SAMHD1 expression is a surrogate marker of immune infiltration and determines prognosis after neoadjuvant chemotherapy in early breast cancer

PURPOSE

The lack of validated surrogate biomarkers is still an unmet clinical need in the management of early breast cancer cases that do not achieve complete pathological response after neoadjuvant chemotherapy (NACT). Here, we describe and validate the use of SAMHD1 expression as a prognostic biomarker in residual disease in vivo and in vitro.

METHODS

SAMHD1 expression was evaluated in a clinical cohort of early breast cancer patients with stage II-III treated with NACT. Heterotypic 3D cultures including tumor and immune cells were used to investigate the molecular mechanisms responsible of SAMHD1 depletion through whole transcriptomic profiling, immune infiltration capacity and subsequent delineation of dysregulated immune signaling pathways.

RESULTS

SAMHD1 expression was associated to increased risk of recurrence and higher Ki67 levels in post-NACT tumor biopsies of breast cancer patients with residual disease. Survival analysis showed that SAMHD1-expressing tumors presented shorter time-to-progression and overall survival than SAMHD1 negative cases, suggesting that SAMHD1 expression is a relevant prognostic factor in breast cancer. Whole-transcriptomic profiling of SAMHD1-depleted tumors identified downregulation of IL-12 signaling pathway as the molecular mechanism determining breast cancer prognosis. The reduced interleukin signaling upon SAMHD1 depletion induced changes in immune cell infiltration capacity in 3D heterotypic in vitro culture models, confirming the role of the SAMHD1 as a regulator of breast cancer prognosis through the induction of changes in immune response and tumor microenvironment.

CONCLUSION

SAMHD1 expression is a novel prognostic biomarker in early breast cancer that impacts immune-mediated signaling and differentially regulates inflammatory intra-tumoral response.

Is oligoprogression a potentially curable disease in epidermal growth factor receptor mutant lung adenocarcinoma?

Third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) have shown impressive results in EGFR mutant lung cancer (LC) patients in terms of disease control rate with a positive impact on overall survival. Nevertheless, after months of treatment with targeted therapy, progression inevitably occurs. Some patients develop oligoprogression and local treatment is required for optimal disease control while maintaining EGFR-TKIs. This work features a clinical case of a patient harboring an EGFR mutant LC undergoing oligoprogression to EGFR-TKIs, first into the brain and afterward to the primary tumor, requiring local ablative strategies, including primary tumor resection three years after the start of osimertinib. Currently, the patient is still alive and continues with a complete response upon EGFR-TKIs maintenance. Hence, oligoprogression, even in driven oncogenic tumors, represents a distinct biological entity and potential curative disease that deserves particular consideration in multidisciplinary tumor boards. In this case, tumor primary resection after three years of the initial diagnosis represents a paradigm shift in the treatment of EGFR mutant patients.

Prognostic Role of Neutrophil, Monocyte and Platelet to Lymphocyte Ratios in Advanced Ovarian Cancer According to the Time of Debulking Surgery

Despite a multimodal radical treatment, mortality of advanced epithelial ovarian cancer (AEOC) remains high. Host-related factors, such as systemic inflammatory response and its interplay with the immune system, remain underexplored. We hypothesized that the prognostic impact of this response could vary between patients undergoing primary debulking surgery (PDS) and those undergoing interval debulking surgery (IDS). Therefore, we evaluated the outcomes of two surgical groups of newly diagnosed AEOC patients according to the neutrophil, monocyte and platelet to lymphocyte ratios (NLR, MLR, PLR), taking median ratio values as cutoffs. In the PDS group (n = 61), low NLR and PLR subgroups showed significantly better overall survival (not reached (NR) vs. 72.7 months, 95% confidence interval [CI]: 40.9-95.2, p = 0.019; and NR vs. 56.1 months, 95% CI: 40.9-95.2, p = 0.004, respectively) than those with high values. Similar results were observed in progression free survival. NLR and PLR-high values resulted in negative prognostic factors, adjusting for residual disease, BRCA1/2 status and stage (HR 2.48, 95% CI: 1.03-5.99, p = 0.043, and HR 2.91, 95% CI: 1.11-7.64, p = 0.03, respectively). In the IDS group (n = 85), ratios were not significant prognostic factors. We conclude that NLR and PLR may have prognostic value in the PDS setting, but none in IDS, suggesting that time of surgery can modulate the prognostic impact of baseline complete blood count (CBC).

Abstract OT3-11-02: SOLTI-1910: Predicting olaparib sensitivity in patients with unresectable locally advanced/metastatic HER2-negative breast cancer with BRCA1/2, PALB2, RAD51C/D mutations or HRD by the RAD51 test: RADIOLA TRIAL

Background The OlympiAD trial evaluated the PARP inhibitor (PARPi) olaparib versus a non-platinum standard chemotherapy in HER2-negative metastatic breast cancer (MBC) patients with a germline BRCA1/2 (gBRCA) mutation. Olaparib resulted in improved progression-free survival (PFS) and doubled the response rate vs chemotherapy. Nevertheless, the response rate to PARPi is 60% in the gBRCA1/2 population with MBC (current approval), suggesting a limited positive predictive value of gBRCA1/2 status. Moreover, patients with other relevant Homologous Recombination Repair defects (HRD) such as PALB2 or RAD51C/D mutation carriers, or HRD epigenetic silencing, are not captured with a gBRCA analysis. We have previoulsy shown that the functional HRD biomarker RAD51, tested in FFPE tumor samples using an optimized immunofluorescence-based assay, is associated with platinum response in early TNBC and PARPi response in preclinical BC models. We hypothesize that the RAD51 test would help to expand the clinical benefit of PARPi by predicting response to olaparib in MBC with germline/somatic BRCA1/2, PALB2 or RAD51C/D mutation and beyond. Study design RADIOLA is an open-label, single-arm, multicentre phase II study evaluating treatment with olaparib in male or female ≥18 years patients with HER2-negative MBC with ≤ two prior chemotherapy lines in two cohorts: cohort 1 (N=41) with known germline/somatic BRCA1/2, PALB2 or RAD51C/D mutation; cohort 2 (N=25) with functional HRD, namely RAD51-low score (≤10%), in wild-type/unknown mutation status at study entry. All patients will receive olaparib 300mg po BID until progression or unacceptable toxicity. Primary objective will assess, in terms of overall response rate (ORR), the capacity of the RAD51 score to predict olaparib efficacy in cohort 1. Secondary objectives include PFS, clinical benefit rate, duration of response, safety in both cohorts and ORR in cohort 2. Recruitment Recruitment (11 sites) started in March 2022. As of July 2022, 7 patients have been enrolled in Spain. Funding This study is financially supported by AstraZeneca.

Citation Format: Judith Balmaña, Tomás Pascual, Alba Llop-Guevara, Pablo Tolosa, Isabel Blancas, Maria-Eva Perez-Lopez, Barbara Adamo, Iris Teruel, Jose Ponce, Marta Gonzalez, Gemma Viñas, Laura Lema, Francisco Javier Salvador, Mª Teresa Martinez, Alejandra Espinosa, Aleix Prat, Violeta Serra. SOLTI-1910: Predicting olaparib sensitivity in patients with unresectable locally advanced/metastatic HER2-negative breast cancer with BRCA1/2, PALB2, RAD51C/D mutations or HRD by the RAD51 test: RADIOLA TRIAL [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 OT3-11-02.

SAMHD1 expression modulates innate immune activation and correlates with ovarian cancer prognosis

Purpose

SAMHD1 is a deoxynucleotide triphosphate (dNTP) triphosphohydrolase which has been proposed as a putative prognostic factor in haematological cancers and certain solid tumours, although with controversial data. Here, we evaluate SAMHD1 function in ovarian cancer, both in vitro and in ovarian cancer patients.

Methods

SAMHD1 expression was downregulated in ovarian cancer cell lines OVCAR3 and SKOV3 by RNA interference. Gene and protein expression changes in immune signalling pathways were assessed. SAMHD1 expression in ovarian cancer patients was evaluated by immunohistochemistry and survival analysis was performed according to SAMHD1 expression.

Results

SAMHD1 knockdown induced a significant upregulation of proinflammatory cytokines concomitant to increased expression of the main RNA-sensors, MDA5 and RIG-I, and interferon-stimulated genes, supporting the idea that the absence of SAMHD1 promotes innate immune activation in vitro. To assess the contribution of SAMHD1 in ovarian cancer patients, tumours were stratified in SAMHD1-low and SAMHD1-high expressing tumours, resulting in significantly shorter progression free survival (PFS) and overall survival (OS) in SAMHD1-high expression subgroup (p=0.01 and 0.04, respectively).

Conclusions

SAMHD1 depletion correlates with increased innate immune cell signalling in ovarian cancer cells. In clinical samples, SAMHD1-low expressing tumors showed increased progression free survival and overall survival irrespective of BRCA mutation status. These results point towards SAMHD1 modulation as a new therapeutic strategy, able to enhance innate immune activation directly in tumour cells, leading to improved prognosis in ovarian cancer.

Prognostic factors in sinonasal cancers: A multicenter pooled analysis

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Background: Sinonasal cancers (SC) are heterogeneous diseases. Despite multimodality treatment, overall survival (OS) remains unsatisfactory. We aimed to identify prognostic factors (PFs) associated with patterns of failure and OS in non-metastatic SC (nmSC). Methods: We retrospectively reviewed a pooled dataset of nmSC from Princess Margaret (Canada) and Catalan Institute of Oncology (Spain) treated with definitive surgery ± postop radiotherapy (RT) or RT ± chemo according to institutional protocols between 2010-2019. In squamous cell carcinoma (SCC), HPV status was tested by p16 staining, and HPV DNA (ISH or PCR) if equivocal. The primary goal was to assess the association of tumor histology, stage (by 7th edition TNM), and other clinicopathological variables on locoregional control (LRC), distant control (DC) and OS. Actuarial rates were calculated with Kaplan–Meier (KM) method. Multivariable analysis (MVA) calculated hazard ratios (aHR) adjusted for histology type, T-/N-categories, and primary treatment. Results: Out of 342 pts, median age was 62 years (y) (range 21-96), Male:Female = 212:130, 95% had ECOG 0-1. Tumor histology types were: 192 (56%) SCC (p16+: 35; p16-/untested: 157), 40 (12%) adenocarcinoma (AD), 33 (10%) sinonasal undifferentiated carcinoma or sinonasal neuroendocrine tumors (SNUC/SNEC), 28 (8%) malignant melanoma (MM), 27 (8%) esthesioneuroblastoma (ES) and 22 (6%) adenoid cystic carcinoma (ACC). Median follow up was 3.6 y (range 0.1-11.3). Three-year actuarial rates for each endpoint are included in table. The PFs for LRC by MVA were: SNUC/SNEC (vs SCC) histology, T3-4 (vs T1-2: aHR 2.4, p = < 0.01) and N+ (vs N-: aHR 1.7, p = 0.02) diseases. The PFs for DC were: MM (vs SCC) and SNUC/SNEC (vs SCC) histology, and T3-4 (vs T1-2: aHR 6.0, p = 0.01) disease. The PFs for OS were: MM (vs SCC) histology, older age (aHR 1.0, p < 0.01), T3-4 (vs T1-2: aHR 5.6, p < 0.01), and N+ (vs N-: aHR 2.5, p < 0.01) disease. There was no difference in primary surgery vs RT in any outcome endpoint (all p > 0.05). p16+ SCC had a marginally higher LRC but similar DC and OS vs p16-/untested SCC (table). Conclusions: This large multicentre cohort of nmSC shows different patterns of relapse and survival with different tumor histologies. Our results suggest that individualization of treatment and follow-up strategies by histologic type is recommended to optimize outcomes in these orphan diseases. [Table: see text]

Abstract PD4-06: Trastuzumab deruxtecan in patients with HER2[+] or HER2-low-expressing advanced breast cancer and central nervous system involvement: Preliminary results from the DEBBRAH phase 2 study

