Decitabine, a DNA methyltransferase inhibitor, reduces P-glycoprotein mRNA and protein expressions and increases drug sensitivity in drug-resistant MOLT4 and Jurkat cell lines.

Multidrug resistance (MDR) is a major clinical obstacle in the treatment of several cancers including hematological malignancies and solid tumors. The ATP-binding cassette transporter B1 (ABCB1) gene and its product, P-glycoprotein (P-gp), is one molecule that is involved in drug resistance. Here we report on the effect of decitabine (5-aza-2'-deoxycytidine), an inhibitor of DNA methyltransferase, on ABCB1 mRNA and P-gp expressions in drug-resistant MOLT4 and Jurkat cells. We found that decitabine treatment reduced ABCB1 mRNA and P-gp expressions in MOLT4/daunorubicin-resistant and Jurkat/doxorubicin-resistant cells. The decrease in the expression of ABCB1 mRNA and P-gp was accompanied by increased sensitivity to anticancer drugs in both drug-resistant cell lines. Our data suggest that DNA methylation is one of the mechanisms underlying ABCB1/P-gp overexpression in drug-resistant hematopoietic cell lines. The modulation of ABCB1/P-gp by DNA methylation inhibitors may be an effective strategy to overcome P-gp-related drug resistance.