BRCA1 deficiency is a recurrent event in early-onset triple-negative breast cancer: a comprehensive analysis of germline mutations and somatic promoter methylation
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BRCA1 germline mutation is closely associated with triple-negative breast cancer. BRCA deficiency leads to impaired DNA repair and tumor development, and understanding this deficiency, in both hereditary and sporadic scenarios, is of great clinical and biological interest. Here, we investigated germline or somatic events that might lead to BRCA1 impairment in triple-negative breast cancer. We also analyzed the clinical implications associated with BRCA deficiency.
Next-generation sequencing for the BRCA1/2 genes and multiplex ligation-dependent probe amplification (MLPA) for the BRCA1 gene were performed for mutation screening. A customized bisulfite next-generation sequencing approach was used for assessing BRCA1 promoter methylation status in tumor tissue.
A total of 131 triple-negative cases were assessed, and germline pathogenic variants were detected in 13.0% of all cases and in 26% of cases diagnosed in young women. Most germline pathogenic variants (88.2%) occurred in the BRCA1 gene. BRCA1 promoter hypermethylation was detected in 20.6% of tumors; none of these tumors were in BRCA1/2 pathogenic variant carriers. BRCA1 impairment by either germline or somatic events was significantly more frequent in young women (55% in those ≤ 40 years; 33% in those 41–50 years; 22% in those > 50 years of age) and associated with better overall and disease-free survival rates in this group of patients.
BRCA1 deficiency was recurrent in early-onset triple-negative breast cancer in Brazilian patients and associated with improved survival. With the new treatment modalities being investigated, including poly (ADP-ribose)-polymerase (PARP) inhibitor therapy, our results suggest that a significant proportion of young women with this subtype of tumor might benefit from PARP inhibitor treatment, which warrants further investigation.
KeywordsTriple-negative breast cancer BRCA1 Mutation Methylation Germline Somatic
The authors are grateful to all patients for donating their biological samples for scientific research. We also thank Dr. Vinicius Fernando Calsavara for assistance with the statistical analysis and the A. C. Camargo Institutional Biobank for providing the DNA samples for the study.
Compliance with ethical standards
The authors declare that they have no conflict of interest.
All procedures performed involving human participants were in accordance with the ethical standards of the A. C. Camargo Cancer Center Research Ethics Committee (Number 1746/13) and with the 1964 Helsinki declaration and its later amendments. Written informed consent was obtained from all patients of the study, who signed the informed consent allowing the use of their biological material, donated for our Biobank, for scientific projects, and for data publication. The A. C. Camargo Cancer Center Biobank has approval of the National Ethical Committee under number B-001.
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