99mTc-labeled single-domain antibody EG2 in targeting epidermal growth factor receptor. Issue 5 (May 2015)

• Record Type: Journal Article
• Authors: Li, Chongjiao; Wen, Bing; Wang, Lifei; Feng, Hongyan; Xia, Xiaotian; Ding, Zhiling; Gao, Bin; Zhang, Yongxue; Lan, Xiaoli
• Is Part Of: Nuclear medicine communications. Volume 36:Issue 5(2015:May)
• Publication Date: 2015-05
• Subjects: Nuclear medicine -- Periodicals; 616.07575
• DOI: 10.1097/MNM.0000000000000264
• Languages: English
• ISSNs: 0143-3636

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Objective</title> <p>The aim of this study was to explore the targeting ability and metabolic characteristics of the technetium-99m-labeled single-domain antibody (<sup>99m</sup>Tc-sdAb) EG2 targeting epidermal growth factor receptor (EGFR) through an in-vitro and in-vivo study.</p> </sec> <sec> <title>Materials and methods</title> <p>The sdAb EG2 was radiolabeled with <sup>99m</sup>Tc using a tricarbonyl kit. The EGFR expression level of A431 and OCM-1 cells was confirmed using immunofluorescence staining. Cell binding, blocking, uptake, and efflux studies were performed to investigate the binding specificity of <sup>99m</sup>Tc-sdAb EG2 <italic>in vitro</italic>. Single-photon emission computed tomography imaging and biodistribution studies were used to explore the targeting abilities and metabolic characteristics of <sup>99m</sup>Tc-sdAb EG2 <italic>in vivo</italic>.</p> </sec> <sec> <title>Results</title> <p> <sup>99m</sup>Tc-sdAb EG2 was successfully prepared with labeling yields of 60–71% and specific activity of 1.83±0.29 GBq/mg (<italic>n</italic>=3). Immunofluorescence staining revealed high and low EGFR expression on the surface of A431 and OCM-1 cells, respectively. The binding affinity of <sup>99m</sup>Tc-sdAb EG2 to A431 cells was 43.53±1.89 nmol/l. <sup>99m</sup>Tc-sdAb EG2 uptake in A431 cells <italic>in vitro</italic> could be blocked by ∼19, 40, and 66% in the presence of excess unlabeled sdAb EG2 at 100, 500, and 1000 nmol/l, respectively. Single-photon emission computed imaging indicated that A431 tumor images could be clearly displayed at early scan time points after <sup>99m</sup>Tc-sdAb EG2 injection, even as early as 1 h. Biodistribution study showed that the A431 tumor uptake of <sup>99m</sup>Tc-sdAb EG2 was blocked by about 51% at 3 h after coinjecting excess of sdAb EG2. However, there were almost no OCM-1 tumor images at the corresponding scan time points and the OCM-1 tumor uptake was only 0.40±0.13% injected dose per gram of tissue (<italic>n</italic>=5) at 3 h.</p> </sec> <sec> <title>Conclusion</title> <p>This study demonstrated that sdAb EG2 can effectively target EGFR <italic>in vitro</italic> and <italic>in vivo</italic> in tumors, suggesting that it could be used as a molecular probe for EGFR detection.</p> </sec> </abstract>