MicroRNA let-7c Inhibits Cell Proliferation and Induces Cell Cycle Arrest by Targeting CDC25A in Human Hepatocellular Carcinoma

PLoS One. 2015 Apr 24;10(4):e0124266. doi: 10.1371/journal.pone.0124266. eCollection 2015.

Abstract

Down-regulation of the microRNA let-7c plays an important role in the pathogenesis of human hepatocellular carcinoma (HCC). The aim of the present study was to determine whether the cell cycle regulator CDC25A is involved in the antitumor effect of let-7c in HCC. The expression levels of let-7c in HCC cell lines were examined by quantitative real-time PCR, and a let-7c agomir was transfected into HCC cells to overexpress let-7c. The effects of let-7c on HCC proliferation, apoptosis and cell cycle were analyzed. The in vivo tumor-inhibitory efficacy of let-7c was evaluated in a xenograft mouse model of HCC. Luciferase reporter assays and western blotting were conducted to identify the targets of let-7c and to determine the effects of let-7c on CDC25A, CyclinD1, CDK6, pRb and E2F2 expression. The results showed that the expression levels of let-7c were significantly decreased in HCC cell lines. Overexpression of let-7c repressed cell growth, induced cell apoptosis, led to G1 cell cycle arrest in vitro, and suppressed tumor growth in a HepG2 xenograft model in vivo. The luciferase reporter assay showed that CDC25A was a direct target of let-7c, and that let-7c inhibited the expression of CDC25A protein by directly targeting its 3' UTR. Restoration of CDC25A induced a let-7c-mediated G1-to-S phase transition. Western blot analysis demonstrated that overexpression of let-7c decreased CyclinD1, CDK6, pRb and E2F2 protein levels. In conclusion, this study indicates that let-7c suppresses HCC progression, possibly by directly targeting the cell cycle regulator CDC25A and indirectly affecting its downstream target molecules. Let-7c may therefore be an effective therapeutic target for HCC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Animals
  • Apoptosis / genetics
  • Carcinoma, Hepatocellular / genetics*
  • Carcinoma, Hepatocellular / pathology
  • Cell Cycle Checkpoints / genetics*
  • Cell Line, Tumor
  • Cell Proliferation
  • Cyclin D1 / genetics
  • Disease Models, Animal
  • Down-Regulation
  • E2F2 Transcription Factor / genetics
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Liver Neoplasms, Experimental / genetics*
  • Liver Neoplasms, Experimental / pathology
  • Mice
  • MicroRNAs / chemistry
  • MicroRNAs / genetics*
  • RNA Interference*
  • RNA, Messenger / chemistry
  • RNA, Messenger / genetics
  • Xenograft Model Antitumor Assays
  • cdc25 Phosphatases / chemistry
  • cdc25 Phosphatases / genetics*

Substances

  • 3' Untranslated Regions
  • E2F2 Transcription Factor
  • MicroRNAs
  • RNA, Messenger
  • mirnlet7 microRNA, human
  • Cyclin D1
  • CDC25A protein, human
  • cdc25 Phosphatases

Grant support

The work was supported by the National 863 Program of China (FSW, Grant No. 2008AA02Z109), and National Natural Science Foundation of China (FSW, Grant No.81272354), as well as in part by Medicine Foundation of Zhejiang Province (XMZ, Grant No.2013RCA006). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.