Proteasome inhibitors sensitize ovarian cancer cells to paclitaxel induced apoptosis

Abstract

To explore the sensitivity of ovarian cancer cell line SKOV3 to paclitaxel, proteasome inhibitors, bortezomib, and their combination. The methyl thiazolyl tetrazolium (MTT) assay was applied to examine the cell viability after treatment. The annexin V-propidium iodide apoptosis detection kit was used to determine the apoptosis rate of different groups. Western blot assay was used to evaluate the expression levels of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3 beta (GSK-3beta). In MTT assay, the cell viability ratios of the combination group at serial time points from 12, 24, 36, 48 and 72 hours were (65.2 +/- 5.8)%, (58.3 +/- 14.4)%, (35.3 +/- 5.0)%, (19.2 +/- 1.5)%, and (11.4 +/- 2.5)%, which were significantly lower than those of the paclitaxel group (P < 0.05). After drug treatments, apoptosis rates of paclitaxel group, bortezomib group and the combination group were (14.7 +/- 0.5)%, (15.1 +/- 0.8)% and (20.5 +/- 0.7)% respectively. The rate of the combination group was significantly higher than that of non-treated group and paclitaxel group (P < 0.05). Western blot assay showed the changes in expression levels of phosphorylated AKT and GSK-3beta, which were decreased significantly after paclitaxel and bortezomib combination treatment [(3.2 +/- 0.8)%, (19.3 +/- 0.4)%; P < 0.05]. The lethal effect of paclitaxel on tumor cells could be increased significantly by its combination with proteasome inhibitors, bortezomib. The AKT/GSK-3beta signaling pathway plays an important role in the molecular mechanism of the combination treatment.