Background: Approximately 30% to 40% of patients (pts) with HER2[+] advanced breast cancer (ABC) will develop brain metastases (BM) during the course of their disease. Trastuzumab deruxtecan (T-DXd; DS-8201) is an antibody-drug conjugate containing an anti-HER2 antibody, a cleavable tetrapeptide-based linker, and a topoisomerase I inhibitor payload. In the phase 2 DESTINY-Breast01 trial, T-DXd showed efficacy in the subgroup of HER2[+] ABC pts with stable BM at baseline. DEBBRAH is assessing the efficacy and safety of T-DXd in HER2[+] and HER2-low-expressing ABC pts with a history of BM and/or leptomeningeal carcinomatosis (LMC). Here, we report primary results from cohorts A and C. Methods: This is an ongoing, multicenter, open-label, 5-cohort, non-comparative, phase 2 study across 18 hospitals in 2 countries. A total of 39 pts aged ≥18 years with pretreated HER2[+] or HER2-low-expressing ABC with stable, progressing, or untreated BM and/or LMC are being enrolled in 5 cohorts: (A) HER2[+] ABC with non-progressing BM after radiotherapy and/or surgery; (B) HER2[+] or HER2-low-expressing ABC with asymptomatic untreated BM; (C) HER2[+] ABC with progressing BM after local treatment; (D) HER2-low-expressing ABC with progressing BM after local treatment; (E) HER2[+] or HER2-low-expressing ABC with LMC. In cohorts A and C, pts must have received prior taxane and ≥1 HER2-targeted therapy for ABC. Pts received 5.4 mg/kg T-DXd intravenously on day 1 of a 21-day cycle until disease progression, unacceptable toxicity, or consent withdrawal. The primary endpoint for cohort A is 16-week progression-free survival (PFS) per local assessment using RANO-BM for central nervous system (CNS) lesions and RECIST v.1.1 for extracranial lesions (H0: 5%); for cohort C, CNS overall response rate (ORR; H0: 10%). A single-arm binomial design is used for cohorts A and C. A futility interim analysis has been planned in cohort A after accrual of 4 pts. Sample size was planned to attain an 80% power at nominal level of one-sided α of 0.05 in each cohort. Results: Between Jun 29, 2020, and Feb 18, 2021, 26 pts were allocated in the study. Enrollment is complete in cohorts A (n=8 pts) and C (n=9 pts), and ongoing in the remaining cohorts. At data cutoff (May 21, 2021), median follow-up for the cohort A was 5.5 months (IQR 4.4-6.9) and 6.2 months (IQR 5.1-6.4) for the cohort C. In the cohort A, 6 (75.0%) of 8 pts were alive without disease progression at 16 weeks, reaching the primary endpoint (p&lt;0.01). In the cohort C, the CNS ORR was 55.6% (5 pts with partial response), also meeting the primary endpoint (p&lt;0.01). At the time of this analysis, 75.0% of pts of the cohort A and 55.6% of the cohort C remained on therapy. The most frequent adverse events of any grade in 26 pts who received at least 1 dose of T-DXd were fatigue (11 [42.3%]; 3.8% of grade 3), nausea (10 [38.5%]), a decreased neutrophil count (9 [34.6%]; 11.5% of grade 3), and anemia (6 [23.1%]). Treatment-related serious adverse events occurred in 1 (3.8%) of 26 pts due to grade 1 pneumonitis. No treatment-related deaths were reported. Conclusions: T-DXd demonstrated preliminary efficacy with manageable toxicity in pretreated pts with HER2[+] ABC with stable and progressing BM after local treatment. Further investigation is required in larger cohorts to validate these findings. The assessment of the T-DXd antitumor activity in cohorts B, D, and E is currently ongoing.

Citation Format: Marta Vaz Batista, Patricia Cortez, Manuel Ruiz, Juan Miguel Cejalvo, Juan de la Haba, Laia Garrigós, Fabricio Racca, Sonia Servitja, Salvador Blanch, Iris Teruel, José Manuel Pérez-García, María Gion, Monica Nave, Antonio Llombart-Cussac, Miguel Sampayo-Cordero, Andrea Malfettone, Javier Cortes, Sofia Braga. Trastuzumab deruxtecan in patients with HER2[+] or HER2-low-expressing advanced breast cancer and central nervous system involvement: Preliminary results from the DEBBRAH phase 2 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 PD4-06.

