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.
Department of Medicine, Indiana University School of Medicine, Indianapolis.
J F
JF
Fleck
G W
GW
Sledge
S V
SV
Benenati
C A
CA
Frolik
B J
BJ
Roth
K S
KS
Hirsch
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