Comparative study between histochemical and biochemical estimation of estrogen receptors in tumors

Sucrose gradient analysis (SDGC) was compared with histofluoroassay, using 17 beta-Estradiol-6-carboxymethyloxime-bovine serum albumin-fluorescein isothiocyanate (E2-BSA-FITC) as fluorescent ligand, for the estimation of estrogen receptors (ER) in human breast tumors. No correlation was seen between fluorescent ligand binding capacity by the tumoral tissues on the one hand and ER levels estimated by SDGC on the other hand. The fluorescent ligand had a lower affinity for the receptor than estradiol itself and was contaminated with free estradiol. It was concluded that the absence of correlation between both techniques was for the greatest part due to unspecific binding of E2-BSA-FITC.