Overcoming acquired resistance to anticancer therapy: focus on the PI3K/AKT/mTOR pathway

Cancer Chemother Pharmacol. 2013 Apr;71(4):829-42. doi: 10.1007/s00280-012-2043-3. Epub 2013 Feb 3.


Background: Most targeted anticancer therapies, as well as cytotoxic and radiation therapies, are encumbered by the development of secondary resistance by cancer cells. Resistance is a complex phenomenon involving multiple mechanisms, including activation of signaling pathways such as phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR). Novel strategies to overcome resistance by targeting these signaling pathways are being evaluated.

Methods: PubMed and key cancer congress abstracts were searched until July 2012 for preclinical and clinical data relating to the PI3K/AKT/mTOR pathway and anticancer treatment resistance, and use of PI3K/AKT/mTOR inhibitors in resistant cancer cell lines and patient populations.

Results: Activation of the PI3K/AKT/mTOR pathway is frequently implicated in resistance to anticancer therapies, including biologics, tyrosine kinase inhibitors, radiation, and cytotoxics. As such, inhibitors of the PI3K/AKT/mTOR pathway are being rapidly evaluated in preclinical models and in clinical studies to determine whether they can restore therapeutic sensitivity when given in combination. In breast cancer, non-small-cell lung cancer, and glioblastoma, we find compelling preclinical evidence to show that inhibitors of PI3K or mTOR can restore sensitivity in resistant cells. Although clinical evidence is less mature, a recent Phase III study with the mTORC1 inhibitor everolimus in patients with advanced breast cancer resistant to aromatase inhibition and several Phase I/II studies with PI3K inhibitors demonstrate proof-of-concept, warranting future clinical evaluation.

Conclusion: Current preclinical and clinical evidence suggest that inhibitors of the PI3K/AKT/mTOR pathway could have utility in combination with other anticancer therapies to circumvent resistance by cancer cells. Multiple clinical studies are ongoing.

Publication types

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

MeSH terms

  • Animals
  • Breast Neoplasms / drug therapy
  • Drug Resistance, Neoplasm*
  • Glioblastoma / drug therapy
  • Humans
  • Lung Neoplasms / drug therapy
  • Neoplasms / drug therapy*
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / physiology*
  • Signal Transduction* / drug effects
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / physiology*


  • Phosphoinositide-3 Kinase Inhibitors
  • TOR Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt