miRNA genes play an important role in cancer pathogenesis, while they may be suppressed by hypermethylation. Here, we assess the diagnostic potential of a group of hypermethylated miRNA genes (MIR-124-1, MIR-124-3, MIR-125B-1, MIR-127, MIR-132, MIR-193a, and MIR-34b/c) in a representative set of 70 breast cancer samples and 17 breast tissue samples from deceased donors with no malignancies. For these seven genes, the methylation status is determined using the methylation-specific PCR. Methylation reached 26-76% in tumor specimens, 1-27% in paired considered normal breast tissues, and 0-18% in breast tissue from deceased donors. By quantitative RT-PCR, reduced expression levels of the investigated miRNAs are detected, with a negative correlation of expression levels with gene hypermethylation. Combinations of three or four hypermethylation biomarkers, namely, MIR-124-1, MIR-125B-1, MIR-127, and MIR-34b/c are found suitable for breast cancer diagnostics; with sensitivity (76-93%), specificity (88-100%), and AUC (0.88-0.94). Notably, the MIR-127 gene was hypermethylated only in the tumor samples of patients with metastases, and, therefore, should be tested as a marker of breast cancer dissemination. These findings may lead to improvement in the management of breast cancer.
Keywords: MIR-127; breast cancer; diagnostic markers; hypermethylation; metastasis marker; miRNA genes.