ASSAYS FOR THE ANALYSIS OF P-GLYCOPROTEIN IN ACUTE MYELOID-LEUKEMIA AND CD34 SUBSETS OF AML BLASTS

Expression of the multidrug resistance (MDR) phenotype is an independe nt prognostic variable in acute myeloid leukemia. Approximately 43-57% of the patients have P-glycoprotein (P-gp) expression. A major drawba ck with the interpretation of Pgp data in AML is the lack of coherence with different analytical assays. We have focused our efforts of P-gp detection on flow cytometry using a dual technique of P-gp staining w ith antibodies for the extracellular epitope (MRK16) and a functional analysis of P-gp using the rhodamine efflux assay and the effect of P- gp inhibitors such as SDZ PSC 833. This technique was combined with th e staining of lineage-specific antigens such as CD34, CD56 and c-kit, In this way, various subsets of AML cells can be identified such as MR K 16(+/-), CD34(+/-) blasts. These cells can be sorted for further ana lysis, such as the molecular expression of P-gp and other pleiotropic drug resistance genes.