Azithromycin induces read-through of the nonsense Apc allele and prevents intestinal tumorigenesis in C3B6F1 ApcMin/ plus mice

Therapeutic strategies that promote read-through of a mutant gene have proved effective for certain non-neoplastic diseases. However, the efficacy of this approach is unproven regarding neoplastic diseases with germline nonsense mutations, including familial adenomatous polyposis. Here we examined the cancer -preventive efficacy of the macrolide antibiotic azithromycin, with a reported read-through effect, on intestinal tumorigenesis in C3B6F1 ApcMin/+ mice harboring a nonsense Apc mutation resulting in a truncated Apc protein. Mice were given drinking water lacking azithromycin or containing 0.0125-0.2 mg/mL azithromycin from 3 weeks of age. The small intestine and cecum were analyzed for pathological changes and alterations of intestinal flora. Azithromycin suppressed the number of tumors and the proportion of adenocarcinomas, with the most effective drinking-water concentration being 0.0125 mg/mL. Furthermore, azithromycin recovered the cellular level of full-length Apc, resulting in downregulation of & beta;-catenin and cyclin D1. Conversely, the effect of azi-thromycin on the diversity of the intestinal microbiota depended on the drinking-water concentration. These results suggest that the balance between azithromycin-mediate read-through of mutant Apc mRNA and anti-bacterial effects influences intestinal tumorigenesis. Thus, azithromycin is a potential anticancer agent for fa-milial adenomatous polyposis patients harboring nonsense mutations.