Previous studies showed that Bak activation could inhibit cell growth in hepatocellular carcinoma, prostate cancer and glioma [34–36], and Bak deletion could stimulate gastric epithelial proliferation [37].We here found that upregulation of Bak in MCF-7 cells dramatically arrested the cell cycle during G2/M phase and sensitized these cells to Taxol by inhibiting proliferation and promoting apoptosis in vitro. The gene discussed is BAK1; the disease is central nervous system cancer.