Novel Dithiolethiones for Bladder Cancer Prevention

描述（由申请人提供）：本项目的重点是鉴定和开发用于预防膀胱癌的新型二硫代硫醚。许多证据表明，致癌物解毒第二阶段酶在膀胱癌预防中起着重要作用。我们最近发现，5，6-二氢环戊二烯并[c]-1，2-二硫杂环戊烯-3（4 H）-环戊烯（CPDT）是啮齿动物膀胱中非常有效的2相酶诱导剂，并假设CPDT或更有效的类似物将是对抗膀胱癌的高效保护剂。该项目的目的1是进一步表征CPDT的2相酶诱导特性，检查CPDT的毒性和药代动力学行为，并测试CPDT类似物以鉴定更有效的2相酶诱导剂。这些研究将在大鼠中进行;将测量测试化合物对三种重要的2期酶（GST、NQO 1和UGT）的影响;将合成CPDT类似物;将测量CPDT的毒性和药代动力学的各种参数。目的2是确定哪些GST和UGT同种型由CPDT及其更有效的类似物（在目的1中鉴定）诱导，这种诱导是否是物种特异性的，以及CPDT是否在细胞中代谢为新的诱导物形式。将使用来自人类和啮齿动物的膀胱上皮细胞来检查GST和UGT的同种型的反应，所述GST和UGT的同种型显示出在膀胱癌预防中起重要作用。CPDT代谢将使用放射性标记的CPDT和LC/MS/MS进行研究。目的3是阐明负责诱导2相酶的CPDT及其类似物的分子机制。我们假设Nrf 2（转录因子）在介导这种诱导中起着重要作用。目的4是评估CPDT或一种更有前途的类似物对体外和体内膀胱细胞中膀胱致癌物的遗传毒性的保护作用，如通过DMA损伤和细胞/组织增殖测量的，并使用培养的膀胱上皮细胞和具有和不具有Nrf 2功能的小鼠研究Nrf 2信号通路在介导这种作用中的作用。目标4中开展的研究还将用于确定目标5中进一步实验所用二硫杂环戊烯硫酮的适当剂量水平。目的5是使用野生型和Nrf 2基因敲除小鼠，确定目的4中检查的二硫代硫酮对体内化学致癌物诱导的膀胱肿瘤发生的抑制作用以及Nrf 2信号传导在介导这种作用中的作用。

DESCRIPTION (provided by applicant): This project is focused on identifying and developing novel dithiolethiones for the prevention of urinary bladder cancer. Many lines of evidence show that carcinogen-detoxifying Phase 2 enzymes play a major role in bladder cancer prevention. We have recently found that 5,6-dihydrocyclopenta[c]-1,2-dithiole-3(4H)-thione (CPDT) is an extremely efficacious inducer of Phase 2 enzymes in rodent bladders in vivo and hypothesize that CPDT or a more potent analog would be a highly effective protector against bladder cancer. Aim 1 of the project is to further characterize the Phase 2 enzyme-inducing property of CPDT, to examine the toxicity and pharmacokinetic behavior of CPDT, and to test CPDT analogs for identification of more potent inducers of Phase 2 enzymes. These studies will be performed in rats; the impact of the test compound on three important Phase 2 enzymes (GST, NQO1 and UGT) will be measured; CPDT analogs will be synthesized; various parameters of toxicity and pharmacokinetics of CPDT will be measured. Aim 2 is to determine which GST and UGT isoforms are induced by CPDT and its more potent analogs (identified in Aim 1), whether such induction is species specific, and if CPDT is metabolized in cells to a new inducer form. The response of the isoforms of GST and UGT which were shown to play important roles in bladder cancer prevention will be examined using bladder epithelial cells from humans and rodents. CPDT metabolism will be investigated using radiolabeled CPDT and LC/MS/MS. Aim 3 is to elucidate the molecular mechanism responsible for the induction of Phase 2 enzymes by CPDT and its analogs. We hypothesize that Nrf2 (a transcriptional factor) plays a major role in mediating such an induction. Aim 4 is to assess the protective effects of CPDT or a more promising analog against the genotoxicities of bladder carcinogens in bladder cells both in vitro and in vivo, as measured by DMA damage and cell/tissue proliferation, and to investigate the role of the Nrf2 signaling pathway in mediating such an effect, using cultured bladder epithelial cells and mice with and without Nrf2 function. Studies carried out in Aim 4 will also serve to identify the appropriate dose levels of the dithiolethione for further experimentation in Aim 5. Aim 5 is to determine the inhibitory effect of the dithiolethione examined in Aim 4 on bladder tumorigenesis induced by a chemical carcinogen in vivo and the role of Nrf2 signaling in mediating such an effect, using wild type and Nrf2 knockout mice.