Multidrug resistance inhibition by antisense oligonucleotide against MDR1/mRNA in P-glycoprotein expressing leukemic cells

Introduction: Acute myeloblastic leukemia (AML) is the most common form of acute leukemia in adults. One major problem in this disease is the emergence of leukemic blast cells that are resistant to anticancer drugs. This phenomenon is termed multidrug resistance (MDR). One cause of MDR is the expression of the MDR1 gene and its product, P-glycoprotein (Pgp). Aim: In the present study, we tried to inhibit the MDR phenotype with MDR1/mRNA/Pgp in leukemic cells using different antisense sequences and two non-viral vectors. Materials and methods: The Pgp expressing cell line was established from a parental K562 (Erythroleukemia) cell line with increasing concentrations of doxorubicin, and named KDI/20. In order to reverse the MDR phenotype due to Pgp expression, four different sequences of sense, antisense and one random sequence with phosphorothioate (PTO) modification (PS-ODN) against MDR1/mRNA were synthesized. They were used on the KDI/20 cells in combination with two non-viral vectors: (1) Fugene 6 transfection reagent (cationic lipid) and (2) polyethylenimine (cationic polymer). The effect of PS-ODN was assessed at the cellular level by flow cytometry (for Pgp detection), and Rhodamine 123 assay (for functional assessment of Pgp) at the molecular level byRT-PCR(forMDR1/mRNA detection) and MTTassay in order to assess the sensitivity of cell to doxorubicin. Results: The results showed a decrease in the percentage of Pgp protein and MDR1/mRNA expression and an increase in the accumulation of Rh123 and drug sensitivity of cells to doxorubicin by antisense I and III. The reduction of MDR1/mRNA was more significant than its protein reduction. Therefore, our data showed that antisense can reverse the MDR phenotype at the transcription level and the PEI vector is more efficient than cationic lipid.