Effect of bile acids and estradiol on thymidine incorporation into DNA in MCF-7 and MCF-10A breast cell lines.

Bile acid conjugates are found in human breast cyst fluid in average concentrations about 50-fold greater than those in blood. Because epidemiologic studies have linked colon and breast cancer and aberrant bile acid profiles are associated with colon cancer risk, we decided to study the influence of bile acid conjugates (glycochenodeoxycholic acid, glycodeoxycholic acid, glycocholic acid, and glycolithocholic acid) on thymidine incorporation into DNA in cancer (MCF-7) and noncancer (MCF-10A) human mammary cell lines. The two lines responded differently. In MCF-7, bile acids, except for glycolithocholic acid, stimulated thymidine incorporation. Estradiol caused even greater stimulation, an effect that was not influenced further by the addition of bile acids. Bile acids suppressed incorporation in MCF-10A cells. Estradiol at 1 nM had no effect, but 10 nM estradiol was stimulatory. In most cases bile acids appeared to diminish the incorporations observed with estradiol alone, but not significantly. The relevance of these studies to the possible impact of bile acids on the course of fibrocystic disease of the breast would require further investigation.