HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JNM Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Blankenberg, F. G. Articles by Backer, J. M. Search for Related Content PubMed PubMed Citation Articles by Blankenberg, F. G. Articles by Backer, J. M.

Tumor Imaging Using a Standardized Radiolabeled Adapter Protein Docked to Vascular Endothelial Growth Factor

¹ Department of Pediatrics, Stanford University, Stanford, California
² Division of Nuclear Medicine, Department of Radiology, Stanford University, Stanford, California
³ SibTech, Inc., Newington, Connecticut
⁴ Theseus Imaging Corporation, Boston, Massachusetts

Direct radiolabeling of proteins can result in the loss of targeting activity, requires highly customized procedures, and yields heterogeneous products. Here we describe a novel imaging complex comprised of a standardized ^99mTc-radiolabeled adapter protein noncovalently bound to a "Docking tag" fused to a "Targeting protein". The assembly of this complex is based on interactions between human 109-amino acid (HuS) and 15-amino acid (Hu-tag) fragments of ribonuclease I, which serve as an "Adapter protein" and a Docking tag, respectively. Methods: HuS modified with hydrazinonicotinamide (HYNIC) was radiolabeled using ^99mTc-tricine to a specific activity of 3.4–7.4 MBq/µg. Protein complexes were then formed by mixing ^99mTc-HuS with equimolar amounts of either Hu-tagged VEGF₁₂₁ (Hu-VEGF [vascular endothelial growth factor]) or Hu-tagged anti-VEGFR-2 single-chain antibody (Hu-P4G7) and incubating on ice for 15 min. 4T1 luc/gfp luciferase-expressing murine mammary adenocarcinoma cells (1 x 10⁴) were implanted subcutaneously or injected intravenously into BALB/c mice. Bioluminescent imaging (BLI) was performed 10 d later. Immediately after BLI visualization of tumor, 18.5–37 MBq of tracer (5–10 µg of protein) were injected via tail vein. One hour later planar or SPECT images were obtained, followed by killing the mice. Results: There was significantly (P = 0.0128) increased uptake of ^99mTc-HuS/Hu-VEGF (n = 10) within subcutaneous tumor as compared with ^99mTc-HuS/Hu-P4G7 (n = 5) at biodistribution assay (2.68 ± 0.75 vs. 1.8 ± 0.21; tumor-to-subcutaneous tissue [ratio of specific activities], respectively), despite similar molecular weights. The focal ^99mTc-HuS/Hu-VEGF uptake seen on planar images (3.44 ± 1.16 [tumor to soft-tissue background]) corresponded directly to the locations of tumor observed by BLI. Region of interest analyses of SPECT images revealed a significant increase of ^99mTc-HuS/Hu-VEGF (n = 5) within the lungs with BLI-detectable pulmonary tumor nodules as compared with controls (n = 4) (right: 4.47 ± 2.07 vs. 1.79 ± 0.56; left: 3.66 ± 1.65 vs. 1.62 ± 0.45, tumor lung [counts/pixel]/normal lung [counts/pixel], respectively). Conclusion: ^99mTc-HuS/Hu-VEGF complex is stable for at least 1 h in vivo and can be effectively used to image mouse tumor neovasculature in lesions as small as several millimeters in soft tissue. We expect that a similar approach can be adapted for in vivo delivery of other targeting proteins of interest without affecting their bioactivity.

Key Words: vascular endothelial growth factor • radionuclide imaging • protein complexes • ribonuclease I • SPECT

Related articles in JNM:

THIS MONTH IN JNM

JNM 2004 45: 8A-9A. [Full Text]  

This article has been cited by other articles:

				B. L. Franc, P. D. Acton, C. Mari, and B. H. Hasegawa Small-Animal SPECT and SPECT/CT: Important Tools for Preclinical Investigation J. Nucl. Med., October 1, 2008; 49(10): 1651 - 1663. [Abstract] [Full Text] [PDF]

				W. Cai and X. Chen Multimodality Molecular Imaging of Tumor Angiogenesis J. Nucl. Med., June 1, 2008; 49(Suppl_2): 113S - 128S. [Abstract] [Full Text] [PDF]

				W. Cai, K. Chen, K. A. Mohamedali, Q. Cao, S. S. Gambhir, M. G. Rosenblum, and X. Chen PET of Vascular Endothelial Growth Factor Receptor Expression J. Nucl. Med., December 1, 2006; 47(12): 2048 - 2056. [Abstract] [Full Text] [PDF]

				W. Cai, J. Rao, S. S. Gambhir, and X. Chen How molecular imaging is speeding up antiangiogenic drug development. Mol. Cancer Ther., November 1, 2006; 5(11): 2624 - 2633. [Abstract] [Full Text] [PDF]

				J. F. Tait, C. Smith, Z. Levashova, B. Patel, F. G. Blankenberg, and J.-L. Vanderheyden Improved Detection of Cell Death In Vivo with Annexin V Radiolabeled by Site-Specific Methods J. Nucl. Med., September 1, 2006; 47(9): 1546 - 1553. [Abstract] [Full Text] [PDF]

				W. S. El-Deiry, C. C. Sigman, and G. J. Kelloff Imaging and Oncologic Drug Development J. Clin. Oncol., July 10, 2006; 24(20): 3261 - 3273. [Abstract] [Full Text] [PDF]

				M. V. Backer, T. I. Gaynutdinov, V. Patel, A. K. Bandyopadhyaya, B.T.S. Thirumamagal, W. Tjarks, R. F. Barth, K. Claffey, and J. M. Backer Vascular endothelial growth factor selectively targets boronated dendrimers to tumor vasculature Mol. Cancer Ther., September 1, 2005; 4(9): 1423 - 1429. [Abstract] [Full Text] [PDF]