Regulation of prostate cancer cell survival by 5-lipoxygenase:Role of PKC-epsilon

描述(申请人提供)：通过5-脂氧合酶调节前列腺癌细胞存活：PKC-epsilon的作用最新的实验数据表明，通过阻断关键生存机制(S)诱导前列腺癌(PCA)细胞凋亡可以是预防和治疗前列腺癌(PCa)的一个有吸引力的方法，因为临床上前列腺癌通常被描述为生长缓慢，抗有丝分裂治疗效果不大。然而，PCa细胞的存活机制尚未完全清楚，这在很大程度上导致了与这种疾病的斗争的失败。多项研究的新证据表明，前列腺癌细胞从花生四烯酸(一种西方饮食中丰富的omega-6脂肪酸)结构性地产生5-脂氧合酶(5-Lox)的代谢产物，而特定的抑制剂抑制5-Lox的产生阻止了5-Lox代谢产物的产生，并诱导雄激素敏感的以及雄激素非依赖性的PCA细胞快速凋亡，而非癌症细胞除外。5-Lox代谢产物5(S)-HETE和5-oxoETE能有效地阻止细胞凋亡，提示这些代谢产物在PCa细胞的生存中起重要作用。使用针对5-Lox的siRNAs也证明了5-Lox在PCa细胞存活中的关键作用。然而，5-Lox代谢物调节PCa细胞存活的信号机制(S)尚不清楚。有趣的是，5-Lox在正常前列腺组织中不表达，但在前列腺癌和前列腺癌细胞中高表达，这与5-Lox在前列腺癌细胞生存中的关键作用一起表明，5-Lox可能在前列腺癌的发生发展中发挥重要作用。最近的一项初步实验表明，5-Lox活性的特异性抑制剂MK591可以显著阻止前列腺癌裸鼠移植瘤的生长，而对动物健康没有任何毒性，这表明抑制5-Lox可能是一种有吸引力的方法，可以在没有普遍毒性的情况下对前列腺癌细胞发动特异性攻击。因此，应广泛开展体内靶向5-Lox的研究，以实现针对PCa的快速翻译开发。本研究的目标是阐明5-Lox调控PCa细胞存活的信号机制，并测试靶向5-Lox的体内效应，重点关注PCa的预防和治疗方面。这些目标将通过实现三个具体目标来实现。具体目的1将确定5-Lox活性如何调节涉及PKC-epsilon(PKC5)介导的信号转导的PCa细胞存活，因为抑制5-Lox抑制PKC5，而5-Lox抑制诱导的细胞凋亡是由PKC5的激活剂阻止的。特定目的2将确定抑制5-Lox是否通过诱导前列腺癌细胞凋亡来抑制裸鼠移植瘤的生长。具体目标3将通过产生5-Lox基因敲除转基因小鼠(TRAMP)来确定5-Lox在前列腺癌的发生和发展中的作用。完成本研究的目标将有助于我们了解PCa细胞存活的新机制，确定5-Lox是否在PCa的发生和发展中发挥作用，并测试靶向5-Lox是否可以成为预防和治疗PCa的一种新的基于机制的策略。

DESCRIPTION (provided by applicant): Regulation of prostate cancer cell survival by 5-lipoxygenase: Role of PKC-epsilon Fresh experimental data suggest that induction of apoptosis in prostate cancer (PCa) cells by blocking critical survival mechanism(s) can be an attractive approach to prevent and treat PCa because clinically PCa is often characterized as slow growing where anti-mitogenic therapies are not much effective. However, the repertoire of survival mechanisms in PCa cells is not completely understood which largely contributes to the loss of battle against this disease. Emerging evidence from various studies has shown that PCa cells constitutively generate metabolites of 5-lipoxygenase (5-Lox) from arachidonic acid (an omega-6 fatty acid plentiful in Western diets), and inhibition of 5-Lox by specific inhibitors blocks production of 5-Lox metabolites and induces rapid apoptosis both in androgen-sensitive as well as androgen-independent PCa cells sparing non-cancer cells. Apoptosis is effectively prevented by the 5-Lox metabolites, 5(S)-HETE and 5-oxoETE, suggesting that these metabolites play an essential role in the survival of PCa cells. A critical role of 5-Lox in the survival of PCa cells has also been documented using siRNAs against 5-Lox. However, signaling mechanism(s) through which 5-Lox metabolites regulate PCa cell survival are not yet understood. Interestingly, 5-Lox is not expressed in normal prostate glands but is highly expressed in prostate tumors and in PCa cells, which together with a critical role of 5-Lox in the survival of PCa cells, suggests that 5-Lox may play an important role in the development of PCa. A recent pilot experiment showed that MK591, a specific inhibitor of 5-Lox activity, remarkably blocks prostate tumor growth in nude mice xenografts without any toxicity to animal health, suggesting that inhibition of 5-Lox could be an attractive approach for mounting specific attack on PCa cells without general toxicity. Thus, in vivo targeting of 5-Lox should be extensively carried out for a rapid translational development against PCa. The goals of this research project are to delineate the signaling mechanisms underlying regulation of PCa cell survival by 5-Lox, and to test the in vivo effects of targeting 5-Lox focusing on both the preventive and therapeutic aspects of PCa. These goals will be achieved by accomplishing the objectives of three specific aims. Specific Aim 1 will determine how 5-Lox activity regulates PCa cell survival involving PKC-epsilon (PKC5)-mediated signaling, because inhibition of 5-Lox inhibits PKC5 which is prevented by 5-Lox metabolites, and 5-Lox inhibition-induced apoptosis is prevented by activators of PKC5. Specific Aim 2 will determine whether inhibition of 5-Lox inhibits growth of prostate tumors in nude mice xenografts via induction of apoptosis in PCa cells. Specific Aim 3 will determine the role of 5-Lox in the development and progression of PCa by generating 5-Lox knockout transgenic (TRAMP) mice. Accomplishing the goals in this research project will help us to understand a novel mechanism of PCa cell survival, to determine whether 5-Lox plays a role in the development and progression of PCa, and to test whether targeting 5-Lox could be a novel mechanism-based strategy for prevention as well as treatment of PCa.