Evaluating the effects of an angiogenesis inhibitor of endostar with a novel RGD dimer probe labeled by 99Tcm

Abstract

Objective To study the feasibility of a novel probe 99Tcm-HYNIC-2(poly-(ethylene glycol),PEG) 4-Dimer (Dimer:E-[c (RGDfK) 2]) as a potential imaging agent for integrin αv β3 positive tumors,and also to observe the influence of an angiogenesis inhibitor,endostar,on the biodistribution and tumor uptake of the tracer in tumor bearing nude mice.Methods The expression of integrin αv β3 in human glioma cells U87MG was determined with immunofluorescence staining before and after treatment with endostar.99Tcm-HYNIC-2PEG4-Dimer was prepared and administered in U87MG tumor bearing mice in 6 h after either administration of endostar (200 μl) or saline (control group) and then biodistribution study was performed.Other 16 mice were divided into endostar treated group (20 mg/kg) and control group (saline) and then gamma imaging was performed in the two groups.Statistical significance of differences between the two groups was assessed using two-sample t test.Results Radiochemical purity of 99Tcm-HYNIC-2PEG4-Dimer was exceeded 95％.The expression of integrin αvβ3 in U87MG cell was high and gradually decreased after treatment with endostar.There was a negative dose-effect relationship between the dose of endostar and the expression of integrin αvβ3 with the peak effect at the dose of 400 μg/ml.The distribution study in vivo showed that the tracer uptake of U87MG tumors was high,but it decreased after injection of endostar.At 90 min,the ％ID/g of endostar and control groups were 1.50±0.08 and 6.27±0.33,respectively (t =40.23,P＜0.05).The average T/NT ratios of 99Tcm-HYNIC-2PEG4-Dimer uptake in the endostar and control groups were 1.02±0.11 and 2.58±0.36,respectively (t =10.25,P＜0.05).The integrin αv β3 positive expression ratios of tumor in endostar and control groups were (33.1 ±2.7) ％ and (81.5±3.2) ％,respectively (t =32.60,P＜0.05).Conclusions The novel probe 99Tcm-HYNIC-2PEG4-Dimer may be a promising radiotracer for integrin αvβ3-positive tumor imaging.It may be used for monitoring the therapeutic effect of endostar and may be potentially used for screening the candidates of anti-angiogenesis therapy. Key words: Glioma; Arg-Gly-Asp; Radionuclide imaging; Angiogenesis inhibitors ; Mice, nude