Roles of fibroblast growth factor receptors in carcinogenesis

Elimination of progressive mammary cancer by repeated administrations of chimeric antigen receptor-modified T cells

Continuous oncogenic processes that generate cancer require an on-going treatment approach to eliminate the transformed cells, and prevent their further development. Here, we studied the ability of T cells expressing a chimeric antibody-based receptor (CAR) to offer a therapeutic benefit for breast cancer induced by erbB-2. We tested CAR-modified T cells (T-bodies) specific to erbB-2 for their antitumor potential in a mouse model overexpressing a human erbB-2 transgene that develops mammary tumors. Comparing the antitumor reactivity of CAR-modified T cells under various therapeutic settings, either prophylactic, prior to tumor development, or therapeutically. We found that repeated administration of CAR-modified T cells is required to eliminate spontaneously developing mammary cancer. Systemic, as well as intratumoral administered CAR-modified T cells accumulated at tumor sites and eventually eliminated the malignant cells. Interestingly, within a few weeks after a single CAR T cells' administration, and rejection of primary lesion, tumors usually relapsed both in treated mammary gland and at remote sites; however, repeated injections of CAR-modified T cells were able to control the secondary tumors. Since spontaneous tumors can arise repeatedly, especially in the case of syndromes characterized by specific susceptibility to cancer, multiple administrations of CAR-modified T cells can serve to control relapsing disease.

Fibroblast growth factor receptor 4 promotes progression and correlates to poor prognosis in cholangiocarcinoma

Fibroblast growth factor receptor 4 (FGFR4) is related to poor prognosis of several cancers, but the correlation between FGFR4 expression and cholangiocarcinoma (CCA) has not been well elucidated. We investigated the expression of FGFR4 in 83 intrahepatic cholangiocarcinomas (IHCCs), 75 perihilar cholangiocarcinomas (PHCCs) and 41 distal cholangiocarcinomas (DCCs) by immunohistochemistry (IHC), and subsequently evaluated association of FGFR4 with clinicopathologic parameters and survival rate. The rate of FGFR4 higher expression was 61.4% (51/83) in IHCCs, 53.3% (40/75) in PHCCs and 56.1% (23/41) in DCCs. FGFR4 expression was significantly related to poor prognosis of IHCC (P=0.002) and PHCC (P=0.019) with univariate analysis, and also identified as an independent prognostic factor in IHCC (P=0.045) and PHCC (P=0.049) with multivariate analysis. Additionally, with functional assays in vitro, we found FGFR4 can induce proliferation, invasion and epithelial-mesenchymal transition (EMT) of CCA cell lines with FGF19 stimulation. Moreover, FGFR4 inhibitor AP24354 can suppress proliferation, invasion and induce apoptosis of CCA cells. In conclusion, FGFR4 expression can be identified as a significant independent prognostic biomarker of IHCC and PHCC. FGFR4 played a pivotal role in proliferation, invasion and EMT of CCA. FGFR4 inhibitor can suppress proliferation, invasion and induce apoptosis of CCA, indicating that FGFR4 may act as a potential therapeutic target.

microRNA-99a inhibiting cell proliferation, migration and invasion by targeting fibroblast growth factor receptor 3 in bladder cancer

The expression of microRNA-99a (miRNA-99a) has been investigated in a number of human cancers. It has been reported to be downregulated in several types of cancer, including ovarian carcinoma, squamous cell carcinoma of the tongue, squamous cell lung carcinoma, hepatocellular carcinoma, bladder cancer, prostate cancer and childhood adrenocortical tumors. In the present study, the effects of miRNA-99a on bladder cancer cell proliferation, migration and invasion were examined. Following transfection of miRNA-99a, cell viability, cell migration assay, cell invasion, western blot analysis and luciferase assays were conducted in bladder cancer cell lines. It was found that miRNA-99a inhibits cell proliferation, migration and invasion in T24 and EJ cells. Additionally, this study provided the first evidence that miRNA-99a is likely to directly target fibroblast growth factor receptor 3 in bladder cancer. The study provided evidence that miRNA-99a suppresses cell proliferation, migration and invasion by targeting growth factor receptor 3 in bladder cancer cell lines. These results indicated that it could be investigated as a target for therapeutic drugs designed to treat bladder cancer.

The involvement of fibroblast growth factor receptor signaling pathways in dermatofibroma and dermatofibrosarcoma protuberans

Fibroblast growth factors (FGFs) and their receptors (FGFRs) control a wide range of biological functions; however, their involvement in the pathogenesis of dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) is currently unknown. In this study, we first confirmed the histological diagnosis by detecting fusion COL1A1-PDGFB transcripts in DFSP, and examined the expression of all FGFRs (FGFR1-4), some of their ligands (FGF1, 2, 9), and forkhead box N1 (FOXN1) as a downstream target of FGFR3 in DF and DFSP by immunohistochemical analysis. Although we failed to detect the expression of FGF1 and FGF9 as specific ligands for FGFR3 in DF, overexpression of FGFR3 and FOXN1 was observed in the epidermal regions of DF, suggesting that the epidermal regions of DF were similar to seborrhoeic keratosis both in terms of histological features and the activation of FGFR3/FOXN1. In addition, strong expression of FGF2 and FGFR4 was observed in the tumor lesions of DF. Expression patterns of FGFR3/FOXN1 and FGF2/FGFR4 in DF were in contrast with those of DFSP. The activation of FGFR signaling pathways may be not only relevant to the pathogenesis of DF, but also very useful in the differential diagnosis of DF and DFSP.

