NPC1 and cancer: It is believed that the diminished PEDF expression in various tumor types may in part account for increased malignant characteristics during tumor progression.40 Possible regulatory mechanisms underlying the changes in PEDF expression during transforming and malignant progression of cancer are rarely studied, which include transcriptional regulation, hypoxia-mediated regulation and posttranslational modifications.41 Our findings suggested that PEDF is suppressed by miRNAs in NPC, indicative of a novel mechanism of PEDF regulation (Figure 6).