To address this hypothesis, we restored DKK3 expression in two basal-like (MDA-MB-436 and MDA-MB-231) and two luminal-like breast cancer cell lines (MDA-MB-453 and MCF-7) by stable transfection with a full-length DKK3 cDNA in a pcDNA3.1/V5-His-TOPO expression vector (DKK3 clones) or an empty vector (mock clones). Here, DKK3 is linked to breast cancer.