Effects of differentiation inducers on cell phenotypes of cultured nontransformed and immortalized mammary epithelial cells: a comparative immunocytochemical analysis.

We examined the effects of the differentiation-inducing agents 1, 25-dihydroxyvitamin D(3) (calcitriol), phorbol myristate acetate (PMA), the cytokine interferon-gamma (IFN-gamma), and the tumor necrosis factor-alpha (TNF-alpha) alone and in combination with calcitriol on cell growth and differentiation parameters of cultured nontransformed human mammary epithelial cell (HMEC) lines, the chemically transformed HMEC line H184 A1N4, and the human mammary carcinoma cell line CAL51. Cell differentiation was phenotyped by semiquantitative immunocytochemistry using a panel of 15 monoclonal antibodies against marker molecules representing epithelial cell differentiation, cell-cell adhesion processes and malignancy. Cell proliferation of HMEC and H184 A1N4, but not of CAL51 cells was reduced by the agents. Cell phenotypes were analyzed by examining the expression of cytokeratins (pan CK and CK19), the epithelial mucin (MUC1), isoactin, and the blood group-related H type 2 carbohydrate antigen. HMEC and H184 A1N4 cells showed characteristics of basal cells, whereas CAL51 cells resembled a lumenal phenotype. The cell-cell adhesion molecules E-cadherin, intracellular adhesion molecule (ICAM-1), and the tumor markers carcinoembryonic antigen (CEA) and CD44v6 were expressed on all 3 mammary cell lines, with moderate differences. With respect to effects on cell phenotypes, HMEC were sensitive to PMA and IFN-gamma resulting in an increased expression of MUC1, CEA and ICAM-1 molecules. H184 A1N4 cells responded to TNF-alpha in combination with calcitriol by increased expression of pan CK, MUC1, and decreased H type 2 antigen expression, suggesting a transition towards a lumenal phenotype. Furthermore, CEA, ICAM-1 and CD44v6 were increased by TNF-alpha plus calcitriol. In contrast, CAL51 cells were overall less sensitive to differentiation induction attempts; only TNF-alpha stimulated MUC1, isoactin and epithelial cell adhesion molecule (Ep-CAM) expression.