Chemosensitization of Pancreatic Cancer Cells by Curcumin and Vitamin D Receptor

描述(申请人提供)：胰腺癌(腺癌)是美国癌症死亡的第四大原因，预后最差，平均预期寿命不到一年。由于这种疾病是在晚期诊断出来的，治疗选择有限。手术只能适度地延长预期寿命。胰腺癌对常规化疗的屈光性很强。相对于放射治疗和紫杉醇，吉西他滨被认为是更有效的药物。然而，发人深省的统计数据是，与其他疗法相比，吉西他滨只能将患者的生存期延长几个月。化疗耐药的分子基础可能非常复杂，因为与吉西他滨联合治疗的成功有限。迫切需要寻找提高胰腺癌细胞对化疗敏感性的方法。在初步实验中，我们进行了全基因组siRNA筛选，以确定与吉西他滨敏感性有关的基因。我们确定了一小部分基因，其中包括 维生素D受体(VDR)和各种相关的相互作用和下游基因。我们已在体外证实VDR是吉西他滨敏感性的重要决定因素。使用一组独立的VDR siRNAs，吉西他滨在两个细胞系(Panc1和BXPC3)中实现了敏化，这是通过克隆存活率确定的。VDR是一种核激素受体，其最广为人知的功能是调节对钙稳态和骨骼矿化至关重要的基因。然而，VDR的活性是巨大和复杂的，因为它也以其抗增殖特性而闻名，并正在与细胞毒剂联合用于癌症治疗。我们发现，在DNA损伤剂处理的细胞中，VDR是形成DNA损伤灶所必需的。因此，缺乏VDR的细胞的化学增敏可能是由于促进细胞存活的DNA损伤反应的中断。这项提议旨在扩大最近的发现，即天然化合物姜黄素是VDR的配体。姜黄素作为化学增敏剂的使用已有很好的文献，但其作用模式仍不清楚。这些观察结合我们的初步数据，使我们认为姜黄素通过VDR发挥作用，增强胰腺癌细胞的化学敏感性。此外，由于VDR的细胞保护作用依赖于突变型p53状态的背景，因此也将评估其对姜黄素诱导的化疗敏感性的影响。我们的研究具有重要的临床意义，因为很大比例的胰腺肿瘤和细胞 细胞株表达突变型P53。P53的状态可能决定是否使用维生素D类似物或拮抗剂和姜黄素以及标准化疗来治疗癌症患者。

DESCRIPTION (provided by applicant): Pancreatic cancer (adenocarcinoma) is the fourth leading cause of cancer deaths in the United States and carries the worst prognosis, with median life expectancy of less than a year. As the disease is diagnosed at a late stage, treatment options are limited. Surgery only modestly improves life expectancy. Pancreatic adenocarcinomas are highly refractile to conventional chemotherapies. Relative to radiation and paclitaxal, gemcitabine is recognized to be the more efficacious drug. The sobering statistic, however, is that gemcitabine only extends patient survival by several months over other therapies. The molecular basis for chemoresistance is likely to be highly complex, as combination therapies with gemcitabine have met with limited success. There is an urgent need to identify methods to enhance sensitivity of pancreatic cancer cells to chemotherapy. In preliminary experiments, we conducted a genome-wide siRNA screen to identify genes responsible for gemcitabine sensitivity. We identified a small collection of genes that include the vitamin D receptor (VDR) and various associated interacting and downstream genes. We have validated VDR to be an important determinant of gemcitabine sensitivity in vitro. Using an independent set of VDR siRNAs, gemcitabine sensitization was achieved in two cell lines (Panc1 and BXPC3) as determined by clonogenic survival. VDR is a nuclear hormone receptor that is best known for its ability to regulate genes important for calcium homeostasis and mineralization of bone. However, the activities of VDR are vast and complex as its also known for its anti-proliferative properties and is being tested in combination with cytotoxic agents for cancer treatment. We have found that VDR is required for the formation of DNA damaged foci in cells treated with DNA damaging agents. Chemosensitization of cells lacking VDR may therefore be due to disruption of DNA damage response that promote cell survival. This proposal seeks to extend the recent finding that the natural compound curcumin is a ligand for VDR. The use of curcumin as a chemosensitizer is well documented but its mode of action remains obscure. These observations combined with our preliminary data leads us to propose that curcumin acts via VDR to enhance chemosensitzation of pancreatic cancer cells. Furthermore, as the cytoprotective actions of VDR is known to depend on the context of mutant p53 status, the impact on curcumin induced chemosensitization will also be assessed. Our studies have significant clinical ramifications as a large proportion of pancreatic tumors and cell lines express mutant p53. The status of p53 may dictate whether to treat cancer patients with a vitamin D analog or antagonist and curcumin along with standard chemotherapy.