EXPRESSION OF MDR-1 P-GLYCOPROTEIN IN CHILDHOOD ACUTE MEGAKARYOBLASTIC LEUKEMIA-CELLS/

Multidrug resistance is a major clinical problem in chemotherapy of ma lignant 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 ma lignancy of multidrug resistant (mdr-1) gene, which encodes for a tran smembrane glycoprotein P-glycoprotein that acts as an efflux pump for structurally unrelated chemotherapeutic drugs. We investigated the mal ignant cells of 15 newly diagnosed childhood AMKL patients by immunocy tochemical analysis and found P-glycoprotein expression in all samples from these patients. RNA prepared from five patients at the time of p resentation confirmed the expression of mdr-1 specific message in all cases by Northern blot analysis. These results imply that malignant ce lls from all childhood AMKL might express the mdr-1/P-glycoprotein.