Apoptosis induced by ursodeoxycholic acid in human melanoma cells through the mitochondrial pathway

Ursodeoxycholic acid (UDCA) is a type of hydrophilic bile acid extracted from animal bile with a wide range of biological functions. The present results demonstrated that UDCA could effectively inhibit the proliferation of two human melanoma cell line (M14 and A375) with time- and concentration-dependence. Following exposure to various concentrations of UDCA, M14 cells exhibited typical morphological changes and weaker ability of colony forming. Flow cytometry analysis demonstrated that UDCA could induce a decrease of mitochondrial membrane potential and an increase in reactive oxygen species (ROS) levels in M14 cells. The cell cycle was arrested in the G2/M phase, which was confirmed by the decrease of cyclin-dependent kinase 1 and cyclinB1 at the protein level. However, when M14 cells were treated with UDCA and Z-VAD-FMK (caspase inhibitor) synchronously, the apoptosis rate of the cells was reduced significantly. In addition, it was demonstrated that UDCA induced apoptosis of human melanoma M14 cells through the ROS-triggered mitochondrial-associated pathway, which was indicated by the increased expression of cleaved-caspase-3, cleaved-caspase-9, apoptotic protease activating factor-1, cleaved-poly (ADP-ribose) polymerase 1 and the elevation of B cell lymphoma-2 (Bcl-2) associated X protein/Bcl-2 ratio associated with apoptosis. Therefore, UDCA may be a potential drug for the treatment of human melanoma.