Cancer chemopreventive effect of orally administrated lupane-type triterpenoid on ultraviolet light B induced photocarcinogenesis of hairless mouse

Ultraviolet light is the most common cause of skin cancers in human and several effects of ultraviolet light B (UVB) are thought to contribute to skin photocarcinogenesis. The generation of seven triterpenoids from the cones of Liquidamber styraciflua (Hamamelidaceae were examined for their nitric oxide (NO) scavenging activity as the first screening of an in vivo mouse skin anti-initiating assay. 3β,25-epoxy-3α-hydroxylup-20(29)-en-28-oic acid (1), which showed the strongest inhibitory effect among these compounds, was studied further for its anti-tumor initiating activity on mouse models initiated with ultraviolet-B (UVB) and promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA). Oral administration of the compound 1 during a period before and after the three times of UVB irradiation exhibited a remarkable effect: administration of 0.0025% solution of the compound 1 given orally only to the test group, which started 1 week before and ended 1 week after the irradiation, showed approximately 50% inhibition of tumor incidence and tumor multiplicity in comparison to the control group. Thus, compound 1 could act as a potent anti-tumor initiator in UVB radiation photocarcinogenesis.