title: PET imaging of colorectal and breast cancer by targeting EphB4 receptor with 64Cu-labeled hAb47 and hAb131 antibodies.
abstract: Accumulating evidence suggests that ephrin type B receptor 4 (EphB4) plays a key role in the progression of numerous cancer types. In this study, we developed a series of (64)Cu-labeled antibodies for PET imaging of tumor EphB4 expression.
  
  
  METHODS
  Anti-EphB4 antibodies (hAb47 and hAb131) were conjugated with the (64)Cu-chelator DOTA through lysine, cysteine, or oligosaccharide on the antibody. DOTA-human IgG (hIgG) was also prepared as a control, which did not bind to EphB4. The EphB4 binding activity of these probes was evaluated through the bead-based binding assay with EphB4-alkaline phosphatase. The resulting PET probes were further evaluated in both HT29 (colorectal cancer) and MDA-MB-231 (breast cancer) xenografts.
  
  
  RESULTS
  All 3 conjugation methods retained most of the EphB4 binding activity of the antibodies (83.85% ± 3.82%, 76.25% ± 5.90%, 98.93% ± 3.75%, and 82.09% ± 4.14% for DOTA-Lys-hAb47, DOTA-Cys-hAb47, DOTA-Sug-hAb47, and DOTA-Lys-hAb131, respectively). Although DOTA-Sug-hAb47 demonstrated the highest receptor binding activity based on a EphB4 binding assay, the corresponding PET probe was trapped in the liver quickly in vivo. In HT29 xenografts, both (64)Cu-DOTA-Lys-hAb47 and (64)Cu-DOTA-Cys-hAb47 demonstrated prominent tumor accumulation, which reached a maximum at 48 h after injection (18.13 ± 1.73 percentage injected dose [%ID]/g and 11.81 ± 2.05 %ID/g, respectively). In contrast, (64)Cu-DOTA-Lys-hIgG had a low tumor accumulation, thus demonstrating the target specificity of EphB4-antibody-based probes. Moreover, (64)Cu-DOTA-Lys-hAb131 (29.48 ± 2.60 %ID/g) demonstrated significantly higher HT29 tumor accumulation than (64)Cu-DOTA-Lys-hAb47. (64)Cu-DOTA-Lys-hAb131 was also found to specifically accumulate in the MDA-MB-231 tumor model (12.96 ± 2.31 %ID/g).
  
  
  CONCLUSIONS
  We have demonstrated that EphB4 can serve as a valid target for colorectal and breast cancer imaging. This approach would be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-EphB4 treatment. Moreover, these newly developed probes may have important applications in other cancer types overexpressing EphB4.
authors.affiliation: Molecular Imaging Center, Department of Radiology, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Shuanglong
authors.initials: S
authors.lastname: Liu
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.forename: Ryan
authors.initials: R
authors.lastname: Park
authors.forename: Ren
authors.initials: R
authors.lastname: Liu
authors.forename: Zanxian
authors.initials: Z
authors.lastname: Xia
authors.forename: Jiacong
authors.initials: J
authors.lastname: Guo
authors.forename: Valery
authors.initials: V
authors.lastname: Krasnoperov
authors.forename: Parkash S
authors.initials: PS
authors.lastname: Gill
authors.forename: Zibo
authors.initials: Z
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Shan
authors.forename: Peter S
authors.initials: PS
authors.lastname: Conti
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D003301:Copper Radioisotopes / Q000493:pharmacokinetics; D005260:Female; D019073:HT29 Cells; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D051379:Mice; D008819:Mice, Nude; D049268:Positron-Emission Tomography / Q000379:methods; D036224:Receptor, EphB4 / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000911:Antibodies, Monoclonal; D003301:Copper Radioisotopes; D036224:Receptor, EphB4
keywords: 64Cu; EphB4; PET; breast cancer; colorectal cancer