Preclinical study of a novel molecular probe 89Zr DFO-G4C2 for monitoring PD-1 expression levels
10.3760/cma.j.cn321828-20231019-00078
- VernacularTitle:新型分子探针 89Zr-DFO-G4C2监测PD-1表达水平的临床前研究
- Author:
Yirong ZHU
1
;
Weiwei KONG
;
Jiaxi YOU
;
Kairu NI
;
Bing ZHANG
;
Zengli LIU
;
Yizhen SHI
;
Zhihui HONG
Author Information
1. 苏州大学附属第二医院核医学科，苏州 215004
- Keywords:
Programmed cell death receptor 1;
Isotope labeling;
Zirconium;
Colorectal neoplasms;
Breast neoplasms;
Positron-emission tomography;
Mice
- From:
Chinese Journal of Nuclear Medicine and Molecular Imaging
2024;44(10):603-608
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To design and synthesize 89Zr-deferoxamine(DFO)-G4C2, a novel molecular probe targeting programmed cell death receptor 1(PD-1), and evaluate its in vivo biodistribution and microPET/CT imaging characteristics in tumor-bearing mice. Methods:DFO-G4C2 was prepared by coupling DFO with G4C2, a monoclonal antibody targeting PD-1. The affinity and binding specificity of this amalgamation were subsequently assessed through the implementation of flow cytometry and surface plasmon resonance techniques. The molecular probe 89Zr-DFO-G4C2 was achieved by labeling DFO-G4C2 with the radioisotope 89Zr, and the labeling efficiency and in vitro stability of 89Zr-DFO-G4C2 were determined. Mouse models laden with CT26 colorectal cancer cells expressing PD-1 were established, followed by in vivo biodistribution and microPET/CT imaging studies, to explore the potential clinical value of 89Zr-DFO-G4C2. Additionally, the validity of this molecular probe was verified in 4T1 breast cancer models, affirming its efficacy as an imaging tool across different tumor models. Independent-sample t test was used to analyze the data. Results:DFO-G4C2 exhibited an affinity constant KD of (0.55±0.02) μmol/L, indicating a strong binding affinity. The binding rate to mouse PD-1 protein was determined to be (61.82±8.49)%. The labeling rate of 89Zr-DFO-G4C2 reached a high level of (98.76±0.51)%. Furthermore, the labeling rates in lysate and human serum after 144 h were measured to be (93.07±2.16)% and (83.42±3.21)%, respectively. MicroPET/CT imaging of CT26 tumor-bearing mice injected with 89Zr-DFO-G4C2 showcased pronounced radioactivity uptake in the tumor tissue. At 72 h post-injection, the tumor uptake value reached (10.47±0.34) percentage activity of injection dose per gram of tissue (%ID/g). The tumor uptake observed in the blocked experimental group, wherein an excess of unlabeled antibody was administered, was significantly lower at (6.26±1.03) %ID/g in comparison to the non-blocked group ( t=6.67, P=0.003). The in vivo biodistribution results were consistent with the observed microPET/CT imaging outcomes. MicroPET/CT imaging observations in the 4T1 breast cancer bearing mouse model were analogous to those obtained from the CT26 model. Conclusion:ImmunoPET based on the 89Zr-DFO-G4C2 molecular probe can non-invasively and visually assess the PD-1 expression level of tumors in vivo, and it is expected to be a new molecular imaging technique for immunotherapy monitoring of PD-1 inhibitors.
