HER2-Overexpressing Breast Cancers Amplify FGFR Signaling upon Acquisition of Resistance to Dual Therapeutic Blockade of HER2

Artemisia argyi extracts overcome lapatinib resistance via enhancing TMPRSS2 activation in HER2-positive breast cancer

Breast cancer stands as the predominant malignancy and primary cause of cancer-related mortality among females globally. Approximately 25% of breast cancers exhibit HER2 overexpression, imparting a more aggressive tumor phenotype and correlating with poor prognoses. Patients with metastatic breast cancer receiving HER2 tyrosine kinase inhibitors (HER2 TKIs), such as Lapatinib, develop acquired resistance within a year, posing a critical challenge in managing this disease. Here, we explore the potential of Artemisia argyi, a Chinese herbal medicine known for its anti-cancer properties, in mitigating HER2 TKI resistance in breast cancer. Analysis of the Cancer Genome Atlas (TCGA) revealed diminished expression of transmembrane serine protease 2 (TMPRSS2), a subfamily of membrane proteolytic enzymes, in breast cancer patients, correlating with unfavorable outcomes. Intriguingly, lapatinib-responsive patients exhibited higher TMPRSS2 expression. Our study unveiled that the compounds from Artemisia argyi, eriodictyol, and umbelliferone could inhibit the growth of lapatinib-resistant HER2-positive breast cancer cells. Mechanistically, they suppressed HER2 kinase activation by enhancing TMPRSS2 activity. Our findings propose TMPRSS2 as a critical determinant in lapatinib sensitivity, and Artemisia argyi emerges as a potential agent to overcome lapatinib via activating TMPRSS2 in HER2-positive breast cancer. This study not only unravels the molecular mechanisms driving cell death in HER2-positive breast cancer cells induced by Artemisia argyi but also lays the groundwork for developing novel inhibitors to enhance therapy outcomes.

Emerging targeted therapies and strategies to overcome resistance in biliary tract cancers

In the last decade, targeted therapies have shown rapid advancement in biliary tract cancer (BTC). Today, many targeted agents are available and under investigation for patients with BTC. More recently, immune checkpoint inhibitors (ICI) such as durvalumab and pembrolizumab in combination with gemcitabine plus cisplatin (gem/cis) have resulted in improved overall survival and progression-free survival in the first-line setting. However, the efficacy benefit of these novel therapeutics is often short-lived, with literature outlining concerns about both primary and secondary resistance to these agents. Investigators also need to consider toxicity profiles that can emerge using this strategy. There have been efforts to reduce evolving resistance through combinatory approaches, both pre-clinically and in early clinical settings. This review summarizes the emerging targeted therapies in BTC, evolving biomarkers of resistance, strategies to overcome them, and an analysis of ongoing clinical trials of patients with advanced BTC.

Revolutionizing anti-HER2 therapies for extrahepatic cholangiocarcinoma and gallbladder cancer: Current advancements and future perspectives

Biliary tract cancers (BTCs) encompass a heterogeneous group of rare tumors, including intrahepatic cholangiocarcinoma (iCCA), extrahepatic cholangiocarcinoma (eCCA), gallbladder cancer (GBC) and ampullary cancer (AC). The present first-line palliative treatment regimen comprises gemcitabine and cisplatin in combination with immunotherapy based on two randomized controlled studies. Despite the thorough investigation of these palliative treatments, long-term survival remains low. Moving beyond conventional chemotherapies and immunotherapies, the realm of precision medicine has demonstrated remarkable efficacy in malignancies such as breast and gastric cancers, characterized by notable HER2 overexpression rates. In the context of biliary tract cancer, significant HER2 alterations are observed, particularly within eCCA and GBC, heightening the interest in precision medicine. Various anti-HER2 therapies, including trastuzumab, pertuzumab, trastuzumab-deruxtecan, zanidatamab and neratinib, have undergone investigation. The objective of this review is to summarize the current evidence and outline future directions of targeted HER2 treatment therapy in patients with biliary tract tumors, specially extrahepatic cholangiocarcinoma and gallbladder cancer.

Next-Generation HER2-Targeted Antibody-Drug Conjugates in Breast Cancer

Human epidermal growth factor receptor 2 (HER2) tyrosine kinase is overexpressed in 20% of breast cancers and associated with a less favorable prognosis compared to HER2-negative disease. Patients have traditionally been treated with a combination of chemotherapy and HER2-targeted monoclonal antibodies such as trastuzumab and pertuzumab. The HER2-targeted antibody-drug conjugates (ADCs) trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd) represent a novel class of therapeutics in breast cancer. These drugs augment monoclonal antibodies with a cytotoxic payload, which is attached by a linker, forming the basic structure of an ADC. Novel combinations and sequential approaches are under investigation to overcome resistance to T-DM1 and T-DXd. Furthermore, the landscape of HER2-targeted therapy is rapidly advancing with the development of ADCs designed to attack cancer cells with greater precision and reduced toxicity. This review provides an updated summary of the current state of HER2-targeted ADCs as well as a detailed review of investigational agents on the horizon. Clinical trials are crucial in determining the optimal dosing regimens, understanding resistance mechanisms, and identifying patient populations that would derive the most benefit from these treatments. These novel ADCs are at the forefront of a new era in targeted cancer therapy, holding the potential to improve outcomes for patients with HER2-positive and HER2-Low breast cancer.

HER2 overexpression predicts pathological T2 stage and improved survival in de novo muscle-invasive bladder cancer after immediate radical cystectomy: a retrospective cohort study

INTRODUCTION

Human epidermal growth factor receptor type 2 (HER2) overexpression is a prognostic factor and a therapeutic target for breast cancer; however, anti-HER2 therapies are ineffective in patients with bladder cancer. The authors investigated the effect of HER2 overexpression (HER2 + ) on the prognosis of muscle-invasive bladder cancer (MIBC).

MATERIALS AND METHODS

This retrospective cohort study included patients who underwent initial transurethral resection of bladder tumors between 2005 and 2013 and were registered in the Korea National Health Insurance Database, which provides data on overall survival (OS). Sixty-one patients with clinically nonmetastatic de novo MIBC were included in this study. As a subgroup, 33 patients who underwent immediate radical cystectomy (RC) were analyzed. Univariate and multivariate Cox proportional hazards models were used to identify prognostic factors for survival. A multivariable binary logistic regression model was used to identify the favorable T stage.

RESULTS

Among the 61 patients with d-MIBC, 14 were HER2 + and 47 HER2 - . Age less than 70 years [hazard ratio (HR): 0.312, CI: 0.16-0.59, P <0.001] and HER2 + status (HR: 0.40, CI: 0.19-0.85, P =0.02) were favorable prognostic factors for OS after adjusting for clinical variables. In the RC subgroup, HER2 + status was a significant predictive factor for the pT2 stage (HR): 36.8, CI: 4.83-797.41, P <0.01). Age less than 70 years (HR: 0.15, CI: 0.05-0.42, P <0.001) and HER2 + status (HR: 0.11, CI: 0.02-0.54, P =0.01) were favorable prognostic factors for OS after adjusting for RC pathological variables.

CONCLUSIONS

HER2 + status could be a marker for an indolent subset of MIBC and could predict favorable survival regardless of RC status. Moreover, HER2 + status not only consistently predicted a favorable T stage after RC, but also predicted better survival than pathological outcomes.

Sunitinib in Patients With Breast Cancer With FGFR1 or FGFR2 Amplifications or Mutations: Results From the Targeted Agent and Profiling Utilization Registry Study

PURPOSE

The Targeted Agent and Profiling Utilization Registry Study is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer and genomic alterations known to be drug targets. Results from cohorts of patients with metastatic breast cancer (BC) with FGFR1 and FGFR2 alterations treated with sunitinib are reported.

METHODS

Eligible patients had measurable disease, Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, and no standard treatment options. Simon's two-stage design was used with a primary end point of disease control (DC), defined as objective response (OR) or stable disease of at least 16 weeks duration (SD16+) according to RECIST v1.1. Secondary end points included OR, progression-free survival, overall survival, duration of response, duration of stable disease, and safety.

