ORF09-04 - DNA Repair Deficiencies in Men with Non-Obstructive Azoosperima

Non-obstructive azoospermia (NOA; spermatogenic failure) represents one of the most severe forms of male factor infertility, as there are only a few costly treatments that can be attempted (testicular sperm extraction [TESE] with intracytoplasmic sperm injection, ICSI). The etiology of NOA is not fully understood. This study addresses a major “Grand Challenge” question in male reproductive medicine today. Namely, is the increased cancer risk for infertile men predominantly present in men with spermatogenic failure, and what is the common genetic/epigenetic link between their infertility and health risks? Infertility presents a significant risk for the development of other diseases. Poor semen quality predicts a variety of health conditions, including cancer. Using assays of genomic instability, as well as studies of proteins involved in mismatch and homologous recombination, involving testicular fibroblasts cultured from NOA and control fertile men exposed to alkylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), mitomycin C, MMC or N-methyl-N-nitroso urea, MNU to cells, induces an 06-MeG:T mismatch that becomes an A:T transition mutation. The cells must recognize the mismatch, and if not repaired the resulting highly toxic DNA doublestrand breaks induce apoptosis. Cells deficient in mismatch repair and homologous recombination exhibit DNA allkylating tolerance, unlike cells with normal DNA repair. Of the 114 control men with normal spermatogenesis, 3 of 144 men tested were apoptosis tolerant and alkylating agent expsoure. In contrast, 141 of 204 NOA men's cell were apoptosis tolerant (!69%) indicating deficiencies of DNA repair (Fisher Exact < 0.001). A different assay using the radiometric drug, neocarzinostatin exposure (for double-strand DNA break repair) were used identifying a subset of NOA men with homologous recombination defiiencies. Mutations in MLH1 and MSH2 were identified in 112 NOA men and 3% of a different cohort of 371 NOA and cryptozoospermic men displayed MSH5 gene mutations. Frequency of damaging MSH5 mutations in the general population is 0.4% and Approximately 1 in 279 people (0.4%) in the general population carry mutations in MMR genes (MLH1 = 1 in 1,946, MSH2 = 1 in 2,841, MSH6 = 1 in 758, PMS2 = 1 in 714). This data suggests that Mismatch and homologous recombintation/Double-Strand Break repair (including but not limited to MLH1 and MSH5 deficiency) underlies a significant percentage of male infertility in men with spermatogenic failure. Because deficiencies of these DNA repair genes and others underlies Lynch syndrome and development of other malignancies, the data suggests that these DNA repair deficiencies may contribute to the increased cancer risks reported in infertile men in general and men with NOA in particular. Supported in part by 1R01CA290670 from the National Cancer Institute, National Institutes of Health