新型αvβ3和Neuropilin-1双靶点正电子成像探针18F-FAl-NOTA-RGD-ATWLPPR用于脑胶质瘤的PET显像研究

Imaging of glioma with an integrin αvβ3 and neuropilin-1 dual-targeted PET probe ^18F-FAI-NOTA- RGD-ATWLPPR

目的 构建可靶向αvβ3和血管内皮生长因子受体Neuropilin-1（NRP-1）双受体的正电子成像探针，并验证双靶点融合肽探针较之单靶点探针的优越性。方法 采用^18F-氟化铝（^18F-FAl）配合物的方法实现分子探针的18F标记。在人神经胶质瘤U87MG细胞中，检测αvβ3和NRP-1的表达水平，测定分子探针精氨酸-甘氨酸-天冬氨酸（RGD）-丙氨酸-苏氨酸-色氨酸-亮氨酸-脯氨酸-脯氨酸-精氨酸（ATWLPPR）与αvβ3/NRP-1的受体-配体亲和力。在U87MG荷瘤裸鼠模型中，测定18F标记RGD-ATWLPPR的体内肿瘤micro-PET显像特性，并且与其对应单体进行比较分析。采用方差分析和t检验对结果进行统计学分析。结果 αvβ3及NRP-1在U87MG肿瘤细胞、肿瘤组织及肿瘤新生血管中均有较高水平的表达。受体-配体亲和力测定的实验结果显示，^18F-FAl-NOTA-RGD-ATWLPPR双靶点融合肽与αvβ3及NRP-1的亲和力并未明显优于其单体，但融合肽在U87MG细胞中的摄取高于相应的单体肽。Micro-PET显像结果显示，融合肽较其单体肽RGD[（4.86±0.48）% ID/g vs.（3.33±0.15）% ID/g，t=10.21，P〈0.05]和ATWLPPR[（4.86±0.48）% ID/g vs.（2.28±0.41）% ID/g，t=32.16，P〈0.05]表现出了更好的显像效果，且融合肽在αvβ3、NRP-1任一受体被未标记“冷”肽阻断的情况下仍能获得肿瘤的阳性显像结果。结论 ^18F-FAl-NOTA-RGD-ATWLPPR可以灵敏地对整合素αvβ3和NRP-1中任何一个受体高表达的肿瘤进行显像，并且较其单体具有更高的肿瘤摄取，但该融合肽的受体-配体亲和力还有待进一步提高。

Objective Arg-Gly-Asp （RGD） or Ala-Thr-Trp-Leu-Pro-Pro-Arg （ATWLPPR） peptide binds specifically to integrin αvβ3 or neuropilin-1（NRP-1） receptor,respectively.In this study,a novel heterodimer peptide probe containing both RGD and ATWLPPR was designed in one molecule.The in vitro and in vivo biological behavior of the dual-targeted imaging probe RGD-ATWLPPR was compared with its corresponding counterparts.Methods 18F labeling was conducted through ^18F-FAl approach.In the integrin αvβ3-positive U87MG human glioma cell line,the αvβ3/NRP-1 receptor binding affinity of RGD-ATWLPPR was tested and compared with its counterparts RGD and ATWLPPR.The tumor uptake and distribution pattern of ^18F-labeled RGD-ATWLPPR through PET imaging was evaluated and compared with those of RGD and ATWLPPR.The means were compared using one-way ANOVA and t test.Results Both integrin αvβ3 and NRP-1 showed high expression in U87MG glioma cells and tumor tissues.RGD-ATWLPPR exhibited similar in vitro receptor binding affinity to those of RGD and ATWLPPR.Based on the PET imaging study,^18F-labeled RGD-ATWLPPR （denoted as ^18F-FAl-NOTA-RGD-ATWLPPR） demonstrated significantly higher tumor uptake than RGD[（4.86±0.48）% ID/g vs.（3.33±0.15）% ID/g,t=10.21,P〈0.05]and ATWLPPR[（4.86±0.48）% ID/g vs.（2.28±0.41）% ID/g,t=32.16,P〈0.05].In the blocking study,^18F-FAl-NOTA-RGD-ATWLPPR showed positive imaging result in the presence of excess unlabeled RGD or ATWLPPR.The tumor uptake decreased to the background level when unlabeled RGD and ATWLPPR were co-injected before administration of ^18F-FAl-NOTA-RGD-ATWLPPR.Conclusions The dual-targeted PET probe ^18F-FAl-NOTA-RGD-ATWLPPR specifically binds to either integrin αvβ3 or NRP-1 receptor and could be a promising PET imaging agent for NRP-1-/αvβ3＋and NRP-1＋/αvβ3-tumors.The receptor-binding affinity of RGD-ATWLPPR must be further improved.