Type I and type II insulin-like growth factor receptors and their function in human Ewing's sarcoma cells.
Binding studies using recombinant human 125I-labelled insulin-like growth factor I ([125I]IGF-I) revealed IGF-I receptors in three Ewing's sarcoma cell lines with Kd ranging from 74 x 10(-12) M to 100 x 10(-12) M and Bmax = 36-63 fmol/mg cell protein. [125I]IGF-I binding was displaced by IGF-I, IGF-II and insulin with IC50 values of 1.5 nM, 6.3 nM and 0.7 microM respectively. Recombinant human [125I]IGF-II radioligand-binding assays in the cell lines disclosed specific binding sites for IGF-II with Kd = (110-175) x 10(-12) M and Bmax varying from 21 fmol/mg to 72 fmol/mg cell protein. Neither IGF-I nor insulin displaced [125I]IGF-II binding. IGF-I was found to increase basal glucose transport by maximally 1.5 times with EC50 = 0.9 nM IGF-I. The efficacy and potency of IGF-II on glucose uptake were comparable to those of IGF-I whereas insulin was ineffective. IGF-I and IGF-II also provoked stimulation of glycogen synthesis in Ewing's sarcoma cells. The maximal glycogenic response was reached at 0.01 microM IGF-I and 0.1 microM IGF-II, the EC50 value being approximately 1 nM IGF-I and 2 nM IGF-II. Insulin did not significantly influence glycogen formation. IGF-I and IGF-II but not insulin increased DNA synthesis in Ewing's sarcoma cells. The maximal mitogenic response was obtained with 10 nM IGF-I or IGF-II with an EC50 value of about 0.7 nM for both peptides. alpha-IR-3, a monoclonal antibody specific for the IGF type I receptor, effectively blocked IGF-I- and IGF-II-mediated metabolic responses. In conclusion, the data show that IGF-I and IGF-II induce rapid and long-term biological responses in Ewing's sarcoma cells exclusively through interaction with IGF type I receptors.
van Valen
F
F
Abt. für Pädiatrische Hämatologie und Onkologie, Heinrich-Heine-Universität, Düsseldorf, Federal Republic of Germany.
Winkelmann
W
W
Jürgens
H
H
D000911:Antibodies, Monoclonal; D016895:Culture Media, Serum-Free; D004247:DNA / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007700:Kinetics; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D017451:Receptors, Somatomedin; D012512:Sarcoma, Ewing / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure*; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D016895:Culture Media, Serum-Free; D007328:Insulin; D007457:Iodine Radioisotopes; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D014316:Tritium; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA; D005947:Glucose; D013936:Thymidine