Consumption of plant-derived food, especially fruits and vegetables, has been linked to decreased risk of cancer. Laboratory studies with animals and cells in culture have shown cancer preventive activity of phytochemicals isolated from soy, tea, rice, noni and many green, yellow and orange fruits and vegetables. We have used cell culture, transgenic mice and knockout mice models to examine the anti-cancer effects of these dietary factors at the molecular level. We have found tha: (1) (-)-Epigallocatechin gallate (EGCG), the major active pohlyphenol in green tea, and theaflavins, the major active components in black tea, inhibit epidermal growth factor (EGF)- or 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced AP-1 and NFΚB-dependent transcriptional activation. (2) Active compound from rice and other grains, inhibited TPA- or EGF-induced transformation and signal transduction through its effects on PI3 kinase. (3) Resveratrol inhibited cell transformation through the induction of apoptosis, mediated through JNK pathways. (4) Phenethyl isothiocyante (PEITC) inhibited cell transformation, correlated with the induction of apoptosis. An elevation of p53 is required for PEITC-induced apoptosis. (5) Chemicals in ginger and hot pepper showed inhibition of AP-1 and cell transformation and apoptotic pathways in cells. Our studies indicated that the chemopreventive effect of these food pheolics may be mediated by their effects on different signal transduction pathways.
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