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 aberran tly expressed by carcinomas. Studies regarding the expression of MUC1 in endometrial tissues and the constitution of its promoter region sug gest a possible role for hormonal regulation of this gene. The aim of the present work was to evaluate the regulation of MUC 1 expression by 17 beta-estradiol (E(2)), progesterone (Pg) and by steroid-free fetal calf serum (FCS) in the hormone-sensitive cell line MCF7. MUC1 mRNA p roved to be detectable by means of Northern-blot analysis in MCF7 cell s, and its levels were strongly increased in cells grown with 10% ster oid-free FCS. By contrast, the steady-state MUC1 mRNA levels of steroi d-supplemented cells did not change compared to those of unsupplemente d cells (controls). In conclusion, MUC1 expression is regulated by sub stances present in the steroid-stripped FCS (growth factors, e.g. Insu lin-like Growth Factor). The lack of any observed MUC1 modulation by s teroids could be due to: a) a low FCS concentration preventing the man ifestation (permissive action) of possible gene regulation; b) an imme diate stimulatory effect occuring in the first phases of the treatment , which could subsequently be lost.