FGFR3 is a receptor tyrosine kinase activated upon binding of the FGF ligand, which activates RAS-MAPK and PI3K-AKT pathways. Altered function of FGFR3 in cancer may lead to increased cell proliferation and decreased apoptosis. Simple variants in FGFR3 are seen in about 8% of all tumors, including 35% of urinary tract tumors and 13% of skin tumors. A Phase II study has shown response to FGFR inhibitors in bladder cancer.