Sex and base excision repair as key susceptibility factors for alkylation-induced mutations, toxicity and hepatic cancer.

N-Nitrosodimethylamine (NDMA) is present in food, water, and drugs and is considered a probable human carcinogen by the International Agency for Research on Cancer. The mechanism of action of NDMA involves the generation of carcinogenic methyl lesions such as 3-methyladenine (3MeA) on DNA bases. Alkyladenine DNA Glycosylase (AAG; a.k.a. N-methylpurine DNA glycosylase, MPG) removes 3MeA to initiate Base Excision Repair, leaving an abasic site that is resolved by backbone cleavage, nucleotide insertion, and backbone ligation. The intermediate steps following base removal produce potentially toxic and mutagenic abasic sites and single-strand DNA breaks. Here, we explored differences between males and females regarding downstream DNA damage, toxicity, mutations and cancer arising from 3MeA in the livers of WT, Aag(-/-), and Aag-overexpressing (AagTg) mice. We found that males were more susceptible to NDMA-induced mutations (WT and Aag(-/-)) and cancer (all genotypes). In contrast, AagTg females were more prone to micronucleus induction. As we showed in our prior analyses where data were pooled for males and females, Aag(-/-) mice were significantly more susceptible to NDMA-induced mutations and cancer, and AagTg mice displayed significantly greater toxicity. Building on these findings, our analyses of sex-related differences show that Aag deficiency and maleness are both susceptibility factors for NDMA-induced hepatic cancer, while Aag overexpression drives toxicity, potentially with a greater effect in females. This study reveals a deeper understanding of the underpinnings for a well-known increased risk of hepatic cancer in men versus women by demonstrating a higher susceptibility of male mice to both mutations and cancer.