To further validate the role of nicotine in regulating VEGF/PEDF ratio through HIF-1α signaling, we blocked the expression of HIF-1α proteins by transfecting NPC cells with an HIF-1α-specific siRNA (si-HIF) and evaluated their effects on nicotine-mediated promotion of the VEGF/PEDF ratio. Here, VEGFA is linked to nasopharyngeal carcinoma.