Abstract
In vivo imaging of aminopeptidase N (APN/CD13) expression is crucial for the early detection of cancer. This study attempted to show that APN/CD13 expression can be imaged and quantified with novel Cerenkov luminescence tomography (CLT). Na131I with various activities was placed at different depths in a tissue-mimicking phantom, and various porcine tissues and luminescent images were acquired. The binding of 131I-NGR with human fibrosarcoma HT1080 and human colon cancer HT-29 cells was detected with Cerenkov luminescence imaging (CLI). Nude mice bearing HT-1080 tumors were imaged after injection with 131I-NGR using both planar and tomographic CLI methods. The penetration depth increased with ascending activity of Na131I. There was a robust linear correlation between the optical signal intensity and the HT1080 cell numbers (r2 = .9691), as well as the activity (r2 = .9860). The three-dimensional visualization CLT results clearly showed that 131I-NGR uptake in tumor tissues represented a high expression of the APN/CD13 receptor. CLT also allowed quantifying 131I-NGR uptake in tumor tissues showing an average activity of 0.1388 ± 4.6788E-6 MBq in tumor tissues. Our study indicated that 131I-NGR combined with CLT allowed us to image and quantify tumor-associated APN/CD13 expression noninvasively. The promising CLT technique could be potentially used for sensitively evaluating tumor angiogenesis in vivo.
Highlights
In vivo imaging of aminopeptidase N (APN/CD13) expression is crucial for the early detection of cancer
In vivo imaging of APN/CD13 expression is crucial for the early detection of cancer
We found that 0.037 MBq was approximately the minimal activity that could be detected by Cerenkov luminescence imaging (CLI) when the depth of Na131I was 1 mm; at 0.185 MBq, it was 4 mm; at 3.7 MBq, it was 7 mm; and at 24.05 MBq, it was 10 mm
Summary
In vivo imaging of aminopeptidase N (APN/CD13) expression is crucial for the early detection of cancer. This study attempted to show that APN/CD13 expression can be imaged and quantified with novel Cerenkov luminescence tomography (CLT). Li and colleagues presented 3D Cerenkov luminescence tomography (CLT) based on a homogeneous mouse model using 18F-fluorodeoxyglucose (18F-FDG).[16] the assumption of a homogeneous optical property background will lead to inaccurate source reconstruction.[19,20] In our previous study, we performed in vivo 3D CLT based on a heterogeneous mouse model with an implanted Na131I radioactive source.[17] Our results showed that the reconstruction based on a heterogeneous mouse model was more accurate in localization than using the homogeneous one
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