Presence of a specific antiestrogen binding site on human follicular thyroid carcinoma cell line (UCLA RO 82 W-1): inhibition by an endogenous ligand present in human serum.
A receptor for antiestrogens, distinct from the estrogen receptor, has been identified in several tissues including the MCF-7 breast cancer cell line. Estrogen receptors have also been found in normal and pathological thyroid tissue homogenates. We demonstrate the presence of an antiestrogen binding site (AEBS) on a pure human follicular thyroid carcinoma cell line (UCLA RO 82 W-1) using a 3H-tamoxifen (3H-TAM) binding assay. The binding of 3H-TAM to the AEBS was determined after preincubation (30 min) of the cells with excess 17 beta-estradiol (2 mumol/L). Specific and saturable binding of 3H-TAM to the cells was observed. Displacement of the tracer from its binding site was dose dependent. Scatchard analysis revealed a dissociation constant (Kd) of 73 nmol/L, indicating a binding site with moderate affinity and capacity (72 pmol/10(6) cells). Using this assay we were also able to demonstrate the presence of an endogenous ligand for the AEBS in ethanol extracts of human serum. Cell growth and 3H-thymidine incorporation by the follicular thyroid carcinoma cells were inhibited when the cells were exposed to TAM (1.5 mumol/L). In conclusion, TAM is able to bind to a specific receptor on this follicular thyroid carcinoma cell line, and a natural circulating ligand present in ethanol extracts of human serum interferes with its binding.
Gross
C
C
Division of Endocrinology, University of California School of Medicine, Los Angeles 90024.
Yu
M
M
Van Herle
A J
AJ
Giuliano
A E
AE
Juillard
G J
GJ
D018263:Adenocarcinoma, Follicular / Q000378:metabolism* / Q000473:pathology; D001665:Binding Sites; D001667:Binding, Competitive; D001790:Blood Physiological Phenomena; D002455:Cell Division; D004965:Estrogen Antagonists / Q000378:metabolism*; D005260:Female; D006801:Humans; D008024:Ligands; D008297:Male; D013629:Tamoxifen / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured
D004965:Estrogen Antagonists; D008024:Ligands; D013629:Tamoxifen