FGF9 and urinary bladder cancer: Fibroblast cytokine 9 (FGF9) is overexpressed in many cancer cells (Ren et al., 2016; Mizukami et al., 2017), and its targeted receptor FGFR3c is an important driver of bladder cancer progression (Iyer and Milowsky, 2013; Wang et al., 2020).