Objective: To investigate the mechanism and clinical value of nicotinamide phosphoribosyltransferase (NAMPT) in multiple myeloma (MM).
Methods: RT-qPCR and Western blot were used to detect the expression of NAMPT in MM cells and normal bone marrow mononuclear cells. The biological function of NAMPT was analyzed by cell proliferation and apoptosis assay, small interfering RNA silencing, overexpression assay and chromatin immunoprecipitation assay.
Results: The mRNA and protein expression levels of NAMPT in MM cell lines (MM1R, MM1S, U266 and RPMI-8226) were significantly higher than those in normal bone marrow mononuclear cells (P < 0.001), and were most obvious in U266 cells. Compared with Si-NC group, the proliferation of U266 cells in Si-NAMPT group was significantly inhibited at 24, 48 and 72 h after transfection (P =0.006, P < 0.001, P =0.001), and the apoptosis rate of U266 cells was significantly increased at 48 h after transfection (P < 0.001). Compared with Flag-NC group, U266 cell proliferation in Flag-NAMPT group was significantly increased (P =0.003, P =0.002, P < 0.001), while the apoptosis rate decreased significantly at 48 h after transfection. The expression of NAMPT in U266 cells was regulated by XBP1 at transcriptional level. The proliferation rate of U266 cells with XBP1 or NAMPT stable knockout or MKC3946 pretreated with bortezomib was significantly decreased, the levels of BCL-2 mRNA and protein were also significantly decreased, while the levels of BAX mRNA and protein were significantly increased, moreover, the cleavage degree of caspase-3 significantly decreased, while caspase-3/7 activity increased dramatically (P < 0.05).
Conclusions: The high expression of NAMPT in MM cell line can promote MM cell proliferation and inhibit apoptosis. NAMPT is regulated by IRE1α-XBP1 signaling pathway in U266 cells. Stable knockdown of NAMPT or blocking of IRE1α-XBP1 pathway can significantly increase the sensitivity of U266 cells to bortezomib.
题目: NAMPT在多发性骨髓瘤中的作用机制及其临床意义.
目的: 探讨烟酰胺磷酸核糖转移酶（NAMPT）在多发性骨髓瘤中的作用机制及其临床价值。.
方法: 采用RT-qPCR和Western blot方法检测多发性骨髓瘤细胞和正常骨髓单个核细胞中NAMPT的表达水平，同时通过细胞增殖与凋亡实验、小干扰RNA沉默、过表达实验和染色质免疫共沉淀实验分析NAMPT的生物学功能。.
结果: 多发性骨髓瘤细胞系（MM1R、MM1S、U266和RPMI-8226）中NAMPT mRNA和蛋白的表达水平较正常骨髓单个核细胞均显著升高（P <0.001），且在U266细胞中最明显。与Si-NC组相比，Si-NAMPT组转染24、48、72 h均显著抑制U266细胞增殖（P =0.006，P <0.001，P =0.001），转染48 h时U266细胞凋亡率升高显著（P <0.001）。与Flag-NC组比较，Flag-NAMPT组U266细胞增殖均显著升高（P =0.003，P =0.002，P <0.001），转染48 h时细胞凋亡率明显降低。在U266细胞中NAMPT的表达在转录水平受到XBP1的调控。用硼替佐米处理XBP1或NAMPT稳定敲除或经MKC3946预处理的U266细胞后细胞增殖率均显著下降，BAX mRNA和蛋白水平显著升高，BCL-2 mRNA和蛋白水平显著下调，Caspase-3裂解度显著下降，Caspase-3/7活性急剧增加（P <0.05）。.
结论: NAMPT在多发性骨髓瘤细胞系中高表达，促进多发性骨髓瘤细胞增殖，抑制细胞凋亡。在U266细胞中NAMPT受IRE1α-XBP1信号通路的转录调控。稳定敲除NAMPT或阻断IRE1α-XBP1通路可显著提高U266细胞对硼替佐米的敏感性。.
Keywords: X-box binding protein 1; bortezomib; inositol-requiring enzyme 1α; multiple myeloma; nicotinamide phosphoribosyltransferase.