PTGS2 and breast cancer: It is also found that downregulation of miR-101 increases the transmigration of breast cancer cells through the brain endothelium in vitro by inducing prostaglandin-endoperoxide synthase-2 (PTGS2, also known as COX-2), expression in cancer cells and miR-101 mediates its effect by modulating COX-2-MMP1 (Matrix Metalloproteinase-1) signaling pathway [70].