Cytochemical and competitive protein binding assays for estrogen receptor in breast disease. A comparative study of 62 cases

Comparison of histochemical and biochemical assays for oestrogen receptor in breast tumour tissue

Oestrogen receptors were measured by a histochemical technique in tumour tissue from 45 patients with breast cancer, and the results compared with receptor levels measured by a standard biochemical dextran-charcoal assay. Histochemical measurements were made by incubating frozen sections of tumour tissue with 17-fluoresceinated oestrone, using dithiothreitol to inhibit uptake by low affinity binding sites, and estimating receptor content by the extent of fluorescence seen microscopically. Results from the two assays gave varying estimates of receptor concentration, with 66% of patients classed as receptor-positive by the biochemical assay, and 44% of patients classed as receptor-positive using the histochemical technique. Because of these discrepancies the histochemical assay cannot be considered a direct substitute for biochemical receptor measurements. Progesterone receptor was detected by biochemical measurement in 80% of the subgroup of patients who were positive for oestrogen receptor in both assays. The histochemical assay may thus identify a subset of those patients considered oestrogen receptor-positive by conventional receptor assays, and this group may be more likely to respond to hormonal therapy. However, whether the histochemical method provides a predictive measurement for endocrine responsiveness which is superior to standard progesterone receptor assay remains to be determined.

Determination of steroid hormone-dependency of tumours utilizing tissue sections. Survey of histochemical techniques and their application in surgical pathology

The growth of neoplasms originating from steroid hormone target tissues may be hormone-dependent. It has been clearly demonstrated that the oestrogen and/or progestagen receptor status predicts the response to endocrine treatment and the prognosis of breast cancer. However steroid receptor determination in tumour cytosols has several limitations, which can partly be resolved by (immuno) histochemical detection of steroid hormone-responsive tumour cells. A variety of histochemical techniques including autoradiography of tritiated steroids, immunohistochemistry with antibodies to steroid hormones, histochemistry with fluorescent ligands of low molecular weight and fluorochrome- or enzyme-labelled macromolecular probes are discussed. It is concluded that there is as yet no substantial evidence that these methods visualize steroid receptors or detect steroid hormone-responsiveness of tumour cells. On the other hand, immunohistochemical demonstration of oestrogen receptors with monospecific antibodies seems validated and indications have been obtained that this information is clinically relevant. Recent developments suggest that immunocytochemistry of receptors and specific hormone-induced proteins, flow cytometric analysis and probably hybridocytochemistry in the future will help to improve management of steroid hormone-dependent tumours.

Histochemical estrogen binding. An independent predictor of recurrence and survival in stage II breast cancer

Cox's proportional hazards regression model was used to analyze the prognostic significance of multiple variables affecting recurrence and survival in patients with Stage II breast cancer. Among the variables were biochemical estrogen (ER) and progesterone receptor (PgR) values and results of a histochemical estrogen-binding assay using a fluoresceinated bovine serum albumin-estradiol conjugate where carrier and label were bound at position 17. In 190 cases ER and PgR were not found to be significantly associated with either disease recurrence or patient survival. On the other hand, patients with tumors that were demonstrably "rich" in estradiol ligand conjugate binding by histochemistry experienced both a longer disease-free interval (P less than 0.03) and survival (P less than 0.02) than did patients whose tumors were "poor" in conjugate binding or showed a heterogeneous population of positively and negatively stained cells. A patient with a tumor rich in estrogen binding was five times more likely to survive than a patient with a neoplasm that was poor in estrogen binding by histochemistry. These results indicate that the histochemical technique used provides new and independent parameters for determination of prognosis in Stage II breast cancer.

Heterogeneous estrogen receptor levels detected via multiple microsamples from individual breast cancers

Twenty-six surgical breast cancer specimens were subjected to multiple estrogen receptor (ER) assays with a microsample technique. In most tumors there were large variations in ER levels in samples taken from different regions of the same tumor. After correction of individual samples for differences in carcinoma content, such variations were not abolished. Nine of the 26 breast cancers, although positive overall, were devoid of ER in some regions. For ER-positive tumors the average coefficient of variation (CV) for intratumor ER levels was 86%, with a range from 25% to 200%. This is well above the CV obtained with repeat samples of homogeneous tissue (14%). These results suggest that many ER-positive cancers may be composed of cells with a variety of ER levels. An assessment of individual intratumor ER variability may have biologic and clinical significance.

Biochemical and histochemical analysis of steroid hormone binding sites in human primary breast cancer

Mammary carcinoma tissue from 514 primary breast cancer patients were all biochemically and histochemically analyzed for both estrogen receptors and progesterone receptors. The dextran-coated charcoal (DCC) method measured the ER and PR as defined by Scatchard analysis, ligand competition experiments and target organ specificity. The ligands, estradiol-6-carboxymethyloxime-BSA-fluoresceine isothiocyanate and hydroxyprogesteronehemisuccinate-BSA-tetramethylrhodamine isothiocyanate, used for histochemistry, did not bind to either ER or PR and were mainly bound to the membrane fraction of isolated breast cancer cells. Fluorescence was not specifically inhibited by estrogens or progestogens. In addition, "estrogenic" always coincided with "progestogenic" fluorescence. The binding of the fluoresceine compounds to tissue slides depended on the large steroid hormone substitution on the bovine serum albumin molecule. Clinical parameters, known to be related to ER and PR did not correlate with the histochemical results. The observations indicated the impossibility of specific steroid receptor detection by the histochemical method. Therefore, up to the present, evaluation of hormone dependency and prognosis in human breast cancer cannot be based on this approach.