Functional roles of fibroblast growth factor receptors (FGFRs) signaling in human cancers

The fibroblast growth factor receptors (FGFRs) regulate important biological processes including cell proliferation and differentiation during development and tissue repair. Over the past decades, numerous pathological conditions and developmental syndromes have emerged as a consequence of deregulation in the FGFRs signaling network. This review aims to provide an overview of FGFR family, their complex signaling pathways in tumorigenesis, and the current development and application of therapeutics targeting the FGFRs signaling for treatment of refractory human cancers.

A proangiogenic signature is revealed in FGF-mediated bevacizumab-resistant head and neck squamous cell carcinoma

Resistance to antiangiogenic therapies is a critical problem that has limited the utility of antiangiogenic agents in clinical settings. However, the molecular mechanisms underlying this resistance have yet to be fully elucidated. In this study, we established a novel xenograft model of acquired resistance to bevacizumab. To identify molecular changes initiated by the tumor cells, we performed human-specific microarray analysis on bevacizumab-sensitive and -resistant tumors. Efficiency analysis identified 150 genes upregulated and 31 genes downregulated in the resistant tumors. Among angiogenesis-related genes, we found upregulation of fibroblast growth factor-2 (FGF2) and fibroblast growth factor receptor-3 (FGFR3) in the resistant tumors. Inhibition of the FGFR in the resistant tumors led to the restoration of sensitivity to bevacizumab. Furthermore, increased FGF2 production in the resistant cells was found to be mediated by overexpression of upstream genes phospholipase C (PLCg2), frizzled receptor-4 (FZD4), chemokine [C-X3-C motif] (CX3CL1), and chemokine [C-C motif] ligand 5 (CCL5) via extracellular signal-regulated kinase (ERK). In summary, our work has identified an upregulation of a proangiogenic signature in bevacizumab-refractory HNSCC tumors that converges on ERK signaling to upregulate FGF2, which then mediates evasion of anti-VEGF therapy. These findings provide a new strategy on how to enhance the therapeutic efficacy of antiangiogenic therapy.

IMPLICATIONS

Novel xenograft model leads to the discovery of FGF as a promising therapeutic target in overcoming the resistance of antiangiogenic therapy in HNSCC.

Targeted therapy for NSCLC with driver mutations

INTRODUCTION

Activating mutations of the epidermal growth factor receptor (EGFR) gene and rearrangement of anaplastic lymphoma kinase (ALK) gene best illustrate the therapeutic relevance of molecular characterization in non-small cell lung cancer (NSCLC) patients. Several genetic aberrations with a potential prognostic or predictive role have been identified, mainly in adenocarcinoma subtype, including ROS1, RET, MET, HER2, BRAF and KRAS. More recently oncogenic drivers, such as DDR2, FGFR1 and PI3KCA, have been characterized in squamous cell lung carcinoma (SCC) and target agents are currently under evaluation. The aim of this review is to summarize the growing scenario of new targetable oncogenes in NSCLC.

AREAS COVERED

For this review article all published data on NSCLC genomic alterations, including the techniques employed for oncogenic drivers identification, the prevalence of each one in lung cancer subtypes, the preclinical data corroborating their role in tumorigenesis and the potential biological tailored agents tested and under evaluation were collected and analyzed using PubMed.

EXPERT OPINION

Oncogenic products represent reliable targets for drug therapy and the expanding knowledge of molecular pathways involved in lung tumorigenesis is resulting in a dramatic change of treatment strategies leading to an improvement in disease and symptom control, extending life duration and improving quality of life.

The FGF/FGFR axis as a therapeutic target in breast cancer

Fibroblast growth factor receptor (FGFR) signaling is a vital component of both embryonic and postnatal mammary gland development, which has prompted researchers to investigate both its relevance to breast cancer and its potential as a therapeutic target. Deregulated FGFR signaling during breast cancer occurs through various mechanisms, including amplification of the receptor genes, aberrant ligand expression, receptor mutations and translocations. Recent experimental outcomes involving both animal models and human breast cancer cell lines have led to the initiation of multiple early clinical trials investigating the safety and efficacy of small molecule FGFR inhibitors. In this article we review both the most recent discoveries and the need for further investigation of the mechanisms through which FGF/FGFR signaling has emerged as an oncogenic driver.

Interplay between estrogen receptor and AKT in estradiol-induced alternative splicing

Background

Alternative splicing is critical for generating complex proteomes in response to extracellular signals. Nuclear receptors including estrogen receptor alpha (ERα) and their ligands promote alternative splicing. The endogenous targets of ERα:estradiol (E2)-mediated alternative splicing and the influence of extracellular kinases that phosphorylate ERα on E2-induced splicing are unknown.

Methods

MCF-7 and its anti-estrogen derivatives were used for the majority of the assays. CD44 mini gene was used to measure the effect of E2 and AKT on alternative splicing. ExonHit array analysis was performed to identify E2 and AKT-regulated endogenous alternatively spliced apoptosis-related genes. Quantitative reverse transcription polymerase chain reaction was performed to verify alternative splicing. ERα binding to alternatively spliced genes was verified by chromatin immunoprecipitation assay. Bromodeoxyuridine incorporation-ELISA and Annexin V labeling assays were done to measure cell proliferation and apoptosis, respectively.

