Cell growth inhibition and apoptotic effects of a specific anti-RTFscFv antibody on prostate cancer, but not glioblastoma, cells

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.

Isolation of Neutralizing Human Single Chain Antibodies Against Conserved Hemagglutinin Epitopes of Influenza a Virus H3N2 Strain

BACKGROUND

Immunotherapies using monoclonal antibodies against influenza A hemagglutinin (HA) has been an effective means for controlling Influenza spread. An alternative method for viral prophylaxis and treatment is the development of human single-chain variable fragment (scFv) antibodies with no human anti-mouse antibody (HAMA) response and high specificity. In the present study, two highly conserved sequences of HA were used to select specific neutralizing scFvs against H3N2 strain of influenza A virus.

METHODS

Biopanning process was performed to isolate specific scFv antibodies against highly conserved HA sequences, aa173-181 and 227-239, of the influenza A H3N2 strain from a scFv library. The peptide-binding specificity of the selected clones was examined via phage ELISA. The soluble forms of the clones were prepared and assessed using western blot analysis and neutralization efficiency of the selected clones were examined by TCID50 neutralizing assay and real-time PCR.

RESULTS

scFv 1 and scFv 2 were selected against HA of H3N2 influenza A virus with frequencies of 95% and 30% in the panning process, respectively. Western blot analysis confirmed the scFv band size. Significant neutralization in the presence of scFv 1 and scFv 2 were obtained. Real time PCR revealed significant decrease in viral copy number.

CONCLUSION

Two specific neutralizing scFvs against two highly conserved neutralizing epitopes of the influenza A virus HA glycoprotein were selected. A strong neutralization effect of scFv1, showed the potential of this antibody for H3N2 influenza A controlling in the viral spread.

Isolation of Specific Human Recombinant Antibodies Against Glycoprotein 41 of HIV

BACKGROUND

Blocking of gp41 of HIV virus, which is involved in the virus entry has been introduced as an effective strategy against HIV infection. In this study we used phage display technology to select specific single chain antibody (scFv) against gp41 HIV for its application in clinical use.

METHODS

Single chain antibodies against an epitope located in C- terminal part of gp41 were selected using the panning process which enriched a phage antibody display library of scFv. Following panning, 20 clones were amplified by PCR and fingerprinted. To test the specificity of the selected antibodies phage ELISA was performed.

RESULTS

PCR of the library clones demonstrated the presence of VH-linker-VL inserts. Fingerprinting of the clones showed a diverse library with different patterns. Fingerprinting of selected clones after panning revealed two specific single chain antibodies with frequency of 25% and 20%. These clones were preserved for further investigations. Phage ELISA results showed specificity of the two scFvs against the immunodominant epitope of gp41. The absorbance of the scFv1 and scFv2 were 0.72 and 0.63 while the absorbance of the no peptide were 0.18 and 0.12, respectively.

CONCLUSION

In this study we successfully selected two specific recombinant antibodies against gp41. These libraries are human antibodies with high affinity and specificity and have the potential to be used for diagnosis and treatment. Further investigations are needed to show the effects of the antibodies in vitro and in vivo.

Selection and Evaluation of Specific Single Chain Antibodies against CD90, a Marker for Mesenchymal and Cancer Stem Cells

BACKGROUND

CD90, a membrane-associated glycoprotein is a marker used to identify mesenchymal stem cells (MSCs). Recent studies have introduced CD90, which induces tumorigenic activity, as a cancer stem cell (CSC) marker in various malignancies. Blocking CD90 activity with anti-CD90 monoclonal antibodies enhanced anti-tumor effects. To date, highly specific antibody single-chain variable fragments (scFvs) have been isolated against various targets and showed promising results in cancer immunotherapy.

METHODS

A phage antibody was produced from a scFv library using M13KO7 helper phage. The phage library was panned against a CD90 epitope. To select specific clones, PCR and DNA fingerprinting were performed and common patterns were identified. The panning results were confirmed by phage ELISA.

RESULTS

Of 20 clones selected after panning, 16 shared identical fingerprints. One clone from this group reacted specifically with the epitope in phage ELISA. The average absorbance of wells coated with the CD90 peptide was significantly greater than that of wells containing no peptide (p=0.03).

CONCLUSION

Currently, recombinant antibodies are used not only as highly specific detection tools, but due to their specific characteristics, are applied in targeted cancer therapies. The anti-CD90 scFv selected in this study has the potential to be used to detect MSCs and target CSCs and offers promising strategies for treatment of various cancers.

Cell growth inhibition and apoptotic effects of a specific anti-RTFscFv antibody on prostate cancer, but not glioblastoma, cells

Background: Single chain antibody (scFv) has shown interesting results in cancer immunotargeting approaches, due to its advantages over monoclonal antibodies. Regeneration and tolerance factor (RTF) is one of the most important regulators of extracellular and intracellular pH in eukaryotic cells. In this study, the inhibitory effects of a specific anti-RTF scFv were investigated and compared between three types of prostate cancer and two types of glioblastoma cells.  Methods: A phage antibody display library of scFv was used to select specific scFvs against RTF using panning process. The reactivity of a selected scFv was assessed by phage ELISA. The anti-proliferative and apoptotic effects of the antibody on prostate cancer (PC-3, Du-145 and LNCaP) and glioblastoma (U-87 MG and A-172) cell lines were investigated by MTT and Annexin V/PI assays.  Results: A specific scFv with frequency 35% was selected against RTF epitope. This significantly inhibited the proliferation of the prostate cells after 24 h. The percentages of cell viability (using 1000 scFv/cell) were 52, 61 and 73% for PC-3, Du-145 and LNCaP cells, respectively, compared to untreated cells. The antibody (1000 scFv/cell) induced apoptosis at 50, 40 and 25% in PC-3, Du-145 and LNCaP cells, respectively. No growth inhibition and apoptotic induction was detected for U-87 and A172 glioblastoma cells.  Conclusions: Anti-RTFscFv significantly reduced the proliferation of the prostate cancer cells. The inhibition of cell growth and apoptotic induction effects in PC-3 cells were greater than Du-145 and LNCaP cells. This might be due to higher expression of RTF antigen in PC-3 cells and/or better accessibility of RTF to scFv antibody. The resistance of glioblastoma cells to anti-RTF scFv offers the existence of mechanism(s) that abrogate the inhibitory effect(s) of the antibody to RTF. The results suggest that the selected anti-RTF scFv antibody could be an effective new alternative for prostate cancer immunotherapy.