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Open Access Research article

Validation of glypican-3-specific scFv isolated from paired display/secretory yeast display library

Yonghai Li2, Donald L Siegel3, Nathalie Scholler4 and David E Kaplan12*

Author Affiliations

1 Medicine and Research Services, Philadelphia VA Medical Center, Philadelphia, PA, 19104, USA

2 Division of Gastroenterology, Department of Medicine, University of Pennsylvania, 600 CRB, 415 Curie Blvd, Philadelphia, PA, 19104, USA

3 Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA

4 Penn Ovarian Cancer Research Center, Center for Research on Reproduction and Women’s Health (CRRWH), Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA, 19104, USA

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BMC Biotechnology 2012, 12:23  doi:10.1186/1472-6750-12-23

Published: 7 May 2012

Abstract

Background

Glypican-3 (GPC3) is a heparan-sulfate proteoglycan frequently expressed on the cell membrane of malignant hepatocytes in hepatocellular carcinoma. The capacity for screening potential antibodies in vitro using human hepatocellular lines is critical to ensure binding to this highly post-translationally modified glycophosphatidylinositiol-linked protein. We hypothesized that we could utilize a recently described paired display/secretory yeast library to isolate human-derived scFv against glypican-3 for potential diagnostic and/or therapeutic application.

Results

Using two different biotinylated antigen targets, a synthesized 29mer fragment GPC3550-558 and a truncated GPC3368-548 fused with glutathione S-transferase (GST) we enriched the yeast display library to greater than 30% target-specific yeast with both positive selection and depletion of streptavidin- and GST-specific clones. After cloning of scFv cDNA from the enriched sub-library, scFv specificity was validated by ELISA for binding to recombinant protein from prokaryotic and eukaryotic sources and ultimately naturally presented human protein on the cell membrane of human hepatocellular cell lines. Specificity was confirmed using non-expressing cell lines and shRNA knockdown. Ultimately, five unique scFv with affinity EC50 ranging from 5.0-110.9nM were identified.

Conclusions

Using a paired display/secretory yeast library, five novel and unique scFvs for potential humoral or chimeric therapeutic development in human hepatocellular carcinoma were isolated and characterized.