An Apocrine Membrane Antigen With Polarized Distribution and Hormonally Regulated Expression in Human Endometrial and Mammary Carcinoma Cell Lines

The topographical distribution and characteristics of an apocrine epithelial differentiation antigen (AEA) were studied in one endometrial adenocarcinoma cell line (HEC-1-B) and two mammary carcinoma cell lines (MCF-7 and T47-D), using an antiserum raised against glycoproteins which had been isolated from human milk fat globule membranes. Immunofluorescent staining of HEC-1-B and MCF-7 cells grown in monolayers, or of histological sections of cells grown in fibrin sponges, revealed a strictly polar distribution of the antigen. The antigen was present only in the dorsal-apical cell membrane. In contrast, T47-D cells grown under identical conditions displayed a nonpolar membrane distribution of the antigen. Detergent lysates of HEC-1-B, MCF-7 and T47-D cells, surface-labeled by the PI(sodiumetaperiodate)-NaB3H4 method, were immunoprecipitated and analysed by SDS-PAGE (sodium dodecyl sulphate polyacrylamide gel electrophoresis). Two closely spaced bands having an apparent MW of 315-290 kD (kilodalton) (HEC-I-B), 330-295 kD (MCF-7) and 320-270 kD (T47-D). The surface expression of the antigen was found to be hormonally regulated. Cultivation of HEC-1-B and MCF-7 in the presence of prolactin increased the amount of antigen. The T47-D cells responded only weakly to prolactin, but displayed enhanced antigen expression after treatment by estrogen and/or progesterone, as quantified by 125I protein A radioimmunoassay. The behaviour of the membrane antigen reported here provides a new and interesting marker for the differentiation and maintenance of polarity in cultured malignant cells of secretory epithelial origin.