Artesunate, as a HSP70 ATPase activity inhibitor, induces apoptosis in breast cancer cells

The present study aims to evaluate the inhibitory effects of artesunate (a semi-synthetic derivative of artemisinin) on HSP70 and Bcl-2 expression in two breast cancer cell lines, 4T1 and MCF-7. In addition, to determine in vitro inhibitory effect of artesunate against the ATPase activity of purified recombinant HSP70, it was tested in a carbonic anhydrase refolding assay with purified HSP70. Our results demonstrated that the artesunate not only induced apoptosis but also lead to the inhibition of HSP70 ATPase activity the in vitro (P < 0.001). The extent of HSP70 refolding inhibition increased with increasing μM concentrations of artesunate. Incubation of HSP70 with 50 μM artesunate showed significant inhibition of refolding activity by 38%. The IC50 values of artesunate for 4T1 cells, were lower than MCF-7 cells, indicating the higher sensitivity of the triple-negative phenotype. Furthermore, artesunate significantly down-regulated the expression of Bcl-2 and HSP70 while enhancing the expression of cleaved caspase-9 in MCF-7 and 4T1 cells. It also induced caspase-9 activity at 18 h in a dose-dependent manner in two breast cancer cell lines. Generally, our results show that the artesunate induces caspase-dependent apoptosis through the inhibition of HSP70 expression.