New Drugs, Old Toxicities: Pneumonitis Related to Palbociclib - A Case Report

Background

Palbociclib is a specific inhibitor of cyclin-dependent kinases 4 and 6 that is approved for the treatment of advanced or metastatic breast cancer patients. Despite a good toxicity profile in pivotal trials, where asymptomatic neutropenia was the main adverse effect, its wider use in clinical practice may show less prevalent but serious toxicities.

Case Presentation

Here, we describe a case of pneumonitis due to palbocicblib. A 57-year-old female with breast cancer with bone metastasis presented dyspnea at rest 3 months after beginning treatment with palbociclib and letrozole. Palbociclib-induced pneumonitis was considered the most probable cause after ruling out all alternatives, and the patient was successfully treated with steroids and showed complete remission.

Conclusions

In summary, we present a well-documented case report of pneumonitis related to palbociclib. However, the mechanism of toxicity is still unknown, and there are as yet no reliable biomarkers to predict toxicity with cyclin-dependent kinase 4/6 inhibitors. In this case report, we alert physicians about new drugs that can provoke old toxicities.

Abstract P2-12-05: Neuropsychological assessment, neuroimaging, and tumor markers to explore cognitive decline in early stage breast cancer patients

Background. It is widely demonstrated that a high percentage of early stage breast cancer patients achieves a long-term survival. However, it seems that some of them show a cognitive decline during and after the oncology treatment, affecting their quality of life. Fortunately, the neuropsychological impairment in cancer patients is nowadays a known issue in oncology literature. Our aim is to assess the effects of chemotherapy and endocrine therapy on neurocognitive functions in patients with early stage breast cancer. If the hypothesis that the patients suffer from neurocognitive impairments related to the oncology treatment will be confirmed, this would imply the possibility of an early neuropsychological rehabilitation since the first diagnosis, to prevent the worsening of the quality of life and to avoid the use of additional medications to regulate for example the severity of fatigue and mood. Methods. The study population includes 45 patients diagnosed of breast cancer undergoing chemotherapy +/- endocrine treatment (CT), 15 patients undergoing endocrine treatment (HT), and 9 healthy controls (HC). Throughout each evaluation at three points time, we administered the Mini-Mental State Examination (MMSE), some tests of the Cogstateneurocognitive battery, the Trail Making Test (TMTA and TMTB), and the Controlled Oral Word Association Test (COWAT). Moreover, each subject was asked to complete the EORTC QLQ-C30 and the QLQ-BR23 quality of life tests, the MD Anderson Symptoms Inventory questionnaire, the Hospital Anxiety and Depression scale, and a self-report of the neurocognitive impairment perceived. In addition, we are performing a pilot neuroimaging study aimed to enroll 20 patients with early stage breast cancer, of whom 10 treated with chemotherapy, and 10 with hormone therapy alone. Patients undergo a structural and functional brain magnetic resonance imaging (fMRI). S100 protein, and neuro specific enolase are also collected to explore their possible relationship with the neurocognitive decline. Results. Both CT and HT Groups performed lower results than HC in visuo-motor processing speed test (TMTA) at baseline and at month 12 (p=0.00). At month 6 only the HT Group had lower results than HC (p=0.00). We found a correlation between the lower results of TMTA and the level of depression (p=0.02), distress (p=0.00), anxiety (p=0.01), severity of symptoms (p=0.00) in CT Group at baseline. The MMSE scores were slightly lower in both CT and HT Groups compared to HC (p=0.04) at month 6. The MMSE results at month 12 were lower in HT Groups compared to HC (p=0.04). In addition, the neurocognitive impairment perceived is higher in CT Group (p&lt;0.00) once having stopped the chemotherapy treatment until the last follow up. The results of TMTB and COWAT increased in CT Group during the last follow up (p=0.00), and it seems to have a positive correlation with the neurocognitive tasks the patients performed (p=0.02 and p=0.03 respectively). Concerning the pilot study, we analysed the first 10 patients enrolled in the study: 5 subjects treated with chemotherapy and 5 with hormone therapy alone. No statistically significant differences were found concerning the alteration of the tumor markers values. On the contrary, we found changes between the baseline and the post-treatment brain fMRI. Conclusions. Our results suggest a decline in few cognitive domains in cancer patients as consequence of the oncology treatment. In some tests the neurocognitive decline was also observed in cancer groups at baseline, and it was associated with the low state of mind in CT Group. We infer that the increasing of scores in CT Group at month 12 was positively associated with the cognitive tasks the patients were performing during the study-period.

