The Role of FGFR3 in the Progression of Bladder Cancer

<b>Introduction:</b> Bladder cancer is associated with a high recurrence rate, and outcomes for muscle-invasive and metastatic disease remain poor. New targeted therapies, such as the FGFR inhibitor erdafitinib, have been introduced, but the progression from non-muscle-invasive to muscle-invasive disease remains a major clinical challenge. <b>Methods:</b> In this study, we performed immunohistochemical staining for FGFR1-FGFR4 on surgical specimens from 192 cases of urothelial carcinoma. We also conducted various functional assays on human bladder cancer cell lines to assess protein/gene expression, cell proliferation, migration, invasion, and colony formation. <b>Results:</b> FGFR2 and FGFR3 expressions were found to be significantly down-regulated in high-grade (0.014) and muscle-invasive (0.002) tumors, respectively. Functionally, the FGFR inhibitor erdafitinib suppressed cell proliferation and migration, and FGFR3 silencing also markedly reduced proliferation, migration, invasion, and colony formation in cancer cell lines. <b>Conclusions:</b> The down-regulation of FGFR3 in muscle-invasive bladder cancer, coupled with the inhibitory effect of its inactivation on cell growth, suggests a significant role for FGFR3 in bladder cancer progression.