Heterogeneity of estrogen binding sites in breast cancer: morphologic demonstration and relationship to endocrine response

Breast cancer specimens from 184 patients were analyzed for estrogen binding by two different histochemical techniques using conjugates of estradiol, bovine serum albumin, and fluorescein. In one conjugate estradiol was bound at position 6, in the other at position 17. Results were in agreement in 64% (p less than .001), but obvious differences in ligand distribution were noted. Results were also correlated with estrogen receptor (ER) analysis by dextran-coated charcoal assay (DCC) and were in accord in 65% and 67% of specimens respectively (p less than .001). In 114 cases, the tissue samples were also studied with the estrogen receptor immunocytochemical assay (ERICA) of Greene and his colleagues, which employs monoclonal antibodies to ER protein. Results were in accord with DCC in 86% (p less than .001). The pattern of staining with ERICA differed from that of either histochemical method. In 43 cases assay results were correlated with clinical endocrine response. Overall, the best statistical prognostic parameters were obtained with ERICA. Analysis of combined assay results revealed that patients with assays positive by all techniques were the most likely to respond to hormonal treatment (p less than .001), whereas if one or more assays were negative the chances for a good response were significantly less favorable. These data suggest that DCC and ERICA are both a measure of the same estrogen binding site (type I) while the histochemical methods apparently identify two other separate and distinct sites (putative type II sites). A degree of positive interaction may exist between these multiple estrogen binding sites.

Immunohistologic localization of estrogen receptors in breast cancer with monoclonal antibodies. Correlation with biochemistry and clinical endocrine response

Breast cancer specimens from 114 patients were assayed for the presence of estrogen receptors (ER) utilizing highly specific, monoclonal antiestrophilin antibodies and the peroxidase-antiperoxidase technique. Results were compared with conventional ER determinations by the dextran-coated charcoal method (DCC) and were in agreement as to positivity and negativity in 86%. Semiquantified immunocytologic assay results were in accord with the level of ER as measured by DCC in 66%. The tumors studied included 43 from patients with Stage IV disease where clinical response to hormonal manipulation was known. In the latter group, the immunohistologic method had a sensitivity similar to that of DCC but showed a superior positive predictive value and a significantly better specificity. These results indicate that this new method is a valuable laboratory tool, enabling prediction of hormone responsiveness in advanced mammary carcinoma and capable of performance at the community hospital level.

Estrogen and progesterone receptors in congenital melanocytic nevi

Using fluorescent-labeled estrogen and progesterone, congenital nevi from fifteen patients, six male and 9 female, were studied for the presence of corresponding cytoplasmic receptor binding. Similar studies were done in a control population of twenty-one patients, ten male and 11 female, with acquired intradermal nevi. Congenital nevi contained high concentrations of estrogen-binding and progesterone-binding nevus cells in both male (6/6) and female patients (5/9). Lesser concentrations of estrogen-binding and progesterone-binding nevus cells were found in congenital nevi from the remaining four female patients. In contrast, acquired intradermal nevi from the control group of patients had little or no detectable estrogen or progesterone binding. These data indicate that congenital nevi are similar in hormonal-binding properties to melanomas and dysplastic nevi, in contrast to acquired intradermal nevi.

Estrogen and progesterone receptors in primary cutaneous melanoma

Using a variety of techniques, estrogen and progesterone receptors have previously been identified in variable percentages of malignant melanomas. We examined 10 primary superficial spreading melanomas (SSM) with a fluorescent hormone-binding technique for estrogen and progesterone cytoplasmic receptors. Of these 6 SSM were markedly positive for estrogen and progesterone binding. Patients with dysplastic nevus syndrome (DNS) or a family history of DNS were markedly positive for estrogen and progesterone binding. A single patient with lentigo maligna and another patient with lentigo maligna melanoma were negative for estrogen and progesterone binding. None of the 21 control intradermal nevi examined for estrogen and progesterone binding exhibited marked positivity.

Radiochemical determination of estrogen receptors in cryostat sections of target tissues

A radioreceptor assay on unfixed cryostat sections has been developed. Mounted and dried sections were incubated with radiolabeled estradiol in the absence and presence of an excess of diethylstilbestrol and washed with buffer. Binding of radiolabel to sections was measured by direct liquid scintillation counting. Also protein-bound radioactivity which eluted from the sections was determined with a dextran-coated charcoal assay. Parallel sections were used for histological staining and protein determination. Scatchard analysis showed the presence of specific saturable binding sites for estradiol with dissociation constants in the 0.1-1.5 nM range. It is concluded that these high affinity and limited capacity (type I) binding sites represent estrogen receptors. The ligand-binding activity of section-bound estrogen receptors did not decrease upon dry storage up to 20 h at 4 or 23 degrees C prior to assay. During aqueous incubation a significant amount of receptor, representing about 40-60% of the total tissue content, elutes from the sections. Steroid specificity was proven by incubation with excess androgen, progestogen or corticoid instead of diethylstilbestrol or estradiol. With these ligands no significant competition was found. Tissue specificity was demonstrated by a very low level of specific estradiol binding to cryostat sections of rat skeletal muscle, spleen and intestine and by a moderate level in rat liver.