Troglitazone, a Ligand for Peroxisome Proliferator‐activated Receptor γ Inhibits Chemically‐induced Aberrant Crypt Foci in Rats

The biological roles of peroxisome proliferator‐activated receptors (PPARs) in various diseases, including inflammation and cancer, have been highlighted recently. Although PPARγ ligand is suspected to play an important role in carcinogenesis, its effects on colon tumorigenesis remain undetermined. The present tune‐course study was conducted to investigate possible modifying effects of a PPARγ ligand, troglitazone, on the development and growth of aberrant crypt foci (ACF), putative precursor lesions for colon carcinoma, induced by azoxymethane (AOM) or dextran sodium sulfate (DSS) in male F344 rats. Oral troglitazone (10 or 30 mg/kg body weight (b.w.)) significantly reduced AOM (two weekly subcutaneous injections, 20 mg/kg b.w.)‐induced ACF. Treatment with troglitazone increased apoptosis and decreased polyamine content and ornithine decarboxylase (ODC) activity in the colonic mucosa of rats treated with AOM. Gastric gavage of troglitazone also inhibited colitis and ACF induced by DSS (1% in drinking water), in conjunction with increased apoptosis and reduced colonic mucosal polyamine level and ODC activity. Our results suggest that troglitazone, a synthetic PPARγ ligand, can inhibit the early stage of colon tumorigenesis with or without colitis.