Evaluation of ABT-751, a novel anti-mitotic agent able to overcome multi-drug resistance, in melanoma cells

PURPOSE

Drug efflux transporter associated multi-drug resistance (MDR) is a potential limitation in the use of taxane chemotherapies for the treatment of metastatic melanoma. ABT-751 is an orally bioavailable microtubule-binding agent capable of overcoming MDR and proposed as an alternative to taxane-based therapies.

METHODS

This study compares ABT-751 to taxanes in vitro, utilizing seven melanoma cell line models, publicly available gene expression and drug sensitivity databases, a lung cancer cell line model of MDR drug efflux transporter overexpression (DLKP-A), and drug efflux transporter ATPase assays.

RESULTS

Melanoma cell lines exhibit a low but variable protein and RNA expression of drug efflux transporters P-gp, BCRP, and MDR3. Expression of P-gp and MDR3 correlates with sensitivity to taxanes, but not to ABT-751. The anti-proliferative IC50 profile of ABT-751 was higher than the taxanes docetaxel and paclitaxel in the melanoma cell line panel, but fell within clinically achievable parameters. ABT-751 IC50 was not impacted by P-gp-overexpression in DKLP-A cells, which display strong resistance to the P-gp substrate taxanes compared to DLKP parental controls. The addition of ABT-751 to paclitaxel treatment significantly decreased cell proliferation, suggesting some reversal of MDR. ATPase activity assays suggest that ABT-751 is a potential BCRP substrate, with the ability to inhibit P-gp ATPase activity.

CONCLUSION

Our study confirms that ABT-751 is active against melanoma cell lines and models of MDR at physiologically relevant concentrations, it inhibits P-gp ATPase activity, and it may be a BCRP and/or MDR3 substrate. ABT-751 warrants further investigation alone or in tandem with other drug efflux transporter inhibitors for hard-to-treat MDR melanoma.

Gender Difference in sidE eFfects of ImmuNotherapy: a possible clue to optimize cancEr tReatment (G-DEFINER): study protocol of an observational prospective multicenter study

BACKGROUND

Immune checkpoint inhibitors (ICIs) have significantly improved outcomes in various cancers. ICI treatment is associated with the incidence of immune-related adverse events (irAEs) which can affect any organ. Data on irAEs occurrence in relation to sex- differentiation and their association with gender-specific factors are limited.

AIMS

The primary objective of the G-DEFINER study is to compare the irAEs incidence in female and male patients who undergo ICI treatment. Secondary objectives are: to compare the irAEs incidence in pre- and postmenopausal female patients; to compare the irAEs incidence in female and male patients according to different clinical and gender-related factors (lifestyle, psychosocial, and behavioral factors). Exploratory objectives of the study are to compare and contrast hormonal, gene-expression, SNPs, cytokines, and gut microbiota profiles in relation to irAEs incidence in female and male patients.

METHODS AND RESULTS

The patients are recruited from Fondazione IRCCS Istituto Nazionale dei Tumori, Italy, St Vincent's University Hospital, Ireland, Oslo University Hospital, Norway, and Karolinska Insitutet/Karolinska University Hospital, Sweden. The inclusion of patients was delayed due to the Covid pandemic, leading to a total of 250 patients recruited versus a planned number of 400 patients. Clinical and translational data will be analyzed.

INTERPRETATION

The expected outcomes are to improve the management of cancer patients treated with ICIs, leading to more personalized clinical approaches that consider potential toxicity profiles. The real world nature of the trial makes it highly applicable for timely irAEs diagnosis.

Ribociclib plus Endocrine Therapy in Early Breast Cancer

BACKGROUND

Ribociclib has been shown to have a significant overall survival benefit in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether this benefit in advanced breast cancer extends to early breast cancer is unclear.

METHODS

In this international, open-label, randomized, phase 3 trial, we randomly assigned patients with HR-positive, HER2-negative early breast cancer in a 1:1 ratio to receive ribociclib (at a dose of 400 mg per day for 3 weeks, followed by 1 week off, for 3 years) plus a nonsteroidal aromatase inhibitor (NSAI; letrozole at a dose of 2.5 mg per day or anastrozole at a dose of 1 mg per day for ≥5 years) or an NSAI alone. Premenopausal women and men also received goserelin every 28 days. Eligible patients had anatomical stage II or III breast cancer. Here we report the results of a prespecified interim analysis of invasive disease-free survival, the primary end point; other efficacy and safety results are also reported. Invasive disease-free survival was evaluated with the use of the Kaplan-Meier method. The statistical comparison was made with the use of a stratified log-rank test, with a protocol-specified stopping boundary of a one-sided P-value threshold of 0.0128 for superior efficacy.

RESULTS

As of the data-cutoff date for this prespecified interim analysis (January 11, 2023), a total of 426 patients had had invasive disease, recurrence, or death. A significant invasive disease-free survival benefit was seen with ribociclib plus an NSAI as compared with an NSAI alone. At 3 years, invasive disease-free survival was 90.4% with ribociclib plus an NSAI and 87.1% with an NSAI alone (hazard ratio for invasive disease, recurrence, or death, 0.75; 95% confidence interval, 0.62 to 0.91; P = 0.003). Secondary end points - distant disease-free survival and recurrence-free survival - also favored ribociclib plus an NSAI. The 3-year regimen of ribociclib at a 400-mg starting dose plus an NSAI was not associated with any new safety signals.

CONCLUSIONS

Ribociclib plus an NSAI significantly improved invasive disease-free survival among patients with HR-positive, HER2-negative stage II or III early breast cancer. (Funded by Novartis; NATALEE ClinicalTrials.gov number, NCT03701334.).

Prognostic Value of BAP1 Protein Expression in Uveal Melanoma

The prognostic value of the traditional pathologic parameters that form part of the American Joint Committee on Cancer staging system and genetic classifications using monosomy chromosome 3 and structural alterations in chromosome 8 are well established and are part of the diagnostic workup of uveal melanoma (UM). However, it has not been fully clarified whether nuclear protein expression of the tumor suppressor gene BAP1 (nBAP1) by immunohistochemistry alone is as powerful a predictor of overall survival (OS) and/or disease-specific survival (DSS) as chromosome analysis. The protein expression of nBAP1 was evaluated in a retrospective cohort study of 308 consecutive patients treated by primary enucleation between January 1974 and December 2022. We correlated clinical, pathologic, and cytogenetic characteristics to identify the best prognostic indicators for OS and DSS. Loss of nBAP1 was detected in 144/308 (47%) of patients. Loss of nBAP1 expression was significantly associated with poor survival. In patients with disomy chromosome 3, nBAP1 negative is significantly associated with poorer OS but not DSS. We observed that older age (>63 years), presence of metastasis, and nBAP1 negative remained independent prognostic factors in multivariate analysis. nBAP1 protein expression proved to be a more reliable prognostic indicator for OS than the American Joint Committee on Cancer staging, M3 status, or The Cancer Genome Atlas classification in this cohort. This study provides support for accurate prognostication of UM patients in routine histology laboratories by immunohistochemistry for nBAP1 alone.

Pilot study of the implementation of G8 screening tool, Cognitive screening assessment and Chemotherapy Toxicity assessment in older adults with cancer in a Tertiary University Hospital in Ireland

BACKGROUND

Comprehensive geriatric assessment (CGA) is recommended by international guidelines prior to initiation of systemic anti-cancer treatment (SACT). In practice, CGA is limited by time constraints, lack of resources and expert interpretation.

AIMS

The primary objective of this pilot study was to establish the prevalence of frailty (assessed by G8), cognitive impairment (assessed by Mini-Cog), and risk of chemotherapy toxicity (assessed by CARG Chemo-Toxicity Calculator) among patients (pts) ≥65 years commencing SACT. We selected these three screening tools due to the ease of conducting them in a busy outpatient setting. In addition, they have been validated to predict frailty and risk of toxicity from SACT among older adults with cancer.

METHODS

Eligible participants were identified from medical oncology clinics. Assessments were conducted in an outpatient setting by treating physicians. Pt records were reviewed to gather demographic and cancer details. Statistical analyses were conducted using SPSS statistical software.

RESULTS

Sixty-three participants were enrolled. The mean age of participants was 73yrs (range=65-88). Thirty-three (52.4%) were female and 30 (47.6%) were male. The majority (n=38, 60.3%) had metastatic cancer. The mean G8 score was 11.9 (range=6-19). Eighty-three percent had a G8 score ≤14. Mini-Cog was positive in 13 pts (21%). The mean CARG score was 7.5 (range=0-16), and 80% had a risk of at least 50% grade ≥3 toxicity. Of these, 48 (76.2%) received chemotherapy and 15 (23.8%) received non-cytotoxic SACT. In multi-variate analyses, age, cancer type, treatment type, and disease stage did not impact G8, Mini-Cog, or CARG scores.

CONCLUSIONS

Our study has several limitations but suggests that the majority of older adults with cancer would qualify for formal CGA assessment. The risk of high-grade toxicity from SACT is substantial in this cohort. Chronological age was not found to negatively impact pts' frailty, cognition, or risk of toxicity.

Carcinoma of unknown primary (CUP): an update for histopathologists

Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic cancers in which the site of origin is not identifiable. These carcinomas have a poor outcome due to their late presentation with metastatic disease, difficulty in identifying the origin and delay in treatment. The aim of the pathologist is to broadly classify and subtype the cancer and, where possible, to confirm the likely primary site as this information best predicts patient outcome and guides treatment. In this review, we provide histopathologists with diagnostic practice points which contribute to identifying the primary origin in such cases. We present the current clinical evaluation and management from the point of view of the oncologist. We discuss the role of the pathologist in the diagnostic pathway including the control of pre-analytical conditions, assessment of sample adequacy, diagnosis of cancer including diagnostic pitfalls, and evaluation of prognostic and predictive markers. An integrated diagnostic report is ideal in cases of CUP, with results discussed at a forum such as a molecular tumour board and matched with targeted treatment. This highly specialized evolving area ultimately leads to personalized oncology and potentially improved outcomes for patients.

Circulating tumor DNA (ctDNA): can it be used as a pan-cancer early detection test?

Circulating tumor DNA (ctDNA, DNA shed by cancer cells) is emerging as one of the most transformative cancer biomarkers discovered to-date. Although potentially useful at all the phases of cancer detection and patient management, one of its most exciting possibilities is as a relatively noninvasive pan-cancer screening test. Preliminary findings with ctDNA tests such as Galleri or CancerSEEK suggest that they have high specificity (> 99.0%) for malignancy. Their sensitivity varies depending on the type of cancer and stage of disease but it is generally low in patients with stage I disease. A major advantage of ctDNA over existing screening strategies is the potential ability to detect multiple cancer types in a single test. A limitation of most studies published to-date is that they are predominantly case-control investigations that were carried out in patients with a previous diagnosis of malignancy and that used apparently healthy subjects as controls. Consequently, the reported sensitivities, specificities and positive predictive values might be lower if the tests are used for screening in asymptomatic populations, that is, in the population where these tests are likely be employed. To demonstrate clinical utility in an asymptomatic population, these tests must be shown to reduce cancer mortality without causing excessive overdiagnosis in a large randomized prospective randomized trial. Such trials are currently ongoing for Galleri and CancerSEEK.

Neratinib + fulvestrant + trastuzumab for HR-positive, HER2-negative, HER2-mutant metastatic breast cancer: outcomes and biomarker analysis from the SUMMIT trial

BACKGROUND

HER2 mutations are targetable alterations in patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC). In the SUMMIT basket study, patients with HER2-mutant MBC received neratinib monotherapy, neratinib + fulvestrant, or neratinib + fulvestrant + trastuzumab (N + F + T). We report results from 71 patients with HR+, HER2-mutant MBC, including 21 (seven in each arm) from a randomized substudy of fulvestrant versus fulvestrant + trastuzumab (F + T) versus N + F + T.

PATIENTS AND METHODS

Patients with HR+ HER2-negative MBC with activating HER2 mutation(s) and prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy received N + F + T (oral neratinib 240 mg/day with loperamide prophylaxis, intramuscular fulvestrant 500 mg on days 1, 15, and 29 of cycle 1 then q4w, intravenous trastuzumab 8 mg/kg then 6 mg/kg q3w) or F + T or fulvestrant alone. Those whose disease progressed on F + T or fulvestrant could cross-over to N + F + T. Efficacy endpoints included investigator-assessed objective response rate (ORR), clinical benefit rate (RECIST v1.1), duration of response, and progression-free survival (PFS). Plasma and/or formalin-fixed paraffin-embedded tissue samples were collected at baseline; plasma was collected during and at end of treatment. Extracted DNA was analyzed by next-generation sequencing.

RESULTS

ORR for 57 N + F + T-treated patients was 39% [95% confidence interval (CI) 26% to 52%); median PFS was 8.3 months (95% CI 6.0-15.1 months). No responses occurred in fulvestrant- or F + T-treated patients; responses in patients crossing over to N + F + T supported the requirement for neratinib in the triplet. Responses were observed in patients with ductal and lobular histology, 1 or ≥1 HER2 mutations, and co-occurring HER3 mutations. Longitudinal circulating tumor DNA sequencing revealed acquisition of additional HER2 alterations, and mutations in genes including PIK3CA, enabling further precision targeting and possible re-response.

CONCLUSIONS

The benefit of N + F + T for HR+ HER2-mutant MBC after progression on CDK4/6is is clinically meaningful and, based on this study, N + F + T has been included in the National Comprehensive Cancer Network treatment guidelines. SUMMIT has improved our understanding of the translational implications of targeting HER2 mutations with neratinib-based therapy.

Alterations in immune cell phenotype and cytotoxic capacity in HER2+ breast cancer patients receiving HER2-targeted neo-adjuvant therapy

BACKGROUND

The phase II neo-adjuvant clinical trial ICORG10-05 (NCT01485926) compared chemotherapy in combination with trastuzumab, lapatinib or both in patients with HER2+ breast cancer. We studied circulating immune cells looking for alterations in phenotype, genotype and cytotoxic capacity (direct and antibody-dependent cell-mediated cytotoxicity (ADCC)) in the context of treatment response.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from pre- (n = 41) and post- (n = 25) neo-adjuvant treatment blood samples. Direct/trastuzumab-ADCC cytotoxicity of patient-derived PBMCs against K562/SKBR3 cell lines was determined ex vivo. Pembrolizumab was interrogated in 21 pre-treatment PBMC ADCC assays. Thirty-nine pre-treatment and 21 post-treatment PBMC samples were immunophenotyped. Fc receptor genotype, tumour infiltrating lymphocyte (TIL) levels and oestrogen receptor (ER) status were quantified.

