Role of DNA methylation in cell cycle arrest induced by Cr (VI) in two cell lines

PLoS One. 2013 Aug 6;8(8):e71031. doi: 10.1371/journal.pone.0071031. Print 2013.

Abstract

Hexavalent chromium [Cr(IV)], a well-known industrial waste product and an environmental pollutant, is recognized as a human carcinogen. But its mechanisms of carcinogenicity remain unclear, and recent studies suggest that DNA methylation may play an important role in the carcinogenesis of Cr(IV). The aim of our study was to investigate the effects of Cr(IV) on cell cycle progress, global DNA methylation, and DNA methylation of p16 gene. A human B lymphoblastoid cell line and a human lung cell line A549 were exposed to 5-15 µM potassium dichromate or 1.25-5 µg/cm² lead chromate for 2-24 hours. Cell cycle was arrested at G₁ phase by both compounds in 24 hours exposure group, but global hypomethylation occurred earlier than cell cycle arrest, and the hypomethylation status maintained for more than 20 hours. The mRNA expression of p16 was significantly up-regulated by Cr(IV), especially by potassium dichromate, and the mRNA expression of cyclin-dependent kinases (CDK4 and CDK6) was significantly down-regulated. But protein expression analysis showed very little change of p16 gene. Both qualitative and quantitative results showed that DNA methylation status of p16 remained unchanged. Collectively, our data suggested that global hypomethylation was possibly responsible for Cr(IV)-induced G₁ phase arrest, but DNA methylation might not be related to up-regulation of p16 gene by Cr(IV).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinogens, Environmental / toxicity*
  • Cell Cycle / drug effects
  • Cell Cycle / genetics
  • Cell Cycle Checkpoints / drug effects*
  • Cell Cycle Checkpoints / genetics*
  • Cell Line
  • Chromium / toxicity*
  • Cyclin-Dependent Kinase 4 / genetics
  • Cyclin-Dependent Kinase 4 / metabolism
  • Cyclin-Dependent Kinase 6 / genetics
  • Cyclin-Dependent Kinase 6 / metabolism
  • DNA Methylation / physiology*
  • Gene Expression Regulation / drug effects
  • Genes, p16 / drug effects
  • Humans
  • Promoter Regions, Genetic / drug effects
  • Solubility

Substances

  • Carcinogens, Environmental
  • Chromium
  • chromium hexavalent ion
  • CDK6 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinase 6

Grant support

This research work was supported by National Natural Science Foundation of China (Grant No. 81001242), Zhejiang Provincial Natural Science Foundation of China (Grant No. Y2100687), Key Medical Discipline Construction Plan of Zhejiang Province, China (Grant No. 11-ZC02), and the Young Core Researcher program from Health Bureau of Zhejiang Province, China (Grant No. 2011RCA001). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.