SERPINF1 and nasopharyngeal carcinoma: Similarly, treatment of NPC cells with nicotine (10 μM) for 8–32 hours also promoted the release of VEGF protein, but reduced the release of PEDF protein in cell culture media (Fig. 5C), resulting in a significant increase of the VEGF/PEDF ratio at protein level in cell culture media in a time-dependent manner (Fig. 5D).