8-hydroxyguanosine and Colorectal-Neoplasms--Hereditary-Nonpolyposis

Inflammatory bowel disease patients have a greatly increased risk of developing colitis-associated colon cancer (CAC); however, the basis for inflammation-induced genetic damage requisite for neoplasia is unclear. Using three models of CAC, we find that sustained inflammation triggers 8-oxoguanine DNA lesions. Strikingly, antioxidants or iNOS inhibitors reduce 8-oxoguanine and polyps in CAC models. Because the mismatch repair (MMR) system repairs 8-oxoguanine and is frequently defective in colorectal cancer (CRC), we test whether 8-oxoguanine mediates oncogenesis in a Lynch syndrome (MMR-deficient) model. We show that microbiota generates an accumulation of 8-oxoguanine lesions in MMR-deficient colons. Accordingly, we find that 8-oxoguanine is elevated in neoplastic tissue of Lynch syndrome patients compared to matched untransformed tissue or non-Lynch syndrome neoplastic tissue. While antioxidants reduce 8-oxoguanine, they do not reduce CRC in Lynch syndrome models. Hence, microbe-induced oxidative/nitrosative DNA damage play causative roles in inflammatory CRC models, but not in Lynch syndrome models.

Topics: Adenomatous Polyposis Coli; Adult; Aged; Aged, 80 and over; Animals; Antioxidants; Carcinogenesis; Colitis; Colon; Colorectal Neoplasms; Colorectal Neoplasms, Hereditary Nonpolyposis; Dextran Sulfate; Disease Models, Animal; DNA Damage; DNA Repair; Dysbiosis; Escherichia coli; Female; Guanosine; Helicobacter Infections; Helicobacter pylori; Humans; Inflammation; Interleukin-10; Male; Mice, Inbred C57BL; Middle Aged; Mutation; Oxidative Stress