Delay of breast carcinogenesis by green tea catechins and black tea theaflavins in the C3 (1) SV40 T/t antigen (Tag) transgenic mouse model
The aim of this study was to compare the efficacies of an extract of black tea (BTT) consisting predominantly of theaflavins with that of a green tea extract (GTC), containing mainly catechins. BTT/GTC reduced proliferation and increased apoptosis and malondialdehyde DNA adduct levels (M1dG) in breast cancer cells in vitro. 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. Mice received drinking water (controls) or drinking water containing BTT or GTC (0.05%/0.01%). Intervention with either BTT or GTC (0.05%) increased Tag mouse survival accompanied with a decrease in tumour volume and tumour burden. Microscopic evaluation revealed that GTC or BTT consumption decreased the size4 of the largest lesion compared to controls.;Increased survival was accompanied by a reduction in proliferation and an increase in apoptosis, as reflected by a decrease in PCNA levels and an increase in cleaved caspase 3 levels. Both tea extracts reduced tumour M1dG adduct levels. The results intimate that both GTC and BTT delay mammary tumour development in the Tag mouse model and M1dG and apoptotic signalling molecules may perhaps constitute suitable biomarkers of efficacy.