Objective To explore the cytotoxicity of 2-chlorodeoxyadenosine (2-CDA) to sensitive or multidrug-resistant (MDR) K562 leukemia cell line.Methods MTT assay was used to detect the cytotoxicity,the combined effect of two drugs was analyzed with Chou-Talalay combination index (CI).Flow cytometry was used to detect the P-glycoprotein (P-gp)on the surface of the cells and the intracellular daunorubicin (DNR).Results The IC 50 of 2-CDA to K562 and K562/A02 was (23.9±2.4)nmol/L and (137.6±12.7) nmol/L,resp...