SMAD3 and nasopharyngeal carcinoma: Furthremore, its expression in NPC was maintained by nerve growth factor (NGF) through p75NTR and extracellular signal-regulated kinase (ERK) signaling pathway [11], while transforming growth factor (TGF)-β, the classical degeneration inducer of NPC, inhibited its expression via SMAD3, a transcriptional repressor [12].