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

描述（由申请人提供）：肿瘤细胞特异性靶点，用于联合热疗和辐射效应。放疗无法控制肿瘤生长仍然是一个令人生畏的临床问题，导致许多治疗方案的失败。最根本的问题是：肿瘤细胞能否通过靶向肿瘤细胞中唯一表达（存在）的基本分子或结构而对电离辐射（IR）通过热特异性敏感？其中一个在大多数肿瘤中表达而在体细胞中沉默的因子是端粒酶。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，靶向端粒酶是相对安全的。在这项拨款申请中，我们提出了解失活的失调性毛细血管扩张突变（ATM）和端粒酶如何增强热介导和红外诱导的肿瘤细胞杀伤。我们的初步数据表明：(1)热休克激活的ATM信号通路与IR激活的信号通路重叠；(2)高温瞬时增强端粒酶活性；(3) GRN163L（一种与端粒酶RNA“hTR”模板区互补的脂质偶联合成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。后一个结果表明，在热疗联合放疗前用GRN163L灭活端粒酶可以提高肿瘤细胞杀伤，特异性抑制肿瘤生长。端粒酶抑制剂（GRN163L）的临床试验正在进行中，因此，将端粒酶为基础的治疗方法添加到不断增长的靶向特异性放射增敏产品列表中是有希望的，但是端粒酶抑制与改变DNA损伤感知相结合的优势或局限性需要确定。因此，我们将确定通过抑制端粒酶和辐射信号通路来增强热介导的放射敏化（HIR），从而控制肿瘤生长的机制基础。具体而言，我们提出以下问题：(1)GRN163L抑制端粒酶是否增强了热介导的ir诱导的肿瘤控制，而对正常组织的毒性很小？(2)端粒酶和ATM的同时失活，或其最近发现的效应物hSSB1 （DNA损伤检测和修复所必需的单链DNA结合蛋白）是否协同热介导的ir诱导的肿瘤控制？(3)在端粒酶活性存在和缺失的情况下，热是否会影响DNA损伤感知和修复蛋白对DNA双链断裂位点的募集？因此，确定热量和/或IR对ATM功能和端粒代谢的影响不仅将增加我们对HIR机制的理解，而且将有助于开发新的肿瘤治疗策略。

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.