[Estrogen-induced proteins secreted by MCF7 human breast cancer cells stimulate their proliferation].

In the MCF7 human breast cancer cells, estrogens stimulate in vitro cell proliferation and biosynthesis of specific proteins which are released into the culture medium; the most abundant of these is a 52,000 dalton glycoprotein. Conditioned media from E2-treated MCF7 cells stimulate the growth of E2-deprived MCF7 cells, whereas conditioned media from untreated control cells are ineffective. At protein concentration greater than 5 micrograms/ml, an inhibitory effect was also obtained with control media. The mitogenic factors of these conditioned media are non-dialysable, sensitive to temperature and proteases and adsorbed on Con A Sepharose. The cell surface of MCF7 cells, examined by scanning electron microscopy, is differentially affected by these two types of conditioned media. We conclude that estrogens may stimulate the growth of breast cancer cells indirectly via the induction of glycoproteins acting as growth factors.