Clinical Significance of CD87 Expression in Acute Myeloblastic Leukemia

CD87 or uPAR (urokinase type plasminogen activator receptor) expression leads to conversion of plasminogen to plasmin to mediate extravasation by proteolytic breakdown of adhesion molecules responsible from cell contact. uPA (urokinase type plasminogen activator) system consists of a proteinase, its receptor uPAR, and two inhibitors (plasminogen activator inhibitor [PAI] 1 and 2). CD87 expression may have implications for diagnosing acute myeloblastic leukemia (AML) and determining its prognosis, as well as for follow-up of minimal residual disease (MRD). In this study we determined CD87 levels in bone marrow or peripheral blood immunophenotypically and investigated its relationship with some prognostic factors in 35 newly diagnosed and untreated AML patients. While there was no significant correlation between CD87 expression and age, sex, admission white cell count, and CD34 expression, a significant relationship was found between CD87 expression and organomegaly. This relationship was prominent in cases with AML showing monocytoid differentiation. No correlation was found between CD87 expression and treatment response. In AML patients hepatosplenomegaly and mucocutaneous infiltrations are associated with increased CD87 expression. Extramedullary extension is common in leukemias with monocytoid differentiation. uPA, by binding to CD87, initiates conversion of plasminogen into plasmin to mediate extravasation of cells through endothelium by proteolytic breakdown of endothelium-associated adhesion molecules. It plays role in adhesion, migration and metastasis of leukemia cells. This condition may also explain the relationship between CD87 and the rate of organomegaly. It may prove a useful marker for follow-up of MRD when detected at the time of diagnosis.