Biodistribution and imaging of 131I-labelled hepatoma aptamer in tumor-bearing nude mice

Abstract

Objective To investigate the feasibility of 131I-labeled hepatoma aptamer JHIT2 (131I-JHIT2) as a novel molecular probe for hepatoma-targeted imaging. Methods The 131I-JHIT2 was prepared by Iodogen method. The labeling rate and radiochemical purity were measured by paper chromatography. The radiochemical purity of 131I-JHIT2 was detected in different solutions at different time points. The radioactivity count of 131I-JHIT2 after combining with human hepatoma HepG2 and normal liver cell L02 was measured by gamma counter. The HepG2 tumor-bearing nude mice were sacrificed at different time points after caudal venous injection of approximately 0.74 MBq 131I-JHIT2. The percentage of radioactivity uptake value and tumor/muscle (T/M) radioactivity ratio per 1 g tissues of each organ were measured and calculated. Single-photon emission computed tomography (SPECT)-CT imaging was performed after caudal venous injection of approximately 9.25 MBq 131I-JHIT2 in tumor-bearing nude mice. The tumor/non-tumor (T/NT) ratio was observed and measured at different time points. The radioactive count was statistically compared between two types of cells by t test. Results The labeling rate of 131I-JHIT2 was (67.8±0.5)%, and the radiochemical purity after purification was (91.4±1.1)%. The radiochemical purity of 131I-JHIT2 in PBS or normal saline at room temperature for 24 h was both above 80%. After 131I-JHIT2 combining with two types of cells, the radioactive count of HepG2 cells was (415±9) CPM, significantly higher than (288±7) CPM of L02 cells (t=15.3, P<0.05). At 30 min and 2 h after caudal venous injection of 131I-JHIT2, the percentage of radioactivity uptake value per 1 g tumor tissue in tumor-bearing mice was (4.17±2.83) and (2.22±0.64) %ID/g, and the T/M ratio was 2.01±1.15 and 2.07±0.82. SPECT-CT imaging demonstrated that radioactive uptake was observed at the tumor site in tumor-bearing nude mice and the T/NT ratio was 2.63 at 30 min after 131I-JHIT2 injection. The radioactivity decreased at 2 h, and the T/NT ratio was 1.82. Conclusions 131I-JHIT2 probe possesses relatively high stability in vitro, and has certain targeting capacity towards HepG2 cells in vitro and HepG2 tumor-bearing nude mouse model, which lays certain foundation for the targeted radionuclide diagnosis and treatment of liver cancer. Key words: Carcinoma, hepatocellular; Aptamer; Radionuclide imaging