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Background and Aim: Multidrug resistance (MDR) compromises the efficacy of chemotherapy. Many approaches have been used to reduce MDR; however, the results are poor. It has been reported that iron deprivation downregulates MDR genes. To investigate the relationship of iron with MDR and early growth response gene-1 (EGR1), we investigated the effect of iron deprivation on expression and/or function of multidrug resistance-1 (MDR1), early growth response gene-1 (EGR1), ferritin heavy chain gene (H-Fn) and MDR1-encoded P-glycoprotein (P-gp) in the K562 leukemic cell line. Methods: The cells were stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA) and incubated with either FeCl3 or the iron-chelating drug DFO. The mRNA levels of MDR1, EGR1 and H-Fn were detected by RT-PCR. The protein expression and function of P-gp were measured by immunohistochemical staining and flow cytometry, respectively. Results: DFO significantly reduced the intracellular iron level, and led to ∼70% reduction of MDR1 mRNA, ∼50% of reduction of H-Fn mRNA and ∼30% reduction of P-gp protein in TPA-differentiated K562 cells. The P-gp pump function, measured by daunorubicin exclusion, was also reduced by DFO treatment. Conclusions: These results suggest a close relationship between iron deprivation and reduced MDR1/P-gp expression and function. DFO may be used together with chemotherapeutic drugs to achieve better clinical efficacy. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]