Search

Purpose We investigated whether a 99m Tc radiolabeled anti-miRNA-155 oligonucleotide (AMO-155) could visualize the expression of miR-155 in multiple kinds of tumors in vivo . Methods AMO-155 was chemically synthesized and modified with 2′- O -methyl (2′-OMe) and phosphorothioate (PS). It was radiolabeled with 99m Tc via the conjugation with NHS-MAG3 at 5′ end. The characterization of radiolabeling and serum stability was evaluated using high performance liquid chromatography (HPLC) and agarose gel electrophoresis. The expression of C/EBPβ, one of the miR-155 target proteins, was assessed using Western blot. The cellular uptake and delivery of AMO-155 was further evaluated in tumor cells. 99m Tc-AMO-155 was tested in vivo in multiple tumor models, including miR-155 over-expressed and low-expressed tumor models. Finally, biodistribution of 99m Tc-AMO-155 was evaluated. Results 99m Tc-AMO-155 was prepared with high yield and radiochemical purity. It showed high stability in fresh human serum for 10 h. 99m Tc-AMO-155 displayed comparable capacity as unlabeled AMO-155 to increase the expression of C/EBPβ protein in MCF-7 cells. 99m Tc-AMO-155 showed an increased radioactive uptake in MCF-7 cells after 8 h of incubation, whereas no change of 99m Tc-pertechnetate uptake was observed. Carboxyfluorescein (FAM) labeled AMO-155 had higher fluorescent delivery than Control in HeLa and HepG2 cells by confocal microscopy. In miR-155 over-expressed tumor models, 99m Tc-AMO-155 showed significantly higher tumor accumulation than 99m Tc-Control. Furthermore, 99m Tc-AMO-155 was capable of discriminating between MCF-7 and MDA-MB-231 tumors based on their expression of miR-155. Conclusions Our study successfully prepared and proved 99m Tc-AMO-155 as a prospective imaging agent for the noninvasive visualization of miR-155 expression in vivo . [ABSTRACT FROM AUTHOR]