China Oncology ›› 2023, Vol. 33 ›› Issue (4): 354-360.doi: 10.19401/j.cnki.1007-3639.2023.04.005

• Article • Previous Articles     Next Articles

The synthesis of a novel molecular imaging probe 68Ga-DOTA-PDL1P and application in mouse model of melanoma

YANG Ziyi1,2,3,4,5(), LI Panli1,2,3,4,5, GU Bingxin1,2,3,4,5, LIU Cheng1,2,3,4,5, SONG Shaoli1,2,3,4,5, XU Xiaoping1,2,3,4,5()   

  1. 1. Department of Nuclear Medicine, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
    2. Center for Biomedical Imaging, Fudan University, Shanghai 200032, China
    3. Shanghai Engineering Research Center of Molecular Imaging Probes, Shanghai 200032, China
    4. Department of Nuclear Medicine, Shanghai Proton and Heavy Ion Center, Shanghai, 201321, China
    5. Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Fudan University, Shanghai 200433, China
  • Received:2022-09-05 Revised:2023-03-08 Online:2023-04-30 Published:2023-05-15
  • Contact: XU Xiaoping

Abstract:

Background and purpose: The immunogenic drugs represented by programmed cell death 1 (PD-1) and programmed death ligand-1 (PD-L1) have achieved great success in clinic. However, with the development of clinical application, the overall effective rate varies greatly. At present, detection of the expression of PD-1/PD-L1 before the start of tumor treatment is an important basis for clinical medication. However, the current detection method of PD-L1 expression requires the acquisition of patient specimens, which is traumatic. Therefore, there is an urgent need to develop a noninvasive method to detect PD-L1 expression in vivo. This study innovatively designed and synthesized a new positron emission tomography (PET) imaging agent targeting PD-L1 polypeptide 68Ga-DOTA-PDL1P. In this study, the labeling rate, radiochemical purity and stability of 68Ga-DOTA-PDL1P were evaluated for quality control. And the application was evaluated in the mouse model of melanoma in order to obtain a promising 68Ga-DOTA-PDL1P immune PET probe. Methods: Gallium-68 (68Ga) was used to label DOTA-PDL1P, and its radiochemical purity and stability were evaluated by quality control. To evaluate its specific targeting performance, the cell uptake and blocking experiments were carried out in murine melanoma B16-F10 cells. The biodistribution experiment was performed in B16-F10 tumor-bearing mice to analyze the metabolism of the PET imaging agent in vivo. The Tumor uptake of 68Ga-DOTA-PDL1P in B16-F10 tumor-bearing mice was observed by PET/CT imaging, and the tumor/muscle (T/M) ratio was semi-quantitatively analyzed. In addition, radioautography was performed to further analyze the tumor uptake of 68Ga-DOTA-PDL1P probe. Tumor cell proportion score (TPS) and combined positive score (CPS) were used to analyze the immunohistochemical staining results to evaluate the expression of PD-L1 in tumor tissues. Results: The labeling efficiency and radiochemical purity of 68Ga-DOTA-PDL1P were more than 99%, and the radiochemical purity of 68Ga-DOTA-PDL1P was more than 90% after 3 h of incubation in PBS and fetal bovine serum. Cellular uptake results showed that 68Ga-DOTA-PDL1P could be specifically taken up by B16-F10 cells, and the specific uptake could be blocked by PD-L1P peptide competitive binding. Biodistribution assay showed that 68Ga-DOTA-PDL1P was mainly excreted through the urinary system. The results of microPET/CT imaging of tumor-bearing mice showed a high uptake of 68Ga-DOTA-PDL1P in tumor tissues, and the T/M ratio was 6.7. The autoradiography results confirmed that 68Ga-DOTA-PDL1P high uptake in the tumor was consistent with the PD-L1 positive area of immunohistochemical staining, which proved that 68Ga-DOTA-PDL1P could specifically bind to PD-L1 positive malignant tumor cells. Conclusion: The novel 68Ga-DOTA-PDL1P PET imaging agent synthesized in this study has good stability and can specifically target PD-L1 positive tumor cells, which is a promising new immune PET probe targeting PD-L1 protein.

Key words: PD-L1, Malignant melanoma, 68Ga, PET/CT

CLC Number: