title: Inhibition of fibroblast growth factor 19 reduces tumor growth by modulating beta-catenin signaling.
abstract: Fibroblast growth factors (FGF) play important roles in development, angiogenesis, and cancer. FGF19 uniquely binds to FGF receptor 4 (FGFR4). Our previous study has shown that FGF19 transgenic tumors have an activated Wnt-pathway phenotype. Wnt signaling is implicated in initiating or promoting FGF signaling in various cell types and organs. In this study, we examined whether FGF19 or inhibition of FGF19 affects the beta-catenin signaling pathway using human colon cancer cell lines (HCT116, Colo201). Our results show that FGF19 increases tyrosine phosphorylation of beta-catenin and causes loss of beta-catenin-E-cadherin binding. FGF19 increases p-GSK3beta and active beta-catenin levels and anti-FGF19 antibody (1A6) treatment abrogates this effect of FGF19. Anti-FGF19 antibody treatment increases S33/S37/T41 phosphorylation and ubiquitination of beta-catenin. Ion-trap mass spectrometric analysis confirmed that 1A6 increases phosphorylation of beta-catenin in the NH(2) terminus. Using HCT116-paired beta-catenin knockout cells, we show that FGF19 induces TCF/LEF reporter activity in parental (WT/Delta45) and in WT/--but not in mutant (-/Delta45) cells, and that inhibition of endogenous FGF19 reduces this reporter activity, indicating that wild-type beta-catenin is accessible for modulation. FGFR4 knockdown using inducible short hairpin RNA significantly reduces the colony-forming ability in vitro and tumor growth in vivo. Although cleaved caspase-3 immunoreactivity remains unchanged, the number of ki67-positive nuclei is reduced in FGFR4 knockdown tumor xenograft tissues. Consistent with the reduced beta-catenin activation, Taqman analyses show that FGF19/FGFR4 inhibition reduced beta-catenin target gene (cyclin D1, CD44, c-jun, Cox-2, UPAR) expression. These findings highlight that FGF19/FGFR4 cross-talk with beta-catenin and that pathway intervention reduces tumor growth.
authors.affiliation: Department of Pathology, Genentech Incorporated, South San Francisco, California 94080, USA. rpai@gene.com
authors.forename: Rama
authors.initials: R
authors.lastname: Pai
authors.forename: Debra
authors.initials: D
authors.lastname: Dunlap
authors.forename: Jing
authors.initials: J
authors.lastname: Qing
authors.forename: Iman
authors.initials: I
authors.lastname: Mohtashemi
authors.forename: Kathy
authors.initials: K
authors.lastname: Hotzel
authors.forename: Dorothy M
authors.initials: DM
authors.lastname: French
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D020134:Catalytic Domain; D049109:Cell Proliferation / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000473:pathology*; D005260:Female; D005346:Fibroblast Growth Factors / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000276:immunology / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D045325:HCT116 Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051499:Receptor, Fibroblast Growth Factor, Type 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013912:Threonine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D000906:Antibodies; C117476:FGF19 protein, human; D034741:RNA, Small Interfering; D051176:beta Catenin; D013912:Threonine; D012694:Serine; D005346:Fibroblast Growth Factors; C496371:FGFR4 protein, human; D011505:Protein-Tyrosine Kinases; D051499:Receptor, Fibroblast Growth Factor, Type 4; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3