Cyclohexane, a frequently used
solvent in industry, was assessed for its tumorigenic potential on mouse skin following multistage initiation-promotion protocols. The activity of
ornithine decarboxylase (ODC), a marker of
tumor promotion was found to be induced by the topical application of
cyclohexane. This ODC induction was dependent on the dose of
cyclohexane used and the duration of application. Effect of
protein synthesis inhibitors and the modifiers of
tumor promotion on the
cyclohexane induced ODC activity was also studied. ODC induction was inhibited by
cycloheximide and also, up to some extent, by
actinomycin D. Inhibitors of stage II
tumor promotion showed more effect on the ODC induction by
cyclohexane as compared to the inhibitors of stage I
tumor promotion. In chronic animal bioassay experiments topical application of
cyclohexane to DMBA initiated mouse skin resulted in just 10% of
tumor bearing animals while prior application of TPA for two weeks resulted in 45% of
tumor bearing animals. Collectively, the present study demonstrates that
cyclohexane is more effective as a stage II
tumor promoter over mouse skin and possibly affects the biochemical events at the molecular level.