Genistein induces apoptosis in vitro and has antitumor activity against human leukemia HL-60 cancer cell xenograft growth in vivo

Genistein, a major isoflavone compound in soybeans, has been shown to have biological activities including anti-cancer activates. In the present, we investigated the anti-leukemia activity of genistein on HL-60 cells in vitro. The percentage of viable cell, cell cycle distribution, apoptotic cell death, reactive oxygen species (ROS), and Ca2+ production and the level of Delta psi(m) were measured by flow cytometric assay. Cell apoptosis and endoplasmic reticulum (ER) stress associated protein expressions were examined by Western blotting assay. Calpain 1, GRP78, and GADD153 expression were measured by confocal laser microscopy. Results indicated that genistein-induced cell morphological changes, decreased the total viable cells, induced G(2)/M phase arrest and DNA damage and fragmentation (cell apoptosis) in HL-60 cells. Genistein promoted ROS and Ca2+ productions and decreased the level of Delta psi(m) in HL-60 cells. Western blotting assay demonstrated that genistein increased ER stress-associated protein expression such as IRE-1 alpha, Calpain 1, GRP78, GADD153, caspase-7, caspase-4, and ATF-6 alpha at 20-50 mu M treatment and increased apoptosis associated protein expression such as pro-apoptotic protein Bax, PARP-cleavage, caspase-9, and -3, but decreased anti-apoptotic protein such as Bcl-2 and Bid in HL-60 cells. Calpain 1, GRP78, and GADD153 were increased in HL-60 cells after exposure to 40 mu M of genistein. In animal xenografted model, mice were intraperitoneally injected with genistein (0, 0.2, and 0.4 mg/kg) for 28 days and the body weight and tumor volume were recorded. Results showed that genistein did not affect the body weights but significantly reduced the tumor weight in 0.4 mg/kg genistein-treated group. Genistein also increased the expressions of ATF-6 alpha, GRP78, Bax, Bad, and Bak in tumor. In conclusion, genistein decreased cell number through G(2)/M phase arrest and the induction of cell apoptosis through ER stress- and mitochondria-dependent pathways in HL-60 cells and suppressed tumor properties in vivo.