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Updated: Oct 14, 2025
Analyzing Tumor and Tissue Distribution of Target Antigen Specific Therapeutic Antibody
Published on: May 16, 2020
A patch of positively charged residues regulates the efficacy of clinical DR5 antibodies in solid tumors
Gururaj Shivange1, Tanmoy Mondal2, Evan Lyerly3
1Laboratory of Novel Biologics, Medical Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA; Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville VA 22908, USA.
Abstract:
Receptor clustering is the first and critical step to activate apoptosis by death receptor-5 (DR5). The recent discovery of the autoinhibitory DR5 ectodomain has challenged the long-standing view of its mechanistic activation by the natural ligand Apo2L. Because the autoinhibitory residues have remained unknown, here we characterize a crucial patch of positively charged residues (PPCR) in the highly variable domain of DR5. The PPCR electrostatically separates DR5 receptors to autoinhibit their clustering in the absence of ligand and antibody binding. Mutational substitution and antibody-mediated PPCR interference resulted in increased apoptotic cytotoxic function. A dually specific antibody that enables sustained tampering with PPCR function exceptionally enhanced DR5 clustering and apoptotic activation and distinctively improved the survival of animals bearing aggressive metastatic and recurrent tumors, whereas clinically tested DR5 antibodies without PPCR blockade function were largely ineffective. Our study provides mechanistic insights into DR5 activation and a therapeutic analytical design for potential clinical success.
Insights
A newly discovered positively charged residue patch (PPCR) in death receptor-5 (DR5) inhibits its clustering. Blocking PPCR with antibodies enhances DR5-mediated apoptosis and improves tumor survival in animal models.
Area of Science:
- Molecular biology
- Immunology
- Cancer research
Background:
- Receptor clustering is essential for activating apoptosis via death receptor-5 (DR5).
- The discovery of an autoinhibitory DR5 ectodomain has raised questions about its activation mechanism by the natural ligand Apo2L.
- The specific residues responsible for DR5 autoinhibition have remained unidentified.
Purpose of the Study:
- To identify and characterize the autoinhibitory residues in the DR5 ectodomain.
- To investigate the role of these residues in DR5 receptor clustering and apoptosis.
- To develop a novel therapeutic strategy for enhancing DR5-mediated apoptosis in cancer.
Main Methods:
- Site-directed mutagenesis to substitute positively charged residues in the DR5 ectodomain.
- Antibody-mediated interference with the identified inhibitory region.
- Assessment of DR5 clustering and apoptotic activity in vitro.
- Evaluation of therapeutic efficacy in animal models of aggressive metastatic and recurrent tumors.
Main Results:
- A crucial patch of positively charged residues (PPCR) was identified in the DR5 ectodomain, responsible for autoinhibition by electrostatically separating receptors.
- Mutational substitution and antibody-mediated blockade of PPCR significantly increased DR5 clustering and apoptotic cytotoxic function.
- A dually specific antibody targeting PPCR demonstrated exceptional enhancement of DR5 clustering, apoptotic activation, and significantly improved tumor-bearing animal survival.
- Clinically tested DR5 antibodies lacking PPCR blockade were largely ineffective.
Conclusions:
- The PPCR is a key determinant of DR5 autoinhibition, regulating receptor clustering and apoptosis.
- Targeting the PPCR with specific antibodies represents a promising therapeutic strategy for enhancing anti-cancer apoptosis.
- This study provides critical mechanistic insights into DR5 activation and a novel design for effective DR5-targeted cancer therapeutics.
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