Protease Nexin-1 (PN1) Promotes The Sensitivity Of Acute Myelocytic Leukemia (AML) To Cytarabine By Inhibiting X-Linked Inhibitor Of Apoptosis Protein (XIAP )

Objective:To investigate the expression and biological activity of protease nexin-1(PN1) in acute myelocytic leukemia(AML) cells and verify the inhibition of PN1 on X-linked inhibitor of apoptosis protein(XIAP) in AML cells. And then to test and verify that PN1 can promote the sensitivity of AML cells to cytarabine by inhibiting XIAP, providing new idea on and theoretical basis for resolution of the cytarabine resistance in AML therapy.Methods: AML cells were transfected with a PN1 expression plasmid or si RNA against PN1 respectively by electrotransfection or lipofection transfection. Real-time PCR and immunoblotting were used to detect the expression of PN-1 and XIAP and PI-Annexin V double staining flow cytometry and Caspase-3 Activity kits for the apoptosis in AML cells; CCK8 kits were used to detect the proliferation and determine the optimal concentration and optimal time for the effect on AML cells of cytarabine. The apoptosis was detected to evaluate the sensitivity of AML cells to cytarabine and the expression of PN1 and XIAP to verify the mechanism in AML cells after treatment with cytarabine and transfection of PN1 expression plasmid.Results: Pn1 differently expressed in all the AML cell lines tested. The apoptosis of AML cells increased after up-regulation of PN1, so did both the RNA and protein expression of XIAP in AML cells. The effect was contrary when downregulation of PN1. Cytarabine induced the XIAP expression in AML cells, which was reversed by combining with transfection of PN1 expression plasmid that increased the apoptosis consequentely.Conclusion: PN1 induced the apoptosis of AML cells and was the natural inhibitor of XIAP in AML cells. PN1 promoted the sensitivity of AML cells to cytarabine by inhibiting XIAP expression in AML cells.