Fibroblast Growth Factor Axis Research Articles

Levels of Circulating Fibroblast Growth Factor 23 (FGF23) and Prognosis in Cancer Patients with Bone Metastases.

The fibroblast growth factor (FGF) signaling pathway plays a key role in tumorigenesis and is recognized as a potential therapeutic target. In this study, the authors aimed to assess the impact of serum FGF23 levels in the prognosis of patients with cancer and bone metastases from solid tumors. A cohort of 112 patients with cancer and metastatic bone disease were treated with bone-targeted agents (BTA). Serum baseline FGF23 was quantified by ELISA and dichotomized in FGF23high and FGF23low groups. Additionally, the association between FGF23 and overall survival (OS) and time to skeletal-related events (TTSRE) was investigated. Baseline characteristics were balanced between groups, except for the median urinary N-terminal telopeptide (uNTX) level. After a median follow-up of 26.0 months, a median OS of 34.4 and 12.2 months was found in the FGF23low and FGF23high groups, respectively (multivariate HR 0.18, 95% CI 0.07–0.44, p = 0.001; univariate HR 0.27, p = 0.001). Additionally, TTSRE was significantly longer for patients with FGF23low (13.0 vs. 2.0 months, p = 0.04). Overall, this study found that patients with FGF23low at baseline had longer OS and TTSRE. Further studies are warranted to define its role as a prognostic biomarker and in the use of drugs targeting the FGF axis.

MS25.05 Targeting the Micro-RNA: A New Therapeutic Venture

MS25.05 Targeting the Micro-RNA: A New Therapeutic Venture

Abstract A026: Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer progression

Abstract Bone metastases typically develop in patients with advanced prostate cancer (PCa). Androgen deprivation is commonly used as treatment, but responses are short, and eventually the disease progresses to a castration-resistant form (CRPC). The fibroblast growth factor (FGF) axis is commonly altered during PCa progression. Our group and others have implicated the FGF axis in the pathogenesis of PCa progression in bone, identified it as a candidate target for therapy, and suggested that FGF receptor (FGFR)-1 mediates a positive feedback loop between PCa cells and bone cells. RNA sequencing studies of 183 human PCa samples indicated that the mean expression of FGFR-1 is the highest of all the FGFR family genes studied. Analyses of these FGFR-1 transcripts identified eight different protein-coding transcripts to be the most abundantly expressed with diverse human PCa tissue samples expressing different FGFR-1 isoforms. The overall goal of this project is to investigate implications of FGFR1/FGFR1 isoforms expression in the pathogenesis of PCa bone metastases. When we assessed the expression of the two best-characterized FGFR-1 isoforms (alpha (NM_023110.2) and beta (NM_023105.2), which represent the most abundant protein coding transcripts found in PCa, we observed that all patient-derived xenografts (PDXs) studied express significantly higher levels of FGFR-1 alpha than beta while PCa cell lines mostly express the beta isoform. Mining The Cancer Genome Atlas (TCGA) PCa data, we identified distinct patterns of gene expression associated with each FGFR-1 isoform (alpha and beta). Briefly, FGFR-1 beta (but not alpha) is significantly associated with pathways including the MAP-kinase signaling cascade, signaling by FGFR in disease and pathways in cancer. In vitro studies of FGF signaling activation in PCa cells expressing FGFR-1 isoforms alpha, beta or empty vector, confirmed these results. Male SCID mice injected intracardially with PC3-FGFR-1 alpha exhibited higher death rates compared to animals injected with either PC3-FGFR-1 beta or PC3-empty vector. Furthermore, higher number of metastases per mice as well as higher number of mice with bone metastases were observed in animals injected with PC3-FGFR-1 alpha. The fact that different prostate tumors express different FGFR-1 isoforms suggests that FGFR1 alpha and beta isoforms activate different genes or pathways in PCa cells and this may underlie, at least in part, PCa heterogeneity, pattern of progression, and differences in response to FGFR1 inhibitors. Further studies will warrant the understanding of the implications of FGFR-1 isoforms expression in the pathogenesis of PCa. Citation Format: Estefania Labanca, Jun Yang, Peter Shepherd, Justin Roberts, Michael Starbuck, Bradley Broom, Matthew Iyer, Christopher Logothetis, Arul Chinnaiyan, Nora Navone. Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer progression [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A026.

