ABSTRACT
Black tea and green tea are major beverages worldwide and have been shown to possess some benecial health effects. Polyphenolic compounds and caffeine are major constituents of tea. Following a single topical application, 12-O-tetradecanoylphorbol-13-acetate (TPA) was found to induce a time-and dose-dependent increase in edema as well as formation of the proinammatory cytokines interleukin-1 (IL-1)
9.1 Introduction ................................................................................................. 161 9.2 Health Effects of Tea and Tea Polyphenols ................................................ 163 9.3 Biochemical and Molecular Mechanisms of Cancer Chemoprevention
by Tea and Tea Polyphenols ........................................................................ 163 9.3.1 Antioxidative Effects and Scavenging of Reactive Oxygen
Species ............................................................................................. 166 9.3.2 Suppression of Tumor Proliferation through Mitogenic
Signaling Blockade .......................................................................... 166 9.3.3 Inhibition of MAPK Signaling ........................................................ 167 9.3.4 Inhibition of PI3K Pathway.............................................................. 167 9.3.5 Inhibition of Cell Cycle Progression ................................................ 167 9.3.6 Suppression of iNOS Signaling ....................................................... 168 9.3.7 Suppression of NF-κB Activation through Downregulating IκB
Kinase .............................................................................................. 168 9.3.8 Inhibition of Proteasome Activity.................................................... 169 9.3.9 Inhibition of Matrix Metalloproteinase (MMP) .............................. 169 9.3.10 Induction of Apoptosis ..................................................................... 169 9.3.11 Suppression of Fatty Acid Synthase (FAS) ...................................... 171
9.4 General Remarks on the Mechanisms of Cancer Chemoprevention .......... 171 9.5 Conclusions ................................................................................................. 173 Acknowledgments .................................................................................................. 174 References .............................................................................................................. 174
and IL-6 in mouse ears. Topical application of epigallocatechin 3-gallate (EGCG), theaavin (TF-1), TF-2, and TF-3 before TPA treatment inhibited TPA-induced ear inammation.1 Furthermore, the effect of a dened extract of black tea (black tea theaavins [BTTs]) consisting predominantly of theaavins such as theaavin (TF1), theaavin monogallates (TF-2), and theaavin 3,3'-digallate (TF-3), and that of green tea extract (green tea catechins [GTCs]) containing mainly catechins such as EGCG on the induction of carcinogenesis in animal models has been investigated. The pharmacological properties of BTTs and GTCs were explored in the C3(1)/ SV40T/t-antigen transgenic (Tag) mouse model mammary carcinogenesis.2 Female Tag mice develop mammary tumors characterized by inactivated tumor suppressor genes p53 and Rb, thus mimicking an independent hormone-insensitive form of human breast cancer. Intervention with either BTTs or GTCs increased Tag mouse survival (control, 143.5 ± 8.25; BTTs, 154 ± 16.83; and GTCs, 151.2 ± 8.02) and decreased Tag mouse mammary carcinogenesis.2
