Effects of 2-phenyl-1,4-benzoquinone and 2,5-dihydroxybiphenyl on two-stage mouse skin carcinogenesis

Abstract

Two metabolites of sodium o-phenylphenate (OPP-Na), 2-phenyl-1,4-benzoquinone (PBQ) and 2,5-dihydroxybiphenyl (5-OH), were examined for initiating, promoting or complete carcinogenic activity for skin carcinogenesis in female CD-1 mice. While PBQ treatment (1 mg per mouse, twice a week for 34 weeks) did cause sustained hyperplasia like 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment (2.5 μg, twice/week for 34 weeks), it showed weak, but not statistically significant, tumor promoting potential for skin tumor development initiated with 7,12-dimethylbenz[a]anthracene (DMBA, 10 μg × 10 in 5 weeks). On the other hand, 5-OH applied at a dose of 10 mg/mouse using a similar protocol did not exert any promoting influence, and neither of these chemicals administered continually for 40 weeks without prior DMBA initiation treatment induced any skin tumors. Furthermore, both chemicals applied 10 times in 5 weeks at higher doses (2 mg for PBQ and 20 mg for 5-OH) in association with subsequent TPA treatment did not initiate any skin tumor development. Thus, neither of the OPP-Na metabolites demonstrated any capacity to influence skin tumor development in any manner, despite the fact that OPP-Na itself was previously found to exert skin tumor promoting potential in the mouse.