Abstract 4781: Changes in intracellular signaling following chronic FGFR inhibition in urothelial bladder cancer models

Abstract

Abstract Preclinical and clinical studies have validated the therapeutic potential of FGFR inhibition in urothelial bladder cancer (UBC) patients with FGFR genetic aberrations. Rogaratinib is a potent small-molecule pan-FGFR inhibitor being studied in phase I trials in UBC. Here, we studied the effects of chronic exposure of bladder cancer cells in vitro to FGFR inhibition by rogaratinib to identify changes in signaling and gene expression patterns that may identify possible drug combinations that may enhance efficacy of rogaratinib and help overcome inherent and/or acquired treatment resistance. Cell proliferation in response to rogaratinib was evaluated using crystal violet staining in a panel of 13 UBC cell lines. Continuous culture of two cell lines–JMSU1 and RT112–with either constant or increasing concentrations of rogaratinib in several independent approaches generated the resistant sublines, JMSU1-R1 to -R4 and RT112-R1 to -R4. In both cellular models rogaratinib resistance (defined as >30-fold [JMSU1] or >100-fold [RT112] difference in absolute IC50 of sublines vs. parental lines) arose reproducibly and with various treatment schedules. Morphologic changes were also observed. Transcriptomic (RNAseq) and proteomic (R&D Systems proteome profiler arrays) analyses of these cell lines or rogaratinib-treated versus untreated parental cells, respectively, revealed changes that co-occur with the development of resistance. Analysis of the phospho-proteome showed increased phosphorylation of several receptor tyrosine kinases compared to the parental cell lines. Phosphorylation levels varied among the 4 resistant sublines that were derived from the same parental line. This resulted in alteration of downstream signaling pathways in rogaratinib-treated sublines compared to parental cell lines. In conclusion, exposure of selected bladder cancer cell lines to rogaratinib resulted in development of resistance and changes in FGFR signaling and gene expression pathways that may identify strategies to optimize treatment with FGFR inhibitors. Citation Format: Isabel S. Jerchel, Atanas Kamburov, Ralf Lesche, Sabine Zitzmann-Kolbe, Alexander Walter, Peter Ellinghaus, Dominik Mumberg, Oliver Politz, Sylvia Gruenewald. Changes in intracellular signaling following chronic FGFR inhibition in urothelial bladder cancer models [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 4781.