Targeting Infiltrating Myeloid Cells in Gastric Cancer Using a Pretargeted Imaging Strategy Based on Bio-Orthogonal Diels–Alder Click Chemistry and Comparison with 89Zr-Labeled Anti-CD11b Positron Emission Tomography Imaging
Targeting Infiltrating Myeloid Cells in Gastric Cancer Using a Pretargeted Imaging Strategy Based on Bio-Orthogonal Diels–Alder Click Chemistry and Comparison with 89Zr-Labeled Anti-CD11b Positron Emission Tomography Imaging
复制标题
使用基于生物正交 Diels 和 Alder Click 化学的预靶向成像策略靶向胃癌中的浸润性骨髓细胞，并与 89Zr 标记的抗 CD11b 正电子发射断层扫描成像进行比较
DOI：
10.1021/acs.molpharmaceut.1c00745
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发表时间：
2021
影响因子：
4.9
通讯作者：
Dengfeng Cheng
中科院分区：
文献类型：
--
作者：
Yingying Zhang;Qingyu Lin;Tingting Wang;Dai Shi;Zhequan Fu;Zhan Si;Zhan Xu;Yuan Cheng;Hongcheng Shi;Dengfeng Cheng
胃癌是世界范围内常见的恶性肿瘤，发病率和死亡率都很高.因此，早期准确诊断胃癌是改善预后的关键。肿瘤相关髓系细胞浸润肿瘤微环境（TME），并可在肿瘤早期产生免疫抑制作用。表面整合素受体CD 11b广泛表达于骨髓细胞的特定亚群，具有高丰度、高特异性和靶向免疫治疗潜力大的特点。本研究采用89 Zr-DFO-anti-CD 11b和预靶向显像（68 Ga-NOTA-polypeptide-PEG 11-Tz/anti-CD 11b-TCO）两种抗CD 11b标记策略，评价其在胃癌早期诊断中的价值，并证实预靶向策略在胃癌诊断中的优势。合成了预靶向分子探针68 Ga-NOTA-多肽-PEG 11-Tz。体外评价了Tz-放射性配体与CD 11b的结合亲和力，并进行了体内血液药代动力学试验。此外，将抗CD 11b抗体与对异硫氰酸根合苄基去铁胺（SCN-DFO）螯合剂偶联，并用锆-89进行放射性标记。采用MGC-803荷瘤小鼠模型进行生物学分布和正电子发射计算机断层成像实验，评价其对胃癌早期诊断的价值。通过对MGC-803肿瘤的组织学评价证实了CD 11b+髓样细胞浸润GC TME。成功地放射合成了68 Ga-NOTA-多肽-PEG 11-Tz，经反相高效液相色谱证实放射化学纯度大于95%。放射性配体在生理盐水和磷酸盐缓冲液中表现出良好的稳定性，与RAW264.7细胞具有良好的亲和力，并且在小鼠中具有快速的血液清除。采用预靶向方法进行的生物分布和成像实验结果显示，在预靶向间隔24、48和72 h时，肿瘤/肌肉比分别为5.17 ± 2.98、5.94 ± 1.46和4.46 ± 2.73。使用直接标记抗体（89 Zr-DFO-anti-CD 11b）的方法的实验结果表明，尽管肿瘤中有放射性蓄积，但正常组织中有较高水平的放射性蓄积。在1、24、48、72和120 h时，肿瘤/肌肉比分别为1.09 ± 0.67、1.66 ± 0.95、2.94 ± 1.24、3.64 ± 1.21和3.55 ± 1.64。本研究证实了68 Ga-NOTA-多肽-PEG 11-Tz/anti-CD 11b-TCO在胃癌诊断中的应用价值。与89 Zr-DFO-anti-CD 11b相比，预靶向策略获得的图像对比度相对提高，探针的背景积累相对较低。这些优点可以提高GC的诊断效率，并为靶向CD 11b受体的放射免疫治疗提供支持证据。
Gastric cancer (GC) is a common cancer worldwide, with high incidence and mortality rates. Therefore, early and precise diagnosis is critical to improving GC prognosis. Tumor-associated myeloid cells infiltrate the tumor microenvironment (TME) and can produce immunosuppressive effects in the early stage of the tumor. The surface integrin receptor CD11b is widely expressed in the specific subsets of myeloid cells, and it has the characteristics of high abundance, high specificity, and high potential for targeted immunotherapy. In this study, two strategies for labeling anti-CD11b, including89Zr-DFO-anti-CD11b and pretargeted imaging (68Ga-NOTA-polypeptide-PEG11-Tz/anti-CD11b-TCO), were used to evaluate the value of early diagnosis of GC and confirm the advantages of the pretargeted strategy for the diagnosis of GC. Pretargeted molecular probe68Ga-NOTA-polypeptide-PEG11-Tz was synthesized. The binding affinity of the Tz-radioligand to CD11b was evaluated in vitro, and its blood pharmacokinetic test was performed in vivo. Moreover, the anti-CD11b antibody was conjugated with a p-isothiocyanatobenzyl-desferrioxamine (SCN-DFO) chelator and radiolabeled with zirconium-89. Biodistribution and positron-emission computed tomography imaging experiments were performed in MGC-803 tumor-bearing model mice to evaluate the value of the early diagnosis of GC. Histological evaluation of MGC-803 tumors was conducted to confirm the infiltration of the GC TME with CD11b+myeloid cells.68Ga-NOTA-polypeptide-PEG11-Tz was successfully radiosynthesized, with the radiochemical purity above 95%, as confirmed by reversed-phase high-performance liquid chromatography. The radioligand showed favorable stability in normal saline and phosphate-buffered saline, good affinity to RAW264.7 cells, and rapid blood clearance in mice. The results of biodistribution and imaging experiments using the pretargeted method showed that the tumor/muscle ratios were 5.17 ± 2.98, 5.94 ± 1.46, and 4.46 ± 2.73 at the pretargeting intervals of 24, 48, and 72 h, respectively. The experimental results using the method of the directly labeling antibody (89Zr-DFO-anti-CD11b) showed that, despite radioactive accumulation in the tumor, there was a higher level of radioactive accumulation in normal tissues. The tumor/muscle ratios were 1.09 ± 0.67, 1.66 ± 0.95, 2.94 ± 1.24, 3.64 ± 1.21, and 3.55 ± 1.64 at 1, 24, 48, 72, and 120 h. The current research proved the value of68Ga-NOTA-polypeptide-PEG11-Tz/anti-CD11b-TCO in the diagnosis of GC using the pretargeted strategy. Compared to89Zr-DFO-anti-CD11b, the image contrast achieved by the pretargeted strategy was relatively improved, and the background accumulation of the probe was relatively low. These advantages can improve the diagnostic efficiency for GC and provide supporting evidence for radioimmunotherapy targeting CD11b receptors.