Estrogen-dependent release of serum proteins from MCF-7 breast carcinoma cells in vitro

The human breast carcinoma cell line MCF-7, propagated in a chemically defined medium, released alfa-1-antitrypsin and alfa-1-antichymotrypsin to the medium under the influence of estradiol. Furthermore, an estrogen-independent release of antigenic material crossreacting with alfa-1-lipoprotein was demonstrated. In the presence of estrogen, the mean concentration of these proteins in the medium was 38 micrograms/l, for alfa-1-antitrypsin and 5 micrograms/l for alfa-1-antichymotrypsin and 34 micrograms/l for alfa-1-lipoprotein. It is suggested that alfa-1-antitrypsin and alfa-1-antichymotrypsin might be oncogene products of possible significance for MCF-7 tumor growth in vivo, while alfa-1-lipoprotein could be essential for the ability of the MCF-7 cells to proliferate in a chemically defined medium in vitro.