Quantitation of human mammary epithelial antigens in cells cultured from normal and cancerous breast tissues

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Abstract
A sensitive radioimmunoassay technique was developed to quantitatite the level of human breast celltype specific antigens on cells from normal breast and from various established cell lines of breast and nonbreast origins. Polyacrylamide gel electrophoresis revealed four major proteinaceous components (150,000; 75,000; 60,000; and 48,000) in human milk fat globule membranes that were used to immunize rabbits in order to elicit antimammary epithelial cell antibody. Antisera obtained were rendered specific by abosorptions and were able to recognize three specific mammary epithelial components of the breast epithelial cell. Human mammary epithelial (HME) antigen expression was highest (1290 ng/106 cells) in normal breast epithelial cells from primary cultures of normal breasts. Lower levels (range: 955 to 330 ng/106 cells) were found in breast epithelial cells from cell lines established from cancerous breast tissue. Cells of nonbreast origins as well as fibroblasts from breast gave much lower values (less than 30 ng/106 cells). On treatment, with trypsin, of two breast epithelial cell lines (MDA-MB-157 and MCF-7) 80 to 85% of their HME antigen expression was lost, suggesting that a majority of these breast antigens reside on the cell surface.