Advances and challenges in targeting FGFR signalling in cancer

EGFR-mediated interleukin enhancer-binding factor 3 contributes to formation and survival of cancer stem-like tumorspheres as a therapeutic target against EGFR-positive non-small cell lung cancer

OBJECTIVES

YM155, an inhibitor of interleukin enhancer-binding factor 3 (ILF3), significantly suppresses cancer stemness property, implying that ILF3 contributes to cell survival of cancer stem cells. However, the molecular function of ILF3 inhibiting cancer stemness remains unclear. This study aimed to uncover the potential function of ILF3 involving in cell survival of epidermal growth factor receptor (EGFR)-positive lung stem-like cancer, and to investigate the potential role to improve the efficacy of anti-EGFR therapeutics.

MATERIALS AND METHODS

The association of EGFR and ILF3 in expression and regulations was first investigated in this study. Lung cancer A549 cells with deprivation of ILF3 were created by the gene-knockdown method and then RNAseq was applied to identify the putative genes regulated by ILF3. Meanwhile, HCC827- and A549-derived cancer stem-like cells were used to investigate the role of ILF3 in the formation of cancer stem-like tumorspheres.

RESULTS

We found that EGFR induced ILF3 expression, and YM155 reduced EGFR expression. The knockdown of ILF3 reduced not only EGFR expression in mRNA and protein levels, but also cell proliferation in vitro and in vivo, demonstrating that ILF3 may play an important role in contributing to cancer cell survival. Moreover, the knockdown and inhibition of ILF3 by shRNA and YM155, respectively, reduced the formation and survival of HCC827- and A549-derived tumorspheres through inhibiting ErbB3 (HER3) expression, and synergized the therapeutic efficacy of afatinib, a tyrosine kinase inhibitor, against EGFR-positive A549 lung cells.

CONCLUSION

This study demonstrated that ILF3 plays an oncogenic like role in maintaining the EGFR-mediated cellular pathway, and can be a therapeutic target to improve the therapeutic efficacy of afatinib. Our results suggested that YM155, an ILF3 inhibitor, has the potential for utilization in cancer therapy against EGFR-positive lung cancers.

Design, synthesis and evaluate of novel dual FGFR1 and HDAC inhibitors bearing an indazole scaffold

Both histone deacetylase (HDAC) and fibroblast growth factor receptor (FGFR) are important targets for cancer therapy. Although combining dual HDAC pharmacophore with tyrosine kinase inhibitors (TKIs) had achieved a successful progress, dual HDAC/FGFR1 inhibitors haven't been reported yet. Herein, we designed a series of hybrids bearing 1H-indazol-3-amine and benzohydroxamic acids scaffold with scaffold hopping and molecular hybridization strategies. Among them, compound 7j showed the most potent inhibitory activity against HDAC6 with IC₅₀ of 34 nM and exhibited the great inhibitory activities against a human breast cancer cell line MCF-7 with IC₅₀ of 9 μM in vitro. Meanwhile, the compound also exhibited moderate FGFR1 inhibitory activities. This study provides new tool compounds for further exploration of dual HDAC/FGFR1 inhibition.

Targeting FGFR pathway in breast cancer

Developments in breast cancer biology over the last years have permitted deconstructing the molecular profile of the most relevant breast cancer subtypes. This has led to an increase in therapeutic options, including more effective personalized therapy for breast cancer and substantial improvements in patient outcomes. Although currently there are only a few targeted therapies approved for metastatic breast cancer, the discovery of druggable kinase gene alterations has radically changed cancer treatment by providing novel and successfully actionable drug targets. Fibroblast growth factors and their receptors (FGFRs) participate in different physiologic processes and also play an essential role in cancer cell proliferation, survival, differentiation, migration, and apoptosis. This article summarizes the main molecular alterations of FGFRs, as well as the available preclinical and clinical data with FGFR inhibitors in breast cancer, and discusses new opportunities for the clinical development of these agents in patients with breast cancer.

