Study On The Effects Of Bortezomib To Myelodysplastic Syndrome Cells

Myelodysplastic Syndrome(MDS) is a group of monoclonal hematopoietic stem cell disorders characterized by cytopenias,transfusion-dependence and progression to AML.While conventional chemotherapy and novel agents,like proteasome inhibitor,is effective on palliating the disease,and even prolonging survival,this disease is generally regarded as incurable.PS-341 was the first of Proteosome inhibitors on the clinical research,which has been used for multiple myeloma.Recent studies showed that PS-341 possessed potential anti-tumor properties,and induced apoptosis of MDS cell lines.In the present study the cell line of MDS were Used in our experiment.We investigated the therapeutic effect and mechanisms of PS-341 against human MDS cell line MUTZ-1,which Provides an experimental evidence of PS-341 for clinical treatment of MDS.First of all,we used MTT assay to examine the effects of different concentrations of PS-341 on the growth of MUTZ-1 cells.The results indicated that cell viability in the presence of PS-341 decreased in a dose-dependent manner.The inhibitory rates of cell growth were positively correlated with PS-341 concentrations(P＜0.01).The growth-inhibitory IC₅₀ values were56.08ng/ml,34.18ng/ml,21.16ng/ml after the treatment of PS-341 for 24,48,72 hours,respectively.Then,in order to investigate whether apoptosis is associated with the antitumor activity of PS-341 in human MUTZ-1 cells,we observed the cell morphology using Wright-Giemsa staining,evaluated the exposure of phosphatidylserine(PS) on MUTZ-1 cells after double staining with fluorescein isothiocyanate(FITC)-labeled annexin V and propidium iodide(PI),and analyzed the cell cycle using propidium iodide staining.We found typical apoptotic morphology such as pyknosis and apoptotic body after MUTZ-lcells were exposed to PS-341 for 24小时.Apoptosis induced by PS-341 was also confirmed using Annexin V and PI staining to detect externalization of PS on the cell membrane in a dose-dependent manner.To further investigate the mechanism possibly involved in PS-341-induced MUTZ-1 cells' apoptosis,we used western-blot to assay the protein expression of Bcl-2 family members.Bcl-2 and Mcl-1 protein level were down-regulated and Bax,PARP,Caspase-3 protein level was up-regulated when 20-80ng/ml PS-341 was treated.The results indicated that PS-341 induced-apoptosis is mediated,at least in part,t小时ough changing the ratio of anti- and proapoptotic Bcl-2 family proteins.We further examined whether PS-341 could enhance the growth inhibitory effect of As₂O₃.MUTZ-1 cells were cultured for 24 hours with As₂O₃(0.25～21μmol/l) in media with or without concentrations of PS-341(10～80ng/ml).PS-341 enhances growth inhibition mediated by As₂O₃,as analyzed by MTT assay.In conclusion,PS-341 can inhibit the viability of human MDS cell line(Mutz-1) in a dose-dependent manner.And this effect is induced by apoptosis.PS-341 triggers the apoptosis of MDS cell line,at least in part,t小时ough the mitochondrial pathway. PS-341 also overcomes the conventional drug resistant of MDS cells,and enhances cytotoxicity of proteasome inhibitor PS-341.