SERPINF1 and nasopharyngeal carcinoma: The inhibition of VEGF/PEDF ratio in NPC cells through disrupting HIF-1α expression using siRNA strategy not only demonstrated nicotine-mediated increase of VEGF/PEDF ratio is HIF-1α-dependent, but also showed HIF-1α’s central role in regulating the VEGF/PEDF ratio stimulated by nicotine in human NPC cells.