Pure Flavonolignans from S. marianum in Prostate Cancer

描述（由申请人提供）：水飞蓟提取物（Silybum marianum）自古以来就被用于许多疾病，最近被研究用于病毒性和化学性肝脏疾病、血脂异常和癌症的治疗。水飞蓟提取物，通常被称为水飞蓟素或水飞蓟宾，含有大量的类黄酮和黄酮木脂素化合物，这些化合物负责它们在体外和体内的生物效应。然而，将特定生物作用归因于特定水飞蓟成分的研究数量很少，因为天然存在的化合物具有复杂的立体化学性质，而且要分离出足够数量的这些化合物存在相当大的挑战。RTI天然产物实验室最近成功地从市售水飞蓟素中鉴定和分离出水飞蓟黄酮木脂素的个体立体和区域异构体。这些化合物被称为水飞蓟宾A、水飞蓟宾B、异水飞蓟宾A和异水飞蓟宾B，现在首次可以用于表征它们的个体生物活性，特别是确定它们对水飞蓟宾和水飞蓟素在人类前列腺癌临床前模型中观察到的实质性活性的相对贡献。为此，该小组与科罗拉多大学（University of Colorado）的拉杰什·阿加瓦尔（Rajesh Agarwal）博士的实验室建立了合作关系。阿加瓦尔博士是证明水飞蓟提取物在皮肤和前列腺癌模型中的功效以及这些反应背后的生化机制方面的国际领导者。这个合作研究小组提出测试假设，即单个黄酮木质素异构体具有不同的生物活性，这解释了以前在天然存在的水飞蓟提取物混合物水飞蓟宾和水飞蓟素中观察到的集体抗癌作用。具体而言，本课课组提出：1)进行并优化4种水飞蓟黄酮木脂素的半合成，以便在体外和体内研究中大量分离每种黄酮木脂素；2)研究每种黄酮木脂素相对于水飞蓟宾和水飞蓟素在DU145激素难愈、转移性人前列腺癌免疫功能低下小鼠中的抗肿瘤活性。3)确定每种黄酮木脂素对有丝分裂细胞信号通路和细胞周期进程的体外终点的特异性生物学作用；4)确定每种黄酮木脂素对a) IGFBP-3和拓扑异构酶II基因启动子中的遗传元件和b)新描述的人类前列腺癌的致病/预后因子（CXCR4， EZH2和AMACR）的特异性生物学作用。综上所述，这些研究有望促进我们对高度无毒前列腺癌预防和治疗干预的生化理解，并有可能确定比自然发生的更有效和/或生物利用的化合物组合。

DESCRIPTION (provided by applicant): Extracts of milk thistle (Silybum marianum) have been used since antiquity for a number of disorders and have most recently been investigated for utility in hepatic disorders of viral and chemical origin, dyslipidemia, and cancer. Milk thistle extracts, often referred to interchangably as silymarin or silibinin, contain a number of flavonoid and flavonolignan compounds that are responsible for their in vitro and in vivo biological effects. However, studies to ascribe particular biological actions to specific milk thistle components have been few in number due both to the complex stereochemistry of the naturally-occurring compounds and the considerable challenges in isolating these compounds in sufficient quantities. The RTI Natural Products Laboratory has recently succeeded in identifying and isolating from commercially-available silymarin the individual stereoand regio-isomers of milk thistle flavonolignans. These compounds, referred to as silybin A, silybin B, isosilybin A, and isosilybin B, are now available for the first time for characterization of their individual biological activities and, specifically, the determination of their relative contribution to the substantial activity of silibinin and silymarin observed previously in pre-clinical models of human prostate cancer. To do so, the group has established a collaboration with the laboratory of Dr. Rajesh Agarwal at the University of Colorado, the international leader in the demonstrating the efficacy of milk thistle extracts in skin and prostate cancer models and the biochemical mechanisms underlying these responses. This collaborative research group proposes to test the HYPOTHESIS that individual flavonolignan isomers possess distinct biological activities that account for the collective anti-cancer action previously observed for the naturally occurring milk thistle extract mixtures, silibinin and silymarin. Specifically, the group proposes 1) to conduct and optimize the semi-synthesis of the 4 milk thistle flavonolignans in order to isolate each in the larger quantities required for all in vitro and in vivo studies, 2) to investigate the antitumor activity of each individual flavonolignan relative to silibinin and silymarin in DU145 hormone-refractory, metastatic human prostate cancer in immunocompromised mice, 3) to determine the specific biological actions of each flavonolignan on in vitro endpoints of mitogenic cellular signaling and cell cycle progression, and 4) to determine the specific biological actions of each flavonolignan on a) genetic elements in the IGFBP-3 and topoisomerase II gene promoters and b) newly described causative/prognostic factors in human prostate cancer (CXCR4, EZH2, and AMACR). Taken together, these studies are anticipated to advance our biochemical understanding of a highly non-toxic prostate cancer prevention and treatment intervention with the possibility of identifying more efficacious and/or bioavailable combinations of compounds than those occurring naturally.