With the observations that estrogen exposure increased expression of FXYD3 in MCF-7 breast cancer cells, and that exposure of these cells to estrogen increased the association of ER with the ZEB1 protein, we set out to determine whether declines in ZEB1 levels would alter the ability of estrogen or tamoxifen to regulate FXYD3 expression. Here, FXYD3 is linked to breast cancer.