Tea consumption is associated with a reduced risk of mammary cancer as reflected by epidemiological studies and experiments in carcinogen-induced rodent models of mammary carcinogenesis. We tested the hypothesis that green tea catechins (GTC) or theaflavins from black tea (BTT) interfere with mammary carcinogenesis in C3(1) SV40 T,t antigen transgenic multiple mammary adenocarcinoma (TAg) mice and that GTC/BTT affect tumor survival or oxidation status. TAg mice received GTC/BTT (0.05%) in drinking water for their lifetime. As compared to control mice, they survived longer and had smaller tumors. On microscopic inspection, the size of the largest tumor per mouse was decreased by 40-42% (p < 0.01). GTC (0.01%) and BTT (0.05%) increased levels of cleaved caspase 3 in tumor tissue by 67 and 38%, respectively (p < 0.05), intimating increased apoptosis. Tumor levels of the malondialdehyde-DNA adduct M(1)dG in mice receiving GTC or BTT (0.05%) were reduced by 78 (p < 0.001) or 63% (p < 0.05), respectively, as compared to controls. The results render the exploration of the breast cancer chemopreventive properties of tea preparations in humans worthwhile.

2254 Polyphenolic constituents contained in green tea impair proliferation and survival of neoplastic cells in vitro and prevent cancer in rodents including that of the mammary gland. Epidemiological studies suggest that high consumption of green tea is associated with a delay in breast cancer recurrence. Much less is known about the potential cancer chemopreventive properties of black tea constituents. The aim of this study was to compare the effect of a defined extract of black tea (BTT) consisting predominantly of theaflavins, with that of green tea extract (GTC), containing mainly catechins such as epigallocatechin gallate. The pharmacological properties of BTT and GTC were explored in the C3(1)/SV40 T/t-antigen transgenic (Tag) mouse model of mammary carcinogenesis. Female Tag mice develop mammary tumours characterised by inactivated tumour suppressor genes p53 and Rb, thus mimicking an insidious hormone-insensitive form of human breast cancer (Maroulakou et al, Proc. Natl. Acad Sci. 91, 11236, 1994). Mice (10 per group) received drinking water (controls) or drinking water containing BTT or GTC (0.05%) from weaning to the end of their lifetime. Animals were sacrificed when tumours exceeded 17 mm in diameter, which served as the experimental endpoint. Intervention with either BTT or GTC increased Tag mouse survival. When average age (days) at death was compared, the differences between control (143.5 ± 8.25) on the one side, and BTT (154 ± 16.83) or GTC (151.2 ± 8.22) on the other were significant (p