Results

We identified the targets of E2-induced alternative splicing and deconstructed some of the mechanisms surrounding E2-induced splicing by combining splice array with ERα cistrome and gene expression array. E2-induced alternatively spliced genes fall into at least two subgroups: coupled to E2-regulated transcription and ERα binding to the gene without an effect on rate of transcription. Further, AKT, which phosphorylates both ERα and splicing factors, influenced ERα:E2 dependent splicing in a gene-specific manner. Genes that are alternatively spliced include FAS/CD95, FGFR2, and AXIN-1. E2 increased the expression of FGFR2 C1 isoform but reduced C3 isoform at mRNA level. E2-induced alternative splicing of FAS and FGFR2 in MCF-7 cells correlated with resistance to FAS activation-induced apoptosis and response to keratinocyte growth factor (KGF), respectively. Resistance of MCF-7 breast cancer cells to the anti-estrogen tamoxifen was associated with ERα-dependent overexpression of FGFR2, whereas resistance to fulvestrant was associated with ERα-dependent isoform switching, which correlated with altered response to KGF.

Conclusion

E2 may partly alter cellular proteome through alternative splicing uncoupled to its effects on transcription initiation and aberration in E2-induced alternative splicing events may influence response to anti-estrogens.

FGFR1 amplification in squamous cell carcinoma of the lung

INTRODUCTION

Amplification of fibroblast growth factor receptor 1 (FGFR1) has been reported in squamous cell lung carcinoma and may be a molecular target for therapy. Little is known, however, about the clinical and demographic correlates of FGFR1 amplification.

METHODS

The study is an Institutional Review Board approved retrospective analysis of 226 patients with squamous cell lung cancer seen at the Massachusetts General Hospital from 2005 to 2011. Clinical and demographic characteristics of all patients were obtained, as well as treatment details including surgery, radiation, and chemotherapy, and overall survival. fluorescence in situ hybridization was performed for FGFR1 on formalin-fixed paraffin-embedded tumor tissue. Clinical genotyping results were also reviewed where available.

RESULTS

Thirty-seven of 226 patients (16%) with squamous cell lung cancer were found positive for amplification using a definition of amplification of a gene to copy number control ratio of 2.2 or higher. FGFR1 amplification status was not associated with age, sex, stage, histologic subtype within squamous cell, smoking history, or pack-years of smoking. We found no significant difference in overall survival by FGFR1 amplification status as a whole; in the advanced stage subset, our findings are inconclusive because of the small sample size.

CONCLUSION

FGFR1 amplification was found in 16% of a clinical cohort of squamous cell lung cancer patients. The lack of any specific clinicodemographic features that correlates with FGFR1 amplification suggests that all squamous cell patients should be tested for this genomic change.

An integrative genomic and transcriptomic analysis reveals potential targets associated with cell proliferation in uterine leiomyomas

Background

Uterine Leiomyomas (ULs) are the most common benign tumours affecting women of reproductive age. ULs represent a major problem in public health, as they are the main indication for hysterectomy. Approximately 40–50% of ULs have non-random cytogenetic abnormalities, and half of ULs may have copy number alterations (CNAs). Gene expression microarrays studies have demonstrated that cell proliferation genes act in response to growth factors and steroids. However, only a few genes mapping to CNAs regions were found to be associated with ULs.

Methodology

We applied an integrative analysis using genomic and transcriptomic data to identify the pathways and molecular markers associated with ULs. Fifty-one fresh frozen specimens were evaluated by array CGH (JISTIC) and gene expression microarrays (SAM). The CONEXIC algorithm was applied to integrate the data.

Principal Findings

The integrated analysis identified the top 30 significant genes (P<0.01), which comprised genes associated with cancer, whereas the protein-protein interaction analysis indicated a strong association between FANCA and BRCA1. Functional in silico analysis revealed target molecules for drugs involved in cell proliferation, including FGFR1 and IGFBP5. Transcriptional and protein analyses showed that FGFR1 (P = 0.006 and P<0.01, respectively) and IGFBP5 (P = 0.0002 and P = 0.006, respectively) were up-regulated in the tumours when compared with the adjacent normal myometrium.

Conclusions

The integrative genomic and transcriptomic approach indicated that FGFR1 and IGFBP5 amplification, as well as the consequent up-regulation of the protein products, plays an important role in the aetiology of ULs and thus provides data for potential drug therapies development to target genes associated with cellular proliferation in ULs.

Identification of driver mutations in lung cancer: first step in personalized cancer

Non-small cell lung cancer (NSCLC) has recently been associated with interesting molecular characteristics that have important implications in carcinogenesis and response to targeted therapies. Targeted therapies, if given to a patient subpopulation enriched by the presence of relevant molecular targets, can often abrogate cell signaling that perpetuates cancer progression. For instance, several molecular alterations have been defined as "driver mutations," such as mutations in EGFR and EML4-ALK fusion gene. Other key signaling pathways have also been identified as novel targets for lung cancer treatment. These first steps towards personalized medicine represent a shift in the management of NSCLC. Indeed, NSCLC should no longer be viewed as one common generic tumor but rather as a collection of more rare diseases with different biological behaviors and different sensitivities to targeted treatments. We are now clearly entering an era of personalized medicine for NSCLC cancers, and the development of molecular profiling technologies to assess DNA provides the potential to tailored medical care.

Identification of FGFR4 as a potential therapeutic target for advanced-stage, high-grade serous ovarian cancer

PURPOSE

To evaluate the prognostic value of fibroblast growth factor receptor 4 (FGFR4) protein expression in patients with advanced-stage, high-grade serous ovarian cancer, delineate the functional role of FGFR4 in ovarian cancer progression, and evaluate the feasibility of targeting FGFR4 in serous ovarian cancer treatment.