RESULTS

Treatment attenuated the cytotoxicity/ADCC of PBMCs. CD3+/CD4+/CD8+ T cells increased following therapy, while CD56+ NK cells/CD14+ monocytes/CD19+ B cells decreased with significant post-treatment immune cell changes confined to patients with residual disease. Pembrolizumab-augmented ex vivo PBMC ADCC activity was associated with residual disease, but not pathological complete response. Pembrolizumab-responsive PBMCs were associated with lower baseline TIL levels and ER+ tumours.

CONCLUSIONS

PBMCs display altered phenotype and function following completion of neo-adjuvant treatment. Anti-PD-1-responsive PBMCs in ex vivo ADCC assays may be a biomarker of treatment response.

Predictive modelling of response to neoadjuvant therapy in HER2+ breast cancer

HER2-positive (HER2+) breast cancer accounts for 20-25% of all breast cancers. Predictive biomarkers of neoadjuvant therapy response are needed to better identify patients with early stage disease who may benefit from tailored treatments in the adjuvant setting. As part of the TCHL phase-II clinical trial (ICORG10-05/NCT01485926) whole exome DNA sequencing was carried out on normal-tumour pairs collected from 22 patients. Here we report predictive modelling of neoadjuvant therapy response using clinicopathological and genomic features of pre-treatment tumour biopsies identified age, estrogen receptor (ER) status and level of immune cell infiltration may together be important for predicting response. Clonal evolution analysis of longitudinally collected tumour samples show subclonal diversity and dynamics are evident with potential therapy resistant subclones detected. The sources of greater pre-treatment immunogenicity associated with a pathological complete response is largely unexplored in HER2+ tumours. However, here we point to the possibility of APOBEC associated mutagenesis, specifically in the ER-neg/HER2+ subtype as a potential mediator of this immunogenic phenotype.

Degradation of MYC by the mutant p53 reactivator drug, COTI-2 in breast cancer cells

TP53 (p53) and MYC are amongst the most frequently altered genes in cancer. Both are thus attractive targets for new anticancer therapies. Historically, however, both genes have proved challenging to target and currently there is no approved therapy against either. The aim of this study was to investigate the effect of the mutant p53 reactivating drug, COTI-2 on MYC. Total MYC, pSer62 MYC and pThr58 MYC were detected using Western blotting. Proteasome-mediated degradation was determined using the proteasome, inhibitor MG-132, while MYC half-life was measured using pulse chase experiments in the presence of cycloheximide. Cell proliferation was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Treatment of 5 mutant p53 breast cancer cell lines with COTI-2 resulted in dose-dependent MYC degradation. Addition of the proteasome inhibitor, MG132, rescued the degradation, suggesting that this proteolytic system was at least partly responsible for the inactivation of MYC. Using cycloheximide in pulse chase experiments, COTI-2 was found to reduce the half-life of MYC in 2 different mutant p53 breast cancer cell lines, i.e., from 34.8 to 18.6 min in MDA-MB-232 cells and from 29.6 to 20.3 min in MDA-MB-468 cells. Co-treatment with COTI-2 and the MYC inhibitor, MYCi975 resulted in synergistic growth inhibition in all 4 mutant p53 cell lines investigated. The dual ability of COTI-2 to reactivate mutant p53 and degrade MYC should enable this compound to have broad application as an anticancer drug.

Rationale and trial design of NATALEE: a Phase III trial of adjuvant ribociclib + endocrine therapy versus endocrine therapy alone in patients with HR+/HER2- early breast cancer

Background

Ribociclib has demonstrated a statistically significant overall survival benefit in pre- and postmenopausal patients with hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) advanced breast cancer. New Adjuvant Trial with Ribociclib [LEE011] (NATALEE) is a trial evaluating the efficacy and safety of adjuvant ribociclib plus endocrine therapy (ET) versus ET alone in patients with HR+/HER2- early nonmetastatic breast cancer (EBC).

Methods/design

NATALEE is a multicenter, randomized, open-label, Phase III trial in patients with HR+/HER2- EBC. Eligible patients include women, regardless of menopausal status, and men aged ⩾18 years. Select patients with stage IIA, stage IIB, or stage III disease (per the anatomic classification in the AJCC Cancer Staging Manual, 8th edition) with an initial diagnosis ⩽18 months prior to randomization are eligible. Patients receiving standard (neo)adjuvant ET are eligible if treatment was initiated ⩽12 months before randomization. Patients undergo 1:1 randomization to ribociclib 400 mg/day (3 weeks on/1 week off) +ET (letrozole 2.5 mg/day or anastrozole 1 mg/day [investigator's discretion] plus goserelin [men or premenopausal women]) or ET alone. Ribociclib treatment duration is 36 months; ET treatment duration is ⩾60 months. The primary end point is invasive disease-free survival.

Discussion

The 36-month treatment duration of ribociclib in NATALEE is extended compared with that in other adjuvant cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor trials and is intended to maximize efficacy due to longer duration of CDK4/6 inhibition. Compared with the 600-mg/day dose used in advanced breast cancer, the reduced ribociclib dose used in NATALEE may improve tolerability while maintaining efficacy. NATALEE includes the broadest population of patients with HR+/HER2- EBC of any Phase III trial currently evaluating adjuvant CDK4/6 inhibitor treatment.

Trial registration

ClinicalTrials.gov identifier: NCT03701334 (https://clinicaltrials.gov/ct2/show/NCT03701334).

Abstract 5787: Modelling the spatial heterogeneity of CD45-positive tumor infiltrating lymphocytes in early-stage, estrogen receptor-positive breast cancer

The frequency of lymphocytes infiltrating tumors is a known prognostic in estrogen receptor (ER) negative cancers. ER+ disease is putatively believed to be immune cold, however, there exists a subset of ER+ tumors with high immune infiltrate and with a significant spatial heterogeneity. The clinic impact of such infiltrate - especially between the Oncotype Dx Recurrence Score risk categories - remains unclear. Moreover, the distribution of tumor and stromal tissues, while noted as significantly heterogenous, is still ill-defined and not yet clinically used prognostically, despite evidence to support its utility. Using a cohort (n=450) of serial sections taken from early-stage, ER+/HER2- breast tumors of the Irish arm of the TAILORx clinical trial, we aimed to investigate the tumor architecture and spatial distribution of tumor immune infiltrate and proliferating tumor cells using digital image analysis. Antibodies against Ki67 (proliferation marker) and CD45 (leukocyte common antigen), and a routine Haematoxylin and Eosin stain were applied to serial sections of 450 full-face tumors via chromogenic immunohistochemistry, as outlined previously [1]. Digital image analysis was performed using open-source software, QuPath [2]. Pixel classifiers were trained and validated against an expert pathologist in order to define observed lymphocytes as tumor or stromal-infiltrating, and to establish a classifier to quantify the tumor-stroma ratio (TSR) and infiltrating tumor area. Distances of CD45-positive cells from tumor were computed, along with autocorrelation statistics [3,4] of CD45 and Ki67 hotspots; firstly in order to quantify spatial heterogeneity, and secondly to examine whether Ki67 as a component gene in the Oncotype Dx assay has a foundation in tumor biology or is being confounded by potentially Ki67-positive lymphocytes. Subdividing by Oncotype Dx risk categories, no significant difference in TSR was observed (p=0.09799), neither for intermediary risk patients receiving hormone therapy alone or in combination with chemotherapy (p=0.3873). While there was an observed trend overall (p=0.092), no significance was found for recurrence between intermediary risk subcategories (HT alone: p=0.393, HT+CT: p=0.288). However, in the cohort as a whole, median TSR was 0.3215 (range 0 - 5.023), with statistically significant differences in recurrence risk observed (cohort high v low by median TSR. HR: 6.356, 95CI: 2.263-17.84, p<0.0001).

Citation Format: Zak Kinsella, Anna Blümel, Mairi Lucas, Andreas Lindner, Claudia A. Gonzalez, Arman Rahman, Joanna Fay, Tony O'Grady, Verena Murphy, John Crown, Cathy Kelly, William Gallagher, Darran O'Connor. Modelling the spatial heterogeneity of CD45-positive tumor infiltrating lymphocytes in early-stage, estrogen receptor-positive breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5787.

Abstract 4041: The EML4-ALK fusion protein mediates reduced sensitivity to the combination of neratinib and dasatinib

Introduction: The anaplastic lymphoma kinase (ALK) gene encodes a receptor tyrosine kinase involved in cellular proliferation, differentiation, and cell death. ALK becomes oncogenic when it forms a fusion gene. The EML4-ALK fusion gene has been identified mainly in non-small cell lung cancer (NSCLC). It is unknown whether neratinib, an irreversible pan-HER tyrosine kinase inhibitor (TKI) targeting EGFR, HER2 and HER4, is effective in cancers harboring EML4-ALK gene fusion. The objective of this study was to assess in vitro efficacy of neratinib in combination with dasatinib (Src/Abl TKI) or crizotinib (ALK TKI) in EML4-ALK+ NSCLC.

Methods: The antiproliferative effects of neratinib, dasatinib and crizotinib were assessed in the CRISPR/Cas9-modified EML4-ALK fusion-A549 (EML4-ALK+) and parental A459 (A549-Par) NSCLC cell lines by 5-day acid phosphatase assay. IC50 values were calculated using CalcuSyn software. To assess the synergy between neratinib and dasatinib, and neratinib and crizotinib, matrix assays were performed and analyzed using Combenefit software. To further assess the efficacy of the TKIs, changes in signaling pathways were assessed by Western blotting, and apoptosis induction and cell migration were measured with the Incucyte® S3 imaging system.

Results: Neratinib, crizotinib, and dasatinib displayed nanomolar IC50 values in both cell lines. As expected, EML4-ALK+ cells were more sensitive to crizotinib than A549-Par cells (IC50 = 595 nM vs 1 µM, p ≤ 0.05). EML4-ALK expression led to numerical increases in neratinib IC50 value (326.37 ± 44.34 nM in EML4-ALK+ vs 247 ± 32.65 nM in A549-Par) and dasatinib IC50 value (39.95 ± 5.67 nM in EML4-ALK+ vs 27.75 ± 18.53 nM in A549-Par) but these changes were not statistically significant. Matrix assays showed that neratinib-crizotinib (NC) was more effective than crizotinib alone in both cell lines, with more potent sensitivity in EML4-ALK+ cells. The neratinib-dasatinib (ND) combination was synergistic in the A549-Par cell line but only additive in the EML4-ALK+ cell line, suggesting a reduced sensitivity to the ND combination. EML4-ALK+ cells had sustained pERK1/2 levels after treatment with all TKIs, except NC, compared to A549-Par cells. Neratinib alone was significantly less effective at inhibiting pAkt (99.2 ± 5.3 % in EML4-ALK+ vs 64.9 ± 19.0 %, p ≤ 0.05) and pERK1/2 (91.3 ± 4.6 % in EML4-ALK+ vs 54.9 ± 15.9 %, p ≤ 0.01) in EML4-ALK+ cells than in A549-Par cells at 24h. In A549-Par cells, ND caused the highest apoptotic induction, followed by NC. Apoptosis levels induced by ND in EML4-ALK+ cells were 4-fold lower at 72hr than in A549-Par cells (p ≤ 0.0001). Dasatinib and ND were more effective than crizotinib or NC at preventing cell migration in both cell lines.

Conclusion: EML4-ALK potentially decreases sensitivity to the neratinib-dasatinib combination. This warrants further investigation in other EML4-ALK+ models.

Citation Format: Myra E. Castel, Neil T. Conlon, Lisa D. Eli, Alvin Wong, John Crown, Denis M. Collins. The EML4-ALK fusion protein mediates reduced sensitivity to the combination of neratinib and dasatinib. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4041.

Abstract 3962: Development of selection-free HER4-mutated CRISPR/Cas9 knock-ins in cutaneous melanoma cell lines

Background: Cutaneous melanoma showed the highest HER4 genomic alteration frequency (17.34%) across 33 different cancer types (cBioPortal). HER4 is a tyrosine kinase receptor belonging to the human epidermal growth factor receptor (HER/ErbB) family. The role of HER4 in cancer has not been fully studied, potentially due to its complex biology (four isoforms, different stability/tissue-specific expression patterns, and oncogenic/tumor suppressor roles). Using computational analysis, we identified two potentially oncogenic HER4 mutations in melanoma (HER4 R106C and R711C). We then developed CRISPR/Cas9-modified selection-free melanoma cell lines for interrogating the role of these mutations as biomarkers of response to the oral, irreversible pan-HER (EGFR, HER2, HER4) tyrosine kinase inhibitor (TKI) neratinib (NER).

Methods: Two melanoma cell lines (WM115, SKMEL24) were genome-edited by using a selection-free CRISPR/Cas9 approach. Single guide RNAs (sgRNAs) were designed by using the CRISPRon (v1.0) web tool, and Homology Directed Repair (HDR) single-stranded OligoDeoxyriboNucleotides (ssODNs), containing the HER4 mutations, were designed with the SnapGene Software (v6.1.1). The RNP complex (Cas9 and sgRNAs) and the HDR_ssODNs, for each HER4 mutation, were delivered into the melanoma cells through electroporation. Upon validation of the CRISPR/Cas9-efficiency via PCR and Sanger Sequencing, the CRISPR/Cas9-modified cells were single-cell sorted via FACS, by using two singlets gating (FSC-A/FSC-H and SSC-A/SSC-H) and a live/dead (propidium iodide) gating, to perform single-cell cloning. Colonies were then amplified and screened via PCR and Sanger sequencing to isolate pure selection-free HER4 CRISPR/Cas9 knock-ins clones of melanoma cells.

