3'-Hydroxypterostilbene 預防小鼠二階段皮膚致癌之起始與促進作用

Abstract

隨著都市化、飲食與生活習慣的改變，全球癌症發生率逐年地提升，因此癌症的預防已成為一個重要的研究主題。腫瘤的形成是一多步驟的過程，牽涉到許多分子層次的改變，其中化學性致癌物質與發炎反應於腫瘤發展上扮演重要的角色，因此阻斷致癌物質活化及抗發炎被視為癌症化學預防的重要策略。3'-hydroxypterostilbene (HPSB) 為 stilbene 化合物的一種，其存在於苦馬豆 (Sphaerophysa salsula) 全株植物中，先前的研究顯示 HPSB 對多株腫瘤細胞的生長有抑制作用，然而其對致癌物質之代謝與抗發炎活性尚未被探討。 因此本研究利用人類角質細胞 (HaCaT) 試驗模式探討 HPSB 對 7,12-dimethylbenz[a]anthracene (DMBA) 代謝酵素之影響，並以 12-O-tetradecanoylphorbol-13-acetate (TPA) 誘發皮膚發炎以及 DMBA/TPA 誘發二階段皮膚致癌之動物模式評估 HPSB 抗發炎與抗癌功效，並深入研究其調節的分子機制。細胞實驗的結果顯示，HPSB 會抑制 DMBA 誘發之 phase I 代謝酵素 cytochrome P450 1A1 (CYP1A1) 與 cytochrome P450 1B1 (CYP1B1) 的基因表現，然而對 Phase II 代謝酵素的基因表現沒有明顯的影響；於 TPA 誘發皮膚發炎模式中，HPSB 可經由降低皮膚促發炎和增生相關蛋白 matrix metalloprotein-9 (MMP-9)、cyclooxygenase-2 (COX-2) 及 ornithine decarboxylase (ODC) 的表現而減少TPA 誘發之表皮層增厚與白血球浸潤的情形；於 DMBA/TPA 誘發之二階段皮膚致癌模式中證實，在 Anti-initiation/Anti-promotion的組別 HPSB 可透過減少皮膚腫瘤之促增生蛋白 proliferating cell nuclear antigen (PCNA)、Cyclin B1 及 cyclin-dependent kinase 1 (CDK1) 的表現而降低 DMBA/TPA 誘發之皮膚腫瘤發生率與腫瘤數目，此外 HPSB 亦可抑制皮膚腫瘤之 DNA 受損反應相關蛋白 ataxia-telangiectasia mutated kinase (ATM)、breast cancer 1 protein (BRCA1)、p53 及histone 2AX (H2AX) 的活化以發揮細胞保護之功效。本研究成果證實 HPSB 具有阻斷致癌物質之代謝與抗發炎之活性，因此進一步預防皮膚腫瘤致癌過程之起始與促進作用，建議 HPSB 未來可開發為抗發炎與癌症化學預防之天然試劑。

Global cancer incidence continues to increase with growing urbanization, the changes in food consumption and lifestyle habits. The concept of cancer chemoprevention is gaining interest and becomes an important research topic. Carcinogenesis is a multiple steps process involving genetic and molecular alterations, in which carcinogen activation and inflammation are considered the risk factor of cancer development. Therefore, the strategies for inactivating carcinogen and anti-inflammation are the critical chemoprventive targets for antitumorogenesis. 3'-hydroxypterostilbene (HPSB), a natural pterostilbene analogue isolated from whole plant of the herb Sphaerophysa salsula exhibits antiproliferative activity in several cancer cell lines; however, the inhibitory effects of HPSB on the initiation and promotion of skin carcinogenesis remains unclear. The present study was to investigate the the effects of HPSB on the modulation of phase I and phase II metabolizing enzymes in 7,12-dimethylbenz[a]anthracene (DMBA)-induced HaCaT cell model. we further investigated the anti-inflammation and anti-tumor effects of HPSB in 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated acute skin inflammation and DMBA/TPA-induced two-stage skin carcinogenesis model. Our results provided evidence that pretreatment of HPSB reduced DMBA-induced cytochrome P450 1A1 (CYP1A1) and cytochrome P450 (CYP1B1) gene expression in human keratinocytes; however, HPSB did not significantly affect the gene expression of phase II enzymes. In addition, topical treatment with HPSB inhibited TPA-induced epidermal hyperplasia and leukocyte infiltration through down-regulation of cyclooxygenase-2 (COX-2), matrix metalloprotein-9 (MMP-9) and ornithine decarboxylase (ODC) protein expression in mouse skin. Furthermore, HPSB suppressed DMBA/TPA-induced skin tumor incidence and multiplicity via inhibiting proliferating cell nuclear antigen (PCNA), Cyclin B1 and cyclin-dependent kinase 1 (CDK1) expression in two-stage skin carcinogenesis model. HPSB also exerted protective effects by suppressing activation of ataxia-telangiectasia mutated kinase (ATM), breast cancer 1 protein (BRCA1), p53 and histone 2AX (H2AX) in skin tumor in vivo. This is the first study to show that topical treatment with HPSB prevents mouse skin tumorigenesis involving cooperation of anti-tumor-initiating and -promoting dependent mechanisms. Overall, our study suggested that natural HPSB may serve as a novel chemopreventive agent for prevention of inflammation-associated tumorigenesis.