EXPERIMENTAL DESIGN

Immunolocalization of FGFR4 was conducted on 183 ovarian tumor samples. The collected FGFR4 expression data were correlated with overall survival using Kaplan-Meier and Cox regression analyses. The effects of FGFR4 silencing on ovarian cancer cell growth, survival, invasiveness, apoptosis, and FGF1-mediated signaling pathway activation were evaluated by transfecting cells with FGFR4-specific siRNAs. An orthotopic mouse model was used to evaluate the effect of injection of FGFR4-specific siRNAs and FGFR4 trap protein encapsulated in nanoliposomes on ovarian tumor growth in vivo.

RESULTS

Overexpression of FGFR4 protein was significantly associated with decreased overall survival durations. FGFR4 silencing significantly decreased the proliferation, survival, and invasiveness and increased apoptosis of ovarian cancer cells. Also, downregulation of FGFR4 significantly abrogated the mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), and WNT signaling pathways, which are activated by FGF1. Targeting FGFR4 with the FGFR4-specific siRNAs and FGFR4 trap protein significantly decreased ovarian tumor growth in vivo.

CONCLUSIONS

FGFR4 is a prognostic marker for advanced-stage, high-grade serous ovarian carcinoma. Silencing FGFR4 and inhibiting ligand-receptor binding significantly decrease ovarian tumor growth both in vitro and in vivo, suggesting that targeting ovarian cancer cells with high levels of FGFR4 protein expression is a new therapeutic modality for this disease and will improve survival of it.

Sorting of the FGF receptor 1 in a human glioma cell line

Fibroblast growth factor receptor 1 (FGFR1) is a receptor tyrosine kinase promoting tumor growth in a variety of cancers, including glioblastoma. Binding of FGFs triggers the intracellular Ras/Raf/ERK signaling pathway leading to cell proliferation. Down-regulation of FGFR1 and, consequently, inactivation of its signaling pathways represent novel treatment strategies for glioblastoma. In this study, we investigated the internalization and endocytic trafficking of FGFR1 in the human glioma cell line U373. Stimulation with FGF-2 induced cell rounding accompanied by increased BrdU and pERK labeling. The overexpression of FGFR1 (without FGF treatment) resulted in enhanced phosphorylated FGFR1 suggesting receptor autoactivation. Labeled ligand (FGF-2-Cy5.5) was endocytosed in a clathrin- and caveolin-dependent manner. About 25 % of vesicles carrying fluorescently tagged FGFR1 represented early endosomes, 15 % transferrin-positive recycling endosomes and 40 % Lamp1-positive late endosomal/lysosomal vesicles. Stimulation with FGF-2 increased the colocalization rate in each of these vesicle populations. The treatment with the lysosomal inhibitor leupeptin resulted in FGFR1 accumulation in lysosomes, but did not enhance receptor recycling as observed in neurons. Analysis of vesicle distributions revealed an accumulation of recycling endosomes in the perinuclear region. In conclusion, the shuttling of receptor tyrosine kinases can be directly visualized by overexpression of fluorescently tagged receptors which respond to ligand stimulation and follow the recycling and degradation pathways similarly to their endogenous counterparts.

FGF1-gold nanoparticle conjugates targeting FGFR efficiently decrease cell viability upon NIR irradiation

Fibroblast growth factor receptors (FGFRs) are overexpressed in a wide variety of tumors, such as breast, bladder, and prostate cancer, and therefore they are attractive targets for different types of anticancer therapies. In this study, we designed, constructed, and characterized FGFR-targeted gold nanoconjugates suitable for infrared-induced thermal ablation (localized heating leading to cancer cell death) based on gold nanoparticles (AuNPs). We showed that a recombinant ligand of all FGFRs, human fibroblast growth factor 1 (FGF1), can be used as an agent targeting covalently bound AuNPs to cancer cells overexpressing FGFRs. To assure thermal stability, protease resistance, and prolonged half-life of the targeting protein, we employed highly stable FGF1 variant that retains the biological activities of the wild type FGF1. Novel FGF1 variant, AuNP conjugates are specifically internalized only by the cells expressing FGFRs, and they significantly reduce their viability after irradiation with near-infrared light (down to 40% of control cell viability), whereas the proliferation potential of cells lacking FGFRs is not affected. These results demonstrate the feasibility of FGF1-coated AuNPs for targeted cancer therapy.

Genetic changes in squamous cell lung cancer: a review

Identifying specific somatic mutations that drive tumor growth has transformed the treatment of lung cancer. For example, cancers with sensitizing epidermal growth factor receptor mutations and echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase translocations can have remarkable responses to epidermal growth factor receptor and ALK inhibitors respectively, leading to significant clinical benefit. However, effective molecularly targeted therapies have disproportionately impacted adenocarcinomas compared to squamous cell carcinomas, and never or light smokers compared to heavy smokers. Further progress in non-small-cell lung cancer will require the identification and effective targeting of molecular alterations in all subtypes of lung cancer. Here, we review the current knowledge about the molecular alterations found in squamous cell carcinoma of the lung. First, we will discuss the ongoing efforts to comprehensively assess the squamous cell carcinoma genome. We will then discuss the evidence supporting the role of specific genes in driving squamous cell carcinomas. By describing the landscape of somatic targets in squamous cell lung cancer, we hope to crystallize the current understanding of potential targets, spur development of therapies that can have clinical impact, and underscore the importance of new discoveries in this field.

