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Table 2 Tumor endothelial cell antigens investigated as targets of ValloVax™

From: Safety of targeting tumor endothelial cell antigens

Tumor endothelial target protein Role of antigen in tumor angiogenesis Refs.
Vascular endothelial growth factor receptor-1 (VEGFR-1); fms-like tyrosine kinase (flt)-1 Receptor that binds VEGF with high affinity Dominant receptor in the tumor microenvironment that is required for endothelial cell survival [70, 71]
Vascular endothelial growth factor receptor-2 (VEGFR2); Flk-1, KDR Also known as FLK-1 and KDR Binds to VEGF and is considered the most important receptor with regard to tumor angiogenesis Expressed on proliferating endothelium Low expression on healthy vascular endothelium [62, 72]
Endoglin/CD105 Selectively expressed by endothelial cells undergoing vasculogenesis, angiogenesis, and inflammation Promotes endothelial cell proliferation, migration, and tube formation during early development and in tumors [7378]
Fibroblast growth factor receptor (FGFR) Bind to fibroblast growth factor family members, having diverse roles in organogenesis, proliferation, pro-survival cell signaling and cellular migration FGF/FGFR system contributes to both adult angiogenesis and tumor angiogenesis FGFR signaling is implicated in escape of tumor vasculature from VEGF inhibitor treatment [61, 7982]
Integrin αvβ3; CD51/CD61 An extracellular matrix adhesion receptor that coordinates endothelial cell responses during angiogenesis Expressed in neo-angiogenic vessels; therefore, it is upregulated in the vasculature of solid tumors, while expression is low in quiescent vasculature [8387]
Tumor endothelial marker 1 (TEM1); endosialin or CD248 One of the most abundantly expressed proteins on tumor vasculature and tumor stroma of human tumors Expression is variable among tumor types; however, this protein can reportedly be expressed on endothelial cells, pericytes, and/or fibroblasts of human and animal tumors [67, 8893]