Background: Gliomas

originating from glial cells

are the most common neoplasms affecting the central nervous system

and glioblastoma multiforme is the most malignant subtype of glioma. The classical subtype of glioblastoma is defined by epidermal growth factor receptor (EGFR) gene amplification

and glioblastomas bearing EGFR amplifications often express EGFRvIII. This suggests that EGFRvIII may operate as critical drivers in the genesis of glioblastoma

hence representing ideal targets for targeted anticancer therapies. Purpose: The aim is to establish a radiolabeling method of antisense oligonucleotide (U2) from U87-EGFRvIII glioma cells with radionuclide rhenium (188Re) and to investigate the possibility of using 188Re-U2 as imaging agents for brain glioma. Methods: A high affinity of antisense oligonucleotide sequences U2 from U87-EGFRvIII glioma cells was screened by the cell systematic evolution of ligands by exponential enrichment

and was directly labeled with 188Re. The optimal labeling condition and stability in vitro were investigated by an orthogonal experimental design method. Labeling rates were determined by paper chromatography. Blood radioactivity clearance of 188Re-U2 in rabbits was evaluated by determining blood radioactive concentrations at different time points after injection of 188Re-U2

and its dynamic distribution was investigated by SPECT imaging. Results: Antisense oligonucleotide (U2) was successfully radiolabeled with 188Re and the labeling rate of 188Re-U2 was 70%±14%. After purification of the labeled 188Re-U2 with Sep-PaK C18 reversed phase extraction cartridge

the radiochemical purity was 70.6% after placing in physiological saline for 24 h and 95.55% after incubation at 37 ºC with human serum. SPECT imaging showed that 188Re-U2 could be quickly cleared from the blood in normal animals primarily through the kidneys

and the radioactivity in other tissues and organs remained low. Conclusion: This method of directly labeling antisense oligonucleotide (U2) with 188Re is simple with better labeling efficiency and stability both in vitro and in vivo

and so 188Re-U2 has more ideal biodistribution and biokinetics in vivo.Cited