Activation of PI3K/mTOR pathway occurs in most adult low-grade gliomas and predicts patient survival

J Neurooncol. 2010 Mar;97(1):33-40. doi: 10.1007/s11060-009-0004-4. Epub 2009 Aug 25.

Abstract

Recent evidence suggests the Akt-mTOR pathway may play a role in development of low-grade gliomas (LGG). We sought to evaluate whether activation of this pathway correlates with survival in LGG by examining expression patterns of proteins within this pathway. Forty-five LGG tumor specimens from newly diagnosed patients were analyzed for methylation of the putative 5'-promoter region of PTEN using methylation-specific PCR as well as phosphorylation of S6 and PRAS40 and expression of PTEN protein using immunohistochemistry. Relationships between molecular markers and overall survival (OS) were assessed using Kaplan-Meier methods and exact log-rank test. Correlation between molecular markers was determined using the Mann-Whitney U and Spearman Rank Correlation tests. Eight of the 26 patients with methylated PTEN died, as compared to 1 of 19 without methylation. There was a trend towards statistical significance, with PTEN methylated patients having decreased survival (P = 0.128). Eight of 29 patients that expressed phospho-S6 died, whereas all 9 patients lacking p-S6 expression were alive at last follow-up. There was an inverse relationship between expression of phospho-S6 and survival (P = 0.029). There was a trend towards decreased survival in patients expressing phospho-PRAS40 (P = 0.077). Analyses of relationships between molecular markers demonstrated a statistically significant positive correlation between expression of p-S6(235) and p-PRAS40 (P = 0.04); expression of p-S6(240) correlated positively with PTEN methylation (P = 0.04) and negatively with PTEN expression (P = 0.03). Survival of LGG patients correlates with phosphorylation of S6 protein. This relationship supports the use of selective mTOR inhibitors in the treatment of low grade glioma.

Publication types

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

MeSH terms

  • Adult
  • Brain Neoplasms / drug therapy
  • Brain Neoplasms / mortality*
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glioma / drug therapy
  • Glioma / mortality*
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • PTEN Phosphohydrolase / genetics*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation / drug effects
  • Predictive Value of Tests
  • Protein Serine-Threonine Kinases / metabolism*
  • Retrospective Studies
  • Serine / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Statistics, Nonparametric
  • Sulfites / pharmacology
  • Sulfites / therapeutic use
  • TOR Serine-Threonine Kinases
  • Young Adult

Substances

  • Intracellular Signaling Peptides and Proteins
  • Sulfites
  • Serine
  • MTOR protein, human
  • Protein Serine-Threonine Kinases
  • TOR Serine-Threonine Kinases
  • PTEN Phosphohydrolase
  • PTEN protein, human
  • hydrogen sulfite