Abstract
There are currently several antibody therapies that directly target tumors, and antibody-drug conjugates represent a novel moiety as next generation therapeutics. Here, we used a unique screening probe, DT3C, to identify functional antibodies that recognized surface molecules and functional epitopes, and which provided toxin delivery capability. Accordingly, we generated the 90G4 antibody, which induced DT3C-dependent cytotoxicity in endothelial cells. Molecular analysis revealed that 90G4 recognized CD321, a protein localized at tight junctions. Although CD321 plays a pivotal role in inflammation and lymphocyte trans-endothelial migration, little is known about its mechanism of action in endothelial cells. Targeting of CD321 by the 90G4 immunotoxin induced cell death. Moreover, 90G4 immunotoxin caused cytotoxicity primarily in migratory endothelial cells, but not in those forming sheets, suggesting a critical role for CD321 in tumor angiogenesis. We also found that hypoxia triggered redistribution of CD321 to a punctate localization on the basal side of cells, resulting in functional impairment of tight junctions and increased motility. Thus, our findings raise the intriguing possibility that endothelial CD321 presented cellular localization in tight junction as well as multifunctional dynamics in several conditions, leading to illuminate the importance of widely-expressed CD321 as a potential target for antitumor therapy.
Highlights
Several types of monoclonal antibodies, with different mechanisms of action, are clinically available for targeted cancer therapy [1]
Using DT3C-based hybridoma screening, we successfully generated the 90G4 antibody, which caused cytotoxicity in endothelial cells in the form of a DT3C immunotoxin (Fig 1). 90G4 antigen was widely expressed in several endothelial cell types (Fig 2A)
Our findings describe the distinct roles played by CD321 in angiogenesis and tight junction formation
Summary
Several types of monoclonal antibodies, with different mechanisms of action, are clinically available for targeted cancer therapy [1]. In addition to major pathways, such as complementdependent cytotoxicity and antibody-dependent cellular cytotoxicity, some functional antibodies exhibit remarkable therapeutic effectiveness by modulating specific signaling cascades such as the vascular endothelial growth factor (VEGF) pathway during tumor angiogenesis [2]. Antibody-drug conjugates (ADC) face increasing demand as they can minimize both medication dose and severity of side effects. The discovery of specific and functional antibodies capable of delivering drugs into target cells remains a challenge.
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