Association between Molecular Genetic Markers of DNA Repair and Cell Cycle Control Genes and Response to Platinum-Based Chemotherapy in Ovarian Cancer Patients.

We analyzed associations of polymorphic markers of DNA repair genes (XRCC1, ERCC2), cell cycle control genes (TP53, MDM2, and CDKN1A), methylation of promoter region, and mutation 5382insC of BRCA1 gene in ovarian cancer with effectiveness of platinumbased chemotherapy assessed by the median of progression-free survival time for markers of DNA repair genes and by relapse risk for all studied markers. An increase in the median of progression-free survival time for carriers of the Gln allele (р=0.025) and Gln/Gln genotype (р=0.022) of the Gln399Arg XRCC1 was observed during the 19-months period after chemotherapy. In carriers of C/C genotype of 5382insC mutation of BRCA1 gene (n=6), no relapses were observed (р=0.035), while 17 of 49 patients without this mutation developed relapses. Of 14 patients with BRCA1 gene function inactivation due to promoter methylation or the presence of the C/C genotype of 5382insC, one relapse was observed (p=0.033). Multivariate analysis revealed an association of markers of the XRCC1, TP53, MDM2 genes, BRCA1 gene inactivation, and type of surgery with the risk of relapse during the follow-up period up to 19 months after the end of chemotherapy (р≤0.0007).

Association of Molecular Genetic Markers of TP53, MDM2, and CDKN1A Genes with Progression-Free Survival of Patients with Ovarian Cancer after Platinum-Based Chemotherapy.

We studied the association of polymorphic markers of cell cycle control genes (Arg72Pro of the TP53 gene, T(-410)G of the MDM2 gene, and Ser31Arg of the CDKN1A gene) in ovarian cancer and progression-free survival following platinum-based chemotherapy. Tumor tissue samples obtained from 49 patients who had undergone chemotherapy were examined. Patients received standard platinum-based chemotherapy and were observed until disease progression. Polymorphic markers of genes were evaluated by PCR-RFLP and real-time PCR. In patients carrying the G allele of the T(-410)G marker of the MDM2 gene, a decreasing trend was observed in median progression-free survival. An increase in the median progression-free survival was observed in carriers of the Pro allele of the TP53 gene (p=0.045). Furthermore, a stronger association was noted with carriers of the minor Pro/Pro homozygous genotype relative to the Arg/Arg genotype (p=0.007). In the subgroup of patients who underwent optimal or complete cytoreductive surgery, carriage of the minor Arg allele of the Ser31Arg marker (CDN1A gene) was associated with a decrease in the median progression-free survival time (p=0.004).

Loss of Heterozygosity in BRCA1 and BRCA2 Genes in Patients with Ovarian Cancer and Probability of Its Use for Clinical Classification of Variations.

Changes (or variants) in BRCA1 and BRCA2 gene sequences can have different lengths and clinical significance: from single nucleotide variants (SNV) and short insertions/deletions (<50 bp) to extended deletions and duplications (so-called copy number variations, or CNV). According to their clinical significance, all variants can be divided into pathogenic, likely pathogenic, variants of uncertain significance, likely benign, and benign. Moreover, variants can be germinal (i.e. inherited from parents) and somatic (arising in the process of development of the organism). A specific somatic event is loss of heterozygosity (LOH), i.e. transition of one or many point and short variants from heterozygous to homozygous state. Such an event can be the key to the development of carcinogenesis for cells carrying a pathogenic variant, if we consider it within the framework of the Knudson's two-hit carcinogenesis theory. We studied the prevalence and nature of LOH in of ovarian cancer samples carrying or not carrying a pathogenic variant. To this end, a full coding sequence of BRCA1/2 genes was determined in 30 pairs of DNA samples isolated from blood cells and paraffinized histological blocks of patients on a MiSeq Illumina instrument. Analyss of the obtained reads revealed 9 pathogenic point and short variants (30% patients): 6 germinal (20%) and 3 somatic (10%), and 8 somatic CNV (3 deletions and 5 duplications of several or all exons of the BRCA1 gene). LOH was detected in 70% patients; among the carriers of pathogenic variants - in 83%. For pathogenic variants, the percentage of reads with the alternative allele increased more often than for benign variants located in another gene, or detected in other patients (67% vs. 44%). However, the difference was statistically insignificant, which can be due to insufficient number of patients. Only in 3 of 21 cases of LOH (14%), it can be attributed to CNV. In other cases, LOH is most likely determined by gene conversion, but further research is needed.

[ERCC1 as a Marker of Ovarian Cancer Resistance to Platinum Drugs].

The review is concerned with the crucial marker of nucleotide excision repair ERCC1 and its contribution to platinum resistance of ovarian cancer. All the variants of the laboratory and clinical ERCC1 assessment in the ovarian cancer tissue (single nucleotide polymorphisms of the ERCC1 gene, levels of mRNA or protein) are considered. Data on the prognostic and predictive value of ERCC1 as a marker of the response to platinum-based therapy in ovarian cancer are systematized. The authors discuss the possible causes of heterogeneity of the results and emphasize the necessity of a unified and integrated approach to evaluation of ERCC1 in the tumor. The publications cited in the Search Engine Pub Med up to January 2015 were analyzed.