OBJECTIVETo investigate the mechanism underlying the curcumin-induced apoptosis of nasopharyngeal carcinoma (NPC) cell line NCE cells.

METHODSThe characteristics of apoptosis were identified by observation acridine orange and ethidium bromide stains, ultrastructure assay, DNA fragmentation assay and TdT-mediated dUTP nick end labeling method (TUNEL). Mitochondrial membrane potential (delta psi m), activity of caspase-3, cytosol cytochrome C and expression of gene Fas were determined by flow cytometry (FCM), Western Blot and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTSSeveral evidences of apoptosis were obtained from curcumin-treated NCE cells by acridine orange and ethidium bromide stains, ultrastructure identification, DNA fragmentation assay and TUNEL staining. And the mean TUNEL-positive rates increased significantly at the 3 different time points (12 h, 24 h and 48 h; 25.6%, 40.3% and 54.5%, respectively). In the curcumin-treated-groups, delta psi m altered significantly and the positive rates increased in a time-dependent manner. At the 3 different time points, the mean positive rates were 26.8%, 42.3% and 68.2%, respectively. When caspase-3 activity was detected, 80.5% cells presented proteases activities after 12 h incubation with curcumin. Western Blot analysis showed that cytoplasmic cytochrome C increased significantly after incubation with curcumin. Flow cytometry and RT-PCR analysis showed that curcumin could up-regulate the Fas expression in time-depended manner , the positive rates of Fas protein increased from 33.6% to 89.9%.

CONCLUSIONSCurcumin induced apoptosis of NCE cells both through mitochondria-dependent pathway and death receptor pathway.