Construction, expression, and activity of a novel immunotoxin comprising a humanized antiepidermal growth factor receptor scFv and modified Pseudomonas aeruginosa exotoxin A

In silico and in vitro evaluation of a PE38 and Nb-based recombinant immunotoxin targeting the GRP78 receptor in cancer cells

Cancer is a global health problem despite the most developed therapeutic modalities. The delivery of specific therapeutic agents to a target increases the effectiveness of cancer treatment by reducing side effects and post-treatment issues. Our aim in this study was to design a recombinant protein consisting of nanobody molecules and exotoxin that targets the surface GRP78 receptor on tumor cells. Bioinformatics methods make drug design and recombinant protein evaluation much easier before the laboratory steps. Two constructs were designed from a single-variable domain on heavy chain nanobody domains and PE toxin domains II, Ib, and III. The physicochemical properties, secondary structure, and solubility of the chimeric protein were analyzed using different software. Prostate cancer DU-145 and breast cancer MDA-MB-468 cell lines were used as GRP78-positive and negative controls, respectively. Accordingly, the cytotoxicity, binding affinity, cell internalization, and apoptosis were evaluated using MTT, enzyme-linked immunosorbent assay, and western blot. The results showed that in the DU-145 cell line, the cytotoxicity of two recombinant immunotoxins is dose and time-dependent. In MDA-MB-468 and HEK-293 cells, such an event does not occur. It is possible that two constructs designed for immunotoxins can attach to GRP78-positive cancer cells and then eradicate cancer cells by internalization and apoptosis. As our in vitro results were in line with in silico data confirming the Bioinformatics predictions, it can be concluded that the designed recombinant immunotoxins may exhibit therapeutic potential against GRP78-positive tumor cells.

A single-chain variable fragment-anticancer lytic peptide (scFv-ACLP) fusion protein for targeted cancer treatment

Antibody-directed drugs for targeted cancer treatment have become a hot topic in new anticancer drug development; however, antibody-fused therapeutic peptides were rarely documented. Herein, we designed a fusion protein with a cetuximab-derived single-chain variable fragment targeting epidermal growth factor receptor (anti-EGFR scFv) and the anticancer lytic peptide (ACLP) ZXR2, connected by a linker (G₄ S)₃ and MMP2 cleavage site. The anti-EGFR scFv-ZXR2 recombinant protein showed specific anticancer activity on EGFR-overexpressed cancer cell lines in a concentration- and time-dependent manner, as it can bind to EGFR on cancer cell surfaces. This fusion protein caused cell membrane lysis as ZXR2, and showed improved stability in serum compared with ZXR2. These results suggest that scFv-ACLP fusion proteins may be potential anticancer drug candidates for targeted cancer treatment, which also provide a feasible idea for targeted drug design.

Engineered Bifunctional Proteins for Targeted Cancer Therapy: Prospects and Challenges

Bifunctional proteins (BFPs) are a class of therapeutic agents produced through genetic engineering and protein engineering, and are increasingly used to treat various human diseases, including cancer. These proteins usually have two or more biological functions-specifically recognizing different molecular targets to regulate the related signaling pathways, or mediating effector molecules/cells to kill tumor cells. Unlike conventional small-molecule or single-target drugs, BFPs possess stronger biological activity but lower systemic toxicity. Hence, BFPs are considered to offer many benefits for the treatment of heterogeneous tumors. In this review, the authors briefly describe the unique structural feature of BFP molecules and innovatively divide them into bispecific antibodies, cytokine-based BFPs (immunocytokines), and protein toxin-based BFPs (immunotoxins) according to their mode of action. In addition, the latest advances in the development of BFPs are discussed and the potential limitations or problems in clinical applications are outlined. Taken together, future studies need to be centered on understanding the characteristics of BFPs for optimizing and designing more effective such drugs.

Immunotoxins and nanobody-based immunotoxins: review and update

Immunotoxins (ITs) are protein-based drugs that compose of targeting and cytotoxic moieties. After binding the IT to the specific cell-surface antigen, the IT internalises into the target cell and kills it. Targeting and cytotoxic moieties usually include monoclonal antibodies and protein toxins with bacterial or plant origin, respectively. ITs have been successful in haematologic malignancies treatment. However, ITs penetrate poorly into solid tumours because of their large size. Use of camelid antibody fragments known as nanobodies (Nbs) as a targeting moiety may overcome this problem. Nbs are the smallest fragment of antibodies with excellent tumour tissue penetration. The ability to recognise cryptic (immuno-evasive) target antigens, low immunogenicity, and high-affinity are other fundamental characteristics of Nbs that make them suitable candidates in targeted therapy. Here, we reviewed and discussed the structure and function of ITs, Nbs, and nanobody-based ITs. To gain sound insight into the issue at hand, we focussed on nanobody-based ITs.

Paper Title "Hu7CG2: A Novel Humanized Anti-Epidermal Growth Factor Receptor (EGFR) Biparatopic Nanobody"

Targeted therapy is an effective and appropriate approach with low side effects in cancer therapy compared with other treatment approaches. Epidermal growth factor receptor, EGFR, is a favorable biomarker as targeted therapy because it overexpresses in several cancers. Monoclonal antibodies are common agents for targeted therapy. Nanobody is the smallest format of monoclonal antibodies with unique properties that include hiding epitope targeting, high stability, low production cost, and ease of connection to other components. The main challenge in targeted therapy by monoclonal antibodies is their immunogenicity due to their non-human nature. In this study, we designed, constructed, and evaluated a novel humanized anti- EGFR biparatopic nanobody, hu7CG2. The hu7CG2 was designed by grafting the complementarity-determining regions of two camelid anti- EGFR nanobodies known as 7C12 and EG2 to a universal scaffold and then connected with a glycine-serine linker. The results of antigen-binding activity and cell viability assays showed that the hu7CG2 inhibited the growth of EGFR overexpression tumor cells. The data showed that hu7CG2 might be a useful tool in the targeting and treatment of tumor cells.

Advances in epidermal growth factor receptor specific immunotherapy: lessons to be learned from armed antibodies

The epidermal growth factor receptor (EGFR) has been recognized as an important therapeutic target in oncology. It is commonly overexpressed in a variety of solid tumors and is critically involved in cell survival, proliferation, metastasis, and angiogenesis. This multi-dimensional role of EGFR in the progression and aggressiveness of cancer, has evolved from conventional to more targeted therapeutic approaches. With the advent of hybridoma technology and phage display techniques, the first anti-EGFR monoclonal antibodies (mAbs) (Cetuximab and Panitumumab) were developed. Due to major limitations including host immune reactions and poor tumor penetration, these antibodies were modified and used as guiding mechanisms for the specific delivery of readily available chemotherapeutic agents or plants/bacterial toxins, giving rise to antibody-drug conjugates (ADCs) and immunotoxins (ITs), respectively. Continued refinement of ITs led to deimmunization strategies based on depletion of B and T-cell epitopes or substitution of non-human toxins leading to a growing repertoire of human enzymes capable of inducing cell death. Similarly, the modification of classical ADCs has resulted in the first, fully recombinant versions. In this review, we discuss significant advancements in EGFR-targeting immunoconjugates, including ITs and recombinant photoactivable ADCs, which serve as a blueprint for further developments in the evolving domain of cancer immunotherapy.