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

描述（由申请人提供）：联合热疗和辐射效应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生畏的临床问题，导致许多治疗方案失败。根本问题是：通过靶向肿瘤细胞中专门表达（存在）的必需分子或结构，肿瘤细胞可以通过热对电离辐射（IR）特异性敏化吗？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，我们提出要了解失活共济失调毛细血管扩张突变（ATM）和端粒酶可以提高热介导的和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）GRN 163 L（一种与端粒酶RNA“hTR”模板区域互补的脂质缀合的合成DNA类似物）特异性抑制端粒酶活性增加了高温介导的IR诱导的细胞杀伤。后一结果表明，在联合热疗和放疗之前用GRN 163 L进行端粒酶失活可以改善肿瘤细胞杀伤，特异性抑制肿瘤生长。 端粒酶抑制剂（GRN 163 L）的临床试验正在进行中，因此将基于端粒酶的疗法添加到不断增长的靶向特异性放射增敏产品列表中的前景是有希望的，但是需要确定将端粒酶抑制与改变的DNA损伤感测组合的优点或局限性。因此，我们将通过抑制端粒酶和辐射信号通路来确定增强热介导的放射增敏（HIR）的机制基础，从而导致肿瘤生长控制。具体而言，我们提出了以下问题：（1）GRN 163 L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，或其最近确定的效应hSSB 1（DNA损伤检测和修复所必需的单链DNA结合蛋白），协同热介导的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到DNA双链断裂位点的募集？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。 公共卫生相关性：我们建议研究通过抑制端粒酶来增强细胞杀伤的机制基础，从而抑制肿瘤生长。我们的初步研究表明，高温激活ATM信号通路，增强端粒酶活性，从而灭活端粒酶之前的热和辐射处理将导致增加细胞杀伤。如果拟议的研究成功进行，从拟议的研究中产生的新信息将有助于设计肿瘤特异性疗法。

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.