Inhibitory effect of green tea on tumorigenesis by chemicals and ultraviolet light

Topical application of a green tea polyphenol fraction inhibited 12-O-tetradecanoyl-phorbol-13-acetate-induced tumor promotion in CD-1 mice previously initiated with 7,12-dimethylbenz[a]anthracene (DMBA). Oral administration of a green tea infusion as the sole source of liquid sustenance to SKH-1 mice inhibited ultraviolet B light (UVB)-induced sunburn lesions, UVB-induced initiation of skin tumors, UVB-induced formation of skin tumors in mice previously initiated with DMBA, and nitrosodiethylamine-induced forestomach and lung tumors in A/J mice. In addition to inhibiting UVB-induced formation of skin tumors in DMBA-initiated mice, oral administration of green tea markedly decreased tumor size.