Biodistribution and gamma imaging of ⁹⁹Tc^m-arginine-glutamate-threonine in human lung cancer xenografts

Objective: To investigate the biodistribution and gamma imaging of ⁹⁹Tc^m-arginine-glutamate-threonine (RET) in nude mice bearing lung cancer xenografts and to explore its feasibility for human lung cancer imaging. Methods: RET was labeled directly with ⁹⁹Tc^m. The binding efficiency of ⁹⁹Tc^m-RET with human NSCLC H1299 cells was measured. ⁹⁹Tc^m-RET was injected via the tail vein in nude mice bearing H1299 xenografts. The mice(n = 32) were sacrificed at different time points: 15 min, 30 min, 1 h, 2 h, 4 h, 8 h, 24 h, and 48 h. Organs of interest were excised, weighted and counted by a gamma counter. The organ uptake was calculated as %ID/g. The gamma imaging was performed on 3 mice at 0.5, 1, 2, 4, 4.5, 5, 6 h after intravenous injection of 4.81 MBq ⁹⁹Tc^m-RET. Results: The radiolabeling yield of ⁹⁹Tc^m-RET was (93.15 ± 2.02)%, and the binding efficiency of ⁹⁹Tc^m-RET with H1299 cells was (3.56 ± 0.37)%. At 4 h after injection, the uptake of tumor, liver and spleen was (4.96 ± 1.05) %ID/g, (15.89 ± 1.84) %ID/g and (10.83 ± 1.66) %ID/g and the T/NT was 5.70 ± 0.21 for the heart and 12.40 ± 0.11 for the blood. The tumor in nude mice could be best visualized at 4.5-6.0 h. Conclusion: ⁹⁹Tc^m-RET might have potential to serve as a lung cancer imaging agent. (authors)