Prostate-Directed Antioxidant to Prevent Prostate Cancer

描述（由申请人提供）：晚期激素难治性转移性前列腺癌是美国男性癌症死亡的第二大原因。由于常用的化疗药物在治疗前列腺癌方面的效果有限，因此迫切需要开发新的药物来预防前列腺癌的发生和发展。前列腺肿瘤中的活性氧（ROS）如过氧化氢、超氧化物、羟基自由基和一氧化氮水平相对高于正常组织。在过去的5年中，有直接证据表明ROS与包括前列腺在内的各种组织中肿瘤发展的增加有关。也有研究表明雄激素可以调节雄激素依赖性前列腺癌细胞中ROS的产生。虽然ROS产生的确切机制尚不清楚，但一种可能性可能是通过诱导多胺分解代谢途径，因为前列腺细胞产生大量过量的多胺。多胺通过亚精胺/精胺乙酰转移酶（SSAT）的乙酰化分解代谢，然后被乙酰多胺氧化酶（APAO）氧化产生ROS。最近在我们实验室进行的DNA微阵列分析和qRT-PCR研究表明，雄激素诱导SSAT基因在雄激素依赖性前列腺癌细胞中过表达。我们的初步数据显示，用APAO抑制剂MDL预处理雄激素依赖性LNCaP细胞完全消除雄激素诱导的氧化应激。在这里，我们建议开发特异性降低前列腺细胞氧化应激的MDL，作为预防前列腺癌发生、生长和/或进展的药物。我们的具体目的是：1)通过二氯荧光（DCF）氧化实验，建立MDL预处理对雄激素依赖性前列腺癌细胞系LapC4和LNCaP雄激素诱导的氧化应激的阻断能力。2)采用氢乙啶（HEt）氧化法测定MDL对LNCaP肿瘤异种移植裸鼠模型氧化应激的降低能力。3)测定MDL对LNCaP和LapC4肿瘤移植裸鼠生长的抑制作用。4)在小鼠前列腺腺癌（TRAMP）转基因模型中，检测MDL对自发性前列腺肿瘤形成的抑制作用。这些目标的成功完成不仅将确立MDL作为一种潜在的前列腺癌化学预防药物，可以进一步开发用于临床应用，而且还将证明多胺分解代谢途径作为前列腺癌化学预防的有效靶点的重要性。

DESCRIPTION (provided by applicant): Advanced hormone refractory metastatic prostate cancer is the second leading cause of cancer deaths among US men. As commonly used chemotherapeutic agents have limited success in the treatment of prostate cancer, development of novel agents to prevent its occurrence and progression is urgently needed. Reactive oxygen species (ROS) such as hydrogen peroxide, superoxide, hydroxyl free radical and nitric oxide levels are relatively higher in prostate tumors than in normal tissues. In the past 5 years, direct evidence linking ROS with an increase in tumor development in various tissues including that in the prostate has been reported. It has also been demonstrated that androgen modulates ROS production in androgen dependent prostate cancer cells. Although the exact mechanism of ROS production remains unknown, one possibility may be through the induction of the polyamine catabolic pathway as prostate cells produce a large excess of polyamines. Polyamines catabolize through acetylation by spermidine/spermine acetyltransferase (SSAT) followed by oxidation by acetyl polyamine oxidase (APAO) that produces ROS. Recent DNA microarray analysis and qRT-PCR studies carried out in our laboratory have shown that androgen induces overexpression of the SSAT gene in androgen dependent prostate cancer cells. Our preliminary data showed that pretreatment of androgen dependent LNCaP cells with an APAO inhibitor MDL completely abrogates androgen induced oxidative stress. Here, we propose to develop MDL that specifically reduces oxidative stress in prostate cells as an agent that can prevent occurrence, growth and/or progression of prostate cancer. Our specific aims are: 1) To establish the ability of MDL pretreatment to block androgen induced oxidative stress in androgen dependent prostate cancer cell lines LapC4 and LNCaP by dichlorofluorescene (DCF) oxidation assay. 2) To determine the ability of MDL to reduce oxidative stress in LNCaP tumor xenografts in nude mouse model using Hydroethidine (HEt) oxidation method. 3) To determine the ability of MDL to prevent growth of LNCaP and LapC4 tumor xenografts in nude mouse. 4) To determine the ability of MDL to prevent spontaneous prostate tumor formation in transgenic adenocarcinoma in mouse prostate (TRAMP) model. A successful completion of these Aims will not only establish MDL as a potential prostate cancer chemopreventive agent that can be further developed for clinical use but should also demonstrate the importance of polyamine catabolic pathway as a valid target for prostate cancer chemoprevention.