Novel antibody probes for the characterization of endosialin/TEM-1
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Daniel J. O’Shannessy1, Michael F. Smith1, Elizabeth B. Somers1, Stephen M. Jackson1, Earl Albone1, Brian Tomkowicz1, Xin Cheng1, Young Park1, Danielle Fernando1, Andrew Milinichik1, Brad Kline1, Regan Fulton2, Pankaj Oberoi3 and Nicholas C. Nicolaides1
1 Morphotek, Inc., Exton, PA, USA
2 PhenoPath, Seattle, WA, USA
3 Meso Scale Discovery, Rockville, MD, USA
Nicholas C. Nicolaides, email:
Keywords: endosialin; CD248; TEM-1; tumor microenvironment; sEND
Received: April 18, 2016 Accepted: June 09, 2016 Published: August 02, 2016
Endosialin (Tumor Endothelial Marker-1 (TEM-1), CD248) is primarily expressed on pericytes of tumor-associated microvasculature, tumor-associated stromal cells and directly on tumors of mesenchymal origin, including sarcoma and melanoma. While the function of endosialin/TEM-1 is incompletely understood, studies have suggested a role in supporting tumor growth and invasion thus making it an attractive therapeutic target. In an effort to further understand its role in cancer, we previously developed a humanized anti-endosialin/TEM-1 monoclonal antibody (mAb), called ontuxizumab (MORAb-004) for testing in preclinical and clinical studies. We herein report on the generation of an extensive panel of recombinant endosialin/TEM-1 protein extracellular domain (ECD) fragments and novel mAbs against ECD motifs. The domain-specific epitopes were mapped against ECD sub-domains to identify those that can detect distinct structural motifs and can be potentially formatted as probes suitable for diagnostic and functional studies. A number of mAbS were shown to cross-react with the murine and human protein, potentially allowing their use in human animal models and corresponding clinical trials. In addition, pairing of several mAbs supported their use in immunoassays that can detect soluble endosialin/TEM-1 (sEND) in the serum of healthy subjects and cancer patients.
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