| One of the major obstacles of the successful treatment of tumor and leukemia inclinic is the drug-resistance phenotype of cancer cells. So,one of the key points of the tumor treatment is how to successfully reverse the multidrug resistance (MDR). The major reason of producing refractory relapsing leukemia is MDR. P-glycoprotein(P-gp), MDR1 gene product acts the important role. The reversal of leukemia MDR is the urgent-settling problem today. At present, many drugs may reverse the MDR of tumor cells; but they couldn't settle the problem fundamentally. Their effect isn't ideal. The drugs have some toxic and side effects and local in the clinic application.Cyclosporin A, CsA, a kind of immunosuppressant, has been applied to the patients of plantation; and we found it may enhance the sensitivity of tumor cells to multidrug chemotherapy. CsA is the earlist studied to reverse drug-resistance, and is one of the best classical drugs in vitro experiments. At abroad, CsA had been used for II clinical trial; at home, Zhaochunting et al firstly used it to reverse leukemia in clinic. But because the reversal effect is dose dependent, the dose is relatively big, the toxic and side effects add and its value is expensive, the clinic application of CsA is limited. The new strategy of reversing MDR is the combination of the reversal agents in the view of the clinic. Tetramethylpyrazine,TMP, is one of active ingredients of traditional Chinese medicine, Ligusticum L.wallichii Franch., the biobase of amid and calcium channel blocker. TMP has been known as its successful treatment of reversal leukemia cell lines in vitro. Its effects are temperate and its toxic and side effects are low. This paper investigated the reversal effect of TMP combined with CsA on multidrug resistance in the human erythroleukemia multidrug resistant cells K562/MDR cells only having classical MDR phenotype acquired by gene transfer in order to obtain the reversal agents which possess clinical prospect.K562/MDR cells only showed the high-expressing of P-gp and classical MDRphenotype acquired by gene transfer. So, we used K562/MDR cells as the experimentalmodel to study the MDR reversing of leukemia cells. The DNA of K562/MDR cells andthe MDR1 gene of MCF-7/ADM cells were detected with reverse transcriptasepolymerase chain reaction (RT-PCR). The MDR1 gene of MDR-7/ADM was positive.The result was the same to that of the MCF-7/ADM cells. So the K562/MDR cells werecompetent for our experiment. The experimental result showed: the non-cytotoxic doseof TMP and CsA 320 u g/ml and 2.0 u g/ml and the low-cytotoxic were 1250 u g/ml and5.0 ug/ml; when 320 u g/ml TMP and 2.0 u g/ml CsA added along with ADM to theK562/MDR culture in vitro, the medium inhibited concentrations (IC50) were evidentlyreduced. The reversal folds were 5.2 and 9.6 as compared to its parental cells K562/S.When 320 ug/ml TMP in combination with 2.0ug/ml CsA was added along with ADMto the K562/MDR culture, the IC50 was reduced and the reversal folds were 15.6 higherthan that of the single application of 320 u g/ml TMP and 2.0 u g/ml CsA and that oftheir combination. When varient concentrations ADM were added to the K562/MDRculture, TMP and CsA could increase the intracellular accumulation of ADM. The effectTMP in combination with CsA was more evident. The two results compared with thecontrol of no-adding TMP or (and) CsA could add the intracellular chemotherapy drugsconcentration and reversed the MDR of K562/MDR cells to ADM.In addition, we also studied the reversal mechanism of TMP and CsA and offered evidence for studying P-gp blockers.The mechanism of MDR has been researching more and more deeply. And comparative perfect theory system had been established. After scholars studied classical MDR, they found that a obvious biochemistry character of drug-resistant tumor cells was the over expression of P-gp in cell membranes. The malignant tumor MDR of blood system still is the range of classical MDR. There are many kinds of fa... |
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