Targeting the EphB4 receptor for cancer diagnosis and therapy monitoring.

Accumulating evidence suggests that EphB4 plays key roles in cancer progression in numerous cancer types. In fact, therapies focusing on EphB4 have become potentially important components of various cancer treatment strategies. However, tumor sensitivity to EphB4 suppression may not be uniform for different cancers. In this study, we developed near-infrared fluorescence (NIRF) probes for EphB4 targeted imaging, based on EphB4-specific humanized monoclonal antibody hAb47. NIRF dye Cy5.5 was introduced to hAb47 either through the reaction with amino groups (named hAb47-Cy5.5) or sulfhydryl groups (named hAb47-Cy5.5-Mal). The resulting probes were evaluated in both HT-29 xenograft and the mAb131 (anti-EphB4) treated models. Although these methods lead to modifications of both the heavy chain and light chain of the antibody, the majority of the EphB4 binding affinity was maintained (81.62 ± 2.08% for hAb47-Cy5.5 and 77.14 ± 2.46% for hAb47-Cy5.5-Mal, respectively). hAb47-Cy5.5 was then chosen for in vivo NIRF imaging of EphB4 expression. In HT29 colorectal tumor xenografts, hAb47-Cy5.5 demonstrated significantly higher tumor uptake compared with that of the hIgG-Cy5.5 control, which was further confirmed by immunofluorescent staining. Moreover, hAb47-Cy5.5 successfully imaged the decreased EphB4 expression (confirmed by Western blot) in EphB4-targeted immunotherapy using another EphB4-specific antibody, mAb131. Collectively, hAb47-Cy5.5 could be used as a specific NIRF contrast agent for noninvasive imaging of EphB4 expression, which may predict whether an individual tumor would likely respond to EphB4 targeted interventions, as well as monitor the therapeutic response.