Introduction: Gene therapy is a technique for correcting defective Genes responsible for disease development. Researchers may use one of several approaches for correcting faulty Genes. In one approach, the regulation (the degree to which a Gene is turned on or off) of a particular Gene could be altered. In Gene therapy approach, a carrier molecule called vector must be used to deliver the therapeutic Gene to the patients target cells. Currently, the most common vector used is a virus that has been Genetically altered to carry normal human DNA. Besides virus-mediated Gene-delivery, there are several nonviral options such as liposome and cationic polymer for Gene delivery. Aim: In the present study, we tried to inhibit multidrug resistant (MDR) phenotype with MDR1/mRNA/Pgp in leukemic cells by different antisense sequences and two nonviral delivery systems. MDR1 Gene is expressed in some normal tissues and cells, especially CD34+ hematopoietic cells. Therefore, the monitoring of this Gene is very important in protection of stem cells against chemotherapy in cancers.
Materials and Methods: The P-glycoprotein expressing cell line was established from parental K562 (erythroleukemia) cell line with increasing concentrations of doxorubicin and called KDI/20. In order to reverse the MDR phenotype due to P-glycoprotein expression, four different sequences of sense, antisense and one random sequence with phosphorothioate (PTO) modification (PS-ODN) against MDR1/mRNA were synthesized. They were treated on the KDI/20 cells in combination with two nonviral vectors: (1) FuGene 6 transfection reagent and (2) polyethylenimine (PEI). 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), and at the molecular level by RT-PCR (for MDR1/mRNA detection) and MTT assay (to assess the doxorubicin sensitivity of the cell).
Results: The results showed a decrease in the proportion of Pgp protein and MDR1/mRNA expression and an increase in the accumulation of Rh 123 and doxorubicin sensitivity of cells by antisense I and III. The reduction of MDR1 mRNA was more significant than its protein reduction. Therefore, the results showed that antisense can reverse MDR phenotype at transcription level and the PEI vector is more efficient than cationic lipid.