ETS1 and breast cancer: The involvement of Ets‐1 in the invasiveness and metastasis of breast cancer cells is associated with the transcriptional activation of genes encoding matrix metalloproteinases (MMPs), proteins that degrade the extracellular matrix, such as MMP1, MMP3 and MMP9 [18, 19, 20], and plasminogen activator inhibitor‐1 (PAI‐1), an inhibitor of urokinase‐type plasminogen activator (uPA) that promotes cells migration [14, 21].