title: Positron emission tomography imaging of tumor angiogenesis with a (61/64)Cu-labeled F(ab')(2) antibody fragment.
abstract: The objective of this study was to characterize the in vitro and in vivo properties of the F(ab')(2) fragment of TRC105, a human/murine chimeric IgG1 monoclonal antibody that binds with high avidity to human and murine CD105 (i.e., endoglin), and investigate its potential for positron emission tomography (PET) imaging of tumor angiogenesis after (61/64)Cu-labeling. TRC105-F(ab')(2) of high purity was produced by pepsin digestion of TRC105, which was confirmed by SDS-PAGE, HPLC analysis, and mass spectrometry. (61/64)Cu-labeling of NOTA-TRC105-F(ab')(2) (NOTA denotes 1,4,7-triazacyclononane-1,4,7-triacetic acid) was achieved with yields of >75% (specific activity: ∼115 GBq/μmol). PET imaging revealed rapid tumor uptake of (64)Cu-NOTA-TRC105-F(ab')(2) in the 4T1 murine breast cancer model (5.8 ± 0.8, 7.6 ± 0.6, 5.6 ± 0.4, 5.0 ± 0.6, and 3.8 ± 0.7% ID/g at 0.5, 3, 16, 24, and 48 h postinjection respectively; n = 4). Since tumor uptake peaked at 3 h postinjection, (61)Cu-NOTA-TRC105-F(ab')(2) also gave good tumor contrast at 3 and 8 h postinjection. CD105 specificity of the tracers was confirmed by blocking studies and histopathology. In conclusion, the use of a F(ab')(2) fragment led to more rapid tumor uptake (which peaked at 3 h postinjection) than radiolabeled intact antibody (which often peaked after 24 h postinjection), which may allow for same day immunoPET imaging in future clinical studies.
authors: Department of Radiology, University of Wisconsin-Madison, Madison, WI 53705-2275, United States.
authors: Hao
authors: H
authors: Hong
authors: Yin
authors: Y
authors: Zhang
authors: Hakan
authors: H
authors: Orbay
authors: Hector F
authors: HF
authors: Valdovinos
authors: Tapas R
authors: TR
authors: Nayak
authors: Jero
authors: J
authors: Bean
authors: Charles P
authors: CP
authors: Theuer
authors: Todd E
authors: TE
authors: Barnhart
authors: Weibo
authors: W
authors: Cai
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D015703:Antigens, CD / Q000276:immunology; D001943:Breast Neoplasms / Q000473:pathology*; D003300:Copper / Q000737:chemistry*; D000071063:Endoglin; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000276:immunology; D051379:Mice; D009389:Neovascularization, Pathologic / Q000473:pathology*; D049268:Positron-Emission Tomography / Q000379:methods*; D011956:Receptors, Cell Surface / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; C502004:Eng protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D011956:Receptors, Cell Surface; D003300:Copper