title: Interleukin-6 mediates G(0)/G(1) growth arrest in hepatocellular carcinoma through a STAT 3-dependent pathway.
abstract: Interleukin-6 (IL-6) is a pleiotropic cytokine that regulates diverse cell functions including proliferation and differentiation. Within the liver IL-6 signaling plays a central role during normal hepatic growth and regeneration yet can inhibit the proliferation of hepatocellular carcinoma (HCC) cells. The aim of the current study was to identify underlying mechanisms whereby IL-6 induces cell-cycle arrest in HCC cells. These studies demonstrate that IL-6 inhibits cell-cycle progression at the G(0)/G(1) interface through inhibition of cyclin-dependent kinase (cdk) 2 and cdk4 activity in the absence of changes in total cyclin (A, D1, D3, and E) or cdk (cdk2, 4, and cdc2 p34) expression. Inhibition of signal transduction pathways associated with IL-6 receptor activation demonstrates that IL-6-dependent inhibition of G(0)-G(1) progression occurs via Janus tyrosine kinase-signal transducers and activators of transcription-3 (Jak-STAT3)-dependent induction of p21(waf1/cip1) and is independent of ERK-MAPK signaling. These data demonstrate that, while IL-6 plays a central role in hepatocyte priming and proliferation in vivo, the pronounced inhibition of proliferation observed in HCC cells occurs due to IL-6-STAT3-dependent regulation of cdk2/cdk4 activity and p21(waf1/cip1) expression.
authors.affiliation: Department of Biology, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
authors.forename: Dairmuid M
authors.initials: DM
authors.lastname: Moran
authors.forename: M Adrian
authors.initials: MA
authors.lastname: Mattocks
authors.forename: Paul A
authors.initials: PA
authors.lastname: Cahill
authors.forename: Leonidas G
authors.initials: LG
authors.lastname: Koniaris
authors.forename: Iain H
authors.initials: IH
authors.lastname: McKillop
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000032:analysis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D016193:G1 Phase / Q000187:drug effects*; D015850:Interleukin-6 / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D051381:Rats; D016192:Resting Phase, Cell Cycle / Q000187:drug effects*; D050796:STAT3 Transcription Factor / Q000502:physiology*
chemical_list: C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495892:Cdk2 protein, rat; C495903:Cdk4 protein, rat; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D048049:Extracellular Signal-Regulated MAP Kinases