Protease Nexin-1 May Increase The Sensitivity Of Multiple Myeloma Cells To Bortezomib

Objective:To detect the expression of protease nexin-1(PN1)in bone marrow of patients with multiple myeloma(MM)patients,to define the apoptosis effect of PN1 in MM cell lines.To detect the impact of PN1 and bortezomib,respectively or together,on X-linked inhibitor of apoptosis protein(XIAP)and NF-?B pathway,and further explore whether PN1 can improve the sensitivity of MM cells to bortezomib.Methods: Immunohistochemistry was used to detect PN1 expression in MM patients' bone marrow and normal bone marrow;CCK8 kits were used to confirm the inhibitory effect of bortezomib on MM cell proliferation and to measure the optimal concentration in MM cells;MM cells were transfected with a PN1 plasmid or siRNA against PN1 by electrotransfection or lipofection;Annexin V-PI double labeling and flow cytometry were used to test the apoptosis after up-regulation of PN1 and treatment of bortezomib or combined treatment;Real-time PCR and Western blot were used to detect the expression of PN1?XIAP?p-XIAP and NF-?B pathway members in MM cells,which was to investigate whether PN1 can increase the sensitivity of MM cells to bortezomib.Results: PN1 expressed significantly lower in MM bone marrow than normal bone marrow;Up-regulation of PN1 increased apoptosis,decreased expression of XIAP;while the effect was contrary to results of PN1 downregulation.When treated with bortezomib,the activation of NF-?B pathway was inhibited and expression of XIAP was increased in MM cell lines(U266 and RPMI8226).However,by combining with up-regulation of PN1,the XIAP and p-XIAP expression induced by bortezomib was reversed,and the activation of NF-?B pathway was synergistically suppressed.Conclusion: In MM cells,PN1 inhibited NF-?B activation pathway synergistically with bortezomib and reduced the expression of XIAP and p-XIAP induced by bortezomib,thereby increasing the sensitivity of MM cells to bortezomib.