Binding of insulin-like growth factors to Tera-2 human embryonal carcinoma cells during differentiation.
Differentiation of Tera-2 human embryonal carcinoma cells by exposure to 2.1 mM alpha-difluoromethylornithine resulted in changes in morphology, a decrease in growth rate, and changes in the expression of SSEA-1 differentiation antigen. While the binding of 125I-insulin-like growth factor I (IGF-I) remained relatively constant during differentiation, binding of 125I-IGF-II increased 2-3-fold. Further, the binding of IGF-II was 87 times greater than IGF-I in both undifferentiated and differentiated cells. Undifferentiated Tera-2 cells exhibited a single class of binding sites for both IGF-I (KD = 1.2 nM, 7.0 x 10(3) sites/cell) and IGF-II (KD = 8.3 nM, 3.4 x 10(5) sites/cell). Following differentiation, IGF-I continued to bind to a single class of binding sites (KD 1.0 nM, 6.7 x 10(3) sites/cell) whereas IGF-II bound to both high-affinity sites (KDH 0.3 nM, 2.2 x 10(5) sites/cell) and low-affinity sites (KDL 15.1 nM, 1.6 x 10(7) sites/cell). The binding of iodinated IGF-II was blocked by unlabeled IGF-II but not IGF-I. In contrast, 125I-IGF-I binding was prevented by either IGF-I or IGF-II. Affinity cross-linking experiments demonstrated the presence of both type I and type II IGF receptors along with a number of IGF binding proteins. IGF-I failed to stimulate the incorporation of [3H]thymidine in both undifferentiated and differentiated cells. Although IGF-II caused a significant increase in [3H]thymidine incorporation in both undifferentiated and differentiated Tera-2 cells, the magnitude of the response and the sensitivity of the cells to IGF-II stimulation was diminished following differentiation. The observed changes in IGF-II binding, which occur in conjunction with cellular differentiation, may be an important feature of the expression of the differentiated phenotype by human germ cell tumors.
Fleck
J F
JF
Department of Medicine, Indiana University School of Medicine, Indianapolis.
Sledge
G W
GW
Benenati
S V
SV
Frolik
C A
CA
Roth
B J
BJ
Hirsch
K S
KS
D001665:Binding Sites; D001667:Binding, Competitive; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects; D000518:Eflornithine / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D016256:Lewis X Antigen / Q000032:analysis; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013724:Teratoma; D013936:Thymidine / Q000378:metabolism
D016256:Lewis X Antigen; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013936:Thymidine; D000518:Eflornithine