title: Human neuroblastoma cells use either insulin-like growth factor-I or insulin-like growth factor-II in an autocrine pathway via the IGF-I receptor: variability of IGF, IGF binding protein (IGFBP) and IGF receptor gene expression and IGF and IGFBP secretion in human neuroblastoma cells in relation to cellular proliferation.
abstract: Neuroblastoma cells are thought to depend upon autocrine stimulation by IGF-II but not by IGF-I. We have studied the expression of IGF, IGFBP and IGF receptor mRNA in two human neuroblastoma cell lines, SK-N-MC and CHP, and asked whether or not the expression of the IGF system in these malignant cells determines their growth pattern. SK-N-MC cells grow with a cell doubling time of 36 hours in medium supplemented with 10% fetal calf serum whereas CHP cells only grow with a doubling time of 72 h. In addition, the SK-N-MC cell line has a plating efficiency ten times greater than the CHP cell line. RNase protection assays were performed using (32)P-labelled riboprobes and RNA that had been purified from SK-N-MC and CHP cells respectively. A 520 bases human IGF-I, a 556 bases human IGF-II, a 480 bases human IGF-I receptor and a 250 human IGF-II/mannose-6-phosphate (M6P) receptor probe were radiolabelled as were human IGFBP-1, -2, -3, -4, -5 and -6 probes. While both SKNMC and CHP neuroblastoma cells expressed mRNAs for IGFBP-2, -4, and -6 no signal was detected for IGFBP-1, and -3 and only SK-N-MC cells expressed IGFBP-5 mRNA. In addition, a 400 bases protected band was seen with the IGF-I receptor probe and a 260 bases protected band with the IGF-IIM6P receptor probe in either cell line. Interestingly, a 300 bases protected species was detected with the IGF-II probe in CHP cell RNA whereas SK-N-MC cells did not express IGF-II transcripts. Conversely, SK-N-MC cells expressed a 520 bases IGF-I transcript while CHP cells did not show IGF-I mRNA expression. As determined by specific radioimmunoassays SK-N-MC cells secreted 0.75+/-0.02 ng/ml IGF-I, 1.2+/-0.04 ng/ml IGF-II and 149+/-2.1 ng/ml IGFBP-2 within 24 h, whereas CHP cells secreted 0.1+/-0.01 ng/ml IGF-I, but 6.2+/-0.1ng/ml IGF-II and 254.8+/-5.5 ng/ml IGFBP-2 (N=5). IGFBP-2 secretion correlated positively with IGF-II secretion in CHP cells (r=0.85, P=0.05) and negatively with IGF-I (r= -0.9, P<0.01) in SK-N-MC cells. In conclusion, SK-N-MC cells which grow rapidly and have a high plating efficiency, express IGF-I, while CHP cells that grow more slowly express IGF-II. We hypothesize that neuroblastoma cells depend upon autocrine stimulation by either IGF-I or IGF-II. Variable sensitivity to growth inhibitors or apoptotic processes may be related to the differential expression of the IGF system.
authors.affiliation: Children's Hospital, Justus Liebig University of Giessen, Germany. wieland.kiess@paediat.med.uni-giessen.de
authors.forename: W
authors.initials: W
authors.lastname: Kiess
authors.forename: G
authors.initials: G
authors.lastname: Koepf
authors.forename: H
authors.initials: H
authors.lastname: Christiansen
authors.forename: W F
authors.initials: WF
authors.lastname: Blum
mesh_terms: D019898:Autocrine Communication; D015153:Blotting, Western; D002455:Cell Division; D017077:Culture Media, Conditioned; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011863:Radioimmunoassay; D017526:Receptor, IGF Type 1 / Q000235:genetics* / Q000276:immunology; D012260:Ribonucleases / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D012260:Ribonucleases