DNA hypermethylation in breast cancer and its association with clinicopathological features.

Aberrant hypermethylation of gene promoter regions is one of the mechanisms for inactivation of tumour suppressor genes in breast cancer. We investigated whether hypermethylation identifies breast cancers with distinctive clinical and pathological features. We evaluated the methylation of RARbeta2, CDH1, ER, BRCA1, CCND2, p16 and TWIST in 193 breast carcinomas. Methylation frequencies ranged from 11% for CCND2 to 84% for ER. Tumours with frequent methylation (4-6 genes) were more often poorly differentiated compared to those with infrequent methylation (0-2 genes; P=0.004). Tumours with ER and CDH1 methylation were associated with significantly lower hormone receptor levels, younger age at diagnosis and the presence of mutant p53. Our data suggests that gene methylation may be linked to various pathological features of breast cancer, however, this requires confirmation in larger studies.