Experiments Of ⁹⁹Tc^m-labeled New Cyclic RGDfK Dimer In Nude Mice Bearing U87MG Human Glioma Xenografts

ObjectiveRGD peptide (containing amino acid sequence Arg-Gly-Asp of a small peptide abbreviation) can specifically bind with the integrinαvβ3, which for the diagnosis and treatment of cancer. To enhance the RGD peptide and integrinαvβ3 binding affinity, and increase tumor uptake of the labeled probe, On the basis of preliminary studies on the RGD dimer structural transformation, we using joint hydrazine nicotinamide (HYNIC) as bifunctional agent, N-tris (hydroxymethyl) methyl glycine (tricine) and triphenylphosphine three sulfonate (TPPTS) as ligand coordination (coligand), prepared the 2PEG4 99Tcm-modified RGD dimer (Dimer:E [c (RGDfK)] 2): 99Tcm-HYNIC-2PEG4-Dimer, and with 99Tcm-HYNIC-Dimer comparison, expecting 2PEG4 can effectively improve the pharmacokinetic properties, reducing its normal tissue uptake.MethodsThe expression of integrinαvβ3 in the U87 human glioma cells as well as tumor tissues were determined by immunofluorescence staining. The 50% inhibitory concentration (IC50) values of c(RGDyK), HYNIC-Dimer and HYNIC-2PEG4-Dimer were determined on U87 human glioma cells with 125I-c(RGDyK) as the integrinαvβ3-pecific radiotracer。99Tcm-HYNIC-2PEG4-Dimer and 99Tcm-HYNIC-Dimer was prepared using non-SnCl2 formulation. The biodistribution and y imaging were performed in nude mice bearing human glioma xenografts.The unpaired t test were used for statistical analysis.ResultsHigh expression of integrinαvβ3 integrinαvβ3 in the U87 human glioma cells as well as tumor tissues can be seen. The labeling yield of the two radiotracers was more than 95%, and the radiochemical purity was more than 99% after purification with Sep-Pek C18 cartridge. HYNIC-2PEG4-Dimer had significantly higher integrinαvβ3 binding affinity than c(RGDyK) and HYNIC-Dimer (The IC50 values were 0.8 nmol/L,27 nmol/L and 2.4 nmol/L, respectively).Biodistribution data showed that 99mTc-HYNIC-2PEG4-Dimer was mainly excreted via the renal route. The tumor uptake of 99Tcm-HYNIC-2PEG4-Dimer was about 2.7 times higher than that of 99Tcm-HYNIC-Dimer at 2 h postinjection (5.71±0.96V.s.2.10±0.50%ID/g), t= 4.80, P< 0.05. y imaging revealed that the xenografted tumors were visible at 0.5 h postinjection, and the image contrast increased at 4 h postinjection with the rapid clearance of the radiotracer.Conclusion99Tcm-HYNIC-2PEG4-Dimer has higher integrinαvβ3 binding affinity,and the tumor uptake of its is higher, so it is a more promising radiotracer for integrinαvβ3-positive tumor imaging.