The search for interacting long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs of protein-coding genes through the mechanism of competing endogenous RNAs in tumors of ovarian cancer patients was carried out. The levels of expression of 24 lncRNAs, 20 miRNAs, and 28 mRNAs of protein-coding genes involved in oncogenesis were determined by real-time PCR on a set of representative samples. Correlations between lncRNAs/miRNA and miRNA/mRNA levels in ovarian cancer samples were analyzed. We identified 8 pairs of lncRNAs/miRNA and 17 pairs of miRNA/mRNA, the expression levels of which have a negative correlation. Five triplets of potentially interacting lncRNAs/miRNA/mRNA have been identified, among which the most significant triplet is the OIP5-AS1/miR-203a-3p/ZEB1. The data obtained determine new epigenetic profiles, as well as new potential biomarkers and targets for targeted therapy of ovarian cancer patients.

We studied the correlations between the levels of methylation of a group of 21 microRNA genes in 99 primary tumors and 29 macroscopic peritoneal metastases of ovarian cancer. Analysis of the level of methylation by quantitative methylation-specific PCR showed that co-methylation was detected for 13 pairs of microRNA genes in primary tumors and for 22 pairs in metastases. Pairs of microRNA genes that have shown significant co-methylation can be involved in common processes and pathways of gene regulation and interaction and can have common target genes. The results are highly significant and pairs of microRNA genes can be proposed as new potential markers for the diagnosis and prognosis of ovarian cancer metastasis.

The content of the soluble form of protein of the key point of immunity B7-H3 (sB7-H3) in the blood plasma of 75 patients with epithelial ovarian cancer before treatment was measured by ELISA. It is known that B7-H3 belongs to the immunoglobulin superfamily (B7 molecule family) and is involved in the regulation of the immune response mediated by T cells. The sB7-H3 concentration correlated with the clinical and morphological parameters of ovarian cancer. The content of sB7-H3 was higher at the later stages of the disease, in the presence of ascites, and in patients with poorly differentiated ovarian cancer. It was revealed that increased plasma content of sB7-H3 in patients with epithelial ovarian cancer is associated with unfavorable prognosis of the disease. Therefore, sB7-H3 can be used as a prognostic marker in ovarian cancer patients.

We identified a group of miRNA genes whose methylation is associated with ovarian cancer metastasis. Based on these data, new markers and the systems of markers predicting tumor dissemination were selected. Using methylation-specific PCR and a representative set of 54 ovarian cancer samples, we identified 10 microRNA genes (MIR-124a-2, MIR-127, MIR-125b-1, MIR-129-2, MIR-137, MIR-193a, MIR-203a, MIR-34b/c, MIR-130b, and MIR-1258) whose methylation is associated with tumor metastasis. The greatest association was established for 4 genes: MIR-137, MIR-193a, MIR-34b/c, and MIR-130b (p<0.01). ROC analysis revealed 3 most optimal marker systems including 4-5 miRNA genes and characterized by high sensitivity (82-94%) and specificity (76-86%) at AUC=0.89-0.92. Methylation of any three genes from these systems is sufficient to predict metastasis with the specified accuracy. Detection of the group of hypermethylated miRNA genes with predictive value for ovarian cancer metastasis is of great importance for personalized treatment of the patients.

The study was designed to determine genes of microRNAs hypermethylated in malignant ovarian tumors and to select new diagnostic and prognostic markers of the disease and effective system of markers. Using methyl-specific PCR and a representative sample of 54 ovarian cancer specimens, we determined 5 microRNA genes ( MIR-34b/c , MIR-9-1 , MIR-124-3 , MIR-129-2 , and MIR-107 ) hypermethylated in the majority of tumor samples in comparison with paired samples of histologically unchanged tissue (48-57% vs . 4-19%, p <0.001). Using ROC-analysis, we selected an effective system of 4 markers for diagnosis of ovarian cancer ( MIR-9-1 , MIR-124-3 , MIR-129-2 , and MIR-107 ) characterized by high sensitivity and specificity (up to 87-94% at AUC=0.92) relative to the conventional norm (54 paired samples of histologically unchanged tissue) and absolute norm (18 ovarian tissue samples from subjects who died from non-tumor diseases). It was also shown that methylation of MIR-129-2 , MIR-9-1 , and MIR-34b/c genes is significantly ( p <0.01) correlated with the clinical stage or the presence of metastases. The results indicate that epigenetic modifications of the studied microRNA genes are involved in the pathogenesis and progression of ovarian cancer and attest to their diagnostic and prognostic potential.

