Utilizing HuR to optimize the treatment of pancreatic cancer

描述（由申请人提供）：胰腺癌全基因组测序和针对胰腺癌的靶向治疗的互补搜索分散了该领域的注意力，使其无法专注于优化临床上最常用的药物之一（吉西他滨）以对抗这种毁灭性疾病。前瞻性和随机临床试验表明，一组选定的人胰腺癌表现出对化疗药物吉西他滨的敏感性。虽然该亚组较小（例如，CONKO-001证明10%的患者在辅助治疗中对吉西他滨产生持久应答），但吉西他滨的这些独特发现为设计分子策略提供了依据，以将疗效扩展至更多患者或预测哪些患者可能从基于吉西他滨的治疗中获益最佳。吉西他滨单药治疗仍然是辅助治疗的标准治疗，最近在晚期患者中进行的一项阳性试验已将吉西他滨-Abraxane确定为首选的一线治疗方案。在本提案中，我们将使用来自多机构III期试验的样本建立吉西他滨疗效的前所未有的预测标志物，并开发适用于所有患者（局部和晚期）的生物标志物测定。此外，我们将深入了解控制吉西他滨代谢的分子机制。在先前的研究中，我们证明了胰腺癌细胞中的转录后基因调控在吉西他滨疗效中起着重要作用。我们证明了RNA结合蛋白HuR（ELAV 1）上调脱氧胞苷激酶（dCK），这是一种产生DNA前体分子并代谢核苷类似物吉西他滨的酶。验证我们的体外研究结果，细胞质HuR蛋白表达增加的患者肿瘤与接受吉西他滨治疗的患者切除术后生存率提高相关。我们假设dCK（通过HuR稳定）有效地代谢前药吉西他滨，从而增强对癌细胞的药物功效。最近，我们将CMPK 1和RRM 2确定为在吉西他滨代谢中发挥核心作用的两个额外的HuR靶点。在此，我们将1）使用来自胰腺癌辅助吉西他滨治疗的多机构、随机、临床试验（ESPAC 3）的手术标本，牢固地确立HuR作为吉西他滨治疗胰腺癌功效的真实预测标志物; 2）评估细胞学抽吸物确定HuR状态的可行性和准确性（与手术标本相比），这将扩大该测试对晚期疾病患者的相关性;和3）精确确定HuR如何调节吉西他滨功效通过生物化学和细胞测定以及胰腺癌细胞中吉西他滨代谢物的光谱分析，研究了吉西他滨（作为单一药剂和与Abraxane）的作用。我们希望这些研究的结果能够立即提高我们识别哪些患者最有可能从吉西他滨治疗中获益的能力。此外，我们预计HuR对吉西他滨代谢的全局控制机制的深入研究最终将导致增强吉西他滨反应的治疗策略。

DESCRIPTION (provided by applicant): Pancreatic cancer genome-wide sequencing and the complementary search for targeted therapies against pancreatic cancer have distracted the field from focusing on optimizing one of the most clinically utilized agents (gemcitabine) against this devastating disease. Prospective and randomized clinical trials reveal that a select set of human pancreatic cancers exhibit sensitivity to the chemotherapeutic agent gemcitabine. While this subset is small (for instance, CONKO-001 demonstrates that 10% of patients experience a durable response to gemcitabine in the adjuvant setting), these findings unique to gemcitabine provide a rationale to devise molecular strategies to expand the efficacy to more patients or predict which patients might best benefit from gemcitabine-based therapies. Gemcitabine monotherapy remains the standard of care in the adjuvant setting and a recent positive trial in advanced patients has established gemcitabine-Abraxane as a preferred front line regimen. In the present proposal, we will establish an unprecedented predictive marker for gemcitabine efficacy using samples from a multi-institution phase III trial and develop a biomarker assay applicable to all patients (both localized and advanced). In addition, we will gain insights into molecular mechanisms that govern the metabolism of gemcitabine. In a prior study, we demonstrated that post-transcriptional gene regulation in pancreatic cancer cells plays an important role in gemcitabine efficacy. We demonstrated that the RNA binding protein, HuR (ELAV1), up-regulates deoxycytidine kinase (dCK), an enzyme that produces DNA precursor molecules and also metabolizes the nucleoside analog, gemcitabine. Validating our in vitro findings, patient tumors with increased cytoplasmic HuR protein expression were associated with improved survival after resection in patients treated with gemcitabine. We hypothesize that dCK (stabilized by HuR) efficiently metabolizes the prodrug gemcitabine, thereby enhancing drug efficacy against cancer cells. Recently, we identified CMPK1 and RRM2 as two additional HuR targets that play a central role in gemcitabine metabolism. Herein, we will 1) firmly establish HuR as a bona fide predictive marker of gemcitabine efficacy for pancreatic cancer treatment using surgical specimens from a multi-institutional, randomized, clinical trial of adjuvant gemcitabine therapy for pancreatic cancer (ESPAC3); 2) evaluate the feasibility and accuracy of cytologic aspirates to determine HuR status (compared to surgical specimens), which will expand the relevance of the test to patients with advanced disease; and 3) determine precisely how HuR regulates gemcitabine efficacy (both as single agent and with Abraxane) through biochemical and cellular assays, and spectroscopic analyses of gemcitabine metabolites in pancreatic cancer cells. We expect results of these studies to yield immediate improvement in our ability to identify which patients are most likely to benefit from gemcitabine-based therapies. In addition, we expect that mechanistic insights gained into HuR's global control of gemcitabine metabolism will eventually lead to therapeutic strategies that enhance gemcitabine response.