title: Farnesoid X receptor knockdown provides significant growth inhibition in hepatocellular carcinoma cells while it does not interfere with the proliferation of primary human hepatocyte-derived cells.
abstract: Identification of substances with specific toxicity for carcinoma cells promises to facilitate the development of cancer chemotherapeutics that cause minimal side effects. Here, we show that knockdown of the farnesoid X receptor (FXR) effectively suppresses the proliferation of human hepatocellular carcinoma cell lines HepG2 and HLE accompanied by elevated expression of cyclin-dependent kinase (CDK) inhibitor p16/INK4a and p21/Cip1 proteins. On the other hand, the growth of the primary human hepatocyte-derived cell line Fa2N-4 is not affected by the treatment with FXR siRNA irrespective of marked increases in the mRNAs of p16/INK4a and p21/Cip1. Surprisingly, the expression levels of p16/INK and p21/Cip1 proteins are left unchanged in Fa2N-4 cells that are subjected to the FXR siRNA treatment. Since the expression levels of these CDK inhibitor proteins in FXR-knockdown Fa2N-4 cells were elevated in the presence of proteasomal inhibitor MG132, these CDK inhibitors may be subjected to the proteasomal degradation, thereby counteracting the increased expression of their cognate mRNAs, therefore similar levels of p16 and p21 proteins were observed in control and FXR-knockdown Fa2N-4 cells. These results suggest that FXR-knockdown is effective for inhibiting the proliferation of hepatocellular carcinoma cells, not interfering with the regulatory mechanism of normal hepatocyte growth.
authors.affiliation: Department of Hygiene and Health Sciences, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences.
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Fujino
authors.forename: Akiko
authors.initials: A
authors.lastname: Maruko-Ohtake
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ohtake
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Ken
authors.initials: K
authors.lastname: Ando
authors.forename: Airi
authors.initials: A
authors.lastname: Takeuchi
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Ohkubo
authors.forename: Makio
authors.initials: M
authors.lastname: Hayakawa
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology*; D049109:Cell Proliferation / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology*; D006801:Humans; D007976:Leupeptins; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000502:physiology*; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D000099150:Receptor, Farnesoid X-Activated; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde