针对 MMP-14 进行双 PET 和荧光成像，用于临床前模型中的脑胶质瘤。
Targeting MMP-14 for dual PET and fluorescence imaging of glioma in preclinical models.
机构信息
Department of Neurosurgery, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
Departments of Radiology and Chemistry, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, CA, 94305, USA.
出版信息
Eur J Nucl Med Mol Imaging. 2020 Jun;47(6):1412-1426. doi: 10.1007/s00259-019-04607-x. Epub 2019 Nov 26.
PURPOSE
There is a clinical need for agents that target glioma cells for non-invasive and intraoperative imaging to guide therapeutic intervention and improve the prognosis of glioma. Matrix metalloproteinase (MMP)-14 is overexpressed in glioma with negligible expression in normal brain, presenting MMP-14 as an attractive biomarker for imaging glioma. In this study, we designed a peptide probe containing a near-infrared fluorescence (NIRF) dye/quencher pair, a positron emission tomography (PET) radionuclide, and a moiety with high affinity to MMP-14. This novel substrate-binding peptide allows dual modality imaging of glioma only after cleavage by MMP-14 to activate the quenched NIRF signal, enhancing probe specificity and imaging contrast.
METHODS
MMP-14 expression and activity in human glioma tissues and cells were measured in vitro by immunofluorescence and gel zymography. Cleavage of the novel substrate and substrate-binding peptides by glioma cells in vitro and glioma xenograft tumors in vivo was determined by NIRF imaging. Biodistribution of the radiolabeled MMP-14-binding peptide or substrate-binding peptide was determined in mice bearing orthotopic patient-derived xenograft (PDX) glioma tumors by PET imaging.
RESULTS
Glioma cells with MMP-14 activity showed activation and retention of NIRF signal from the cleaved peptides. Resected mouse brains with PDX glioma tumors showed tumor-to-background NIRF ratios of 7.6-11.1 at 4 h after i.v. injection of the peptides. PET/CT images showed localization of activity in orthotopic PDX tumors after i.v. injection of Ga-binding peptide or Cu-substrate-binding peptide; uptake of the radiolabeled peptides in tumors was significantly reduced (p < 0.05) by blocking with the non-labeled-binding peptide. PET and NIRF signals correlated linearly in the orthotopic PDX tumors. Immunohistochemistry showed co-localization of MMP-14 expression and NIRF signal in the resected tumors.
CONCLUSIONS
The novel MMP-14 substrate-binding peptide enabled PET/NIRF imaging of glioma models in mice, warranting future image-guided resection studies with the probe in preclinical glioma models.
目的
针对神经胶质瘤细胞，开发非侵入性和术中成像的靶向试剂，以指导治疗干预并改善神经胶质瘤的预后，这具有重要的临床意义。基质金属蛋白酶（MMP）-14 在神经胶质瘤中过度表达，在正常脑组织中几乎不表达，因此 MMP-14 作为一种有吸引力的神经胶质瘤成像生物标志物。在这项研究中，我们设计了一种含有近红外荧光（NIRF）染料/猝灭剂对、正电子发射断层扫描（PET）放射性核素和与 MMP-14 具有高亲和力的部分的肽探针。这种新型基质结合肽只有在 MMP-14 切割后才能激活被猝灭的 NIRF 信号，从而实现双重模态成像，从而提高探针的特异性和成像对比度。
方法
通过免疫荧光和凝胶酶谱法在体外测量人神经胶质瘤组织和细胞中的 MMP-14 表达和活性。通过 NIRF 成像测定新型基质和基质结合肽在体外培养的神经胶质瘤细胞和体内神经胶质瘤异种移植瘤中的切割情况。通过 PET 成像测定携带原位患者来源异种移植（PDX）神经胶质瘤肿瘤的小鼠中放射性标记的 MMP-14 结合肽或基质结合肽的生物分布。
结果
具有 MMP-14 活性的神经胶质瘤细胞显示出从切割肽中激活和保留 NIRF 信号。静脉注射肽后 4 小时，切除的携带 PDX 神经胶质瘤的小鼠大脑显示出肿瘤与背景的 NIRF 比值为 7.6-11.1。静脉注射 Ga 结合肽或 Cu 基质结合肽后，PET/CT 图像显示出在原位 PDX 肿瘤中的活性定位；用未标记的结合肽阻断后，放射性标记肽在肿瘤中的摄取显著减少（p <0.05）。在原位 PDX 肿瘤中，PET 和 NIRF 信号呈线性相关。免疫组织化学显示，在切除的肿瘤中 MMP-14 表达和 NIRF 信号的共定位。
结论
新型 MMP-14 基质结合肽可实现小鼠神经胶质瘤模型的 PET/NIRF 成像，为该探针在临床前神经胶质瘤模型中的图像引导切除研究提供了依据。
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