Results: The WM115 and SKMEL24 melanoma cell lines were found to be wild-type for the HER4 receptor in the Depmap Portal (mutation 22Q2, 2022 data release 2). R106C and R711C CRISPR/Cas9 knock-ins were created in the melanoma cell lines three days after the electroporation of the CRISPR/Cas9 complex. The efficiency of the HER4 R106C CRISPR/Cas9 knock-in was 22% and 7% in the SKMEL24 and WM115 melanoma cells, respectively, with a respective total indel percentage of 76% (SKMEL24) and 55% (WM115). The HER4 R711C CRISPR/Cas9 knock-in efficiency was 15% in the SKMEL24 (with 26% total indels) and 1% in the WM115 (with 33% total indels). Single-cell colonies of the HER4 CRISPR/Cas9-mediated knock-ins (HER4 R106C and R711C), were formed at four days (SKMEL24) and at one week (WM115) after single-cell sorting.

Conclusions: CRISPR/Cas9 technology can be utilised to introduce single-point mutations in HER4 to melanoma cell lines. In vitro functional characterisation of the isolated HER4 CRISPR/Cas9-edited melanoma cell lines will be performed in order to understand the activating potential of HER4 R106C and R711C and their sensitivity to NER.

Citation Format: Marta Valenti, Yonglun Luo, Neil T. Conlon, Lisa D. Eli, Alvin Wong, John Crown, Denis M. Collins. Development of selection-free HER4-mutated CRISPR/Cas9 knock-ins in cutaneous melanoma cell lines. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3962.

Abstract P3-07-16: Pre-clinical study of amcenestrant and HER2-targeted therapies in HER2+/ER+ breast cancer cell line models

Background: Up to 70% of HER2 over-expressing (HER2+) breast cancers also express estrogen receptor (ER). Dual targeting of HER2 and ER has shown pre-clinical and clinical benefit in HER2+/ER+ breast cancer. Rationale for these combinations is based on circumvention of resistance mediated by crosstalk between HER2 and ER signalling pathways. Fulvestrant is the only selective estrogen receptor degrader (SERD) approved by the FDA for the treatment of ER+ breast cancer. Development of alternative orally available SERDs with improved bioavailability, such as amcenestrant, is underway. The HER2-targeted tyrosine kinase inhibitors (TKIs) lapatinib, neratinib and tucatinib and the antibody drug conjugate T-DM1 are approved for the treatment of HER2+ breast cancer. This pre-clinical study aims to investigate the potential of combining the oral SERD amcenestrant with HER2-targeted therapies for the treatment of HER2+/ER+ breast cancer through identification of synergistic combinations.

Methods: ER and HER2 expression levels were assessed in the HER2+/ER+ BT-474 and MDA-MB-361 cell lines by western blot. 5-day acid phosphatase-based assays were used to assess cell viability following treatment with neratinib, lapatinib, tucatinib, and T-DM1; alone and in combination with amcenestrant. All TKIs were commercially sourced, T-DM1 was obtained from Saint Vincent’s University Hospital. Amcenestrant was supplied by Sanofi. IC50 values were determined using Calcusyn, while matrix combination assays of the HER2-targeted therapies combined with amcenestrant were analysed using Combenefit software employing the Loewe model (LM) to determine synergy (Score > 0) or antagonism (Score < 0). All data are the result of a minimum of three independent experiments.

Results: HER2 and ER expression was confirmed in the MDA-MB-361 and BT-474 cell lines. MDA-MB-361 cells express higher levels of ER and lower levels of HER2 and phosphorylated HER2 than BT474 cells. MDA-MB-361 exhibited a higher sensitivity to 1 µM amcenestrant alone (% cell viability = 53.3 ± 2.3 %) than the BT-474 (% viability = 85.3 ± 5%). A comparison of IC50 values for each TKI alone or in combination with 1 µM amcenestrant showed amcenestrant significantly lowered the IC50 values for neratinib and tucatinib in BT-474, and all three TKIs in MDA-MB-361 (Table 1). In matrix combination assays, all TKIs exhibited synergistic combinations, with the combination of neratinib and amcenestrant demonstrating the highest synergy values in MDA-MB-361 (LM max value = 25 ± 7) and in BT-474 (LM max value = 19 ± 7). The combination of amcenestrant and T-DM1 displayed additivity (LM value = 0) rather than synergy in the BT-474 cell line, likely due to the high potency of T-DM1 as a single agent.

Conclusions: The combination of amcenestrant and HER2-targeting therapies such as neratinib shows potential as a dual-target therapeutic strategy for the treatment of HER2+/ER+ breast cancer and warrants further investigation.

Table 1. IC50 values for TKIs alone and with the addition of 1 µM amcenestrant. Significance of chance in IC50 point calculated by Student’s T test, ns = p > 0.05, * = p < 0.05, ** = p < 0.01, SD = standard deviation

Citation Format: Amira F. Mahdi, Niall Ashfield, Neil T. Conlon, John Crown, Denis M. Collins. Pre-clinical study of amcenestrant and HER2-targeted therapies in HER2+/ER+ breast cancer cell line models [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-07-16.

Abstract P1-11-10: Reversible versus irreversible tyrosine kinase inhibitors (TKIs) combined with antibody-drug conjugates (ADCs) in HER2-positive (HER2+) breast cancer (BC) cell lines

Background: Targeting the human epidermal growth factor receptor (HER) family of tyrosine kinase receptors with small molecule TKIs lapatinib, neratinib and tucatinib, monoclonal antibodies like trastuzumab and more recently with ADCs like T-DM1 and T-DXd has resulted in improved survival rates for patients with HER2+ BC. TKIs are primarily utilised in trastuzumab-refractory disease. Neratinib, and the pan-HER TKI afatinib, bind irreversibly to all members of the HER family, while lapatinib binds reversibly to HER2 and EGFR, and tucatinib binds reversibly to HER2 alone. Previous work in our lab has shown that TKIs like lapatinib are capable of modulating tumour surface HER2 levels and increasing trastuzumab load on tumours. Thus, there is a rationale for the use of TKI/ADC combinations in HER2+ BC. Using innately trastuzumab-resistant HER2+ BC cell lines, this in vitro study aims to assess the anti-proliferative potential of HER2-targeting ADCs T-DM1 or T-DXd in combination with the TKIs afatinib, lapatinib, neratinib or tucatinib.

Methods: HCC1569 and HCC1954 cells (HER2+, estrogen receptor (ER)-negative; innately trastuzumab-resistant) were grown in RPMI1640/10% FBS at 37°C and 5% CO2. The anti-proliferative effects of afatinib, lapatinib, neratinib and tucatinib; of T-DM1 and T-DXd; and of each TKI/ADC combination thereof were assessed in these cells via 5-day acid phosphatase. ADCs were obtained from Saint Vincent’s University Hospital, Dublin, and TKIs were purchased from commercial sources. Calcusyn software was used to generate IC50 values and combination index (CI) values at ED50. CI values > 1 represent an antagonistic combination, CI values = 1 are additive, and CI values < 1 are synergistic. All assays were carried out in triplicate.

Results: The HCC1569 cell line was more sensitive to all four TKIs (IC50 values were 12.8 ± 0.3, 453.8 ± 47.1 nM, 4.7 ± 1.4 and 381.5 ± 37.3 nM for afatinib, lapatinib, neratinib and tucatinib respectively) compared to the HCC1954 cell line (IC50 22.3 ± 2.8, 652.4 ± 36.0, 57.0 ± 6.3 and 2365.1 ± 185.3 nM for afatinib, lapatinib, neratinib and tucatinib respectively). Despite their innate trastuzumab resistance, both cell lines displayed high sensitivity to T-DM1 (IC50 25.2 ± 8.7 ng/mL for HCC1569 and IC50 30.4 ± 3.2 ng/mL for HCC1954) and to T-DXd (IC50 16.0 ± 3.2 ng/mL for HCC1569 and IC50 36.8 ± 8.7 ng/mL for HCC1954). In both cell lines, co-treatment with ADCs and the irreversible TKIs afatinib and neratinib resulted in additive or synergistic responses, while the combination of the ADCs with the reversible TKIs lapatinib and tucatinib resulted in mild to moderate antagonism (Table 1).

Conclusions: In this pre-clinical study, T-DM1 and T-DXd consistently exhibited antagonistic interactions with reversible HER2-targeting TKIs, and synergy/additivity in combination with the irreversible TKIs tested. Future work will explore the underlying mechanisms of this observed synergy and antagonism, including impacts of TKIs on HER2 expression and real-time ADC internalisation rates.

Table 1. CI values +/- Std Dev for each TKI/ADC treatment combination in HCC1569 and HCC1954 cells

Citation Format: Niall Ashfield, Amira F. Mahdi, Neil T. Conlon, John Crown, Denis M. Collins. Reversible versus irreversible tyrosine kinase inhibitors (TKIs) combined with antibody-drug conjugates (ADCs) in HER2-positive (HER2+) breast cancer (BC) cell lines [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-11-10.

Abstract P5-02-10: In-silico approaches that detect immune contexture to trastuzumab response in neo-adjuvant studies

Introduction: Computational approaches have aided in estimating cellular composition of the tumour microenvironment. The evaluation of immune composition in tumours before treatment may predict pathologic complete response (pCR). The aim of the study was to perform a meta-analysis of HER2-positive breast cancer subjects who received neoadjuvant trastuzumab to detect associations between immune cells measured by CIBERSORT and ESTIMATE and pCR. Methods: PubMed was used to identify transcriptomic data of HER2-positive breast cancer patients who received neoadjuvant trastuzumab. Baseline data from eight neoadjuvant studies (N=338) was downloaded from GEO. Data from each study was background corrected and quantile normalised using ‘limma’ or ‘oligo’ packages in R. Immune profiles per sample was generated using computational softwares CIBERSORT and ESTIMATE, and were then linked to pCR status. Correlations between immune contexture and pCR for each study were interpreted using statistical testing. Meta-analysis by a logistic regression model was conducted on studies which passed assumptions to identify CIBERSORT immune subsets robust to pCR. Results: CIBERSORT results showed that three studies had reduced T follicular helper cells (Tfh) (Brodsky p=0.38, CHER-LOB p=0.17, TransNOAH p=0.25) and two studies had reduced plasma cells (CHER-LOB p=0.15, Brodsky p=0.38) in the pCR group, but was not significant after multiple correction. ESTIMATE analysis showed that data from two studies had elevated immune infiltration in pCR (Brodsky p=0.19, CHER-LOB p=0.10) but was not significant. A meta-analysis of pooled data from four studies (TRIO-US B07, 03-311, TransNOAH, CHER-LOB) showed that low Tfh (p=0.053, OR=0.04, CI [0.0012-0.99]) and high memory B-cells (p=0.008, OR=2126.9, CI [8.12-7.65 × 10+5]) prior to trastuzumab treatment may be associated with a better chance of achieving pCR. Conclusion: Results from our meta-analysis proposed that memory B- and T follicular helper subsets may predict a role in achieving pCR. Incorporating studies with larger sample cohorts such as the CALGB-40601 (N=265) study can achieve statistical power of this analysis.

Citation Format: Dalal AlSultan, Alex J. Eustace, Stephen F. Madden, John Crown. In-silico approaches that detect immune contexture to trastuzumab response in neo-adjuvant studies [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-10.

Abstract P5-02-11: Immune cell profile of tumors from patients with metastatic (met) HER2+ breast cancer (BC) with < 30 months overall survival (OS)

Background: The “Thousand Patient HER-2 database” project at Saint Vincent’s University Hospital (SVUH) Dublin has been used to identify HER2+ BC patients with durable complete response (never relapsed) to trastuzumab-based therapy. ~10% of met HER2+ BC patients achieve a durable complete response to trastuzumab, meaning the majority of patients progress on treatment. Higher stromal tumour immune infiltrate has been associated with longer OS in met HER2+ BC. There is limited tumor immune profile and PD-1 expression data available for patients with met HER2+ BC with short OS. Using the SVUH database, we have identified a preliminary cohort of 21 met HER2+ BC patients that received trastuzumab and had an OS < 30 months. This study examines the levels of pan T cell marker CD3, cytotoxic T cell marker CD8, Natural Killer (NK) cell marker CD56 and immune checkpoint PD-1 by immunohistochemistry (IHC) in this preliminary cohort. Methods: Formalin-fixed, paraffin-embedded (FFPE) biopsy specimens (n=21 primary, n=7 matched metastatic biopsies) and associated clinico-pathological data were curated. Tumor biopsies were processed for IHC staining of CD8 (Agilent IR62361-2), CD3 (Agilent IR50361-2), CD56 (Agilent IR62861-2) and PD-1 (Roche 07099029001). PD-1 staining was available for 20/21 samples. Staining was performed using the DAKO Link 48 Autostainer as per the manufacturer’s instructions using positive (tonsil tissue) and negative controls (isotype controls). Slides were processed using the Aperio AT2 Digital Slide Scanner (Leica Biosystems), reviewed using Aperio ImageScope 12.4 software (Leica Biosystems) and analyzed in QuPath (University of Edinburgh). Images were annotated to outline tumor areas and an algorithm was trained to identify cells and classify them as either tumor or stromal. Data was expressed as number of positively stained cells/mm2 breast tumor or stromal tissue. Survival studies utilized the Kaplan Meier method. The paired Student’s T test was utilized for primary vs metastatic site comparisons. Results: Designating samples with > 1 stained cell/mm2 breast tumor as positive (pos) and zero stained cells as negative (neg), 19/21 (90.5%) primary samples were pos for CD3, 15/21 (71.4%) for CD56, 14/21 (66.6%) for CD8, and 10/20 (50%) for PD-1. Within the stromal compartment, 20/21 (95.2%) primary samples were pos for CD8, 18/21 (85.7%) for CD56, 16/21 (76.2%) for CD3 and 8/20 (40%) for PD-1. PD-1 expression in the primary tumor (median OS PD-1pos 7.85 mo vs PD-1neg 5.39 mo, hazard ratio (HR) 0.642 (95% CI 0.256-1.613), p=0.346) or the stroma (median OS PD-1pos 8.84 mo vs PD-1neg 5.39 mo, HR 0.495 (95% CI 0.197-1.244), p=0.135) was not significantly associated with OS. When comparing matched primary and metastatic samples (n=7), increased stromal levels of CD3 (4/7), CD8 (4/7), CD56 (5/7) and PD-1 (4/7) were observed. Increased levels of CD3 and CD8 were observed for 2/7 samples, and increased levels of CD56 and PD-1 for 4/7 samples. With the exception of tumor CD8 levels which decreased, mean values for tumor and stromal CD3, CD56, PD-1 and stromal CD8 levels were higher in metastatic sites but all differences were not found to be significant (p>0.05). Conclusions: Our results suggest that met HER2+ BC patients with < 30 months OS have significant T cell and NK cell presence in the tumor and stromal compartments in both primary and metastatic sites. Further expansion of this limited dataset is planned to gain greater insight in to the immune cell profiles and PD-1 status of met HER2+ BC patients with short OS.

