Inhibition of N-(4-hydroxyphenyl)retinamide-induced autophagy at a lower dose enhances cell death in malignant glioma cells

Carcinogenesis. 2008 Mar;29(3):600-9. doi: 10.1093/carcin/bgm264. Epub 2008 Jan 3.

Abstract

The question whether chemotherapy-induced autophagy is causative to the demise of the cells or a part of the survival mechanism activated during cellular distress is unclear. Others and we have previously demonstrated apoptosis-inducing capacity of N-(4-hydroxyphenyl)retinamide (4-HPR) in malignant glioma cells. We provide evidences of 4-HPR-induced autophagy at a lower concentration (5 microM). Suboptimal dose of 4-HPR treatment of malignant glioma cell lines increased G(2)/M arrest, whereas cell accumulated in S phase at a higher concentration. 4-HPR-induced autophagy was associated with acidic vacuole [acidic vesicular organelle (AVO)] formation and recruitment of microtubule-associated protein light chain 3 (LC3). At a higher concentration of 10 microM of 4-HPR, glioma cells undergoing apoptosis manifested autophagic features indicated by autophagosome formation, AVO development and LC3 localization. Autophagy inhibition at an early stage by 3-methyl adenine inhibited the AVO formation and LC3 localization with an enhancement in cell death. Bafilomycin A1, a specific inhibitor of vacuolar type Hthorn-ATPase also prevented AVO formation without effecting LC-3 localization pattern and also enhanced the extent of 4-HPR-induced cell death. 4-HPR activated c-jun and P38(MAPK) at both 5 and 10 microM concentrations, whereas increased activation of extracellular signal-regulated kinase 1/2 and NF-kappaB was seen only at lower dose. Inhibiting phosphoinositide 3-kinase and mitogen-activated protein kinases pathways modulated 4-HPR-induced cell death. This is the first report that provides evidences that besides apoptosis induction 4-HPR can also induce autophagy. These results indicate that 4-HPR-induced autophagy in glioma cell may provide survival advantage and inhibition of autophagy may enhance the cytotoxicity to 4-HPR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy / drug effects*
  • Brain Neoplasms / pathology*
  • Cell Death / drug effects*
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Fenretinide / antagonists & inhibitors*
  • Fenretinide / pharmacology
  • Flow Cytometry
  • Glioma / pathology*
  • Humans
  • Immunohistochemistry
  • Microscopy, Electron, Transmission
  • Protein Kinases / metabolism

Substances

  • Fenretinide
  • Protein Kinases