Targeting pyrimidine biosynthesis in pancreatic ductal adenocarcinoma

项目摘要 胰腺导管腺癌(PDAC)是几乎所有人都能致死的肿瘤，预计将成为 到2030年成为美国癌症相关死亡的第二大原因。常规(基因毒性)化疗 构成当前护理标准的方法大多无效，并延长晚期患者的生存时间 PDAC患者平均缩短不到一年。同样，靶向小分子药物也被异常激活 致癌信号通路已显示出令人失望的临床结果，因此未能获得 FDA对PDAC的批准。这两种方法的替代策略是利用新陈代谢依赖性 它们是恶性肿瘤细胞所特有的，因为它们错乱的细胞代谢。 虽然对基因毒性和靶向治疗有很好的耐受机制，但剥夺 某些对恶性细胞增殖至关重要的营养物质似乎是癌症的不可逾越的障碍。 进步。然而，细胞有多余的手段来获得这些关键的营养物质，因此抑制一种 单一的代谢酶通常不足以阻止它们对癌细胞的作用。因此，组合封锁 可能需要多种代谢途径的共同作用，才能将关键代谢物的缺乏强加给恶性肿瘤细胞。 嘧啶核苷酸是一类代谢物，已在许多研究中表明 对PDAC和许多其他恶性肿瘤来说是必不可少的。重要的是，有几种临床分级的抑制剂 已显示出作为抗癌药物的临床前应用前景的嘧啶合成酶。然而，这些 药物在临床试验中都没有显示出疗效，在这些试验中，它们被用作单一疗法来治疗 各种恶性肿瘤。一种可能的解释是，细胞通过两条主要途径 产生核苷酸，称为从头通路和挽救通路，这些抑制物阻断从头通路的关键 途径酶二氢轮酸脱氢酶(DHODH)，从而使挽救途径完全保持不变。 我们已经确定了各种PDAC细胞系对DHODH抑制剂Bquina(BQ)的反应。我们 在细胞活力检测中发现，一些PDAC细胞株对BQ具有高度抗药性 敏感的对应者。然后，我们筛选了大约350种已知的激酶抑制剂化合物，以探测任何 可以恢复我们耐药的PDAC细胞对BQ的敏感性，这就提名了临床前BTK抑制剂 CNX-774为最强命中。随访研究表明，BQ/CNX-774联合治疗可导致 与单独使用任何一种药物相比，BQ耐药PDAC的严重细胞活力损失和嘧啶耗竭 细胞。此外，我们有强有力的证据表明，CNX-774正在以一种偏离目标的方式抑制 嘧啶残留物。因此，本研究的目的是揭示CNX-774致敏的机制 并确定这种药物组合在我们的临床前PDAC小鼠模型中是否有效。 我们的目标是为这种代谢联合疗法作为一种潜在的PDAC治疗提供临床前支持。

Project Summary Pancreatic ductal adenocarcinoma (PDAC) is almost universally lethal and is projected to become the second-leading cause of cancer related deaths in the US by 2030. Conventional (genotoxic) chemotherapy approaches that make up the current standard of care are mostly ineffective and prolong survival of advanced PDAC patients by less than one year on average. Similarly, small molecule drugs targeting aberrantly activated oncogenic signaling pathways have shown disappointing clinical results and accordingly have failed to gain FDA approval for PDAC. An alternative strategy to these two approaches is to exploit metabolic dependencies that are unique to malignant cells by virtue of their deranged cellular metabolism. While there are well-characterized resistance mechanisms to genotoxic and targeted therapies, deprivation of certain nutrients critical for proliferation of malignant cells appears to be an insurmountable barrier for cancer progression. However, cells have redundant means of acquiring these critical nutrients, and so inhibition of a single metabolic enzyme is generally not sufficient to deny them to cancer cells. Thus, combinatorial blockade of multiple metabolic pathways could be required to impose deficiency of key metabolites on malignant cells. Pyrimidine nucleotides represent a class of metabolites that has been shown in numerous studies to be essential for PDAC and a host of other malignancies. Importantly, there are several clinical grade inhibitors of pyrimidine synthesis enzymes that have shown preclinical promise as anticancer agents. However, these drugs have uniformly failed to show efficacy in clinical trials in which they were used as monotherapy against various malignancies. One potential explanation for this is that there are two major pathways by which cells generate nucleotides, termed the de novo and salvage pathways, and these inhibitors block the key de novo pathway enzyme dihydroorotate dehydrogenase (DHODH), thus leaving the salvage pathway fully intact. We’ve characterized the response of various PDAC cell lines to the DHODH inhibitor brequinar (BQ). We found that some PDAC cell lines are highly resistant to BQ in cell viability assays compared to their more sensitive counterparts. We then screened some 350 known kinase inhibitor compounds to probe for any that could restore BQ sensitivity in our resistant PDAC cell lines, and this nominated the preclinical BTK inhibitor CNX-774 as the strongest hit. Follow-up studies have shown that combined BQ/CNX-774 treatment leads to profound cell viability loss and pyrimidine depletion, compared to either drug alone, in BQ-resistant PDAC cells. Furthermore, we have strong evidence that CNX-774 is acting in an off-target manner to inhibit pyrimidine salvage. Thus, the goal of this study is to uncover the mechanism by which CNX-774 is sensitizing PDAC cells to BQ and determine if this drug combination is efficacious in our preclinical PDAC mouse models. Our goal is to provide preclinical support for this metabolic combination therapy as a potential PDAC treatment.