Fibroblast growth factor receptor 4 (FGFR4) expression as a prognostic indicator in high-grade serous ovarian carcinoma (HGSC): Signaling pathway, mechanism, and implication for therapeutic targeting.

Abstract

5049 Background: Poor survival associated with the amplicon 5q31-35(previously reported) in HGSC may be due to subsequent overexpression of FGFR4. This work aims to correlate FGFR4 with survival in HGSC, identify its role, molecular mechanism & test feasibility of therapeutic targeting. Methods: QT-PCR validated amplification of FGFR4 on 5q31-35 in 52 cases. IHC quantified FGFR4 expression in 181 patients. Western blots(WB) quantified FGFR4 expression in HGSC cell lines. Role of FGFR4 in proliferation, survival, migration and invasion potential of HGSC in vitro was quantified in HGSC cells transfected with FGFR4 siRNA and control scramble sequence siRNA. HGSC cell lines expressing response elements linked to luciferase were treated with Fibroblast growth factor 1(FGF1) in the presence and absence of FGFR4 siRNA or FGFR4 trap protein to identify relevant pathways. Reverse phase protein array analysis and WB were also performed on HGSC cell lines subjected to similar treatments. Mutational analysis on FGFR4was performed in 43 HGSC samples. Results: FGFR4 staining intensity correlated with poor OS in HGSC patient (median survival 28 vs 55 months p<0.001) and increase risk of death (HR 1.22 p<0.001). FGFR4 was over-expressed in HGSC cell lines compared to ovarian surface epithelium. FGFR4 and FGF1 DNA copy number were significantly correlated (r=0.4, p=0.04). Significant decreases in cell proliferation (p<0.001), survival (p<0.01) and migration (p<0.05) were noted in cells treated with FGFR4 siRNA compared to controls. RPPA, the luciferase reporter assay and western blot analysis demonstrated activation of multiple pathways (MAPK,WNT and NFkB) in response to FGF1 but the effect was inhibited by silencing FGFR4 or by FGFR4 trap treatment. Sequencing of FGFR4 did not reveal mutations. Conclusions: Over-expression of FGFR4 is associated with poor survival in late stage HGSC. In vitro data provides evidence that binding of ligand to FGFR4 activates multiple signaling pathways leading to a more aggressive phenotype. Targeting FGFR4 over-expression in HGSC may be a therapeutic strategy with potential for improving survival in HGSC.