TP53 and nasopharyngeal carcinoma: However, this TP53 aberration in NPC is also indirectly induced by LMP1 via the activation of NF-kB and activator protein 1 (AP-1) signalling, or the overexpression of its negative regulator, E3 ubiquitin-protein ligase murine double minute 2 (MDM2) [131, 232].