N-Myc induction stimulated by insulin-like growth factor I through mitogen-activated protein kinase signaling pathway in human neuroblastoma cells.
Insulin-like growth factor I (IGF-I) stimulates proliferation, survival, and differentiation in many cell types, including pediatric neuroblastomas. The effect is mediated via the type I IGF-I receptor (IGF-IR), which is essential for growth in these cells. Several lines of evidence indicate that IGF-IR function may be particularly important in the pathogenesis of neuroblastoma. Amplification of the N-myc oncogene or overexpression of N-Myc oncoprotein has been reported to be associated with resistance to therapy and poor prognosis of neuroblastomas. It was therefore of interest to analyze whether IGF-I signaling regulated expression of N-myc in KP-N-RT human neuroblastoma cells as an experimental model that has amplified N-myc. We found that IGF-I induces N-myc mRNA and protein in the KP-N-RT with maximums of four and six times more than the basal level at 2 and 3 h after stimulation, respectively. These effects of IGF-I were blocked by a neutralizing antibody against IGF-IR (alpha-IR3). Exogenous IGF-I induced phosphorylation and activation of extracellular signal-regulated kinases p44/42 (ERK1 and ERK2), with a maximal level 30 min after the stimulation. The MEK1 inhibitor PD98059 reduced IGF-I-mediated p44/42 MAPKs phosphorylation and produced a parallel reduction of IGF-I-stimulated N-Myc induction. Furthermore, both alpha-IR3 and PD98059 inhibited G1-S cell cycle progression stimulated by IGF-I. Our results demonstrate that IGF-I induces N-Myc in the KP-N-RT neuroblastoma cell line at the RNA level and establishes a clear correlation between N-Myc induction and activation of p44/42 MAPK signaling.
Misawa
A
A
Department of Pediatrics, Kyoto Prefectural University of Medicine, Japan.
Hosoi
H
H
Arimoto
A
A
Shikata
T
T
Akioka
S
S
Matsumura
T
T
Houghton
P J
PJ
Sawada
T
T
D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000502:physiology*; D009447:Neuroblastoma / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D004791:Enzyme Inhibitors; D005419:Flavonoids; D009363:Neoplasm Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one