e Suppression of Multidrug Resistance in Leukemic Cells by Short Interfering RNA

Acute myeloblastic leukemia (AML) is the most common form of acute leukemia in adults. One of the major problems 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 the MDR is the expression of the MDR1 gene and its product, P-glycoprotein (Pgp). In this study, we tried to inhibit the MDR phenotype with MDR1/mRNA/Pgp in the leukemic cells using short interfering RNA (siRNA) and two nano particles as non-viral vectors. The Pgp expressing cell line was established from a parental K562 cell line with increasing concentration of doxorubicin and named KDI/20. In order to reverse the MDR phenotype due to pgp expression, siRNA against MDR1/mRNA was synthesized. siRNA was used on the KDI/20 cells in combination with two nano particles as non-viral vectors: (1) Fugene 6 transfection reagent (cationic lipid) and (2) polyethylenimine (cationic polymer). The effect of these complexes was assessed at the cellular level by flowcytometry (for Pgp detection) and molecular level by Real Time - PCR.The result showed 79% reduction in Pgp by siRNA /Fugene 6 and 86% reduction in the Pgp by siRNA/PEI at the cellular level in flowcytometry. Also 62% reduction in the MDR1/mRNA by siRNA /Fugene 6 and 74% reduction in the MDR1/mRNA by siRNA /PEI at the molecular level by Real Time – PCR. siRNA could be an efficient method in order to post transcriptional gene silencing and there were no significant differences between two nano particles in gene silencing in this study.