Changes in Gene Methylation Following Chemotherapy in Breast Cancer Cell Lines

Abstract

Objective: Epigenetic modulation of gene expression by DNA promoter methylation may contribute to acquired resistance to chemotherapy in cancer cells. Decitabine (5-aza-2'- deoxycytidine), a demethylating agent, may act synergistically with standard chemotherapy regimens to activate epigenetically silenced genes. In the present in vitro study, it was investigated the effect of gene methylation level after treatment with decitabine and combination of decitabine with anthracycline-based therapeutics (5-fluorouracil plus epirubicine plus cyclophosphamide; FEC) on breast cancer cells (MCF-7 and MDA-MB-231). Methods: The effect of decitabine and its combination with FEC on different genes methylation level has been tested in MDA-MB-231 and MCF-7 human breast cancer cell lines. The effect of decitabine on the cell viability was assayed by MTT assay. Methylight real-time PCR and methylation specific PCR were carried out to determine the methylation status of certain genes: DAPK, TMS1, MGMT and the global methylation marker LINE-1. Results: The LINE-1 methylation status significantly decreased in both cell lines after treatment with the combination of decitabine with FEC. In MDA-MB-231 cells, methylation of the TMS1 and the MGMT gene promoter was significantly reduced by FEC plus decitabine while no effect was observed in MCF-7 cells. Conclusion: Anthracycline-based therapy regimens in combination with demethylating agents such as decitabine may affect chemotherapy outcome by modulation of apoptosis- relevant genes by methylation. More importantly, this modulation seems to be dependent on