Insulin-like growth factor I is the key growth factor in serum that protects neuroblastoma cells from hyperosmotic-induced apoptosis.
Neuroblastoma is a childhood tumor of the peripheral nervous system that remains largely uncurable by conventional methods. Mannitol induces apoptosis in neuroblastoma cell types and insulin-like growth factor I (IGF-I) protects these cells from hyperosmotic-induced apoptosis by affecting apoptosis-regulatory proteins. In the current study, we investigate factors that enable SH-SY5Y neuroblastoma cells to survive in the presence of an apoptotic stimulus. When SH-SY5Y cells are exposed to high mannitol concentrations, more than 60% of the cells are apoptotic within 48 h. Normal CS prevents hyperosmotic-induced apoptosis in a dose-dependent manner, with 0.6% CS protecting 50% of the cells, and 3% CS rescuing more than 70% of the cells from apoptosis. Serum also delays the commitment point for SH-SY5Y cells from 9 h to 35 h. A survey of several growth factors, including epidermal growth factor (EGF), platelet-derived growth factor (PDGF), nerve growth factor (NGF), fibroblast growth factor (FGF), and IGF-I reveals that IGF-I is a component of serum necessary for protection of neuroblastoma cells from death. Mitochondrial membrane depolarization occurs in greater than 40% of the cells after mannitol exposure and caspase-3 activation is increased in high mannitol conditions after 9 h. IGF-I blocks both the mitochondrial membrane depolarization and caspase-3 activation normally induced by hyperosmotic treatment in neuroblastoma cells. Our results suggest that (1) IGF-I is a key factor in serum necessary for protection from death and (2) IGF-I acts upstream from the mitochondria and the caspases to prevent apoptosis in human neuroblastoma.
Van Golen
C M
CM
Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA.
Feldman
E L
EL
D017209:Apoptosis / Q000187:drug effects*; D001798:Blood Proteins / Q000032:analysis / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000737:chemistry / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008353:Mannitol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D008970:Molecular Weight; D009447:Neuroblastoma / Q000473:pathology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects*; D009994:Osmolar Concentration; D017526:Receptor, IGF Type 1 / Q000502:physiology; D014407:Tumor Cells, Cultured
D001798:Blood Proteins; D006133:Growth Substances; D008353:Mannitol; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases