title: Down-regulation of salt-inducible kinase 1 (SIK1) is mediated by RNF2 in hepatocarcinogenesis.
abstract: Our previous study reported that down-regulation of SIK1 accelerates the growth and invasion of hepatocellular carcinoma (HCC). However, the underlying mechanism leading to SIK1 down-regulation in HCC largely remains to be determined. Herein, we demonstrated that RNF2 expression is negatively correlated with SIK1 levels in HCC tissues. Kaplan-Meier analysis of tumor samples revealed that high RNF2 expression with concurrent low SIK1 expression is associated with poor overall survival. The down-regulation of RNF2 expression in HCC cells significantly reduces tumor cell growth and metastasis, while the simultaneous down-regulation of both RNF2 and SIK1 restores tumor cell growth in vitro and in tumor xenograft models. Mechanistically, we identified RNF2 as an E3 ligase that targets SIK1 for degradation. We further demonstrated that direct physical interaction between RNF2 and SIK1 triggers SIK1 down-regulation in HCC cells. These data suggest that RNF2 is an important upstream negative regulator of SIK1 and that restoration of SIK1 levels induced by loss of RNF2 inhibited HCC cell growth and promoted apoptosis, which may represent a promising therapeutic strategy for HCC treatment.
authors.affiliation: Department of Radiation Oncology, The First Hospital of Jilin University, Changchun, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Qu
authors.affiliation: Department of Radiation Oncology, The First Hospital of Jilin University, Changchun, China.
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Qu
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism*; D004195:Disease Models, Animal; D015972:Gene Expression Regulation, Neoplastic; D064593:Heterografts; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D051379:Mice; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D063150:Polycomb Repressive Complex 1 / Q000378:metabolism*; D011379:Prognosis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D054875:Ubiquitination
chemical_list: D063150:Polycomb Repressive Complex 1; C489841:RNF2 protein, human; D017346:Protein Serine-Threonine Kinases; C509080:SIK1 protein, human
keywords: RNF2; SIK1; liver cancer; ubiquitination