The role of microRNA genes methylation in different molecular-biological subtypes of breast cancer

The methylation of CpG islands in the promoter regions of miRNA genes is an epigenetic modification that plays a decisive role in the breast cancer (BC) initiation and progression. The aim of the study was to investigate the frequency of 5 miRNA genes methylation (miRNA-9-1, miRNA-9-3, miRNA-34b/c, miRNA-193A, miRNA-129-2) in mammary epithelial neoplasms. Methylation-specific polymerase chain reaction (MS-PCR) was used to detect methylated genes. 62 patients took part in this study. It was found that the frequency of all 5 miRNAs genes methylation is significantly higher in tumor tissue than in the adjacent histologically unchanged mammary tissue. The authors also performed a correlation analysis and founded a relationship between the methylation rate of certain miRNA genes with some clinical and molecular characteristics of the tumor. This information on epigenetic disorders of BC complements the “molecular portrait” of the tumor and can be used to diagnose and assess the prognosis.