title: Critical role of farnesoid X receptor for hepatocellular carcinoma cell proliferation.
abstract: Farnesoid X receptor (FXR), a pivotal factor maintaining bile acid homeostasis, has been recently shown to be a critical factor required for liver regeneration. The elucidation of the mechanism how FXR controls the proliferation of hepatocellular carcinoma cells is useful to establish the therapy for liver cancer. Here, we show that FXR plays a crucial role in the proliferation of human hepatocellular carcinoma cell line, HepG2, Huh7 and HLE. The treatment of HepG2 with FXR siRNA elevates the level of p16/INK4a expression resulting in the inhibition of cell proliferation. By contrast, FXR activation reduces p16/INK4a expression and stimulates the cell proliferation. The ectopic expression of the active form of Ras that causes strong activation of extracellular signal-regulated kinase (ERK) leads to the decrease in FXR expression, suggesting that FXR expression is negatively regulated via Ras/ERK pathway. The elevation of p16/INK4a expression and the inhibition of cell proliferation by FXR knockdown are also observed in Huh7 and HLE. In this study, we have suggested a novel mechanism by which hepatocellular carcinoma cell proliferation is regulated: FXR stimulates cell proliferation by suppressing the p16/INK4a expression, whereas Ras/ERK pathway down-regulates the FXR expression, leading to the suppressed cell proliferation in hepatocellular carcinoma cell lines.
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Science, Tokyo, Japan. tfujino@ps.toyaku.ac.jp
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Fujino
authors.forename: Airi
authors.initials: A
authors.lastname: Takeuchi
authors.forename: Akiko
authors.initials: A
authors.lastname: Maruko-Ohtake
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ohtake
authors.forename: Junichi
authors.initials: J
authors.lastname: Satoh
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Haruka
authors.initials: H
authors.lastname: Ito
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sakamaki
authors.forename: Ryo
authors.initials: R
authors.lastname: Kashimura
authors.forename: Ken
authors.initials: K
authors.lastname: Ando
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nishimaki-Mogami
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Ohkubo
authors.forename: Naomi
authors.initials: N
authors.lastname: Kitamura
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Sato
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Kikugawa
authors.forename: Makio
authors.initials: M
authors.lastname: Hayakawa
mesh_terms: D002070:Butadienes / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D053144:Cell Nucleus Shape; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D017228:Hepatocyte Growth Factor / Q000502:physiology; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms; D020935:MAP Kinase Signaling System; D009570:Nitriles / Q000494:pharmacology; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D002070:Butadienes; D019941:Cyclin-Dependent Kinase Inhibitor p16; D048049:Extracellular Signal-Regulated MAP Kinases; D017228:Hepatocyte Growth Factor; D051557:Hepatocyte Nuclear Factor 4; D009570:Nitriles; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D000099150:Receptor, Farnesoid X-Activated; C496592:HNF4A protein, human; C113580:U 0126; C501009:HRAS protein, human