Disposition and metabolism of 14C-dovitinib (TKI258), an inhibitor of FGFR and VEGFR, after oral administration in patients with advanced solid tumors

PURPOSE

This study investigated the metabolism and excretion of dovitinib (TKI258), a tyrosine kinase inhibitor that inhibits fibroblast, vascular endothelial, and platelet-derived growth factor receptors, in patients with advanced solid tumors.

METHODS

Four patients (cohort 1) received a single 500 mg oral dose of (14)C-dovitinib, followed by the collection of blood, urine, and feces for ≤10 days. Radioactivity concentrations were measured by liquid scintillation counting and plasma concentrations of dovitinib by liquid chromatography-tandem mass spectrometry. Both techniques were applied for metabolite profiling and identification. A continuous-dosing extension phase (nonlabeled dovitinib 400 mg daily) was conducted with the 3 patients from cohort 1 and 9 additional patients from cohort 2.

RESULTS

The majority of radioactivity was recovered in feces (mean 61 %; range 52-69 %), as compared with urine (mean 16 %; range 13-21 %). Only 6-19 % of the radioactivity was recovered in feces as unchanged dovitinib, suggesting high oral absorption. (14)C-dovitinib was eliminated predominantly via oxidative metabolism, with prominent primary biotransformations including hydroxylation on the fluorobenzyl ring and N-oxidation and carbon oxidation on the methylpiperazine moiety. Dovitinib was the most prominent radioactive component in plasma. The high apparent volume of distribution (2,160 L) may indicate that dovitinib distributes extensively to tissues. Adverse events were predominantly mild to moderate, and most common events included nausea, vomiting, constipation, diarrhea, and fatigue.

CONCLUSIONS

Dovitinib was well absorbed, extensively distributed, and eliminated mainly by oxidative metabolism, followed by excretion, predominantly in feces. The adverse events were as expected for this class of drug.

Functional impact bias reveals cancer drivers

Identifying cancer driver genes and pathways among all somatic mutations detected in a cohort of tumors is a key challenge in cancer genomics. Traditionally, this is done by prioritizing genes according to the recurrence of alterations that they bear. However, this approach has some known limitations, such as the difficulty to correctly estimate the background mutation rate, and the fact that it cannot identify lowly recurrently mutated driver genes. Here we present a novel approach, Oncodrive-fm, to detect candidate cancer drivers which does not rely on recurrence. First, we hypothesized that any bias toward the accumulation of variants with high functional impact observed in a gene or group of genes may be an indication of positive selection and can thus be used to detect candidate driver genes or gene modules. Next, we developed a method to measure this bias (FM bias) and applied it to three datasets of tumor somatic variants. As a proof of concept of our hypothesis we show that most of the highly recurrent and well-known cancer genes exhibit a clear FM bias. Moreover, this novel approach avoids some known limitations of recurrence-based approaches, and can successfully identify lowly recurrent candidate cancer drivers.

Endocrine resistance in breast cancer: molecular pathways and rational development of targeted therapies

Endocrine resistance presents a major challenge in the management of estrogen receptor (ER)-positive breast cancer and is an area under intense investigation. Although the underlying mechanism is still poorly understood, many studies point towards the 'cross-talk' between ER and growth factor receptor signaling pathways as the key in the development of estrogen-independent growth in breast cancer. This review aims to provide the reader our current understanding of various molecular pathways that mediate endocrine resistance and that are being evaluated as therapeutic targets for ER-positive breast cancer. While most of the agents that target these pathways have only been tested in Phase I or small Phase II trials, some have shown encouraging results. A critical issue that remains is the development of research strategies and clinical trials that take into account the molecular heterogeneity of ER-positive breast cancer.

Dovitinib demonstrates antitumor and antimetastatic activities in xenograft models of hepatocellular carcinoma

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death. Although sorafenib has been shown to improve survival of patients with advanced HCC, this improvement is modest and patients eventually have refractory disease. This study aims at investigating the antitumor, antiangiogenesis and antimetastatic activities of dovitinib in preclinical models of HCC.

METHODS

21-0208 and SK-HEP1 cells as well as patient-derived HCC models were employed to study the antitumor effect of dovitinib. Changes of biomarkers relevant to FGFR/VEGFR/PDGFR pathways were determined by Western blotting. Microvessel density, apoptosis and cell proliferation were analyzed by immunohistochemistry.

RESULTS

Treatment of SK-HEP1 cells with dovitinib resulted in G2/M cell cycle arrest, inhibition of colony formation in soft agar and blockade of bFGF-induced cell migration. Dovitinib inhibited basal expression and FGF-induced phosphorylation of FGFR-1, FRS2-α and ERK1/2. In vivo, dovitinib potently inhibited tumor growth of six HCC lines. Inhibition of angiogenesis correlated with inactivation of FGFR/PDGFR-β/VEGFR-2 signaling pathways. Dovitinib also caused dephosphorylation of retinoblastoma, upregulation of p-histone H2A-X and p27, and downregulation of p-cdk-2 and cyclin B1, which resulted in a reduction in cellular proliferation and the induction of tumor cell apoptosis. In an orthotopic model, dovitinib potently inhibited primary tumor growth and lung metastasis and significantly prolonged mouse survival.

CONCLUSIONS

Dovitinib demonstrated significant antitumor and antimetastatic activities in HCC xenograft models. This study provides a compelling rationale for clinical investigation in patients with advanced HCC.

