Autocrine regulation of human tumor cell proliferation by insulin-like growth factor II: an in-vitro model.
We have shown that a pleomorphic cell line of abnormal human karyotype derived from a stomach carcinoma (LIM-1839) proliferates in serum-free medium, expresses insulin-like growth factor II (IGF-II) mRNA, and secretes IGF-II (up to 56 ng/ml in serum-free conditioned medium, as measured in a rat liver RRA. No detectable levels of IGF-I can be measured in serum-free conditioned medium by RIA. These cells also secrete IGF-binding proteins, detected by a charcoal adsorption assay. The release of IGF-II and IGF binding proteins into serum-free conditioned medium (1.7 pmol/10(6) cells.24 h and 0.8 pmol binding sites/10(6) cells.24 h for 3 days, respectively) is inhibited 80% by cycloheximide (10 micrograms/ml). The LIM-1839 cells have type I and type II IGF receptors, determined by affinity cross-linking and competition binding studies. These cells proliferated 1.6-fold over 4 days in serum-free medium, with fresh medium changes on days 0 and 2: their growth was inhibited 56% by 40 micrograms/ml Sm 1.2, a monoclonal antibody which recognizes IGF-I and IGF-II. The addition of 20 and 50 ng/ml multiplication stimulating activity (rat IGF-II) caused 1.8- and 1.7-fold increases in cell growth between days 0 and 4 compared to controls, while [Thr59]IGF-I, at 20 and 50 ng/ml, caused 1.6- and 2.0-fold increases. Insulin, at 2 and 10 micrograms/ml, had no significant effect. The stimulatory effects of endogenous and exogenous IGFs on LIM-1839 cell proliferation were inhibited by a monoclonal antibody to the type I IGF receptor, alpha IR-3. These results suggest that the LIM-1839 cells are biologically responsive to endogenously produced IGF-II, and may thereby provide an in vitro model for autocrine regulation of human tumor growth by IGF-II.
Thompson
M A
MA
University of Melbourne Department of Medicine, Victoria, Australia.
Cox
A J
AJ
Whitehead
R H
RH
Jonas
H A
HA
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001667:Binding, Competitive; D001769:Blood; D002352:Carrier Proteins / Q000378:metabolism; D002455:Cell Division; D003513:Cycloheximide / Q000494:pharmacology; D015870:Gene Expression; D006706:Homeostasis; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000276:immunology / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000378:metabolism; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000502:physiology*; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D003513:Cycloheximide