Knockdown of <Emphasis Type="Italic">MRP4</Emphasis> by lentivirus-mediated siRNA improves sensitivity to adriamycin in adriamycin-resistant acute myeloid leukemia cells

Chemotherapy remains the standard treatment for acute myeloid leukemia; however, the emergence of drug resistance is a major hurdle in the successful treatment of leukemia. The expression of multidrug resistance-associated protein 4 (MRP4) induces resistance in the adriamycin-resistant acute myeloid leukemia cell line, K562/ADR. The aim of this study was to investigate whether knockdown of MRP4 by lentivirus-mediated siRNA could improve the sensitivity of K562/ADR cells to adriamycin. Five lentivirus-mediated short hairpin RNAs (lv-shRNAs-MRP4) were designed to trigger the gene silencing RNA interference (RNAi) pathway. The efficiency of lentivirus-mediated siRNA infection into K562/ADR cells was determined using fluorescence microscopy to observe lentivirus-mediated GFP expression. MRP4 expression in infected K562/ADR cells was evaluated by real-time PCR and Western blot analysis. The MTS assay was used to measure cell viability and flow cytometry was used to measure apoptosis. The transfection efficiency of K562/ADR cells was over 80 percent. The gene silencing efficacy of lv-shRNA1-MRP4 was superior to the other constructs. Infection of K562/ADR cells with lv-shRNA1-MRP4 led to strong inhibition of MRP4 mRNA and protein expression. Combined treatment with lv-shRNA1-MRP4 and adriamycin decreased cell growth and increased apoptosis compared to treatment with lv-shRNA1-MRP4 or adriamycin alone. These data indicate that in K562/ADR cells MRP4 is involved in drug resistance mechanisms and that lentivirus-mediated knockdown of MRP4 may enhance sensitivity to adriamycin.