Combination this with the results that mutation of either the NF-κB or the AP-1 motif could not completely abolish the iEκ activity in NPC cells as well as previous reports that several additional functional motifs are located within the iEκ [33,34], suggested that the variety of nuclear factors that can bind to the iEκ may result in complex regulatory pathways. Here, FOS is linked to nasopharyngeal carcinoma.