Previous research from our lab shows that an enteric release formulation of rapamycin, eRapa, enhances the lifespan of mice mutated for adenomatous polyposis coli (Apc) tumor suppressor (ApcMin/+ mice), which normally develop intestinal cancer. Although the polyps are believed to originate from stem cells, our results suggest involvement of Paneth cells in tumor prevention perhaps by signaling changes in the niche. These are novel effects of rapamycin and help define its mechanisms of cancer prevention.