Yu Liu1,2,3, Xueyan Jin1,2, Xiaoli Lan1,2, Juntao Lang1,2, Qiong Wen1,2, Rui An4,2. 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. 4. Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China - anruiwh@163.com.
Abstract
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.
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.