Resistance mediated by alternative receptor tyrosine kinases in FGFR1-amplified lung cancer

Fibroblast growth factor receptor 1 (FGFR1) amplification has been identified in 10-20% of patients with squamous non-small-cell lung cancer. Preclinical models showed promising activity of specific FGFR inhibitors, but early clinical trials showed that only a small fraction of patients with FGFR1-amplified lung cancer responded to FGFR inhibitors. These unsatisfactory results were partly explained by heterogeneous amplicons around the 8p11 genomic region, leading to false-positive amplification results. Furthermore, discrepancies in the gene amplification and protein expression of FGFR1 were also reported. In this study, we identified the roles of alternative receptor tyrosine kinases (RTKs) in FGFR1-amplified lung cancer. These alternative RTKs dominantly activate phosphoinositide 3-kinase-AKT signaling and also mitigate sustained inhibition of mitogen-activated protein kinase signaling by FGFR inhibitors. The rebound activation of extracellular signal-regulated kinase phosphorylation was associated with sensitivity to the drugs. Combinatorial inhibition of alternative RTKs and FGFR1 was required to suppress both AKT and extracellular signal-regulated kinase phosphorylation and to induce key pro-apoptotic proteins BIM and p53 upregulated modulator of apoptosis (PUMA). Furthermore, even in FGFR inhibitor-sensitive NCI-H1581 lung cancer cells, MET-expressing clones were already detectable at a very low frequency before resistance induction. Selection of these pre-existing subclones resulted in FGFR inhibitor resistance because of the activation of AKT and extracellular signal-regulated kinase by MET signaling that was mediated by GRB2 associated binding protein 1 (GAB1). These results suggest that incomplete suppression of key survival signals led to intrinsic and acquired resistance to FGFR inhibitors. Our results may help explain the low clinical response rates to FGFR inhibitors in FGFR1-amplified lung cancer.

Genome-wide association studies of cancer: current insights and future perspectives

Genome-wide association studies (GWAS) provide an agnostic approach for investigating the genetic basis of complex diseases. In oncology, GWAS of nearly all common malignancies have been performed, and over 450 genetic variants associated with increased risks have been identified. As well as revealing novel pathways important in carcinogenesis, these studies have shown that common genetic variation contributes substantially to the heritable risk of many common cancers. The clinical application of GWAS is starting to provide opportunities for drug discovery and repositioning as well as for cancer prevention. However, deciphering the functional and biological basis of associations is challenging and is in part a barrier to fully unlocking the potential of GWAS.

FGFR2 regulation by picrasidine Q inhibits the cell growth and induces apoptosis in esophageal squamous cell carcinoma

Fibroblast growth factor receptor (FGFR) 2 and its downstream signaling cascades, PI3 K/AKT/mTOR is playing an important role in cell survival and proliferations. In this study, we firstly found that picrasidine Q (PQ), an alkaloid component extracted from Angelica keiskei species, has the capacity of anti-cell transformation and anti-cancer. After ligand shape similarity approach of PQ, we found that PQ targeted FGFR 2 and verified by FGFR2 kinase assay as well as computational docking model. FGFR2 highly expressed in esophageal cancer tissues and PQ inhibited fibroblast growth factor (FGF)-induced cell transformation. Furthermore, PQ inhibited cell proliferation and induced cell cycle arrest and apoptosis in KYSE30, KYSE410, and KYSE450 esophageal squamous cell carcinoma (ESCC) cells. It was confirmed by detecting of biological markers such as cyclinD1, cyclinD3 and cyclinB1 for cell cycle or cleaved caspase-7, caspase-3, and PARP for apoptosis. PQ targeting of FGFR2 kinase activities suppressed downstream target proteins including phosphorylation of AKT and mTOR but not MEK/ERK signaling pathways. Taken together, our results are the first to identify that PQ might be a chemopreventive and chemotherapeutic agent by direct targeting FGFR2 and inhibiting cell proliferation of ESCC cells.

Breast cancer cell-derived fibroblast growth factors enhance osteoclast activity and contribute to the formation of metastatic lesions