Abstract 2870: A specific pan-FGFR inhibitor has antitumor activity against prostate cancer patient derived xenografts, PDX, expressing high FGFR1

Abstract Prostate Cancer (PCa) is one of the most commonly diagnosed malignancies in men. Patients with advanced metastatic PCa have effective treatment options, but none of them are curative. Androgen deprivation is the most effective therapy, but growth of the cancer resumes over time in most cases, and the disease progresses to castration-resistant PCa (CRPC). Bone is the main site of CRPC progression. Acquired (or inherent) resistance mechanisms to second line therapy options for CRPC eventually lead to disease recurrence and, ultimately, death. The underlying mechanisms of PCa progression to first or second line therapy options are diverse and include fibroblast growth factor (FGF) axis activation. Indeed, we previously reported that blockade of FGFRs with dovitinib (TKI258) (Novartis Pharmaceuticals), a receptor tyrosine kinase inhibitor (TKI) with potent activity against FGFR1-3 and vascular endothelial growth factor receptor (VEGFR) has clinical activity in men with CRPC and bone metastases (PMID: 25186177), thus providing direction for therapy development of FGFR blockade in PCa. Because dovitinib was withdrawn from the clinic by Novartis, we seek to identify an alternative agent with activity against FGFR1 as a candidate for therapy development. With that goal, we tested the antitumor activity of a specific pan-FGFR TKI, JNJ-42756493 (JNJ) (Janssen Pharmaceutical Companies of Johnson&Johnson) against PCa patients derived xenografts (PDXs) expressing high (MDA PCa 118b) and low (MDA PCa 183) endogenous levels of FGFR1. Because bone is the primary site of CRPC progression we tested the antitumor activity of JNJ against these PDXs growing in the bone of mice. By assessing tumor volume by MRI, we found that JNJ has antitumor activity against MDA PCa 118b but not MDA PCa 183. Immunohistochemical analysis of FGFR1 expression exhibited reduction of FGFR1 in tumors of the treated group compared with vehicle treated group in MDA PCa 118b samples. Both these evidences suggest that FGFR1 is the main driver of PCa progression in this PDX and that JNJ is a potent agent against PCas with high FGFR1 expression.Due to the important role that FGF axis has in bone biology, we assessed the effect of JNJ in the bones of mice without tumors by micro-CT analysis. Interestingly, we observed a reduction in bone parameters including bone volume/ total volume (BV/TV) and trabecular thickness (Tb.Th) in the treated group compared with the vehicle treated group, suggesting FGF axis blockade reduces bone mass. However, we identified an increase in the bone surrounding the tumors in the MDA PCa 118b tumor-bearing bones of mice treated with JNJ. These results highlight the complex role of FGF axis in the PCa-bone interaction and warrant further studies to identify candidate patients for this therapy and markers of response in men treated with FGFR inhibition. Citation Format: Estefania Labanca, Jun Yang, Peter Shepherd, Xinhai Wan, Justin M. Roberts, Michael W. Starbuck, Nora M. Navone. A specific pan-FGFR inhibitor has antitumor activity against prostate cancer patient derived xenografts, PDX, expressing high FGFR1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2870.

A link between the fibroblast growth factor axis and the miR-16 family reveals potential new treatment combinations in mesothelioma.

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with very limited therapeutic options. Fibroblast growth factor (FGF) signals play important roles in mesothelioma cell growth. Several FGFs and FGF receptors (FGFRs) are predicted targets of the miR‐15/16 family, which is downregulated in MPM. The aim of this study was to explore the link between the miR‐15/16 family and the FGF axis in MPM. Expression analyses via RT‐qPCR showed downregulation of the FGF axis after transfection with miR‐15/16 mimics. Direct interaction was confirmed by luciferase reporter assays. Restoration of miR‐15/16 led to dose‐dependent growth inhibition in MPM cell lines, which significantly correlated with their sensitivity to FGFR inhibition. Treatment with recombinant FGF2 prevented growth inhibition and further reduced the levels of FGF/R‐targeting microRNAs, indicating a vicious cycle between miR‐15/16 down‐ and FGF/FGFR signaling upregulation. Combined inhibition of two independent miR‐15/16 targets, the FGF axis and Bcl‐2, resulted in additive or synergistic activity. Our data indicate that post‐transcriptional repression of FGF‐mediated signals contributes to the tumor suppressor function of the microRNA‐15/16 family. Inhibiting hyperactivated FGF signals and Bcl‐2 might serve as a novel therapeutic combination strategy in MPM.

Evidence for distinct alterations in the FGF axis in prostate cancer progression to an aggressive clinical phenotype

Multiple fibroblast growth factor (FGF) axis alterations are known to occur in prostate cancer. Here we simultaneously profiled key components of this axis to determine their relevance in disease progression. An optimized immunohistochemistry protocol was used in expression analysis of FGF2, FGF8, FGFR1, FGFR4, and Sef (similar expression to FGF) in a single TMA of prostate cancer. FGF ligands and receptors were overexpressed in cancers compared to benign samples (p < 0.0001), while Sef expression was reduced (p < 0.0001). There was a positive association between higher grades and increased FGFR4 (p = 0.02), FGF2, and FGF8 (p = 0.002 and p < 0.0001). Sef expression was progressively lower with increasing grade (p = 0.005). Clinical stage was positively associated with FGF2, FGF8, and FGFR4 expression (p = 0.005, 0.03, and 0.012) but not with FGFR1 or Sef expression. Only reduced Sef was associated with bone metastasis (p = 0.02) and was also predictive of subsequent metastasis in initially localized tumours (p = 0.004). Down-regulation of Sef and increased FGFR4 were also the only independent variables associated with disease-specific survival (HR 1.73, p = 0.04 and HR 0.56, p = 0.01). In in vitro studies, silencing Sef enhanced the cell response to FGFs (p < 0.001) and substantially mitigated the effectiveness of an FGFR1 inhibitor. Conversely, increased Sef blocked the response to FGFs and had a comparable suppressive effect to the inhibitor. This study demonstrates that increased FGFR4 and reduced Sef may be critical FGF alterations associated with prostate cancer progression. Sef may also have a role in the tumour response to FGFR inhibition and warrants further investigation in this context.

