ORIGINAL ARTICLE   

The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2019 June;63(2):216-24

DOI: 10.23736/S1824-4785.16.02864-8

Copyright © 2016 EDIZIONI MINERVA MEDICA

language: English

SPECT imaging of colorectal cancer by targeting CD 133 receptor with 99mTc-labeled monoclonal antibody

Yu LIU ^{1, 2, 3}, Xueyan JIN ^{1, 2}, Xiaoli LAN ^{1, 2}, Juntao LANG ^{1, 2}, Qiong WEN ^{1, 2}, Rui AN ^{1, 2} ✉

¹ Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; ² Hubei Key Laboratory of Molecular Imaging, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; ³ Department of Radiology, Anhui Provincial Hospital, Hefei, China

BACKGROUND: Previous reports suggested that CD133-positive cells had biological features of cancer stem cells (CSCs). Furthermore, CD133 expression was reported as an unfavorable prognostic factor in patients. Therefore, a new radiolabeled probe, 99mTc labeled AC133 antibody which binding with CD133 specifically, was developed to noninvasively detect CSCs by SPECT in vivo.
METHODS: CD133 expression was evaluated by flow cytometry in three colon cancer cell lines (HCT116, Lovo and DLD1). AC133 antibody and control IgG were conjugated with succinimidyl-6-hydrazinonicotinate hydrochloride (SHNH), and then labeled with 99mTc. The new radiolabeled probe was named as 99mTc-SHNH-AC133. The vitro cell binding assays, series SPECT imaging and biodistribution analyses were performed. Flow cytometry, immunofluorescence staining of tumor tissues were carried to verify the in-vivo imaging results.
RESULTS: 99mTc-SHNH-AC133 was labeled with a high radiochemical purity (97.7±2.4%, N.=3) and specific activity (4.07 MBq/µg). Cellular experiments showed that the labeled AC133 antibody retained with a high binding affinity on CD133-positive cells (HCT116 and Lovo cells). Biodistribution analyses showed high tumor uptake of the tracer in HCT116 and Lovo xenografts (8.82±0.73 and 7.37±0.26 %ID/g, respectively, N.=4) and high tumor-to-muscle ratios (13.18±2.84 and 11.13±0.53, respectively, N.=4) at 36 h after injection, resulting in high contrast SPECT images with high specific tumor uptake. However, the tumor bearing CD133-negative cell (DLD1 cells) showed no obvious uptake of 99mTc-SHNH-AC133 both in-vitro cell binding and in-vivo imaging study. Moreover, the tumor uptake of 99mTc-SHNH-AC133 in positive tumor models was significantly reduced by pre-injection of excess unlabeled AC133 antibody. Flow cytometric analysis and immunofluorescence staining confirmed the CD133 expression in tumors, which correlated well with the in-vivo results.
CONCLUSIONS: This study showed that 99mTc-SHNH-AC133 exhibited high uptake in CD133-positive tumors. The high specificity and good tumor targeting properties of 99mTc-SHNH-AC133 may provide a new method to track or locate CSCs.

KEY WORDS: CD133; Monoclonal antibody; Cancer stem cells; SPECT imaging