Clinical and Molecular Significance of Poly (ADP-Ribose) Polymerase-1 (PARP-1) in Breast Cancer of African Women and its Potential as a Targeted Therapy

Background: The therapeutic effects of Poly (ADP-ribose) polymerase-1 (PARP -1) inhibition are currently studied in a clinical trial that is recruiting AfricanAmerican (A-A) women with breast cancer (BC). Although, A-A and West African women are likely to share the same ancestry, there are overwhelming evidences, that BC is undoubtedly heterogeneous which might influence results obtained in these Nationalities. Thus, this study aims to investigate PARP-1 expression in a large and annotated series of breast cancer from Nigerian women to determine its clinical and biological significance for the indigenous African women. Methods: PARP-1 protein expression was assessed immunohistochemically in 204 formalin fixed paraffin samples from Nigerian breast cancer women prepared as TMA. Results: PARP-1 was inversely associated with steroid hormone receptors (oestrogen (ER) and progesterone (PR) receptor), the Homologous Recombination marker BRCA1 associated ring domain 1 (BARD1) and p27. Conversely, a positive association was established between PARP-1 and high histologic grade, expression of basal markers (cytokeratins (CK) 5/6 and 14) and epidermal growth factor receptor (EGFR)), DNA damage-repair markers (protein inhibitor of activator signal transducer gamma (PIAS)), the BRCA1 inhibitor (metastasis tumour antigen-1 (MTA1), p53, the proliferation markers (KI-67, Phosphoinositide-3-kinases (PI3KCA)), the triple-negative and basal-like phenotypes. Outcome analysis indicated PARP-1 as a predictor of poor survival independent of tumour size, histological grade and lymph node involvement. Conclusion: These results provide evidence that PARP-1 plays an important role in Nigerian women with breast cancer. It is recommended that indigenous Black women from Africa are included in the ongoing clinical trial of PARP1 inhibitors that is aimed at determining the efficiency of the drug in black BC women outside United States.