title: MiR-222 overexpression promotes proliferation of human hepatocellular carcinoma HepG2 cells by downregulating p27.
abstract: OBJECTIVE
  Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related death worldwide. Increasing evidence suggests that microRNAs, a novel class of non-coding RNAs that function as endogenous suppressors of gene expression, are deregulated in HCC. Although microRNA-222 (miR-222) overexpression has been described in HCC, the role of miR-222 and its target genes in the proliferation of hepatocellular carcinoma cells remain poorly elucidated.
  
  
  METHODS
  HepG2 cells were transfected with miR-222 mimic, inhibitor or their negative controls. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) and EdU incorporation assay. Flow cytometry was performed to assess the effects of miR-222 on HepG2 cell cycle progression. MiR-222 and putative targets genes (p27 and p57) expression levels were determined using qRT-PCR and/or Western blot.
  
  
  RESULTS
  MiR-222 overexpression induced an enhancement of HepG2 cell proliferation in vitro, paralleling with an altered cell cycle progression via increased cell population in S phase. P27 expression, other than p57, was negatively regulated by miR-222 overexpression at post-transcriptional level in HepG2 cells. Transfection of either small interfering RNA (siRNA) for p27 or miR-222 mimic increased HepG2 cell proliferation rate, whereas co-transfection of p27 siRNA and miR-222 mimic did not further enhance HepG2 cell proliferation in comparison with the cells transfected with p27 siRNA or miR-222 mimic alone, validating that p27 is a target gene of miR-222 during HepG2 cell proliferation.
  
  
  CONCLUSIONS
  This study suggests that miR-222 overexpression promotes HepG2 cell proliferation by downregulating p27.
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Yue-Feng
authors: YF
authors: Yang
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Fei
authors: F
authors: Wang
authors: Regeneration Laboratory, School of Life Science, Shanghai University Shanghai 200444, China ; Experimental Center of Life Sciences, Shanghai University Shanghai 200444, China.
authors: Jun-Jie
authors: JJ
authors: Xiao
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Yang
authors: Y
authors: Song
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Ying-Ying
authors: YY
authors: Zhao
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Yan
authors: Y
authors: Cao
authors: Regeneration Laboratory, School of Life Science, Shanghai University Shanghai 200444, China ; Experimental Center of Life Sciences, Shanghai University Shanghai 200444, China.
authors: Yi-Hua
authors: YH
authors: Bei
authors: Division of Gastroenterology and Hepatology, Digestive Disease Institute, Tongji Hospital, Tongji University School of Medicine Shanghai 200065, China.
authors: Chang-Qing
authors: CQ
authors: Yang
keywords: Hepatocellular carcinoma; MicroRNA-222; P27; proliferation