Abstract
1052
Objectives: Recent years, tumor immunotherapy is in full swing, especially PD1/ PDL1 checkpoint has harvested great achievements in oncotherapy. Theranostics has become as a very promising technique in precision medicine, especially in nuclear medicine for kinds of tumors management. Iodine-131 has been widely used in thyroid diseases over the past decades, what’s more, I-131 has already been widely used as convenient radionuclide for novel theranostic molecular probes preparation as its γ and β- radiation which could be used for SPECT imaging and treatment. The aim of the study was to prepare a new radioiodinated PD-L1 as imaging probe, and aim at imaging tumor in vivo by SPECT.
Methods: In order to optimize the labeling method, gradients of factors, such as Ch-T, reacting time and volume, were set. The labeled product was purified by PD10 column, and the radiochemical yields (RCY) and radiochemical purity (RCP) were evaluated by filter paper chromatography or radio high performance liquid chromatography (HPLC). To evaluate the stability of the probe, its RCP in different environments were measured at different time points. Lipid-water partition coefficient was tested. Hela and U87 cell line were implanted in axillary subcutaneous layer of Babl/C mice. The probe was injected via tail vein, and imaged mice in vivo by SPECT.
Results: The optimum labeling method was 30 μg Ch-T in 150 μl at room temperature for 3 minutes, and RCY was 68.47%±13.05% (n=11), RCP was 6.51%±1.10% with favorable stability in different environments, and its LgP was -2.51±0.39 (n=3). Results from SPECT showed excellent tumors imaging of both glioma and cervical cancer in vivo and the concentration of probe in tumors kept for a long time.
Conclusions: The probe of I-131-PD-L1 was successfully prepared with high stabilities in different environments. The probe has been certificated at oncotargeting imaging, in glioma and cervical cancer, by SPECT in vivo. Keywords: PD-L1; Iodine-131; Molecular probe; Molecular imaging; Tumor immunology