Light-induced Skin Carcinogenesis in 7,12-Dimethylbenz[ Tea, and Decaffeinated Green Tea on Ultraviolet B Inhibitory Effects of Black Tea, Green Tea, Decaffeinated Black

In a previous study (Z Y. Wang et ci., Cancer Res., 52: !!62—1!70, !992),wefoundthatadministrationof a waterextractof greentealeaves as the sole source of drinking fluid inhibited ultraviolet B light (UVB) Induced carcinogenesis in SKH-! mice previously Initiated with 7,12dimethylbenz[alanthncene (DMBA). In the present study, we compared the effects of black tea, green tea, decaffeinated black tea, and decaffein ated green tea on UVB-lnduced skin carclnogenesis In DMBA-inltiated SKH-! mice. A 1.25% water extract of each kind of ten leaf (US g tea leaf/100 ml water) was prepared by passing 4 liters of hot water through 50g of tealeavesIn a Burntteabrewingmachine. Themeanconcentra dons of solids in multiple samples of 1.25% black tea, green tea, decal feinated black tea, and decaffeinated green tea analyzed during the course of this study were 4.23, 3.94, 3.66, and 3.53 mg/ml, respectively. These concentrations of tea solids are similar to those present in tea brews ingested by humans. Female SKH-! mice were treated topically with 200 nmol of DMBA, followed 3 weeks later by Irradiation with 30 mJ/cm2 of UVB twice weekly for 3! weeks. UVB-Induced formation of skin tumors was markedly inhibited by oral administration of0.63 or 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea as the sole source of drinking fluid 2 weeks prior to and during 3! weeks of UVB treatment. Administration of each of the eight tea preparations not only inhibited the number of tumors, but tumor size was also markedly de creased. Histopathological examination of each tumor showed that oral administration of the eight tea preparations had a marked Inhibitory effect on the formation of UVB-induced keratoacanthomas and carcino mas AdmInistration of 1.25% black tea, green tea, decaffeInated black tea, or decaffeinated green tea inhibited the number of keratoacanthomas per mouse by 79, 78, 73, or 70%, respectively, and the number of card nomas per mouse was Inhibited by 93, 88, 77, or 72%, respectIvely. In summary, administration of black tea was comparable to green tea as an inhibitor of UVB-induced skin carcinogenesis in DMBA-iaitiated SKH-! mice. Oral administration of decaffeinated black tea or decaffeinated green tea also had a marked inhibitory effect on UVB-induced skin carcinogenesis in DMBA-lnitiated SKH-! mice, but these tea preparations were slightly less effective than the regular teas at the high dose leveL