Bufalin induces apoptosis in human esophageal carcinoma ECA109 cells by inhibiting the activation of the mTOR/p70S6K pathway.

The present study examined whether bufalin could induce human esophageal carcinoma ECA109 cells apoptosis via inhibiting the activation of mechanistic target of rapamycin (mTOR)/p70 S6 kinase (p70S6K) pathway is discussed in this article. The present study used the esophageal squamous cell carcinoma ECA109 cell line to assess the apoptosis-inducing effects of bufalin via inhibition of the mTOR/p70S6K pathways. A plasmid containing the wild-type mTOR gene (wtmTOR) was transfected into ECA109 cells. The levels of p70S6K, phosphorylated (p)-p70S6K, cellular inhibitor of apoptosis-1 (cIAP-1) and Bcl-2-associated death promoter (BAD) in ECA109 cells were examined by western blot analysis, and apoptosis was detected by flow cytometry analysis and Giemsa staining. The results revealed that the expression of p-p70S6K was increased as the time progressed (at 0, 12 and 24 h), and then decreased at 30, 36, 42 and 48 h after transfection. The expression of cIAP-1 was significantly decreased as time progressed following the addition of bufalin, whereas that of BAD was increased. The levels of p-p70S6K and cIAP-1 were significantly higher in the wtmTOR-transfected group than in the control and empty vector-transfected groups, and then reduced following addition of bufalin; however, BAD expression was significantly lower in the wtmTOR-transfected group. The results of flow cytometry revealed the cell cycle of ECA109 was arrested at G2/M phase and the apoptotic rate was significantly lower in the wtmTOR-transfected group than in the control and empty vector-transfected groups, and then increased following addition of bufalin. In conclusion, the findings of the present study demonstrated that bufalin induced apoptosis in esophageal carcinoma cells via the inhibition of the mTOR/p70S6K pathway and indicated that treatment with bufalin could be combined with chemotherapy to overcome the resistance of esophageal carcinoma cells to chemotherapeutic-induced apoptosis.