Clinical studies revealed that high intratumoral levels of uPA‐PAI‐1 heteromers predict impaired overall survival (Andreasen etal, 1997; Schmitt etal, 1997; Knoop etal, 1998; Duffy etal, 1999; Foekens etal, 2000; Janicke etal, 2001; Sten‐Linder etal, 2001; Look etal, 2002; Manders etal, 2004b) and treatment response (Harbeck etal, 2002a; Harbeck etal, 2002b; Manders etal, 2004a; Manders etal, 2004c) in early breast cancer. Here, SERPINE1 is linked to breast cancer.