[The effect of downregulation of MCT1 on the proliferation of glioma cells].

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.