SNAI1 and breast cancer: In a recent study, [D-Ala2, D-Leu5]-enkephalin (DADLE) not only enhanced migration of DOR-expressing human MCF-7, murine T47D (epithelial origin), and human MDA-MB-231 (mesenchymal origin) breast cancer cells, which was reversible upon exposure to naltrindole, but also upregulated SNAIL in all cell types [51].