The hypothesis to be tested in this Project is that caffeine, caffeine metabolites and tea polyphenols and their metabolites inhibit cell transformation, and tumor phenotype, and induce apoptosis synergistically or additively through targeting different signal transduction molecules. Caffeine, tea polyphenols and other tea components have been shown to inhibit carcinogenesis in rodent and cell culture models. Our goal in this Project is to identify the molecular mechanisms/targets of anti-tumor effects exhibited by caffeine and its metabolites, tea polyphenols and their metabolites, and other tea components. We will use the JB6 mouse epidermal cells, a transformed mouse tumor cell line (RTIOl), a keratinocyte carcinoma cell line (PDV), and cells derived from gene knockout mice (e.g., p53 minus) to examine the anti-tumor promotion and anti-tumor phenotype activity of tea polyphenols, caffeine and their derivatives.
The specific aims to address the hypothesis are: (1) To investigate the inhibition of cell transformation by caffeine, tea polyphenols, their metabolites, and their combinations in cell lines (JB6, RTIOl and PDV). (2) To determine whether inhibition of tumor promoter-induced cell transformation by caffeine metabolites, EGCG, and their combinations is through the modulation of AP-l, NF-kB or other signal transduction pathways. (3) To determine whether apoptosis is involved in the inhibition of cell transformation by caffeine, tea polyphenols and their metabolites and to determine which signal transduction mediates the induction of apoptosis. (4) To determine the structure-effect relationship of caffeine derivatives for inhibition of AP-1 and NF-kB activities and cell transformation. We have established experimental conditions through preliminary studies. These molecular mechanism studies are designed to lead to the development of better chemopreventive agents and to design more effective chemoprevention trials.
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