Anti-promotion effect of chlorophyllin in DMBA-TPA-induced mouse skin carcinogenesis

This study aimed to elucidate the inhibitory effects of chlorophyllin (CHL) at different promotion stages in a DMBA-TPA-induced mouse skin carcinogene sis model. TPA promotion was under-taken for 6, 18 and 24 weeks, respective ly. Proliferating activity was observed immunohistochemically and the ornit hine decarboxylase (ODC) mRNA level was analyzed by reverse transcriptase-p olymerase chain reaction. Messenger RNAs for c-fos, c-jun and jun-B were al so observed. CHL treatment clearly reduced proliferating activity and the l evel of ODC mRNA at the 18-week-promotion stage. When promoted for 24 weeks , CHL was not effective in reducing proliferating activity and ODC mRNA exp ression. These results indicate that the promotion stage of each target tis sue should be considered in a chemopreventive program.