Studies on the methylation status of CpG sequences located in promoters of selected tumour suppressor genes in breast cancer cells.

In the tested samples of sporadic breast cancer (100 cases), hypermethylation of CpG sequences located in ERalpha promoter was observed in 62 cases. It correlated with: (i) deficiency of ERalpha protein in 45%, (ii) hypermethylation of BRCA1 promoter in 95%, and (iii) nonmethylated E-cadherin promoter in 90%. Fifty-eight percent of the patients with nonmethylated E-cadherin promoter (56 cases) did not show metastasis to lymphatic nodes. The analysis of the methylation level of the promoter of ERalpha, BRCA1, and E-cadherin, frequently connected with their activity, shows that it can be an important parameter in the diagnosis and therapeutic strategies in sporadic breast cancer.