Green Tea Catechins: Proposed Mechanisms of Action in Breast Cancer Focusing on the Interplay Between Survival and Apoptosis

Recent data have shown strong chemopreventive and possibly cancer chemotherapeutic effects of green tea polyphenols against cancer. Despite advances in breast cancer treatment, mortality from breast cancer is still high. Undoubtedly novel treatment strategies are needed for chemoprevention of high risk women and for the treatment of receptor negative breast cancer. Green tea catechins have been shown to inhibit proliferation of breast cancer cells and to block carcinogenesis. This review attempts a critical presentation of the mechanisms of action of green tea catechins in breast cancer. Several mechanisms of action of green tea catechins in breast cancer have been proposed including modulation of extracellular signalling, induction of apoptosis through redox regulation, or through modulation of epigenetic alterations. A number of molecular targets of green tea catechins have been suggested i.e molecular chaperones, telomerase, apoptotic cascade. Although the molecular links among the proposed mechanisms of action of green tea catechins are often missing, it must be emphasized that all the proposed mechanisms indicate that green tea catechins inhibit growth and /or promote apoptosis. It would be interesting if future experimental trials could take into account that green tea catechins are multi-target agents and attempt to link every novel proposed target with the other already proposed targets of green tea catechins.