MODULATION OF THERAPEUTIC RESPONSE

为了改善癌症治疗，相当多的注意力已经放在辐射损伤的修饰上。该项目的主要目标是继续定义和理解独特的肿瘤生理学，解剖学，细胞和分子过程的那些方面，这些方面最终定义了肿瘤的本质，使得特定剂量的电离辐射在使用时更有效。为此目的的一种手段是研究电离辐射与各种化疗药物的相互作用，以评估是否可以使肿瘤更敏感。我们证明了用紫杉醇治疗不同的人肿瘤细胞系诱导细胞周期的G2/M期（细胞周期的放射敏感期）阻滞，这导致显著的放射增敏。因此，放射肿瘤学分支目前正在将这些临床前信息转化为放射和紫杉醇联合治疗头颈癌的临床试验。正在研究其他化疗药物（喜树碱衍生物、米托蒽醌和UCN-01等），以确定它们作为辐射增敏剂的用途。众所周知，缺氧是辐射敏感性的主要决定因素。因此，我们正在使用几种小鼠肿瘤模型来研究肿瘤缺氧。我们的方法是使用当前的侵入性技术，并将该信息扩展到正在开发的非侵入性方法，使得患者肿瘤治疗概况可以在个体基础上优化。为此，我们正在使用体外/体内存活技术，基于荧光的氧探针，硝基咪唑固定，然后免疫组织化学，F-18硝基咪唑PET扫描，血氧水平测定（BOLD）NMR，电子顺磁共振和Overhauser NMR。我们获得的信息将教会我们如何以非侵入性方式评估肿瘤中的氧气状态，以实现最佳治疗。同样，了解和定义肿瘤血管和DNA表达应该提供洞察力，了解如何新生血管对肿瘤氧的影响，从而对辐射的反应，以及提供有关这些基因的信息，表达在氧化应激反应。已经构建了几种血管抑制素和内皮抑制素表达载体用于直接肿瘤内注射或全身脂质体递送。此外，目前正在制备含有具有用于内皮抑制素和血管抑制素表达的开关的载体的体外/体内肿瘤模型，使得可以在对辐射的响应性的背景下以及在非侵入性功能成像的背景下评估血管分布的影响。正在研究肿瘤内的基因表达作为氧状态、再灌注、电离辐射暴露和一般氧化应激的函数，以使用cDNA微阵列技术确定在肿瘤细胞对单独的电离辐射或与药理学试剂组合的损伤的反应性和存活中重要的那些分子事件。其目的是扩展我们的肿瘤微环境，生理学和分子生物学的知识，并将这些知识与研究肿瘤的非侵入性方法相关联，以便我们设计出高效和有效的治疗方案，使用辐射与药理学药物相结合或串联。

In the interest of improving cancer treatment, considerable attention has been placed on the modification of radiation damage. The major goal of this project continues to define and understand those aspects of unique tumor physiology, anatomy, cellular, and molecular processes that ultimately define the very nature of a tumor such that a particular dose of ionizing radiation, when used will be more effective. One means to that end is to investigate the interaction of ionizing radiation with a variety of chemotherapy agents to assess if tumors can be made more sensitive. We demonstrated that treatment of diverse human tumor cell lines with paclitaxel induced a block in G2/M of the cell cycle (radiosensitive phases of the cell cycle) which resulted in significant radiosensitization. As a consequence, translation of this pre-clinical information into a clinical trail combining radiation and paclitaxel in the treatment of head/neck cancer is currently underway in the Radiation Oncology Branch. Other chemotherapeutic agents (camptothecin derivatives, mitoxanthone, and UCN-01, among others) are being investigated to determine their use as radiation sensitizing agents. It is well established that hypoxia is a major determinant of radiation sensitivity. Therefore, we are using several murine tumor models to study tumor hypoxia. Our approach is to use current invasive techniques and extend that information to non- invasive methods that are under development, such that patient tumor treatment profiles may optimized on an individual basis. To that end we are using in vitro/in vivo survival techniques, fluorescent based oxygen probes, nitroimidazole fixation followed by immunohistochemistry, F-18 nitroimidazole PET scanning, blood oxygen level determination (BOLD) NMR, electron paramagnetic resonance, and Overhauser NMR. The information we acquire will teach us how to assess oxygen status in a tumor in a non-invasive manner to effect optimum treatment. Likewise, understanding and defining tumor vasculature and DNA expression should provide insight to understanding how neoangiogenesis impacts on tumor oxygen and consequently responsiveness to radiation, as well as provide information regarding those genes that are expressed in response to oxidative stress. Several angiostatin and endostatin expression vectors have been constructed for direct intra- tumor injection or systemic liposome delivery. Moreover, in vitro/in vivo tumor models containing vectors with switches for expression of endostatin and angiostatin are being made presently, such that the impact of vascularity can be assessed in the context of responsiveness to radiation and also in the context of non-invasive functional imaging. Gene expression within a tumor as a function of oxygen status, reperfusion, ionizing radiation exposure and general oxidative stress is being investigated to determine those molecular events that are important in the tumor cell responsiveness and survival to insult by ionizing radiation alone or in combination with pharmacologic agents using cDNA microarray technology. The aim is to extend our knowledge of tumor micro-environment, physiology, and molecular biology and to correlate such knowledge with non-invasive methods of studying tumors so that we design efficient and effective treatment protocols using radiation in combination or tandem with pharmacologic agents.