Citation Format: Denis M. Collins, Janet McCormack, Laura P. Ivers, Jose Javier Berenguer Pina, Jo Ballot, Cecily Quinn, Darko Skrobo, Alex J. Eustace, Naomi Walsh, Aurelie Fabre, John Crown. Immune cell profile of tumors from patients with metastatic (met) HER2+ breast cancer (BC) with < 30 months overall survival (OS). [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-11.

Abstract P6-12-09: Retinoic acid receptor (RAR) signalling plays a role in neratinib (NER) resistance in HER2+ breast cancer (BC) cell lines

Introduction: NER is a pan-HER tyrosine kinase inhibitor (TKI) approved for the treatment of HER2+ BC in the adjuvant setting following trastuzumab and in combination with capecitabine for advanced disease. Resistance to small molecule TKIs like NER can develop in the clinic. Pre-clinical studies have highlighted that retinoic acid can inhibit BC growth and modulate HER2 signalling pathways. The RAR family of nuclear transcription factors consists of RARα, RARβ and RARγ. The synthetic retinoic acid fenretinide (FN) acts as a pan-RAR agonist, while AGN194310 (AG) acts as a pan-RAR antagonist. In order to investigate the anti-proliferative potential of co-targeting RAR and HER2 pathways in sensitive and resistant BC cell line models, we examined the effect of FN and AG in combination with NER in two HER2+, estrogen receptor-negative, trastuzumab-resistant cell lines HCC1569 and HCC1954, and their NER-resistant (NR) sub-lines HCC1569-NR and HCC1954-NR. Methods: HCC1569 and HCC1954 cell lines were cultured in RPMI/10% FCS at 370C/5% CO2. NR cell lines were generated by continuous exposure to 150nM NER for 6 months. 10 mM stock solutions of FN (H7779-Sigma), AG (SML2665-Sigma) and NER (supplied by Puma Biotechnology, Inc) were made in DMSO. Proliferation was measured as percentage growth versus DMSO control using an acid phosphatase based assay after 5 days drug exposure. The half-maximal inhibitory concentration (IC50) was calculated for each drug using CalcuSyn. The combination assays were performed using fixed ratios. The combination index (CI) values were calculated at the effective dose that inhibits 50% growth (ED50) using CalcuSyn. Values < 1 represent a synergistic effect, a value of 1 is additive and values > 1 represent an antagonistic effect. All data presented as the mean of biological triplicate experiments ± standard deviation. Results: This research found that the NR cell lines were >10-fold resistant to NER (HCC1569-NR IC50 0.44 ± 0.1 μM, HCC1954-NR IC50 0.198 ± 0.019 μM) compared to the parental HCC1569 (IC50 0.018 ± 0.015 μM) and HCC1954 (IC50 0.017 ± 0.001 μM) cell lines. Pan-RAR agonism by FN had a potent anti-proliferative effect in the HCC1569 (FN IC50 0.22 ± 0.02 μM) and the HCC1569-NR cell lines (FN IC50 0.28 ± 0.13 μM), with the HCC1954 and HCC1954-NR cell lines proving less sensitive (IC50 6.47 ± 1.3 μM and 1.9 ± 0.2 μM, respectively). When combined with NER, FN produced a strong antagonistic effect in the HCC1569 cell line (CI value: 15.63 ± 9.5) and a strong synergistic effect in the HCC1954 cell line (CI value: 0.42 ± 0.06). For the NR cell line models, the NER/FN combination proved synergistic (HCC1569-NR, CI value: 0.84 ± 0.46) or additive (HCC1954-NR, CI value: 0.97 ± 0.15). Next, we wanted to assess the impact of antagonising rather than activating RAR activity in our cell line models. All four cell lines were less sensitive to antagonist AG (IC50 >8μM for all cell lines) compared to FN. The addition of AG to NER resulted in responses diametrically opposed to the FN/NER combination. The AG/NER combination produced a strong synergistic effect in the HCC1569 cell line (CI value: 0.52 ± 0.17), an antagonistic effect in the HCC1954 cell line (CI value: 2.1 ± 0.4) and an antagonistic effect in both NR cell lines (HCC1954-NR, CI value: 2.69 ± 0.6 and HCC1569-NR, CI value: 1.58 ± 0.12). Conclusions: This pre-clinical study suggests involvement of the RAR signalling pathway in response to NER and the development of NR. Results also suggest pan-RAR agonism, rather than pan-RAR antagonism, as a potential therapeutic strategy to overcome NR. Further investigation is warranted to determine how targeting the RAR signalling pathway may assist in the treatment of HER2+ BC.

Citation Format: Debbie O’Reilly, Lisa D. Eli, Alvin Wong, John Crown, Denis M. Collins. Retinoic acid receptor (RAR) signalling plays a role in neratinib (NER) resistance in HER2+ breast cancer (BC) cell lines [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-12-09.

Abstract P1-11-09: Five year follow up of a randomized phase II comparison of neo-adjuvant docetaxel, carboplatin, trastuzumab with or without lapatinib in HER-2 positive breast cancer

Background: The addition of trastuzumab (H) to pre-operative chemotherapy in HER2+ breast cancer (H+BC) increases the rate of pathological complete response (pCR). TCH is a widely used adjuvant regimen in early stage H+BC. Lapatinib (L) is a small molecule HER2 antagonist that produces responses following H failure, and has been reported to augment H activity in combination in vitro. We compared neo-adjuvant docetaxel, carboplatin (TC) + H v TCL v TCHL in pts with H+BC.

Methods: Pts with stages Ic–III H+BC were randomized to receive neo-adjuvant TCH, TCL or TCHL (ICORG/CTRIAL-IE 10-05, NCT01485926 www.clinicaltrials.gov). Pts subsequently underwent surgery and received H post-operatively for 1 year from the first dose of H. The primary endpoint of the trial was pCR. Secondary objectives were overall survival (OS) and relapse-free survival (RFS) and molecular and pharmacological markers of response. This study was supported by GSK, Novartis, The Cancer Clinical Research Trust and The Caroline Foundation.

Results: When the NCIC CTG MA.31 trial reported inferior outcomes for L compared to H, we discontinued the TCL arm. This abstract reports data on the 76 pts recruited to the TCH and TCHL arms only, who included stage II (69.7%; n=53) or stage III disease (21.1%; n=16, with stage unknown for 9.2% (n=7). The final analysis set numbered 75 pts. Clinicopathological characteristics were well balanced between arms. The pCR rate of the two arms TCHL and TCH were virtually identical at 51.6% and 52.8% respectively (Fisher’s test p-value: 1.000). TCHL pts had significantly superior 5 year relapse-free survival (relative risk (RR) 0.171, 95% CI 0.041 – 0.713; log-rank test p-value = 0.009). OS was comparable between the TCH and TCHL groups (RR 0.205, 95% CI 0.025 – 1.675); log-rank test p-value = 0.2). Median RFS and OS were not reached. The most frequent serious adverse event was diarrhoea which occurred in 21.3% (n=16/75) pts (Grade 3 diarrhoea 13/16). One pt (TCH arm) who did not have protocol-mandated prophylactic G-CSF had a Grade 5 toxicity. One TCHL pt had a self-limiting diverticular perforation. There was a significantly higher frequency of severe diarrhoea in pts who received the TCHL regimen (Grade 3+, 32.4% vs 10.5%, p=0.038). The use of prophylactic loperamide reduced the frequency of diarrhoea in both the TCHL arm (86.2% vs 44.4%, p=0.004) and in the TCH arm (58.8% vs 24%, p=0.009). A post lock audit with minimum 9-year follow-up showed relapse rates of 15% TCHL vs 33% TCH.

Conclusions: The study did not meet its primary pCR endpoint possibly due to a high TCH pCR rate, and small numbers. TCHL produced a statistically significant improvement in RFS compared to TCH. TCHL produced a higher rate of gastro-intestinal toxicity, but the use of loperamide significantly reduced the frequency of diarrhoea. These data suggest that anti-HER2 TKIs merit further investigation in the neo-adjuvant treatment of early stage H+BC.

Table 1. pCR rates, 5 year RFS and OS results for ICORG/CTRIAL-IE 10-05 (NCT01485926) study pts. * significant, p<0.05.

Citation Format: John Crown, Denis M. Collins, Alex J. Eustace, Maccon Keane, Linda Coate, John Kennedy, Seamus O’Reilly, Catherine Kelly, Miriam O’Connor, Michael J. Martin, Conleth Murphy, Karen Duffy, Janice Walshe, Thamir Mahgoub, Giuseppe Gullo, Brian Moulton, Alberto Alvarez-Iglesias, Imelda Parker, Bryan Hennessy. Five year follow up of a randomized phase II comparison of neo-adjuvant docetaxel, carboplatin, trastuzumab with or without lapatinib in HER-2 positive breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-11-09.

Vitamin D Supplementation: Does It Have a Preventative or Therapeutic Role in Cancer?

Although best known for its role in skeletal health, a deficiency of vitamin D has also been implicated in cancer formation and progression. The aim of this article was to review the relationship between circulating levels of vitamin D {25(OH)D} and both the risk of developing cancer and outcome from cancer. We also reviewed the effects of vitamin D supplementation on cancer risk and outcome. Our primary focus was on patients with colorectal and breast cancer, as these are two of the cancer types best investigated with respect to the effects of vitamin D on cancer risk and outcome. Based on our review of the literature, we conclude that although low circulating levels of 25(OH)D appears to be associated with an increased risk of developing breast and colorectal cancer, the available evidence suggests that supplementation of healthy subjects with vitamin D does not decrease cancer risk. Supplementation may however, improve outcomes in patients who develop cancer, but this finding remains to be confirmed in an appropriately powered randomized clinical trial.

Circulating Tumor DNA as a Biomarker for Monitoring Patients with Solid Cancers: Comparison with Standard Protein Biomarkers

BACKGROUND

Protein-based biomarkers are widely used in monitoring patients with diagnosed cancer. These biomarkers however, lack specificity for cancer and have poor sensitivity in detecting early recurrences and monitoring therapy effectiveness. Emerging data suggest that the use of circulating tumor DNA (ctDNA) has several advantages over standard biomarkers.

CONTENT

Following curative-intent surgery for cancer, the presence of ctDNA is highly predictive of early disease recurrence, while in metastatic cancer an early decline in ctDNA following the initiation of treatment is predictive of good outcome. Compared with protein biomarkers, ctDNA provides greater cancer specificity and sensitivity for detecting early recurrent/metastatic disease. Thus, in patients with surgically resected colorectal cancer, multiple studies have shown that ctDNA is superior to carcinoembryonic antigen (CEA) in detecting residual disease and early recurrence. Similarly, in breast cancer, ctDNA was shown to be more accurate than carbohydrate antigen 15-3 (CA 15-3) in detecting early recurrences. Other advantages of ctDNA over protein biomarkers in monitoring cancer patients include a shorter half-life in plasma and an ability to predict likely response to specific therapies and identify mechanisms of therapy resistance. However, in contrast to proteins, ctDNA biomarkers are more expensive to measure, less widely available, and have longer turnaround times for reporting. Furthermore, ctDNA assays are less well standardized.

SUMMARY

Because of their advantages, it is likely that ctDNA measurements will enter clinical use in the future, where they will complement existing biomarkers and imaging in managing patients with cancer. Hopefully, these combined approaches will lead to a better outcome for patients.

Inhibition of CDK8/19 Mediator kinase potentiates HER2-targeting drugs and bypasses resistance to these agents in vitro and in vivo

Breast cancers (BrCas) that overexpress oncogenic tyrosine kinase receptor HER2 are treated with HER2-targeting antibodies (such as trastuzumab) or small-molecule kinase inhibitors (such as lapatinib). However, most patients with metastatic HER2+ BrCa have intrinsic resistance and nearly all eventually become resistant to HER2-targeting therapy. Resistance to HER2-targeting drugs frequently involves transcriptional reprogramming associated with constitutive activation of different signaling pathways. We have investigated the role of CDK8/19 Mediator kinase, a regulator of transcriptional reprogramming, in the response of HER2+ BrCa to HER2-targeting drugs. CDK8 was in the top 1% of all genes ranked by correlation with shorter relapse-free survival among treated HER2+ BrCa patients. Selective CDK8/19 inhibitors (senexin B and SNX631) showed synergistic interactions with lapatinib and trastuzumab in a panel of HER2+ BrCa cell lines, overcoming and preventing resistance to HER2-targeting drugs. The synergistic effects were mediated in part through the PI3K/AKT/mTOR pathway and reduced by PI3K inhibition. Combination of HER2- and CDK8/19-targeting agents inhibited STAT1 and STAT3 phosphorylation at S727 and up-regulated tumor suppressor BTG2. The growth of xenograft tumors formed by lapatinib-sensitive or -resistant HER2+ breast cancer cells was partially inhibited by SNX631 alone and strongly suppressed by the combination of SNX631 and lapatinib, overcoming lapatinib resistance. These effects were associated with decreased tumor cell proliferation and altered recruitment of stromal components to the xenograft tumors. These results suggest potential clinical benefit of combining HER2- and CDK8/19-targeting drugs in the treatment of metastatic HER2+ BrCa.

Statins inhibit proliferation and induce apoptosis in triple-negative breast cancer cells

TP53 (p53) is mutated in 80–90% of cases of triple-negative breast cancer (TNBC). Statins, which are widely used to treat elevated cholesterol, have recently been shown to degrade mutant p53 protein and exhibit anti-cancer activity. The aim of this work was to evaluate the potential of statins in the treatment of TNBC. The anti-proliferative effects of 2 widely used statins were investigated on a panel of 15 cell lines representing the different molecular subtypes of breast cancer. Significantly lower IC50 values were found in triple-negative (TN) than in non-TN cell lines (atorvastatin, p < 0.01; simvastatin p < 0.05) indicating greater sensitivity. Furthermore, cell lines containing mutant p53 were more responsive to both statins than cell lines expressing wild-type p53, suggesting that the mutational status of p53 is a potential predictive biomarker for statin response. In addition to inhibiting proliferation, simvastatin was also found to promote cell cycle arrest and induce apoptosis. Using an apoptosis array capable of detecting 43 apoptosis-associated proteins, a novel protein shown to be upregulated by simvastatin was the IGF-signalling modulator, IGBP4, a finding we confirmed by Western blotting. Finally, we found synergistic growth inhibition between simvastatin and the IGF-1R inhibitor, OSI-906 as well as between simvastatin and doxorubicin or docetaxel. Our work suggests repurposing of statins for clinical trials in patients with TNBC. Based on our findings, we suggest that these trials investigate statins in combination with either doxorubicin or docetaxel and include p53 mutational status as a potential predictive biomarker.

