ABSTRACT
Estrogen binding proteins (ER) have been found in a wide variety of other human tumors including pancreatic carcinomas. Flow cytometry (FCM) began as a tool to automatically count and size individual cells from a flowing cell suspension. Hormone-responsive human tumors include breast, prostate, endometrial, and ovarian carcinomas. In contrast to biochemical analysis, the histochemical detection of ER in frozen tissue sections offers the potential for rapidly estimating the number of ER-positive and -negative tumor cells within a very small tissue specimen. The lack of a quantitative measure of cell-bound fluorescence has precluded precise characterization of ER binding by fluorescent ligands. Resonance energy transfer and the use L. Stryer's ”spectroscopic ruler” offers another potentially powerful application of the FCM methodology. Adapting FCM to the quantitative measure of E-bovine serum albumin-fluorescein isothiocyanate binding in ER-positive tumor cell suspensions produces further evidence for the receptor specificity of this fluorescent ligand.
