Molecular neuro-oncology and development of targeted therapeutic strategies for brain tumors. Part 2: PI3K/Akt/PTEN, mTOR, SHH/PTCH and angiogenesis

Expert Rev Anticancer Ther. 2004 Feb;4(1):105-28. doi: 10.1586/14737140.4.1.105.


Brain tumors are a diverse group of malignancies that remain refractory to conventional treatment approaches. Molecular neuro-oncology has now begun to clarify the transformed phenotype of brain tumors and identify oncogenic pathways that might be amenable to targeted therapy. Activity of the phosphoinositide 3; kinase (PI3K)/Akt pathway is often upregulated in brain tumors due to excessive stimulation by growth factor receptors and Ras. Loss of function of the tumor suppressor gene PTEN also frequently contributes to upregulation of PI3K/Akt. Several compounds, such as wortmannin and LY-294002, can target PI3K and inhibit activity of this pathway. The mammalian target of rapamycin (mTOR) is an important regulator of cell growth and metabolism and is often upregulated by Akt. Clinical trials of CCI-779, an inhibitor of mTOR, are ongoing in recurrent malignant glioma patients. The sonic hedgehog/PTCH pathway is involved in the tumorigenesis of some familial and sporadic medulloblastomas. This pathway can be targeted by cyclopamine, which is under evaluation in preclinical studies. Angiogenesis is a critical process for development and progression of brain tumors. Targeted approaches to inhibit angiogenesis include monoclonal antibodies, receptor tyrosine kinase inhibitors, antisense oligonucleotides and gene therapy. Clinical trials are ongoing for numerous angiogenesis inhibitors, including thalidomide, CC-5103 and PTK 787/ZK 222584. Further development of targeted therapies and evaluation of these new agents in clinical trials will be needed to improve survival and quality of life of patients with brain tumors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Angiogenesis Inhibitors / pharmacology
  • Angiogenesis Inhibitors / therapeutic use*
  • Brain Neoplasms / blood supply
  • Brain Neoplasms / drug therapy*
  • Drug Delivery Systems
  • Drug Design
  • Enzyme Inhibitors / pharmacology
  • Enzyme Inhibitors / therapeutic use*
  • Hedgehog Proteins
  • Humans
  • Medical Oncology
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / metabolism
  • Molecular Biology
  • Neovascularization, Pathologic / drug therapy*
  • PTEN Phosphohydrolase
  • Patched Receptors
  • Patched-1 Receptor
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphoric Monoester Hydrolases / antagonists & inhibitors
  • Phosphoric Monoester Hydrolases / metabolism
  • Protein Kinase Inhibitors
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Receptors, Cell Surface
  • Signal Transduction
  • TOR Serine-Threonine Kinases
  • Trans-Activators / antagonists & inhibitors
  • Trans-Activators / metabolism
  • Tumor Suppressor Proteins / antagonists & inhibitors
  • Tumor Suppressor Proteins / metabolism


  • Angiogenesis Inhibitors
  • Enzyme Inhibitors
  • Hedgehog Proteins
  • Membrane Proteins
  • PTCH1 protein, human
  • Patched Receptors
  • Patched-1 Receptor
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Receptors, Cell Surface
  • SHH protein, human
  • Trans-Activators
  • Tumor Suppressor Proteins
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Phosphoric Monoester Hydrolases
  • PTEN Phosphohydrolase
  • PTEN protein, human