Serpin E1, also known as plasminogen activator inhibitor-1 (PAI-1), is a member of a superfamily of serine protease inhibitors that are produced primarily by the endothelium (cells lining the endothelium of blood vessels), but also secreted by other types of tissue such as adipose tissue. Serpin E1 is a major inhibitor of urokinase and tissue type plasminogen activators (uPA and tPA). The PA-fibrinolytic enzyme system is involved in a variety of physiological and pathological processes such as fibrinolysis, fibrosis, angiogenesis, wound healing, invasion and metastasis of tumor cells. For example, high levels of uPA and Serpin E1 are associated with poor prognosis in patients with breast cancer, and studies have confirmed that uPA and Serpin E1 are the most reliable biomarkers with grade 1 clinical value. In addition to breast cancer, Serpin E1 is also involved in many other diseases such as metabolic syndrome, asthma, major depressive disorder (MDD), and age-related diseases. The absence of Serpin E1 in the plasma will lead to abnormal bleeding, and high levels of Serpin E1 are associated with genetic susceptibility.