N-myc regulation of type I insulin-like growth factor receptor in a human neuroblastoma cell line.
Insulin-like growth factors I and II (IGF-I and IGF-II) stimulate proliferation and differentiation in many cell types, including cell lines derived from human neuroblastomas. Their effects are mediated via the IGF-I receptor (IGF-IR) that is essential for growth in these cells. Amplification of the N-myc oncogene is a marker for poor prognosis in neuroblastoma development, and it therefore seemed of interest to analyze the relationships that may exist between IGF-IR and N-myc. N-myc-deficient SK-N-SH neuroblastoma cells were used as an experimental model. After stable transfection with N-myc cDNA, Northern blotting revealed a marked increased in IGF-IR, IGF-II, IGF-binding protein (IGFBP)-2, and IGFBP-4 mRNA levels, whereas IGFBP-6 mRNA levels were clearly diminished. Western immunoblot analysis also demonstrated increased intact IGFBP-2 but decreased IGFBP-6 in the presence of N-myc oncogene. Parallel binding experiments using IGF-I missing the first 3 amino acids revealed a 47% increase in binding sites for IGF-I and an increase of at least 335% in DNA synthesis, as measured by labeled thymidine incorporation into DNA. s.c. injection of these cells into nude mice provoked xenograft development in 50-100% of cases (depending on the series of experiments). Control cells, in contrast, were not tumorigenic. In cells transfected with bp -420/+60 of the human IGF-IR promoter controlling expression of the luciferase reporter gene, promoter activity was stimulated by a factor of 3.8 +/- 0.6 (n = 6) in the presence of N-myc oncogene. This suggests transcriptional regulation of IGF-IR expression by N-myc. IGF-IR activity and N-myc amplification are two events that to date have been identified as independently instrumental in the etiology of human neuroblastoma. Our results provide the first evidence of a direct link between them and demonstrate the effects of the oncogene on components of the IGF system in neuroblastoma cell growth in vitro and in vivo.
Chambéry
D
D
INSERM Unité 515, Croissance, Différenciation et Processus Tumoraux, Hôpital Saint Antoine, Paris, France.
Mohseni-Zadeh
S
S
de Gallé
B
B
Babajko
S
S
D000818:Animals; D002455:Cell Division; D004247:DNA / Q000096:biosynthesis; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc / Q000502:physiology*; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D017526:Receptor, IGF Type 1 / Q000235:genetics*; D013002:Somatomedins / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D004247:DNA; D017526:Receptor, IGF Type 1