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Published on: March 24, 2017
Synergistic Cytotoxic Effect on Gastric Cancer Cells of an Immunotoxin Cocktail in Which Antibodies Recognize
Osamu Kusano-Arai1,2, Hiroko Iwanari1, Shota Kudo3
11 Department of Quantitative Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo , Tokyo, Japan .
Abstract:
Cadherin-17 (CDH17) is highly expressed in gastric cancer and is thus considered to be a good target for antibody therapy. CDH17 is classified as a nonclassical cadherin, in that it is composed of seven extracellular cadherin domains. We generated anti-CDH17 monoclonal antibodies (mAbs) which recognize the extracellular domain of CDH17. Competitive assay using AGS, a gastric cancer cell line, cells revealed that five selected anti-CDH17 mAbs recognize different epitopes on CDH17. As AGS cells were shown to exhibit broad expression pattern of CDH17 by flow cytometry, we separated three clones with a low (10,000/cell), medium (50,000/cell), and high (200,000/cell) expression level, designating them as AGSlow, AGSmed, and AGShigh, respectively. The mAbs, coupled with saporin, exhibited effective cytotoxicity to AGShigh, but poor cytotoxicity to AGSlow. By contrast, the immunotoxin cocktail using the three clones D2101, D2005, and D2008, which recognize different epitopes, exhibited efficient cytotoxicity, even to the AGSlow group. The effect of the immunotoxin cocktail is synergistic, as the combination index was demonstrated to be below 1.0, as calculated by the method of Chou and Talalay using CalcuSyn software. These results suggest that the immunotoxin cocktail targeted to multiple epitopes has synergistic effects on low expression level cells, which expand the applicable range of immunotoxin therapy for cancer.
Insights
Targeting Cadherin-17 (CDH17) with multiple antibodies in a cocktail enhances cancer therapy. This approach shows synergistic effects, improving efficacy even in cells with low CDH17 expression.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Cadherin-17 (CDH17) is highly expressed in gastric cancer, making it a promising target for antibody-based therapies.
- CDH17 is a nonclassical cadherin with seven extracellular domains, offering multiple sites for antibody binding.
Purpose of the Study:
- To develop and evaluate anti-CDH17 monoclonal antibodies (mAbs) for gastric cancer therapy.
- To investigate the efficacy of a combination immunotoxin therapy targeting multiple CDH17 epitopes.
Main Methods:
- Generation of anti-CDH17 monoclonal antibodies (mAbs).
- Epitope mapping using competitive assays on gastric cancer cell lines (AGS).
- Assessment of immunotoxin cytotoxicity on AGS cells with varying CDH17 expression levels (AGSlow, AGSmed, AGShigh).
- Synergistic effect analysis using the Chou-Talalay method with CalcuSyn software.
Main Results:
- Five anti-CDH17 mAbs recognizing distinct epitopes were identified.
- Immunotoxins targeting single epitopes showed limited efficacy on low-expression cells.
- A cocktail of mAbs targeting multiple epitopes demonstrated synergistic cytotoxicity, even in AGSlow cells.
- The combination index below 1.0 confirmed synergistic effects of the immunotoxin cocktail.
Conclusions:
- Targeting multiple CDH17 epitopes with an immunotoxin cocktail yields synergistic therapeutic effects.
- This multi-epitope targeting strategy enhances the applicability of immunotoxin therapy for gastric cancer, particularly in low-expression scenarios.
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