SUPPRESSION OF TUMOR-DEVELOPMENT BY SUBSTANCES DERIVED FROM THE DIET - MECHANISMS AND CLINICAL IMPLICATIONS

The concept that cancer can be prevented, or its onset postponed, by c ertain diet-derived substances is currently eliciting considerable int erest. Agents which interfere with tumour-development at the stage of promotion and progession in particular are of potential clinical value . As chemopreventive agents have to be administered over a long period oi time ill order to establish whether they possess efficacy in human s, it is of paramount importance to establish their lack of toxicity. The desire to select the best chemopreventive drug candidates for clin ical trial, and the necessity to monitor efficacy in the short and int ermediate term, render the identification of specific mechanism-based in vivo markers of biological activity a high priority. Antioxidation, inhibition of arachidonic acid metabolism, modulation of cellular sig nal transduction pathways, inhibition of hormone and growth factor act ivity and activity are discussed as mechanisms by which the soya const ituent genistein, the curry ingredient curcumin and the vitamin A anal ogue 13-cis retinoic acid exert tumour suppression. A better understan ding of these mechanisms will help the establishment of screens for th e discovery of new and better chemopreventive agents and the identific ation of surrogate markers to assess the outcome of clinical chemoprev ention trials.