Generation and characterization of an anti-delta like ligand-4 Nanobody to induce non-productive angiogenesis

Antibody-based targeting of angiogenesis is a key approach for cancer treatment. Delta-like ligand 4 (DLL4) plays a pivotal role in tumor neovascular development and angiogenesis during tumor progression. It forecasts the prognosis of human malignancies and blocking its signaling can help to inhibit neovascularization and tumor metastasis. Nanobodies are the smallest antigen-binding domains of heavy chain antibodies in camelidae. The aim of this study was to develop a Nanobody against DLL4 and apply binding and functional approaches to target it. In this work, a Nanobody library against human recombinant DLL4 was developed. After panning, the periplasmic-extract (PE) of individual colonies were screened through ELISA. The interactions between Nanobody and DLL4 were assessed using immunohistochemistry and FACS. The functional assessment was carried out via tube formation assay. We selected a Nanobody (3Nb3) with a high binding signal to DLL4, associated with a binding affinity of 3.6 nM. It was demonstrated that 3Nb3 binds to native DLL4 on the surface of MKN cells and gastric carcinoma tissue, and also inhibits the maturation of capillary-like structures in HUVECs. The results were indicative of the potential of Nanobody for DLL4 identification and can broaden the scope for development of cancer diagnosis and treatment techniques.