Cultured Human Breast Carcinoma Derived Epithelial Cells Preservation of Defined Phenotypic Traits in Short-Term

Interpretation of primary monolayer culture of organs and tissues with different epithelial cell types demands well-defined criteria for distin guishing between such cells. Epithelial components in breast carcinomas comprise, in addition to carcinoma epithelial cells (CEP), at least two epithelial cell types organized in mammary ductules of normal appearance as an inner layer of luminal epithelial cells (LEP) and an outer layer of basal or myoepithelial cells (MEP) resting on a basement membrane. In a previous study (Petersen and van Deurs, Cancer Res., 46: 20132020, 1986) we have defined a population of CEP in vivo and in vitro, appearing in about 50% of primary carcinomas, by a cytochemical reaction for reduced nicotinamide adenine dinucleotide phosphate neotetrazolium reductase. Carcinoma derived epithelial cells not showing this cytochemical reaction in culture were believed to originate from either carcinoma cells or from mammary ductules of normal or benign appearance. In the present study we show that carcinoma derived NADPH-NT reductase negative cell islets often exhibit phenotypic traits of apparently normal mammary ductules as defined in vivo. Moreover, it is shown that the reductase positive CEP, apart from the reductase reaction, has preserved several other features in culture distinguishing them from cells of apparently normal origin. Thus, whereas reductase positive CEP often consisted of only one cell type, as revealed by phase contrast microscopy, some reductase negative cell islets showed a distinct two-cell-type composition. One cell type exhibited cobblestone-like ap pearance and remained in the center of the islets whereas the other was more loosely arranged and rapidly left the central area by migration below the cobblestone-like cells to the periphery of the islets. Cobble stone-like cells and loosely arranged cells were found by immunocytochemistry to express elements of LEP and MEP phenotype, respectively. LEP phenotype was defined in vivo by expression of milk fat globule membrane antigen and cytokeratins, whereas MEP expressed basement membrane-associated type IV collagen. Computerized image analysis revealed mean population doubling times for cells with MEP phenotype of 1 day and for those with LEP phenotype of 2 days. Both cell types showed a diploid DNA pattern as revealed by fluorimetry. Reduced nicotinamide adenine dinucleotide phosphate neotetrazolium reductase positive CEP expressed milk fat globule membrane antigen and cytokeratins, thus resembling the reductase negative LEP. However, in contrast to LEP, these CEP exhibited distinct intracytoplasmic lumina (in 15-46% of all cells in reductase positive CEP islets from five biopsies). Moreover, reductase positive CEP islets were not associated with cells of MEP-phenotype, and showed population doubling times in the range of 5 days to indefinite. In addition, some CEP were highly aneuploid.