An update on the immunohistochemical localization of estrogen receptors in mammary carcinomas utilizing polyclonal anti-receptor antibodies

Cell Interactome: Good Neighbors or Bad Neighbors

We report an interesting finding that cellular distribution and interactions between neighboring cells modulate protein expression and localization. MCF7 breast cancer cells, which express ERb, were cultured in estrogen free medium. ERb exhibited a unique migration pattern that was dependent on cell density and proximity. This findings attest to a novel mechanism other than ligand-receptor one. Since cells were grown in conditioned culture media, the only factor influencing protein distribution is cell-cell proximity (cell-cell interactions). Thus, hormonal receptors may function independently from their ligand. in addition, physical intercellular interactions may function as a non-molecular factor inducing gene expression and activation.

Nuclear binding of the estrogen receptor: a potential predictor for hormone response in metastatic breast cancer

We have previously described an in vitro immunohistochemical test employing anti-receptor antibodies, for demonstrating the nuclear binding characteristics of estrogen receptors (ER) in breast carcinomas. Based on a retrospective analysis of twenty-five patients with estrogen receptor-positive (ER+) breast cancer who were treated with hormone therapy and whose clinical responses were evaluable, we were able to demonstrate that this test may be valuable to predict which, among the ER+ tumors (whether or not they are progesterone receptor positive, PR+), are likely to respond to hormone therapy and which may fail. While tumors in which ER exhibited abnormalities in nuclear binding behavior (ligand-independent nuclear binding or no nuclear binding) failed hormone therapy (16 out of 19 patients), those in which nuclear binding of ER appeared normal (ligand-dependent) in the in vitro test, responded to hormone therapy (5/6 patients). While our previous report dealt with the procedural details, specificity of the reagents, and the design of the study, this report addresses the clinical aspects of this study and response correlation.

Nuclear location of hormone-free estrogen receptors by monoclonal antibodies could be a tissue-fixation dependent artifact

The 'two-step' model proposed by Jensen and his collaborators for explaining estrogen action conceptualized hormone-free estrogen receptors (ER) to be cytoplasmic, and hormone-filled, transformed ER to be nuclear. Applying monoclonal antibodies which recognized epitopes in ER and formaldehyde-fixed tissues, King et al demonstrated exclusively nuclear staining in target tissues utilizing immunoperoxidase technique. Recently these antibodies have become commercially available enabling other investigators to conduct studies. In this report, using these monoclonal antibodies we have demonstrated that a change in the concentration of formaldehyde alters the staining pattern yielding cytoplasmic instead of nuclear staining in calf uterus, MCF-7 cells, and ER(+) human breast cancer. In addition, neutralization of the antibody activity was not achieved with freshly prepared ER(+) cytosols. Formaldehyde-treated cytosols were essential. These results ought to caution investigators in determining in vivo location of antigens based on the staining pattern obtained in fixed tissues. Furthermore, this effect of formaldehyde on estrogen receptors may be applicable to other steroid hormone receptors.

Histochemical studies of human breast cancer using a monoclonal antibody against an oestrogen receptor-related antigen

The presence or absence of an oestrogen receptor-related antigen in breast tumours has been examined histochemically using a monoclonal antibody ('Ds' - Coffer & King, 1981). In frozen sections, fixed either by the method of Tamura et al. (1980) or in methanol, staining was apparent in 14/24 (58%) and 22/26 (85%) of the breast cancers respectively. In paraffin sections fixed in ethanol, staining was present in 25/33 breast cancers (76%). In either type of section, staining was predominantly in the cytoplasm of the epithelial cells. When staining was scored by independent observers (2 or 3) and related to the tumour oestrogen receptor activity, determined by a standard biochemical technique, antigen was present in both receptor-positive and receptor-negative tumours. No significant association was found between the presence of antigen and receptors in the frozen sections, but for the series of paraffin sections, there was a weak association (r = +0.48) between the presence of the two proteins. Histochemical processing of paraffin sections from 9 tumours under conditions of higher sensitivity increased the staining significantly in 2/9 tumours, but did not alter the relationship between staining and receptor status. Six tissues were stained after exposure to 'receptor-translocating' conditions (25 degrees C/2 nM oestradiol/both for 1 h): this did not consistently change the subcellular staining pattern, though all tissues tended to stain more after exposure to 25 degrees C. Staining was not blocked by absorption of the D5 antiserum with a variety of pure proteins or human serum but at higher concentrations (approx. 2-15 mg protein ml-1), extracts from human uterus, an oestrogen-receptor-positive breast cancer and an oestrogen-receptor-negative breast cancer all effectively abolished staining in sections from another breast cancer. These results are consistent with other reports suggesting that the D5 antibody detects an antigen which is not the oestrogen receptor, but which may be associated with the receptor in its tissue distribution.

Estrogen binding sites and estrophilin histochemistry and their correlation with oestrogen receptor biochemistry

Since the application of mono- and poly-clonal antibodies to the estrogen receptor protein (estrophilin) classically admitted opinions about the interactions between estrogens and their target cells have changed. Biochemical assays of ER have been shown to provide false negative results; the key-mechanism seems to be located at the nuclear level, while until now most emphasis was put on cytosolic ER. In histochemistry, apparently contradictory reports have emphasized either cytoplasmic or nuclear labelling of estrogen binding sites (EBS). A lot of supputations have tried to explain in vitro translocations from the cytoplasm to the nucleus according to the physicochemical conditions which were used. Reading of some articles gives the impression that EBS histochemistry is yet an established and reliable method; commercially available histochemical "kits" may support this false idea. Therefore it is absolutely mandatory to intend to remain cautious and critical. Stepwise our knowledge is increasing; it is absolutely clear that the problems which did rise thanks to the "contradictory" histochemical studies gave a new impetus to both biochemical and histochemical research. Immunohisto- and cyto-chemistry of EBS and estrophilin go on in parallel and in correlation with biochemistry.

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.

Semiquantitative oestrogen receptor assay in formalin-fixed paraffin sections of human breast cancer tissue using monoclonal antibodies

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