3′-Hydroxypterostilbene Inhibits 7,12-Dimethylbenz[a]anthracene (DMBA)/12-O-Tetradecanoylphorbol-13-Acetate (TPA)-Induced Mouse Skin Carcinogenesis

Background: A natural pterostilbene analogue isolated from the herb Sphaerophysa salsula, 3′-hydroxypterostilbene (HPSB), exhibits antiproliferative activity in several cancer cell lines; however, the inhibitory effects of HPSB on skin carcinogenesis remains unclear. Purpose: The aim of this study was to evaluate the inhibitory effects of HPSB on two-stage skin carcinogenesis in mice and its potential mechanism. Study Design and Methods: This study investigated the anti-inflammatory and anti-tumor effects of HPSB in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated acute skin inflammation and 7,12-dimethylbenz[a]anthracene (DMBA)/TPA-induced two-stage skin carcinogenesis model. In addition, the effects of HPSB on the modulation of the phase I and phase II metabolizing enzymes in the DMBA-induced HaCaT cell model were investigated. Results: The results provide evidence that topical treatment with HPSB significantly inhibits TPA-induced epidermal hyperplasia and leukocyte infiltration through the down-regulation of cyclooxygenase-2 (COX-2), matrix metalloprotein-9 (MMP-9), and ornithine decarboxylase (ODC) protein expression in mouse skin. Furthermore, HPSB suppresses DMBA/TPA-induced skin tumor incidence and multiplicity via the inhibition of proliferating cell nuclear antigen (PCNA), Cyclin B1 and cyclin-dependent kinase 1 (CDK1) expression in the two-stage skin carcinogenesis model. In addition, pretreatment with HPSB markedly reduces DMBA-induced cytochrome P450 1A1 (CYP1A1) and cytochrome P450 1B1 (CYP1B1) gene expression in human keratinocytes; however, HPSB does not significantly affect the gene expression of the phase II enzymes. Conclusion: This is the first study to show that topical treatment with HPSB prevents mouse skin tumorigenesis. Overall, our study suggests that natural HPSB may serve as a novel chemopreventive agent capable of preventing carcinogen activation and inflammation-associated tumorigenesis.