Novel Dithiolethiones for Bladder Cancer Prevention

项目描述（由申请人提供）：本项目主要研究新型二硫代硫酮预防膀胱癌。许多证据表明，致癌解毒的第2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[c]-1,2-二硫孔-3(4H)-硫酮（CPDT）是一种非常有效的体内啮齿动物膀胱ii期酶诱导剂，并假设CPDT或更有效的类似物将是一种非常有效的膀胱癌保护剂。该项目的目的1是进一步表征CPDT的2期酶诱导特性，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期酶诱导剂。这些研究将在大鼠中进行；测试化合物对三种重要的二期酶（GST， NQO1和UGT）的影响将被测量；CPDT类似物将被合成；测定CPDT的毒性和药代动力学的各项参数。目的2是确定CPDT及其更有效的类似物（在目的1中鉴定）诱导哪些GST和UGT亚型，这种诱导是否具有物种特异性，以及CPDT是否在细胞中代谢为新的诱导剂形式。GST和UGT的同种异构体在膀胱癌预防中发挥重要作用，将在人类和啮齿动物的膀胱上皮细胞中进行检测。CPDT代谢将采用放射性标记CPDT和LC/MS/MS进行研究。目的3是阐明CPDT及其类似物诱导2期酶的分子机制。我们假设Nrf2（一种转录因子）在介导这种诱导中起主要作用。目的4是评估CPDT或更有前景的类似物在体外和体内对膀胱细胞中膀胱癌基因毒性的保护作用，通过DMA损伤和细胞/组织增殖来测量，并研究Nrf2信号通路在介导这种作用中的作用，使用培养的膀胱上皮细胞和具有和不具有Nrf2功能的小鼠。在目标4中进行的研究还将有助于确定二硫代硫酮的适当剂量水平，以便在目标5中进行进一步实验。目的5是利用野生型和Nrf2敲除小鼠，确定目的4中检测的二硫代硫肽在体内对化学致癌物诱导的膀胱肿瘤发生的抑制作用以及Nrf2信号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.