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-epsilon的作用最新实验数据表明，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前列腺癌的一种有吸引力的方法，因为临床上前列腺癌通常以生长缓慢为特征，抗有丝分裂治疗效果不明显。然而，前列腺癌细胞的生存机制还不完全清楚，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，前列腺癌细胞组成性地从花生四烯酸（西方饮食中大量存在的一种ω -6脂肪酸）中产生5-脂氧合酶（5-Lox）代谢物，特定抑制剂抑制5-Lox可阻断5-Lox代谢物的产生，并诱导雄激素敏感和雄激素非依赖型前列腺癌细胞快速凋亡，而非癌细胞。5- lox代谢物、5(S)-HETE和5- oxoete可有效阻止细胞凋亡，提示这些代谢物在PCa细胞存活中发挥重要作用。5-Lox在PCa细胞存活中的关键作用也被证明使用sirna来对抗5-Lox。然而，5-Lox代谢物调节PCa细胞存活的信号机制尚不清楚。有趣的是，5-Lox在正常前列腺中不表达，但在前列腺肿瘤和前列腺癌细胞中高表达，加之5-Lox在前列腺癌细胞存活中的关键作用，提示5-Lox可能在前列腺癌的发生发展中发挥重要作用。最近的一项试点实验表明，MK591，一种特异性的5-Lox活性抑制剂，可以显著阻止裸鼠异种移植前列腺肿瘤的生长，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，可以对PCa细胞进行特异性攻击，而不会产生一般毒性。因此，5-Lox的体内靶向应该广泛开展，以快速开发针对PCa的翻译。本研究项目的目标是描述5-Lox调控PCa细胞存活的信号机制，并测试靶向5-Lox在PCa预防和治疗方面的体内效果。这些目标将通过实现三个具体目标来实现。特异性Aim 1将确定5-Lox活性如何通过PKC-epsilon （PKC5）介导的信号传导调节PCa细胞存活，因为5-Lox的抑制会抑制PKC5，而PKC5的代谢物可以阻止PKC5的抑制，PKC5的激活剂可以阻止5-Lox抑制诱导的凋亡。特异性目的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异种移植前列腺肿瘤的生长。特异性Aim 3将通过产生5-Lox基因敲除转基因（TRAMP）小鼠来确定5-Lox在PCa发生和进展中的作用。完成本研究项目的目标将有助于我们了解前列腺癌细胞存活的新机制，确定5-Lox是否在前列腺癌的发生和进展中发挥作用，并测试靶向5-Lox是否可能成为一种基于机制的预防和治疗前列腺癌的新策略。

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.