Experimental study of tumor hypoxia imaging with 99Tcm-MAVGG-azathiopurine in vitro and in vivo

Objective: To investigate the biodistribution and scintigraphy of 99Tcm-mercaptoacetyl-Val-Gly-Gly-(MAVGG)-azathiopurine in hypoxic mice tumors (S180) in vivo. Methods: Azathiopurine was radiolabelled with 99Tcm via the bifunctional chelator MAVGG. Cell accumulation was studied in S180 cells under hypoxic condition and compared with oxygenous condition. The results were expressed as an accumulation ratio, Cin/Cout, defined as concentration of radioactivity within the cells divided by that in the external medium. Biodistribution and scintigraphy in S180 tumor bearing mice were studied at different time point post injection of 99Tcm-MAVGG-azathiopruine. Results: At 5 h after injection, the Cin/Cout was 0.59 for hypoxia and 0.36 for oxygenation. The biodistribution was 4.24 for tumor-to-muscle and 1.55 for tumor-to-blood at 3 h post-injection. The results were showed in scintigraphic images. Conclusion: Retention of 99Tcm-MAYGG-azathiopurine was 1.6 fold higher in hypoxic than in oxygenous condition, suggesting this compound might possibly be a candidate for tumor hypoxic imaging agent. (authors)