Reversal of hypermethylation and reactivation of the RARβ2 gene by natural compounds in cervical cancer cell lines.

Reactivation of tumour suppressor genes that have been silenced by promoter methylation is a very attractive molecular target for cancer therapy. The treatment of a squamous cervical cancer cell line, SiHa, with 20 μM curcumin and genistein resulted in demethylation of promoter of the RARβ2 gene and led to the reactivation of the gene. The degree of methylation as observed by MSP decreased as the time period of treatment was increased from 72 h to 6 days. In HeLa cells (an adenocarcinoma cervical cancer cell line) there was also reversal of hypermethylation of the RARβ2 gene after six days of treatment with 20 μM curcumin. However, allyl sulphide treatment (20 μM) did not cause the reversal of hypermethylation until 72 h of treatment in the SiHa cell line. This is the first report to show the reversal of hypermethylation of the RARβ2 gene by genistein and curcumin in cervical cancer cell lines. Furthermore, these compounds acted as doublepronged agents as they caused apoptosis in the treated cervical cancer cell lines in addition to reversal of promoter hypermethylation.