In Vitro Study of the Effect of Cyclosporine A, Tetrandrine and Their Combination on the Reversion of Multidrug Resistance in Leukemia Cell Line.

Objective: The aim of this study was to investigate the mechanism to reverse the drug resistance of leukemia cells in Cyclosporine A(CsA), tetrandrine (Tet) alone or their combination by using empirical methods, and to provide the basic evidence for further study, and lay the theoretical basis for the clinical applications.

Method: By MTT assay, the IC50(the concentration causing 50% inhibitor of cell growth) of DNR was determined;By flow cytomet ry (FCM) assay, the intracellular DNR concentration and the expression of P-glyco-protein (P-gp) were examined, and the apoptotic changes were observed by Anexin-V. By fluorescent semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), the mRNA expression of multidrug resistance (MDR) was measured.

Results:

1. The IC50 of DNR for K562 and K562/A02 cells were 0.26mg/l and 21.22mg/l respectively. Treating K562/A02 cells with CsA(1mg/L), TTD(0.1mg/L)and both for 48 hours partially restored the sensitivity of K562/A02 cells to DNR(IC50 were 7.83 mg/L,5.32 mg/L,2.33 mg/L respectively.) but had not effect on K562 cells;

2. K562/A02 cells showed apoptotic characteristics after treated with CsA, and both for 48 hours(Apoptosis rate was 10.27%,17.64%,52.79% respectively);

3. The fluorescence intensity of intracellelar DNR in K562 and K562/A02 cells treated with DNR(1mg/L)was 522,173 respectively. CsA and TTD (alone or combination) elevated the intracellular DNR concentration in K562/A02 cells(the fluorescence intensity of intracellelar DNR in K562/A02 cells was 188,339,515 respectively);

4. The fluorescence intensity of P-gp in K562 and K562/A02 cells was 0.5,97.97. The P-gp expression was down after treated with CsA, TTD and both(73.7,65.05,58.1);

5. mdr1 mRNA was also down regulated, and the effect of their combination was greater. Date was analyzed by SPSS 13.0 software and expressed as mean ± SD.

Conclusions:

1. High expression of P-gp may be involved in the mechanism of multidrug resistance (MDR) of K562/A02 cells line;

2. MDR can be partially reversed by CsA or TTD, of which the combination shows a great synergistic reversal effect.