Objective: To investigate the molecular mechanism of down-regulation of monocarboxylic acid transporter 1 (MCT1) on the proliferation inhibition of glioma cell. Methods: siMCT1, siMCT4 and negative control siRNA were transfected into glioma cell lines including U-251 and U-87. The proliferation activities of U-251 and U-87 cells were detected by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay and clonogenic assay. Glucose consumption and lactic acid efflux of U-251 and U-87 cells were determined by spectrophotometry.Western blot was used to detect the expressions of MCT1, MCT4, human glucose transporter 1 (GLUT1), GLUT4, tuberous sclerosis associated protein (TSC2), p-TSC2, 4E binding protein 1 (4EBP1), p-4EBP1, ribosomal S6 protein kinase (S6) and p-S6 protein in U-251 and U-87 cells. Results: Compared with negative control group, siMCT1 and siMCT4 significantly inhibited the expressions of MCT1 and MCT4 protein in U-251 and U-87 cells (both P<0.05). However, only knockdown of MCT1, the proliferation activities of U-251 and U-87 cells significantly decreased (P<0.05). The clone formation rates of U-251 and U-87 cells decreased to (55.20±3.27)% and (68.33±4.58) %, respectively (P<0.05). The glucose consumption of U-251 and U-87 cells in the negative control group at 72 hours were (82.65±6.66) pmol/L and (63.33±5.27) pmol/L, respectively, significantly higher than (31.70±3.17) pmol/L and (26.41±3.19) pmol/L of the siMCT1 transfected group (P<0.05). The extracellular lactate flow of U-251 and U-87 cells in negative control group at 72 h were (155.49±8.15) mmol/L and (135.37±8.21) mmol/L, respectively, significantly higher than (42.69±4.66) mmol/L and (38.91±4.83) mmol/L of the siMCT1 transfected group (P<0.05). Western blot analysis showed that knockdown of MCT1 significantly decreased the protein levels of GLUT1 p-TSC2, p-4EBP1 and p-S6 in U-251 and U-87 cells. Conclusions: Downregulation of MCT1 expression can inhibit the proliferation of glioma cells. Deletion of MCT1 inhibits the glycolysis and metabolism of glioma cells through regulating the mTOR signaling pathway.
目的： 探讨下调单羧酸转运蛋白1(MCT1)的表达对神经胶质瘤细胞增殖抑制的分子机制。 方法： 将siMCT1、siMCT4和阴性对照siRNA分别转染神经胶质瘤细胞系U-251和U-87，采用四甲基偶氮唑蓝(MTT)法检测U-251和U-87细胞的增殖活性，采用克隆形成实验检测U-251和U-87细胞的克隆形成能力，采用分光光度-比色法测定U-251和U-87细胞的葡萄糖消耗量和乳酸外流量。采用Western blot法检测U-251和U-87细胞中MCT1、MCT4、葡萄糖转运蛋白1(GLUT1)、GLUT4、结节性硬化症相关蛋白2(TSC2)、p-TSC2、真核细胞翻译起始因子4E结合蛋白1(4EBP1)、p-4EBP1、S6和p-S6蛋白的表达。 结果： 与阴性对照组比较，siMCT1和siMCT4干扰均能明显抑制U-251和U-87细胞中MCT1和MCT4蛋白的表达(均P<0.05)。但仅siMCT1转染后24～96 h，U-251和U-87细胞的细胞增殖活性明显降低(均P<0.05)。干扰MCT1的表达后，U-251和U-87细胞的克隆形成率分别下降至(55.20±3.27)%和(68.33±4.58)%，与阴性对照组比较，差异均有统计学意义(均P<0.05)。与72 h阴性对照组U-251和U-87细胞的葡萄糖消耗量[分别为(82.65±6.66)pmol/L和(63.33±5.27)pmol/L]比较，siMCT1转染组U-251和U-87细胞的葡萄糖消耗量明显降低[分别为(31.70±3.17)pmol/L和(26.41±3.19)pmol/L，均P<0.05)]；与72 h阴性对照组U-251和U-87细胞的乳酸外流量[(155.49±8.15)mmol/L和(135.37±8.21)mmol/L]比较，siMCT1转染组U-251和U-87细胞的乳酸外流量明显降低[分别为(42.69±4.66)mmol/L和(38.91±4.83)mmol/L，均P<0.05]。Western blot检测结果显示，U-251和U-87细胞转染siMCT1后能抑制GLUT1的表达，p-TSC2、p-4EBP1和p-S6蛋白的表达水平也明显降低。 结论： 下调MCT1表达能抑制神经胶质瘤细胞的增殖和克隆形成，其可能通过调控mTOR信号通路抑制GLUT1的表达，进而抑制其糖酵解代谢。.
Keywords: Cell proliferation; GLUT1; MCT1; Neurospongioma.