Production and characterization of a humanized single-chain antibody against human integrin alphav beta3 protein

Anti-Proliferative Effect of Specific Anti-EGFR Single Chain Antibody on Triple Negative Breast Cancer Cells

Background

Targeted therapy is an important treatment strategy that is widely used for cancer therapy. Epidermal growth factor receptor (EGFR) is overexpressed in a significant percentage of Triple-negative breast cancer (TNBC) patients. Although Cetuximab, which targets EGFR, has shown some inhibitory effects on TNBC cells, Cetuximab resistance cases due to ligand-independent activating mutations in the EGFR gene limit its application. Due to various benefits of single chain antibodies (scFvs), the use of these antibodies in cancer targeted therapy is increasing. In this study, a specific anti-EGFR antibody was isolated and evaluated.

Methods

Panning procedure was used against an immunodominant epitope of EGFR in its dimerization arm using a diverse phage library. Polymerase Chain Reaction (PCR) and fingerprinting were applied to identify the specific clones. The MTT tetrazolium assay was performed to evaluate the inhibitory effects of selected anti- EGFR scFv phage antibody on MDA-MB-468, a TNBC cell line.

Results

After four round of panning, one dominant pattern was observed in DNA fingerprinting with frequency of 85%. The growth of MDA-MB-468 cells was decreased dose-dependently after treatment with anti-EGFR scFv phage antibody. No significant inhibitory effect of M13KO7 helper phage as negative control on the cell growth of MDA-MB-468 was observed (p> 0.05).

Conclusion

The selected anti-EGFR scFv with high anti proliferative effect on TNBC cells offers an effective alternative for TNBC targeted therapy. The antibody, which binds to the dimerization arm of EGFR and inhibits EGFR dimerization, could also overcome TNBC cases with Cetuximab resistance due to ligandindependent activating mutations.

Small molecular peptide-ScFv αvβ3 conjugates specifically inhibit lung cancer cell growth in vitro and in vivo

Integrin αvβ3 (ITG) is highly expressed in various cancers and is considered a major target for anti-angiogensis cancer therapy. The single chain fragment variable of which (ScFv αvβ3) has been reported to inhibit tumor growth both in vitro and in vivo. Here, we conjugated cdGIGPQc which can exclusively bind to NSCLC cells according to our previous study synthesized by SPPS with ScFv αvβ3 expressed in E. coli BL21 (DE3) to develop a novel lung cancer specific targeted drug. Specific cell targeting of cdGIGPQc-ScFv was assessed in parallel with the single ScFv and a control nonspecific peptide-ScFv through immunofluorescence and flow cytometry while the αvβ3-binding property was examined by Western blot. Our results showed that cdGIGPQc-ScFv retained both the lung cancer-binding activity of cdGIGPQc and the antigen-recognizing ability of ScFv αvβ3 in vitro. CCK8 assays and in animal experiments suggested that cdGIGPQc-ScFv possessed a superior antitumor effect than ScFv and nonspecific peptide-ScFv both in vitro and vivo. Further immunohistochemical staining revealed that cdGIGPQc-ScFv retarded lung cancer growth through inhibiting tumor angiogensis and proliferation. Therefore, cdGIGPQc delivery of ScFv αvβ3 to lung cancer may be a hopeful new strategy for enhancing specific antitumor efficacy and cdGIGPQc-ScFv could be a potential drug for lung cancer targeted treatment.

The antitumor efficacy of a novel adenovirus-mediated anti-p21Ras single chain fragment variable antibody on human cancers in vitro and in vivo

Activated ras genes are found in a large number of human tumors, and therefore are one of important targets for cancer therapy. This study investigated the antitumor effects of a novel single chain fragment variable antibody (scFv) against ras protein, p21Ras. The anti-p21Ras scFv gene was constructed by phage display library from hybridoma KGHR1, and then subcloned into replication-defective adenovirus vector to obtain recombinant adenovirus KGHV100. Human tumor cell lines with high expression of p21Ras SW480, MDA-MB‑231, OVCAR-3, BEL-7402, as well as tumor cell line with low expression of p21Ras, SKOV3, were employed to investigate antitumor effects in vitro and in vivo. Fluorescence microscopy demonstrated that KGHV100 was able to express intracellularly anti-p21Ras scFv antibody in cultured tumor cells and in transplantation tumor cells. MTT, Transwell, colony formation, and flow cytometry analysis showed that KGHV100 led to significant growth arrest in tumor cells with high p21Ras expression, and induced G0/G1 cell cycle arrest in the studied tumor cell lines. In vivo, KGHV100 significantly inhibited tumor growth following intratumoral injection, and the survival rates of the mice were higher than the control group. These results indicate that the adenovirus-mediated intracellular expression of the novel anti-p21Ras scFv exerted strong antitumoral effects, and may be a potential method for therapy of cancers with p21Ras overexpression.