Abstract 2717: Exploring immune contexture using computational approaches in HER2-positive breast cancer

Introduction: Tumor infiltrating lymphocytes (TILs) have a significant effect on tumor progression and survival outcome, and serve as a potential biomarker for pathologic complete response (pCR) in neoadjuvant HER2-positive breast cancer therapy. The assessment of TIL abundance and organization prior to treatment initiation has been associated with improved survival and response in breast cancer. This study aims to assess immune contexture using in silico approaches in a meta-analysis of neoadjuvant trastuzumab therapy.

Methods: A literature search was conducted on baseline and on-treatment mRNA data from neoadjuvant studies that enrolled patients who received HER2-targeted therapies. A total of 322 baseline samples from eight neoadjuvant datasets were retrieved from Gene Expression Omnibus (GEO) repository (0. Of these studies, two had available on-treatment samples (03-311; n=50, TRIO-US B07 (n=64). The raw data were pre-processed by normalization and background correction using ‘limma’ and ‘oligo’ packages in R. mRNA profiles of baseline and paired samples were analyzed using in silico approaches CIBERSORT and ESTIMATE. Response information was assigned to each sample to observe the proportion of immune cell contexture in pCR and non-responder (NR) groups in baseline analysis. Generalized linear mixed model (GLMM) analyses on baseline data from CIBERSORT was conducted using the ‘lme4’ package in R to investigate whether a systemic relationship of appropriate immune cell signatures occur across the pooled data. Statistical hypothesis on baseline data was applied to observe differences between pCR and NR groups. Testing on paired data was conducted to observe the differences in immune contexture between baseline and on-treatment. Results: Preliminary results of baseline analysis using CIBERSORT revealed a non-significant trend in reduced follicular helper T-cells and plasma cells in the pCR group amongst three neoadjuvant studies (Brodsky, CHER-LOB and TransNOAH). ESTIMATE analysis observed a trend in elevated immune infiltrate in pCR groups from two studies (Brodsky and CHER-LOB), but was not significant after multiple correction. Paired data analysis using CIBERSORT revealed that single-agent trastuzumab reduced activated natural killer cells (p&lt;0.05) in the 03-311 study, whilst single-agent trastuzumab did not lead to changes in immune contexture in TRIO-US B07. Furthermore, trastuzumab in dual combination with lapatinib increased resting dendritic cells, memory B-cells and stromal cells, and reduced naive B-cells and activated dendritic cells (p&lt;0.05) in TRIO-US. ESTIMATE analysis on paired data observed immune infiltration following trastuzumab alone in 03-311 (p=0.01) and stromal infiltration following dual combination in TRIO-US B07 (p=0.03). Neither immune subset was associated to pCR in all treatment arms of the on-treatment analysis.

Citation Format: Dalal AlSultan, Alex J. Eustace, Stephen F. Madden, John Crown. Exploring immune contexture using computational approaches in HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2717.

Abstract 3988: Identification of HER4 mutations with potential as biomarkers of response to neratinib

Background: HER4 is a member of the human epidermal growth factor receptor (HER/ErbB) family of receptor tyrosine kinases. HER4 is activated through ligand binding, transmitting intracellular signals by homodimerizing, or by heterodimerizing with other family members (EGFR, HER2, HER3). The role of HER4 in cancer or normal tissue has not been studied as comprehensively as EGFR and HER2, potentially due to a more complex biology that includes four different isoforms and different stability/tissue-specific expression patterns, and oncogenic or oncosuppressor roles. The oral, irreversible pan-HER (EGFR, HER2, HER4) tyrosine kinase inhibitor (TKI) neratinib (NER) is clinically active against HER2-mutant and HER2-amplified cancers. Using publicly available datasets including cBioPortal and COSMIC and predicted structural and functional impacts, this study aimed to identify HER4 mutations with the greatest oncogenic potential that may have value as potential biomarkers of response to NER.

Methods: The frequency of HER4 mutations across 33 cancer types was determined by using the clinical database cBioPortal and TCGA PanCancer Atlas datasets (n=10967). A shortlist of potentially oncogenic HER4 mutations was created based on the occurrence in cBioPortal and COSMIC databases, annotation as putative driver and cancer hotspot, structural and functional impacts according to OncoKB, Mutation Assessor, SIFT and Polyphen-2 software, and HER4 protein folding studies. Analysis was carried out using the R-studio statistical environment.

Results: HER4 amplification is rare in cancer, with the majority of genetic changes reported as point mutations; particularly missense (31.93%), synonymous (6.43%) and nonsense (3%) substitutions. Melanoma and esophagogastric (EG) cancers showed the highest HER4 alteration frequency, 17.34% and 13.42%, respectively, across different cancer types in the cBioPortal database. Melanoma and EG cancers showed the second and third highest absolute count of HER4 genomic alterations (n=77 and n=69, respectively). Based on the criteria outlined in methods, a priority list of HER4 mutations with greatest oncogenic potential was curated for melanoma (HER4 R106C, R306C, R711C, G936E, F1003I), stomach (HER4 C217R, S774N, K1002R, Y1150C) and esophageal (HER4 R488W, S449Y) adenocarcinomas. Mutations at these sites, located across ligand-binding, dimerization and intracellular signaling domains, have the potential to impact HER4 activity and thus possibly act as biomarkers of response to an irreversible pan-HER TKI like NER.

Conclusions: These data suggest that melanoma and EG cancers are the cancer types with the highest rate of HER4 mutations. In vitro functional characterization of the identified HER4 mutations is now required to further explore their value as biomarkers of response to NER.

Citation Format: Marta Valenti, Neil T. Conlon, Lisa D. Eli, Irmina Diala, John Crown, Denis M. Collins. Identification of HER4 mutations with potential as biomarkers of response to neratinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3988.

Neratinib plus fulvestrant plus trastzuzumab (N+F+T) for hormone receptor-positive (HR+), HER2-negative, HER2-mutant metastatic breast cancer (MBC): Outcomes and biomarker analysis from the SUMMIT trial

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Background: N is an oral, irreversible pan-HER TKI with activity against HER2 mutations. Genomic analyses from the SUMMIT MBC cohort following N±F suggest that resistance to N may occur via mutant allele amplification or secondary HER2 mutations. Adding T to N+F in SUMMIT showed encouraging durable responses in patients (pts) with HR+, HER2-mutant MBC and prior CDK4/6 inhibitors (CDK4/6i). Methods: SUMMIT (NCT01953926) enrolled pts with HR+, HER2-negative MBC with activating HER2 mutation(s) and prior CDK4/6i. Pts received N+F+T (oral N 240 mg/d with loperamide prophylaxis, im F 500 mg d1&15 of cycle 1 then q4w, iv T 8 mg/kg initially then 6 mg/kg q3w). During the small, randomized portion of the trial, pts received N+F+T, F+T or F (1:1:1 ratio). Pts randomized to F+T or F could crossover to N+F+T at progression. Efficacy endpoints: investigator-assessed ORR and CBR (RECIST v1.1); DOR; best overall response. Pre-treatment tumor tissue was centrally assessed retrospectively by next-generation sequencing. ctDNA from patient samples was assessed by NGS. Results: SUMMIT has completed enrolment; we report efficacy from 45 pts in the N+F+T cohort, plus 10 pts who progressed on F (n=6) or F+T (n=4) and crossed over to N+F+T (Table). HER2 allelic variants in the 45 N+F+T pts and ORR (%) (pts may have >1 mutation) were: V777L (n=6, 50%), L755S/P (n=15, 40%), S310F (n=4, 50%), exon 20 insertion (n=11, 36%), other KD missense (n=6, 33%), TMD missense (n=2, 0%), exon 19 deletion (n=1, 0%). Conclusions: N+F+T is a promising combination for HR+, HER2-mutated MBC with prior exposure to CDK4/6i, across a range of activating HER2 mutations. Results from the upcoming Apr 2022 data cut, including biomarkers, safety, mechanisms of acquired resistance, and preclinical mechanism of N+T, will be presented. Clinical trial information: NCT01953926. [Table: see text]

CD45-positive tumor infiltrating lymphocytes in early-stage hormone-positive, HER2-negative (ER+/HER2-) breast cancer: Correlation with proliferation and prognostic signature scores

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Background: Tumour infiltrating lymphocytes (TILs), have been associated in higher responses to treatment and are thought to be a prognostic marker in a number of cancer types. The role of TILs in breast cancer varies depending on the molecular subtype of the disease. In hormone positive, HER2-negative breast cancer, the significance of TILs is less clear, partly due to the paucity of data in this area. We aim to assess overall TILs in early-stage, hormone-positive, HER2-negative (ER+/HER2-) breast cancer and its relationship with proliferation index, Ki67, and the 21-gene recurrence score. Methods: Archival patient tissue samples of early-stage, ER+/HER2- breast cancer from the Irish arm of the TAILORx clinical trial were used. Full-face sections of these tumours were stained with anti-CD45 antibody (DAKA clone M0701) via the automated Leica Bond III system. A watershed cell-detection algorithm from the open-source digital pathology software, QuPath, was fine-tuned to identify true cell objects and positive immune markers. Optimised detection parameters were used to calculate the percentage of overall CD45+ cells (CD45%) within the tumour area. Patient TIL categories were dichotomised into High v Low CD45%, with 10% chosen as the threshold. CD45% was further correlated with proliferation index, clinical data, and 21-gene recurrence score. Results: 409 samples were included in the analysis. The mean CD45% was 5.96, with samples ranging from 0.13 to 78.86. The majority of samples were in the range of 0-10% of CD45% positivity with 89% (n = 367) patients in this category. Stratification of the cohort by 21-gene-recurrence score (RS) into Low, Intermediate and High, showed a statistically significantly high CD45% in patients with a High RS compared to Low RS (p = 0.0015). When divided by recurrence score group, high CD45% trended toward a lower disease free survival (DFS) when compared to low CD45%, with statistical significance found in those in the Intermediate RS chemotherapy treatment arm (p = 0.009). Conclusions: The role of TILs in ER+/HER2- breast cancer is still undefined. While a High RS was associated with a higher percentage of CD45-positive lymphocytes, the impact on recurrence and response to treatment remains unclear. Further studies to assess the role of different tumour infiltrating lymphocyte phenotypes, and the spatial distribution of assessed markers, are needed.

Whole genome sequencing of HER2+ metastatic breast cancer and CNA comparison between long term survivor and short-term survivor

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Background: The introduction of anti-HER2 therapies such as trastuzumab for HER2+ metastatic breast cancer (MBC) has led to significant improvements to disease progression. We and others have reported long-term durable complete response to trastuzumab in patients with HER2+ MBC. We hypothesise that genomic copy number alteration (CNA) and tumour mutational burden (TMB) may act as a prognostic measure of predicting response to trastuzumab in long-term survivors (LTS) compared to short-term survivors (STS). Using whole-genome sequencing (WGS) to detect these alterations, we aim to identify the molecular characteristics of primary and metastatic lesions in patients with metastatic HER2+ breast cancer. Methods: WGS was performed on samples from two patients from a HER2+ MBC cohort; a of long-term survivor (PFS 27 months; OS > 60 months) and a short-term survivor (PFS 4 months; OS < 14 months). Primary tumours, adjacent normal tissue and metastases were sequenced at a mean depth of 60X. Reads were aligned on the hg38 reference genome using Burrows-Wheeler Aligner (bwa), CNA were detected using Control-FREEC to evaluate total CNA burden. Single nucleotide variants were detected using GATK Mutect2 to calculate TMB. Results: Analysis of DNA chromosome disruption (fraction of the genome amplified/deleted) revealed a higher overall fraction of disrupted genome in the LTS primary tumour and metastasis compared with the STS (0.061 and 0.064 vs 0.031 and 0.047, respectively). Further delineation of the distribution of CNA burden in all genomes identified chr1 as the most altered in the STS samples whereas chr17 was the most disrupted in the LTS samples. HER2 and CDK12 were amplified in both LTS and STS samples (4 copies in LTS primary tumour and metastasis, 18 and 14 copies in STS primary tumour and metastasis respectively). A high TMB was estimated in both samples but was higher in the STS primary tumour than in the LTS one (161 vs 142, respectively). TMB was increased in LTS metastatic lesions. NRAS mutation was found in LTS primary tumour but was lost in the metastasis. Conclusions: This pilot study highlights the potential for whole-genome sequencing to identify CNA and TMB in HER2+ MBC in patients who display long-term and short-term survival. Further samples from this cohort need to be studied to investigate the relationship between CNA burden and HER2+ MBC patient survival.

Assessment of tumour infiltrating subpopulations and pathological complete response using multiplex immunohistochemistry and digital pathology in early HER2+ breast cancer

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Background: The treatment of HER2+ breast cancer (BC) has improved substantially with the use of targeted therapies, and patients achieving pathological complete response (pCR) following neoadjuvant therapy have significantly improved disease free survival. However, there is currently no way to determine which patients are most likely to respond to neoadjuvant HER2-targeting treatment. Growing evidence indicates tumour infiltrating lymphocytes influence HER2+ BC outcome. We hypothesize that a deeper investigation of the immune landscape of HER2+ patient tumours may improve patient stratification and identify an immune profile associated with pCR. Methods: 3plex immunohistochemistry panels identifying immune cell subpopulations and tertiary lymphoid structures were applied to HER2+ BC tumors (pre-treatment N=19, post-treatment N=9) of patients of the neoadjuvant TCHL clinical trial (NCT01485926), who received HER2-targeting therapy. Quantitative analysis of CD3+, CD20+, DC-Lamp+, CD4+, and CD8+ immune cells on multi-labelled whole-slide images of TCHL tumor sections was performed using artificial intelligence image analysis models. Patient-specific densities of each cell type in tumor regions were determined to facilitate assessment of pre-treatment differences in target immune subpopulations in complete, partial, and non-responders. Results: Statistical analysis demonstrated a trend for higher densities of each immune subpopulation in pre-treatment biopsies of pCR vs. non-pCR patients. Patient categorisation based on median threshold demonstrated patients achieving pCR are more frequently high for each immune cell type assessed, while non-pCR patients are more frequently in the low category. Investigation of association of pre-treatment immune infiltrate with clinicopathological features demonstrated trends for higher levels of T-cell infiltration in later stage and hormone receptor negative patients. Conclusions: Multiplex IHC is an optimal technique for the concurrent assessment of multiple target markers in patient tissue, which can be quantitatively analyzed in a high throughput manner using AI models. The findings of this preliminary study support recent evidence regarding the role of tumor infiltrating immune cells in HER2+ BC outcome and warrant further investigation in a larger cohort.