RESULTS

Forty patients with BC with FGFR1 (N = 30; amplification only n = 26, mutation only n = 1, both n = 3) or FGFR2 (N = 10; amplification only n = 2, mutation only n = 6, both n = 2) alterations were enrolled. Three patients in the FGFR1 cohort were not evaluable for efficacy; all patients in the FGFR2 cohort were evaluable. For the FGFR1 cohort, two patients with partial response and four with SD16+ were observed for DC and OR rates of 27% (90% CI, 13 to 100) and 7% (95% CI, 1 to 24), respectively. The null hypothesis of 15% DC rate was not rejected (P = .169). No patients achieved DC in the FGFR2 cohort (P = 1.00). Thirteen of the 40 total patients across both cohorts had at least one grade 3-4 adverse event or serious adverse event at least possibly related to sunitinib.

CONCLUSION

Sunitinib did not meet prespecified criteria to declare a signal of antitumor activity in patients with BC with either FGFR1 or FGFR2 alterations. Other treatments and clinical trials should be considered for these patient populations.

Targeting HER2 and FGFR-positive cancer cells with a bispecific cytotoxic conjugate combining anti-HER2 Affibody and FGF2

Breast cancer remains a significant global health challenge, necessitating the development of effective targeted therapies. This study aimed to create bispecific targeting molecules against HER2 and FGFR1, two receptors known to play crucial roles in breast cancer progression. By combining the high-affinity Affibody ZHER2:2891 and a modified, stable form of fibroblast growth factor 2 (FGF2), we successfully generated bispecific proteins capable of simultaneously recognizing HER2 and FGFR1. Two variants were designed: AfHER2-sFGF2 with a shorter linker and AfHER2-lFGF2 with a longer linker between the HER2 and FGFR1-recognizing proteins. Both proteins exhibited selective binding to HER2 and FGFR1, with AfHER2-lFGF2 demonstrating simultaneous binding to both receptors. AfHER2-lFGF2 exhibited superior internalization compared to FGF2 in FGFR-positive cells and significantly increased internalization compared to AfHER2 in HER2-positive cells. To enhance their therapeutic potential, highly potent cytotoxic agent MMAE was conjugated to the targeting proteins, resulting in protein-drug conjugates. The bispecific AfHER2-lFGF2-vcMMAE conjugate demonstrated exceptional cytotoxic activity against HER2-positive, FGFR-positive, and dual-positive cancer cell lines that was significantly higher compared to monospecific conjugates. These data indicate the beneficial effect of simultaneous targeting of HER2 and FGFR1 in precise anticancer medicine and contribute valuable insights into the design and potential of bispecific targeting molecules for breast cancer treatment.

Chemotherapeutic Activity of Imidazolium-Supported Pd(II) o-Vanillylidene Diaminocyclohexane Complexes Immobilized in Nanolipid as Inhibitors for HER2/neu and FGFR2/FGF2 Axis Overexpression in Breast Cancer Cells

Two bis-(imidazolium-vanillylidene)-(R,R)-diaminocyclohexane ligands (H2(VAN)2dach, H2L1,2) and their Pd(II) complexes (PdL1 and PdL2) were successfully synthesized and structurally characterized using microanalytical and spectral methods. Subsequently, to target the development of new effective and safe anti-breast cancer chemotherapeutic agents, these complexes were encapsulated by lipid nanoparticles (LNPs) to formulate (PdL1LNP and PdL2LNP), which are physicochemically and morphologically characterized. PdL1LNP and PdL2LNP significantly cause DNA fragmentation in MCF-7 cells, while trastuzumab has a 10% damaging activity. Additionally, the encapsulated Pd1,2LNPs complexes activated the apoptotic mechanisms through the upregulated P53 with p < 0.001 and p < 0.05, respectively. The apoptotic activity may be triggered through the activity mechanism of the Pd1,2LNPs in the inhibitory actions against the FGFR2/FGF2 axis on the gene level with p < 0.001 and the Her2/neu with p < 0.05 and p < 0.01. All these aspects have triggered the activity of the PdL1LNP and PdL2LNP to downregulate TGFβ1 by p < 0.01 for both complexes. In conclusion, LNP-encapsulated Pd(II) complexes can be employed as anti-cancer drugs with additional benefits in regulating the signal mechanisms of the apoptotic mechanisms among breast cancer cells with chemotherapeutic-safe actions.

FGFR2 genetic variants in women with breast cancer

Black African populations are more genetically diverse than others, but genetic variants have been studied primarily in European populations. The present study examined the association of four single nucleotide polymorphisms (SNPs) of the fibroblast growth factor receptor 2, associated with breast cancer in non‑African populations, with breast cancer in Black, southern African women. Genomic DNA was extracted from whole blood samples of 1,001 patients with breast cancer and 1,006 controls (without breast cancer), and the rs2981582, rs35054928, rs2981578, and rs11200014 polymorphisms were analyzed using allele‑specific Kompetitive allele‑specific PCR™, and the χ2 or Fisher's exact tests were used to compare the genotype frequencies. There was no association between those SNPs and breast cancer in the studied cohort, although an association was identified between the C/C homozygote genotype for rs2981578 and invasive lobular carcinoma. These results show that genetic biomarkers of breast cancer risk in European populations are not necessarily associated with risk in sub‑Saharan African populations. African populations are more heterogenous than other populations, and the information from this population can help focus genetic risks of cancer in this understudied population.

AXL - a new player in resistance to HER2 blockade

HER2 is a driver in solid tumors, mainly breast, oesophageal and gastric cancer, through activation of oncogenic signaling pathways such as PI3K or MAPK. HER2 overexpression associates with aggressive disease and poor prognosis. Despite targeted anti-HER2 therapy has improved outcomes and is the current standard of care, resistance emerge in some patients, requiring additional therapeutic strategies. Several mechanisms, including the upregulation of receptors tyrosine kinases such as AXL, are involved in resistance. AXL signaling leads to cancer cell proliferation, survival, migration, invasion and angiogenesis and correlates with poor prognosis. In addition, AXL overexpression accompanied by a mesenchymal phenotype result in resistance to chemotherapy and targeted therapies. Preclinical studies show that AXL drives anti-HER2 resistance and metastasis through dimerization with HER2 and activation of downstream pathways in breast cancer. Moreover, AXL inhibition restores response to HER2 blockade in vitro and in vivo. Limited data in gastric and oesophageal cancer also support these evidences. Furthermore, AXL shows a strong value as a prognostic and predictive biomarker in HER2+ breast cancer patients, adding a remarkable translational relevance. Therefore, current studies enforce the potential of co-targeting AXL and HER2 to overcome resistance and supports the use of AXL inhibitors in the clinic.

PET/CT and SPECT/CT Imaging of HER2-Positive Breast Cancer

HER2 (Human Epidermal Growth Factor Receptor 2)-positive breast cancer is characterized by amplification of the HER2 gene and is associated with more aggressive tumor growth, increased risk of metastasis, and poorer prognosis when compared to other subtypes of breast cancer. HER2 expression is therefore a critical tumor feature that can be used to diagnose and treat breast cancer. Moving forward, advances in HER2 in vivo imaging, involving the use of techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT), may allow for a greater role for HER2 status in guiding the management of breast cancer patients. This will apply both to patients who are HER2-positive and those who have limited-to-minimal immunohistochemical HER2 expression (HER2-low), with imaging ultimately helping clinicians determine the size and location of tumors. Additionally, PET and SPECT could help evaluate effectiveness of HER2-targeted therapies, such as trastuzumab or pertuzumab for HER2-positive cancers, and specially modified antibody drug conjugates (ADC), such as trastuzumab-deruxtecan, for HER2-low variants. This review will explore the current and future role of HER2 imaging in personalizing the care of patients diagnosed with breast cancer.

The Role of HER2 Status in the Biliary Tract Cancers

Despite recent advances, biliary tract cancer (BTC) is traditionally known as being hard to treat with a poor prognosis. Recent state-of-the-art genomic technologies such as next-generation sequencing (NGS) revolutionized cancer management and shed light on the genomic landscape of BTCs. There are ongoing clinical trials to assess the efficacy of HER2-blocking antibodies or drug conjugates in BTCs with HER2 amplifications. However, HER2 amplifications may not be the sole eligibility factor for these clinical trials. In this review, we aimed to comprehensively examine the role of somatic HER2 alterations and amplifications in patient stratification and provide an overview of the current state of ongoing clinical trials.

