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 carcinogenesis model. TPA promotion was under-taken for 6, 18 and 24 weeks, respectively. Proliferating activity was observed immunohistochemically and the ornithine decarboxylase (ODC) mRNA level was analyzed by reverse transcriptase-polymerase chain reaction. Messenger RNAs for c-fos, c-jun and jun-B were also observed. CHL treatment clearly reduced proliferating activity and the level 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 expression. These results indicate that the promotion stage of each target tissue should be considered in a chemopreventive program.