This study successfully screened and characterized two high-affinity nanobodies targeting EGFR with non-competitive binding properties, and validated their functional activity in inhibiting the EGFR signaling pathway in cellular models, providing high-quality molecular tools for subsequent antibody engineering and tumor-targeted research.
Literature Overview
The article "Camelid-Derived Nanobodies Targeting Human Epidermal Growth Factor Receptor: Screening, Expression, and Functional Validation," published in the journal Antibodies, reviews and summarizes the screening of nanobodies targeting the human epidermal growth factor receptor (EGFR) using camel immunization and phage display technology, with systematic characterization of their binding properties, epitope relationships, and preliminary functional activity. The study successfully obtained two nanobodies, Nb2H4 and Nb2B6, that specifically bind EGFR, recognizing non-overlapping epitopes with high affinity, and demonstrated their ability to inhibit the EGFR signaling pathway in cellular models. This work provides valuable molecular resources for EGFR-related structural studies, targeted therapeutic development, and multivalent antibody construction. The research strategy and validation workflow presented offer a reproducible experimental framework for the development of nanobodies targeting membrane receptors.Background Knowledge
The epidermal growth factor receptor (EGFR) is a key receptor tyrosine kinase in the ErbB family, widely involved in physiological processes such as cell proliferation, survival, and migration. It is abnormally overexpressed or mutated in various solid tumors and closely associated with tumor invasiveness and poor prognosis, making it an important target in cancer therapy. Several monoclonal antibodies (e.g., cetuximab) and small-molecule inhibitors (e.g., gefitinib) targeting EGFR are already in clinical use, yet their efficacy is limited by large molecular size, poor tissue penetration, and high immunogenicity. Nanobodies, derived from the variable domain of heavy-chain-only antibodies (VHH) in camelids, have a molecular weight of only ~15 kDa, exhibiting high affinity, stability, good solubility, and low immunogenicity, and are easily expressed in E. coli, making them suitable for molecular engineering. Their small size offers significant advantages in tumor penetration, multispecific construct development, molecular imaging, and drug delivery. Several EGFR-targeting nanobodies, such as 7D12 and OA-cb6, have been reported, but most studies focus on application validation of single candidates, lacking systematic screening and characterization of paired nanobodies (recognizing non-competing epitopes). Paired nanobodies can be used to construct bispecific molecules, enhance detection sensitivity, or induce receptor degradation, making the development of EGFR-targeting nanobodies with defined epitope relationships highly significant for advancing antibody engineering and precision therapy. This study employs a whole-cell immunization strategy to screen for nanobodies recognizing native conformational epitopes, and systematically evaluates their binding kinetics, epitope competition, and preliminary function, thereby filling a gap in current research.
Research Methods and Experiments
Researchers used transiently transfected HEK-293F cells expressing full-length human EGFR as antigens to immunize a dromedary camel. RNA was then extracted from peripheral blood lymphocytes to construct a phage-display nanobody library. After two rounds of biopanning, enrichment was performed using biotin-labeled EGFR extracellular domain protein to screen for binding-specific clones. Positive clones were identified by ELISA and subjected to sequencing to assess diversity. Two candidate nanobodies, Nb2H4 and Nb2B6, were subcloned into expression vectors and recombinantly expressed in E. coli, followed by purification via nickel-affinity chromatography and size-exclusion chromatography. Their binding specificity, affinity, and epitope relationships were systematically evaluated using size-exclusion chromatography–high-performance liquid chromatography (SEC-HPLC), bio-layer interferometry (BLI), and flow cytometry. Flow cytometry was used to assess the binding of the nanobodies to 5637 bladder cancer cells with endogenous high EGFR expression, with HEK-293T cells (low EGFR expression) serving as a negative control. Additionally, the CCK-8 cell proliferation assay was used to evaluate the inhibitory effect of Nb2H4 on EGF-induced cell proliferation, providing preliminary validation of its functional activity.Key Conclusions and Perspectives
Research Significance and Prospects
This study successfully developed and characterized a pair of nanobodies targeting EGFR, offering not only high-value molecular tools for basic EGFR-related research but also laying the foundation for nanobody-based tumor-targeted therapeutic strategies. The non-competing binding properties of Nb2H4 and Nb2B6 make them potentially valuable for constructing bispecific antibodies or nanobody-drug conjugates (e.g., ADCs), possibly enabling more efficient receptor blockade or internalization. Moreover, their high affinity and small size offer advantages in molecular imaging (e.g., PET/SPECT), enabling early tumor detection and treatment monitoring.
Future studies could further explore the pharmacokinetics, tumor-targeting efficiency, and anti-tumor efficacy of these two nanobodies in animal models. Additionally, structural biology approaches could be used to resolve the complex structures of these nanobodies bound to EGFR, guiding rational design and optimization. Furthermore, fusing Nb2H4 or Nb2B6 with other functional domains (e.g., toxins, T-cell engagers) could lead to the development of novel targeted therapeutics. The screening workflow established in this study—combining whole-cell immunization with phage display—can also be extended to other membrane receptor targets, accelerating the discovery of nanobody-based drugs.
Conclusion
This study successfully screened and characterized two nanobodies, Nb2H4 and Nb2B6, targeting the human epidermal growth factor receptor (EGFR) using camel immunization and phage display technology. Both exhibit high affinity and specificity, recognize non-competing epitopes on EGFR, and are suitable for paired use. Functional assays demonstrated that Nb2H4 effectively inhibits EGF-induced cell proliferation, suggesting its potential as an inhibitor of the EGFR signaling pathway. This work not only provides a high-quality pair of EGFR-targeting nanobody tools but also offers valuable molecular resources for the development of nanobody-based diagnostic and therapeutic strategies. These findings lay a solid foundation for subsequent antibody engineering, structural studies, and tumor-targeted applications, highlighting the broad potential of nanobodies in precision medicine. The overall strategy is highly transferable and can serve as a reference for the development of nanobodies against other membrane receptor targets.
