ESTROGEN-RECEPTOR DETERMINATION IN ENDOMETRIAL CARCINOMA - LIGAND-BINDING ASSAY VERSUS ENZYME-IMMUNOASSAY

We compared concentrations of cytosolic estogen receptors (ERc) measur ed in 35 postmenopausal endometrial carcinomas by ligand binding metho d (LBA) (dextran-coated charcoal assay) and enzyme immunoassay (EIA). Correlations between ERc, nuclear estrogen receptors (ERn) determined by EIA, and cytosolic progesterone receptors (PR) measured by LBA were also studied. While ERc concentrations determined by LBA and EIA were highly correlated (r: 0.94), ERc values detected by LBA were approxim ately twice those found by EIA (median values of ERc: 155 vs. 64 fmol/ mg cytosol protein, DCC vs. EIA). The percentages of ERc positive tumo rs were 89% by LBA and 77% by EIA. The median fraction of total ER pre sent as ERn was 63%. PR levels correlated positively with ERn concentr ations (r: 0.73). We explore possible reasons why greater concentratio ns of ERc are determined by estradiol binding than by the ER-EIA kit i n endometrial cancer.