Prostate-Directed Antioxidant to Prevent Prostate Cancer

描述(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。由于目前常用的化疗药物对前列腺癌的治疗效果有限，迫切需要开发新的药物来预防前列腺癌的发生和发展。前列腺癌组织中过氧化氢、超氧化物歧化、羟基自由基和一氧化氮等活性氧物种(ROS)水平相对高于正常组织。在过去的5年里，有直接证据表明，ROS与包括前列腺癌在内的各种组织中肿瘤发展的增加有关。已有研究表明，雄激素可调节雄激素依赖型前列腺癌细胞中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剩的多胺。多胺通过亚精胺/精胺乙酰转移酶(SSAT)的乙酰化，然后被乙酰多胺氧化酶(APAO)氧化产生ROS来分解代谢。最近在我们实验室进行的DNA芯片分析和qRT-PCR研究表明，雄激素诱导雄激素依赖型前列腺癌细胞中SSAT基因的过度表达。我们的初步数据显示，用APAO抑制剂MDL对雄激素依赖的LNCaP细胞进行预处理后，完全消除了雄激素诱导的氧化应激。在这里，我们建议开发MDL，它可以特异性地降低前列腺癌细胞中的氧化应激，作为一种可以防止前列腺癌发生、生长和/或进展的药物。我们的具体目标是：1)通过二氯荧光素(DCF)氧化实验，确定MDL预处理对雄激素依赖的前列腺癌LapC4和LNCaP细胞株的氧化应激的阻断作用。2)采用氢乙啶(HET)氧化法检测MDL对LNCaP裸鼠移植瘤的氧化应激抑制作用。3)检测MDL对LNCaP和LapC4裸鼠移植瘤生长的抑制作用。4)检测MDL对转基因小鼠前列腺癌(TRAMP)模型自发性前列腺癌的抑制作用。这些目标的成功实现不仅将使MDL成为一种潜在的前列腺癌化学预防药物，并可进一步开发用于临床，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.