Genetic and epigenetic profiling of the BRCA1 / 2 genes in solitary ovarian cancer and multiple primary ovarian tumors

Abstract

Background. Ovarian cancer is a complex and poorly studied disease that kills nearly 70–80 % of patients. Therefore, practitioners are interested in any opportunity of improving survival of these patients. From this point of view, investigation of genetic and epigenetic functions associated with this pathology is quite promising.Objective: to assess clinical and morphological characteristics of tumors in ovarian cancer patients, considering the presence of mutations and methylation in the BRCA1/2 gene.Materials and methods. This study included 180 ovarian cancer patients (FIGO stage I–IV) treated in the N. N. Blokhin Russian Cancer Research Center between 2008 and 2019. Study participants were divided into 3 groups according to their BRCA status and the number of primary tumors. We collected and analyzed venous blood, biopsy samples of ovarian cancer, archived histological sections, and paraffin-embedded tissue blocks. DNA isolated from venous blood was used to identify the following germline mutation by pyrosequencing: BRCA1 5382insC, BRCA1 4153delA, BRCA1 185delAG, and BRCA26174delT. DNA isolated from biopsy specimens and paraffin-embedded tissue specimens was used to analyze methylation in the promoter regions of the BRCA1 and BRCA2 genes by bisulfite sequencing (PyroMark Q24 DNA Sequencer; Qiagen, USA) with specific primers targeting promoter regions of the BRCA1 and BRCA2 genes.Results. Molecular testing demonstrated that the frequency of BRCA1 gene mutations was 21.1 % (38/148) in patients with solitary ovarian cancer and 40.6 % (13/32) in patients with multiple primary ovarian cancers. The frequency of methylation of the BRCA1 gene promoter was 2.2 % (18/148) in patients with solitary ovarian cancer and 3.1 % (1 case) in patients with multiple primary ovarian cancers. All BRCA1 methylated ovarian tumors were serous adenocarcinomas, including high grade tumors in 15 patients (78.9 %) and low-grade tumors in 4 patients (21.1 %).Conclusion. Hypermethylation of the BRCA1 gene promoter was observed only in individuals with sporadic serous ovarian cancer. No methylation was detected in patients with non-serous ovarian cancer, as well as in patients carrying BRCA1 gene mutations (both with solitary ovarian cancer and with primary multiple ovarian tumors).

Keywords

• ovarian cancer
• brca1 / 2 gene mutations
• brca1 / 2 promoter hypermethylation