Validation of Biomarkers to Distinguish Aggressive from Indolent Prostate Cancer

描述（申请人提供）：晚期激素难治性转移性前列腺癌（PCa）是美国男性癌症死亡的第二大原因。血清PSA水平持续升高对PCa诊断的特异性低于30%，导致过度治疗和不必要的焦虑和痛苦。PSA筛查的广泛应用导致每年越来越多的低级别和小的前列腺癌的诊断。如果不及时治疗，其中一些PCas可能会发展并变得致命。然而，他们中的许多人可能会在病人的余生中保持惰性。目前还没有被批准的生物标志物可以区分通常致命的PCas和惰性的PCas。天然致癌物，如活性氧（ROS）在大多数PCa组织中大量过量产生。有强有力的证据表明，ROS在雄激素依赖性PCa （ADPCa）向毒性更强的去势抵抗性PCa （CRPCa）的发展过程中起着关键作用。一些出版物已经证明，其中一种ROS （H2O2）在表达某些生长和转录因子中起着核心作用，这些因子在缺乏雄激素的情况下维持雄激素依赖性PCa细胞的增殖。直到最近，雄激素诱导ROS产生的机制仍然很大程度上是未知的。在过去的5年中，我们已经确定了亚精胺/精胺乙酰转移酶（SSAT）酶活性的增加是ADPCa细胞中细胞ROS产生的主要原因。SSAT是将前列腺中大量产生的亚精胺和精胺转化为其相应的乙酰基衍生物的第一个调控酶。在富含多胺的PCa细胞中，乙酰精胺（ac-spd）和乙酰精胺（ac-spm）的氧化是雄激素诱导的ROS产生的主要因素。在前列腺活检或手术切除的前列腺组织中可以观察到SSAT的诱导。使用质谱法也可以从精液、血液和尿液中的代谢产物ac-spd和ac-spm中观察到所有患者的前列腺SSAT活性。在这里，我们提出验证我们的假设，即前列腺组织中SSAT表达增加以及精液、血液或尿液中SSAT代谢物ac-spd和/或ac-spd的升高可能是鉴别预后不良患者的可靠指标。我们的具体目标是：1)量化SSAT基因和蛋白在几个切除的前列腺组织微阵列（TMA）中的表达，包括正常前列腺、良性前列腺增生（BPH）、前列腺上皮内瘤变（PIN）、局部低级别前列腺癌、高级别前列腺癌和转移性前列腺癌，以及从马什菲尔德诊所获得的患者活检和前列腺切除术样本。2)定量分析前列腺癌患者和正常志愿者精液、血液和尿液中乙酰精胺和乙酰精胺的含量。3)将目标#1和#2中收集的数据与患者结果相关联，以验证PCa患者精液、血液或尿液样本中SSAT表达和ac-spd和/或ac-spm水平。这些生物标志物的阈值应该有助于识别进展风险高的患者。

DESCRIPTION (provided by applicant): Advanced hormone refractory metastatic prostate cancer (PCa) is the second leading cause of cancer deaths among US men. Persistent increase in serum PSA level has less than 30% specificity for PCa diagnosis leading to overtreatment and unnecessary anxieties and anguish. A widespread application of PSA screening is leading to the diagnosis of an increasing number of low grade and small PCas each year. Left untreated, some of these PCas may progress and become lethal. Many of them, however, may remain indolent for the rest of the patients' life. There is no approved biomarker that can distinguish often lethal PCas from the indolent ones. Natural carcinogens such as reactive oxygen species (ROS) are produced in large excess in a majority of PCa tissues. There is strong evidence that ROS play a key role in the progression of androgen- dependent PCa (ADPCa) to more virulent castrate-resistant PCa (CRPCa). Several publications have demonstrated that one of the ROS (H2O2) plays a central role in expressing certain growth and transcription factors that sustain androgen-dependent PCa cell proliferation in the absence of androgen. Until recently, a mechanism of androgen-induced ROS production remained largely unknown. In the last 5 years, we have established that an increase in the enzymatic activity of spermidine/spermine acetyl transferase (SSAT) is primarily responsible for the cellular ROS production in ADPCa cells. SSAT is the first and a regulatory enzyme in the pathway that converts spermidine and spermine that are produced in large amount in the prostate to their corresponding acetyl derivatives. Oxidation of acetyl-spermidine (ac-spd) and acetyl-spermine (ac-spm) is a major contributor of the androgen-induced ROS production in polyamine-rich PCa cells. Induction of SSAT can be observed in prostate biopsies or in the surgically resected prostate tissues from PCa patients. Prostate SSAT activity may also be observed in all patients from its metabolic products ac-spd and ac-spm in the seminal fluid, blood and urine using mass spectrometry. Here, we propose to validate our hypothesis that an increased SSAT expression in prostate tissues and an elevation of SSAT metabolites ac-spd and/or ac-spd in the seminal fluid, blood or urine could be a reliable indicator to identify patients with poor prognosis. Our Specific Aims are: 1) To quantitate SSAT gene and protein expression in several resected prostate tissue microarrays (TMA) consisting of normal prostate, benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN), localized low grade PCa, high grade PCa and metastatic PCa available at our Institution along with patient biopsy and prostatectomy samples obtained from the Marshfield Clinic, Marshfield, WI. 2) To quantitate acetyl-spermine and acetyl-spermidine levels in collected seminal fluids, blood and urine samples from PCa patients and normal volunteers. 3) To correlate the data collected in Aims #1 and #2 with patient outcome to validate the SSAT expression and the ac-spd and/or the ac-spm level in the semen, blood or urine samples of PCa patients. The threshold values of these biomarkers should help identify patients with high risk of progression.