The Mbd4 DNA glycosylase protects mice from inflammation-driven colon cancer and tissue injury

Much of the global cancer burden is associated with longstanding inflammation accompanied by release of DNA-damaging reactive oxygen and nitrogen species. Here, we report that the Mbd4 DNA glycosylase is protective in the azoxymethane/dextran sodium sulfate (AOM/DSS) mouse model of inflammation-driven colon cancer. Mbd4 excises T and U from T:G and U:G mismatches caused by deamination of 5-methylcytosine and cytosine. Since the rate of deamination is higher in inflamed tissues, we investigated the role of Mbd4 in inflammation-driven tumorigenesis. In the AOM/DSS assay, Mbd4[superscript –/–] mice displayed more severe clinical symptoms, decreased survival, and a greater tumor burden than wild-type (WT) controls. The increased tumor burden in Mbd4[superscript –/–] mice did not arise from impairment of AOM-induced apoptosis in the intestinal crypt. Histopathological analysis indicated that the colonic epithelium of Mbd4[superscript –/–] mice is more vulnerable than WT to DSS-induced tissue damage. We investigated the role of the Mbd4[superscript –/–] immune system in AOM/DSS-mediated carcinogenesis by repeating the assay on WT and Mbd4[superscript –/–] mice transplanted with WT bone marrow. Mbd4[superscript –/–] mice with WT bone marrow behaved similarly to Mbd4[superscript –/–] mice. Together, our results indicate that the colonic epithelium of Mbd4[superscript –/–] mice is more vulnerable to DSS-induced injury, which exacerbates inflammation-driven tissue injury and cancer.National Institutes of Health (U.S.) (Grant R01-CA075576)National Institutes of Health (U.S.) (Grant R01-CA055042)National Institutes of Health (U.S.) (Grant R01-CA149261)National Institutes of Health (U.S.) (Grant P30-ES000002)National Institutes of Health (U.S.) (Grant P30-ES02109)National Institutes of Health (U.S.) (Training Grant in Environamental Toxicology T32-ES007020MIT)American Cancer Society (Postdoctoral Fellowship PF-13-204-01