FGFR

FGFRs are transmembrane receptor tyrosine kinases for fibroblast growth factors, and four FGFRs possess intracellular protein-tyrosine kinase activity^[1]. Mechanistically, FGFR signaling activates MAPK, JNK, β-catenin, and related transcriptional programs that regulate proliferation, differentiation, survival, migration, and organogenesis^[2][3][4]. In developmental models, FGFR1 supports neurulation and limb development, whereas FGFR2IIIb controls mesenchymal-epithelial signaling during early organogenesis^[5][6]. In epithelial and cancer models, isoform context strongly changes biological output: FGFR1-IIIb induces proliferation through p44/42 MAP kinase and JNK pathways, FGFR2IIIb differs from FGFR2IIIc in ligand-binding specificity and tissue distribution, and FGFR4 mediates FGF19 signaling to the prolactin promoter^[2][6][7]. Disease relevance also differs by isoform, because FGFR3 mutations account for achondroplasia, hypochondroplasia, and thanatophoric dwarfism, while FGFR4 overexpression associates with poor survival in high-grade serous ovarian carcinoma^[8][9]. For experimental applications, FGFR inhibitors such as erdafitinib, infigratinib, futibatinib, and fisogatinib provide tools to interrogate kinase-dependent FGFR signaling and FGFR-driven cancers^[1][10].