Citation Format: Claudia Panciroli, Carles Biarnes, Josep Puig, Jose Anton Anton, Vanesa Quiroga, Eudald Felip, Beatriz Cirauqui, Margarita Romeo, Iris Teruel, Salvador Pedraza, Mireia Margeli. Neuropsychological assessment, neuroimaging, and tumor markers to explore cognitive decline in early stage breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-12-05.

Abstract P3-08-32: Predictive value of SAMHD1 expression in early relapse breast cancer

Introduction: SAMHD1 is a triphosphohydrolase that catalyzes the degradation of deoxynucleoside triphosphates (dNTP). SAMHD1 expression and function are coordinated during the cell cycle and tightly linked to cell cycle progression and proliferation. SAMHD1 affects nucleotide and antimetabolite drug susceptibility and has been identified as a biomarker of cytarabine treatment in acute myeloid leukemia (AML)1.Here, we explore the potential impact of SAMHD1 expression in breast cancer (BC) outcome, and its role as a modulator of response to antimetabolites. Material and methods: We evaluated the effect of SAMHD1 function on the efficacy of a wide range of nucleotide analogues used in cancer therapy, using established cell lines modified to express or not SAMHD1 and primary cells where SAMHD1 expression was modulated by Vpx-mediated degradation. We performed tissue microarray of tumor tissue from metastatic (M) BC patients (P) treated with capecitabine, and evaluated SAMHD1 status using inmunohistochemistry (anti-SAMHD1 polyclonal antibody 12586-1-AP, Proteintech). SAMHD1 positivity was defined as cellular positivity ≥25%. Statistical analysis was performed using Chi-square test for qualitative covariables, Kaplan-Meier survival curves and log Rank function, considering a p &lt; 0.05 as statistically significant.Results: In vitro, SAMHD1 effectively modified the efficacy of all nucleotide analogues tested. Interestingly, SAMHD1 could either enhance (gemcitabine, capecitabine, fluorouracil and floxuridine) or inhibit (Ara-C, fludarabine, cladribine, clofarabine and nelaravine) potency of nucleotide analogues, an effect that was not dependent on the specific nucleotide targeted. In our cohort of 30 BCP, the median age was 52 years, 63% were classified as luminal according to hormone receptor (HR) and epidermal growth factor receptor-2 (HER2) status, 10% were HER2 positive and 27% as triple negative. 33.3% p presented as de novo metastatic disease, 36.7% presented m disease with a disease free interval (DFI) ≤ 5 years and 30% presented m disease with a DFI &gt;5 years. P were treated with capecitabine as first line therapy in 33.3% of cases, second in 33.3%, third in 13.3%, four in 10%, and fifth in 10%. 33% of P presented response to capecitabine, 40% presented stabilization of disease, and 27% progressed. Median time to progresion to capecitabine was 12.5 months, and median overal survival was 26.6 months. SAMHD1 expression was positive in 63.3% (n: 19) of p and negative in 33.3% (n: 10) of p. SAMHD1 positivity was significantly enriched in cases with de novo disease, and DFI ≤ 5 years (Chi-Square test; p=0.022). According to survival analysis, SAMHD1 positivity was associated with DFI ≤ 5 years (Log Rank; p=0.047). SAMHD1 was not associated with clinical characteristiques or inmunohistochemical subtypes.SAMHD1 positivity was associated with better response to capecitabine and less grade 3/4 toxicity, although these differences did not reach statistical significance. These results were in line with the evaluation of susceptibility to capecitabine in cell culture. Conclussion: SAMHD1 modifies the efficacy of a wide variety of nucleoside analogues used to treat cancer. In vivo, SAMHD1 expression is a predictor of early relapse in BCP independently of the subtype. Moreover, it could be a potential predictive factor of capecitabine efficacy in MBCP. Thus, modulation of SAMHD1 function may constitute a promising target for the improvement of multiple therapies.

