Hypermethylation of a group of microRNA genes in primary tumors and peritoneal metastases of ovarian cancer
Abstract
Ovarian cancer is characterized by the early metastatic activity and high frequency of poor prognosis. Earlier we described a group of miRNA genes where methylation is involved in the development and progression of ovarian cancer. Aim. To expand the array of miRNA genes hypermethylated in ovarian cancer and to study their correlation with metastatic activity both in primary tumors and macro-metastases. Methods. For our study, we used DNA bisulfite conversion followed by methyl-specific PCR. Results. A significant increase in methylation frequency was observed in 54 samples of ovarian cancer compared with histologically intact ovarian tissue for 6 of 7 studied miRNA genes, MIR-107, MIR-1258, MIR-130b, MIR-34b/c, MIR-9-1, and MIR-9-3 (p<10-3, FDR = 0.01). Five miRNA genes statistically significantly correlated with cancer progression, particularly with the metastatic activity. When comparing the methylation status of tumor samples from 37 non-metastatic and 17 metastatic patients we found statistically significant correlations with metastasis for MIR-1258 (p≤0.04), MIR-130b (p≤0.01), and MIR-34b/c (p≤0.001), and tendencies for MIR-9-1 and MIR-9-3. Analysis of primary tumors and matched peritoneal metastases in 13 patients confirmed the association between methylation and metastasis for these 5 genes. Conclusion. This study demonstrated a systemic role of hypermethylation for the group of miRNA genes in peritoneal metastasis in patients with ovarian cancer.