Overt Increase of Oxidative Stress and DNA Damage in Murine and Human Colitis and Colitis-Associated Neoplasia

Patients with inflammatory bowel disease (IBD) have a higher risk of developing colitis-associated-cancer (CAC); however, the underlying processes of disease progression are not completely understood. Here, the molecular processes of inflammation-driven colon carcinogenesis were investigated using IL10-deficient mice (IL10 KO). IL10 KO mice were euthanized after development of colitis and dysplasia. IHC was performed for markers of colitis-induced DNA damage (CIDD): oxidative DNA lesions (8-oxoG), double-strand breaks (DSB; H2AX). and DSB repair. MSI, LOH (Trp53, Apc), and global methylation (CIMP) were assessed on microdissected tissue. Comet assay for DNA damage, immunofluorescence, and immunoblotting were performed on intestinal organoids from wild-type (WT) and IL10 KO mice. Sequential biopsies and surgical specimens from IBD and CAC patients were used for IHC analysis. Severity of inflammation correlated with number of dysplasia. 8-oxoG and H2AX-positive cells were significantly increased in inflamed and dysplastic areas along with activation of DSB repair. The amount of positively stained cells strongly correlated with degree of inflammation (8-oxoG: R = 0.923; H2AX: R = 0.858). Neither CIMP, MSI nor LOH was observed. Enhanced DSBs in IL10 KO organoids were confirmed by comet assay and increased expression of H2AX. Human clinical specimens exhibited significantly higher H2AX and 8-oxoG in IBD, dysplasia, and CAC compared with normal mucosa. These data indicate that inflammation-driven colon carcinogenesis in IL10 KO mice and IBD patients is associated with oxidative DNA damage and overt presence of DSB. Mol Cancer Res; 16(4); 634–42. ©2018 AACR.

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