Effect of rapamycin on mTOR/p70S6K signaling pathway in esophageal squamous cell carcinoma EC9706 cell line

Objective:To study the effects of rapamycin on mTOR/p70S6K signaling pathway in esophageal squamous cell carcinoma EC9706 cell line.Methods:The existence of mTOR/pTOS6K signaling pathway was demonstrated by immunocyto- chemistry.Electrophoresis,RT-PCR,Western blot,and flow cytometry was used to investigate the effects of rapamycin on roTOR,p70S6K signaling pathway and apoptosis of EC9706 cells at DNA,RNA,and protein levels.Results:Immunocytoche- mistry showed that roTOR was positively expressed in the nucleus and cytoplasm of EC9706 cells.An apparent DNA ladder was observed and expressions of mTOR mRNA and proteins decreased after rapamycin treatment.But the mRNA and protein ex- pressions of roTOR downstream target pTOS6K were increased by rapamycin in a concentration-dependent manner in EC9706 cells.Flow cytometry revealed that EC9706 cells were arrested at G_1 phage by rapamycin.Conclusion:mTOR/p70S6K signaling pathway exists in esophageal squamous cell carcinoma cells and is constitutively activated.Rapamycin stimulats apoptosis of EC9706 cells and inhibits the mTOR/p70S6K signaling pathway therefore suppressing transcription indirectly.