Selective Sensitization of Pancreatic Cancer to Therapy by Chk1 and PARP1 Inhibit

描述（由申请人提供）：我们最近发现Chk1的小分子抑制剂可以取消G2检查点并抑制胰腺癌细胞中的HRR（同源重组修复）。重要的是，Chk1抑制优先使p53突变的肿瘤细胞敏感，K-Ras突变也可能赋予对Chk1抑制的敏感性。PARP抑制剂已被证明在具有其他DNA损伤修复缺陷的细胞中作为单一药物和放射增敏剂具有优先疗效。因此，我们假设HRR （Chk1抑制剂MK-8776）和PARP1（奥拉帕尼）的抑制会选择性地使胰腺癌细胞对辐射敏感。我们工作的长期目标是通过选择性靶向DNA修复途径（结合放化疗）来改善胰腺癌（以及其他p53/K- Ras突变肿瘤）患者的预后。本应用的目的是联合DNA损伤反应途径抑制剂，以改善基于吉西他滨的胰腺癌放化疗，并通过抑制Chk1和PARP1了解致敏和肿瘤细胞选择性的机制。在Specific Aim 1中，我们将通过抑制Chk1和PARP1来确定肿瘤细胞选择性和放射增敏的机制。我们将通过选择性地增加p53-和K-Ras突变胰腺癌细胞中未修复的双链断裂，来验证Chk1和PARP1联合抑制对DNA损伤（辐射和吉西他滨辐射）产生协同增敏的假设。我们将利用正常细胞以及等基因p53和K-Ras癌细胞来确定p53和K-Ras在选择性中的作用。为了研究Chk1和PARP1联合抑制肿瘤细胞的放射致敏机制，我们将评估DNA损伤、DNA损伤反应和HRR。为了确定Chk1和PARP1抑制剂如何相互作用产生放射致敏，我们将选择性地操纵MK-8776对HRR和G2检查点的抑制作用。在Specific Aim 2中，我们将验证Chk1和PARP1联合抑制选择性地使p53和K-Ras突变胰腺肿瘤异种移植物对辐射和吉西他滨辐射敏感的假设，而正常组织的敏感程度最低。我们将鉴定p53和K- Ras突变患者衍生的胰腺肿瘤，并确定Chk1和PARP1联合抑制对吉西他滨和放疗致敏的疗效。为了理解与致敏相关的机制，我们将分析Aim 1中鉴定的关键DNA损伤反应蛋白。十二指肠毒性，即胰腺照射的剂量限制性毒性，将通过Chk1和PARP1抑制与放射和吉西他滨放射联合进行评估。这些目标的成功完成将通过提供新的治疗方案以及用于患者选择的生物标志物来影响胰腺癌患者的治疗。我们的跟踪记录和研究团队使我们极有可能成功完成这些目标并将其转化为临床。

DESCRIPTION (provided by applicant): We have recently shown that small molecule inhibitors of Chk1 abrogate the G2 checkpoint and inhibit HRR (homologous recombination repair) in pancreatic cancer cells. Importantly, Chk1 inhibition preferentially sensitizes p53-mutant tumor cells and K-Ras mutation may also confer sensitivity to Chk1 inhibition. PARP inhibitors have demonstrated preferential efficacy as single agents and as radiosensitizers in cells with other DNA damage repair defects. Thus, we hypothesize that inhibition of HRR (by the Chk1 inhibitor MK-8776) and PARP1 (by olaparib) will selectively sensitize pancreatic cancer cells to radiation. The long-term goal of our work is to improve the outcome of patients with pancreatic cancer (and other p53/K- Ras -mutant tumors) by selectively targeting DNA repair pathways (in combination with chemoradiation). The goals of this application are to combine inhibitors of DNA damage response pathways in order to improve gemcitabine-based chemoradiotherapy for pancreatic cancer as well as to understand the mechanisms of sensitization and tumor cell selectivity by Chk1 and PARP1 inhibition. In Specific Aim 1 we will determine the mechanisms of tumor cell selectivity and radiosensitization by Chk1 and PARP1 inhibition. We will test the hypothesis that combined inhibition of Chk1 and PARP1 produce synergistic sensitization to DNA damage (radiation and gemcitabine-radiation) by increasing unrepaired double strand breaks selectively in p53- and K-Ras mutant pancreatic cancer cells. We will utilize normal cells as well as isogenic p53 and K-Ras cancer cells to determine the roles of p53 and K-Ras in selectivity. To address the mechanisms of radiosensitization in response to the combination of Chk1 and PARP1 inhibition in cancer cells, we will assess DNA damage, DNA damage responses, and HRR. To determine how Chk1 and PARP1 inhibitors interact to produce radiosensitization we will selectively manipulate the inhibitory effects of MK-8776 on HRR versus the G2 checkpoint. In Specific Aim 2 we will test the hypothesis that combined Chk1 and PARP1 inhibition selectively sensitize p53 and K-Ras mutant pancreatic tumor xenografts to radiation and gemcitabine-radiation with minimal normal tissue sensitization. We will identify p53 and K- Ras -mutant patient-derived pancreatic tumors and determine the efficacy of combined Chk1 and PARP1 inhibition on sensitization to gemcitabine and radiation. To understand the mechanisms associated with sensitization, we will analyze key DNA damage response proteins identified in Aim 1. Duodenal toxicity, the dose limiting toxicity for irradiation of the pancreas, will be assessed in response to Chk1 and PARP1 inhibition in combination with radiation and gemcitabine-radiation. Successful completion of these aims will IMPACT therapy for patients with pancreatic cancer by providing new therapy options as well as biomarkers for patient selection. Our track record and team of investigators make it highly likely that we will succeed in the completion of these aims and their translation to the clinic.