Binding of labeled estrogen-albumin conjugates in breast cancer

It was Lee1 who was the first to use an estrogen-bovine serum albumin fluorescein isothiocyanate (O-BSA-FITC) complex in order to demonstrate estrogen binding sites in thin sections of mammary tumors. Synthesis of this O-BSA-FITC complex is relatively simple. This new method had the advantage over autoradiographic methods,2 viz., with respect to technical simplicity and speed. In contrast to immunological methods,1 the advantage of Lee’s method is that no complicated purifications of antigen and antibodies are necessary and, besides, no animals have to be sensitized against either the estrogen receptor proper or estradiol. In his first publication Lee interpreted the fluorescence observed without any restrictions as proof of the presence of biochemically defined estrogen receptors. He did not specify the term receptor, but he implied its identity with the biochemically defined type I estrogen receptor.