POLYPEPTIDE MODULATION IN MCF-7 CELLS BY ESTROGEN AND GROWTH FACTORS

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The purpose of this project was to utilize the established human mammary tumor cell lines (MCF-7, MCF-7gpt (produced by transfection with the Eco-gpt selectable gene marker), MCF-7ras (produced by transfection with Eco-gpt and the v-Hras oncogene) and LY2) to investigate the effect of antiestrogens, estrogen and other growth factors on the polypeptide expression of both cellular and secreted proteins in these cells. The growth factors IGF-I (insulin like growth factor-I) and TGF-alpha (transforming growth factor alpha) are able to elicit many of the growth stimulating responses of estrogen when applied to the MCF-7 human mammary tumor cell line. Analysis of the 2-dimensional polyacrylamide gels from cellular proteins of the MCF-7gpt and MCF-7ras cells which have been treated with 17-beta-estradiol or an ethanol vehicle showed 12 polypeptides which were consistently altered. Of these, four polypeptides were clearly affected the same way by ras transfection and estrogen stimulation. Sixteen secreted polypeptides were altered by at least twofold subsequent to either estrogen or v-Hras. Opposing effects of estrogen and v-Hras were observed for a number of polypeptides, but synergistic effects of v-Hras and estrogen were seen for three polypeptides detected by autoradiography. Studies to ascertain the effects of the growth factors IGF-I and TGF-alpha on the expression and secretion of these polypeptides are in the final stages of analysis. Additional to this are experiments using the anti-estrogen LY117018 to assess the effect on polypeptide expression and secretion from the antiestrogen-resistant cell line LY2 and the MCF-7 cells.