New aspects of cancer prevention with green tea catechin.

A96

Since 1983, we have studied cancer prevention with green tea. The significance of green tea catechins is being increasingly recognized with regard to clinical cancer prevention. This paper dealts with two main topics: the synergistic effect by multiple administrations of green tea catechin and the direct binding of EGCG to both DNA and RNA molecules. Japanese drink green tea throughout the day. We studied the enhanced effects of duplicate administrations at molecular level. Human lung cancer cell line A549 cells were treated with EGCG from one to four times at 6 h intervals. The expression of growth arrest and DNA damage-inducible gene GADD153 was continuously enhanced depending on increased administrations, and that of p21 was also enhanced. We think that this synergistic effect by multiple administrations plays a significant role in human cancer prevention with green tea beverage in Japan. Based on our previous observation that nucleic acids extracted from catechin-treated cells are colored, we studied whether catechins directly interact with nucleic acid using surface plasmon resonance assay (Biacore assay) and cold spray ionization mass spectrometry (CSI-MS). The Biacore assay indicated that four catechins, such as EGCG, ECG, GCG, and CG bound to DNA oligomers, and CSI-MS analysis showed one to three EGCG molecules bound to single strand 18 mers of DNA and RNA. These results suggest that multiple binding sites of EGCG are present in DNA and RNA, and that both DNA and RNA molecules can act as biological reservoirs for EGCG.