Objective: To investigate the mechanism underlying the curcumin-induced apoptosis of nasopharyngeal carcinoma (NPC) cell line NCE cells.
Methods: The 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).
Results: Several 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%.
Conclusions: Curcumin induced apoptosis of NCE cells both through mitochondria-dependent pathway and death receptor pathway.