Chemoprevention of oral cancer by green tea.
Hsu SD; Singh BB; Lewis JB; Borke JL; Dickinson DP; Drake L;
Caughman GB; Schuster GS
Gen Dent 2002 Mar-Apr;50(2):140-6
Green tea has been a popular beverage for many centuries. Only recently,
however, has the anti-cancer power of green tea constituents been unveiled.
Green tea polyphenols are found to induce apoptosis (programmed cell death)
in many types of tumor cells, including oral cancer cells. However, mechanisms
that enable normal cells to evade the apoptotic effect still are not understood.
In this study, cell growth and invasion assays combined with apoptosis
assays were used to examine the effects of green tea extracts, green tea
polyphenols, and the most potent green tea polyphenol, (-)-epigallocatechin-3-gallate
(EGCG), on normal human keratinocytes and oral carcinoma cells. The results
showed that green tea and its constituents selectively induce apoptosis
only in oral carcinoma cells, while EGCG was able to inhibit the growth
and invasion of oral carcinoma cells. These differential responses to
green tea and its constituents between normal and malignant cells were
correlated with the induction of p57, a cell cycle regulator. These data
suggest that the chemopreventive effects of green tea polyphenols may
involve a p57 mediated survival pathway in normal epithelial cells, while
oral carcinoma cells undergo an apoptotic pathway. Therefore, regular
consumption of green tea could be beneficial in the prevention of oral