Effects of Tea Polyphenols on the Signal Transduction Pathways

Mitogenic stimulation is likely to be an important component of tumor promotion. However, that alone is not sufficient for transformation, and changes in gene expression are required to avoid growth regulation or differentiation. In general, alterations in the transcription of a specific set of cellular genes are mediated by specific regulatory DNA binding proteins or transcription factors that regulate gene expression directly by binding to specific DNA sequences in promoter regions (1, 2, 3, 4, 5, 6, 7, 8, 9). The expression of genes transcriptionally induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) and other tumor promoters such as UV irradiation are thought to be required in tumor promotion (4, 5, 6, 7, 8, 9, 10).