Abstract
Antibodies have become an attractive class of therapeutic agents for solid tumors, mainly because of their high target selectivity and affinity. The target binding properties of antibodies are critical for their efficacy and toxicity. Our lab has developed a bioluminescence resonance energy transfer (BRET) imaging approach that directly supports the measurement of the binding dynamics between antibodies and their targets in the native tumor environment. In the present study, we have developed a spatially resolved computational model analyzing the longitudinal BRET imaging data of antibody–target binding and exploring the mechanisms of biphasic binding dynamics between a model antibody cetuximab and its target, the epidermal growth factor receptor (EGFR). The model suggested that cetuximab is bound differently to EGFR in the stroma-rich area than in stroma-poor regions, which was confirmed by immunofluorescence staining. Compared to the binding in vitro, cetuximab bound to EGFR to a “slower-but-tighter” degree in the living tumors. These findings have provided spatially resolved characterizations of antibody–target binding in living tumors and have yielded many mechanistic insights into the factors that affect antibody interactions with its targets and treatment efficacy.
Highlights
Antibodies have become an attractive class of therapeutic agents for solid tumors, mainly because of their high target selectivity and affinity
Transient activation of epidermal growth factor receptor (EGFR) is associated with tumor cell proliferation, whereas sustained activation can lead to cell differentiation[6]
The tumor receptor occupancy (RO) peaked at approximately 4 h post-dosing, which was consistent across doses, suggesting that the extravasation of DY605-CTX into tumors is a slow and linear process
Summary
Antibodies have become an attractive class of therapeutic agents for solid tumors, mainly because of their high target selectivity and affinity. Compared to the binding in vitro, cetuximab bound to EGFR to a “slower-but-tighter” degree in the living tumors These findings have provided spatially resolved characterizations of antibody–target binding in living tumors and have yielded many mechanistic insights into the factors that affect antibody interactions with its targets and treatment efficacy. More than 30 therapeutic antibodies have been approved for treating tumors at various s tages[1,2] These broad applications of therapeutic antibodies in solid tumors are largely due to their high target binding selectivity and affinity compared with traditional cytotoxic agents. Once bound to their targets, therapeutic antibodies eradicate tumor cells mainly by three mechanisms: blocking the pathogenic ligand–receptor interactions, triggering cell apoptosis pathways, or activating host effector functions[3]. The target binding properties in living systems remain largely uncharacterized
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