Metformin inhibits the proliferation of human esophageal squamous cell carcinoma KYSE450 cells in vitro and in vivo / 肿瘤

ABSTRACT

Objective: To investigate the inhibitory effect of metformin on the proliferation of esophageal cancer KYSE450 cells, and to explore its possible mechanism. Methods: The human esophageal cancer KYSE450 cells were cultured in vitro and treated with different concentrations of metformin (5, 10, 20 and 40 mmol/L). The proliferation and apoptosis of KYSE450 cells after metformin treatment were detected by MTT and FCM method, respectively. The expression levels of 4E-binding protein 1 (4EBP1) and S6 kinase 1 (S6K1) mRNAs and proteins were detected by semi-quantitative RT-PCR and Western blotting, respectively. The subcutaneous tumor xenograft models of esophageal squamous cell carcinoma KYSE450 cells in nude mice were constructed, and were divided into two groups at the 7th day after injection with KYSE450 cells. In the two groups, metformin or 0.9% sodium chloride solution was separately used by intraperitoneal injection for 15 d. The size of tumor was measured every 3 days. The cell morphological characteristics of tumor xenografts were detected by HE staining. The expressions of S6K1 and 4EBP1 proteins in xenograft tumor tissues were detected by immunohistochemistry. Results: Different concentrations of metformin (5, 10, 20 and 40 mmol/L) could obviously inhibit the proliferation of KYSE450 cells in a dose- and time-dependent manner (all P<0.0001). The apoptosis rates of KYSE450 cells treated with 5, 10 and 20 mmol/L metformin were increased in a concentration-dependent manner (all P<0.05). The expression levels of 4EBP1 and S6K1, two downstream molecules of mammalian target of rapamycin (mTOR), in KYSE450 cells were significantly down-regulated with the increasing of concentrations or time of metformin treatment (all P<0.05). The growth of tumor xenografts in nude mice of metformin group was significantly suppressed (P < 0.0001). The expression levels of 4EBP1 and S6K1 proteins in tumor xenograft tissues were significantly down-regulated after metformin injection (both P<0.05). Conclusion: Metformin can inhibit the proliferation of esophageal cancer KYSE450 cells in vitro and in vivo, and its mechanism may be related to the down-regulation of 4EBP1 and S6K1 expressions in the downstream pathway of mTOR.