title: Dual Inhibition of PI3K/Akt/mTOR Pathway and Role of Autophagy in Non-Small Cell Lung Cancer Cells.
abstract: BACKGROUND
  The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling axis has emerged as a novel target for cancer therapy. Agents that inhibit this pathway are currently under development for lung cancer treatment. In the present study, we have tested whether dual inhibition of PI3K/Akt/mTOR signaling can lead to enahnced antitumor effects. We have also examined the role of autophagy during this process.
  
  
  METHODS
  We analyzed the combination effect of the mTOR inhibitor, temsirolimus, and the Akt inhibitor, GSK690693, on the survival of NCI-H460 and A549 non-small cell lung cancer cells. Cell proliferation was determined by MTT assay and apoptosis induction was evaluated by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Autophagy induction was also evaluated by acridine orange staining. Changes of apoptosis or autophagy-related proteins were evaluated by western blot analysis.
  
  
  RESULTS
  Combination treatment with temsirolimus and GSK690693 caused synergistically increased cell death in NCI-H460 and A549 cells. This was attributable to increased induction of apoptosis. Caspase 3 activation and poly(ADP-ribose) polymerase cleavage accompanied these findings. Autophagy also increased and inhibition of autophagy resulted in increased cell death, suggesting its cytoprotective role during this process.
  
  
  CONCLUSIONS
  Taken together, our results suggest that the combination of temsirolimus and GSK690693 could be a novel strategy for lung cancer therapy. Inhibition of autophagy could also be a promising method of enhancing the combination effect of these drugs.
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Korea Cancer Center Hospital, Seoul, Korea.
authors.forename: Eun-Hui
authors.initials: EH
authors.lastname: Jeong
authors.forename: Hyeong Sim
authors.initials: HS
authors.lastname: Choi
authors.forename: Tae-Gul
authors.initials: TG
authors.lastname: Lee
authors.forename: Hye-Ryoun
authors.initials: HR
authors.lastname: Kim
authors.forename: Cheol Hyeon
authors.initials: CH
authors.lastname: Kim