Preparation of 99Tcm-SHNH-AC133 and imaging on colon cancer bearing mice

Abstract

Objective To prepare 99Tcm-succinimidyl-6-hydrazinonicotinate hydrochloride (SHNH)-AC133 and evaluate its targeting ability on CD133 positive colon cancer by Gamma imaging, and to explore its feasibility as a molecular probe for cancer stem cells (CSCs). Methods CD133 expression was detected by immunofluorescence assay and flow cytometry on Lovo cell lines and tumor xenografts. CD133 specific monoclonal antibody (AC133) was conjugated with SHNH, and then labeled with 99Tcm to prepare 99Tcm-SHNH-AC133. The radiolabeled yield and radiochemical purity were investigated. Colon cancer xenografts were developed and Gamma imaging were performed. Region of interest (ROI) was drawn and the tumor/non-tumor (T/NT) ratio was calculated. For the blocking experiment, animals were pre-injected with excess unlabeled AC133. Two-sample t test was used to analyze the data. Results CD133 was expressed on the surface of Lovo cells. And the percentage of CD133 positive cells in Lovo tumor tissues was (29.5±3.4)%. The radiolabeled yield of 99Tcm-SHNH-AC133 was more than 85% and radiochemistry purity was (97.7±2.4)%. Gamma imaging demonstrated that 99Tcm-SHNH-AC133 could specifically target to Lovo tumors which could be gradually visible after 12 h. The tumor uptake was obvious at 24 h and T/NT ratio was 8.16±0.45. In blocking study, the tumor uptake was significantly reduced by pre-injection of excess unlabeled AC133 (3.52±0.13; t=19.8, P<0.05). Conclusions 99Tcm-SHNH-AC133 has high labeling yield and radiochemistry purity. The excellent targeting properties of 99Tcm-SHNH-AC133 on CD133 positive colon cancer demonstrate that it is a promising imaging agent for CSCs tracking in vivo. Key words: Antibodies, monoclonal; Succinimides; Technetium; Isotope labeling; Colonic neoplasms; Radionuclide imaging; Mice, nude