1. Rassidakis GZ, Herold N, Myrberg IH et al. Low-level expression of SAMHD1 in acute myeloid leukemia (AML) blasts correlates with improved outcome upon consolidation chemotherapy with high-dose cytarabine-based regimens. Blood Cancer J. 2018 Oct 19;8(11):98.

Citation Format: Mireia Margeli, Eudald Felip, Maica Gomez, Pedro Fernandez, Laia Pérez-Roca, Eva Riveira-Muñoz, Anna Martinez-Cardús, Iris Teruel, Margarita Romeu, Beatriz Cirauqui, Vanesa Quiroga, José A. Este, Ester Ballana. Predictive value of SAMHD1 expression in early relapse breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-32.

Abstract P5-05-14: Cyclin-dependent kinases inhibitors improve antimetabolite drug potency depending on SAMHD1 expression

Introduction Cyclin-dependent kinase (CDK) 4/6 inhibitors represent a new paradigm in the treatment of hormone receptor (HR) positive and HER-2 negative metastatic breast cancer (MBC). However, despite their evident clinical benefit, the cellular and molecular mechanisms underlying treatment efficacy and drug failure are still largely unknown. CDK4/6 inhibitors block the cyclin D1-CDK4/6 interaction, leading to inhibition of cell cycle progression through the G1/S phase and inhibiting cell proliferation. SAMHD1 is a dNTPase that maintains the intracellular dNTP pool at levels adequate for DNA replication and repair. SAMHD1 function is regulated by phosphorylation, a process controlled by CDKs. Moreover, SAMHD1 has also been shown to modify the efficacy of different nucleotide analogues. Here, we aim to evaluate the capacity of selective CDK4/6 inhibitors to modify the efficacy of different antimetabolites currently used for cancer treatment. Material and methods: Cytotoxic activity of 5-fluorouracil, its prodrug capecitabine and the anti-folate pemetrexed was evaluated alone or in combination with the CDK4/6 inhibitor palbociclib in breast cancer cell lines (T47D and MDA-MB-468) and primary cells expressing or not SAMHD1 through HIV-2 Vpx mediated degradation. Cytotoxicity was measured either by colorimetric tetrazolium dye MTT method or flow cytometry. Drug combinations were evaluated by calculating the combination index (CI) through the ixobologram equation, considering a synergic drug combination a CI &lt;1. Intracellular dNTP content was determined using a polymerase- based method. Expression of relevant genes was measured by qPCR mRNA detection. SAMHD1 expression and phosphorylation were measured by Western blot. Results Analysis of cell cycle profile and protein expression of drug-treated cells confirmed that CDK4/6 control SAMHD1 phosphorylation and decrease intracellular dNTPs. CDK4/6 inhibitors palbociclib, ribociclib and abemaciclib blocked SAMHD1 phosphorylation, whereas SAMHD1 protein expression was not affected. In addition, we observed a concomitant dephosphorylation and decreased expression of Rb, the natural substrate of CDK6, and a known marker of CDK4/6 inhibitor activity. In combination, palbociclib enhanced the efficacy of pemetrexed or 5-fluorouracil up to 6-fold, indicating strong synergy (CI=0,0049-0,404). Interestingly, the synergistic effect was lost in cells not expressing SAMHD1. Palbociclib did not change antimetabolite efficacy in the breast cancer MDA-MB-468 cell line. However, Rb and pRb were not detected in MDA-MB-468 cells by mRNA qPCR or Western blot. Conclusion CDK4/6 inhibitors induce the activation of SAMHD1. Taken together, our results suggest that CDK4/6 inhibitor-mediated enhancement of antimetabolite activity is dependent on the regulation of SAMHD1 function. CDK4/6 inhibitors restrict cells in G1 but also prevent SAMHD1 phosphorylation that sensitizes tumoral cells to antimetabolite drugs. Thus, pharmacological modulation of SAMHD1 activity has the potential to improve the efficacy of cancer therapies and paves the way to the identification of malignancies that may be treated with new drug combinations. Combinations with selective CDK4/6 inhibitors plus pemetrexed or capecitabine could be effective in the treatment of cancer after first line drug-failure. SAMHD1 could be a useful biomarker to predict treatment response.

