Department of Nuclear Medicine, Shanghai Changhai Hospital, Shanghai, 200433, China.
Department of Radiology, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Hubei, 441021, China.
Biochem Biophys Res Commun. 2023 Sep 17;673:23-28. doi: 10.1016/j.bbrc.2023.06.059. Epub 2023 Jun 19.
This study aimed to establish the radio-immune imaging protocol on the basis of Avidin/Biotin system. The programmed death-ligand 1 (PD-L1) antibody (Atezolizumab) was employed as the primary molecule in targeting PD-L1, and the two-step strategy, consisting of the first injection of Avidin-conjugated PD-L1 monoclonal antibody (Atezolizumab) and the second injection of 7.4 MBq Ga-Biotin with a 60 h interval, was then verified on the colon cancer-bearing mice. PET imaging was performed at 30, 90, 180 min to measure the standard uptake value and tumor to liver ratios. Cellular binding experiments and in vivo distribution showed that the conjugation of Avidin did not affect the affinity of Atezolizumab to PD-L1 antigen. Biotin was radio-labeled with Ga with radiolabeling efficiency of 70.5 ± 3.5% and purification was needed to increase the radiochemical purity. For PD-L1-positive tumors, SUV was 0.38 ± 0.06 in the Avidin-Atezolizumab pre-treated mice at 90 min; the tumor/liver ratios of pre-targeting group were 1.06 ± 0.19 and 0.97 ± 0.16 at 30 and 90 min, while the absence of pre-treatment of Avidin was of the lower ratios as 0.88 ± 0.01 and 0.54 ± 0.11 when Ga-Biotin served as the radiopharmaceutical as well. In conclusion, pre-targeting immunoPET strategy can elevate the target-to-nontarget ratio, decrease the blood background and shorten the interval between injection of radiopharmaceuticals and PET scan, providing a highly PD-L1-specific and sensitive imaging method for the detection of tumorous immune micro-environment.
本研究旨在基于亲和素/生物素系统建立放射免疫成像方案。程序性死亡配体 1（PD-L1）抗体（阿替利珠单抗）被用作靶向 PD-L1 的主要分子，然后在结肠癌荷瘤小鼠上验证了两步策略，包括第一次注射亲和素偶联的 PD-L1 单克隆抗体（阿替利珠单抗）和第二次注射 7.4 MBq Ga-生物素，间隔 60 h。在 30、90、180 min 进行 PET 成像，测量标准摄取值和肿瘤与肝脏的比值。细胞结合实验和体内分布表明，亲和素的缀合不影响阿替利珠单抗与 PD-L1 抗原的亲和力。生物素用 Ga 进行放射性标记，放射标记效率为 70.5±3.5%，需要纯化以提高放射化学纯度。对于 PD-L1 阳性肿瘤，在 90 min 时，经阿替利珠单抗预处理的小鼠中，Avidin-Atezolizumab 的 SUV 为 0.38±0.06；预靶向组的肿瘤/肝脏比值分别为 30 和 90 min 时的 1.06±0.19 和 0.97±0.16，而当 Ga-生物素作为放射性药物时，无阿替利珠单抗预处理的比值较低，分别为 0.88±0.01 和 0.54±0.11。总之，预靶向免疫 PET 策略可以提高靶标与非靶标比值，降低血液背景，并缩短放射性药物注射与 PET 扫描之间的间隔，为肿瘤免疫微环境的检测提供了一种高度特异性和敏感的成像方法。
