Prostate Cancer Prevention by Diallyl Trisulfide

描述（申请人提供）：由于美国男性前列腺癌的高死亡率，预防前列腺癌的新策略是非常可取的。在此资助期间，我们发现大蒜成分二烯丙基三硫醚（DATS）选择性地抑制培养的人前列腺癌细胞的生长，导致细胞凋亡，而不管其雄激素反应性或p53状态如何。我们还首次证明，口服DATS不仅可以延缓PC-3人类前列腺癌异种移植物在胸腺小鼠中的生长，而且在转基因小鼠模型（TRAMP）中对前列腺癌的发展也有显著的保护作用，而没有任何明显的毒性迹象。此外，我们发现dats介导的前列腺癌细胞促凋亡信号转导与铁蛋白（轻链）降解和不稳定（可螯合）铁池增加导致活性氧（ROS）的产生密切相关。我们最近的初步未发表的研究表明，用诱导凋亡浓度的DATS治疗人类前列腺癌细胞会导致survivin的上调，survivin是一种在人类癌症中经常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基础上，很大程度上将重点从分子导向的细胞研究转移到具有巨大翻译价值的机制发现的体内验证。假设：统一更新申请的具体目标的中心假设是，有利的药代动力学特性使DATS能够通过不稳定的铁ros介导的细胞凋亡来预防前列腺癌的发展，这可以通过药物抑制survivin来增强。具体目的：更新申请的具体目的是：(1)使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)通过细胞模型（PC-3、LNCaP和PrEC）和体内模型（TRAMP小鼠），确定不稳定铁介导的ROS产生对DATS的促凋亡和化学预防反应的贡献；(3)利用培养的细胞（PC-3、LNCaP和PrEC）和来自TRAMP小鼠的前列腺/肿瘤组织，深入了解dats诱导的ROS产生下游细胞凋亡的分子通路（来自特异性目的2）；(4)通过细胞模型（PC-3, LNCaP）和体内模型（TRAMP小鼠）确定survivin敲低对DATS促凋亡和化学预防反应的影响。拟议研究的转化影响：尽管在本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体内验证。没有充分了解影响DATS生物学效应的因素的临床试验有失败的风险。例如，在体内验证不稳定的铁- ros对DATS的促凋亡和化学预防反应的贡献（Specific Aim 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-药物相互作用。类似地，Specific Aim 4的内在价值在于设计包含DATS和survivin抑制剂的联合方案，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 Our more recent preliminary unpublished studies have revealed that treatment of human prostate cancer cells with apoptosis-inducing concentrations of DATS results in up-regulation of survivin, an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. PUBLIC HEALTH RELEVANCE: Prostate cancer is one of the most commonly diagnosed visceral malignancies and a leading cause of cancer- related deaths among men in the United States. Therefore, novel strategies to hinder inception and/or progression of prostate cancer are highly desirable to reduce the disease-related cost, morbidity and mortality associated with this neoplasm. The ultimate goal of this project is to develop a safe and inexpensive but effective strategy for chemoprevention of human prostate cancer using garlic constituent diallyl trisulfide (DATS). Even though the studies conducted thus far 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 findings. In summary, the immediate and future intrinsic value of the studies proposed in this renewal application resides in optimization of DATS-based regimens for chemoprevention of prostate cancer.