Pure Flavonolignans from S. marianum in Prostate Cancer

描述(申请人提供)：水飞蓟提取物(水飞蓟)自古以来就被用于治疗多种疾病，最近被研究用于治疗病毒性和化学性肝病、血脂异常和癌症。水飞蓟提取物，通常被称为水飞蓟素或水飞蓟宾，含有大量的黄酮类和黄酮木素化合物，这些化合物在体外和体内都有生物学效应。然而，将特定的生物学作用归因于特定的水飞蓟成分的研究还很少，这既是因为自然产生的化合物的复杂立体化学，也是因为要分离足够数量的这些化合物存在相当大的挑战。RTI天然产品实验室最近成功地从市场上可获得的水飞蓟素中分离出了水飞蓟黄酮木脂素的个体立体异构体和区域异构体。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，现在首次可用于表征它们的单独生物活性，特别是确定它们对先前在人类前列腺癌临床前模型中观察到的水飞蓟宾和水飞蓟素的实质性活性的相对贡献。为此，该小组与科罗拉多大学的拉杰什·阿加瓦尔博士的实验室建立了合作关系。阿加瓦尔博士是该领域的国际领先者，致力于展示水飞蓟提取物在皮肤癌和前列腺癌模型中的功效，以及这些反应背后的生化机制。这个合作研究小组建议测试这一假设，即单个黄酮木脂素异构体具有不同的生物活性，这解释了以前观察到的天然牛奶蓟提取物混合物水飞蓟宾和水飞蓟素的集体抗癌作用。具体地说，该小组建议1)进行和优化4种乳蓟黄酮木脂素的半合成，以便分离出所有体外和体内研究所需的更大数量的每一种黄酮木脂素；2)研究每一种黄酮木脂素相对于水飞蓟宾和水飞蓟素在免疫受损小鼠的DU145激素耐药、转移性前列腺癌中的抗肿瘤活性；3)确定每一种黄酮素对体外有丝分裂细胞信号转导和细胞周期进程终点的特定生物学作用，4)确定各黄酮木脂素对人前列腺癌(CXCR4、EZH2和AMACR)中IGFBP-3基因启动子和拓扑异构酶II基因启动子中的遗传元件以及新发现的致病/预后因子(CXCR4、EZH2和AMACR)的特定生物学作用。综上所述，这些研究有望促进我们对高度无毒的前列腺癌预防和治疗干预措施的生化理解，从而有可能确定比自然发生的化合物更有效和/或生物可用的组合。

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.