Impact of DNA Repair Genes Polymorphisms on Incidence and Prognosis of Breast Cancer in an Egyptian Cohort

Background: Sporadic breast cancer might be caused by low-penetrance genes, including genes constituting the DNA repair pathways. Defective DNA repair is a common imprint of cancer that promotes the accretion of DNA errors and genomic instability. The clustering of damage in DNA may stimulate breast carcinogenesis. Aims: The goal of the study is to evaluate the role of single nucleotide polymorphisms in DNA repair genes XRCC1 Arg399Gln, XPD Lys751Gln, RAD51 G135C and XRCC3 Thr241Met as genetic indicators of susceptibility to breast cancer and to evaluate their role in treatment outcome. Methodology: The study included 248 females diagnosed with primary breast cancer and 232 normal healthy females. Patients were clinically followed up for 5 years after completing chemotherapy. Genomic DNA was isolated and the four polymorphisms under investigation were assessed by PCR-RFLP technique. Findings: XRCC1 399Gln, XPD 751Gln and XRCC3 241Met alleles were significantly associated with breast cancer risk (OR = 2.63, 2.17 and 3.21; respectively), with carriers having lower disease free survival (DSF). When grouping patients based on the number of affected genotypes they carry, DFS decreased as the number of affected genotypes increased (PaccumConclusion: XRCC1 Arg399Gln, XPD Lys751Gln and XRCC3 Thr241Met polymorphisms may take a significant part in sporadic breast cancer as risk factors and in prognosis, where patients carrying XRCC1 Arg/Arg, XPD Lys/Lys and XRCC3 Thr/Thr genotypes had significantly diminished risk for breast cancer and higher DFS. DFS decreased as the number of affected genotypes increased. But RAD51 5'UTR G135C polymorphism did not associate with either risk or prognosis of breast cancer.