BCG-Induced Oxidative Stress as a Target for Improved Clinical Efficacy

描述（由申请人提供）： 这项建议建立在先前的研究基础上，以确定减毒牛分枝杆菌（卡介苗）直接抗肿瘤作用的机制。膀胱内BCG仍然是高危非肌层浸润性膀胱癌（尿路上皮癌，UC）患者的标准治疗。不幸的是，BCG有很大的局限性。接受治疗的患者中只有65%对这种药物有反应。BCG的潜在感染性导致的毒性限制了其对高危患者的使用。为了提高治疗效果和/或降低治疗毒性，研究人员定义了一组强大的中间终点，用于测量BCG对人类UC细胞的直接作用。这些终点包括细胞内信号传导途径的激活，以及多种趋化因子、细胞因子和白色细胞受体的基因的反式激活。信号激活/基因表达在以细胞周期停滞和凋亡抗性为特征的表型变化中达到高潮。细胞亚群经历坏死，释放“坏死相关趋化因子”HMGB 1。如前一资助周期所示，BCG的体内抗肿瘤反应需要HMGB 1释放。该小组的终点小组提供了对BCG作用机制的深入了解，并作为评估改善治疗结果策略的“工具箱”。 对BCG的直接细胞反应的性质使研究人员假设由BCG结合/内化引起的细胞氧化应激（COS）是BCG抗肿瘤功效的关键组成部分。我们已发表的和初步的数据表明，卡介苗作为一种“自由基发生器。“BCG活力的丧失减少了自由基的产生和UC细胞对BCG在所有中间终点的反应。在活BCG的细胞结合/内化的下游，研究人员已经证明，特定氧化应激途径的反式激活和相关的自由基产生也是UC细胞对BCG的最佳反应所必需的。这些途径/自由基的药理学增强增强了UC细胞对活的和非活的BCG的反应。 该提案将检验以下假设：活BCG对UC细胞的药物遗传学效应（抗肿瘤活性的要求）是BCG产生的H2 O2的直接结果，H2 O2作为COS和细胞损伤的触发因素。BCG与UC细胞结合并内化后产生H2 O2，为第二波涉及iNOS的细胞产生的氧化剂奠定了基础。自由基（超氧化物和NO）和反应分子增强细胞内信号传导途径和下游基因表达，并导致细胞表型，定义BCG治疗效果。BCG活力的丧失与H2 O2产生减少、COS的无效诱导及其直接后果以及治疗功效降低相关。操纵COS对BCG反应的贡献者代表了增强COS活性以获得更大抗肿瘤效果的机会。与活的BCG组合，这种方法提供了更大的治疗功效的机会。当与热灭活BCG一起使用时，这些方法有望保持治疗效果，同时降低与活BCG相关的潜在毒性。 在解决这一假设时，拟议的研究将满足两个基本目标。首先，研究人员将建立在现有数据的基础上，以完成他们对BCG诱导的COS和COS相关细胞损伤的因素的理解。通过了解响应BCG激活的特定COS途径以及这些途径的下游效应，该小组将准备解决他们的第二个目标。具体地，采用稳健的体外和体内系统来测试增强UC细胞中BCG诱导的氧化剂产生和氧化损伤的策略，以改善治疗功效和/或降低治疗毒性。选定的治疗策略将以一种降低肿瘤复发和进展率以及BCG更广泛的治疗适用性的方式转化为临床。

DESCRIPTION (provided by applicant): This proposal builds on prior studies to define the mechanisms responsible for the direct antitumor effects of the attenuated mycobacterium bovis, Bacillus Calmette-Gu�rin (BCG). Intravesical BCG remains the standard of care treatment for patients with high risk, nonmuscle-invasive bladder cancer (urothelial carcinoma, UC). Unfortunately, BCG has significant limitations. Only 65% of the patients receiving treatment respond to this agent. Toxicity resulting from BCG's infectious potential limits its use to high-risk patients. With the goal of improving treatment efficacy, and/or decreasing treatment toxicity, the investigators have defined a robust set of intermediate endpoints for measuring BCG's direct effect on human UC cells. These endpoints include activation of intracellular signaling pathways, and transactivation of the genes for multiple chemokines, cytokines and white cell receptors. Signal activation/gene expression culminates in phenotypic changes characterized by cell-cycle arrest and apoptotic resistance. Subpopulations of cells undergo necrosis releasing the "necrosis related chemokine" HMGB1. As shown in the previous funding interval HMGB1 release is required for the in vivo antitumor response to BCG. The group's panel of endpoints provides insight into BCG's mechanism of action, and serves as a "toolbox" for assessing strategies to improve treatment outcomes. The nature of the direct cellular response to BCG has led the researchers to hypothesize that cellular oxidative stress (COS), elicited by BCG binding/internalization, is a critical component of BCG's antitumor efficacy. Our published and preliminary data demonstrates that BCG serves as a "free radical generator." Loss of BCG viability diminishes free radical production and the UC cell response to BCG across all intermediate endpoints. Downstream of the cellular binding/internalization of viable BCG, the researchers have demonstrated that transactivation of specific oxidative stress pathways and associated free radical production also are required for the optimal UC cell response to BCG. Pharmacologic enhancement of these pathways/free radicals potentiates the response of UC cells to viable and nonviable BCG. This proposal will test the hypothesis that viable BCG's pharmacogenetic effects on UC cells, a requirement for antitumor activity, are a direct consequence of BCG generated H2O2 which serves as the trigger for COS and cell damage. Production of H2O2 by BCG, following binding to and internalization by UC cells, sets the stage for a second wave of cell-generated oxidants involving iNOS. Free radicals (superoxide and NO), and reactive molecules potentiate intracellular signaling pathways and downstream gene expression and result in a cellular phenotype that defines the BCG-treatment effect. Loss of BCG viability is associated with decreased H2O2 production, inefficient induction of COS and its direct consequences, and decreased treatment efficacy. Manipulation of contributors to the COS response to BCG represents an opportunity to enhance COS activity for greater antitumor effect. In combination with viable BCG such approaches afford an opportunity for greater treatment efficacy. When used with heat killed BCG these approaches promise to maintain treatment efficacy while decreasing the potential toxicity associated with viable BCG. In addressing this hypothesis the proposed studies will meet two fundamental goals. First, the researchers will build upon existing data to complete their understanding of the factors contributing to BCG induced COS and COS associated cellular injury. By understanding the specific COS pathways activated in response to BCG, and the downstream effects of those pathways, the group will be poised to address their second goal. Specifically, to employ robust in vitro and in vivo systems to test strategies to potentiate BCG induced oxidant generation and oxidative damage in UC cells for improved treatment efficacy and/or decreased treatment toxicity. Selected treatment strategies will be translatable to the clinic in a way that will result in decreased tumor recurrence and progression rates and broader therapeutic applicability of BCG.