We studied microRNA whose expression can be regulated by carcinogenic compounds. Bioinformatic analysis has detected microRNA potentially regulated by xenosensor receptors AhR (miR-28, miR-30c, miR-30e, miR-139, and miR-153) and CAR (miR-29c, miR-31, miR-185, miR-625, and miR-652). Published data indicate that these microRNAs are oncosuppressors, except miR-31 that can act as an oncogene. The expression of these microRNAs in malignant tumors of the endometrium was studied. The expression of the majority of the studied microRNAs, except miR-652, was 2-3-fold below the normal, which confirms their oncosuppressor function and indicates their involvement in the endometrial carcinogenesis and hence, allows considering them as potential markers of the disease.

MicroRNA and methylation are important epigenetic mechanisms in the pathogenesis of cancer. The role of a group of microRNA hypermethylated genes in the pathogenesis of ovarian cancer was studied and their diagnostic and prognostic potential was evaluated. Studies on a representative sample of 54 ovarian cancer specimens with the use of methyl-specific PCR resulted in detection of five microRNA genes (MIR-9-1, MIR-9-3, MIR-107, MIR-1258, and MIR-130b) methylated in the majority of tumor specimens in comparison with paired specimens of histologically intact tissue (37-57% vs. 4-9%, p<0.01). Methylation of three genes (MIR-9-1, MIR-9-3, and MIR-130b) was significantly (p≤0.05) associated with the parameters of ovarian cancer progress (clinical stage, differentiation degree, tumor size, and presence of metastases). These findings attest to oncosuppressive role of the studied microRNA genes (MIR-9-1, MIR-9-3, MIR-107, MIR-1258, and MIR-130b) in the pathogenesis and progress of ovarian cancer and indicated their prognostic potential.

IGF-I, II, IGFBP-1, 2 and 3 levels were measured with standard ELISA kits (Mediagnost) in blood serum of 44 ovarian cancer, 12 benign and 11 borderline ovarian tumorpatients. Control group comprised 33 practically healthy women. Serum IGF-1 content in ovarian cancer patients was significantly lower, and IGFBP-1 content higher than in all other groups. IGFBP-2 level was increased both in ovarian cancer and borderline tumor groups as compared to control and benign ovarian tumor patients. No significant associations were found between the majority ofparameters studied and main clinico-pathologic characteristics of ovarian cancer. Thus, disturbances in IGFs/IGBPs balance were revealed in blood serum of ovarian cancer patients, and IGFBP-2 proved to be a potential diagnostic serological marker with 90% specificity and 90% sensitivity.

The IGF system including IGF ligands, their receptors and IGF binding proteins connected by uneasily regulated interrelations, also interacts with some other biological regulators of cell proliferation and growth. IGF system components modulate normal growth processes and tumor growth. IGF-1 inhibits apoptosis and stimulates cell proliferation. Laboratory and clinical investigations show that IGF signaling pathway plays an important role at all stages of tumor development: malignant transformation of cells, tumor growth, invasion and metastasizing as well as resistance to treatment. In this connection, the strategies of IGF effects inhibition are yet under investigation those (1) blocking IGF-receptor binding, (2) using endogenous inhibitors of IGF effects in tissue IGFBP, which can neutralize IGF ligands and block IGF-receptor activation, and (3) using specific inhibitors against internal IGF-R1 tyrosine kinase.