Protosappanin B promotes apoptosis and causes G(1) cell cycle arrest in human bladder cancer cells

The aim of the study was to investigate the effects of protosappanin B on the proliferation and apoptosis of bladder cancer cells. The effects of protosappanin B (12.5, 25, 50, 100, or 200 μg/mL, 48 h) on proliferation of SV-HUC-1, T24 and 5637 cells was assessed using the MTT assay. The effects of protosappanin B (100, 150, 200, 250, or 300 μg/mL, 48 h) on cell apoptosis and cell cycle were analyzed using flow cytometry. T24 and 5637 cells treated with 200 µg/mL protosappanin B showed morphological changes (shrinkage, rounding, membrane abnormalities, and reduced adhesion), but protosappanin B had no proliferation arrest effect on SV-HUC-1 cells. Protosappanin B caused concentration-dependent inhibition of cell growth, with IC(50) of 82.78 µg/mL in T24 cells and 113.79 µg/mL in 5637 cells. Protosappanin B caused concentration-dependent increases in T24 and 5637 cell apoptosis (100–300 µg/mL). The effects of protosappanin B on the cell cycle in both cell types was G(1) arrest with reductions in the proportion of S-phase cells and proliferation index. A proteomics analysis showed that protosappanin B modulated a number of genes involved in the cell cycle. In conclusion, protosappanin B inhibits the proliferation and promotes the apoptosis of T24 and 5637 human bladder cancer cells in a concentration-dependent manner, possibly via interference with cell cycle regulation, preventing G(1)-to-S transition.