Citation Format: Eudald Felip, Roger Badia, Mireia Margelí, Marc Castellví, Vanesa Quiroga, Iris Teruel, Beatriz Cirauqui, Margarita Romeo, Ifeanyi Jude Ezeonwumelu, Eva Riveira-Muñoz, José Esté, Ester Ballana. Cyclin-dependent kinases inhibitors improve antimetabolite drug potency depending on SAMHD1 expression [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-05-14.

Prognostic value of monocyte to lymphocyte ratio (MLR) in epithelial ovarian cancer (EOC)

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Background: Identifying high-risk early-stage EOC patients (p) is a major issue. Also, controversy about the role of neoadjuvant chemotherapy prior to surgery in advanced EOC is still ongoing. A high MLR is related to poorer outcomes in several cancers, and also in ovarian cancer according to limited retrospective series. We explored the clinical value of MLR in a cohort of EOC p. Methods: We included all EOC p diagnosed in our center, from January 2008 to April 2017, who had undergone radical treatment. Overall survival (OS) was assessed by Kaplan Meyer. Maximally selected rank statistics was used to determine the MLR cut-off value for the greatest OS discrimination. The hazard ratio (HR) of death of MLR was explored by multivariate Cox regression models, adjusted by age at diagnosis, stage I/II versus (vs) III/IV, high grade serous carcinomas (HGSC) vs other, primary surgery vs interval surgery after neoadjuvant chemotherapy (PS, IS), residual disease < 1 vs > 1cm, year of diagnosis, and hemoglobin, neutrophils, platelets and MLR at diagnosis. Results: 124 p were included. Median age at diagnosis was 58.7 years; 55.6% were HGSC;67.7% stage III/IV; 69.3% received PS; 14.3% had residual disease > 1cm. Median OS was 75 months. MLR was the laboratory parameter that more significantly impacted on OS in our model (p = 0.02). Optimal MLR cut-off was 0.38. The MLR > 0.38 group (MLR-hi) had a higher-risk of death (HR = 2.9; 95% IC: 1.3–6.5) with respect to those with MLR < = 0.38 (MLR-lo). Median OS were 100 and 35 months, respectively. In the MLR-lo group, median age at diagnosis was 56.9 years (vs 61.9 in the MLR-hi, p 0.047), 44.8% were HGSC (vs 61.2%, p 0.134), and 49.97% were stages I/II (vs 14.2%, p 0.001). MLR-hi p who had undergone PS or IS had similar OS (p = 0.63). In contrast, among MLR-lo p, PS showed significantly higher OS than IS (p < 0.0001). Conclusions: In our cohort, MLR was an independent prognostic factor in EOC. Its potential role to identify high-risk early-stage p and to predict worse outcomes after PS among advanced-stage p need to be explored in larger cohorts.

Delay in starting radiotherapy due to neoadjuvant therapy does not worsen survival in unresected glioblastoma patients

PURPOSE

We retrospectively examined the potential effect on overall survival (OS) of delaying radiotherapy to administer neoadjuvant therapy in unresected glioblastoma patients.

PATIENTS AND METHODS

We compared OS in 119 patients receiving neoadjuvant therapy followed by standard treatment (NA group) and 96 patients receiving standard treatment without neoadjuvant therapy (NoNA group). The MaxStat package of R identified the optimal cut-off point for waiting time to radiotherapy.

RESULTS

OS was similar in the NA and NoNA groups. Median waiting time to radiotherapy after surgery was 13 weeks for the NA group and 4.2 weeks for the NoNA group. The longest OS was attained by patients who started radiotherapy after 12 weeks and the shortest by patients who started radiotherapy within 4 weeks (12.3 vs 6.6 months) (P = 0.05). OS was 6.6 months for patients who started radiotherapy before the optimal cutoff of 6.43 weeks and 19.1 months for those who started after this time (P = 0.005). Patients who completed radiotherapy had longer OS than those who did not, in all 215 patients and in the NA and NoNA groups (P = 0.000). In several multivariate analyses, completing radiotherapy was a universally favorable prognostic factor, while neoadjuvant therapy was never identified as a negative prognostic factor.

CONCLUSION

In our series of unresected patients receiving neoadjuvant treatment, in spite of the delay in starting radiotherapy, OS was not inferior to that of a similar group of patients with no delay in starting radiotherapy.