Abstract
Purpose:
Bevacizumab is taken up into RPE cells and is intracellularly found for at least seven days. In this study, we investigate Bevacizumab uptake and intracellular localisation of Bevacizumab at different time points in RPE cells.
Methods:
For this study, RPE cell line Arpe19 and primary porcine RPE cells, passage 2, were used. Cells were treated once with Bevacizumab and intracellular Bevacizumab was investigated after various time periods (1 h - 7 d). For the detection of intracellular Bevacizumab, Western blot and immunofluorescence was utilized. For intracellular localization, antibodies against Rab5 (early endosome), Rab7 (late endosome), Lamp2 (lysosome) and microtubuli were used. Actin was stained using Phalloidin.
Results:
Bevacizumab is abundantly found in porcine RPE cells and Arpe19 cells as detected in immunofluorescence and Western blot. After 1 h and 4 h of stimulation, Bevacizumab is primarily located close to the cell membrane and can partly be found in close proximity to or colocalizing with Rab 5, indicating that sections of Bevacizumab are taken up into early endosomes. During 1 day to 5 days after Bevacizumab challenge, intracellular Bevacizumab displays a net-like pattern. After 7 d of Bevacizumab challenge, the pattern intracellular Bevacizumab displays becomes more diffuse. Colocalization with microtubule can hardly be seen, while Bevacizumab is found in close proximity to or colocalizing with actin filaments, suggesting an actin-mediated intracellular transport. Colocalization with Lamp2 is rarely found, suggesting that Bevacizumab is not degraded in lysosomes.
Conclusions:
Bevacizumab displays a distinct, time dependent localization in RPE cells. The pattern suggests a controlled intracellular transport via actin filaments. Taken-up Bevacizumab does not seem to be transported into the lysosomal pathway and does not seem to be intracellularly degraded.
Keywords: 701 retinal pigment epithelium •
493 cytoskeleton •
748 vascular endothelial growth factor