The effect of bovine rotavirus and its nonstructural protein 4 on ER stress-mediated apoptosis in HeLa and HT-29 cells

Endoplasmic reticulum (ER) plays important roles in multiple cellular processes as well as cell survival and apoptosis. Perturbation of ER functions leads to ER stress and unfolded protein response (UPR). The primary goal of this response is cell survival, but severe ER stress can trigger apoptosis signaling. In tumor cells, chronically activated UPR response provides tumor growth. So, apoptosis induced by the ER stress has been the target for anti-cancer therapy. In this in vitro study, we examined the apoptotic effect associated with ER stress of bovine rotavirus and its nonstructural protein 4 (NSP4) alone in two cancer cell lines. The plasmid pcDNA3.1 encoding NSP4 protein of bovine rotavirus transfected with lipofectamine 2000 into the HeLa and HT-29 cells for protein production. MTT, flow cytometry, and Western blot were used to evaluate the cell viability, apoptosis, and expression level of C/EBP-homologous protein (CHOP) and activated caspase-4. In parallel, the apoptotic effect of the bovine rotavirus associated with ER stress in the infected cells was examined too. The cytotoxic and apoptotic effect of NSP4 protein on the cells were statistically significant compared to the control groups. However, Western blot showed that the expression of the NSP4 protein by recombinant plasmid did not lead to high expression of CHOP and activation of caspase-4. Interestingly, rotavirus not only induced significant apoptosis but also caused an increase in CHOP expression and caspase-4 activation in the infected cells compared to control. As a result, NSP4 protein and bovine rotavirus can be considered a potential novel bio-therapeutic strategy for cancer treatment.

Antibody humanization methods for development of therapeutic applications

Recombinant antibody technologies are rapidly becoming available and showing considerable clinical success. However, the immunogenicity of murine-derived monoclonal antibodies is restrictive in cancer immunotherapy. Humanized antibodies can overcome these problems and are considered to be a promising alternative therapeutic agent. There are several approaches for antibody humanization. In this article we review various methods used in the antibody humanization process.

A new recombinant immunotoxin hscFv-ETA' demonstrates specific cytotoxicity against chronic myeloid leukemia cells in vitro

Antibodies against cell surface antigens of tumor have attracted increasing attention in immunotherapy for tumor diagnosis and treatment. Recently, we constructed a new recombinant immunotoxin for possible clinical application in patients with chronic myeloid leukemia (CML). A functional humanized single chain variable fragment (hscFv) against CML patient cells was previously obtained from an anti-CML cell hybridoma derived monoclonal antibody. By insertion into the bacterial vector pWW20, the hscFv was fused with a deletion mutant of Pseudomonas exotoxin A (ETA'). Then the fusion fragment was inserted into the bacterial vector pET32a(+). After isopropyl β-d-thiogalactoside (IPTG) induction, the 6× His tagged hscFv-ETA' protein was periplasmically expressed and purified by Ni(2+)-NTA column. The characteristics of the recombinant protein were assessed by cell membrane-ELISA, flow cytometry, and toxicity assays in CML cell lines and CML patient cells. The recombinant immunotoxin showed significant toxicity toward the CML cell lines K562 and KU812 as tested by MTT and apoptosis assay. Approximately 37% of leukemia cells of CML patients were driven into apoptosis by hscFv-ETA' as measured by flow cytometric analysis. In conclusion, the hscFv-ETA' is efficacious against CML in vitro, providing the basis for a novel therapeutic strategy for the treatment of CML patients.

BSP gene silencing inhibits migration, invasion, and bone metastasis of MDA-MB-231BO human breast cancer cells

Bone sialoprotein (BSP) has been implicated in a variety of physiological and pathophysiological events, including tumor cell invasion, bone homing, adhesion, and matrix degradation. To explore the potential involvement of BSP in human breast cancer cell invasion and metastasis, we used retrovirus-mediated RNAi to deplete BSP levels in the human bone-seeking breast cancer cell line MDA-MB-231BO (231BO) and established the 231BO-BSP27 and 231BO-BSP81 cell clones. Cell proliferation, colony formation, wound healing, and the ability to invade into matrigel of these BSP-depleted clones were all decreased. Both 231BO-BSP27 cells and 231BO-BSP81 cells showed a significant (15.4% and 28.6% respectively) reduction of bone metastatic potential following intracardiac injection as determined by X-ray detection and by hematoxylin and eosin staining. Moreover, the expression of integrins αvβ3 and β3 was decreased in the BSP-silenced cells whereas ectopic BSP expression increased the integrins αvβ3 and β3 levels. These results together suggest that BSP silencing decreased the integrin αvβ3 and β3 levels, in turn inhibiting cell migration and invasion and decreasing the ability of the cells to metastasize to bone.

Toward low-cost affinity reagents: lyophilized yeast-scFv probes specific for pathogen antigens

The generation of affinity reagents, usually monoclonal antibodies, remains a critical bottleneck in biomedical research and diagnostic test development. Recombinant antibody-like proteins such as scFv have yet to replace traditional monoclonal antibodies in antigen detection applications, in large part because of poor performance of scFv in solution. To address this limitation, we have developed assays that use whole yeast cells expressing scFv on their surfaces (yeast-scFv) in place of soluble purified scFv or traditional monoclonal antibodies. In this study, a nonimmune library of human scFv displayed on the surfaces of yeast cells was screened for clones that bind to recombinant cyst proteins of Entamoeba histolytica, an enteric pathogen of humans. Selected yeast-scFv clones were stabilized by lyophilization and used in detection assay formats in which the yeast-scFv served as solid support-bound monoclonal antibodies. Specific binding of antigen to the yeast-scFv was detected by staining with rabbit polyclonal antibodies. In flow cytometry-based assays, lyophilized yeast-scFv reagents retained full binding activity and specificity for their cognate antigens after 4 weeks of storage at room temperature in the absence of desiccants or stabilizers. Because flow cytometry is not available to all potential assay users, an immunofluorescence assay was also developed that detects antigen with similar sensitivity and specificity. Antigen-specific whole-cell yeast-scFv reagents can be selected from nonimmune libraries in 2–3 weeks, produced in vast quantities, and packaged in lyophilized form for extended shelf life. Lyophilized yeast-scFv show promise as low cost, renewable alternatives to monoclonal antibodies for diagnosis and research.