SERPINE1 and breast cancer: In contrast to our findings, however, uPA‐PAI‐1 heteromers have previously been reported to exhibit direct (e.g., pro‐proliferative) effects on MCF‐7 and MDA‐MB‐435 breast cancer as well as HT 1080 fibrosarcoma cells by utilizing VLDLr (Webb etal, 1999; Webb etal, 2001).