Song In Ho, Lee Tae Sup, Park Yong Serk, Lee Jin Sook, Lee Byung Chul, Moon Byung Seok, An Gwang Il, Lee Hae Won, Kim Kwang Il, Lee Yong Jin, Kang Joo Hyun, Lim Sang Moo
Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences (KIRAMS), Seoul, South Korea Department of Biomedical Laboratory Science, Yonsei University, Wonju, South Korea.
Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences (KIRAMS), Seoul, South Korea
J Nucl Med. 2016 Jul;57(7):1105-11. doi: 10.2967/jnumed.115.167155. Epub 2016 Feb 25.
Immuno-PET provides valuable information about tumor location, phenotype, susceptibility to therapy, and treatment response, especially to targeted radioimmunotherapy. In this study, we prepared antiepidermal growth factor receptor (EGFR) antibody via identical chelator, 3,6,9,15-tetraazabicyclo[9.3.1]-pentadeca-1(15),11,13-trience-3,6,9,-triacetic acid (PCTA), labeled with (64)Cu or (177)Lu to evaluate the EGFR expression levels using immuno-PET and the feasibility of radioimmunotherapy in an esophageal squamous cell carcinoma (ESCC) model.
Cetuximab was conjugated with p-SCN-Bn-PCTA and radiolabeled with (64)Cu or (177)Lu. In vitro EGFR expression levels were determined and compared using flow cytometry and cell binding assay. In vivo EGFR expression levels were evaluated via immuno-PET imaging of (64)Cu-cetuximab and biodistribution analysis. Micro-SPECT/CT imaging, biodistribution, and radioimmunotherapy studies of (177)Lu-cetuximab were performed in the ESCC model. Therapeutic responses were monitored using (18)F-FDG PET and immunohistochemical staining.
(64)Cu- or (177)Lu-labeled antibodies showed high radiolabeling yield (>98%), stability (>90%), and favorable immunoreactivity. In vitro EGFR status measured by cell binding assay was correlated with the flow cytometry data. Immuno-PET, micro-SPECT/CT, and biodistribution demonstrated specific uptake in ESCC tumors depending on the EGFR expression levels. Tumor accumulation of (64)Cu- and (177)Lu-cetuximab was peaked at 48 and 120 h, respectively. Radioimmunotherapy with (177)Lu-cetuximab showed significant inhibition of tumor growth (P < 0.01) and marked reduction of (18)F-FDG SUV compared with that of control (P < 0.05). Terminal deoxynucleotidyl transferase dUTP nick-end labeling positivity and Ki-67 staining indices increased and decreased, respectively, in the radioimmunotherapy group compared with other groups (P < 0.01).
(64)Cu-cetuximab immuno-PET represented EGFR expression levels in ESCC tumors, and (177)Lu-cetuximab radioimmunotherapy effectively inhibited the tumor growth. The diagnostic and therapeutic convergence radiopharmaceutical (64)Cu-/(177)Lu-PCTA-cetuximab may be useful as a diagnostic tool in patient selection and a potent radioimmunotherapy agent in EGFR-positive ESCC tumors.
免疫正电子发射断层扫描（Immuno-PET）可提供有关肿瘤位置、表型、治疗敏感性和治疗反应的有价值信息，尤其是对于靶向放射免疫治疗。在本研究中，我们通过相同的螯合剂3,6,9,15-四氮杂双环[9.3.1]-十五碳-1(15),11,13-三烯-3,6,9-三乙酸（PCTA）制备抗表皮生长因子受体（EGFR）抗体，并用（64）Cu或（177）Lu进行标记，以使用免疫正电子发射断层扫描评估EGFR表达水平，并在食管鳞状细胞癌（ESCC）模型中评估放射免疫治疗的可行性。
西妥昔单抗与p-SCN-Bn-PCTA偶联，并用（64）Cu或（177）Lu进行放射性标记。使用流式细胞术和细胞结合试验测定并比较体外EGFR表达水平。通过（64）Cu-西妥昔单抗的免疫正电子发射断层扫描成像和生物分布分析评估体内EGFR表达水平。在ESCC模型中进行（177）Lu-西妥昔单抗的微单光子发射计算机断层扫描/计算机断层扫描（Micro-SPECT/CT）成像、生物分布和放射免疫治疗研究。使用（18）F-氟代脱氧葡萄糖（FDG）正电子发射断层扫描和免疫组织化学染色监测治疗反应。
（64）Cu或（177）Lu标记的抗体显示出高放射性标记产率（>98%）、稳定性（>90%）和良好的免疫反应性。通过细胞结合试验测量的体外EGFR状态与流式细胞术数据相关。免疫正电子发射断层扫描、微单光子发射计算机断层扫描/计算机断层扫描和生物分布显示，根据EGFR表达水平，ESCC肿瘤中有特异性摄取。（64）Cu-和（177）Lu-西妥昔单抗的肿瘤蓄积分别在48小时和120小时达到峰值。与对照组相比，（177）Lu-西妥昔单抗放射免疫治疗显示出对肿瘤生长的显著抑制（P<0.01）和（18）F-FDG标准摄取值（SUV）的显著降低（P<0.05）。与其他组相比，放射免疫治疗组的末端脱氧核苷酸转移酶dUTP缺口末端标记阳性率和Ki-67染色指数分别升高和降低（P<0.01）。
（64）Cu-西妥昔单抗免疫正电子发射断层扫描代表了ESCC肿瘤中的EGFR表达水平，（177）Lu-西妥昔单抗放射免疫治疗有效抑制了肿瘤生长。诊断和治疗一体化放射性药物（64）Cu/（177）Lu-PCTA-西妥昔单抗可用作患者选择的诊断工具以及EGFR阳性ESCC肿瘤的有效放射免疫治疗药物。
