Regulation of cell cycle progression and expression of tumor suppressor genes in human colonic cancer cells by epigenetics / 中华消化杂志

ABSTRACT

Objective To investigate the effects of DNA methylation and histone acetylation on cell cycle progression and expression of tumor suppressor genes in human colonic cancer cells. Methods Three colonic cancer cell lines(HT 29,SW1116 and Colo 320) were treated with the DNA methylation inhibitor, 5 aza 2' deoxycytidine(5 aza dC) and/or the histone deacetylase(HDAC) inhibitor, trichostatin A(TSA)and sodium butyrate. The methylation status of the promoter of the p16 INK4A gene was assayed by methylation specific PCR(MSP). The expression of p16 INK4A and p21 WAF1 were analyzed by RT PCR. Cell cycle distribution was studied by flow cytometry. Results p16 INK4A expression was weakly detected in three colon cancer cells (HT 29,SW1116 and Colo 320) and p21 WAF1 expression was not detected in SW1116 and Colo 320 cells before treatment. The methylation status of the promoter of the p16 INK4A gene was significantly decreased and mRNA expression was markedly increased in HT 29 cells after treatment with 1 ?mol/L but not 10 ?mol/L of 5 aza dC for 24 hours. In SW1116 and Colo 320 cells, the expression of p16 INK4A was obviously enhanced at 10 ?mol/L or 5 ?mol/L of 5 aza dC for 24 hours. However, p21 WAF1 gene expression has not been detected. Interestingly, after treatment of TSA or sodium butyrate, the transcription of p21 WAF1 was significantly up regulated in these two cell lines. In addition, 5 aza dC did not affect cell cycle distribution, but TSA or sodium butyrate blocked cells mainly in the G 1 phases. Conclusions The expression of p16 INK4A gene was regulated by DNA methylation in three human colonic cancer cells. The expression of p21 WAF1 gene was regulated by histone acetylation in SW1116 and Colo 320. In these two cell lines, histone hyperacetylation causes a G 1 cell cycle arrest.