title: Role of autophagy in apoptotic regulation by Akt in pancreatic cancer.
abstract: OBJECTIVE
  The Akt signaling pathway mediates a potent anti-apoptotic signal in pancreatic cancer and inhibition of this pathway has become an attractive mechanism to increase the efficacy of traditional chemotherapies. Autophagy is a lysosomal catabolic pathway by which eukaryotic cells recycle macromolecules and organelles. Although autophagy may function as a survival mechanism under metabolic stress conditions, it also serves as an alternate route to programmed cell death distinct from apoptosis. In the present study, we examined the role of autophagy in Akt-mediated regulation of cell death in pancreatic cancer.
  
  
  METHODS
  Mia-PaCa-2 and PANC-1 human pancreatic cancer cell lines were used in our experiments. The small-molecule inhibitor A-443654 was used to inhibit Akt, and rapamycin was used to inhibit mTOR. Autophagy was inhibited with Chloroquine and 3-methyladenine. Autophagy was assessed by immunoblotting for light chain-3 (LC-3) processing as well as fluorescence microscopy for autophagosome formation following transfection with a LC-3/GFP construct. Cell death was determined by fluorescence-activated cell sorting (FACS) with quantitation of the sub-G0 content.
  
  
  RESULTS
  Inhibition of either Akt or mTOR induced autophagy; inhibition of Akt but not of mTOR led to traditional caspase-mediated apoptosis. When autophagy was inhibited, cell death was abrogated following Akt, but not mTOR, inhibition.
  
  
  CONCLUSIONS
  The Akt signaling pathway regulates both autophagy and apoptosis through divergent pathways; mTOR mediates autophagy signaling but appears to be un-involved in cell death. Autophagy appears to play a role in the regulation of cell survival by Akt, but only when proximal signaling pathways not involving mTOR are simultaneously activated.
authors: Division of Surgical Oncology, Suite 3010, UC Davis Cancer Center, 4501 X Street, Sacramento, CA 95817, U.S.A. richard.bold@ucdmc.ucdavis.edu.
authors: Diego
authors: D
authors: Muilenburg
authors: Colin
authors: C
authors: Parsons
authors: Jodi
authors: J
authors: Coates
authors: Subbulakshmi
authors: S
authors: Virudachalam
authors: Richard J
authors: RJ
authors: Bold
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006801:Humans; D007191:Indazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000473:pathology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C504035:A 443654; D000590:Amino Acid Chloromethyl Ketones; D007191:Indazoles; D007211:Indoles; D047428:Protein Kinase Inhibitors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020169:Caspases; D020123:Sirolimus
keywords: AKT; Pancreatic cancer; autophagy; mTOR