Tumor-cell-specific targets for combined hyperthermia and radiation effects

描述(申请人提供)：热疗和辐射联合作用的肿瘤细胞特异性靶点。放射治疗无法控制肿瘤生长仍然是一个令人望而生畏的临床问题，导致许多治疗方案失败。根本的问题是：肿瘤细胞是否可以通过靶向肿瘤细胞中唯一表达(存在)的基本分子或结构来特异性地对热电离辐射(IR)敏感？其中一种在大多数肿瘤中表达，在体细胞中不表达的因子是端粒酶。此外，正常组织和肿瘤组织之间端粒酶活性和细胞动力学的差异表明，靶向端粒酶将是相对安全的。在这项拨款申请中，我们建议了解共济失调-毛细血管扩张突变(ATM)和端粒酶失活如何增强热介导和IR诱导的肿瘤细胞杀伤。我们的初步数据表明：(1)热休克激活了与IR激活的ATM信号通路重叠的ATM信号通路；(2)高温瞬时增强了端粒酶活性；(3)GRN163L(一种与端粒酶RNA“HTR”模板区域互补的脂质结合合成DNA类似物)对端粒酶活性的特异性抑制增加了高温介导的IR诱导的细胞杀伤。后者的结果表明，在联合热疗和放射治疗之前用GRN163L灭活端粒酶可以提高肿瘤细胞的杀伤率，特别是抑制肿瘤的生长。端粒酶抑制剂(GRN163L)的临床试验仍在进行中，因此，将基于端粒酶的疗法添加到越来越多的靶向特异性放射增敏产品中的前景是光明的，但结合端粒酶抑制和改变的DNA损伤感知的优势或限制需要确定。因此，我们将通过抑制端粒酶和辐射信号通路来增强热介导放射增敏(HIR)的机制，从而达到控制肿瘤生长的目的。具体地说，我们提出以下问题：(1)GRN163L对端粒酶的抑制是否在对正常组织几乎没有毒性的情况下增强了热介导IR诱导的肿瘤控制？(2)同时失活端粒酶和ATM或其最近发现的效应蛋白hSSB1(DNA损伤检测和修复所必需的单链DNA结合蛋白)是否协同热介导IR诱导的肿瘤控制？(3)在端粒酶活性存在和不存在的情况下，热是否影响DNA损伤感知和修复蛋白向DNA双链断裂位置的募集？因此，确定热和/或IR对ATM功能和端粒代谢的影响不仅有助于我们理解HIR的机制，而且有助于开发新的肿瘤治疗策略。 与公共健康相关：我们建议研究通过抑制端粒酶增强细胞杀伤力的机制基础，在加热和放射治疗之前，端粒酶可能导致抑制肿瘤生长。我们的初步研究表明，高温激活ATM信号通路并增强端粒酶活性，因此在加热和放射治疗之前灭活端粒酶将导致细胞杀伤增加。如果建议的研究成功进行，从建议的研究产生的新信息将有助于设计肿瘤特异性治疗方法。

DESCRIPTION (provided by applicant): Tumor-cell-specific targets for combined hyperthermia and radiation effects. The inability of radiotherapy to control tumor growth is still a daunting clinical problem that leads to the failure of many treatment regimens. The fundamental question is: can tumor cells be specifically sensitized to ionizing radiations (IR) by heat by targeting essential molecules or structures exclusively expressed (present) in tumor cells? One such factor, expressed in most tumors and silent in somatic cells, is telomerase. Moreover, differences in telomerase activity and cell kinetics between normal and tumor tissues suggest that targeting telomerase would be relatively safe. In this grant application we propose to understanding how inactivation of ataxia-telangiectasia mutated (ATM) and telomerase could enhance heat mediated and IR-induced tumor cell killing. Our preliminary data suggest that: (1) Heat shock activates ATM signaling pathways that overlap with those activated by IR; (2) Hyperthermia transiently enhanced telomerase activity and; (3) The specific inhibition of telomerase activity by GRN163L (a lipid conjugated synthetic DNA analogue complementary to the template region of telomerase RNA "hTR") increased hyperthermia-mediated IR-induced cell killing. The latter result suggests that telomerase inactivation with GRN163L prior to combined hyperthermia and radiotherapy could improve tumor cell killing, specifically inhibiting tumor growth. Clinical trials are ongoing with telomerase inhibitor (GRN163L), the prospect of adding telomerase-based therapies to the growing list of target-specific radiosensitizing products is therefore promising, but the advantages or limitations of combining telomerase inhibition with altered DNA damage sensing needs to be determined. Therefore, we will determine the mechanistic basis of enhancing heat-mediated radiosensitization (HIR) by inhibiting telomerase and radiation signaling pathways, which result in the tumor growth control. Specifically, we propose to ask the following questions: (1) Does telomerase inhibition by GRN163L enhance heat-mediated IR-induced tumor control with little toxicity to normal tissue? (2) Does simultaneous inactivation of telomerase and ATM, or its recently identified effector hSSB1 (a single-strand DNA binding protein essential for DNA damage detection and repair), synergize heat-mediated IR-induced tumor control? (3) Does heat influence DNA damage sensing and the recruitment of repair proteins to DNA double strand break sites in the presence and absence of telomerase activity? Thus, determining the influence of heat and/or IR on ATM function and telomere metabolism will not only add to our understanding of the mechanisms of HIR but will aid in the development of new tumor treatment strategies. PUBLIC HEALTH RELEVANCE: We propose to investigate the mechanistic basis of enhancing cell killing by inhibiting telomerase prior heat and radiation treatment that could result in the suppression of tumor growth. Our preliminary studies suggest that hyperthermia activates ATM signaling pathways and enhances telomerase activity, thus inactivating telomerase prior heat and radiation treatment would result in increased cell killing. If the proposed research is successfully carried out, the novel information generated from the proposed studies will be useful in designing tumor specific therapies.