Germline BRCA1 and BRCA2 Variants Among Nigerian Breast Cancer Patients

Background: Breast cancer remains a leading cause of mortality among Nigerian women, with triple-negative breast cancer (TNBC) being particularly prevalent. Variations in BRCA1 and BRCA2 genes remain key risk factors for this disease. However, there are gaps in the frequency and spectrum of these variants in Nigerian populations, as well as a dearth in the local capacity to characterize these variations. Objective: This study aimed at identifying and characterizing the germline variations in BRCA1/2 in Nigerian breast cancer patients and healthy age-matched controls to understand the genetic risk profile of breast cancer in this population. Methods: A prospective case-control study was conducted involving 45 breast cancer patients and 51 controls recruited from four major hospitals. DNA was extracted from blood samples, followed by targeted sequencing of BRCA1/2 exonic and intronic regions using the Ampliseq BRCA panel and Illumina MiSeq platform. Variant calling was performed, clinical significance was evaluated on ClinVar and BRCA Exchange databases, and haplotype analysis was performed using NIH LDlink and Haploview 4.2 software. Results: Pathogenic BRCA1/2 variants were identified in 6.7% of breast cancer patients, all with TNBC and a family history of cancer. Two pathogenic BRCA1 variants were detected: a frameshift deletion BRCA1 c.133_134delAA (p.Lys45fs) (rs397508857) and a missense variant BRCA1 c.5324T>A (p.Met1775Arg) (rs41293463). A BRCA2 frameshift deletion BRCA2 c.8817_8820del (p.Lys2939fs) (rs397508010) was also identified. These variants were absent in controls. Haplotype analysis revealed distinct BRCA1 and BRCA2 haplotypes in the breast cancer group. Conclusion: This study identifies key BRCA1/2 pathogenic variants and unique haplotypes in Nigerian breast cancer patients, highlighting the need for population-specific genetic screening. Integrating genetic testing into breast cancer management strategies could facilitate early detection, personalized treatment planning, and genetic counseling in Nigeria