Variability in surface antigen expression of human breast epithelial cells cultured from normal breast, normal tissue peripheral to breast carcinomas, and breast carcinomas.

Single-cell heterogeneity and variability in expression of several surface antigens on human mammary epithelial cells in short-term culture were studied with immunofluorescence techniques, using polyclonal and monoclonal antibodies. The cultures, derived from normal breast, a fibroadenoma, a gynecomastia, normal breast tissue peripheral to breast carcinomas, and breast carcinomas and their metastases, were studied after one passage in vitro. The percentage of positive cells varied considerably from one tissue sample to another in all categories from normal to malignant, although there was an overall trend toward a decreasing percentage of positive cells of malignant tissues. The relative antigen content varied 3- to 8-fold among individual samples of cells from normal, peripheral, and carcinoma tissue, while the mean values in the three categories were similar. The single-cell variability in relative antigen content was considerable in all individual samples of normal, peripheral, and carcinoma tissues, as reflected in the high coefficients of variation. However, the coefficients of variation were significantly higher for cells from carcinoma and peripheral tissues [69 +/- 10% (S.E.) and 75 +/- 9%, respectively] than for cells from normal breast (48 +/- 5%). By analyzing in clonal colonies the appearance of quantitative variants in expression of a specific surface antigen, detected with a monoclonal antibody, the carcinoma cells were found to have a 10-fold higher rate of phenotypic variability (mean, 1.21 X 10(-2)/cell/generation) than did cells from normal breast (mean, 0.119 X 10(-2)) and one gynecomastia (0.045 X 10(-2)). Mammary epithelial cells from apparently "normal" tissue peripheral to a carcinoma had an intermediate rate of phenotypic variability (mean, 0.310 X 10(-2)) that was significantly higher than that of the normal tissue.