OBJECTIVETo investigate the effect of small interfering RNA (siRNA)-mediated silencing of monocarboxylate transporter 1 (MCT1) on the sensitivity of drug-resistant nasopharyngeal carcinoma HNE1/DDP cells to cisplatin (DDP)-induced apoptosis and explore the possible mechanism.

METHODSThe expression of MCT1 was analyzed in HNE1 and HNE1/DDP cells and in HNE1/DDP cells transfected with siRNA using Western blot. MTT assay was used to assess the inhibitory effect of different concentrations of DDP alone or in combination with MCT1 siRNA on the proliferation of HNE1/DDP cells. The apoptosis of cells treated with MCT1 siRNA or/and DDP (8 µmol/L) was assessed using flow cytometry with PI staining, and the mitochondrial membrane potential was detected using JC-1 staining assay; the expressions of Mcl-1, Bak, Bcl-2, and Bax were analyzed using Western blotting.

RESULTSHNE1/DDP cells showed a high expression of MCT1, and MCT1 silencing using siRNA significantly increased the sensitivity of HNE1/DDP cells to DDP (P<0.05) and partly reversed DDP resistance of the cells. MCT1 silencing enhanced the sensitivity of HNE1/DDP cells to DDP-induced apoptosis. Treatment of HNE1/DDP cells with MCT1 siRNA combined with 8 µmol/L DDP for 24 h resulted in an apoptotic rate of (51.23∓2.86)%, significantly higher than that in cells treated with MCT1 siRNA or DDP alone (P<0.05). The combined treatment also reduced the mitochondrial membrane potential, down-regulated the expression of Mcl-1 and Bcl-2, and up-regulated the expression of Bax in the DDP-resistant cells.

CONCLUSIONMCT1 siRNA can enhance the sensitivity of HNE1/DDP cells to DDP-induced apoptosis, the mechanism of which may involve the down-regulation of Mcl-1 and Bcl-2 and up-regulation of Bax expression.