Contribution of BRCA1, BRCA2, CHEK2 gene mutations to the pathogenesis of hereditary ovarian cancer in Crimean female patients

Ovarian cancer (OC) is characterized by high heterogeneity of its clinical, morphological and genetic characteristics. A number of genes are identified, the pathology of which leads to the initiation of carcinogenesis, including genes of the DNA damage repair system by homologous recombination. The role of highly penetrant mutations in the BRCA1 and BRCA2 genes has been studied most thoroughly to date [1].

The prevalence of certain mutations responsible for the development of ovarian cancer varies in different geographic regions and ethnic groups, which, on the one hand, complicates the identification of a spectrum of mutations that are universal for the entire population, and on the other hand, dictates the need to study the molecular genetic profile of some individual ethnic groups.

At present, a genetic panel including 7 mutations in the BRCA1 gene and 1 mutation in the BRCA2 gene has been widely introduced into practice in the Russian Federation. Despite the fact that these genetic variants are actually common among Slavs in various regions, data obtained in various studies indicate the presence of some regional differences in the molecular genetic profiles of the tumors [2, 3, 4].

The aim hereof is to study the spectrum of mutations in the genes of hereditary predisposition to ovarian cancer BRCA1, BRCA2, CHEK2 in Crimeans and analyze their role in the pathogenesis of this oncological pathology.

MATERIALS AND METHODS

The study covered one hundred Crimean women representing the Slavic group and the Crimean Tatar ethnic group. The study was approved by the meeting of the Ethics Committee at the Crimean Federal University named after V.I. Vernadsky; all participants

38 | Cardiometry | Issue 33. November 2024

signed their informed consent and were aware of the goals and results of the study.

The main group covered 50 women diagnosed with ovarian cancer. The appropriate inclusion criteria in the main group were as follows: 1) histological findings confirming the diagnosis; 2) the presence of one or more signs of the hereditary nature of the disease (aggravated oncological anamnesis, early age of manifestation, bilateral cancer, combined tumor lesions); 3) the permanent residence in the territory of the Republic; 4) the informed consent to participate in the study. The reference group included 50 healthy women permanently residing in the Republic of Crimea, in case of the absence of data on appearance of oncological diseases in their close relatives. The average age of patients in the main and reference groups was 54.8 ± 9.6 and 53.1 ± 9.3, respectively (p = 0.89).

For the study, 2-3 ml of fasting blood was sampled from the cubital vein. Initially, the DNA samples were isolated from whole blood using spin columns with the Extract DNA Blood kits (Eurogen, Russia). Subsequently, the isolated DNA samples were geno-typed using multiplex allele-specific polymerase chain reaction (PCR) in real time followed by evaluation of the melting curves. The reactions were carried out in accordance with the manufacturer’s recommendations in two parallel test tubes. The composition of the reaction mixture contained the same reverse primer, but differed in the forward primer. The HRR-screen-ing reagent kit (Testgen, Russia) was used to perform real-time PCR. In addition to the eight most common mutations that increase the risk of developing ovarian cancer and breast cancer, the above kit includes primers for identifying eight additional rarer mutations.

Fisher’s exact test were used to analyze differences in qualitative features in independent samples. Differences were considered to be statistically significant at p<0.05.

RESULTS

Genotyping in both groups revealed a total of 13 mutations (13%), 9 of which were found in the main group (18%; 9/50) (see Table 1 herein). 6 mutations (12%) were detected in the BRCA1 gene; 1 mutation (2%) was found in the BRCA2 gene, and two mutations were revealed in the CHEK2 gene (4%). Among the healthy women, 4 carriers (8%) of the CHEK2 gene mutation were found. Other studied mutations were not identified in the reference group.

Table 1.

Spectrum of mutations identified in the study of the main and reference groups

Thus, germline mutations in the BRCA1 gene (p = 0.03) have the greatest significance in the development of ovarian cancer in the examined patients, accounting for 46.2% of the detected mutations. At the same time, two patients are carriers of the “founder” mutation c.5266dupC in the BRCA1 gene, while other detected mutations are rarer for the Russian population. Mutations in the CHEK2 gene are characterized by the similar occurrence rate (46.2% of detected mutations), however, this molecular genetic variant has not shown a significant effect on the increased risk of ovarian cancer according to the results of this study (p = 0.67).

CONCLUSION

The mutations identified in women of the main group reflect trends typical for the Russian population, but some of them are less common and not included in the standard list. Thus, cases of ovarian cancer in carriers of the CHEK2c.470T>C mutation are relatively rare and require a more detailed analysis and study, primarily in order to understand the prognosis of the disease and searching for targeted therapy methods.

Also indicative is the absence of the sought-after mutations in most patients diagnosed with ovarian cancer, including Crimean Tatars, despite the presence of signs of the hereditary nature of the disease. To create a more accurate molecular genetic profile of the Crimean population, it is necessary to continue the research using more sensitive and specific diagnostic methods. This will significantly improve the quality of medical care for cancer patients in the region by improving early diagnostics of the disease, as well as identifying indications for targeted antitumor therapy.