Nutritional wheat alpha-amylase/trypsin inhibitors promote azoxymethane/dextran sulfate sodium-induced colonic tumorigenesis via enhancing mucosal inflammation

Background and aims:

Inflammatory bowel disease (IBD) is a grave health problem with a complex genetic and environmental etiology that can severely compromise the quality of life in many aspects. IBD patients are threatened by long-term complications, including increased susceptibility to colorectal cancer (CRC) development. Inflammation is a critical player in the development of both colitis-associated and sporadic colon cancers. Several studies suggest that nutrients and/or microbes contribute to inflammation and therefore tumorigenesis, but specific components remain elusive. We studied the effects of wheat ATIs, nutritional activators of toll like receptor 4 and a constituent of most diets, on azoxymethane and dextran sulfate sodium (AOM/DSS)-induced carcinogenesis in mice.

Methods and Results:

C57BL/6 mice were fed a diet with standard chow (gluten/ATI; 25% of protein) or a gluten/ATI-free diet for 4 weeks. To induce experimental colitis-associated tumorigenesis, a single i.p. injection of AOM (7,4 mg/kg) was followed by 3 cycles of DSS administration (2.5% in drinking water) for 1 week, followed by 2 weeks of regular water. Tumor development was monitored by the Colorview endoscopic system. Gluten/ATI and ATI fed mice developed significantly more and larger tumors compared to gluten/ATI-free mice after AOM/DSS treatment. H&E staining of colon sections showed multiple large tumors and increased infiltration of inflammatory cells in gluten/ATI fed mice. RT-PCR analysis indicated that ATI feeding significantly increased the expression of proinflammatory cytokines like IL-1β, IL-6 and TNFα in the colonic mucosa of AOM/DSS treated mice. Immunhistostology showed a dramatic elevation of myeloperoxidase, F4/80-positive macrophages compared to mice on an ATI free diet. Gluten alone had no significant effect on tumor growth and inflammation.

Conclusions:

This study demonstrates that dietary ATIs diet promote colonic tumorigenesis, likely by enhancing macrophage influx and inflammation.