Insulin-like growth factor-II (IGF-II)/Mannose-6-phosphate receptors are increased in primary human thyroid neoplasms.
Insulin-like growth factor (IGF)-II receptors were demonstrated in normal and neoplastic tissues of human thyroid. Specific binding of [125I]IGF-II to thyroid membranes was dependent on the time and temperature of incubation, and a steady state was achieved after 22 h of incubation at 4 degrees C. The binding of [125I]IGF-II was dose-dependently displaced by unlabelled IGF-II with 50% inhibition at an IGF-II concentration of 6 ng/ml. IGF-I had a relative potency of 1% compared to IGF-II, and insulin showed no inhibition at concentrations as high as 2000 ng/ml. Scatchard analysis of the binding data revealed a single class of IGF-II receptor with high affinity. Affinity crosslinking and autoradiography demonstrated the type II IGF receptors. Specific binding of [125I]IGF-II to thyroid papillary cancer tissues (mean [S.D.]13.2[1.3]% per 200 micrograms protein, n = 8) was significantly (P less than 0.01) higher than that to the surrounding normal tissues (4.8 [0.5]%). The binding in follicular cancer and follicular adenoma was also significantly higher than that in the corresponding normal tissues. The higher IGF-II binding to neoplastic tissues was due to an increase in the number of binding sites without any change of affinity. These results suggest that the increased IGF-II receptors may be involved in growth or functions of thyroid neoplasms.
Yashiro
T
T
Department of Surgery, Tsukuba University, Japan.
Tsushima
T
T
Murakami
H
H
Obara
T
T
Fujimoto
Y
Y
Shizume
K
K
Ito
K
K
D001667:Binding, Competitive; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013961:Thyroid Gland / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism
D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007335:Insulin-Like Growth Factor II