Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Clinical and Chemical Pathology

Genetic polymorphisms in homologous recombination repair genes are generally associated with increased cancer risk. The aim of the present study was to evaluate associations between the risk of breast cancer and single nucleotide polymorphisms in the genes, encoding two key proteins of the homologous recombination repair: Rad51 (the human homologue of the E. Coli RecA protein), and X - ray cross complementing group (XRCC3). Moreover, it aimed to correlate genotypes with tumor type, stage, histopathological grade as well as estrogen and progesterone receptors status of the surgically removed breast lesions. The polymorphisms studied were G135C of the Rad51 gene (rs1801320), and C241T of the XRCC3 gene (rs861539). The Rad51 polymorphism was genotyped by PCR - RFLP method, while the XRCC3 polymorphism was genotyped by real time Taqman assay, in 50 breast cancer patients and 50 healthy age matched controls selected from national cancer institute. In the present study, we showed the association between Rad51 G135C polymorphism and the incidence of breast cancer (OR = 10.6, 95%CI [3.0 - 33.9], pvalue < 0.0001), especially advanced tumor stages (Pvalue = 0.0009), but found no significant association with C241T XRCC3 polymorphism. Patients having combined RAD51 G / C and XRCC3 C / T mutation were at a higher risk of breast cancer (OR = 4.69, 95%CI [1.93 - 11.41], Pvalue < 0.0001). This study revealed a link between single nucleotide polymorphism of Rad51 gene with the risk of breast cancer in Egyptian Females, this polymorphism may be regarded as a predictive factor of sporadic breast cancer in Egyptian female population

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