CASP9 and nasopharyngeal carcinoma: Cells of different NPC cell lines and cell line NP69 were treated for 72 h with 1,000 U/ml IFNβ in the presence or absence of the pan-caspase inhibitor Z-VAD-fmk, the caspase-8-inhibitor Z-IETD-fmk or the caspase-9 inhibitor Z-LEHD-fmk.