Antiestrogen binding sites in human breast cancer biopsies. Measurement ligand-specificity and affinity, and correlation to estrogen and progesterone receptors.
Specific binding sites for the antiestrogen tamoxifen (AEBStot), as measured with the dextran-coated charcoal technique and Scatchard analysis, were quantitated in 43 of 44 breast cancer samples (41-2,100 fmol/mg protein). In this work, AEBStot has been defined as the sum of AEBSspec and estrogen receptor (ER), AEBSspec shows a very weak positive correlation with ER, and no correlation with progesterone receptor. Tamoxifen (TAM) has a lower affinity to ER compared with one of its main metabolites, 4-OH-TAM. This may be one reason why inhibition by excess estradiol on 3H-4-OH-TAM binding was better correlated with ER content in the same sample than if 3H-TAM was the radioactive ligand. It is therefore suggested that 3H-4-OH-TAM is a better choice than 3H-TAM for measuring AEBSspec alone. A possible role of AEBSspec for the clinical effects of TAM is discussed.
D001943:Breast Neoplasms / Q000032:analysis*; D004965:Estrogen Antagonists / Q000032:analysis; D005260:Female; D006801:Humans; D011869:Radioligand Assay; D011955:Receptors, Drug; D011960:Receptors, Estrogen / Q000032:analysis*; D011980:Receptors, Progesterone / Q000032:analysis; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000032:analysis; D014316:Tritium
D004965:Estrogen Antagonists; D011955:Receptors, Drug; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen; D014316:Tritium; C016601:afimoxifene; C028787:N-desmethyltamoxifen