A pilot study to identify single nucleotide variants in exon 19 of the braca1 gene in female breast cancer patients at Matero level one hospital, Lusaka, Zambia.

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Shakachite, Lisa
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The University of Zambia
Breast cancer (BC) patients in Zambia more commonly present with advanced-stage disease and often at young ages (≤50 years). Breast cancer gene 1 (BRCA1) is a tumor suppressor gene in which mutations have been linked to disease presentation at a young age. More than 600 distinct pathogenic (disease causing) single nucleotide variants with the potential for structural and functional effects on BRCA1 have been documented in ClinVar, a major human variation and phenotype database. The BRCA1 C-terminal (BRCT) region is critical for tumor suppression because it acts in DNA damage repair and cell cycle checkpoint protein control. Mutations in this region have been associated to structural effects and loss of function of BRCA1 in many studies. However, BRCT mutations in young female breast cancer patients from Zambia have not been identified to date. The genetic alterations in exon 19 of the BRCA1 gene were assessed here for the first time in a cohort from Zambia. Seventy-three patients diagnosed with breast cancer at the age of ≤50 years were recruited irrespective of family history of breast and/or ovarian cancer. Genomic DNA was extracted from ten peripheral blood samples and PCR-amplified with exon 19-targeting primers of the BRCA1 gene. Amplicons were sequenced using a Sanger sequencing platform and analyzed using bioinformatics tools at various web-based platforms and ClinVar. Overall, elevensingle nucleotide mutations were identified in three patients, and all known to play a role in determining the structure of BRCA1. Of the identified mutations, one was pathogenic and sevenhad uncertain significances. Six of these mutations were heterozygous and classified in the loss of function category in ClinVar. These variants were specifically associated with Breast-ovarian cancer, familial, susceptibility to, 1 (BROVCA1). Four out of the six heterozygous mutations were missense mutations and two were nonsense mutations. Based on an unpaired two-tailed student’s t-test, the null hypothesis that there was no association between the age of a BC patient and the number of mutations in exon 19 leading to a loss of function of BRCA1, was rejected (P= 0.04). Further studies are clearly necessary to explore how mutations in the entire BRCA1 gene affect disease presentation in the female BC population. The young age (≤50 years) for breast cancer diagnosis in female Zambian patients may be attributed to other factors like other genetic mutation status, epigenetic changes, lifestyle etc. These results will help in decision making with regard to the integration of genomic medicine into breast cancer care in Zambia which has tremendous potential to improve the outcomes and survival of diagnosed patients.