Opposite effects of estrogen and catecholestrogen on hormone-sensitive breast cancer cell growth and differentiation

Abstract Catecholestrogens and especially 2-hydroxyestrone (2OH-E 1 ) are estradiol metabolites locally formed in breast cancer cells. The present study demonstrates that the two parent compounds, estradiol (E 2 ) and its metabolite 2OH-E 1 , exert opposite effects on hormone-sensitive breast cancer cell growth assessed by cell counts and transferrin receptor levels, and also on cell differentiation assessed by secreted proteins such as alpha-lactalbumin and gross cystic disease fluid protein (GCDFP-15). The present findings may highlight estradiol regulation in hormone-sensitive breast cancer cells.