18F-labeled FGFR1 peptide: a new PET probe for subtype FGFR1 receptor imaging

Introduction

The fibroblast growth factor receptor (FGFR) family is highly expressed in a variety of tumor types and represents a new target for cancer therapy. Different FGFR subtype aberrations have been found to exhibit highly variable sensitivity and efficacy to FGFR inhibitors.

Methods

The present study is the first to suggest an imaging method for assessing FGFR1 expression. The FGFR1-targeting peptide NOTA-PEG2-KAEWKSLGEEAWHSK was synthesized by manual solid-phase peptide synthesis and high-pressure liquid chromatography (HPLC) purification and then labeled with fluorine-18 using NOTA as a chelator. In vitro and in vivo experiments were conducted to evaluate the stability, affinity and specificity of the probe. Tumor targeting efficacy and biodistribution were evaluated by micro-PET/CT imaging in RT-112, A549, SNU-16 and Calu-3 xenografts.

Results

The radiochemical purity of [18F]F-FGFR1 was 98.66% ± 0.30% (n = 3) with excellent stability. The cellular uptake rate of [18F]F-FGFR1 in the RT-112 cell line (FGFR1 overexpression) was higher than that in the other cell lines and could be blocked by the presence of excess unlabeled FGFR1 peptide. Micro-PET/CT imaging revealed a significant concentration of [18F]F-FGFR1 in RT-112 xenografts with no or very low uptake in nontargeted organs and tissues, which demonstrated that [18F]F-FGFR1 was selectively taken up by FGFR1-positive tumors.

Conclusion

[18F]F-FGFR1 showed high stability, affinity, specificity and good imaging capacity for FGFR1-overexpressing tumors in vivo, which provides new application potential in the visualization of FGFR1 expression in solid tumors.

LY2874455 and Abemaciclib Reverse FGF3/4/19/CCND1 Amplification Mediated Gefitinib Resistance in NSCLC

Non-small cell lung carcinoma (NSCLC) patients who initially received tyrosine kinase inhibitor (TKI) therapy often acquired resistance via multiple complex mechanisms. The amplification of FGF3/4/19/CCND1 on chromosome 11q13 was found in many cancers with TKI resistance. However, the role of these amplifications in TKI-resistant NSCLC remains uncovered. Here, we generated the FGF3/4/19/CCND1 amplification model in the NSCLC cell lines PC-9 and HCC827. Upregulation of FGF3/4/19/CCND1 strongly promoted cell proliferation and gefitinib resistance in NSCLC cells. To find out the potential therapeutic strategies, we screened the combination of inhibitors against the FGF/FGFR signaling pathway and the CCND1/CDK4 complex and revealed that gefitinib combined with LY2874455 and abemaciclib exhibited the most effective inhibition of resistance in vitro and in vivo. Mechanistically, FGFs/CCND1 activated the MAPK pathway, which was abolished by the combination drugs. Our study provides a rationale for clinical testing of dual targeting FGFR and CCND1 with LY2874455 and abemaciclib in NSCLC patients who harbored FGF3/4/19/CCND1 amplification.

Novel applications of molecular imaging to guide breast cancer therapy

The goals of precision oncology are to provide targeted drug therapy based on each individual’s specific tumor biology, and to enable the prediction and early assessment of treatment response to allow treatment modification when necessary. Thus, precision oncology aims to maximize treatment success while minimizing the side effects of inadequate or suboptimal therapies. Molecular imaging, through noninvasive assessment of clinically relevant tumor biomarkers across the entire disease burden, has the potential to revolutionize clinical oncology, including breast oncology. In this article, we review breast cancer positron emission tomography (PET) imaging biomarkers for providing early response assessment and predicting treatment outcomes. For 2-¹⁸fluoro-2-deoxy-D-glucose (FDG), a marker of cellular glucose metabolism that is well established for staging multiple types of malignancies including breast cancer, we highlight novel applications for early response assessment. We then review current and future applications of novel PET biomarkers for imaging the steroid receptors, including the estrogen and progesterone receptors, the HER2 receptor, cellular proliferation, and amino acid metabolism.

N6-methyladenosine regulated FGFR4 attenuates ferroptotic cell death in recalcitrant HER2-positive breast cancer

Intrinsic and acquired anti-HER2 resistance remains a major hurdle for treating HER2-positive breast cancer. Using genome-wide CRISPR/Cas9 screening in vitro and in vivo, we identify FGFR4 as an essential gene following anti-HER2 treatment. FGFR4 inhibition enhances susceptibility to anti-HER2 therapy in resistant breast cancer. Mechanistically, m6A-hypomethylation regulated FGFR4 phosphorylates GSK-3β and activates β-catenin/TCF4 signaling to drive anti-HER2 resistance. Notably, suppression of FGFR4 dramatically diminishes glutathione synthesis and Fe²⁺ efflux efficiency via the β-catenin/TCF4-SLC7A11/FPN1 axis, resulting in excessive ROS production and labile iron pool accumulation. Ferroptosis, a unique iron-dependent form of oxidative cell death, is triggered after FGFR4 inhibition. Experiments involving patient-derived xenografts and organoids reveals a synergistic effect of anti-FGFR4 with anti-HER2 therapy in breast cancer with either intrinsic or acquired resistance. Together, these results pinpoint a mechanism of anti-HER2 resistance and provide a strategy for overcoming resistance via FGFR4 inhibition in recalcitrant HER2-positive breast cancer.

Anti-HER2 resistance causes treatment failure in HER2-positive breast cancers. Here the authors identify FGFR4 as one of the vulnerabilities of anti-HER2 resistant breast cancer and show that FGRR4 inhibition enhances sensitivity to anti-HER2 treatment in these resistant cells by triggering ferroptosis.

Intra-tumoral FGFR2 Expression Predicts Prognosis and Chemotherapy Response in Advanced HER2-positive Gastric Cancer Patients

BACKGROUND/AIM

This study aimed to evaluate the relationship between clinical outcomes and intra-tumoral fibroblast growth factor receptor 2 (FGFR2) expression in human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC) patients who had undergone HER2-targeted chemotherapy.

PATIENTS AND METHODS

A retrospective analysis was performed in 22 patients with HER2-positive GC, who had undergone systemic chemotherapy. We performed immunohistochemistry staining of FGFR2 expression using surgically resected specimens or biopsied samples and evaluated clinicopathological characteristic and overall survival (OS) in the FGFR2-negative and -positive GC groups.

RESULTS

A total of 8 and 14 patients were placed in the FGFR2-negative and -positive group, respectively. The median OS rates were 56.2 and 16.0 months in the FGFR2-negative and -positive groups, respectively. The FGFR2-negative group had a significantly better prognosis after HER2-targeted chemotherapy [p=0.027 (log-rank test)]. The univariate analysis revealed that performing gastrectomy, response to combination chemotherapy with trastuzumab, and FGFR2 positivity were significantly correlated with OS. In a multivariate analysis, the response to combination chemotherapy with trastuzumab (p=0.008) was significantly correlated with OS. In addition, the proportions of patients who showed CR or PR in response to chemotherapy were 87.5 and 42.9% in the FGFR2-negative and -positive groups, respectively (p=0.031).

CONCLUSION

HER2-positive GC patients, without overexpression of FGFR2, exhibited an improved prognosis and response rate to trastuzumab combination chemotherapy. Assessment of intra-tumoral FGFR2 expression could be helpful in predicting the prognosis and response to trastuzumab in HER2-positive GC patients.

Clinical utility of PDX cohorts to reveal biomarkers of intrinsic resistance and clonal architecture changes underlying acquired resistance to cetuximab in HNSCC

Cetuximab is a widely used drug for treating head and neck squamous cell carcinomas (HNSCCs); however, it provides restricted clinical benefits, and its response duration is limited by drug resistance. Here, we conducted randomized “Phase II-like clinical trials” of 49 HNSCC PDX models and reveal multiple informative biomarkers for intrinsic resistance to cetuximab (e.g., amplification of ANKH, up-regulation of PARP3). After validating these intrinsic resistance biomarkers in another HNSCC PDX cohort (61 PDX models), we generated acquired cetuximab resistance PDX models and analyzed them to uncover resistance mechanisms. Whole exome sequencing and transcriptome sequencing revealed diverse patterns of clonal selection in acquired resistant PDXs, including the emergence of subclones with strongly activated RAS/MAPK. Extending these insights, we show that a combination of a RAC1/RAC3 dual-target inhibitor and cetuximab could overcome acquired cetuximab resistance in vitro and in vivo. Beyond revealing intrinsic resistance biomarkers, our PDX-based study shows how clonal architecture changes underlying acquired resistance can be targeted to expand the therapeutic utility of this important drug to more HNSCC patients.

