肿瘤组织中细胞间粘附分子-1表达的PET/近红外荧光跨模态靶向成像表征

Dual-modality PET and optical imaging of intercellular adhesion molecule 1 in pancreatic cancer

目的验证基于双标记细胞间粘附分子-1(ICAM-1)单抗示踪剂,进行胰腺癌组织中ICAM-1的正电子发射断层(PET)/近红外荧光(NIRF)跨模态靶向成像的可行性。方法采用流式细胞术测定2种胰腺癌细胞系BxPC-3、MIA PaCa的ICAM-1表达水平。通过生物耦联和配位反应制备NIRF荧光团和[^(89)Z]锆核素双标记示踪剂。在上述细胞系构建的裸鼠皮下移植瘤模型(简称模型鼠)中,测试示踪剂的特异性、跨模态成像性能和生物分布特性;尝试在BxPC-3模型鼠中进行解剖前/后离体组织器官NIRF光学成像。最后采用组织病理学方法确认ICAM-1在移植瘤组织中的分布。结果BxPC-3与MIAPaCa细胞系的ICAM-1表达水平有显著差异(P<0.05)。PET/NIRF跨模态成像和放射性生物分布实验显示,在2种模型鼠中,肿瘤的示踪剂摄取峰值的差异也有统计学意义(P<0.05)。PET/NIRF成像所显示的肿瘤位置相互吻合。解剖切除瘤体前后,荧光信号随瘤体转移,周围组织几乎无残留信号。免疫组织化学染色显示,这2种移植瘤组织的ICAM-1表达水平差异与其示踪剂浓聚水平差异正相关(P<0.05)。结论本研究确认了以ICAM-1为靶标的双标记单抗示踪剂,用于胰腺癌组织临床前靶向跨模态成像是可行的,这为同时实现肿瘤活体全身成像和肿瘤组织原位可视化提供了例证,揭示了基于ICAM-1靶向成像的病灶检测、手术导航等临床转化应用的潜力。

Objective To validate the feasibility of intermodal imaging of pancreatic cancer tissue employing positron emission tomography(PET)and near-infrared fluorescent(NIRF)imaging,based on a dual-labeled monoclonal ICAM-1 antibody tracer.Methods ICAM-1 expression in pancreatic cancer cell lines(BxPC-3 and MIA PaCa)was determined via flow cytometry.NIRF fluorophore and zirconium-89 Dual-labeled tracer was synthesized via bio-conjugation reaction and coordination chemistry.In the mouse models bearing subcutaneous tumors established using the aforementioned cell lines,we assessed the specificity,performance of intermodal imaging,and radioactive bio-distribution of the tracer.The in situ ex vivo NIRF imaging of resected tumor and major organs at pre-/post-dissection timepoints in BxPC-3 subcutaneous mouse model was also performed.The expression of ICAM-1 in the tissue of transplanted tumors was validated via pathohistochemistry.Results Significant discrepancy in the expression level of ICAM-1 was found between BxPC-3 and MIA PaCa cell lines.The results of PET/NIRF intermodal imaging and radioactive bio-distribution indicated that peak values of tracer uptake in tumors were notably different between the two mouse models of pancreatic cancer(P<0.05).There was strong evidence for the optimal avidity and specificity of the tracer against ICAM-1.PET and NIRF imaging colocalized the tumor,and the NIRF signal translocated with resected tumor nodules,leaving negligible residual signal in remaining surrounding tissues.Immunohistochemical staining showed that the difference in the expression of ICAM-1 in tumor tissues derived from the two cell lines was positively correlated with the contrast of tracer deposition in tumors between the two mouse models.Conclusion We confirmed that the preclinical intermodal imaging of malignant tissues in pancreatic cancer using dual-labeled monoclonal antibody targeting ICAM-1 is feasible.This attempt exemplifies the simultaneous implementation of whole-body in vivo focal imaging and in situ visualization of tumor tissue.It implies the potential of ICAM-1-targeted imaging in clinical applications involving lesion detection and intraoperative navigation.