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.