Abstract 2637: Novel targeted therapy-resistant FGFR3 splice variant increases oncogenic phenotype in African American prostate cancer

Abstract

Abstract Introduction: In this study, we investigate the role of alternative splicing in the receptor tyrosine kinase family on prostate cancer health disparities in African American men. Background: Prostate cancer (PCa) is the most diagnosed cancer in men and the second leading cause of male-cancer related deaths in the U.S. Dramatic ethnic disparities have been observed in PCa patients, as African American (AA) men are 60% more likely to be diagnosed with PCa and have a 2.4 fold higher mortality rate compared to European American (EA) men. Increasing evidence suggests that, after accounting for epidemiological factors, a remaining component of this disparity is due to intrinsic genetic and biological factors. Interestingly, exon array data from our lab suggest that differential alternative splicing (dAS) may be occurring in AA PCa. We hypothesize that dAS involving exon 14 of FGFR3 is generating a shorter, more oncogenic variant in AA PCa, which is absent or weakly expressed in EA PCa. Differential splicing of FGFR3 in AA patients may be mechanisms contributing to AA PCa health disparities. Results: Cloning confirmed the presence of the FGFR3-L variant (containing exon 14) and the FGFR3-S variant (without exon 14) from EA and AA PCa cell lines, respectively. RNA-seq data analysis suggests decreased survival of PCa patients with high FGFR3-S/-L expression ratios. EA cell lines overexpressing FGFR3-S show increased small molecule inhibitor (SMI) TKI258-mediated resistance to proliferation, invasion, and apoptosis in vitro. Additionally, mice injected with cells overexpressing FGFR3-S have increased tumor growth, metastasis, and resistance to TKI258 treatment. Conclusions: We have identified an oncogene of interest, FGFR3, which undergoes exon skipping specific to AA PCa. We have successfully cloned this novel FGFR3 variant in cell lines and created stable cell lines overexpressing both short and long variants. In vitro and in vivo studies suggest FGFR3-S is more resistant to SMIs. Thus, dAS in FGFR3 may be one mechanism contributing to the increased aggressiveness of PCa in AA patients. Citation Format: Jacqueline Moy, Bi-Dar Wang, Norman H. Lee. Novel targeted therapy-resistant FGFR3 splice variant increases oncogenic phenotype in African American prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2637.