PARP1 and breast carcinoma: Further, later studies demonstrated the ability of PARP inhibitors to successfully target tumors that exhibit mutations in the breast cancer 1, early onset protein (BRCA1), a tumor suppressor protein that is involved in the maintenance of genomic integrity (20) and the breast cancer 2, early onset protein (BRCA2), a protein involved in DNA double strand break repair and homologous recombination (21).