A Novel Compound XN51 Inhibits Acute Myeloid Leukemia Cells Through Blocking Hsp90 Chaperone Function

Aim To investigate the relationship between the effect of the novel compound XN51 on acute myelocytic leukemia(AML) cells and the heat shock protein 90(Hsp90) chaperone function in AML cells.Methods(1) To test the proliferation inhibition effect of XN51 on AML cells using trypan blue staining and MTT methods.(2) To test the effect of XN51 on cell cycle process, mitochondrial membrane potential(MMP) and cell apoptosis ratio in AML cells by Flow cytometry.(3) To exame the effect of XN51 on protein level by Westernblot.(4) To test the effect of XN51 on Hsp90 ATPase activity by malachite green ammonium phosphomolybdate- inorganic phosphorus assay in vitro.(5) To detect the expression level of Hsp90’s client proteins Akt and CDK2 after XN51 treatment by Westernblot.Results(1) XN51 could obviously inhibite the proliferation of AML cells, and the proliferation inhibition activity was nearly 100 folds greater than that of the Nov.(2) XN51 could induce cell cycle S phase arrest, decrease mitochondrial membrane potential and increase the apoptosis ratio of AML cells. Weternblot data illustrated that XN51 could upregulate the protein level of Cleaved parp, Cleaved Caspase3 and Cleaved Caspase9 but downregulate expression level of p- Akt and CDK2.(3) XN51 could combine with Hsp90 in vitro, with Hsp90 endogenous fluorescence statically quenching, resulting in inhibition of Hsp90 ATPase activity; XN51 leaded to the degradation of Akt protein by proteasome pathway because of forming abnormal and instability molecule structure without assistance of heat shock protein 90 molecular chaperone, resulting in proliferation inhibition of AML cells; In the same way, CDK2 protein could not form the correct and stable conformation structure leading to AML cells cycle arrest in S phase; Additionally,XN51 induced expression of Hsp70 after inhibiting the chaperone function of Hsp90.Conclusion XN51 inhibited the activity of the Hsp90 molecular chaperone through combining with Hsp90 statically, resulting in dysfunction and degradation of Akt and CDK2 proteins without forming correct and stable conformation, finally induced AML cell cycle arrest in S phase, increased the apoptosis proportion of AML cells, and inhibited the proliferation of AML cells.