Oroxylin A induces G<SUB>2</SUB>/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells

We reported previously that oroxylin A, a natural product isolated from Scutellariae Radix, was a potent apoptosis inducer of human hepatoma HepG2 cells. In this study, cell-cycle arrest of BGC-823 human gastric carcinoma cells caused by oroxylin A has been investigated. Based on our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay and flow cytometric analysis, treatment of BGC-823 cells with growth suppressive concentrations of oroxylin A caused an irreversible arrest in the G2/M phase of the cell cycle. Western blot analysis demonstrated that oroxylin A-induced cell-cycle arrest in BGC-823 cells was associated with a significant decrease in cdc2/p34, cyclin B1 and cyclin A expression. In addition, oroxylin A-treated cells decreased the expression of Cdk7, which was responsible for the low expression of M phase promoting factor (cyclin B1/Cdc2). The results suggested that oroxylin A induced G2/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells.