Altered DNA methyltransferases promoter methylation and mRNA expression are associated with tamoxifen response in breast tumors

Tamoxifen is a standard anti‐hormone treatment in estrogen receptor positive breast carcinoma patients. Unfortunately, about 50% of patients relapse during treatment. Promoter hypermethylation contributes to the epigenetic modulation of tamoxifen resistance‐related genes. To evaluate the contribution of DNMTs expression and their promoter methylation as diagnostic biomarkers in development of breast malignancy and tamoxifen resistance, the present study was designed and 107 breast tumors and normal breast tissues were recruited. Methylation‐specific high‐resolution melt curve analysis and quantitative RT‐PCR were performed to evaluate DNMTs promoter methylation and mRNA expression, respectively. Our results indicated that DNMT3A and DNMT3B promoters were demethylated in breast tumors as compared to control tissues. The mRNA expression levels of all three DNMTs were significantly increased in tumor specimens in comparison to control tissues (p