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T. H. Tezel, Q. Zeng, S. Schaal, H. J. Kaplan; Bevacizumab (Avastin®) Differs From Ranibizumab (Lucentis®) in Its Binding Affinity to Retinal Pigment Epithelium (RPE) and Vascular Endothelium Cell Membranes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4955.
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To determine and characterize the differences in the binding of bevacizumab and ranibizumab to human RPE and human vascular endothelium cell membranes.
The expression of VEGF and the receptor for Fc (FcR), on human umbilical vein endothelial cells (HUVEC), ARPE-19 and primary human RPE (phRPE) cell membranes was determined under normoxic (21% O2) and hypoxic (10% O2/10 nM, PMA for 12 hours) conditions using Western blotting and immunohistochemistry. Effect of bevacizumab (625 µg/ml) and ranibizumab (125 µg/ml) on cell viability and complement activation was determined with FACS analysis. Confocal microscopy and iC3b ELISA was used to confirm the results. VEGF-expressing SKOV cells were used as a positive control.
phRPE, ARPE-19 and HUVECs express VEGF on cell membrane; however Fc expression was observed only on phRPE and HUVEC. Hypoxia increases membrane-bound VEGF expression in HUVEC (2.3±0.6x) and RPE (2.6±0.4x) cells, but FcR expression remained unchanged. Bevacizumab was able to bind to HUVEC and RPE cell membranes resulting in RPE cell death (3.8%), whereas ranibizumab bound weakly on RPE without causing cell death. Bevacizumab binding to HUVEC cells was completely blocked by FcR-antibodies indicating that its binding is mediated through Fc-FcR interaction. Additionally, bevacizumab binding to RPE cells increased in hypoxia along with an increase in membrane-bound VEGF expression.
Bevacizumab binds to different ligands on HUVEC (FcR) and human RPE (membrane-bound VEGF) cells. Binding of bevacizumab is associated with complement activation and cell death. In contrast, Ranibizumab can only weakly bind to RPE and does not activate complement
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