SPECT Imaging of PD-L1 Expression of MDA-MB-231 Tumor Xenograft Mice with 125I-labeled Monoclonal Antibody
125I-Atezolizumab was synthesized with Iodogen method for monitoring the expression level of PD-L1 in tumors.The influence of reaction time on 125I-labeling efficiency and the stability of 125I-Atezolizumab in PBS and fetal bovine serum were studied.The pharmacokinetics of 125I-Atezolizumab was evaluated in rats.Binding specificity to PD-L1 was determined using cellular uptake experiment of breast cancer cell line MDA-MB-231 in vitro and SPECT imaging of mice bearing MDA-MB-231 xenografts in vivo.The results indicated that the labeling yield of 125I-Atezolizumab was over 98%after 5 minutes reaction at room temperature.The radiochemical purity was more than 90%after 48 h incubation in PBS and fetal bovine serum.The elimination half-life of 125I-Atezolizumab in rats was(12.1±1.9)h.The immunological activity of 125I-Atezolizumab was well maintained(IF=52%)and high affinity was demonstrated in breast cancer cell line.SPECT/CT imaging of MDA-MB-231 tumor-bearing mice showed high radioactivity uptake in the tumor.Tumor uptake of 125I-Atezolizumab was blocked in the presence of Atezolizumab,confirming target specificity.The preliminary results suggested that 125I-Atezolizumab exhibited specificity for PD-L1 imaging using a simple and efficient labeling method,and demonstrated relatively good in vitro stability.It is potential to monitor the expression levels of PD-L1 in tumors by 125I-Atezolizumab SPECT imaging and is worthy of further research.
programmed death protein ligand 1(PD-L1)125I-labeling125I-AtezolizumabSPECT/CT
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