Symposium on mechanisms of action of naturally occurring anticarcinogens

In recent years, it has been suggested that diet is responsible for about one-third of the cancers and, for this reason, the strategy of diet manipulation has become increasingly important as an approach for cancer prevention (Ahmad and Mukhtar, 1999; Katiyar and Mukhtar, 1996; Kohlmeier et al., 1997). The use of tea, especially green tea, for prevention of cancer has only been appreciated in the last ten years. Tea is one of the most popular beverages in the world, and epidemiological and laboratory research has indicated that tea consumption possesses beneficial effects against development of many cancer types. Although compelling evidence is now available in favor of the cancer preventive potential of green tea, a clear understanding of the mechanisms of action is far from complete. As discussed above, it is clear that the green tea polyphenols may modulate multiple signaling pathways that may be responsible for development of cancer. Green tea appears to possess qualities of an ideal chemopreventive agent, since this beverage product (a) induces minimal or no toxic effects, (b) exhibits high efficacy at multiple sites, (c) can be taken by oral administration, (d) induces responses through multiple pathways, (e) has a low cost, and (f) is widely used in the human diet. In view of the available laboratory and epidemiological data, it would be reasonable to evaluate the usefulness of green tea polyphenols in clinical trials with humans. It is noteworthy that clinical trials for evaluating the efficacy of formulated green tea in patients with advanced solid tumors are currently being conducted at many centers around the world.