AIM: To explore the effect of pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, on the proliferation and apoptosis of human multiple myeloma U266 cells and its mechanisms.METHODS: The U266 cells were treated with PDTC at different concentrations (0, 25, 50, 100 and 200 μmol/L) in vitro.The growth inhibitory rate of the U266 cells was detected by CCK-8 assay and cell counting.The cell cycle of the U266 cells was determined by flow cyto-metry, and the apoptosis was examined by flow cytometry with Annexin V-FITC/PI staining.The effect of PDTC on the expression of DNA methyltransferase 1 (DNMT1) at mRNA and protein levels was measured by RT-qPCR and Western blot, respectively.The effects of PDTC on the protein levels of NF-κB (P65), DNMT1, Bcl-2, cyclin D1, cleaved caspase-3 and cleaved caspase-8 were determined by Western blot.RESULTS: The protein level of NF-κB (P65) was decreased after treatment with PDTC for 48 h or 72 h.PDTC inhibited the proliferation of U266 cells in both dose-and time-dependent manners.After treatment with PDTC for 48 h, the percentage of U266 cells in G2 phase increased compared with control group (P<0.05).PDTC induced the apoptosis of U266 cells in a dose-dependent manner.The expression of DNMT1 at mRNA and protein levels decreased (P<0.05).The results of Western blot showed that the expression of Bcl-2 in PDTC groups decreased, while the protein levels of cyclin D1, cleaved caspase-3 and cleaved caspase-8 were higher than those in control group (P<0.05).CONCLUSION: The NF-κB inhibitor PDTC inhibits the proliferation of U266 cells by inducing cell apoptosis.It may be related to the down-regulated expression of DNMT1, cell cycle arrest and activation of the apoptotic pathways.