title: Synergy between PI3K/Akt and Raf/MEK/ERK pathways in IGF-1R mediated cell cycle progression and prevention of apoptosis in hematopoietic cells.
abstract: The insulin like growth factor-1 (IGF-1) receptor (R) induced PI3K/Akt signal transduction cascade has critical roles in prevention of apoptosis and regulation of cell cycle progression. Here, we discuss the effects of IGF-1R-mediated signal transduction on hematopoietic cells which normally require interleukin-3 (IL-3) for growth and prevention of apoptosis. Cytokine-dependent FDC-P1 hematopoietic cells were conditionally transformed to grow in response to overexpression of IGF-1R in the presence of IGF-1. When these cells were deprived of IL-3 or IGF-1 for 24 hrs, they exited the cell cycle, activated caspase 3 and underwent apoptosis. The effects of inhibitors which targeted the PI3K/Akt and Raf/MEK/ERK pathways were determined. When the cells were cultured with IGF-1 and either PI3K or MEK inhibitors, cell cycle progression and DNA synthesis were inhibited and caspase 3 activity and apoptosis were induced. Coinhibition of both pathways synergized to prevent cell cycle progression, inhibit DNA synthesis and induce apoptosis. These inhibitors had more apoptotic inducing effects when the cells were grown in response to IGF-1 than IL-3, indicating that IL-3 can induce additional anti-apoptotic pathways. These results demonstrate that the PI3K/Akt and Raf/MEK/ERK pathways are intimately involved in IGF-1R-mediated cell cycle progression and prevention of apoptosis in hematopoietic cells.
authors.affiliation: Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
authors.forename: John G
authors.initials: JG
authors.lastname: Shelton
authors.forename: Linda S
authors.initials: LS
authors.lastname: Steelman
authors.forename: Edmond R
authors.initials: ER
authors.lastname: White
authors.forename: James A
authors.initials: JA
authors.lastname: McCubrey
mesh_terms: D000818:Animals; D017209:Apoptosis; D001773:Blood Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases; D004247:DNA; D007377:Interleukin-3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D017526:Receptor, IGF Type 1; C494918:AKT1 protein, human; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse