Enzyme immunoassay and Scatchard plot estimation of estrogen receptor in gynecological tumors

Tissue samples of three endometrial carcinomas, seven ovarian carcinomas, and 24 mammary carcinomas were analyzed for estrogen receptor (ER) by enzyme immunoassay (EIA) and a conventional dextran-coated charcoal (DCC) method. In addition, ER and progesterone receptor were assayed by DCC only in 68 ovarian carcinoma specimens. All three endometrial cancer specimens showed elevated ER values by both assays. As with mammary cancers the ER-EIA values tend to be higher than DCC values. It was intriguing to note that negative Scatchard plot data resulted in residual ER levels in the EIA system. Also four ovarian cancer specimens with negative ER values by the DCC assay had detectable levels by ER-EIA, and three of these four had ER-EIA values less than or equal to 10 fmol/mg of protein. Of the ten breast cancers with negative DCC values, seven were less than or equal to 10 fmol/mg of protein by the ER-EIA. Good correlation (r = 0.88) between EIA and Scatchard plot data was calculated from ER data of 24 mammary carcinoma tissue samples. Receptor assays in 68 ovarian cancer patients indicate that ER determinations should become a useful tool in the management of patients bearing this carcinoma. In addition, receptor determinations may improve the possibility of predicting which well differentiated Stage I ovarian carcinomas are likely to recur. Present data combine to suggest that ER-EIA may become a useful diagnostic laboratory tool.