Skin cancer chemoprevention.

Chemoprevention of cancer is a means of cancer control in which the occurrence of this disease, as a consequence of exposure to carcinogenic agents, can be entirely prevented, slowed, or reversed by the administration of one or several naturally occurring or synthetic agents. Thus, the chemoprevention of cancer differs from therapy in that the goal of prevention is to lower the rate of cancer incidence. Such chemopreventive agents are also known as anticarcinogens, and an ideal agent should have (i) little or no untoward or toxic effects, (ii) high efficacy against multiple sites, (iii) capability of oral administration, (iv) a known mechanism of action, (v) low cost, and (vi) human acceptance. With regard to naturally occurring agents, fruits, vegetables, and common beverages, as well as several herbs and plants, have been identified as rich sources of cancer chemopreventive agents. While a wide range of laboratory studies has identified many compounds, including several polyphenols, as cancer chemopreventive agents, in this article our main emphasis is on the cancer chemopreventive potential of a polyphenolic fraction isolated from green tea and silymarin, a flavonoid present in artichoke, against different stages of mouse skin multistage carcinogenesis. We also highlight studies related to retinoid effects on prevention of human skin cancers.