Endoxifen and fulvestrant regulate gene expression of estrogen receptor alpha and its co-activators DEADbox5 and 17

Background: Application of anti-estrogens remains a standard therapy in ERα -positive breast cancer. Endoxifen acts as a selective receptor down-modulator of ERα function, while fulvestrant acts as a selective receptor down-regulator via an increased ERα inhibition and degradation. RNA helicases p68 (DDX5) and p72 (DDX17) act as co-activators of ERα. DDX17 expression correlates with decreased Her2/neu levels, extended relapse-free periods, and an increase in overall survival rates. In contrast, DDX5 expression is associated with increased Her2/neu levels and higher tumor grading, but not correlated with relapse-…