Hsp90 inhibitor SY-016 induces G2/M arrest and apoptosis in paclitaxel-resistant human ovarian cancer cells.

The aim of the present study was to evaluate the in vitro effect of a heat shock protein (Hsp)90 inhibitor, SY-016, on the paclitaxel (PTX)-resistant human ovarian cancer cell line OVCAR-3PTX, and explore its mechanism of apoptosis. In the present study, SY-016 was used in combination with PTX to determine its effect on the cell proliferation and apoptosis of OVCAR-3PTX cells. The drug-resistant tumor cells were established in vitro by stepwise sequential exposure to increasing concentrations of PTX. The cell viability and cell cycle distribution were measured by MTT assay and flow cytometric analysis, respectively. The induction of apoptosis was measured by caspase-3 activity, DNA fragmentation and western blot analyses. The cell viability significantly decreased following treatment with PTX and SY-016 as compared with either drug alone. The DNA fragmentation assay revealed an induction of apoptosis. The results from the flow cytometric analysis revealed an increase in the percentage of cells in the G2/M phase. Downregulation of B-cell lymphoma (Bcl)-2, X-linked inhibitor of apoptosis protein, survivin, Akt, nuclear factor-κB and cyclin-dependent kinase 4, as well as upregulation of Bcl-2-associated X protein, were observed. SY-016 may contribute to the induction of apoptosis in OVCAR-3PTX cells. These results suggest that SY-016 in combination with PTX may be a beneficial chemotherapeutic strategy, particularly in patients with tumors refractory to PTX.