BRCA1 Protein Deficiency in Breast Cancer Microbiopsy Lysate Delineates Patient Survival Time

Abstract

Introduction: Breast-Cancer gene 1(BRCA1) encodes for protein which has many cellular functions including DNA damage repair and maintenance of genome integrity. Malfunction or deficiency of BRCA1 protein, due to mutations or epigenetic inactivation, may provoke breast epithelial cell dedifferentiation and initiate cancer. In fact, mutants of BRCA1 predispose to breast and ovarian cancers. In the past this biomarker was not investigated for breast cancer prevention and care in Benin. The aim of our work is to assess the expression pattern of BRCA1 gene and protein in precancerous and cancerous breast tissue microbiopsies to determine the molecular mechanisms underlying BRCA1 protein suppression and potentiate prognosis and targeted personalized therapy in Benin. Method: This study obtains the institutional ethical approval. Microbiopsy tissues (n = 54) were collected in the Visceral surgery department of the National University Hospital Center HKM (CNHU-HKM) located in the city of Cotonou (Benin) for diagnosis and prognosis purposes. Polymerase chain reaction (PCR) technic with primers targeting Exon 1 and Exon 2 of BRCA1 was used to assess gene transcription capability. Immunoblotting was used to determine BRCA1 protein profile in breast cancer tissue microbiopsy lysates. Ethical approval was obtained for this study. Kaplan–Meier curves analysis was performed to determine the median survival time according to BRCA1 gene and protein patterns. Results: We observed that 87% of samples had lost the expression of BRCA1 protein. Among them, 78% of the loss was not associated to gene deletion. The disparity between the presence of the BRCA1 gene and the lack of protein expression suggested that the silencing of BRCA1 may be due to epigenetic inactivation in most patients. Ultimately, Kaplan Meyer’s survival curve analysis showed that the lack of BRCA1 amplification at Exon 1 or Exon 2 diminished the median survival time of cancer patients to 20 months. Conclusion: BRCA1 protein translation is impaired by Exon 1 or Exon 2 mutation /deletion along with epigenetic inactivation in breast cancer; all together influences median survival time. The delineation of the molecular mechanism underlying BRCA1 gene inactivation leading to protein deficiency will be an excellent molecular tool for African breast cancer prognostic and personalized targeted therapy in the future.