Effect of pyridoxine or cobalamin supplementation on apoptosis and cell cycle progression in a human glioblastoma cell line

Glioblastoma is the most aggressive type of brain tumor, with current therapies failing to significantly improve patient survival. Vitamins have important effects on cellular processes that are relevant for tumor development and progression.The present study explored the effect of pyridoxine or cobalamin supplementation on the viability and cell cycle progression of human glioblastoma cell line U-87 MG.Cell cultures were treated with increasing concentrations of pyridoxine or cobalamin for 24-72 h. After supplementation, cell viability and cell cycle progression were assessed by spectrophotometry and flow cytometry. Analysis of Bcl-2 and active caspase 3 expression in supplemented cells was performed by western blot.The results show that pyridoxine supplementation decreases cell viability in a dose and time dependent manner. Loss of viability in pyridoxin-supplemented cells is probably related to less cell cycle progression, higher active caspase 3 expression and apoptosis. In addition, Bcl-2 expression did not appear to be altered by vitamin supplementation, but active caspase 3 expression was significantly increased in pyridoxine-, but not cobalamin-supplemented cells, furthermore, cobalamin inhibited the pyridoxine cytotoxicity in the cell viability assay when combined.The results suggest that pyridoxine supplementation promotes apoptosis in human glioblastoma-derived cells and may be useful to enhance the effect of cytotoxic therapies in vivo.