Modulation by retinoic acid of insulin-like growth factor (IGF) and IGF binding protein expression in human SK-N-SH neuroblastoma cells.
Growth in neuroblastoma cells is regulated by insulin-like growth factors (IGFs) whose action is modulated by IGF binding proteins (IGFBPs). In this study, SK-N-SH neuroblastoma cells were shown to produce IGF-II, IGFBP-2, IGFBP-4 and small quantities of IGFBP-6. We have studied the effects of a natural morphogen, retinoic acid (RA), on growth and IGFBP expression in these cells. In all experiments, cells were cultured in serum-free medium and treated with 1 mumol/l RA for 12 h. Cell number increased by almost 50% during the first 24 h after the beginning of treatment. This stimulation was inhibited by 80% or more in the presence of the anti-type 1 IGF receptor antibody alpha-IR3 and anti-IGF-II antibody. The IGF-II concentrations in the culture media, measured after acidic gel filtration, increased about 1.5-fold and Northern blotting showed a concomitant increase in IGF-II mRNA levels. The mitogenic effect of RA therefore reflects its stimulation of IGF-II production. The availability of IGF-II to the cells may also be enhanced because of the proteolysis of IGFBP-2 to which it is bound. After this initial phase, proliferation ceased despite continued IGF-II production between 24 and 72 h. Both IGFBP-2 and IGFBP-4 production decreased, whereas that of IGFBP-6 increased. These changes appeared both in the protein quantities and in their mRNAs. Insulin-like growth factor binding protein 6 has a strong affinity for IGF-II, 5-10 times that of IGFBP-2 and at least 10 times that of the type I IGF receptor, and the arrested proliferation may result, at least in part, from sequestration by IGFBP-6 of the IGF-II secreted.
Babajko
S
S
Institut National de la Santé et de la Recherche Médicale, Unité de Recherches sur la Régulation de la Croissance, Hopital Saint Antoine, Paris, France.
Binoux
M
M
D015153:Blotting, Western; D002455:Cell Division; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000235:genetics; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018976:Insulin-Like Growth Factor Binding Protein 6; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D014212:Tretinoin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II