Pilot study of the implementation of G8 screening tool, cognitive screening assessment and chemotherapy toxicity assessment in older adults with cancer in a tertiary University Hospital in Ireland

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Background: 11% of Ireland’s population is above the age of 65. This is projected to double to 1.4 million by 2040 corresponding to doubling of cancer cases. Clinical trials often exclude patients (pts) ≥70; therefore, it can be challenging to apply evidence based treatment (tx) to this population. Data from the National Cancer Registry of Ireland suggests under tx of older patients (pts). Comprehensive Geriatric assessment (CGA) is recommended by the National Comprehensive Cancer Network (NCCN) and the International Society of Geriatric Oncology (SIOG). In practice, CGA is limited by time constraints, lack of resources and expert interpretation. Geriatric screening tools can help identify frail pts who are most likely to benefit from CGA. The primary objective of this pilot study was to establish the prevalence of frailty (assessed by G8), presence of cognitive impairment (assessed by Mini-Cog), and risk of chemo-toxicity (assessed by Chemo-Toxicity Calculator) among pts ≥ 65 years (yrs) starting systemic anti-cancer tx. Methods: Pts ≥65yrs starting new systemic anticancer tx were identified between 1st of December 2020 to 31ST of September 2021 in St. Vincent’s University Hospital. Verbal consent was obtained. Printed versions of the G8 screening tool and Mini-Cog were used. CARG chemo-toxicity score was conducted online ( www.mycarg.org/tools ). .The assessment was conducted by consultants, specialist registrars and registrars. Data including pts’ age, type of malignancy, stage of cancer, and planned treatment were recorded. Analysis was conducted by SPSS statistical software, V.25(SPSS Institute, IBM Corp., 2017). Results: We identified 56 pts ≥65 years.27 (48.1%) were females and 29 (50.8%) were males. The majority of treated pts, N = 33 (58.1%) had metastatic cancer. The median G8 score was 12 (IQR 9.6-14). 83.9% of pts had a G8 score ≤14. Mini-Cog was found to be positive in 11 pts (19.6%). The median CARG score was 7 (IQR 6-11) and the median risk of toxicity 51% (IQR 44-78%). Of these, 44 (78.2%) received chemotherapy and 12 pts (21.4%) received non-chemotherapy systemic tx. In multi-variate analyses, age, type of cancer, planned treatment, and stage of disease did not impact G8, Min-cog, and CARG scores. Conclusions: In this single center study of elderly pts, more than 80% of pts had a positive G8 score representing a need for formal CGA assessment. The risk of toxicity was substantial with almost 50% risk of grade ≥ 3 toxicity in this cohort. Chronological age was not found to negatively impact patient’s frailty, cognition, or risk of toxicity. Interpretation of this pilot study is limited by small sample size, possible inter-operator variability, and lack of self-reported assessment.

Clinical Impact of Immune Checkpoint Inhibitor (ICI) Response, DNA Damage Repair (DDR) Gene Mutations and Immune-Cell Infiltration in Metastatic Melanoma Subtypes

Molecular and histopathological analysis of melanoma subtypes has revealed distinct epidemiological, genetic, and clinical features. However, immunotherapy for advanced metastatic melanoma patients does not differ based on subtype. Response to immune checkpoint inhibitors (ICI) has been shown to vary, therefore, predictive biomarkers are needed in the design of precision treatments. Targeted sequencing and histopathological analysis (CD8 and CD20 immunohistochemistry) were performed on subtypes of metastatic melanoma (cutaneous melanoma (CM, n = 10); head and neck melanoma (HNM, n = 7); uveal melanoma (UM, n = 4); acral lentiginous melanoma (AM, n = 1) and mucosal melanoma (MM, n = 1) treated with ICI). Progression-free survival (PFS) was significantly associated with high CD8 expression (p = 0.025) and mutations in DNA damage repair (DDR) pathway genes (p = 0.012) in all subtypes but not with CD20 expression. Our study identified that immune cell infiltration and DDR gene mutations may have an impact in response to ICI treatment in metastatic melanoma but differs among subtypes. Therefore, a comprehensive understanding of the immune infiltration cells' role and DDR gene mutations in metastatic melanoma may identify prognostic biomarkers.

Endometrial Mesonephric-like Adenocarcinoma Presenting as an Ocular Lesion: A Case Report

Endometrial mesonephric-like carcinoma (ML-CA) is a recently recognized subtype of aggressive endometrial adenocarcinoma that is morphologically and immunophenotypically similar to mesonephric carcinoma but not typically associated with mesonephric remnants. Here, we report a case of 58-yr-old female who had a past medical history of fibroids and of irregular menstrual bleeding for ~20 yr who presented with visual disturbance. On further investigation, she was found to have a large choroidal peri-papillary tumor of the right eye. A presumptive diagnosis of choroidal melanoma was made. Right eye enucleation was performed, and microscopy revealed moderately differentiated metastatic adenocarcinoma. Further work up was advised. A uterine mass was identified on imaging followed by endometrial biopsy that showed a morphologically and immunohistochemically similar tumor to that in the eye. A hysterectomy was carried out and a malignant neoplasm with varying morphologic patterns including gland formation, solid sheets of tumor cells, cribriform, glomeruloid, spindled and papillary areas was seen. The immunohistochemical profile showed diffuse strong positivity for AE1/AE3, TTF1, P16, and vimentin. CD56, GATA3, Napsin A, and CD10 were focally positive. The neoplastic cells were negative for the following markers ER, PR, WT1, calretinin, and synaptophysin. PDL-1 was negative and mismatch repair protein was proficient. An identical KRAS mutation was detected in both the uterine corpus and ocular tumors. The findings are in keeping with a uterine mesonephric-like adenocarcinoma with an ocular metastasis. An Oncomine Focus-Mutation profile, Thermo-Fisher Scientific Inc., a 60 gene oncologic panel, performed on the ocular tumor, revealed no further mutations.

Abstract P2-13-28: Inhibiting retinoic acid receptor signalling enhances the effect of neratinib in HER2 positive breast cancer cell lines

Introduction: Treatment strategies for HER2+ breast cancer (BC) involves first line treatment with the monoclonal antibody trastuzumab, however resistance to treatment can occur. The pan-HER tyrosine kinase inhibitor neratinib is an approved adjuvant treatment for early stage HER2+ BC after one year of treatment with trastuzumab. Recent studies have highlighted the potential benefits of using retinoic acid as an adjuvant treatment for BC. The retinoic acid receptor (RAR) family of nuclear transcription factors consists of RARα, RARβ and RARγ. Interestingly ~30% of HER2+ BC have a co-amplification of the RARA gene, which codes for RARα. We examined the effect of RARα agonists (Fenretinide & AM580) and antagonist (AGN194310) in combination with neratinib in two HER2+ cell lines: SKBR3, has co-amplification of ERBB2 and RARA, and HCC1569 has amplified ERBB2 but are not RARA-amplified. Methods: SKBR3 and HCC1569 cell lines were cultured in RPMI/10% FCS at 370C/5% CO2. 10mM stock concentrations of fenretinide (H7779-Sigma), AM580 (A8843-Sigma), AGN194310 (SML2665-Sigma) and neratinib (Puma Biotechnology, Inc) were prepared in DMSO. For proliferation assays, cells were seeded in 96 well plates at a density of 3 X 104 cells per well for 24h. Cells were treated with a drug alone (2X concentration) or combination of drugs (4X concentration) in 100μL of medium. Proliferation was measured using an acid phosphatase-based assay after 5 days as percentage growth versus DMSO control. The half maximal inhibitory concentration (IC50) was calculated for each drug, using CalcuSyn. The combination assays were performed using fixed ratios. The combination index (CI) values were calculated at the effective dose that inhibits 50% growth (ED50), using CalcuSyn. Values &lt; 1 represent a synergistic effect, a value of 1 is additive and values &gt; 1 represent an antagonistic effect. All data presented as the mean of biological triplicate experiments ± standard deviation. Results: This research has found that the synthetic retinoic acid fenretinide, a pan-RAR (α, β and γ) activator, was more potent in the HCC1569 cells compared to the SKBR3 cell line with an IC50 of 0.21 ± 0.03μM compared to 4.55 ± 0.87 μM, respectively. However, when combined with neratinib there was a strong antagonistic effect observed in the HCC1569 cell line (CI value: 15.63 ± 9.5). Conversely, fenretinide enhanced the effect of neratinib in the SKBR3 cell line (CI value: 0.83 ± 0.4). The RARα-specific activator AM580 had an IC50 &gt;10μM for both cell lines. When combined with neratinib there was an additive effect observed in the RARα negative HCC1569 cells (CI value: 0.97 ± 0.4), and a synergistic effect observed in the RARα upregulated SKBR3 cell line (CI value: 0.78 ± 0.08). Next we wanted to determine if inhibiting RAR activity would have any effect on the proliferation of these cell lines. The IC50 for the pan-RAR (α, β and γ) antagonist AGN194310 was &gt;10μM for each cell line. However, when combined with neratinib treatment there was a strong synergistic effect observed in the HCC1569 cell line (CI value: 0.52 ± 0.17) and the SKBR3 cell line (CI value: 0.66 ± 0.19). Conclusions: This study suggests a differential effect of RAR agonists when combined with neratinib in RARα amplified versus non-amplified HER2+ BC. Targeting RAR signalling, particularly with a RAR antagonist, in combination with the pan-HER inhibitor warrants further investigation in HER2+ BC.

Citation Format: Debbie O'Reilly, Nicola Gaynor, Neil Conlon, Irmina Diala, Lisa D Eli, John Crown, Denis M Collins. Inhibiting retinoic acid receptor signalling enhances the effect of neratinib in HER2 positive breast cancer cell lines [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-28.

Abstract GS4-10: Neratinib + fulvestrant + trastuzumab for hormone receptor-positive, HER2-mutant metastatic breast cancer and neratinib + trastuzumab for triple-negative disease: Latest updates from the SUMMIT trial

Background: HER2 mutations are oncogenic drivers in a subset of metastatic breast cancers (MBC). Neratinib (N) is an oral, irreversible pan-HER tyrosine kinase inhibitor with preclinical and clinical activity against HER2 mutations. Genomic analyses from paired biopsies following N ± fulvestrant (F) suggest that resistance to N may occur via amplification of the mutant allele or by acquisition of secondary HER2 mutations. Addition of trastuzumab (T) to N+F showed encouraging clinical activity with durable responses in the SUMMIT trial in hormone receptor-positive (HR+), HER2-mutant MBC, including patients (pts) who had previously received cyclin-dependent kinase 4 & 6 inhibitors (CDK4/6i) [Jhaveri et al. SABCS 2020]. On the basis of these findings, and in order to better understand the contribution of N to the activity of the N+F+T combination, SUMMIT has recently been expanded to include a randomized Simon 2-stage comparison of N+F+T vs. F+T vs. F in pts with HR+, HER2-mutated, HER2-negative MBC who were exposed to CDK4/6i. Enrollment for stage 1 is now complete (N+F+T, n=7; F+T, n=7; F, n=7), and results will be forthcoming once the data are mature. Here we report updated findings from the breast cancer cohorts of the SUMMIT trial for which data are currently available. Methods: The phase 2 SUMMIT trial (NCT01953926) enrolled pts with HR+, HER2-negative MBC whose tumors harbored activating HER2 mutation(s) identified by genomic sequencing. Prior to starting the randomized portion of the trial, these patients were enrolled in a non-randomized cohort and received N+F+T (oral N 240 mg/d, i.m. F 500 mg d1&15 of cycle 1 then q4w, i.v. T 8 mg/kg initially then 6 mg/kg q3w). Following initiation of the randomized portion of the trial, these pts received N+F+T, F+T or F (1:1:1 ratio; dose schedules as above). Pts with HER2-mutant triple-negative breast cancer (TNBC) were enrolled in a non-randomized cohort and received N+T (dose schedules as above). Loperamide prophylaxis was mandatory during the first 2 treatment cycles. There was no restriction on the number of prior lines of systemic therapy for MBC. Efficacy endpoints: investigator-assessed objective response rate and clinical benefit rate (RECIST v1.1 or other defined criteria); duration of response; best overall response. Results: Prior to enrolling the randomized cohort, 24 pts with HR+, HER2-mutated MBC who had previously received CDK4/6i were enrolled in the non-randomized cohort and received N+F+T, and 17 pts with HER2-mutant TNBC were enrolled and received N+T, as of 18-Jun-2021. Data for randomized pts are not yet mature. HER2 allelic variants across both cohorts (pts may have &gt;1 mutation): kinase domain hotspots (n=26); exon-20 insertion (n=9); extracellular domain hotspot (n=4); exon-19 deletion (n=1); transmembrane domain missense (n=1); kinase domain non-hotspot (n=2). Efficacy findings are reported in the Table. Diarrhea was the most commonly reported adverse event: N+F+T (non-randomized cohort), 96%; N+T (TNBC cohort), 94%. No grade 4 diarrhea was reported.

Conclusions: N+F+T is a promising combination for pts with HR+, HER2-mutated MBC with prior exposure to CDK4/6 inhibitors. N+T also showed encouraging activity in HER2-mutated TNBC. The first results from the randomized comparison of N+F+T vs. F+T vs. F in pts with HR+, HER2-mutated MBC (Simon stage 1 analysis) will be presented at the meeting.

Table: Efficacy findingsHR+, HER2-mutated, HER2-non-amplified MBCHER2-mutant TNBCN+F+T (n=24)N+T (n=17)Confirmed objective response,a n (%)11 (46)5 (29)CR0 (0)1 (6)PR11 (46)4 (24)ORR, % (95% CI)46 (26–67)29 (10–56)Best overall response, n (%)13 (54)7 (41)CR0 (0)1 (6)PR13 (54)6 (35)Best overall response rate, % (95% CI)54 (33–74)41 (18–67)Medianb DOR, months (95% CI)14.4 (6.4–NR)NRClinical benefit, n (%)14 (58)6 (35)CR or PR11 (46)5 (29)SD ≥24 weeks3 (13)1 (6)CBR,b % (95% CI)58 (37–78)35 (14–62)aORR defined as either a CR or PR confirmed no less than 4 weeks after the response criteria are met; bCBR defined as confirmed CR or PR or SD for ≥24 weeks. Note: Tumor response is based on investigator tumor assessments per RECIST v1.1 for HR+, HER2-mutated cohort, and RECIST v1.1 or modified PERCIST for HER2-mutated TNBC cohort. CBR, clinical benefit rate; CI, confidence interval; CR, complete response; DOR, duration of response; F, fulvestrant; HR+, hormone receptor-positive; MBC, metastatic breast cancer; N, neratinib; NR, not reached; ORR, objective response rate; PERCIST, Positron Emission Tomography Response Criteria in Solid Tumors; PR, partial response; RECIST, Response Evaluation Criteria in Solid Tumors; SD, stable disease; T, trastuzumab, TNBC, triple-negative breast cancer.

Citation Format: Komal Jhaveri, Haeseong Park, James Waisman, Jonathan W Goldman, Angel Guerrero-Zotano, Valentina Boni, Barbara Haley, Ingrid A Mayer, Adam Brufsky, Eddy S Yang, José A García-Sáenz, François-Clement Bidard, John Crown, Bo Zhang, Aimee Frazier, Irmina Diala, Lisa D Eli, Brian Barnett, Hans Wildiers. Neratinib + fulvestrant + trastuzumab for hormone receptor-positive, HER2-mutant metastatic breast cancer and neratinib + trastuzumab for triple-negative disease: Latest updates from the SUMMIT trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS4-10.

Abstract P2-08-09: Investigation of autoantibodies (AAbs) in HER2+ breast cancer (BC) patients treated in the neo-adjuvant setting

Background: HER2+ breast cancer is treated with anti-HER2 IgG monoclonal antibody therapies such as trastuzumab and pertuzumab. These antibodies inhibit HER2-driven intracellular signaling and can also be described as a form of passive immunotherapy, engaging effector immune cells in antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP). Tumor-associated autoantibodies (AAbs) to tumor neo-antigens can be generated by the adaptive immune response before, or in response to, therapy. There is growing evidence of a functional role for tumor-associated AAbs in the immune response to tumors, with IgG and IgA AAbs capable of mediating ADCC and ADCP. Using the innovative Nucleic Acid-Programmable Protein Array (NAPPA) platform we examined the levels and targets of circulating AAbs to ~1700 human proteins before, during and after treatment in HER2+ breast cancer treated in the neo-adjuvant setting. . Methods: Pre-treatment, On-treatment (pre- Cycle 2) and Post-treatment (post-Cycle 6) serum samples were obtained from HER2+ breast cancer patients (n=19) treated on the ICORG 10-05 clinical trial. Patients were treated with neo-adjuvant chemotherapy (docetaxel (T)/carboplatin (C)) +/- trastuzumab (H), lapatinib (L) or HL, TCH n=9, TCHL n= 7, TCL n=3. Patients were classified as having a pathological complete response (pCR, n=6), a partial response (PR, n=6) or a non-response (NR, n=7) to treatment. IgG and IgA autoantibody levels were determined using the HD-NAPPA system, focussing on a subset of ~ 1700 human protein targets. A normalised intensity score of &gt 5 was utilised as a cut-off for detection. Results: 92 IgG AAbs and 29 IgA AAbs were detected in all samples, across all timepoints (n=57). When IgG AAbs were divided by patient response, 26 AAbs unique to pCR, 26 AAbs unique to PR and 16 AAbs unique to NR were detected. 5 IgG AAbs (BCL11B, MAP6, PRDM8, SYTL2, TP53BP2) were common to all HER2+ breast cancer patients. When IgA AAbs were divided by patient response, 11 AAbs unique to pCR, 6 AAbs unique to PR and 7 AAbs unique to NR were detected. 2 IgA AAbs (TDP1 and MAP6) were common to all HER2+ breast cancer patients. Treatment-induced AAbs were detected in On-treatment and Post- treatment samples in 16/19 patients examined. Conclusions: Our results suggest HER2+ BC patients have unique circulating AAbs associated with treatment response and AAb levels change in response to treatment. Further investigation of AAb levels as biomarkers of response in HER2+ BC is warranted in a larger cohort of patients.

Citation Format: Denis Martin Collins, Ji Qiu, Jaine Blayney, Nuala McCabe, Richard Kennedy, Joshua LaBaer, John Crown. Investigation of autoantibodies (AAbs) in HER2+ breast cancer (BC) patients treated in the neo-adjuvant setting [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-08-09.

Abstract P2-13-36: Comparative time course analysis of the effects of neratinib, lapatinib and tucatinib in an in vitro HER2+ breast cancer model

Introduction: Human epidermal growth factor 2 (HER2/ErbB2) is overexpressed in approximately 20% of breast cancers. The HER2-targeted tyrosine kinase inhibitors (TKIs) neratinib, lapatinib and tucatinib are all FDA-approved for the treatment of HER2-positive breast cancer. All three inhibit the HER2 kinase domain but differ in binding characteristics (the irreversible neratinib vs reversible lapatinib and tucatinib) and their affinity for other HER family members. The aim of this study was to carry out kinetic analysis of the effect of the three TKIs on HER family signalling, cellular proliferation, and apoptosis induction in a cell model of breast cancer. Methods: In this study, the anti-proliferative effects of the three TKIs were assessed in the HER2-amplified breast cancer cell line SKBR3 by acid phosphatase assay (5-day endpoint assay) and with the IncuCyte→ live-cell imaging system over 120 hours. TKI IC50 values were calculated using CalcuSyn software. Apoptotic cells were detected every 3 hours for 5 days using the Incucyte→ Caspase 3/7 dye. Western blotting was used to investigate the time course effects (15 min, 6 h, 24 h, 72 h) of the TKIs on the expression and phosphorylation of EGFR, HER2 and on their downstream effectors ERK1/2 and Akt. Results: All three TKIs displayed nanomolar activity against SKBR3 cells. Neratinib showed the greatest anti-proliferative effect (IC50 = 3.4 ± 1.1 nM), followed by tucatinib (IC50 = 37.5 ± 18.4 nM) and lapatinib (IC50 = 51.0 ± 23.0 nM). 50 nM neratinib induced higher activation of caspase 3/7 than 500 nM lapatinib or 500 nM tucatinib. Total levels of HER2 and EGFR were increased in the presence of lapatinib and tucatinib, but decreased in the presence of neratinib. The three drugs (500 nM) significantly inhibited the activation of EGFR and HER2 at 15 min. From 6 h to 72 h, treatment with 5 nM and 50 nM neratinib resulted in greater inhibition of phosphorylated HER2 and EGFR, compared to the equivalent concentration of lapatinib or tucatinib. All three TKIs (500 nM) inhibited the activity of phospho-Akt at the earliest timepoint (15 min), but a strong impact on downstream ERK1/2 phosphorylation was not observed until the 6h timepoint. 50 and 500 nM neratinib was more effective at preventing reactivation of ERK1/2 and Akt phosphorylation than either 500 nM lapatinib or tucatinib at 72 h. Conclusion: These data highlight the differences in in vitro efficacy of the three HER2-targeting TKIs currently approved for the treatment of HER2+ breast cancer in the clinic. Neratinib inhibits HER2 and EGFR at lower concentrations and for longer compared to lapatinib and tucatinib, resulting in increased apoptosis induction. This may be due to the irreversible nature of neratinib binding, as opposed to the reversible nature of lapatinib and tucatinib binding. Further comparative studies between neratinib, lapatinib and tucatinib are warranted to explore the impact of varied pre-clinical characteristics on the emergence of therapeutic resistance.

Citation Format: Myra E Castel, Neil T Conlon, Naomi Walsh, Irmina Diala, Lisa Eli, John Crown, Denis M Collins. Comparative time course analysis of the effects of neratinib, lapatinib and tucatinib in an in vitro HER2+ breast cancer model [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-36.

Abstract P2-13-39: Investigation of neratinib and endocrine therapy combinations in HER2 positive breast cancer models

Background: HER2-positive (+) breast cancer (BC) represents a significant clinical burden due to an aggressive phenotype and propensity for brain metastasis. Up to 70 % of HER2+ BCs are also oestrogen receptor (ER)-positive, with receptor crosstalk often attributed to anti-HER2 therapeutic resistance. Neratinib is a pan-HER tyrosine kinase inhibitor, currently approved for the treatment of HER2+ BC. Dual-blockade with anti-HER2 and endocrine therapies (ETs) has shown positive outcomes in clinical trials, without the added toll of traditional chemotherapy. Fulvestrant is the only currently approved selective ER degrader (SERD), but it is hindered by poor bioavailability, leading to several orally available SERDs being developed. CDK4/6 inhibitors have been approved for ER+ BC, and trials are ongoing to see if their addition also benefits ER+/HER2+ BC patients. The aim of this study is to outline the benefit of ETs in HER2+ BC and to investigate neratinib/ET combinations with potential for the treatment of HER2+/ER+ BC. Methods: BC patient overall (OS) and recurrence free (RFS) survival and clinical data for a number of independent breast cancer studies was sourced from the METABRIC study via cBioportal and from KMplotter. Patients were stratified according to HER2 status, ER status and treatment with ET. GraphPad Prism 8 was then used to produce Kaplan-Meier graphs and to calculate difference in patient survival according to treatment with ET. Fulvestrant (SERD, #S1191), AZD9496 (novel, orally bioavailable SERD, #S8372) and ribociclib (CDK4/6 inhibitor, #S7440) were obtained from Selleckchem. Neratinib was obtained from Puma Biotechnology, Inc. Estradiol (Sigma, #E2758) treatment was carried out at 1nM. To assess drug effect, the HER2+/ER+ BC cell line BT-474 was treated for 5 days before growth inhibition was measured using an acid phosphatase-based proliferation assay. Compounds were combined at fixed ratios. Drug IC50 and combination index (CI) values were calculated using Calcusyn. Results: Analysis of the METABRIC study shows HER2+ BC patients who receive ET, numerically experience a longer median survival, with particular separation seen in early OS (ET = 113.8 months vs no ET= 85.50 months, HR= 0.8797, 95% CI: 0.6402 - 1.209, p=0.0987). In addition, analysis of KMPlotter data shows HER2+ patients who receive ET may also experience greater 5 year RFS (HR= 0.7639, 95% CI: 0.5452 to 1.070, p= 0.0539). Despite this potential benefit, the METABRIC dataset showed within a cohort of HER2+ patients, 10.5% were ER+ but did not receive ET. An in vitro cell line model of HER2+/ER+ BC was highly sensitive to neratinib (N) at nanomolar concentrations (IC50 = 2.0549± 0.7 nM). In contrast, fulvestrant (F), AZD9496 (A) and ribociclib (R) were less effective as single agents and an IC50 was not achieved (% growth @ 5µM: F = 54.7 ± 8.5%, A = 61.3 ± 7.8% and R = 95.6 ± 8.7%). The combination of N with F was compared to N with A. Both combinations demonstrated synergy, defined as CI &lt; 1 @ ED50 (N+F CI value = 0.21385 ± 0.15, N+A CI value = 0.25448 ± 0.26). The combination of N + R did not improve the efficacy of N alone ( % growth at max, N = 6.8 ± 1.7% vs N +R = 10.8 ± 2.8%, p&gt;0.9999). Further, triplet combinations with R did not significantly affect cell growth for either the N + F or the N + A combinations (% growth @ max conc., N + F= 5.8 ± 1.6%, N+F+R = 7.2 ± 1.2 %, N+A= 8.2 ± 2%, N+A+R= 9.8 ± 1.7%, p&gt;0.9999). Estradiol supplementation at time of drug treatment significantly increased the growth inhibitory effect of A (p = 0.0489 @ 5µM). Conclusions: Using publicly available data, our results highlight the positive impact ET has on HER2+ breast cancer survival outcome. In vitro data supports the combination of novel SERDs and neratinib as a therapeutic strategy that warrants further investigation in HER2+/ER+ breast cancer.

Citation Format: Amira F Mahdi, Neil T Conlon, Lisa D Eli, Irmina Diala, John Crown, Denis Collins. Investigation of neratinib and endocrine therapy combinations in HER2 positive breast cancer models [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-39.

Abstract P5-16-08: Phase Ib/II trial evaluating safety and efficacy of copanlisib (PI3K inhibitor) and trastuzumab in pre-treated advanced HER2-positive breast cancer: Results from the PantHER study

Background: De novo and acquired resistance to HER2 directed therapy is frequently encountered. Upregulation of the phosphatidylinositol-3-kinase (PI3K) pathway is an important mediator of treatment resistance. This can occur through an activating mutation of the PIK3CA gene or PTEN loss. PIK3CA mutations are present in approximately 20% of HER2 positive breast cancers and as such, the PI3K pathway has emerged as an attractive target for restoring sensitivity to HER2 directed therapy. Methods: We performed a single arm, multicentre, open label Phase Ib/II trial. Patients (pts) with advanced HER2-positive breast cancer whose disease had progressed on at least 1 line of Trastuzumab/T-DM1 based treatment in the metastatic setting were eligible if they met following criteria: ECOG PS ≤ 2 and adequate organ function. Pts with treated, controlled brain metastases were permitted to enrol. Exclusion criteria included uncontrolled hypertension or diabetes mellitus. Pts on Phase IB were treated according to a 6+6 study design with a dose escalation schedule of Copanlisib IV (level 1 = 45mg, level 2 = 60mg) on Day 1, 8 and 15 of a 28-day cycle along with a fixed dose of Trastuzumab 2mg/kg weekly. Phase II treatment was the MTD (maximum tolerated dose) of Copanlisib in combination with Trastuzumab. Archival tumour tissue, voluntary biopsies and serial plasma samples were collected for genomic sequencing. Primary endpoints were MTD (Phase I) and clinical benefit rate (CBR) which was defined as complete response (CR) or partial response (PR) at any time point; or stable disease (SD) lasting at least 24 weeks (Phase II). Secondary endpoints included safety and tolerability, tumor response rate, duration of response, time to treatment failure (TTF) and progression free (PFS) and overall survival (OS). Results: Twelve pts were enrolled in Phase IB. No dose limiting toxicity was observed. The MTD was established as Copanlisib 60mg and Trastuzumab 2mg/kg. Fourteen pts were enrolled in Phase II (6 pts treated at the MTD in Phase IB were included in the final Phase II analysis resulting in a total of 20 pts). The median number of lines of prior treatment in the metastatic setting was 3 (1-8). The most common grade 3-4 toxicities encountered in the Phase Ib/II cohorts included hypertension (n=7, 27%), hyperglycaemia (n=2, 8%) and vomiting (n=2, 8%). Three pts discontinued treatment due to toxicity. The median follow-up for the Phase II cohort was 7.5 months (95% CI 6.0-14.5). PR was observed in 4 pts (20%) and SD (at any time point) was seen in 8 pts (40%). The CBR was 30% (n=6). The duration of response was 15.0 weeks (95% CI 4.9 - 16.1). The median TTF was 11.9 weeks (95% CI 7.5 - 21.1). The median PFS was 3.0 mo (95% CI 0.2 - 5.8) and OS was 14.0 mo (95% CI 5.2-22.8). At the time of analysis, 9 of 20 patients were alive. PIK3CA mutations were detectable in the archival tissue of 11 of 26 pts (42%). PIK3CA hotspot mutations (H1047R, E542K and E545K) were detectable in the plasma of all 26 pts at various points throughout treatment. Pre and post treatment biopsies of 2 pts in the Phase IB trial revealed somatic mutations in DNAH3 and TRRAP, the latter of which encodes a PI3K-like protein kinase. Targeted next generation sequencing was performed on the circulating tumour DNA of 20 pts in the Phase II cohort taken before, during and after treatment to further validate these findings and to assess for other mechanisms of response or resistance. The final translational results will be presented at the meeting. Conclusions: The combination of Copanlisib and Trastuzumab is a safe and tolerable regimen and is associated with clinical efficacy in a heavily pre-treated metastatic HER2-positive breast cancer population. Translational studies may have identified novel resistance biomarkers in this pt cohort.

Citation Format: Lisa Prior, Niamh M Keegan, Simon J Furney, Janice M Walshe, Giuseppe Gullo, John Crown, M John Kennedy, Diarmuid Smith, John McCaffrey, Catherine M Kelly, Keith Egan, Jennifer Kerr, Mark Given, Niall Sheehy, Peter O'Donovan, Andres Hernando, Ausra Teiserskiene, Imelda Parker, Elaine Kay, Ray McDermott, Maccon M Keane, Seamus O'Reilly, Liam Grogan, Oscar Breathnach, Patrick G Morris, Sinead Toomey, Bryan T Hennessy. Phase Ib/II trial evaluating safety and efficacy of copanlisib (PI3K inhibitor) and trastuzumab in pre-treated advanced HER2-positive breast cancer: Results from the PantHER study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-16-08.

Genetic polymorphisms and correlation with treatment induced cardiotoxicity and prognosis in breast cancer patients

BACKGROUND

Cardiac toxicity is a serious complication of HER2-directed therapies and anthracyclines. HER2 codon 655 and SLC28A3 gene polymorphisms have been reported to be associated with cardiac toxicity from anti-HER2 and anthracycline therapy, respectively. Association of the polymorphism at HER2 codon 655 with prognosis has also been reported.

METHODS

Whole blood samples from patients treated on a randomized adjuvant breast cancer trial (BCIRG-006) that compared anthracycline-based chemotherapy to trastuzumab plus either anthracycline or non-anthracycline chemotherapy were tested for genetic polymorphisms in HER2 codon 655 and SLC28A3 Genotypes were correlated with cardiac function and disease-free survival (DFS) outcomes.

RESULTS

Of 3,222 patients enrolled in BCIRG-006, 662 patient samples were successfully genotyped for the rs1136201 allele in HER2 (codon 655): 424 (64%) were AA, 30 (4.5%) were GG, and 208 (31%) were AG genotype. Additionally, 665 patient samples were successfully genotyped for the rs7853758 allele in the SLC28A3 gene: 19 (3%) were AA, 475 (71%) were GG, and 171 (26%) were AG genotype. Follow up time was 10 years. No correlation between DFS, cardiac event rate or mean left ventricular ejection fraction (LVEF) and rs1136201 genotype was seen in the trastuzumab treated or non-trastuzumab treated patients. Moreover, mean LVEF and cardiac event rates were similar in all rs7853758 genotype groups treated with anthracycline-based therapy.

CONCLUSIONS

In the largest study to date to evaluate whether two polymorphisms are associated with DFS and/or cardiac toxicity in HER2 positive breast cancer treated with trastuzumab and/or anthracyclines, we observed no correlation.

Use of Circulating Tumour DNA (ctDNA) for Measurement of Therapy Predictive Biomarkers in Patients with Cancer

Biomarkers that predict likely response or resistance to specific therapies are critical in personalising treatment for cancer patients. Such biomarkers are now available for an increasing number of anti-cancer therapies, especially targeted therapy and immunotherapy. The gold-standard method for determining predictive biomarkers requires tumour tissue. Obtaining tissue, however, is not always possible and even if possible, the amount or quality of tissue obtained may be inadequate for biomarker analysis. Tumour DNA, however, can be released into the bloodstream, giving rise to what is referred to as circulating tumour DNA (ctDNA). In contrast to tissue, blood can be obtained from effectively all patients in a minimally invasive and safe manner. Other advantages of blood over tissue for biomarker testing include a shorter turn-around time and an ability to perform serial measurements. Furthermore, blood should provide a more complete profile of mutations present in heterogeneous tumours than a single-needle tissue biopsy. A limitation of blood vis-à-vis tissue, however, is lower sensitivity and, thus, the possibility of missing an actionable mutation. Despite this limitation, blood-based predictive biomarkers, such as mutant EGFR for predicting response to EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer and mutant PIK3CA for predicting response to alpelisib in combination with fulvestrant in advanced breast cancer, may be used when tissue is unavailable. Although tissue remains the gold standard for detecting predictive biomarkers, it is likely that several further blood-based assays will soon be validated and used when tissue is unavailable or unsuitable for analysis.

Hepatic resection for breast cancer related liver metastases: A single institution experience

BACKGROUND & OBJECTIVE

Liver resection for breast cancer liver metastases is becoming a more widely accepted therapeutic option for selected groups of patients. The aim of this study was to describe the outcomes of patients undergoing liver resection for breast cancer-related liver metastases and identify any variables associated with recurrence or survival.

METHODS

A retrospective review of a prospectively maintained database was undertaken for the 12 year period between 2009 and 2021. Clinicopathological, treatment, intraoperative, recurrence, survival and follow-up data were collected on all patients. Kaplan-Meier methods, the log-rank test and Cox proportional hazards regression analysis were used to identify variables that were associated with recurrence and survival.

RESULTS

A total of 20 patients underwent 21 liver resections over the 12-year period. There were no deaths within 30 days of surgery and an operative morbidity occurred in 23.8% of cases. The median local recurrence free survival and disease free survival times were both 50 months, while the 5 year overall survival rate was 65%. The presence of extrahepatic metastases were associated with a decreased time to local recurrence (p < 0.01) and worse overall survival (p = 0.02).

CONCLUSIONS

This study has demonstrated that liver resection for breast cancer-related liver metastases is feasible, safe and associated with prolonged disease free and overall survival in selected patients. It is likely that this option will be offered to more patients going forward, however, the difficulty lies in selecting out those who will benefit from liver resection particularly given the increasing number of systemic treatments and local ablative methods available that offer good long-term results.

A method of separating extracellular vesicles from blood shows potential clinical translation, and reveals extracellular vesicle cargo gremlin-1 as a diagnostic biomarker

Extracellular vesicles (EVs) have potential as minimally invasive biomarkers. However, the methods most commonly used for EV retrieval rely on ultracentrifugation, are time-consuming, and unrealistic to translate to standard-of-care. We sought a method suitable for EV separation from blood that could be used in patient care. Sera from breast cancer patients and age-matched controls (n = 27 patients; n = 36 controls) were analysed to compare 6 proposed EV separation methods. The EVs were then characterised on 8 parameters. The selected method was subsequently applied to independent cohorts of sera (n = 20 patients; n = 20 controls), as proof-of-principle, investigating EVs' gremlin-1 cargo. Three independent runs with each method were very reproducible, within each given method. All isolates contained EVs, although they varied in quantity and purity. Methods that require ultracentrifugation were not superior for low volumes of sera typically available in routine standard-of-care. A CD63/CD81/CD9-coated immunobead-based method was most suitable based on EV markers' detection and minimal albumin and lipoprotein contamination. Applying this method to independent sera cohorts, EVs and their gremlin-1 cargo were at significantly higher amounts for breast cancer patients compared to controls. In conclusion, CD63/CD81/CD9-coated immunobeads may enable clinical utility of blood-based EVs as biomarkers.

Myxoedema coma caused by immunotherapy-related thyroiditis and enteritis

SUMMARY

Thyroid dysfunction is among the most common immune-related adverse reactions associated with immune checkpoint inhibitors. It most commonly manifests as painless thyroiditis followed by permanent hypothyroidism. This usually causes mild toxicity that does not interfere with oncological treatment. In rare instances, however, a life-threatening form of decompensated hypothyroidism called myxoedema coma may develop. We present a case of myxoedema coma in a woman in her sixties who was treated with a combination of CTLA-4 and PD-1 immune checkpoint inhibitors; for stage four malignant melanoma. She became hypothyroid and required thyroxine replacement after an episode of painless thyroiditis. Six months after the initial diagnosis of malignant melanoma, she presented to the emergency department with abdominal pain, profuse diarrhoea, lethargy and confusion. She was drowsy, hypotensive with a BP of 60/40 mmHg, hyponatraemic and hypoglycaemic. Thyroid function tests (TFTs) indicated profound hypothyroidism with a TSH of 19 mIU/L, and undetectable fT3 and fT4, despite the patient being compliant with thyroxine. She was diagnosed with a myxoedema coma caused by immune-related enteritis and subsequent thyroxine malabsorption. The patient was treated with i.v. triiodothyronine (T3) and methylprednisolone in the ICU. While her clinical status improved with T3 replacement, her enteritis was refractory to steroid therapy. A thyroxine absorption test confirmed persistent malabsorption. Attempts to revert to oral thyroxine were unsuccessful. Unfortunately, the patient's malignant melanoma progressed significantly and she passed away four months later. This is the first reported case of myxoedema coma that resulted from two distinct immune-related adverse reactions, namely painless thyroiditis and enterocolitis.

LEARNING POINTS

Myxoedema coma, a severe form of decompensated hypothyroidism is a rare immunotherapy-related endocrinopathy. Myxedema coma should be treated with either i.v. triiodothyronine (T3) or i.v. thyroxine (T4). Intravenous glucocorticoids should be co-administered with thyroid hormone replacement to avoid precipitating an adrenal crisis. Thyroid function tests (TFTs) should be monitored closely in individuals with hypothyroidism and diarrhoea due to the risk of thyroxine malabsorption. A thyroxine absorption test can be used to confirm thyroxine malabsorption in individuals with persistent hypothyroidism.

Trastuzumab for early-stage, HER2-positive breast cancer: a meta-analysis of 13 864 women in seven randomised trials

BACKGROUND

Trastuzumab targets the extracellular domain of the HER2 protein. Adding trastuzumab to chemotherapy for patients with early-stage, HER2-positive breast cancer reduces the risk of recurrence and death, but is associated with cardiac toxicity. We investigated the long-term benefits and risks of adjuvant trastuzumab on breast cancer recurrence and cause-specific mortality.

METHODS

We did a collaborative meta-analysis of individual patient data from randomised trials assessing chemotherapy plus trastuzumab versus the same chemotherapy alone. Randomised trials that enrolled women with node-negative or node-positive, operable breast cancer were included. We collected individual patient-level data on baseline characteristics, dates and sites of first distant breast cancer recurrence and any previous local recurrence or second primary cancer, and the date and underlying cause of death. Primary outcomes were breast cancer recurrence, breast cancer mortality, death without recurrence, and all-cause mortality. Standard intention-to-treat log-rank analyses, stratified by age, nodal status, oestrogen receptor (ER) status, and trial yielded first-event rate ratios (RRs).

FINDINGS

Seven randomised trials met the inclusion criteria, and included 13 864 patients enrolled between February, 2000, and December, 2005. Mean scheduled treatment duration was 14·4 months and median follow-up was 10·7 years (IQR 9·5 to 11·9). The risks of breast cancer recurrence (RR 0·66, 95% CI 0·62 to 0·71; p<0·0001) and death from breast cancer (0·67, 0·61 to 0·73; p<0·0001) were lower with trastuzumab plus chemotherapy than with chemotherapy alone. Absolute 10-year recurrence risk was reduced by 9·0% (95% CI 7·4 to 10·7; p<0·0001) and 10-year breast cancer mortality was reduced by 6·4% (4·9 to 7·8; p<0·0001), with a 6·5% reduction (5·0 to 8·0; p<0·0001) in all-cause mortality, and no increase in death without recurrence (0·4%, -0·3 to 1·1; p=0·35). The proportional reduction in recurrence was largest in years 0-1 after randomisation (0·53, 99% CI 0·46 to 0·61), with benefits persisting through years 2-4 (0·73, 0·62 to 0·85) and 5-9 (0·80, 0·64 to 1·01), and little follow-up beyond year 10. Proportional recurrence reductions were similar irrespective of recorded patient and tumour characteristics, including ER status. The more high risk the tumour, the larger the absolute reductions in 5-year recurrence (eg, 5·7% [95% CI 3·1 to 8·3], 6·8% [4·7 to 9·0], and 10·7% [7·7 to 13·6] in N0, N1-3, and N4+ disease).

INTERPRETATION

Adding trastuzumab to chemotherapy for early-stage, HER2-positive breast cancer reduces recurrence of, and mortality from, breast cancer by a third, with worthwhile proportional reductions irrespective of recorded patient and tumour characteristics.

FUNDING

Cancer Research UK, UK Medical Research Council.