Adenovirus-mediated expression of dominant negative fibroblast growth factor (FGF) receptor 1 in thyroid cells blocks FGF effects and reduces goitrogenesis in mice.

Levels of fibroblast growth factor 2 (FGF-2) and its receptor, FGFR1, are elevated in goiter, but whether this is a direct effect of TSH is unknown. We have determined the regulation of FGF-2 and FGFR1 synthesis by TSH in a rat thyroid cell line (FRTL5) and have used a replication-defective adenovirus (RAd) expressing dominant negative FGFR1 (RAdDN-FGFR1) to examine the role of FGFR signaling in vitro and in goiter induced in mice. TSH induced FGF-2 and increased the expression of FGFR1 in FRTL5 cells. Infection of TSH-stimulated FRTL5 cells with RAdDN-FGFR1 inhibited growth and prevented FGF-2-mediated inhibition of (125)I uptake. Similar effects were found in primary cultures of human thyroid follicular cells. For in vivo experiments, male BALB/c mice were injected systemically with RAdDN-FGFR1 or RAd encoding green fluorescent protein, and goiter was simultaneously induced. Mouse thyroid follicles were shown to be transduced with RAd encoding green fluorescent protein. Circulating TSH was elevated comparably in the two groups. In the RAdDN-FGFR1-injected animals, goiter induced over 14 d was significantly smaller, and the vascular volume increase seen in goiter was also diminished. We conclude that the FGF axis is important in thyroid growth and that RAdDN-FGFR1 effectively blocks FGF actions, offering a means to control goitrogenesis.

Differential expression of specific FGF ligand and receptor isoforms during angiogenesis associated with prostate cancer progression.

The aim of this study was to elucidate how changes in temporal and spatial expression patterns of individual components of the fibroblast growth factor (FGF) signaling axis correlate with prostate cancer-associated angiogenesis to contribute to the progression of this disease. The temporal and spatial expression patterns of specific FGF ligands and receptors were characterized by immunoblot, in situ hybridization, and immunohistochemical analyses in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. We detected expression of high molecular weight isoform of FGF-2 in PIN lesions and detected both high and low molecular weight isoforms of FGF-2 in advanced tumors. Expression of the mRNA encoding the FGFR1iiib isoform was found to be specifically and differentially expressed in tumor vasculature in TRAMP but was not detected in prostate-associated vasculature in nontransgenic mice. Expression of the FGFR2iiic isoform was observed to be elevated in the epithelial component of PIN lesions in TRAMP mice. By using the TRAMP model, the expression of FGFR1iiib in intraductal vasculature and expression of FGF-2 protein were found to be concomitant with the emergence of PIN. These observations implicate specific changes in the FGF axis with the initiation and progression of prostate cancer and underscore the utility of animal models to identify specific molecular changes in early disease.

Characterization of the FGF axis and identification of a novel FGFR1iiic isoform during prostate cancer progression in the TRAMP model.

Expression of the fibroblast growth factor (FGF) axis was examined during prostate cancer progression in the autochthonous Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model, including TRAMP derived cell lines. Transcripts for FGF-7 and FGF-10 that are normally expressed by the stroma were detected in all samples, including the epithelial cell lines, suggesting that elaboration of these factors by the epithelium may be an essential event during transformation. Interestingly FGFR2iiib, the FGF-7 and FGF-10 receptor, was downregulated during tumor progression whereas a novel FGFR1iiic (Phi) inframe splice form was found to be expressed. These observations support the hypothesis that specific changes in FGF axis correlate with, and probably facilitate, tumor progression.

Peptide growth factors and prostate cancer: new models, new opportunities.

Prostate cancer is the leading form of newly diagnosed cancer cases in men in the United States. However, the molecular mechanisms contributing to the initiation, progression and ultimate development of metastatic and androgen independent disease are poorly understood. This is due in part to the difficulty in obtaining clinical samples representing early disease and the lack of animal models that recapitulate the full spectrum of the clinical disease. To this end we have developed and characterized the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) animal model that expresses the oncogene SV40 T antigen specifically in the epithelium of the prostate. TRAMP develops spontaneous autochthonous prostate cancer compelte with distant site metastasis and can progress to androgen independent disease. Changes in the fibroblast growth factor (FGF) axis and the insulin-like growth factor (IGF) axis have been examined during prostate cancer progression utilizing the TRAMP model and these data generally support observations reproted in the clinical disease. Moreover, we report novel changes in the FGF axis and IGF axis utilizing TRAMP. Thus, TRAMP can be used as a potent tool in understanding the mechanism of prostate cancer initiation and progression.