Chemoprevention by the oxygenated carotenoid beta-cryptoxanthin of N-methylnitrosourea-induced colon carcinogenesis in F344 rats.

Beta-cryptoxanthin (betaCx), one of 4 major carotenoids in the blood, was investigated for anticarcinogenic activity in F344 rats. Four groups of 25 rats each received an intrarectal dose of 2 mg of N-methylnitrosourea 3 times a week for 5 weeks, and were fed the diet supplemented with 0 ppm (control), 25 ppm, 5 ppm or 1 ppm betaCx throughout the experiment. The colon cancer incidence at week 30 was significantly lower in the betaCx (25 ppm) diet group, but not in the betaCx (5 ppm) and betaCx (1 ppm) diet groups, than in the control diet group: 68%, 84%, 80% vs. 96%. The results suggested that dietary betaCx may affect colon carcinogenesis after accumulation in the colonic mucosa, perhaps due to absorption from the colon as well as the small intestine.