Chemoprevention of cancer

In this short article, we review the conceptual basis for chemoprevention o f cancer, the proven clinical efficacy of this concept, and current trends to develop new chemo-preventive agents based on understanding of their mech anisms of action. Four classes of new agents, namely selective inhibitors o f cyclooxygenase-2, selective estrogen receptor modulators, rexinoids (reti noids that bind selectively to the receptors known as RXRs) and ligands for the peroxisome proliferator-activated receptor-gamma are discussed in deta il. The importance of developing totally new classes of chemopreventive age nts is stressed, with particular emphasis on the potential usefulness of ne w synthetic triterpenoids derived from naturally occurring molecules.