Fibroblast growth factor receptor signalling dysregulation and targeting in breast cancer

Fibroblast Growth Factor Receptor (FGFR) signalling plays a critical role in breast embryonal development, tissue homeostasis, tumorigenesis and metastasis. FGFR, its numerous FGF ligands and signalling partners are often dysregulated in breast cancer progression and are one of the causes of resistance to treatment in breast cancer. Furthermore, FGFR signalling on epithelial cells is affected by signals from the breast microenvironment, therefore increasing the possibility of breast developmental abnormalities or cancer progression. Increasing our understanding of the multi-layered roles of the complex family of FGFRs, their ligands FGFs and their regulatory partners may offer novel treatment strategies for breast cancer patients, as a single agent or rational co-target, which will be explored in depth in this review.

FGFR1 Amplification and Response to Neoadjuvant Anti-HER2 Treatment in Early HER2-Positive Breast Cancer

HER2-positive breast cancer (BC) is an aggressive subtype that affects 20–25% of BC patients. For these patients, neoadjuvant therapy is a good option that targets a pathological complete response (pCR) and more breast-conserving surgery. In effect, the outcomes of patients with HER2-positive BC have dramatically improved since the introduction of anti-HER2 antibodies such as trastuzumab (TZ) and/or pertuzumab (PZ) added to chemotherapy. This study sought to examine whether correlation exists between copy number variations (CNVs) in several genes related to the PI3K/AKT pathway (HER2, FGFR1, PIK3CA, AKT3 and MDM2) and the efficacy of anti-HER2 neoadjuvant treatment in patients with early HER2-positive BC. Forty-nine patients received TZ or PZ/TZ and chemotherapy as neoadjuvant treatment. Gene CNVs were determined by quantitative polymerase chain reaction on paraffin-embedded biopsy specimens. The response to 6 months of therapy was assessed by Miller–Payne grading of the tumor on surgical resection; grades 4 and 5, indicating >90% tumor reduction, were defined as a good response. A good response was shown by 64.5% and a pCR by 31.2% of patients. When stratified by anti-HER2 antibody received and gene CNV, it was found that patients with FGFR1 gene amplification or those with FGFR1 amplification treated with TZ alone showed a poor response (p = 0.024 and p = 0.037, respectively). In the subset of patients treated with TZ/PZ combined, the pCR rate was significantly lower among those showing FGFR1 amplification (p = 0.021). Although based on a small sample size, our findings suggest that patients with FGFR1 amplification might benefit less from anti-HER2 antibody therapy.

Immune Effective Score as a Predictor of Response to Neoadjuvant Trastuzumab Therapy and a Prognostic Indicator for HER2-Positive Breast Cancer

Background: HER2-positive breast cancer (BC) is a highly aggressive phenotype. The role of the host immune features in predictive response to anti-HER2 therapies and prognosis in BC has already been suggested. We aimed to develop a predictive and prognostic model and examine its relevance to the clinical outcomes of patients with HER2-positive BC. Methods: Immune effective score (IES) was constructed using principal component analysis algorithms. A bioinformatic analysis using four independent cohorts (GSE66305, n = 88; GSE130786, n = 110; TCGA, n = 123; METABRIC, n = 236) established associations between IES and clinical outcomes. Results: Genes associated with neoadjuvant trastuzumab therapy response were enriched in pathways related to antitumor immune activities. IES was demonstrated to be a predictive biomarker to neoadjuvant trastuzumab therapy benefits (GSE66305: area under the curve (AUC) = 0.804; GSE130786: AUC = 0.704). In addition, IES was identified as an independent prognostic factor for overall survival (OS) in the TCGA cohort (p = 0.036, hazard ratio (HR): 0.66, 95% confidence interval (CI): 0.449–0.97) and METABRIC cohort (p = 0.037, HR: 0.9, 95% CI: 0.81–0.99). Conclusion: IES has a predictive value for response to neoadjuvant trastuzumab therapy and independent prognostic value for HER2-positive breast cancer.

FGF/FGFR-Dependent Molecular Mechanisms Underlying Anti-Cancer Drug Resistance

Simple Summary

Deregulation of the FGF/FGFR axis is associated with many types of cancer and contributes to the development of chemoresistance, limiting the effectiveness of current treatment strategies. There are several mechanisms involved in this phenomenon, including cross-talks with other signaling pathways, avoidance of apoptosis, stimulation of angiogenesis, and initiation of EMT. Here, we provide an overview of current research and approaches focusing on targeting components of the FGFR/FGF signaling module to overcome drug resistance during anti-cancer therapy.

Abstract

Increased expression of both FGF proteins and their receptors observed in many cancers is often associated with the development of chemoresistance, limiting the effectiveness of currently used anti-cancer therapies. Malfunctioning of the FGF/FGFR axis in cancer cells generates a number of molecular mechanisms that may affect the sensitivity of tumors to the applied drugs. Of key importance is the deregulation of cell signaling, which can lead to increased cell proliferation, survival, and motility, and ultimately to malignancy. Signaling pathways activated by FGFRs inhibit apoptosis, reducing the cytotoxic effect of some anti-cancer drugs. FGFRs-dependent signaling may also initiate angiogenesis and EMT, which facilitates metastasis and also correlates with drug resistance. Therefore, treatment strategies based on FGF/FGFR inhibition (using receptor inhibitors, ligand traps, monoclonal antibodies, or microRNAs) appear to be extremely promising. However, this approach may lead to further development of resistance through acquisition of specific mutations, metabolism switching, and molecular cross-talks. This review brings together information on the mechanisms underlying the involvement of the FGF/FGFR axis in the generation of drug resistance in cancer and highlights the need for further research to overcome this serious problem with novel therapeutic strategies.

Biological Significance and Targeting of the FGFR Axis in Cancer

Simple Summary

All cells within tissues and organ systems must communicate with each other to ensure they function in a coordinated manner. One form of communication is signalling mediated by small proteins (for example fibroblast growth factors; FGFs) that are secreted by one cell and bind to specialised receptors (for example FGF receptors) on nearby cells. These receptors propagate the signal to the nucleus of the receiving cell, which in turn dictates to the cell how it should react. FGFR signalling is versatile, tightly controlled and important for normal body homeostasis, facilitating growth, healing and replacing old cells. However, cancer cells can take command of this pathway and use it to their advantage. This review will first explain the biology of FGFR signalling and then describe how it can be corrupted, the implications in cancer, and how it can be targeted to improve cancer therapy.

Abstract

The pleiotropic effects of fibroblast growth factors (FGFs), the widespread expression of all seven signalling FGF receptors (FGFRs) throughout the body, and the dramatic phenotypes shown by many FGF/R knockout mice, highlight the diversity, complexity and functional importance of FGFR signalling. The FGF/R axis is critical during normal tissue development, homeostasis and repair. Therefore, it is not surprising that substantial evidence also pinpoints the involvement of aberrant FGFR signalling in disease, including tumourigenesis. FGFR aberrations in cancer include mutations, gene fusions, and amplifications as well as corrupted autocrine/paracrine loops. Indeed, many clinical trials on cancer are focusing on targeting the FGF/FGFR axis, using selective FGFR inhibitors, nonselective FGFR tyrosine kinase inhibitors, ligand traps, and monoclonal antibodies and some have already been approved for the treatment of cancer patients. The heterogeneous tumour microenvironment and complexity of FGFR signalling may be some of the factors responsible for the resistance or poor response to therapy with FGFR axis-directed therapeutic agents. In the present review we will focus on the structure and function of FGF(R)s, their common irregularities in cancer and the therapeutic value of targeting their function in cancer.

