Prostate Cancer Prevention by Diallyl Trisulfide

描述(由申请人提供)：预防前列腺癌的新策略是非常可取的，因为这种恶性肿瘤在美国男性中死亡率很高。在这项资助的资助期间，我们发现大蒜成分二烯丙基三硫化物(DATS)通过诱导细胞凋亡来选择性地抑制培养的人前列腺癌细胞的生长，而与其雄激素反应或P53状态无关。我们还首次证明，口服DATS不仅可以延缓裸鼠体内PC-3人前列腺癌移植瘤的生长，而且在转基因小鼠模型(TRAMP)中也可以有效地防止前列腺癌的发展，而且没有任何明显的毒性迹象。此外，我们还发现，前列腺癌细胞中DATS介导的促凋亡信号转导与铁蛋白(轻链)降解产生的活性氧物种(ROS)的产生以及不稳定(可螯合)铁库的增加密切相关。我们最近未发表的初步研究表明，用诱导凋亡浓度的DATS处理人前列腺癌细胞会导致Survivin的上调，Survivin是一种经常在人类癌症中过度表达的抗凋亡蛋白。目前的更新应用建立在这些令人兴奋和新颖的观察结果的基础上，在很大程度上将重点从面向分子的细胞研究转移到对具有巨大翻译价值的机制发现的体内验证。假设：统一更新应用的具体目的的中心假设是，良好的药代动力学属性使DATS能够通过不稳定的铁-ROS介导的细胞凋亡来防止前列腺癌的发展，这种细胞凋亡可以通过药物抑制Survivin来增强。具体目的：更新应用的具体目的是：(1)利用非转基因雄性小鼠确定DATS的药代动力学参数和口服生物利用度；(2)使用细胞(PC-3、LNCaP和PREC)和体内模型(TRAMP小鼠)确定不稳定的铁介导的ROS产生在DATS促凋亡和化学预防反应中的作用；(3)通过培养细胞(PC-3、LNCaP和PREC)和来自TRAMP小鼠的前列腺/肿瘤组织(来自特定的目标2)，深入了解DATS诱导ROS产生下游的分子电路；(4)用细胞模型(PC-3、LNCaP)和体内模型(TRAMP小鼠)确定Survivin基因敲除对DATS诱导细胞凋亡和化学预防反应的影响。拟议研究的翻译影响：尽管在该项目资助期间进行的研究为DATS治疗前列腺癌的有效性提供了令人信服的临床前证据，但将这些发现有效地转化为临床环境，关键取决于细胞观察的活体验证。如果临床试验没有充分了解影响DATS生物效应的因素，就会有失败的风险。例如，体内验证不稳定的铁-ROS在DATS的促凋亡和化学预防反应中的作用(特定目标2)对于优化基于DATS的化学预防方案至关重要，以消除DATS与其他抗氧化剂或干扰铁稳态的药物之间潜在的不良药物相互作用。同样，特定目标4的内在价值在于潜在的设计包含DATS和Survivin抑制剂的组合方案，以有效地化学预防人类前列腺癌。

DESCRIPTION (provided by applicant): Novel strategies for prevention of prostate cancer are highly desirable because of high mortality associated with this malignancy in American men. During the funded period of this grant, we showed that garlic constituent diallyl trisulfide (DATS) selectively inhibits growth of cultured human prostate cancer cells by causing apoptosis regardless of their androgen responsiveness or the p53 status. We also demonstrated, for the first time, that oral DATS administration not only retards growth of PC-3 human prostate cancer xenografts in athymic mice but also offers significant protection against prostate cancer development in a transgenic mouse model (TRAMP) without any signs of overt toxicity. Furthermore, we discovered that the DATS-mediated proapoptotic signal transduction in prostate cancer cells is intimately linked to the production of reactive oxygen species (ROS) due to ferritin (light chain) degradation and an increase in labile (chelatable) iron pool. Our more recent preliminary unpublished studies have revealed that treatment of human prostate cancer cells with apoptosis-inducing concentrations of DATS results in up-regulation of survivin, an anti-apoptotic protein frequently overexpressed in human cancers. The present renewal application, building upon these exciting and novel observations, largely shifts emphasis from molecularly-oriented cellular studies to in vivo validation of the mechanistic findings with tremendous translational value. Hypothesis: Central hypothesis unifying the specific aims of the renewal application is that favorable pharmacokinetic attributes empower DATS to prevent prostate cancer development via labile iron-ROS- mediated apoptosis, which is amenable to augmentation by pharmacologic suppression of survivin. Specific Aims: The specific aims of the renewal application are to: (1) determine the pharmacokinetic parameters and oral bioavailability of DATS using non-transgenic male mice; (2) determine the contribution of labile iron-mediated ROS production in proapoptotic and chemopreventive response to DATS using cellular (PC-3, LNCaP, and PrEC) and in vivo models (TRAMP mice); (3) gain insight into the molecular circuitry of DATS-induced apoptosis downstream of ROS production using cultured cells (PC-3, LNCaP, and PrEC) and prostate/tumor tissues from TRAMP mice (from specific aim 2); and (4) determine the effect of survivin knockdown on proapoptotic and chemopreventive response to DATS using cellular (PC-3, LNCaP) and in vivo models (TRAMP mice). Translational Impact of the Proposed Research: Even though the studies conducted during the funded period of this project provide compelling preclinical evidence for efficacy of DATS against prostate cancer, efficient translation of these findings into a clinical setting is critically dependent on in vivo validation of the cellular observations. Clinical trials without a full appreciation of the factors influencing biological effects of DATS inherit risk of failure. For example, in vivo validation of the contribution of labile iron-ROS in proapoptotic and chemopreventive response to DATS (Specific Aim 2) is essential for optimization of DATS-based chemopreventive regimens to eliminate potential adverse drug-drug interactions between DATS and other anti- oxidants or agents interfering with iron homeostasis. Similarly, intrinsic value of Specific Aim 4 resides in potential design of combination regimens involving DATS and inhibitors of survivin for efficient chemoprevention of human prostate cancer.