title: Negative regulation of mTOR activity by LKB1-AMPK signaling in non-small cell lung cancer cells.
abstract: OBJECTIVE
  To investigate the role of LKB1 in regulation of mTOR signaling in non-small cell lung cancer (NSCLC) cells.
  
  
  METHODS
  LKB1 protein expression and phosphorylation of AMPK, 4E-BP1 and S6K in the cells were assessed using Western blotting in various NSCLC cell lines (A549, H460, H1792, Calu-1 and H1299). Energy stress was mimicked by treating the cells with 2-deoxyglucose (2-DG). Compound C was used to inhibit AMPK activity. Cell growth was measured using the MTS assay.
  
  
  RESULTS
  LKB1 protein was expressed in LKB1 wild-type Calu-1, H1299 and H1792 cells, but it was undetected in LKB1 mutant A549 and H460 cells. Treatment of the LKB1 wild-type cells with 2-DG (5, 10 and 25 mmol/L) augmented the phosphorylation of AMPK in dose- and time-dependent manners. In the LKB1 wild-type cells, 2-DG dramatically suppressed the phosphorylation of two mTOR targets, 4E-BP1 and S6K, whereas the LKB1 mutant A549 and H460 cells were highly resistant to 2-DG-induced inhibition on mTOR activity. In addition, stable knockdown of LKB1 in H1299 cells impaired 2-DG-induced inhibition on mTOR activity. Pretreatment of H1299 and H1792 cells with the AMPK inhibitor compound C (10 μmol/L) blocked 2-DG-induced inhibition on mTOR activity. 2-DG inhibited the growth of H1299 cells more effectively than that of H460 cells; stable knockdown of LKB1 in H1299 cells attenuated the growth inhibition caused by 2-DG.
  
  
  CONCLUSIONS
  In non-small cell lung cancer cells, LKB1/AMPK signaling negatively regulates mTOR activity and contributes to cell growth inhibition in response to energy stress.
authors.affiliation: Department of Respiratory Medicine, Tianjin Medical University General Hospital, China.
authors.forename: Li-xia
authors.initials: LX
authors.lastname: Dong
authors.forename: Lin-lin
authors.initials: LL
authors.lastname: Sun
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Pan
authors.forename: Lin-juan
authors.initials: LJ
authors.lastname: Lian
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.forename: Dian-sheng
authors.initials: DS
authors.lastname: Zhong
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004734:Energy Metabolism; D004789:Enzyme Activation; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D058570:TOR Serine-Threonine Kinases; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases