CD34 and acute myeloid leukemia: To study the expression of P-glycoprotein (P-gp) and the reversal function of As2O3, the active ingredient of arsenic, on drug resistance in acute myeloid leukemia (AML) patients, P-gp and cluster of differentiation 34 (CD34) were examined in primary mononuclear and resistant cells, with or without As2O3.