The Akt pathway: molecular targets for anti-cancer drug development.
The serine/threonine kinase Akt functions intracellularly as a cardinal nodal point for a constellation of converging upstream signaling pathways, which involve stimulation of receptor tyrosine kinases such as IGF-1R, HER2/Neu, VEGF-R, PDGF-R), and an assembly of membrane-localized complexes of receptor-PI-3K and activation of Akt through the second messenger PIP(3). The integration of these intracellular signals at the level of Akt and its kinase activity, regulates the phosphorylation of its several downstream effectors, such as NF-kappa B, mTOR, Forkhead, Bad, GSK-3 and MDM-2. These phosphorylation events in turn mediate the effects of Akt on cell growth, proliferation, protection from pro-apoptotic stimuli, and stimulation of neo-angiogenesis. Because Akt and its upstream regulators are deregulated in a wide range of solid tumors and hematologic malignancies, and in view of the aforementioned biologic sequelae of this pathway, the Akt pathway is considered a key determinant of biologic aggressiveness of these tumors, and a major potential target for novel anti-cancer therapies. This review focuses on ongoing translational efforts to therapeutically target Akt and its biologic sequelae, either at the level of Akt itself or at the levels of its upstream regulators and downstream effectors. Because Akt is also important for proliferative and anti-apoptotic signaling pathways critical for normal cells, particular emphasis is placed on the fine-tuning the targeting of individual components of this pathway to maximize the therapeutic index of anti-cancer strategies based on the PI-3K/Akt pathway.
Mitsiades
Constantine S
CS
Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston MA 02115, USA. Constantine_Mitsiades@dfci.harvard.edu
Mitsiades
Nicholas
N
Koutsilieris
Michael
M
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002455:Cell Division; D002470:Cell Survival; D002471:Cell Transformation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology; D006801:Humans; D018919:Neovascularization, Physiologic; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction
D000970:Antineoplastic Agents; D038362:Glycogen Synthase Kinase 3; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494918:AKT1 protein, human