Characterization of Drug Survival by Pancreatic Cancer Cells in vitro and in vivo

描述(申请人提供)：胰腺癌(PCA)是美国第四大致死性癌症，平均预期寿命不到一年。PCa对常规化疗的反应不佳，因为疾病在确诊时已进展到晚期。吉西他滨(Gem)通常被用作一线治疗，但与其他单一药物或联合治疗相比，只能将患者的生存时间延长几个月。Gem+NaB-紫杉醇的组合最近被证明比单独使用Gem可延长生存期约2个月。FOLFIRINOX方案是一种多种药物的配方，与单用吉西他滨相比，胰腺癌患者的生存期增加了一倍(~4-6个月)，显示出了希望。然而，与这种治疗相关的高毒性可能会限制能够耐受这种方案的患者。了解并针对化疗耐药的分子机制是改善治疗结果的合理途径。抑制这种途径应该会让现有的药物杀死更多的肿瘤细胞，从而延长患者的生存时间。重要的是，化疗增敏剂可以减少化疗的有效剂量，因此也可以减少毒副作用。癌细胞严重依赖于生存途径，使它们能够耐受 广泛的外在和内在压力，通常会阻碍细胞生长。吉西他滨、紫杉醇和FOLFIRINOX等药物抑制DNA复制和染色体分离，这两个过程在癌细胞中已经不稳定。进化到允许癌细胞耐受基因组不稳定的生存途径可能是允许细胞在这些药物治疗下存活的原因。我们进行了全基因组siRNA筛选，以确定对吉西他滨治疗的胰腺癌细胞的生存至关重要的基因。这项工作揭示了维生素D受体(VDR)转录因子在决定细胞对药物的反应中存活的一个意想不到的作用。VDR被1，25-OH维生素D3激活，最为人所知的是调节钙稳态和骨矿化的重要基因。我们已经确定了促进DNA修复的新作用，这对胰腺癌细胞吉西他滨的生存至关重要。我们的分子、药理学和细胞生物学数据有力地表明VDR对于胰腺癌细胞存活吉西他滨是必不可少的。我们认为，这反映了VDR在保护皮肤免受紫外线在维生素D生产中的有害但必要的好处方面的重要性的进化适应。我们在这项R21应用中建议解决胰腺癌细胞如何利用VDR来生存吉西他滨和其他化疗药物。我们还将进行体内研究，测试一种抗真菌药物在增强宝石杀伤力方面的效果。 Pca患者来源的肿瘤异种移植，以及该疾病的小鼠模型。这是一个令人兴奋的R21提议，因为它有很高的翻译潜力和对PCa细胞如何在药物治疗中生存的新见解。

DESCRIPTION (provided by applicant): Pancreatic cancer (PCa) is the 4th deadliest cancer in the US, with median life expectancy of less than a year. PCa does not respond well to conventional chemotherapies as the disease has progressed to late stages by the time of diagnosis. Gemcitabine (Gem) is commonly used as frontline treatment, but only extends patient survival by several months over other single agent or combination therapies. The combination of Gem + nab- paclitaxel was recently shown to extend survival by ~2 months over Gem alone. The FOLFIRINOX regimen is a formulation of multiple drugs that has shown promise by doubling (~4-6 months) survival of pancreatic cancer patients over gemcitabine alone. However, high toxicity associated with this treatment may limit the patients that can tolerate this regimen. Understanding and targeting the molecular mechanism responsible for chemoresistance is a rational approach to improving treatment outcomes. Inhibiting such pathways should allow existing drugs to kill more tumor cells, and thus extend patient survival. Importantly, chemosensitizers may reduce the effective dose of chemo and thus also reduce toxic side effects. Cancer cells rely critically on survival pathways that allow them to tolerate a broad range of extrinsic and intrinsic stresses that would normally block cell growth. Drugs such as gemcitabine, paclitaxel, and FOLFIRINOX inhibit DNA replication and chromosome segregation, two processes that are already destabilized in cancer cells. The survival pathways that have evolved to allow cancer cells to tolerate genome instability are likely responsible for allowing cells to survive treatment with these drugs. We conducted a genome-wide siRNA screen to identify genes that are critically important for the survival of pancreatic cancer cells treated with gemcitabine. This effort revealed an unexpected role for the Vitamin D receptor (VDR) transcription factor in dictating cell survival in response to drugs. VDR is activated by 1,25-OH vitamin D3 and is best known for regulating genes important for calcium homeostasis and bone mineralization. We have identified a new role in promoting DNA repair that is crucial for gemcitabine survival by pancreatic cancer cells. Our combined molecular, pharmacological and cell biological data strongly suggest that VDR is essential for pancreatic cancer cells to survive gemcitabine treatment. We believe that this reflects evolutionary adaptation of the importance of VDR in protecting skin from the harmful yet necessary benefits of UV in the production of Vitamin D. We propose in this R21 application to address how VDR is used by pancreatic cancer cells to survive gemcitabine and other chemotherapeutic agents. We will also conduct in vivo studies that test the efficacy of an anti-fungal drug in enhancing Gem killing of a PCa patient derived tumor xenograft, as well as a mouse model for the disease. This is an exciting R21 proposal because of its high translational potential and novel insights into how PCa cells survive drug treatment.