25-Hydroxycholesterol Induces Death Receptor-mediated Extrinsic and Mitochondria-dependent Intrinsic Apoptosis in Head and Neck Squamous Cell Carcinoma Cells

Abstract

Background/Aim: Oxysterol plays important physiological roles in diverse biological processes including apoptosis. However, the mechanisms underlying oxysterol-induced apoptosis remain unknown. 25-hydroxycholesterol (25-HC) is an oxysterol synthesized by cholesterol 25-hydroxylase from cholesterol during sterol metabolism. The aim of present study was to investigate 25-HC-induced apoptosis and associated signalling pathways in FaDu cells, which is originated form human head and neck squamous cell carcinoma cells. Materials and Methods: 25-HC-induced apoptosis was investigated by cell cytotoxicity assay using MTT, cell viability assay using cell LIVE/DEAD cell viability assay, haematoxylin & eosin staining, nuclear staining, fluorescence-activated cell sorting, western blotting using specific antibodies associated with extrinsic and intrinsic apoptosis pathways, and caspase-3/-7 activity assay in FaDu cells. Results: 25-HC dose-dependently decreased the viability of FaDu cells and up-regulated apoptotic events, such as alteration in morphology, and nuclear condensation. Flow cytometric analysis showed an increase in apoptotic population upon 25-HC treatment, suggesting that 25-HC induces apoptosis in FaDu cells. Moreover, 25-HC-induced apoptosis in FaDu cells was dependent on the activation of caspases by Fas antigen ligand-triggered death receptor-mediated extrinsic pathway and mitochondria-dependent intrinsic pathway via mitogen activated protein kinases. Conclusion: Cholesterol-derived oxysterol, 25-HC has potential anti-cancer function in FaDu cells and may have potential properties for the discovery of anti-cancer agents.