Effects Of NF-?B On Proliferation And DNMT1 Gene Expression In Multiple Myeloma Cells

AIM: To explore the effects of nuclear factor kappa B(NF-?B)on proliferation and DNA methyltransferase 1(DNMT1)gene expression in multiple myeloma(MM)U266,RPMI8226 cells.METHODS: MM U266,RPMI8226 cells were treated with pyrrolidine dithiocarbamate(PDTC)at different concentrations(0,25,50,100,200 ?mol/L)in vitro.Morphological changes of cells were observed under light microscope.The growth inhibition rate of U266,RPMI8226 cells was detected by Cell Counting Kit-8(CCK-8)assay.The cell cycle of the cells was determined by flow cytometry and the apoptosis was examined by flow cytometry with annexin-V FITC/PI staining.The effect of PDTC on the expression of DNMT1 at mRNA and protein levels was measured by quantitative real-time PCR(qPCR)and Western blot respectively.The effects of PDTC on the protein levels of NF-?B(P65),DNMT1,Bcl-2,CyclinD1,cleaved caspase-3 and caspase-8 were determined by Western blot.The effects of decitabine(DAC)on the protein levels of NF-?B(P65)and DNMT1 were determined by Western blot too.RESULTS: The protein level of NF-?B(P65)was decreased aftertreated with PDTC for 48 h.PDTC inhibited the proliferation of U266,RPMI8226 cells in both dose-and time-dependent manners.PDTC induced the apoptosis of U266 cells in a dose-dependent manner.The results of Western blot showed that the expression of Bcl-2 decreased,while the protein levels of CyclinD1,cleaved caspase-3 and caspase-8 were higher than those in control group(P<0.05).The expression of DNMT1 at mRNA and protein levels all decreased(P<0.05).The protein levels of NF-?B(P65)and DNMT1 were decreased after treated with DAC for 48 h.CONCLUSION: The NF-?B inhibitor PDTC inhibits the proliferation of U266,RPMI8226 cells and induces cell apoptosis.It may be related to the down-regulated expression of Bcl-2 and activation of the apoptotic pathways.Inhibition of NF-?B by PDTC inhibits the expression of DNMT1 gene.DAC can inhibit the expression of DNMT1 and NF-?B.Therefore,NF-?B may interact with DNMT1 to promote the development of MM.