Expression of multidrug resistance P-glycoprotein in myeloid progenitor cells of different phenotype: comparison between normal bone marrow cells and leukaemia cells.

We examined the multidrug resistant P-glycoprotein (P-gp) on normal bone marrow (BM) cells and acute myeloid leukaemia (AMI) cells, using newly devised flow cytometric multi-parameter analysis with CD33, CD34 and MRK16 monoclonal antibodies. In both normal BM cells and AML cells, CD34+CD33- cells expressed P-gp strongly, CD34+CD33- cells moderately, and CD34-CD33+ cells weakly. Acute promyelocytic leukaemia, mainly expressing CD34-CD33+ but not CD34+CD33- at diagnosis, expressed less P-gp. P-gp expression of AML cells at diagnosis was increased as compared with normal cells of the same phenotype. P-gp expression was more increased in relapsed cases, especially in immature subpopulations.