Targetable Pathways in Advanced Bladder Cancer: FGFR Signaling

Bladder cancer is the 10th most commonly diagnosed cancer in the world, accounting for around 573,000 new cases and 213,000 deaths in 2020. The current standard treatment for locally advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. The significant progress being made in the genomic and molecular understandings of bladder cancer has uncovered the genetic alterations and signaling pathways that drive bladder cancer progression. These developments have led to a dramatic increase in the evaluation of molecular agents targeting at these alterations. One example is Erdafitinib, a first-in-class FGFR inhibitor being approved as second-line treatment for locally advanced or metastatic urothelial carcinoma with FGFR mutations. Immunotherapy has also been approved as second-line treatment for advanced and metastatic bladder cancer. Preclinical studies suggest targeted therapy combined with immunotherapy has the potential to markedly improve patient outcome. Given the prevalence of FGFR alternations in bladder cancer, here we review recent preclinical and clinical studies on FGFR inhibitors and analyze possible drug resistance mechanisms to these agents. We also discuss FGFR inhibitors in combination with other therapies and its potential to improve outcome.

Reciprocal priming between receptor tyrosine kinases at recycling endosomes orchestrates cellular signalling outputs

Integration of signalling downstream of individual receptor tyrosine kinases (RTKs) is crucial to fine-tune cellular homeostasis during development and in pathological conditions, including breast cancer. However, how signalling integration is regulated and whether the endocytic fate of single receptors controls such signalling integration remains poorly elucidated. Combining quantitative phosphoproteomics and targeted assays, we generated a detailed picture of recycling-dependent fibroblast growth factor (FGF) signalling in breast cancer cells, with a focus on distinct FGF receptors (FGFRs). We discovered reciprocal priming between FGFRs and epidermal growth factor (EGF) receptor (EGFR) that is coordinated at recycling endosomes. FGFR recycling ligands induce EGFR phosphorylation on threonine 693. This phosphorylation event alters both FGFR and EGFR trafficking and primes FGFR-mediated proliferation but not cell invasion. In turn, FGFR signalling primes EGF-mediated outputs via EGFR threonine 693 phosphorylation. This reciprocal priming between distinct families of RTKs from recycling endosomes exemplifies a novel signalling integration hub where recycling endosomes orchestrate cellular behaviour. Therefore, targeting reciprocal priming over individual receptors may improve personalized therapies in breast and other cancers.

Cancer-Associated Fibroblasts in Breast Cancer Treatment Response and Metastasis

Breast cancer (BrCa) is the leading cause of death among women worldwide, with about one million new cases diagnosed each year. In spite of the improvements in diagnosis, early detection and treatment, there is still a high incidence of mortality and failure to respond to current therapies. With the use of several well-established biomarkers, such as hormone receptors and human epidermal growth factor receptor-2 (HER2), as well as genetic analysis, BrCa patients can be categorized into multiple subgroups: Luminal A, Luminal B, HER2-enriched, and Basal-like, with specific treatment strategies. Although chemotherapy and targeted therapies have greatly improved the survival of patients with BrCa, there is still a large number of patients who relapse or who fail to respond. The role of the tumor microenvironment in BrCa progression is becoming increasingly understood. Cancer-associated fibroblasts (CAFs) are the principal population of stromal cells in breast tumors. In this review, we discuss the current understanding of CAFs' role in altering the tumor response to therapeutic agents as well as in fostering metastasis in BrCa. In addition, we also review the available CAFs-directed molecular therapies and their potential implications for BrCa management.

HER3 PET Imaging Identifies Dynamic Changes in HER3 in Response to HER2 Inhibition with Lapatinib

PURPOSE

Standard therapy for HER2+ breast cancers includes HER2 inhibition. While HER2 inhibitors have significantly improved therapeutic outcomes, many patients remain resistant to therapy. An important intrinsic resistance mechanism to HER2 inhibition in some breast cancers is dynamic upregulation of HER3. Increase in HER3 expression that occurs in response to HER2 inhibition allows for continued growth signaling through HER2/HER3 heterodimers, promoting tumor escape. We hypothesized that a non-invasive method to image changes in HER3 expression would be valuable to identify those breast cancers that dynamically upregulate HER3 in response to HER2 inhibition. We further hypothesized that this imaging method could identify those tumors that would benefit by additional HER3 knockdown.

PROCEDURES

In a panel of HER2+ breast cancer cell lines treated with the HER2 inhibitor lapatinib, we evaluate changes in HER3 expression and viability. Mouse HER2+ breast cancer models treated with lapatinib were imaged with a peptide-based HER3-specific PET imaging agent [⁶⁸Ga]HER3P1 to assess for dynamic changes in tumoral HER3 expression and uptake confirmed by biodistribution. Subsequently, HER2+ cell lines were treated with the HER2 inhibitor lapatinib as well HER3-specific siRNA to assess for changes in viability and correlate with HER3 expression upregulation. For all statistical comparisons, P<0.05 was considered statistically significant.

RESULTS

Lapatinib treatment of a panel of HER2+ breast cancer cell lines increased HER3 expression in the lapatinib-resistant cell line MDA-MB 453 but not the lapatinib-resistant cell-line HCC-1569. Evaluation of [⁶⁸Ga]HER3P1 uptake in mice implanted with the HER2+ breast cancer cell lines MDA-MB453 or HCC-1569 prior to and after treatment with lapatinib demonstrated a significant increase in MDA-MB453 tumors only, consistent with in vitro findings. The additional knockdown of HER3 increased therapeutic efficacy of lapatinib only in MDA-MB453 cells, but not in HCC-1569 cells.

CONCLUSION

HER3 PET imaging can be used to visualize dynamic changes in HER3 expression that occur in HER2+ breast cancers with HER2 inhibitor treatment and identify those likely to benefit by the addition of combination HER3 and HER2 inhibition.

Concurrent mutations associated with trastuzumab-resistance revealed by single cell sequencing

PURPOSE

HER2-positive breast cancer patients benefit from HER2-targeted therapies, among which the most commonly used is trastuzumab. However, acquired resistance typically happens within one year. The cellular heterogeneity of it is less clear.

METHODS

Here we generated trastuzumab-resistant cells in two HER2-positive breast cancer cell lines, SK-BR-3 and BT-474. Cells at different time points during the resistance induction were examined by exome sequencing to study changes of genomic alterations over time. Single cell-targeted sequencing was also used to identify resistance-associated concurrent mutations.

RESULTS

We found a rapid increase of copy number variation (CNV) regions and gradual accumulation of single nucleotide variations (SNVs). On the pathway level, non-synonymous SNVs for SK-BR-3 cells were enriched in the MAPK signaling pathway, while for BT-474 cells they were enriched in mTOR and PI3K-Akt signaling pathways. However, all of the three signaling pathways were in the downstream of the HER2 kinase. Putative trastuzumab-resistance-associated SNVs included AIFM1 P548L and ERBB2 M833R in SK-BR-3 cells, and ADAMTS19 V451L, OR5M9 D230N, COL9A1 R627T, and ITGA7 H911Q in BT-474 cells. Single-cell-targeted sequencing identified several concurrent mutations. By validation, we found that concurrent mutations (AIFM1 P548L and IL1RAPL2 S546C in SK-BR-3 cells, MFSD11 L242I and ANAPC4 E16K in BT-474 cells) led to a decrease of trastuzumab sensitivity.

CONCLUSION

Taken together, our study revealed a common pathway level trastuzumab-resistance mechanism for HER2-positive breast cancer cells. In addition, our identification of concurrent SNVs associated with trastuzumab-resistance may be indicative of potential targets for the treatment of trastuzumab-resistant breast cancer patients.

Fibroblast growth factor receptors in cancer: genetic alterations, diagnostics, therapeutic targets and mechanisms of resistance

Fibroblast growth factor receptors (FGFRs) are aberrantly activated through single-nucleotide variants, gene fusions and copy number amplifications in 5-10% of all human cancers, although this frequency increases to 10-30% in urothelial carcinoma and intrahepatic cholangiocarcinoma. We begin this review by highlighting the diversity of FGFR genomic alterations identified in human cancers and the current challenges associated with the development of clinical-grade molecular diagnostic tests to accurately detect these alterations in the tissue and blood of patients. The past decade has seen significant advancements in the development of FGFR-targeted therapies, which include selective, non-selective and covalent small-molecule inhibitors, as well as monoclonal antibodies against the receptors. We describe the expanding landscape of anti-FGFR therapies that are being assessed in early phase and randomised controlled clinical trials, such as erdafitinib and pemigatinib, which are approved by the Food and Drug Administration for the treatment of FGFR3-mutated urothelial carcinoma and FGFR2-fusion cholangiocarcinoma, respectively. However, despite initial sensitivity to FGFR inhibition, acquired drug resistance leading to cancer progression develops in most patients. This phenomenon underscores the need to clearly delineate tumour-intrinsic and tumour-extrinsic mechanisms of resistance to facilitate the development of second-generation FGFR inhibitors and novel treatment strategies beyond progression on targeted therapy.

