In CCH-induced VD, ROS is primarily produced by NADPH oxidase, which is a multi-subunit complex composed of cytoplasmic subunits (p47phox, p67phox, and p40phox) and membrane subunits (gp91phox, p22phox, and Rac) [24]. This evidence concerns the gene NCF2 and columnar cell hyperplasia of the breast.