Intestinal inflammatory cytokine response in relation to tumorigenesis in the ApcMin/+ mouse

The etiology of colon cancer is a complex phenomenon that involves both genetic and environmental factors. However, only about 20% have a familial basis with the largest fraction being attributed to environmental causes that can lead to chronic inflammation. While the link between inflammation and colon cancer is well established, the temporal sequence of the inflammatory response in relation to tumorigenesis has not been characterized. We examined the timing and magnitude of the intestinal inflammatory cytokine response in relation to tumorigenesis in the ApcMin/+ mouse. ApcMin/+ mice and wildtype mice were sacrificed at one of 4 time-points: 8, 12, 16, and 20 weeks of age. Intestinal tissue was analyzed for polyp burden (sections 1, 4 and 5) and mRNA expression and protein concentration of MCP-1, IL-1β, IL-6 and TNF-α (sections 2 and 3). The results show that polyp burden was increased at 12, 16 and 20 weeks compared to 8 weeks (P < 0.05). Gene expression (mRNA) of MCP-1, IL-1β, IL-6 and TNF-α was increased in sections 2 and 3 starting at week 12 (P < 0.05), with further increases in MCP-1, IL-1β and IL-6 at 16 weeks (P < 0.05). Protein concentration for these cytokines followed a similar pattern in section 3. Similarly, circulating MCP-1 was increased at 12 weeks (P < 0.05) and then again at 20 weeks (P < 0.05). In general, overall polyp number and abundance of large polyps were significantly correlated with the inflammatory cytokine response providing further support for a relationship between polyp progression and these markers. These data confirm the association between intestinal cytokines and tumorigenesis in the ApcMin/+ mouse and provide new information on the timing and magnitude of this response in relation to polyp development. These findings may lead to the development of inflammatory mediators as important biomarkers for colon cancer progression. Further, these data may be relevant in the design of future investigations of therapeutic interventions to effectively target inflammatory processes in rodent models.

► We examined the timing and magnitude of the intestinal inflammatory cytokine response in relation to tumorigenesis in the ApcMin/+ mouse. ► An elevation in inflammation occurs at 12 weeks of age in association with a rapid increase in polyp number. ► Further enhancements in inflammatory cytokines with age were associated with increased polyp size.