Family with sequence similarity 3 member B (FAM3B)

Family with sequence similarity 3 member B (FAM3B), also known as PANDER (Pancreatic-derived factor), is a secreted cytokine-like protein with distinct structural features, differing from classical cytokines. FAM3B is expressed most notably in pancreatic islet beta cells, where it is co-secreted with insulin in response to glucose. It acts as a direct ligand for fibroblast growth factor receptors (FGFR1–4), activating the FGFR/ERK signaling cascade; its functions include modulation of glucose and lipid metabolism, induction of apoptosis in pancreatic alpha and beta cells, and regulation of anterior–posterior axis formation in embryonic development. Overexpression or dysregulation of FAM3B is implicated in the pathogenesis of type 2 diabetes (by impairing beta-cell survival and promoting hepatic gluconeogenesis), as well as in the progression of certain cancers. FGFR inhibitors have been shown to block FAM3B-mediated signaling and are under clinical investigation for FGFR-driven diseases, highlighting potential therapeutic relevance.

Other names

PANDERPancreatic-derived factorC21orf11C21orf76D21M16SJHU19ePRED44UNQ320/PRO365ORF9Cytokine-like protein 2-21protein FAM3Bfamily with sequence similarity 3 member B

As a ligand, FAM3B directly binds and activates fibroblast growth factor receptors (FGFR1–4), leading to downstream ERK pathway activation. FGFR inhibitors block FAM3B-induced signaling and effects.