SOAT transportssulfated steroid hormones into specific targetcells and thereby contributes to the overall regulation of steroidresponsive cells and organs.18−21 SOAT is highly expressed in the breast cancer tissue,in particular in specimens showing ductal hyperplasia, intraductalpapilloma, atypical ductal hyperplasia, intraductal carcinoma, andinvasive ductal carcinoma.22,23 In breast cancer cells,SOAT-mediated transport of estrone-3-sulfate significantly stimulated in vitro cell proliferation, while SOAT inhibitors blockedthis effect. The gene discussed is SLC10A6; the disease is ductal breast carcinoma in situ.