SERPINB2 and leukemia: SERPINB2, also known as plasminogen activator inhibitor type 2 (PAI-2), is highly increased in response to the classic terminal cellular differentiation agent retinoic acid in multiple cell types, such as epidermal keratinocytes12, peripheral blood mononuclear cells13, and promyelocytic leukemia cells14, 15, indicating that SERPINB2 is involved in the process of cell differentiation.