Yin and yang of the plasminogen activator inhibitor

Plasminogen activator inhibitor type one (PAI‑1) is involved in many biological processes, and depending on a disease its overexpression, deficiency or normal level can sometimes produce surprising outcomes. This paper reviews low, high, and normal levels of PAI‑1 in relation to diseases, their incidents, and possible treatment. Also, a role of PAI‑1 in cancer is discussed with attention to “PAI‑1 paradox” and explanation of the possible therapeutic applications using this protein.