Western blotting protocol was performed as described previously 25 (link). Primary antibodies included the mouse monoclonal antibodies anti-APE1 (1:5000), VEGF (1:500), FGF2 (1:1000), TGFβ (1:50) and anti-β-Actin (1:2000), all of the primary antibodies were purchased from Abcam. Visualization was performed using Bio-Rad ChemiDocTM XRS system (Hercules, CA, USA) with enhanced-chemiluminescence substrate and the blots were analyzed using Image Lab 3.0 (BioRad, Hercules, CA, USA). Protein level was normalized to the matching densitometry values of the internal control β-actin.