PTGS2 and nasopharyngeal carcinoma: Since the p38 MAPK and JAK2/STAT3 signaling pathways are known to be upstream regulators of COX-2 in cancer cells (26, 45), the activation of the ERK/MAPK and JAK2/STAT3 pathways by COX-2 may form a positive feedback loop to promote the survival of NPC cells.