Akt inhibitor shows anticancer and radiosensitizing effects in malignant glioma cells by inducing autophagy

Int J Oncol. 2007 Oct;31(4):753-60.


Autophagy, or programmed cell death type II, is one of the responses of cancer cells to various therapies, including ionizing radiation. Recently, we have shown that radiation induces autophagy, but not apoptosis, in various malignant glioma cell lines. Autophagy is mainly regulated by the mammalian target of rapamycin (mTOR) pathway. The Akt/mTOR pathway also mediates oncogenesis and radioresistance. Thus, we hypothesized that inhibiting this pathway has both an anticancer and radiosensitizing effect by activating autophagy. The purpose of our study was therefore to determine whether and by which mechanisms an Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2(R)-2-O-methyl-3-O-octadecylcarbonate, had anticancer and radiosensitizing effects on malignant glioma U87-MG and radioresistant U87-MG cells with a consistitutively active form of epidermal growth factor receptor (U87-MGDeltaEGFR). Treatment with the Akt inhibitor successfully inhibited Akt activity and reduced cell viability in both cell lines. In terms of the mechanism, the Akt inhibitor decreased phosphorylated p70S6 kinase, a downstream target of Akt, and induced autophagy, but not apoptosis. Furthermore, the Akt inhibitor radiosensitized both U87-MG and U87-MGDeltaEGFR cells by enhancing autophagy. Specific inhibition of Akt using the dominant-negative Akt plasmid also resulted in enhanced radiation-induced autophagy. In conclusion, an Akt inhibitor showed anticancer and radiosensitizing effect on U87-MG and U87-MGDeltaEGFR cells by inducing autophagy. Thus, Akt inhibitors may represent a promising new therapy as a single treatment or used in combination with radiation for malignant gliomas, including radioresistant ones that express DeltaEGFR.

Publication types

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

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Apoptosis / radiation effects
  • Autophagy / drug effects*
  • Autophagy / radiation effects
  • Cell Cycle / drug effects
  • Cell Cycle / radiation effects
  • Cell Line, Tumor / drug effects
  • Cell Line, Tumor / radiation effects
  • Cell Survival / drug effects
  • Cell Survival / radiation effects
  • Colony-Forming Units Assay
  • Enzyme Inhibitors / pharmacology*
  • Glioma / drug therapy
  • Glioma / pathology*
  • Glioma / radiotherapy
  • Humans
  • Inositol / analogs & derivatives*
  • Inositol / pharmacology
  • Phosphorylation / drug effects
  • Phosphorylation / radiation effects
  • Protein Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors*
  • Radiation, Ionizing
  • Radiation-Sensitizing Agents / pharmacology*
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • TOR Serine-Threonine Kinases


  • 1L-6-hydroxymethyl-chiro-inositol 2(R)-2-O-methyl-3-O-octadecylcarbonate
  • Antineoplastic Agents
  • Enzyme Inhibitors
  • Radiation-Sensitizing Agents
  • Inositol
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa