FGFR-4

FGFR4 is the principal receptor for the endocrine growth factor FGF19 and signals through the FGFR4-Klotho beta co-receptor complex on hepatocytes. The FGF19-FGFR4 axis suppresses bile acid synthesis by downregulating CYP7A1, and it also modulates glucose and lipid metabolism, making this pair a focus in metabolic liver disease. Constitutive pathway activation occurs in hepatocellular carcinoma, and FGFR4 overexpression or FGF19 amplification correlates with aggressive tumors; FGFR4 is additionally implicated in rhabdomyosarcoma, where the Gly388Arg polymorphism has been studied. Liver-selective FGFR4 inhibitors such as fisogatinib have entered clinical trials for HCC, and recombinant FGFR4 supports these drug-discovery efforts.