Targeted Treatment of Triple-Negative Breast Cancer

ABSTRACT

Triple-negative breast cancer is increasingly recognized as a heterogeneous entity that can be categorized according to histologic, molecular, and clinical subtypes. While chemotherapy remains the backbone of treatment for this disease, there are now several available targeted agents including immunotherapy, poly(adenosine diphosphate-ribose) polymerase inhibitors, and most recently a Food and Drug Administration-approved antibody-drug conjugate sacituzumab govitecan-hziy as a third-line treatment of metastatic triple-negative breast cancer. We review several actionable targets for triple-negative breast cancer and describe promising nonimmunotherapeutic agents including cyclin-dependent kinase inhibitors, androgen receptor inhibitors, mitogen-activated protein kinase inhibitors, phosphoinositide 3-kinase inhibitors, AKT (also known as protein kinase B) inhibitors, and antibody-drug conjugates.

Fibroblast growth factor receptor facilitates recurrence of minimal residual disease following trastuzumab emtansine therapy

Trastuzumab-emtansine (T-DM1) is an antibody-drug conjugate (ADC) that efficiently delivers a highly potent microtubule inhibitor to HER2 overexpressing cells. Herein, we utilize HER2 transformed human mammary epithelial cells (HME2) to demonstrate in vitro and in vivo response and recurrence upon T-DM1 treatment. Continuous in vitro dosing of HME2 cells with T-DM1 failed to produce a spontaneously resistant cell line. However, induction of epithelial-mesenchymal transition (EMT) via pretreatment with TGF-β1 was capable of promoting emergence of T-DM1-resistant (TDM1R) cells. Flow cytometric analyses indicated that induction of EMT decreased trastuzumab binding, prior to overt loss of HER2 expression in TDM1R cells. Kinome analyses of TDM1R cells indicated increased phosphorylation of ErbB1, ErbB4, and FGFR1. TDM1R cells failed to respond to the ErbB kinase inhibitors lapatinib and afatinib, but they acquired sensitivity to FIIN4, a covalent FGFR kinase inhibitor. In vivo, minimal residual disease (MRD) remained detectable via bioluminescent imaging following T-DM1-induced tumor regression. Upon cessation of the ADC, relapse occurred and secondary tumors were resistant to additional rounds of T-DM1. These recurrent tumors could be inhibited by FIIN4. Moreover, ectopic overexpression of FGFR1 was sufficient to enhance tumor growth, diminish trastuzumab binding, and promote recurrence following T-DM1-induced MRD. Finally, patient-derived xenografts from a HER2+ breast cancer patient who had progressed on trastuzumab failed to respond to T-DM1, but tumor growth was significantly inhibited by FIIN4. Overall, our studies strongly support therapeutic combination of TDM1 with FGFR-targeted agents in HER2+ breast cancer.

Epigenetic targeting of neuropilin-1 prevents bypass signaling in drug-resistant breast cancer

Human epidermal growth factor receptor 2 (HER2)-amplified breast cancers are treated using targeted antibodies and kinase inhibitors, but resistance to these therapies leads to systemic tumor recurrence of metastatic disease. Herein, we conducted gene expression analyses of HER2 kinase inhibitor-resistant cell lines as compared to their drug-sensitive counterparts. These data demonstrate the induction of epithelial-mesenchymal transition (EMT), which included enhanced expression of fibroblast growth factor receptor 1 (FGFR1) and axonal guidance molecules known as neuropilins (NRPs). Immunoprecipitation of FGFR1 coupled with mass spectroscopy indicated that FGFR1 forms a physical complex with NRPs, which is enhanced upon induction of EMT. Confocal imaging revealed that FGFR1 and NRP1 predominantly interact throughout the cytoplasm. Along these lines, short hairpin RNA-mediated depletion of NRP1, but not the use of NRP1-blocking antibodies, inhibited FGFR signaling and reduced tumor cell growth in vitro and in vivo. Our results further indicate that NRP1 upregulation during EMT is mediated via binding of the chromatin reader protein, bromodomain containing 4 (BRD4) in the NRP1 proximal promoter region. Pharmacological inhibition of BRD4 decreased NRP1 expression and ablated FGF-mediated tumor cell growth. Overall, our studies indicate that NRPs facilitate aberrant growth factor signaling during EMT-associated drug resistance and metastasis. Pharmacological combination of epigenetic modulators with FGFR-targeted kinase inhibitors may provide improved outcomes for breast cancer patients with drug-resistant metastatic disease.

The FGF/FGFR System in Breast Cancer: Oncogenic Features and Therapeutic Perspectives

One of the major challenges in the treatment of breast cancer is the heterogeneous nature of the disease. With multiple subtypes of breast cancer identified, there is an unmet clinical need for the development of therapies particularly for the less tractable subtypes. Several transduction mechanisms are involved in the progression of breast cancer, therefore making the assessment of the molecular landscape that characterizes each patient intricate. Over the last decade, numerous studies have focused on the development of tyrosine kinase inhibitors (TKIs) to target the main pathways dysregulated in breast cancer, however their effectiveness is often limited either by resistance to treatments or the appearance of adverse effects. In this context, the fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) system represents an emerging transduction pathway and therapeutic target to be fully investigated among the diverse anti-cancer settings in breast cancer. Here, we have recapitulated previous studies dealing with FGFR molecular aberrations, such as the gene amplification, point mutations, and chromosomal translocations that occur in breast cancer. Furthermore, alterations in the FGF/FGFR signaling across the different subtypes of breast cancer have been described. Next, we discussed the functional interplay between the FGF/FGFR axis and important components of the breast tumor microenvironment. Lastly, we pointed out the therapeutic usefulness of FGF/FGFR inhibitors, as revealed by preclinical and clinical models of breast cancer.

Crosstalk Between Cancer Associated Fibroblasts and Cancer Cells in Scirrhous Type Gastric Cancer

Gastric cancer (GC) is the third leading cause among all cancer deaths globally. Although the treatment outcome of GC has improved, the survival of patients with GC at stages III and IV remains unsatisfactory. Among several types of GC, scirrhous type GC (SGC) shows highly aggressive growth and invasive activity, leading to frequent peritoneal metastasis. SGC is well known to accompany abundant stromal cells that compose the tumor microenvironment (TME) along with the produced extracellular matrix (ECM) and secreted factors. One of the main stromal components is cancer associated fibroblast (CAF). In the SGC microenvironment, CAFs are a source of various secreted factors, including fibroblast growth factors (FGFs), which mediate prominent tumor-stimulating activity. In turn, cancer cells also secrete numerous factors, which can activate and educate CAFs. Current findings suggest that cancer cells and stromal cells communicate interactively via the soluble factors, the ECM, and likely also by exosomes. In this review, we focus on the soluble factors mediating communication between cancer cells and CAFs in SGC, and consider how they are related to the modulation of TME and the high rate of peritoneal metastasis. At last, we discuss the perspectives on targeting these communication pathways for improved future treatment.

Extracellular Matrix-Bound FGF2 Mediates Estrogen Receptor Signaling and Therapeutic Response in Breast Cancer

The extracellular matrix (ECM) is often unaccounted for in studies that consider the stromal contribution to cancer cell signaling and response to treatment. To investigate the influence of a fibrotic microenvironment, we use fibroblast-derived ECM scaffolds as a cell culture platform. We uncover that estrogen receptor-positive (ER⁺) breast cancer cells cultured within ECM-scaffolds have an increase in ER signaling that occurs via an MAPK-dependent, but estrogen-independent manner. The ECM acts as a reservoir by binding, enriching, and presenting growth factors to adjacent epithelial cells. We identified FGF2 as a specific ECM-bound factor that drives ER signaling. ER⁺ cells cultured on ECM matrices have reduced sensitivity to ER-targeted therapies. The sensitivity to ER-targeted therapy can be restored by inhibiting FGF2-FGFR1 binding. ECM-FGF2 complexes promote Cyclin D1 induction that prevents G₁ arrest even in the presence of antiestrogens. This work demonstrates that the ECM can drive ER signaling and resistance to endocrine therapy, and suggests that patients with ER⁺ breast cancer that have high mammographic breast density may benefit from existing FGFR-targeted therapies. IMPLICATIONS: This work uncovers how the ECM may mediate signaling between growth factors and ER⁺ breast cancer cells to promote estrogen-independent ER signaling and resistance to endocrine therapy.

