Evaluation of Wild Yam (Dioscorea villosa) Root Extract as a Potential Epigenetic Agent in Breast Cancer Cells
Aberrant epigenetic alterations in the genome, is believed to be a potential cause of some forms of cancer. Due to their reversibility, epigenetic modifications are considered potentially useful in drug development approaches (epi-drugs). The currently available synthetic epi-drugs are non-specific and induce adverse effects. Natural products might offer advantages and find utility for cancer treatment . The present study was designed to evaluate the efficacy of wild yam root extract as a potential demethylating agent using two breast cancer cell lines, MCF-7 (Estrogen receptor positive, ER+) and MDA-MB-231 (ER negative, ER-), and a gene, GATA-3, a potential marker of breast cancer development. Moreover, GATA-3 expression is methylation-specific, being higher in ER+ cells with promoter hypomethylation and insignificant in ER- with promoter hypermethylation. In this study, cells, approximately at 70% confluency, were treated with wild yam root extract (0 – 50 µg/mL) for 72h and then used for viability, mRNA, and methylation analyses. It was observed that wild yam significantly reduced viability of both cell lines and enhanced the mRNA contents of DNMTs (DNMT1, 3A, and 3B) and GATA-3 in a dose-dependent manner. Global DNA methylation, analyzed as 5'-methyl-2'-deoxycytidine (mC) and 5-hydroxymethylcytosine (hmC), showed that mC was increased only in MCF-7 cells, whereas hmC level was reduced in both cell lines. Since hmC is generated from mC by ten-eleven-translocation (TET) enzymes, the present data suggest that enhanced expression of GATA-3 and DNMT enzymes followed by a reduction in hmC in MCF-7 and MDA-MB-231 cells are the result of interruption of TET enzyme functions in the epigenome by wild yam root extract. This plant with a long history of traditional use should be further explored with regard to its potential as an epigenetic agent in breast cancer therapy. Acknowledgements: Thanks go to the United States Department of Agriculture, Agriculture Research Service, Specific Cooperative Agreement No.1UO1FD004246. References:  Khan SI, Aumsuwan P, et al. (2012) Chem Res Toxicol, 25: 61 – 73.