Carotenoids in cancer chemoprevention and therapeutic interventions.

Carotenoid (CARs: beta-carotene BC and/or canthaxanthin CX) supplementation have been shown to be chemopreventive in animals, since 1980, against direct or indirect chemical carcinogenesis/photo-carcinogenesis of the skin, breast, stomach, salivary glands, colon-rectum, urinary bladder, and against transplanted tumors. This action could be either independent of or dependent on pro-vitamin A activity of BC. In vitro, both BC and CX proved to be antimutagenic and to have anti-malignant transformation properties in cell cultures. Preliminary interventions in humans with BC +/- CX prevented the onset of second primary tumors in lung, colon, urinary bladder, and head and neck. The powerful antioxidant properties of CARs, possibly associated with their retinoid potential, played a role in all the above observations, producing free-radical quenching and immunostimulation.(ABSTRACT TRUNCATED AT 250 WORDS)