title: Roles of antiestrogen binding sites in human endometrial cancer cells.
abstract: Estrogen-noncompatible antiestrogen binding sites (AEBS) as well as estrogen receptors (ER), and the growth-inhibitory effect of tamoxifen were investigated in two human endometrial cancer cell lines, IK-90 and HEC-IA cells. IK-90 cells contained specific AEBS, but no ER was found in these cells. Scatchard plot analysis of AEBS in 12,000 g supernatant from IK-90 cells showed a high affinity binding site for tamoxifen (Kd:5.6 +/- 1.0 nM) with the maximum binding site of 457 +/- 47 fmol/mg protein. However, no measurable ER or AEBS was found in HEC-IA cells. The effect of tamoxifen on the growth of cells was found to be identical in both cell lines; the addition of 10 microM tamoxifen to culture medium was cytocidal whereas tamoxifen at lower concentrations (1 nM-1 microM) did not significantly affect the growth of both IK-90 and HEC-IA cells. These results demonstrate for the first time the presence of AEBS in human endometrial cancer cells. The present results also suggest that AEBS does not play a fundamental role in mediating the growth-inhibitory effect of tamoxifen in endometrial cancer cells.
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D001665:Binding Sites; D001667:Binding, Competitive; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004958:Estradiol / Q000378:metabolism; D004965:Estrogen Antagonists / Q000378:metabolism*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011960:Receptors, Estrogen / Q000378:metabolism; D013629:Tamoxifen / Q000378:metabolism / Q000494:pharmacology; D014594:Uterine Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D013629:Tamoxifen; D004958:Estradiol