FGFR2 genotype and risk of radiation-associated breast cancer in Hodgkin lymphoma

Women treated at young ages with supradiaphragmatic radiotherapy for Hodgkin lymphoma (HL) have a highly increased risk of breast cancer. For personalized advice and follow-up regimens for patients, information is needed on how the radiotherapy-related risk is affected by other breast cancer risk factors. Genome-wide association studies have identified 14 independently replicated common single nucleotide polymorphisms that influence breast cancer risk. To examine whether these variants contribute to risk of radiation-associated breast cancer in HL, we analyzed 2 independent case-control series, from the United Kingdom and The Netherlands, totaling 693 HL patients, 232 with breast cancer and 461 without. rs1219648, which annotates the FGFR2 gene, was associated with risk in both series (combined per-allele odds ratio = 1.59, 95% confidence interval: 1.26-2.02; P = .000111). These data provide evidence that genetic variation in FGFR2 influences radiation-induced breast cancer risk.

Mechanisms of FGFR-mediated carcinogenesis

In this review, the evidence for a role of fibroblast growth factor receptor (FGFR) mediated signalling in carcinogenesis are considered and relevant underlying mechanisms highlighted. FGF signalling mediated by FGFR follows a classic receptor tyrosine kinase signalling pathway and its deregulation at various points of its cascade could result in malignancy. Here we review the accumulating reports that revealed the association of FGF/FGFRs to various types of cancer at a genetic level, along with in vitro and in vivo evidences available so far, which indicates the functional involvement of FGF signalling in tumour formation and progression. An increasing number of drugs against the FGF pathways is currently in clinical testing. We will discuss the strategies for future FGF research in cancer and translational approaches.

Ponatinib (AP24534), a multitargeted pan-FGFR inhibitor with activity in multiple FGFR-amplified or mutated cancer models

Members of the fibroblast growth factor receptor family of kinases (FGFR1-4) are dysregulated in multiple cancers. Ponatinib (AP24534) is an oral multitargeted tyrosine kinase inhibitor being explored in a pivotal phase II trial in patients with chronic myelogenous leukemia due to its potent activity against BCR-ABL. Ponatinib has also been shown to inhibit the in vitro kinase activity of all four FGFRs, prompting us to examine its potential as an FGFR inhibitor. In Ba/F3 cells engineered to express activated FGFR1-4, ponatinib potently inhibited FGFR-mediated signaling and viability with IC(50) values <40 nmol/L, with substantial selectivity over parental Ba/F3 cells. In a panel of 14 cell lines representing multiple tumor types (endometrial, bladder, gastric, breast, lung, and colon) and containing FGFRs dysregulated by a variety of mechanisms, ponatinib inhibited FGFR-mediated signaling with IC(50) values <40 nmol/L and inhibited cell growth with GI(50) (concentration needed to reduce the growth of treated cells to half that of untreated cells) values of 7 to 181 nmol/L. Daily oral dosing of ponatinib (10-30 mg/kg) to mice reduced tumor growth and inhibited signaling in all three tumor models examined. Importantly, the potency of ponatinib in these models is similar to that previously observed in BCR-ABL-driven models and plasma levels of ponatinib that exceed the IC(50) values for FGFR1-4 inhibition can be sustained in patients. These results show that ponatinib is a potent pan-FGFR inhibitor and provide strong rationale for its evaluation in patients with FGFR-driven cancers.

Fibroblast growth factor-2 is an important factor that maintains cellular immaturity and contributes to aggressiveness of osteosarcoma

Osteosarcoma is the most frequent, nonhematopoietic, primary malignant tumor of bone. Histopathologically, osteosarcoma is characterized by complex mixtures of different cell types with bone formation. The role of environmental factors in the formation of such a complicated tissue structure as osteosarcoma remains to be elucidated. Here, a newly established murine osteosarcoma model was used to clarify the roles of environmental factors such as fibroblast growth factor-2 (Fgf2) or leukemia-inhibitory factor (Lif) in the maintenance of osteosarcoma cells in an immature state. These factors were highly expressed in tumor environmental stromal cells, rather than in osteosarcoma cells, and they potently suppressed osteogenic differentiation of osteosarcoma cells in vitro and in vivo. Further investigation revealed that the hyperactivation of extracellular signal-regulated kinase (Erk)1/2 induced by these factors affected in the process of osteosarcoma differentiation. In addition, Fgf2 enhanced both proliferation and migratory activity of osteosarcoma cells and modulated the sensitivity of cells to an anticancer drug. The results of the present study suggest that the histology of osteosarcoma tumors which consist of immature tumor cells and pathologic bone formations could be generated dependent on the distribution of such environmental factors. The combined blockade of the signaling pathways of several growth factors, including Fgf2, might be useful in controlling the aggressiveness of osteosarcoma.

Alternative Splicing of Fibroblast Growth Factor Receptor IgIII Loops in Cancer

Alternative splicing of the IgIII loop of fibroblast growth factor receptors (FGFRs) 1–3 produces b- and c-variants of the receptors with distinctly different biological impact based on their distinct ligand-binding spectrum. Tissue-specific expression of these splice variants regulates interactions in embryonic development, tissue maintenance and repair, and cancer. Alterations in FGFR2 splicing are involved in epithelial mesenchymal transition that produces invasive, metastatic features during tumor progression. Recent research has elucidated regulatory factors that determine the splice choice both on the level of exogenous signaling events and on the RNA-protein interaction level. Moreover, methodology has been developed that will enable the in depth analysis of splicing events during tumorigenesis and provide further insight on the role of FGFR 1–3 IIIb and IIIc in the pathophysiology of various malignancies. This paper aims to summarize expression patterns in various tumor types and outlines possibilities for further analysis and application.

