Targeting CD133 for imaging and therapy in prostate cancer

摘要 侵袭性变异型前列腺癌（AVPC）发生在第二代前列腺癌治疗失败的男性中 抗雄激素治疗不受雄激素受体信号传导轴的驱动，有效的治疗选择不 AVPC存在，迫切需要新的创新疗法。小说发展的关键 治疗的最大优势是能够准确地成像AVPC患者的疾病负担。一种成像模态， 检测骨和内脏转移与AVPC不存在。这个项目的总体目标是 项目是开发正电子发射断层扫描（PET）成像探针和放射免疫治疗（RIT）试剂 通过用新的抗体构建体靶向新鉴定的AVPC特有的细胞表面抗原。使用人 抗体噬菌体展示，我们最近确定了一个单链可变片段（scFv），特异性结合 跨膜蛋白CD 133的肽骨架上的糖基化非依赖性表位。经常 尽管CD 133被表征为癌症干细胞标志物，但其在癌症中的功能尚不清楚。所有市 可用的CD 133抗体识别糖基化依赖性表位，这些表位在细胞之间变化， 细胞周期的不同阶段。这些抗体的免疫组织化学（IHC）产生不一致的结果 和染色质量差;从而导致我们对CD 133的了解有限。我们的针对CD 133的scFv，称为A10， 转化为全长免疫球蛋白（IA 10），用于对患者活检和组织进行IHC分析 微阵列值得注意的是，我们发现CD 133仅在男性的骨和内脏转移中表达， 开发了AVPC。作为单光子发射计算机断层扫描成像剂，IA 10能够 体内成像CD 133表达。在生物分布研究中，IA 10和较小的微抗体构建体版本 （MA 10）两者均显示高肿瘤摄取和有利的药代动力学。高肿瘤摄取的 A10抗体构建体是其通过表达CD 133的细胞快速内化的直接结果， 它们是纵向PET成像和RIT的理想候选者。在本提案中，我们将评估IA 10的效用 和MA 10作为PET探针在AVPC的细胞系来源的和患者来源的异种移植物模型中， 作为药效学生物标志物（目的1），然后确定用放射性标记的IA 10的治疗潜力 177 Lu用于皮下和转移性异种移植物中的β颗粒RIT，使用单次和分次剂量（Aim 2）。我们的初步数据有力地表明，我们已经为AVPC开发了具有以下功能的有效工具： 可能导致疾病治疗方式的巨大转变。

ABSTRACT Aggressive variant prostate cancer (AVPC) arises in men who have failed treatment with second-generation anti-androgen therapy. Not driven by the androgen receptor-signaling axis, effective treatment options do not exist for AVPC and new, innovative therapies are urgently needed. Critical to the development of novel therapeutics is the ability to accurately image disease burden in AVPC patients. An imaging modality that can detect both the bone and visceral metastases associated with AVPC does not exist. The overall goal of this project is to develop positron emission tomography (PET) imaging probes and radioimmunotherapy (RIT) agents by targeting a newly identified cell-surface antigen unique to AVPC with novel antibody constructs. Using human antibody phage display, we recently identified a single chain variable fragment (scFv) that specifically bound to a glycosylation-independent epitope on the peptide backbone of the transmembrane protein CD133. Often characterized as a cancer stem cell marker, the function of CD133 in cancer is unknown. All commercially available antibodies for CD133 recognize glycosylation-dependent epitopes that vary between cells and at different stages of the cell cycle. Immunohistochemistry (IHC) with these antibodies yield inconsistent results and poor staining quality; thus contributing to our limited knowledge of CD133. Our scFv for CD133, termed A10, was converted into a full-length immunoglobulin (IA10) for IHC analysis on patient biopsies and tissue microarrays. Remarkably, we found that CD133 was only expressed in bone and visceral metastases of men who had developed AVPC. As a single-photon emission computed tomography imaging agent, IA10 was able to image CD133 expression in vivo. In biodistribution studies, IA10 and a smaller minibody construct version (MA10) both demonstrated high tumor uptake and favorable pharmacokinetics. The high tumor uptake of the A10 antibody constructs was the direct result of their rapid internalization by CD133-expressing cells making them ideal candidates for longitudinal PET imaging and RIT. In this proposal, we will evaluate the utility of IA10 and MA10 as PET probes in cell line-derived and patient-derived xenograft models of AVPC and evaluate CD133 as a pharmacodynamic biomarker (Aim 1) then determine the therapeutic potential of IA10 radiolabeled with 177Lu for beta particle RIT in subcutaneous and metastatic xenografts using single and fractionated doses (Aim 2). Our preliminary data strongly suggest that we have developed potent tools for AVPC that possess the potential to result in a dramatic shift in how the disease is treated.