Analysis of estrogen receptors in human breast cancer by assays using monoclonal antibodies and by the dextran-coated charcoal method.

Estrogen receptors (ER) were analyzed in 63 human breast cancers by immunocytochemical assay, and by enzyme-immunoassay, using monoclonal antibodies against human ER protein, and also by the dextran-coated charcoal method. The specific staining was observed only in the nucleus of cancer cells by the immunocytochemical assay, and the presence of nuclear staining by this assay was closely associated with the estimation of the cytosolic ER content by both the dextran-coated charcoal method and the enzyme-immunoassay. In the latter, the cytosolic ER content correspondingly increased with the nuclear ER content. Both the cytosolic and nuclear ER contents correlated well with those obtained by the dextran-coated charcoal method. Furthermore, the cytosolic ER contents obtained by the enzyme-immunoassay and the dextran-coated charcoal method correlated significantly with the age of the patient, but not with the nuclear ER contents. These above mentioned results suggest that ER is present mainly in the nucleus of breast cancer cells and that the cytosolic ER obtained by these two assays is the unoccupied one released from the nucleus.