Expression of MDR-1/P-glycoprotein in childhood acute megakaryoblastic leukemia cells

Multidrug resistance is a major clinical problem in chemotherapy of malignant disease. Acute megakaryoblastic leukemia (AMKL) is a rare form of childhood leukemia, and is often more resistant to many anticancer chemotherapeutic drugs compared to other types of childhood leukemia. There have been reports of the increased expression in hematologic malignancy of multidrug resistant (mdr-1) gene, which encodes for a transmembrane glycoprotein P-glycoprotein that acts as an efflux pump for structurally unrelated chemotherapeutic drugs. We investigated the malignant cells of 15 newly diagnosed childhood AMKL patients by immunocytochemical analysis and found P-glycoprotein expression in all samples from these patients. RNA prepared from five patients at the time of presentation confirmed the expression of mdr-1 specific message in all cases by Northern blot analysis. These results imply that malignant cells from all childhood AMKL might express the mdr-1/P-glycoprotein.