Fibroblast growth factors (FGFs) and their receptors (FGFRs) have been implicated in promoting breast cancer growth and progression. While the autocrine effects of FGFR activation in tumor cells have been extensively studied, little is known about the effects of tumor cell-derived FGFs on cells in the microenvironment. Because FGF signaling has been implicated in the regulation of bone formation and osteoclast differentiation, we hypothesized that tumor cell-derived FGFs are capable of modulating osteoclast function and contributing to growth of metastatic lesions in the bone. Initial studies examining FGFR expression during osteoclast differentiation revealed increased expression of FGFR1 in osteoclasts during differentiation. Therefore, studies were performed to determine whether tumor cell-derived FGFs are capable of promoting osteoclast differentiation and activity. Using both non-transformed and transformed cell lines, we demonstrate that breast cancer cells express a number of FGF ligands that are known to activate FGFR1. Furthermore our results demonstrate that inhibition of FGFR activity using the clinically relevant inhibitor BGJ398 leads to reduced osteoclast differentiation and activity in vitro. Treatment of mice injected with tumor cells into the femurs with BGJ398 leads to reduced osteoclast activity and bone destruction. Together, these studies demonstrate that tumor cell-derived FGFs enhance osteoclast function and contribute to the formation of metastatic lesions in breast cancer.

High amplification of FGFR1 gene is a delayed poor prognostic factor in early stage ESCC patients

Amplification of the fibroblast growth factor receptor 1 (FGFR1) is believed to predict response to FGFR inhibitors. The aim of this study was to investigate the frequency and the prognostic impact of FGFR1 amplification in patients with resected esophageal squamous cell carcinoma (ESCC) by using fluorescent in situ hybridization. Microarrayed paraffin embedded blocks were constructed, and the cohort of tissues came from 506 patients with ESCC. FGFR1 high amplification (FGFR1^high) was defined by an FGFR1/centromere 8 ratio of ≥ 2.0, or average number of FGFR1 signals/tumor cell nucleus ≥ 6.0, or percentage of tumor cells containing ≥ 15 FGFR1 signals, or large cluster in ≥ 10% of cancer cells. FGFR1 low amplification was defined by ≥ 5 FGFR1 signals in ≥ 50% of cancer cells. Kaplan-Meier curves with log-rank tests and Cox proportional hazards model were used to analyze patients’ survival. Among 506 patients, high amplification, low amplification, and disomy were detected in 8.7%, 3.6% and 87.7%, respectively. In general, the FGFR1^high group trended towards worse disease-free survival (DFS) and overall survival (OS) compared to the FGFR1 low amplification/disomy (FGFR1^low/disomy) group (DFS, P=0.108; OS, P=0.112), but this trend was amplified for patients with DFS ≥ 30 months (DFS, P=0.009; OS, P=0.007). Furthermore, when patients were stratified into stage I-II and stage III-IV, the FGFR1^high group directly presented with adverse DFS and OS than the FGFR1^low/disomy group in stage I-II patients (DFS, P=0.019; OS, P=0.034), especially with DFS ≥ 30 months (DFS, P=0.002; OS, P=0.001). However, for patients in stage III-IV, FGFR1^high had no effect on prognosis regardless of DFS time. FGFR1^high occurs in a minority of ESCC, and it predicts delayed poor prognosis in stage I and II ESCC patients.

Fibroblast growth factor-mediated crosstalk in cancer etiology and treatment

It is becoming increasingly evident that multiple cell types within the tumor work together to drive tumour progression and impact on both the response to therapy and the dissemination of tumour cells throughout the body. Fibroblast growth factor signalling (FGF) is perturbed in a number of tumors, serving to drive tumor cell proliferation and migration, but also has a central role in orchestrating the plethora of cells that comprise the tumor microenvironment. This review focuses on how this family of signalling molecules can influence the interactions between tumor cells and their surrounding environment. Unraveling the complexities of FGF signalling between the distinct cell types of a tumor may identify additional opportunities for FGF-targeted compounds in therapy and could help combat drug resistance. Developmental Dynamics 246:493-501, 2017. © 2017 Wiley Periodicals, Inc.

A summary of relationships between alternative splicing and breast cancer

Alternative splicing (AS) is the process of combinatorial rearrangement of parts of exons, and/or parts of introns into mature RNA to result in a multitude of transcripts. AS is a biological process through which organisms produce as many protein variants as possible by a limited genetic resource. It plays an important role in growth and development of the organisms. Over the past few years, alternative splicing has been discovered to be critical for genesis and development of malignant tumors, including breast cancer. If the relationships between AS and breast cancer can be discussed more deeply, it will be helpful for better diagnosis, judging prognosis and intervening with breast cancer. In this paper, the relationships between AS and breast cancer are elaborated from different angles, in hope that this summary is beneficial for readers to understand the roles of AS and breast cancer.