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Detection of BRCA1/2 Mutation and Analysis of Clinicopathological Characteristics in 141 Cases of Ovarian Cancer

ABSTRACT: Breast cancer susceptibility genes 1 and 2 (BRCA1 and BRCA2) are known biomarkers for hereditary ovarian cancer (OC). However, a comprehensive association study between BRCA1/2 mutation spectrum and clinicopathological characteristics in Chinese ovarian cancer patients has not been performed yet to our best knowledge. To fill in this gap, we collected BRCA1/2 sequencing data and clinical information of 141 OC patients from Fujian Cancer Hospital between April 2018 and March 2020. The clinical information includes the age of onset, FIGO staging, pathological types, serum 125 detection level, lymph node metastasis, distant metastasis, the expression of Ki67, and disease history of the patient and his/her family. We then studied their associations by software SciPy 1.0. As a result, we detected pathogenic and potentially pathogenic BRCA1/2 mutations in 27 out of 141 patients (19.15%). Among the 27 patients with mutations, the major type of mutation was frameshift, which was observed in 12 patients (44.4%). Most of the mutation sites were distributed on exons 10 and 11, accounting for 48.1% (13/27) and 22.2% (6/27), respectively. In terms of histological classification, high-grade serous adenocarcinoma accounted for 79.43% of the 141 samples. The BRCA1/2 mutation group was all high-grade serous adenocarcinoma, accounting for 24.1% (27/112) of this group. The incidence of pathogenic mutation in BRCA1 and BRCA2 was 15.7% (19/112) and 7.27% (8/112), respectively. Univariate analysis showed that there was no significant difference between patients with BRCA1/2 mutation and others in age-of-onset, FIGO stage, pathological types, serum CA125 level, lymph node metastasis, the expression of Ki67, and personal and family disease history. However, there are significant differences between patients with BRCA1/2 mutation and others in distant metastasis rate (P < 0.002). In addition, the BRCA1/2 mutation rate in 141 ovarian cancer patients was similar to those reported in other studies in China. Nearly one-quarter of high-grade serous carcinomas had BRCA1/2 mutations. In conclusion, our study indicated that patients with BRCA1/2 mutations were more likely to undergo distant metastasis, and BRCA1/2 mutation detection should be performed for patients with high-grade serous adenocarcinoma to guide the selection of clinical treatment options.

SUBMITTER: Li L

PROVIDER: S-EPMC8554521 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundApproximately 3/4 of ovarian cancers are diagnosed in advanced stages, with the high-grade epithelial ovarian carcinoma (EOC) accounting for 90% of the cases. EOC present high genomic instability and somatic loss-of-function variants in genes associated with homologous recombination mutational repair pathway (HR), such as BRCA1 and BRCA2, and in TP53. The identification of germline variants in HR genes in EOC is relevant for treatment of platinum resistant tumors and relapsed tumors with therapies based in synthetic lethality such as PARP inhibitors. Patients with somatic variants in HR genes may also benefit from these therapies. In this work was analyzed the frequency of somatic variants in BRCA1, BRCA2, and TP53 in an EOC cohort of Brazilian patients, estimating the proportion of variants in tumoral tissue and their association with progression-free survival and overall survival.MethodsThe study was conducted with paired blood/tumor samples from 56 patients. Germline and tumoral sequences of BRCA1, BRCA2, and TP53 were obtained by massive parallel sequencing. The HaplotypeCaller method was used for calling germline variants, and somatic variants were called with Mutect2.ResultsA total of 26 germline variants were found, and seven patients presented germline pathogenic or likely pathogenic variants in BRCA1 or BRCA2. The analysis of tumoral tissue identified 52 somatic variants in 41 patients, being 43 somatic variants affecting or likely affecting protein functionality. Survival analyses showed that tumor staging was associated with overall survival (OS), while the presence of somatic mutation in TP53 was not associated with OS or progression-free survival.ConclusionFrequency of pathogenic or likely pathogenic germline variants in BRCA1 and BRCA2 (12.5%) was lower in comparison with other studies. TP53 was the most altered gene in tumors, with 62.5% presenting likely non-functional or non-functional somatic variants, while eight 14.2% presented likely non-functional or non-functional somatic variants in BRCA1 or BRCA2.

Project description:Mutations in BRCA1/2 increase the risk of developing breast and ovarian cancer. Germline BRCA1/2 mutations occur in 8.6-13.7% of unselected epithelial ovarian cancers, somatic mutations are also frequent. BRCA1/2 mutated or dysfunctional cells may be sensitive to PARP inhibition by synthetic lethality. The aim of this study is to comprehensively characterise the BRCA1/2 status of a large panel of ovarian cancer cell lines available to the research community to assist in biomarker studies of novel drugs and in particular of PARP inhibitors. The BRCA1/2 genes were sequenced in 41 ovarian cell lines, mRNA expression of BRCA1/2 and gene methylation status of BRCA1 was also examined. The cytotoxicity of PARP inhibitors olaparib and veliparib was examined in 20 cell lines. The cell line SNU-251 has a deleterious BRCA1 mutation at 5564G > A, and is the only deleterious BRCA1/2 mutant in the panel. Two cell lines (UPN-251 and PEO1) had deleterious mutations as well as additional reversion mutations that restored the protein functionality. Heterozygous mutations in BRCA1/2 were relatively common, found in 14.6% of cell lines. BRCA1 was methylated in two cell lines (OVCAR8, A1847) and there was a corresponding decrease in gene expression. The BRCA1 methylated cell lines were more sensitive to PARP inhibition than wild-type cells. The SNU-251 deleterious mutant was more sensitive to PARP inhibition, but only in a long-term exposure to correct for its slow growth rate. Cell lines derived from metastatic disease are significantly more resistant to veliparib (2.0 fold p = 0.03) compared to those derived from primary tumours. Resistance to olaparib and veliparib was correlated Pearsons-R 0.5393, p = 0.0311. The incidence of BRCA1/2 deleterious mutations 1/41 cell lines derived from 33 different patients (3.0%) is much lower than the population incidence. The reversion mutations and high frequency of heterozygous mutations suggest that there is a selective pressure against BRCA1/2 in cell culture similar to the selective pressure seen in the clinic after treatment with chemotherapy. PARP inhibitors may be useful in patients with BRCA1 deleterious mutations or gene methylation.

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Detection of BRCA1/2 Mutation and Analysis of Clinicopathological Characteristics in 141 Cases of Ovarian Cancer

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