Elisabetta Marchetti

Affinity cytochemistry visualizes specific estrogen binding sites on the plasma membrane of breast cancer cells

Abstract A study has been initiated on mapping specific interaction of estrogen with the plasma membrane of estrogen-target cells. Fluorescent estrogen analogues have been used in order to obtain the dynamic display and positioning of estrogen binding sites at the surface of intact breast cancer cells. The binding of these fluorescent ligands to the plasma membrane shows a major saturable component with structural specificity for natural estrogen. Moreover, estrogen binding sites display a temperature-sensitive lateral mobility in the plane of the membrane, leading to the formation of small clusters, larger patches and polar caps. Different steroid specificity indicates that these binding sites on the plasma membrane are distinct from classical cytosol estrogen-receptors. The actual function of these estrogen binding sites is unknown, but their location and properties are at least consistent with the idea that they might be involved in the cell control by estrogen.

Commentary on human mammary preneoplasia. The estrogen receptor-promotion hypothesis

In the carcinogenic process, promotion is the process whereby an initiated tissue develops focal proliferations which act as proximate precursors. The evidence obtained from the immunocytochemical staining by monoclonal anti-receptor antibodies indicates that the early steps (atypical hyperplasias) in the carcinogenic process of the breast show an increased and homogeneous expression of the estrogen receptor. These observations suggest that the persistent sensitivity to estrogen may be critical in sustaining the growth of mammary preneoplastic changes and their progression to ultimate precursors and to invasive cancer.

Pathophysiology of estrogen receptors in mammary tissue by monoclonal antibodies

Identification of preneoplastic lesions of the breast has mainly rested on morphological grounds, supported by epidemiological data. These studies assign a definite precancerous potential to a group of atypical hyperplastic lesions and in situ carcinoma. In spite of much effort no criteria are yet available to understand which, among these lesions, is committed to infiltrative growth, in other words, to understand the risk to a single patient. Estrogens are know to play a critical role in the etiology of breast cancer. The hypothesis is investigated that this role is dependent on a modified expression of their receptor. To approach this question estrogen receptor expression was traced by specific monoclonal anti-receptor antibodies and immunocytochemistry, on a spectrum of breast tissue changes, from normal tissue to infiltrating cancer. Estrogen receptor expression is heterogeneous in normal tissue and in infiltrating cancer, and on the contrary is homogeneous in proliferative atypical lesions and in in situ carcinomas. Present results show that receptor expression is enhanced and becomes homogeneous, maybe constitutive, in atypical hyperplasia and in in situ carcinoma and that this phenomenon could subserve important changes of proliferative capacity which are necessary and possibly sufficient for autonomous growth.

Expression of p21 ras gene products in breast cancer relates to histological types and to receptor and nodal status

SummaryExpression of the p21 product of theras gene family was investigated in a series of 142 infiltrating primary breast tumors by two specificras p21 monoclonal antibodies with an immunocytochemical technique. The majority of tumors demonstrated a varying number of positive cells. A significant association between p21 expression and tumor histotype was found: among ductal carcinomas the comedo variety was always positive; conversely, lobular tumors were more frequently negative. Nodal status was recorded for all patients. A significant difference was found in nodal status with respect to p21 expression: tumors with more than 50% positive cells were more often N+. Estrogen receptor (ER) status was determined in 77 tumors. Tumors with higher levels of p21 contained a high percentage of estrogen receptor positive cells.The present results show that p21 expression in human breast cancer could be a marker of tumor aggressiveness and might thus improve the predictive power of known prognostic factors such as estrogen receptor and nodal status.

The plasma membrane as an additional level of steroid-cell interaction

Abstract Specific binding sites for estrogen have been traced on the plasma membrane of estrogen-target cells by means of fluorescein-labelled estrogen derivatives. The occurrence of these sites of steroid-cell interaction additional to specific classical receptors is discussed, with special regard to their possible role in the cell economy.

CLINICAL USEFULNESS OF ESTROGEN RECEPTOR IMMUNOCYTOCHEMISTRY IN HUMAN BREAST CANCER

We assessed the reliability of the immunocytochemical assay of estrogen receptor (ER-ICA) as a marker of clinical outcome. Relapse-free interval (RFI) and overall survival (OS) according to ER-ICA status were retrospectively evaluated on a series of 210 patients who had undergone surgery for primary breast cancer between January 1985 and December 1988. ER assay by the dextran-coated charcoal method (DCC) was also performed in 189 tumors. A significant positive correlation was found between the DCC and ER-ICA assays, with an overall agreement of 79 %. ER-ICA status showed a prognostic predictive power with respect to OS and RFI in the whole series of patients and in the subset of node-positive patients. It was also a marker of outcome with respect to OS in the subsets of node-negative patients and patients with tumors ≤ 2 cm in diameter. Moreover, the predictive value of the ER-ICA assay was higher than that of the DCC assay in the present study. These findings emphasize the clinical usefulness of the ER-ICA assay as a measure for prognosis.

Intracellular flow of particulate steroid-receptor complexes in steroid target cells.

SummaryThe structural expression of nuclear transportation of receptorbound oestradiol was investigated by immunoelectron microscopy on human breast cancer cells. In oestradiol-treated cells during transportation, oestradiol antibodies attached to cytoplasmic oestradiol-bearing particles which seemed to interact with the nuclear membrane. These particles, subserving the intracellular flow of steroid-receptor complexes, could constitute a special cellular system of macromolecular transport, communication and compartmentalisation.

Immunohistochemical expression of c-erbB-2 in human breast cancer by monoclonal antibody: correlation with lymph node and ER status.

c-erbB-2 Protein expression was investigated in a series of fifty primary breast cancers by means of a specific monoclonal antibody and immunocytochemistry. Specific staining was observed at the plasma membrane level of neoplastic cells, according to the reported localization of c-erbB-2 protein. Sixty-four percent of tumors scored positive, with a variable amount of stained cells. The rate of protein expression was found to exceed the reported gene amplification. No relationship was observed between c-erbB-2 protein staining and age, meno pausal status or histologic subtypes. An inverse association was found between cerbB-2 protein staining and estrogen receptor content of tumors, assayed by immunocytochemistry. A positive relationship was observed between c-erbB-2 protein expression and presence of axillary node metastasis. These findings suggest that c-erbB-2 protein expression is a marker of tumor aggressiveness and that its prognostic power deserves further investigation both in node-positive and node-negative patients.