COMBINED RADIOIMMUNOTHERAPY WITH RADIOTHERAPY

这项赠款申请检验了放射性标记抗体异质性是放射免疫治疗(RIT)失败的主要来源的假设。这一局限性可以通过RIT和外照射(XRT)相结合来克服。本研究将研究XRT和RIT的相互作用，并确定这两种方式的最佳组合以获得最大的肿瘤疗效。这一假说将在小鼠SW1222结直肠癌移植模型系统中进行验证，该模型以完整的A33Ig G单抗及其单链高变型SFV片段为靶向。研究目的有四个：(1)用荧光板放射自显影技术测定放射性标记的A33Ig G在SW1222肿瘤移植瘤系统中的三维微分布。关于抗体/抗原摩尔比、分子量的影响、通过同时给药单链高变片段SFV A33和亲本A33免疫球蛋白，以及在预外照射之后，分布的依赖性将被研究。(2)确定放射性组织损伤如何促进/阻碍抗体进入肿瘤。这将通过传统的组织学和免疫组织化学染色来实现，旨在确定辐射损伤对肿瘤血液供应、肿瘤细胞密度以及抗原密度和炎症反应的影响。这些变化将被用来为从特定的目标1测量放射性标记抗体分布提供科学的理论基础。此外，这个目标将试图通过测定经历凋亡细胞死亡的细胞比例(通过TUNEL法)和周期细胞比例的变化(由IUdR掺入和Ki67和增殖细胞核抗原免疫组织化学确定)来量化肿瘤细胞反应的变化，作为有丝分裂细胞死亡的替代。(3)通过XRT和RIT单独及联合治疗后肿瘤的生长延缓和治愈来确定治疗效果。为了确定最佳的联合治疗，将进行这样的实验，即先进行XRT，然后同时进行RIT、XRT和RIT，并在XRT之前进行RIT。肿瘤反应的变化将与目标1和目标2的结果相关。(4)开发一个放射生物学模型，该模型根据不同的活动分布确定治疗效果。该模型将使用放射自显影数据(目标1)的来源分布信息进行测试，以预测特定目标3测量的总体肿瘤反应。

This grant application examines the hypothesis that radiolabeled antibody heterogeneity is the principal source of failure of radioimmunotherapy (RIT). It proposes that this limitation can be overcome by the combination of RIT with external beam radiotherapy (XRT). This study will investigate the interaction between XRT with RIT, and determine the optimum combination of these two modalities for maximum tumor efficacy. The hypothesis will be tested with the murine SW1222 colorectal xenograft model system using intact A33 IgG monoclonal antibody as the targeting agent and its single chain hypervariable sFv fragment. There are four specific aims: (1) To determine the 3D microdistribution of radiolabeled A33 IgG within the SW1222 tumor xenograft system using phosphor plate autoradiography. The dependence of the distribution will be investigated with respect of the antibody/antigen molar ratio, the effect of molecular weight, by concomitant administration of the single chain hypervariable fragment sFv A33 with the parent A33 IgG, and following pre-external beam irradiation. (2) To determine how radiation tissue damage facilitates/impedes the penetration of antibody into the tumor. This will be achieved by conventional histological and immunohistochemical stains designed to ascertain the effects of radiation damage on tumor blood supply, tumor cell density, as well as antigen density and inflammatory response. These changes will be used to provide a scientific rationale for the measured radiolabeled antibody distribution from specific aim 1. In addition, this aim will attempt to quantitate changes in tumor cell response by determining the fraction of cells undergoing apoptotic cell death, (by the tunel assay), as well as changes in the fraction of cycling cells, (determined by IUdR incorporation and Ki67 and PCNA immunohistochemistry), as a surrogate of mitotic cell death. (3) To determine the therapeutic efficacy by tumor growth delay and cure after treatment with XRT and RIT alone and then in combination. Experiments will be performed in which tumors are treated with XRT followed by RIT, XRT and RIT simultaneously, and RIT prior to XRT, in order to determine the optimum combination therapy. Variations in the tumor response will be correlated with the results from aim 1 and 2. (4) To develop a radiobiological model, which determines the therapeutic effectiveness from a heterogeneous activity distribution. The model will be tested using information from the source distribution from autoradiographic data (aim 1) to predict overall tumor response measured by specific aim 3.