SERPINE1 and cancer: The plasminogen activator (PA) system, which consists of two serine proteases, the urokinase PA (uPA) and the tissue-type PA (tPA), their two serpin inhibitors (PAI-1 and PAI-2), and the glycolipid-anchored receptor for the uPA (uPAR), is involved in cancer progression, since it enhances both distant metastasis and direct invasion.