COMBINED RADIOIMMUNOTHERAPY WITH RADIOTHERAPY

这项拨款申请审查了放射性标记抗体异质性是放射免疫治疗（RIT）失败的主要原因的假设。 它提出，这一限制可以克服的RIT与外部束放射治疗（XRT）的组合。 本研究将研究XRT与RIT之间的相互作用，并确定这两种方式的最佳组合，以获得最大的肿瘤疗效。 将使用完整的A33 IgG单克隆抗体作为靶向剂及其单链高变sFv片段，使用鼠SW 1222结肠直肠异种移植模型系统来检验该假设。 有四个具体目标：（1）荧光板放射自显影法测定放射性标记的A33 IgG在SW 1222肿瘤异种移植系统中的三维微分布。 通过同时给予单链高变片段sFv A33和亲本A33 IgG，并在预外照射后，研究分布对抗体/抗原摩尔比、分子量的影响的依赖性。 (2)确定放射组织损伤如何促进/阻碍抗体渗透到肿瘤中。 这将通过常规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。这些变更将用于为特定目的1中测定的放射性标记抗体分布提供科学依据。 此外，该目标将试图通过确定经历凋亡性细胞死亡的细胞的分数（通过tunel测定）以及作为有丝分裂细胞死亡的替代物的循环细胞的分数的变化（通过IUdR掺入和Ki 67和PCNA免疫组织化学测定）来定量肿瘤细胞应答的变化。 (3)通过XRT和RIT单独或联合治疗后肿瘤生长延迟和治愈来确定疗效。将进行实验，其中肿瘤用XRT随后RIT、XRT和RIT同时治疗，以及RIT在XRT之前治疗，以确定最佳组合疗法。肿瘤缓解的变化将与目标1和2的结果相关。 (4)建立一个放射生物学模型，根据放射性分布的不均匀性确定治疗效果。 将使用来自放射自显影数据（目标1）的源分布信息对模型进行检验，以预测特定目标3测量的总体肿瘤缓解。

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.