Novel approaches to enhance tumor cell cytotoxicity of alkylating agents

增强烷化剂肿瘤细胞细胞毒性的新方法

• 批准号: 8676463
• 负责人: Robert W Sobol
• 金额: $ 9.98万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-02 至 2014-10-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8676463
• 关键词: Address; Adjuvant Therapy; Alkylating Agents; Alkylation; Anabolism; Antineoplastic Agents; Apoptosis; Base Excision Repairs; Binding Proteins; Biogenesis; Biological Markers; Brain; Cancer Etiology; Cell Death; Cell Line; Cell Survival; Cells; Cessation of life; Complex; Coupled; DNA Alkylation; DNA Damage; DNA-Directed DNA Polymerase; Diagnosis; Drug resistance; Elements; Enzymes; Failure; Glioblastoma; Glioma; Goals; Human; Lesion; Lysine; Malignant Neoplasms; Malignant neoplasm of brain; Mediating; Methylation; Methyltransferase; Mitochondria; Modification; Necrosis; Nude Mice; Pathway interactions; Poly Adenosine Diphosphate Ribose; Polymerase; Process; Proteins; Regulation; Resistance; Role; Signal Transduction; Testing; United States; Xenograft Model; base; cancer diagnosis; cytotoxic; cytotoxicity; drug efficacy; improved; in vivo; inhibitor/antagonist; insight; mortality; neoplastic cell; novel; novel strategies; poly ADP-ribose glycohydrolase; repair enzyme; repaired; research study; response; sensor; signal processing; success; temozolomide; tumor

DESCRIPTION (provided by applicant): Glioblastoma is a major cause of cancer related death in the United States, with approximately 17,000 new cases of brain cancer diagnosed annually. Unfortunately, therapy remains inadequate and the mortality rate is high. Limited success in the treatment of glioblastoma has been demonstrated with the alkylating agent Temozolomide (TMZ). However, as with many alkylating agents, drug resistance has limited its efficacy. The base excision repair (BER) pathway provides significant resistance to TMZ by repairing greater than 80% of the TMZ-induced base lesions. As such, it is reasonable to expect that BER provides a significant level of resistance to TMZ and therefore enhanced TMZ efficacy may be obtained by blocking or interrupting repair and thereby promoting BER failure. The overall goals of this project are to utilize strategies to circumvent resistance to TMZ to enhance the cytotoxicity and potentially the efficacy of this alkylating agent. As the rate-limiting enzyme in BER, DNA polymerase ss (Polss) is important to facilitate repair and to maintain cell survival following DNA damage. Therefore, inhibition of Polss will enhance TMZ response. Specifically, we wil characterize a novel regulatory mechanism of Polss (lysine di-methylation) that can be exploited to inhibit Polss and enhance alkylating agent-induced cell death by enhancing the accumulation of cytotoxic BER intermediates (Aim 1). We posit that Polss inhibition or BER failure signals via poly(ADP)ribose (PAR) synthesis and NAD+/ATP depletion by a process that requires activation of PARP1 & PARP2 and is regulated by the enzyme PARG. We find that BER failure- induced cell death results from energy (NAD+ & ATP) depletion due to elevated PAR synthesis mediated by the PARP1/PARP2 BER sensor complex, suggesting that the response to TMZ can be enhanced via increased PAR synthesis or depletion of cellular NAD+ synthesis (Aim 2) and/or deregulation of the BER enzyme PARG (Aim 3). Overall, we will test the hypothesis that the BER pathway is a determinant of resistance to TMZ and therefore selectively targeting the BER pathway will significantly enhance TMZ efficacy. In each of our three specific aims, our goals are to identify and functionally characterize key elements of the BER pathway that control cellular responses to alkylating agents with the goal of increasing TMZ-induced cytotoxicity in cells from glioma tumors. Relevance: The proposed studies will provide new biomarkers of response to alkylation-induced DNA damage and cell death and provide insight into mechanisms that can be exploited to enhance response. Insights gained from these studies have the potential to identify novel targets for adjuvant therapies including BER inhibitors and NAD+ biosynthesis modulators that can be combined with alkylators to improve anticancer drug efficacy.

描述（由申请人提供）：胶质母细胞瘤是美国癌症相关死亡的主要原因，每年诊断出约 17,000 例脑癌新病例。不幸的是，治疗仍然不足，死亡率很高。烷化剂替莫唑胺 (TMZ) 在治疗胶质母细胞瘤方面取得的成功有限。然而，与许多烷化剂一样，耐药性限制了其功效。碱基切除修复 (BER) 途径可修复 80% 以上的 TMZ 诱导的碱基损伤，从而对 TMZ 产生显着的抵抗力。因此，可以合理地预期 BER 对 TMZ 具有显着水平的抵抗力，因此可以通过阻止或中断修复并从而促进 BER 故障来获得增强的 TMZ 功效。该项目的总体目标是利用策略来规避 TMZ 耐药性，以增强该烷化剂的细胞毒性和潜在功效。作为 BER 中的限速酶，DNA 聚合酶 ss (Polss) 对于促进 DNA 损伤后的修复和维持细胞存活非常重要。因此，抑制 Polss 将增强 TMZ 反应。具体来说，我们将描述 Polss（赖氨酸二甲基化）的一种新型调节机制，该机制可用于抑制 Polss 并通过增强细胞毒性 BER 中间体的积累来增强烷化剂诱导的细胞死亡（目标 1）。我们假设 Polss 抑制或 BER 失败信号是通过聚 (ADP) 核糖 (PAR) 合成和 NAD+/ATP 消耗而发出的，该过程需要激活 PARP1 和 PARP2，并受 PARG 酶调节。我们发现，BER 失败诱导的细胞死亡是由于 PARP1/PARP2 BER 传感器复合物介导的 PAR 合成增加而导致能量（NAD+ 和 ATP）消耗，这表明对 TMZ 的反应可以通过增加 PAR 合成或细胞消耗来增强。 NAD+ 合成（目标 2）和/或 BER 酶 PARG 的失调（目标 3）。总体而言，我们将检验以下假设：BER 途径是 TMZ 耐药性的决定因素，因此选择性靶向 BER 途径将显着增强 TMZ 功效。在我们的三个具体目标中，我们的目标是识别和功能表征 BER 通路的关键元件，这些元件控制细胞对烷化剂的反应，以增加 TMZ 诱导的神经胶质瘤细胞的细胞毒性。相关性：拟议的研究将提供对烷基化诱导的 DNA 损伤和细胞死亡反应的新生物标志物，并深入了解可用于增强反应的机制。从这些研究中获得的见解有可能确定辅助治疗的新靶点，包括 BER 抑制剂和 NAD+ 生物合成调节剂，它们可以与烷化剂结合使用，以提高抗癌药物的疗效。