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Published on: August 21, 2014
Isolation of novel EGFR-specific VHH domains
Elizabeth B Gottlin1, Xiangrong Guan, Charles Pegram
1Department of Radiologyy, Duke University Medical Center, Durham, North Carolina 27710, USA. liz.gottlin@duke.edu
Abstract:
Epidermal growth factor receptor (EGFR) is overexpressed or mutated in a high percentage of tumors. EGFR has long been considered a promising target for cancer diagnostic and therapeutic applications. However, monoclonal antibodies and other large antibody constructs diffuse into tumors slowly, limiting their efficacy. To develop lower molecular weight probes for EGFR and other tumor cell receptors, the authors immunized a llama with the extracellular domains (ECDs) of EGFR and an oncogenic mutant receptor, EGFRvIII, and with extracts of tumor cell lines. From the immune repertoire of the llama, the authors constructed a heavy chain variable domain (VHH domain)-phage library. At approximately 16 kDa, the VHH domain is a tenth of the size of a monoclonal antibody and is the smallest antibody fragment that retains specificity. By affinity selection from this library, the authors isolated many VHH domains with specificity for EGFR. The VHH domains bind to whole cells expressing the receptor but not to control cells lacking the receptor and can immunoprecipitate EGFR from cell lysates. Some VHH domains have cross-specificity with existing anti-EGFR monoclonal antibodies and have reasonably high (nM) affinities. The llama-VHH domain library is also potentially a rich source of targeting agents directed toward other tumor cell receptors.
Insights
Researchers developed small, llama-derived antibody fragments (VHH domains) targeting epidermal growth factor receptor (EGFR) for improved cancer diagnostics and therapeutics. These VHH domains offer enhanced tumor penetration compared to larger antibodies.
Area of Science:
- Oncology
- Immunology
- Biotechnology
Background:
- Epidermal growth factor receptor (EGFR) is frequently overexpressed or mutated in various tumors, making it a significant target for cancer therapy.
- Conventional large antibody constructs face challenges with slow tumor diffusion, limiting their diagnostic and therapeutic effectiveness.
- The need for smaller, more penetrant molecular probes for tumor-associated receptors like EGFR is critical.
Purpose of the Study:
- To develop novel, low-molecular-weight probes targeting EGFR and its oncogenic mutant EGFRvIII.
- To create a versatile platform for generating specific antibody fragments for cancer-related receptors.
Main Methods:
- Immunization of a llama with EGFR extracellular domains (ECDs), EGFRvIII, and tumor cell extracts.
- Construction of a heavy chain variable domain (VHH domain)-phage display library from the llama's immune repertoire.
- Affinity selection to isolate VHH domains with specificity for EGFR.
Main Results:
- Isolation of numerous VHH domains (approx. 16 kDa) with specific binding to EGFR-expressing cells.
- Demonstrated VHH domain ability to immunoprecipitate EGFR from cell lysates.
- Identified VHH domains with cross-reactivity to existing anti-EGFR monoclonal antibodies and nanomolar affinities.
Conclusions:
- VHH domains represent effective, small-sized antibody fragments for targeting EGFR.
- The llama-VHH domain library is a promising source for developing diagnostic and therapeutic agents for EGFR and other tumor receptors.
- The improved diffusion characteristics of VHH domains could enhance their efficacy in cancer applications.
