Effects of steroid-free fetal serum and steroid supplementation on MUC1 gene expression in human breast cancer cell line MCF7

MUC1 is a gene expressed by many normal epithelial tissues and aberrantly expressed by carcinomas. Studies regarding expression of MUC1 in endometrial tissues and and the constitution of its promotor region suggest a possible role for hormonal regulation of this gene. The aim of the present work was to evaluate the regulation of MUC1 expression by 17β-estradiol (E₂), progesterone (Pg) and by steriod-free fetal calf serum (FCS) in the hormone-sensitive cell line MCF7, MUC1 mRNA proved to be detectable by means of Northern-blot analysis in MCF7 cells, and its levels were strongly increased cells grown with 10% steriod-free FCS. By contrast, the steady-state MUC1 mRNA levels of steriod-supplemented cells did not change compared to those of unsupplemented cells (controls). In conclusion, MUC1 expression is regulated by substances present in the steriod-stripped FCS (growth factors, e.g. Insuline like Growth Factor). The lack of any observed MUC1 modulation by steroids could be due to: (a) a low FCS concentration preventing the manifestation (permissive action) of possible gene regulation; (b) an immediate stimulatory a effect occurring in the first phases of the treatment, which could be subsequently be lost.