STAT3 down regulates LC3 to inhibit autophagy and pancreatic cancer cell growth

Oncotarget. 2014 May 15;5(9):2529-41. doi: 10.18632/oncotarget.1810.

Abstract

The dismal 5-year survival (<5%) for pancreatic cancer (PanCA) underscores the need for developing effective therapeutic options. Recent studies from our laboratory have shown that Nexrutine® (Nx), a bark extract from Phellodendron amurense exhibits excellent anticancer activity in human pancreatic cancer cells through inhibition of inflammatory signaling via STAT3/NFκB/Cox-2. Given the apparent high oxidative stress and autophagic activity in pancreatic tumors, we investigated the potential of Nx to modulate autophagy, reactive oxygen species (ROS), and their crosstalk. Our results show that Nx inhibits autophagy and decreases ROS generation. Pharmacological inhibition of autophagy led to decreased ROS generation and proliferation with no significant effect on apoptosis. Further, using combination index analysis we also found that combination of late-stage autophagy inhibitor with Nx exhibited a moderate synergistic to additive effect. Additionally, genetic or pharmacological inactivation of STAT3 reduced LC3-II levels and expression indicating a possible role for STAT3 in transcriptional regulation of autophagy. Since both inflammatory and oxidative stress signaling activate STAT3, our data implicates that STAT3 plays a vital role in the regulation of autophagy through its contributions to the positive feedback loop between ROS and autophagy. Overall, our findings reveal an important role for STAT3/LC3/ROS in Nx-mediated anti-pancreatic cancer effects.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Autophagy / drug effects*
  • Blotting, Western
  • Humans
  • Microtubule-Associated Proteins / antagonists & inhibitors
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Oxidative Stress / drug effects
  • Pancreatic Neoplasms / drug therapy
  • Pancreatic Neoplasms / metabolism
  • Pancreatic Neoplasms / pathology*
  • Plant Extracts / pharmacology*
  • RNA, Messenger / genetics
  • Reactive Oxygen Species / metabolism*
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • STAT3 Transcription Factor / genetics
  • STAT3 Transcription Factor / metabolism*
  • Signal Transduction / drug effects
  • Tumor Cells, Cultured

Substances

  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • NF-kappa B
  • Nexrutine
  • Plant Extracts
  • RNA, Messenger
  • Reactive Oxygen Species
  • STAT3 Transcription Factor
  • STAT3 protein, human