microRNA-99b acts as a tumor suppressor in non-small cell lung cancer by directly targeting fibroblast growth factor receptor 3

microRNAs (miRNAs) play a significant role in cancer development and progression by regulating the expression of proto-oncogenes or tumor suppressor genes. Our previous study using microarrays demonstrated that miR-99b was downregulated in patients with lung cancer. To assess whether or not miR-99b has a functional role in lung cancer, we determined the expression of miR-99b and fibroblast growth factor receptor 3 (FGFR3), which is a predicted target of miR-99b in public algorithms in human lung cancer tissues. miR-99b was downregulated and FGFR3 was upregulated in lung cancer patients. We demonstrated that the overexpression of miR-99b induced a reduction in FGFR3 expression and confirmed the target specificity between miR-99b and the FGFR3 3'-untranslated region by luciferase reporter assay. In addition, the growth rate in miR-99b precursor-treated cells was lower compared to the negative controls. Taken together, these results suggest that miR-99b may be a tumor suppressor through the downregulation of FGFR3. miR-99b may be a potent tumor suppressor and may be a potential therapeutic tool for patients with lung cancer.

The receptor tyrosine kinase FGFR2b/KGFR controls early differentiation of human keratinocytes

The FGFRs trigger divergent responses, such as proliferation and differentiation, and the cell type as well as the context-dependent signaling are crucial for the functional outcome. The FGFR2b/KGFR is expressed exclusively on epithelial cells and plays a key role in skin homeostasis. Here we analyzed in vitro the role of KGFR in the early differentiation of keratinocytes modulating its expression by KGFR cDNA transient transfection or KGFR siRNA microinjection and inducing a synchronous wave of differentiation in pre-confluent cells. Immunofluorescence, biochemical and molecular approaches demonstrated that KGFR overexpression increased the early differentiation marker keratin 1 at both transcriptional and translational levels, while receptor depletion reduced it. Ligand-dependent receptor activation and signaling were required for this differentiative effect. Overexpression of kinase negative KGFR mutant or Tyr769 KGFR signaling mutant, which is not able to recruit and activate PLC-γ, showed that the receptor kinase activity, but not its PLCγ-mediated signaling, is required for differentiation. Reduction of K1 expression, obtained by AKT inhibition, demonstrated that the PI3K/Akt signaling pathway is involved in the control of KGFR-mediated keratinocyte differentiation. This in vitro experimental model indicates that FGFR2b/KGFR expression represents a key event regulating keratinocyte early differentiation during the switch from undifferentiated to differentiating cells.

Anti-VEGF and beyond: shaping a new generation of anti-angiogenic therapies for cancer

The anti-angiogenic class of drugs is one of the few where representatives have gained international approval for clinical use in oncology during the past decade. Most of the biological and clinical activity of the currently available generation of anti-angiogenic drugs targets vascular endothelial growth factor (VEGF) and its related pathways. However, the clinical benefits associated with the use of these drugs have, so far, been limited. There is, therefore, an unmet need for biomarkers that can be used to identify patients who are most likely to benefit therapeutically and also to predict the best schedule and dosage for these drugs. Here, we discuss some of the emerging new combination strategies involving the approved anti-angiogenic drugs, some of the emerging targets associated with neoplastic angiogenesis and some novel agents used as a paradigm of the next generation of anti-angiogenic drugs.

Clathrin- and dynamin-independent endocytosis of FGFR3--implications for signalling

Endocytosis of tyrosine kinase receptors can influence both the duration and the specificity of the signal emitted. We have investigated the mechanisms of internalization of fibroblast growth factor receptor 3 (FGFR3) and compared it to that of FGFR1 which is internalized predominantly through clathrin-mediated endocytosis. Interestingly, we observed that FGFR3 was internalized at a slower rate than FGFR1 indicating that it may use a different endocytic mechanism than FGFR1. Indeed, after depletion of cells for clathrin, internalization of FGFR3 was only partly inhibited while endocytosis of FGFR1 was almost completely abolished. Similarly, expression of dominant negative mutants of dynamin resulted in partial inhibition of the endocytosis of FGFR3 whereas internalization of FGFR1 was blocked. Interfering with proposed regulators of clathrin-independent endocytosis such as Arf6, flotillin 1 and 2 and Cdc42 did not affect the endocytosis of FGFR1 or FGFR3. Furthermore, depletion of clathrin decreased the degradation of FGFR1 resulting in sustained signalling. In the case of FGFR3, both the degradation and the signalling were only slightly affected by clathrin depletion. The data indicate that clathrin-mediated endocytosis is required for efficient internalization and downregulation of FGFR1 while FGFR3, however, is internalized by both clathrin-dependent and clathrin-independent mechanisms.

The driver of malignancy in KG-1a leukemic cells, FGFR1OP2-FGFR1, encodes an HSP90 addicted oncoprotein

The KG-1a cell line is developed from a human stem cell myeloproliferative neoplasm as the result of intragenic disruption and a chromosomal translocation of the FGFR1 gene and the FGFR1OP2 gene encoding a protein of unknown function called FOP2 (FGFR1 Oncogene Partner 2). The resulting fusion protein FOP2-FGFR1 is soluble and has constitutive tyrosine kinase activity. Since the heat shock protein HSP90 and its co-chaperone CDC37 have been shown to stabilize many oncogenic proteins, we investigated the requirement for HSP90 or HSP90-CDC37 assistance to maintain the stability or activity of FOP2-FGFR1 expressed in KG-1a cells. We found that HSP90-CDC37 forms a permanent complex with FOP2-FGFR1. This results in protection against degradation of FOP2-FGFR1 and holds the oncoprotein in a permanently active conformation. Inhibition of HSP90 or depletion of CDC37 or heat shock factor 1 (HSF1) reduced the expression level of FOP2-FGFR1 and was sufficient to block the oncoprotein induced proliferation of KG-1a cells. We conclude that the driver of malignancy in KG-1a leukemic cells, FOP2-FGFR1, is an HSP90 addicted oncoprotein. This provides a rationale for the therapeutic use of HSP90 inhibitors in myeloid leukemias that contain FGFR fusion proteins.

Fibroblast growth factor receptors are components of autocrine signaling networks in head and neck squamous cell carcinoma cells

PURPOSE

We previously reported that a fibroblast growth factor (FGF) receptor (FGFR) signaling pathway drives growth of lung cancer cell lines of squamous and large cell histologies. Herein, we explored FGFR dependency in cell lines derived from the tobacco-related malignancy, head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

FGF and FGFR mRNA and protein expression was assessed in nine HNSCC cell lines. Dependence on secreted FGF2 for cell growth was tested with FP-1039, an FGFR1-Fc fusion protein. FGFR and epidermal growth factor receptor (EGFR) dependence was defined by sensitivity to multiple inhibitors selective for FGFRs or EGFR.

RESULTS

FGF2 was expressed in eight of the nine HNSCC cell lines examined. Also, FGFR2 and FGFR3 were frequently expressed, whereas only two lines expressed FGFR1. FP-1039 inhibited growth of HNSCC cell lines expressing FGF2, identifying FGF2 as an autocrine growth factor. FGFR inhibitors selectively reduced in vitro growth and extracellular signal-regulated kinase signaling in three HNSCC cell lines, whereas three distinct lines exhibited responsiveness to both EGFR and FGFR inhibitors. Combinations of these drugs yielded additive growth inhibition. Finally, three cell lines were highly sensitive to EGFR tyrosine kinase inhibitors (TKI) with no contribution from FGFR pathways.

CONCLUSIONS

FGFR signaling was dominant or codominant with EGFR in six HNSCC lines, whereas three lines exhibited little or no role for FGFRs and were highly EGFR dependent. Thus, the HNSCC cell lines can be divided into subsets defined by sensitivity to EGFR and FGFR-specific TKIs. FGFR inhibitors may represent novel therapeutics to deploy alone or in combination with EGFR inhibitors in HNSCC.

Somatic mutation of fibroblast growth factor receptor-3 (FGFR3) defines a distinct morphological subtype of high-grade urothelial carcinoma

FGFR3 mutations are common in low-grade urothelial carcinoma and represent a potential therapeutic target in this disease. Their incidence and functional role in high-grade urothelial carcinoma (HGUC), which displays an increased propensity for recurrence and muscularis propria invasion, is less well defined. We developed a mass spectrometry-based genotyping assay to define the incidence of FGFR3 mutations in a large clinically annotated set of urothelial carcinomas. FGFR3 mutations were found in 17% of HGUC versus 84% of low-grade lesions. Retrospective pathological review of the class of FGFR3 mutant HGUC revealed unique histological features, characterized by a bulky, exophytic component with branching papillary architecture as well as irregular nuclei with a koilocytoid appearance. The predictive value of this histological appearance was confirmed using a prospective set of 49 additional HGUCs. Prospective histological review was able to correctly predict for the presence of an FGFR3 mutation in 13/24 HGUC specimens that exhibited the distinct morphology (54%). All 25 specimens lacking the defined histological features were FGFR3 wild-type for a negative predictive value of 100%. Macrodissection of individual tumours confirmed the presence of the FGFR3 mutant allele in non-invasive and invasive, low and high-grade regions of individual tumours and in the lymph node metastases of patients whose tumours possessed the characteristic morphological signature, suggesting that FGFR3 mutations are not restricted to the more clinically indolent regions of HGUCs. These data suggest that histological screening of HGUCs followed by confirmatory genotyping can be used to enrich for the population of HGUCs most likely to harbour activating mutations in the FGFR-3 receptor tyrosine kinase. Histological review could thus aid in the development of targeted inhibitors of FGFR-3 by facilitating the identification of the subset of patients most likely to harbour activating mutations in the FGFR3 gene.

Targeting fibroblast-growth-factor-receptor-dependent signaling for cancer therapy

INTRODUCTION

Fibroblast growth factors (FGF) exert a combination of biological effects that contribute to four of the six essential hallmarks of cancer. It is no surprise that FGF-dependent signaling has increasingly moved to the center of cancer therapy research during the past decade. This is illustrated by the large number of publications focusing on various aspects of this theme that have been published in the past 5 years.

AREAS COVERED

Information from these sources as well as ongoing work from the authors' groups is used to outline the physiological functions of FGF signaling and to highlight how the high oncogenic effects of deregulated FGFs and FGFRs derive from their physiological functions. The biological effect of deregulated FGFR signaling in malignant diseases is described and the current state of therapeutic targeting of FGFR is summarized.

EXPERT OPINION

Strategies for targeting FGFR-signaling for cancer therapy are very promising, but need to be carefully developed based on the physiological roles of FGF signaling. Preventive measures may be necessary for protection from FGF-related side effects. Combined targeting of several receptor tyrosine kinases or combination with other therapies may be a useful way of avoiding or ameliorating side effects. FGF-related markers of prognosis and therapy response still need to be investigated.