可跨越血脑屏障的磁共振/光学双模态靶向分子探针的构建及其在乳腺癌脑转移瘤早期诊断中的应用研究

The early diagnosis and treatment of breast cancer brain metastases (BCBM) have become a difficult clinical problem due to the largely unknown underlying mechanisms of BCBM and the existence of blood-brain barrier (BBB). Screening novel tumor biomarkers and development of molecular imaging probes which are BBB permeable and BCBM-targeted will be of great importance in studying the development and progression mechanisms of BCBM from the perspective of molecular imaging, detecting the early BCBM and monitoring the therapeutic effects. Some other studies in literature and preliminary results of the present study have found that EGFR may play a critical role in BCBM development. Therefore, the present study aim to develop an BCBM-targeted dual-modality molecular imaging probe in which Gd3+-DOTA T1-weighted MR reporters, Cy5.5 near-infrared fluorescence imaging reporters, BCBM cell targeted anti-EGFR scFv fragments, and BBB permeable Angiopep2 peptides are labeled on the PAMAM-G5 dendrimer, to confirm the high specificity, efficiency and safety of the molecular probe through in vitro and in vivo studies, to establish an in vivo imaging evaluation system for accurate detection of early BCBM, and to clarify the mechanisms of EGFR overexpression in regulating BCBM development and progression by using molecular imaging approach.

由于发病机制不明及血脑屏障的存在，使乳腺癌脑转移瘤的早期诊断和治疗成为临床亟待解决的难题。筛选新的肿瘤分子标记物，开发能有效跨越血脑屏障并具有肿瘤靶向性的分子成像探针，对从分子影像学角度深入研究乳腺癌脑转移发生发展机制，并对其进行早期诊断及疗效监测具有重要意义。文献报道及我们前期工作发现EGFR在乳腺癌脑转移形成过程中发挥重要作用。本项目拟合成T1加权磁性基团、近红外荧光基团、Angiopep2多肽和抗EGFR scFv标记的能有效跨越血脑屏障的双模态靶向分子成像探针，利用Angiopep2介导探针跨越血脑屏障及抗EGFR scFv介导探针靶向结合肿瘤细胞表达的EGFR，采用MR及近红外荧光成像方法，在体外细胞实验和体内动物实验证实此探针的特异性、高效性和安全性，建立活体评估乳腺癌脑转移瘤的影像评价体系，实现其早期准确诊断，并运用分子影像手段阐明EGFR在乳腺癌脑转移发生发展中的新机制。

由于发病机制不明及血脑屏障的存在，使乳腺癌脑转移瘤的早期诊断和治疗成为临床亟待解决的难题。筛选新的肿瘤分子标记物，开发能有效跨越血脑屏障并具有肿瘤靶向性的分子成像探针，对从分子影像学角度深入研究乳腺癌脑转移发生发展机制，并对其进行早期诊断及疗效监测具有重要意义。文献报道及我们前期工作发现EGFR 在乳腺癌脑转移形成过程中发挥重要作用。本项目成功构建了T1 加权磁性基团、近红外荧光基团、Angiopep2多肽和GE11多肽组成的能有效跨越血脑屏障的双模态靶向EGFR分子成像探针，利用Angiopep2介导探针跨越血脑屏障及GE11多肽介导探针靶向结合肿瘤细胞表达的EGFR，采用MR 及近红外荧光成像方法，在体外细胞实验和体内动物实验证实了此探针的特异性、高效性和安全性，结果显示探针可特异性与乳腺癌脑转移细胞结合，并可在活体跨越血脑屏障，靶向至乳腺癌脑转移瘤进行活体MR及光学双模态成像，且探针对细胞的增殖活性及迁移能力无明显影响。本项目建立了活体评估乳腺癌脑转移瘤的影像评价体系，为实现其早期准确诊断，并运用分子影像手段阐明EGFR 在乳腺癌脑转移发生发展机制奠定了实验基础。