The root cause of drug resistance in HER2-positive breast cancer and the therapeutic approaches to overcoming the resistance

HER2 is a well-known oncogenic receptor tyrosine kinase. HER2 gene amplification occurs in about 20% of breast cancer (BC), which leads to overexpression of HER2 protein, known as HER2-positive BC. Inhibitors of HER2 have significantly improved the prognosis of patients with this subset of BC. Since 1998, seven HER2 inhibitors have been developed to treat this disease. However, drug resistance is common and remains a major unresolved clinical problem. Patients typically show disease progression after some time on treatment. This review discusses the complexity and diversified nature of HER2 signaling, the mechanisms of actions and therapeutic activities of all HER2 inhibitors, the roles of HER2 and other signaling proteins in HER2-positive BC resistant to the inhibitors, the non-cell-autonomous mechanisms of drug resistance, and the heterogeneity of tumor HER2 expression. The review presents the concept that drug resistance in HER2-positive BC results primarily from the inability of HER2 inhibitors to deplete HER2. Emerging therapeutics that are promising for overcoming drug resistance are also discussed.

Impact of fibroblast growth factor receptor 1 (FGFR1) amplification on the prognosis of breast cancer patients

Purpose

Various aberrations in the fibroblast growth factor receptor genes FGFR1, FGFR2, and FGFR3 are found in different cancers, including breast cancer (BC). This study analyzed the impact of FGFR amplification on the BC prognosis.

Methods

The study included 894 BC patients. The amplification rates of FGFR1, FGFR2, and FGFR3 were evaluated on tissue microarrays using fluorescence in situ hybridization (FISH). Associations between these parameters and prognosis were analyzed using multivariate Cox regression analyses.

Results

FGFR1 FISH was assessable in 503 samples, FGFR2 FISH in 447, and FGFR3 FISH in 562. The FGFR1 amplification rate was 6.6% (n = 33). Increased FGFR2 copy numbers were seen in 0.9% (n = 4); only one patient had FGFR3 amplification (0.2%). Most patients with FGFR1 amplification had luminal B-like tumors (69.7%, n = 23); only 32.6% (n = 153) of patients without FGFR1 amplification had luminal B-like BC. Other patient and tumor characteristics appeared similar between these two groups. Observed outcome differences between BC patients with and without FGFR1 amplification did not achieve statistical significance; however, there was a trend toward poorer distant metastasis-free survival in BC patients with FGFR1 amplification (HR = 2.08; 95% CI 0.98 to 4.39, P = 0.05).

Conclusion

FGFR1 amplification occurs most frequently in patients with luminal B-like BC. The study showed a nonsignificant correlation with the prognosis, probably due to the small sample size. Further research is therefore needed to address the role of FGFR1 amplifications in early BC patients. FGFR2 and FGFR3 amplifications are rare in patients with primary BC.

Electronic supplementary material

The online version of this article (10.1007/s10549-020-05865-2) contains supplementary material, which is available to authorized users.

miR-511 inhibits proliferation and metastasis of breast cancer cells by targeting FGF4

BACKGROUND

The present study aimed to explore the functions and molecular mechanisms of miR-511 in breast cancer.

METHODS

A quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect miR-511 levels in breast cancer tissues; a chi-squared test was used to analyze the relationship between miR-511 expression level and pathological parameters of breast cancer patients; the proliferation of breast cancer cell lines MDA-MB-231 and MCF-7 was determined by the cell counting kit-8 (CCK-8) assay; migration was determined by scratch wound healing assay and transwell assay; TargetScan was used to predict the binding site between the 3'-untranslated region (3'-UTR) of fibroblast growth factor 4 (FGF4) and miR-511; and qRT-PCR, western blot and a luciferase reporter gene assay were conducted to further validate the targeting relationship between miR-511 and FGF4.

RESULTS

The expression level of miR-511 was lower in breast cancer tissues than that in adjacent normal tissues. Low expression of miR-511 was associated with larger tumor size, lymph node metastasis and short survival time. In vitro experiments showed that miR-511 modulated the proliferation and metastasis of breast cancer cells. It was also confirmed that miR-511 directly targeted 3'-UTR of FGF4 and reduced its expression, and FGF4 overexpression reversed the effect of miR-511 on the malignant phenotypes of breast cancer cells.

CONCLUSIONS

The results obtained in the present study demonstrate that miR-511 inhibits breast cancer proliferation and metastasis by down-regulating FGF4 expression, which may be helpful in the development of new treatment strategies for breast cancer.

A phase II trial of the FGFR inhibitor pemigatinib in patients with metastatic esophageal-gastric junction/gastric cancer trastuzumab resistant: the FiGhTeR trial

Background:

Prognosis of patients affected by metastatic esophageal–gastric junction (EGJ) or gastric cancer (GC) remains dismal. Trastuzumab, an anti-HER2 monoclonal antibody, is the only targeted agent approved for the first-line treatment of patients with HER2-overexpressing advanced EGJ or GC in combination with chemotherapy. However, patients invariably become resistant during this treatment. We recently identified the overexpression of fibroblast growth factor (FGF) receptor 3 (FGFR3) as a molecular mechanism responsible for trastuzumab resistance in GC models, providing the rationale for the inhibition of this receptor as a potential second-line strategy in this disease. Pemigatinib is a selective, potent, oral inhibitor of FGFR1, 2, and 3.

Methods:

The FiGhTeR trial is a phase II, single-arm, open-label study to assess safety and activity of the FGFR inhibitor pemigatinib as second-line treatment strategy in metastatic EGJ/GC patients progressing under trastuzumab-containing therapies. The primary endpoint is the 12-week progression-free survival rate. Plasma and tumor tissue samples will be collected for translational research analyses at baseline, during treatment, and at progression on pemigatinib.

Discussion:

Co-alterations in genes coding for different tyrosine-kinase receptors are emerging as relevant mechanisms of acquired resistance to anti-HER2 therapeutic strategies in GC. In particular, our group has recently identified that in GC models the overexpression of FGFR3 sustains the acquired resistance to trastuzumab. This trial aims to assess the safety, tolerability and activity of the FGFR inhibitor pemigatinib as a second-line treatment in metastatic EGJ/GC patients refractory to first-line trastuzumab-containing therapies. Furthermore, this study offers the opportunity to prospectively study mechanisms and pathways involved in trastuzumab resistance.

Protocol number:

CRC2017_02

EudraCT Number:

2017-004522-14

Phase II Study of AZD4547 in Patients With Tumors Harboring Aberrations in the FGFR Pathway: Results From the NCI-MATCH Trial (EAY131) Subprotocol W

PURPOSE

NCI-MATCH is a nationwide, histology-agnostic, signal-finding, molecular profile-driven trial for patients with refractory cancers, lymphomas, or myelomas. Patients with tumors harboring actionable aberration(s) in fibroblast growth factor receptor (FGFR) 1-3 were treated with AZD4547, an oral FGFR1-3 inhibitor.

METHODS

Patients' tumors were screened by next-generation sequencing for predefined FGFR amplification, activating mutations, or fusions. Patients were treated with AZD4547, 80 mg orally twice daily until progression of disease or drug intolerance. A response rate of 16% was considered promising.

