Female CD-1 mice were initiated with a single topical application of 7,12-dimethylbenz[a]
anthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate. Mice with established
papillomas were then treated with
black tea or decaffeinated
black tea (approximately 4 mg
tea solids/ml) as the sole source of drinking fluid for 11-15 weeks. In four separate experiments,
oral administration of
black tea inhibited the growth of
papillomas (increase in
tumor volume/mouse) by an average of 35%, 37%, 41% and 48%, respectively. Studies with decaffeinated
black tea gave inconsistent results. In one experiment, administration of decaffeinated
black tea inhibited
papilloma growth (increase in
tumor volume/mouse) by 27%, but in two additional experiments
papilloma growth was stimulated by 14% and 193%, respectively. In a separate experiment, skin
tumors were generated by treating SKH-1 female mice with ultraviolet B light (UVB; 30 mJ/cm2) twice weekly for 22 weeks, after which UVB administration was stopped.
Tumors were allowed to develop during the following 13 weeks, and
tumor-bearing mice were then treated with
black tea (6 mg/ml
tea solids) as the drinking fluid for 11 weeks. In this experiment,
tumor growth (increase in
tumor volume/mouse) was inhibited by 70%. Histological examination revealed that
tea-treated mice had a 58% decrease in the number of nonmalignant
tumors (primarily
keratoacanthomas)/mouse and a 54% decrease in the number of
squamous cell carcinomas/mouse. In addition, administration of
black tea decreased the volume per
tumor by 60% for nonmalignant
tumors and by 84% for
carcinomas. Mechanistic studies with
tumors from these mice revealed that administration of
black tea decreased the
bromodeoxyuridine labeling index in
squamous cell papillomas,
keratoacanthomas and
squamous cell carcinomas by 56%, 45% and 35%, respectively, and the apoptosis index was increased by 44%, 100% and 95%, respectively. Administration of
black tea decreased the mitotic index in
keratoacanthomas and
squamous cell carcinomas by 42% and 16%, respectively. The results indicate that
oral administration of
black tea to
tumor-bearing mice inhibited proliferation and enhanced apoptosis in nonmalignant and malignant skin
tumors.