Patterns of expression of tumor markers on non-transformed human mammary epithelial cells cultured in vitro.

We have examined the expression of 7 well defined tumor markers/tumor associated antigens (H type 2, X, Y, sialyl-Lea, CEA, MAM-6, and Tn) and a tumor associated antigen defined by a new own monoclonal antibody on non-transformed human epithelial cell lines derived from reduction mammoplasties by means of immunocytochemistry with monoclonal antibodies. Two cell types are discernible: slowly or non-proliferating, lumenal derived (I), and proliferating, stem cell-like, basal cell-derived cells (II). Five out of the 8 tumor markers were expressed on type I cells, and all 8 on type II cells. The number of positive cells varied considerably from a few to 100 per cent depending on the individual markers. The observed patterns proved to be characteristic and reproducible; they appear to reflect the developmental stage of the cells cultured in vitro rather than a direct influence of the culture conditions.