Abstract： Objective To investigate the effect of miR-424 on the proliferation and apoptosis of multiple myeloma(MM)cells by targeting the F-box and WD repeat domain containing 7(FBXW7).Methods Real-time fluorescence quantitative PCR(RT-qPCR)experiment was ap-plied to detect the expression levels of miR-424 and FBXW7 in human normal bone marrow plasma cells and MM cell lines MM.1S,RPMI 8226,U266.U266 cells were cultured in vitro and random-ly separated into 5 groups:control group,miR-424 inhibitor group,FBXW7 overexpression group,negative control group,miR-424 inhibitor+FBXW7 knockdown group.Edu staining and TUNEL staining were applied to detect the cell proliferation and apoptosis,respectively.Western blotting as-say was applied to detect the expression levels of proliferation related proteins(Cyclin D1,PC-NA),apoptosis related proteins(Bax,Bcl-2),and FBXW7 protein.A nude mouse model of mul-tiple myeloma transplantation was constructed by subcutaneous inoculation of transfected U266 cells in the right axilla of nude mice,the growth of the transplanted tumors were detected and the trans-planted tumor volume was compared on the 21st day.Dual luciferase reporter experiment was applied to verify the targeted regulatory effect of miR-424 on FBXW7 in U266 cells.Results In comparison with those in the normal human bone marrow plasma cells,the expression of miR-424 in the MM.1S,RPMI 8226,and U266 cells were increased(P<0.05),while the expression of FBXW7 mRNA were decreased(P<0.05).In addition,when compared with the control group,the miR-424 inhibitor group and the FBXW7 overexpression group showed decreased cell prolifera-tion rate,lower protein expression levels of Cyclin D1,PCNA and Bcl-2,and decreased transplan-ted tumor volume on the 21st day(P<0.05),and increased apoptosis rate,FBXW7 mRNA and protein expression levels,and Bax protein expression level(P<0.05).There was no significant difference in the indicators in cells of the negative control group(P>0.05).Moreover,when com-pared with the miR-424 inhibitor group,the miR-424 inhibitor+FBXW7 knockdown group exhibi-ted increased cell proliferation rate,Cyclin D1,PCNA and Bcl-2 protein expression,and trans-planted tumor volume on the 21st day(P<0.05),and decreased apoptosis rate,FBXW7 mRNA and protein expression levels,and Bax protein expression level(P<0.05).It was also observed that miR-424 was able to targetly downregulate FBXW7 expression in U266 cells.Conclusion Down-regulation of miR-424 can inhibit MM cell proliferation and growth in nude mice,and pro-mote the apoptosis by up-regulating FBXW7 expression.