ABSTRACT
Estrogen receptor (ER) determination as a means of predicting hormone dependency of human breast cancer is widely used and generally accepted. In particular, fluorescent bovine serum albumin conjugates which represent large, bulky ligands compared to E2, might not reach structure-associated receptors. With the exception of autoradiography and antireceptor antibody methods, the histochemical methods were criticized for claiming the localization of ER in tissue sections. Receptor specificity of ligand binding of biochemical and histochemical methods is demonstrated by competitive inhibition of the ligand-receptor interaction by unlabeled ligands with an affinity for the receptor similar to that of E2. Contamination of fluorescent ligands by noncovalently bound hormone has been implicated but not thoroughly investigated. Incubation of calf uterine cytosol with sepharose-bound conjugates resulted in a significant decrease of cytosolic ER content. Human breast cancer cell lines as model systems are well suited for testing and validation of fluorescent ligands devised for histochemical receptor localization.