RESULTS

Between July 2016 and June 2017, 70 patients were assigned and 48 received protocol therapy and are eligible for analysis. Patients' tumors harbored FGFR1 or FGFR2 amplification (n = 20), FGFR2 or FGFR3 single-nucleotide variants (n = 19), or FGFR1 or FGFR3 fusions (n = 9). The most common primary tumors were breast (33.3%), urothelial (12.5%), and cervical cancer (10.4%).Grade 3 adverse events were consistent with those described in previous clinical trials. Confirmed partial responses were seen in 8% (90% CI, 3% to 18%) and were observed only in patients whose tumors harbored FGFR1-3 point mutations or fusions. Stable disease was observed in 37.5% (90% CI, 25.8% to 50.4%). The median progression-free survival (PFS) was 3.4 months, and the 6-month PFS rate was 15% (90% CI, 8% to 31%). For patients with tumors harboring FGFR fusions, the response rate was 22% (90% CI, 4.1% to 55%), and 6-month PFS rate was 56% (90% CI, 31% to 100%).

CONCLUSION

Preliminary signals of activity appeared to be limited to cancers harboring FGFR activating mutations and fusions, although AZD4547 did not meet the primary end point. Different FGFR somatic alterations may confer different levels of signaling potency and/or oncogene dependence.

Genetic alterations and their association with clinicopathologic characteristics in advanced breast carcinomas: focusing on clinically actionable genetic alterations

Breast carcinomas (BCs) are genetically heterogeneous and associated with numerous mutations which can be used to predict outcomes and initiate targeted therapies. We investigated clinicopathologic characteristics associated with gene mutations detected using the FoundationOne CDx assay in a cohort of 223 clinically advanced BCs (66 locally recurrent and 157 metastatic) from our institution. One hundred fifty unique mutations were identified (total 1008) in the cohort, with the most prevalent (>10%) including TP53 (53.8%), PIK3CA (35%), MYC (22%), CCND1 (19.7%), FGF19 (19.7%), FGF4 (16.6%), FGF3 (16.1%), ZNF703 (14.8%), ESR1 (13.9%), FGFR1 (13.5%), PTEN (12.1%), and CDH1 (10.8%). ERBB2 genetic alteration was most common in human epidermal growth factor receptor 2 (HER2)-positive BCs, and GATA3 and ESR1 mutations were only identified in hormone receptor-positive BC. Mutations enriched in triple-negative BCs (TNBCs) included TP53, PTEN, RB1, and CDKN2A/B. CDH1 mutation was predominantly found in lobular carcinomas, and PIK3CA mutation was also enriched. Mutations enriched in metaplastic carcinomas with heterologous mesenchymal differentiation included TP53, PTEN, MCL1, CDKN2A/B, and NOTCH2. An increase in mutations of CCND1, FGF19, FGF4, FGF3, ESR1, and EMSY was identified in metastatic BCs compared with locally recurrent BCs. Overall, PIK3CA was the most frequent clinically actionable genetic alteration (35%), followed by MYC (22%), CCND1 (19.7%), and FGF3/FGF4/FGFR1 (16%). In conclusion, our study provides genetic insight into the biology of advanced BCs and summarizes their most frequent clinically actionable genetic alterations, generating useful genomic information for potential improvement of patient management.

Inhibition of the transcriptional kinase CDK7 overcomes therapeutic resistance in HER2-positive breast cancers

Resistance of breast cancer to human epidermal growth factor receptor 2 (HER2) inhibitors involves reprogramming of the kinome through HER2/HER3 signaling via the activation of multiple tyrosine kinases and transcriptional upregulation. The heterogeneity of induced kinases prevents kinase targeting by a single kinase inhibitor and presents a major challenge to the treatment of therapeutically recalcitrant HER2-positive breast cancers (HER2+ BCs). As a result, there is a critical need for effective treatment that attacks the aberrant kinome activation associated with resistance to HER2-targeted therapy. Here, we describe a novel treatment strategy that targets cyclin-dependent kinase 7 (CDK7) in HER2 inhibitor-resistant (HER2iR) breast cancer. We show that both HER2 inhibitor-sensitive (HER2iS) and HER2iR breast cancer cell lines exhibit high sensitivity to THZ1, a newly identified covalent inhibitor of the transcription regulatory kinase CDK7. CDK7 promotes cell cycle progression through inhibition of transcription, rather than via direct phosphorylation of classical CDK targets. The transcriptional kinase activity of CDK7 is regulated by HER2, and by the receptor tyrosine kinases activated in response to HER2 inhibition, as well as by the downstream SHP2 and PI3K/AKT pathways. A low dose of THZ1 displayed potent synergy with the HER2 inhibitor lapatinib in HER2iR BC cells in vitro. Dual HER2 and CDK7 inhibition induced tumor regression in two HER2iR BC xenograft models in vivo. Our data support the utilization of CDK7 inhibition as an additional therapeutic avenue that blocks the activation of genes engaged by multiple HER2iR kinases.

A Comparison of DNA Mutation and Copy Number Profiles of Primary Breast Cancers and Paired Brain Metastases for Identifying Clinically Relevant Genetic Alterations in Brain Metastases

Improving the systemic treatment of brain metastases (BM) in primary breast cancer (PBC) is impaired by the lack of genomic characterization of BM. To estimate the concordance of DNA copy-number-alterations (CNAs), mutations, and actionable genetic alterations (AGAs) between paired samples, we performed whole-genome array-comparative-genomic-hybridization, and targeted-next-generation-sequencing on 14 clinical PBC–BM pairs. We found more CNAs, more mutations, and higher tumor mutational burden, and more AGAs in BM than in PBC; 92% of the pairs harbored at least one AGA in the BM not observed in the paired PBC. This concerned various therapeutic classes, including tyrosine-kinase-receptor-inhibitors, phosphatidylinositol 3-kinase/AKT/ mammalian Target of Rapamycin (PI3K/AKT/MTOR)-inhibitors, poly ADP ribose polymerase (PARP)-inhibitors, or cyclin-dependent kinase (CDK)-inhibitors. With regards to the PARP-inhibitors, the homologous recombination defect score was positive in 79% of BM, compared to 43% of PBC, discordant in 7 out of 14 pairs, and positive in the BM in 5 out of 14 cases. CDK-inhibitors were associated with the largest percentage of discordant AGA appearing in the BM. When considering the AGA with the highest clinical-evidence level, for each sample, 50% of the pairs harbored an AGA in the BM not detected or not retained from the analysis of the paired PBC. Thus, the profiling of BM provided a more reliable opportunity, than that of PBC, for diagnostic decision-making based on genomic analysis. Patients with BM deserve an investigation of several targeted therapies.

A functional CRISPR/Cas9 screen identifies kinases that modulate FGFR inhibitor response in gastric cancer

Some gastric cancers have FGFR2 amplifications, making them sensitive to FGFR inhibitors. However, cancer cells inevitably develop resistance despite initial response. The underlying resistance mechanism to FGFR inhibition is unclear. In this study, we applied a kinome-wide CRISPR/Cas9 screen to systematically identify kinases that are determinants of sensitivity to a potent FGFR inhibitor AZD4547 in KatoIII cells, a gastric cancer cell line with FGFR2 amplification. In total, we identified 20 kinases, involved in ILK, SRC, and EGFR signaling pathways, as determinants that alter cell sensitivity to FGFR inhibition. We functionally validated the top negatively selected and positively selected kinases, ILK and CSK, from the CRISPR/Cas9 screen using RNA interference. We observed synergistic effects on KatoIII cells as well as three additional gastric cancer cell lines with FGFR2 amplification when AZD4547 was combined with small molecular inhibitors Cpd22 and lapatinib targeting ILK and EGFR/HER2, respectively. Furthermore, we demonstrated that GSK3b is one of the downstream effectors of ILK upon FGFR inhibition. In summary, our study systematically evaluated the kinases and associated signaling pathways modulating cell response to FGFR inhibition, and for the first time, demonstrated that targeting ILK would enhance the effectiveness of AZD4547 treatment of gastric tumors with amplifications of FGFR2.

Current Updates on Trastuzumab Resistance in HER2 Overexpressing Breast Cancers

Trastuzumab represents the predominant therapy to target breast cancer subtype marked by HER2 amplification. It has been in use for two decades and its continued importance is underlined by recent FDA approvals of its biosimilar and conjugated versions. Progression to an aggressive disease with acquisition of resistance to trastuzumab remains a major clinical concern. In addition to a number of cellular signaling pathways being investigated, focus in recent years has also shifted to epigenetic and non-coding RNA basis of acquired resistance against trastuzumab. This article provides a succinct discussion on the most recent advances in our understanding of such factors.