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

描述（由申请人提供）：5-脂氧合酶对前列腺癌细胞存活的调节：PKC-β的作用新的实验数据表明，通过阻断关键存活机制诱导前列腺癌（PCa）细胞凋亡可能是预防和治疗PCa的一种有吸引力的方法，因为临床上PCa通常被表征为生长缓慢，其中抗有丝分裂疗法不是很有效。然而，PCa细胞中的存活机制尚未完全了解，这在很大程度上导致了对抗这种疾病的失败。来自各种研究的新证据表明，PCa细胞从花生四烯酸（西方饮食中丰富的ω-6脂肪酸）组成性地产生5-脂氧合酶（5-Lox）的代谢物，并且通过特异性抑制剂抑制5-Lox阻断5-Lox代谢物的产生并诱导雄激素敏感性以及雄激素非依赖性PCa细胞（保留非癌细胞）的快速凋亡。5-Lox代谢产物5（S）-HETE和5-oxoETE可有效防止细胞凋亡，表明这些代谢产物在PCa细胞的存活中起重要作用。5-Lox在PCa细胞存活中的关键作用也已使用针对5-Lox的siRNA记录。然而，5-Lox代谢物调节PCa细胞存活的信号传导机制尚不清楚。有趣的是，5-Lox在正常前列腺中不表达，但在前列腺肿瘤和PCa细胞中高度表达，这与5-Lox在PCa细胞存活中的关键作用一起表明5-Lox可能在PCa的发展中起重要作用。最近的一项初步实验表明，MK 591（一种5-Lox活性的特异性抑制剂）可以显着抑制裸小鼠异种移植物中前列腺肿瘤的生长，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，可以对前列腺癌细胞进行特异性攻击，而不会产生全身毒性。因此，5-Lox的体内靶向应该广泛地进行，以针对PCa进行快速翻译开发。本研究项目的目标是描述5-Lox调节PCa细胞存活的信号传导机制，并测试靶向5-Lox的体内作用，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。具体目标1将确定5-Lox活性如何调节PCa细胞存活，涉及PKC-β（PKC 5）介导的信号传导，因为5-Lox的抑制抑制PKC 5，这被5-Lox代谢物阻止，并且5-Lox抑制诱导的细胞凋亡被PKC 5的激活剂阻止。具体目标2将确定5-Lox的抑制是否通过诱导PCa细胞的凋亡来抑制裸鼠异种移植物中前列腺肿瘤的生长。具体目标3将通过产生5-Lox敲除转基因（TRAMP）小鼠来确定5-Lox在PCa的发展和进展中的作用。实现本研究项目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的发展和进展中发挥作用，并测试靶向5-Lox是否可以成为预防和治疗PCa的新机制。

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.