Abstract: Objective To investigate the effects of BLIMP1 gene silencing by RNA interference on the proliferation and apoptosis of multiple myeloma (MM) cell line NCI-H929 and related mechanisms. MethodsNCI-H929 cells were transfected with a lentiviral vector or a control vector. Then, the levels of BLIMP1 mRNA and protein were detected by RT-PCR and Western blotting. The proliferation of the above cells was detected by CCK-8 assay. Cell apoptosis was detected by Annexin V/PI double staining flow cytometry. The levels of XBP1, IRE1α and CHOP mRNA and protein were detected by RT-PCR and Western blotting. ResultsAfter transfection of BLIMP1 mRNA, the levels of BLIMP1 mRNA and protein were markedly suppressed (P<0.05). The shRNA/BLIMP1 group showed suppressed proliferation of NCI-H929 cells at 24, 48 and 72 h, compared with the shRNA/con and control groups. The cell apoptotic rate was (10.87±1.79)% in the shRNA/BLIMP1 group, which was higer than (5.57±0.87)% for the shRNA/con group and (4.90±0.57)% for the control group (P<0.01). BLIMP1 shRNA up- regulated the expression of CHOP, but down- regulated the expression of XBP1 and IRE1α. ConclusionsBLIMP1 gene silencing may inhibit the proliferation of NCI-H929 cells through suppressing unfolded protein response (UPR) by down-regulation of XBP1 expression.