Biodistribution characteristics and SPECT imaging of (99m)Tc-RET and (99m)Tc-REG in human lung cancer xenografts.

Objective: To investigate the biodistribution and single-photon emission computed tomography (SPECT) imaging of (99m)Tc-labeled arginine-glutamic acid-threonine (RET) and arginine-glutamic acid-glycine (REG) in nude mice bearing human lung cancer xenografts.
Materials and Methods: RET and REG were labeled directly with (99m)Tc and their binding efficiency to tumor cells was measured in human nonsmall cell lung cancer H1299 cells. After intravenously injecting (99m)Tc-RET and (99m)Tc-REG into normal mice and nude mice bearing human lung cancer xenografts, their biodistribution was measured at different postinjection times, and percentages of injected dose per gram tissue (% ID/g) of organs of interest were calculated. The mice bearing H1299 lung cancer xenografts were scanned by SPECT at different times following the (99m)Tc-RET or (99m)Tc-REG injection.
Results: The radiochemical purity of (99m)Tc-RET and (99m)Tc-REG was 93.15%±2.02% and 92.90%±2.86%, respectively. The binding rate of (99m)Tc-RET and (99m)Tc-REG to H1299 cells was 3.56%±0.37% and 2.32%±0.31%, respectively. The uptake of (99m)Tc-RET and (99m)Tc-REG in tumor was 4.96±1.05% ID/g at 4 hours postinjection and 1.95±0.73% ID/g at 2 hours postinjection, respectively. Tumors in nude mice could be best imaged at 4.5-6 hours postinjection of (99m)Tc-RET.
Conclusion: (99m)Tc-RET has a higher binding rate to H1299 cells than (99m)Tc-REG and might be used as a potential lung cancer imaging agent.