Regulation of insulin-like growth factor-IL expression and its role in autocrine growth of human neuroblastoma cells.
Insulin-like growth factor-II (IGF-II) is highly expressed in fetal tissues and may act as an autocrine growth factor during early embryogenesis. The SH-SY5Y human neuroblastoma cell line also expresses IGF-II and its receptors and responds to exogenous IGF-II with increased DNA synthesis, cell division, and neuritic outgrowth. For this study, we tested the hypothesis that IGF-II mediates autocrine growth of SH-SY5Y cells in serum-free media. SH-SY5Y cells plated at high densities proliferated in serum-free media, whereas sparsely plated cells did not. IGF-II mRNA levels increased within 24 hours of serum deprivation and were associated with increased immunoreactive IGF-II protein. Exogenous addition of IGF-II increased 3H-TdR incorporation and cell number in a dose- and time-dependent fashion. By nuclear labelling experiments using 5-Bromo-2' deoxyuridine (BrdU), we detected a twofold higher percentage of S phase nuclei after a 24-hour incubation in IGF-II. Treatment of SH-SY5Y cells with anti-IGF-II antibodies in serum-free media inhibited cell proliferation, and this inhibition was partially overcome by the addition of increasing concentrations of IGF-II. Collectively, our results indicate that IGF-II mediates an autocrine growth mechanism in SH-SY5Y cells that is associated with increased IGF-II expression.
Martin
D M
DM
Department of Neurology, University of Michigan, Ann Arbor 48104.
Feldman
E L
EL
D000906:Antibodies / Q000276:immunology; D002453:Cell Cycle; D002455:Cell Division; D002470:Cell Survival; D016895:Culture Media, Serum-Free; D004247:DNA / Q000096:biosynthesis; D005786:Gene Expression Regulation; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured
D000906:Antibodies; D016895:Culture Media, Serum-Free; D007335:Insulin-Like Growth Factor II; D004247:DNA