| Objective: multidrug resistance (MDR) means that tumor cells produce the resistance to multiple chemotherapy agents, which is the major cause of failure of chemotherapy. The mechanism of MDR are complex and variable. One kind of drug resistance cell may concern several mechanism of MDR, leading to unsatisfying effect with single reversal agent. If two reversal agents, especially two kind of Chinese medicine, combined together aiming at different mechanism , better chemotherapy effect maybe can obtained with less toxicity. It has been identified that both As2O3 and matrine have reversal effect on tumor cells. But the research about combination of As2O3 and matrine to reverse MDR of tumor cells has not been reported at present. This study was planned to observe the reversal effect of combination of AS2O3 and matrine on K562/ADM cells, a adriamycin-resistant cell line of human leukemia. The relationship between their reversal effect with changes of cellular drug efflux mediated by P-gp and changes of GST- π related to drug detoxification was also studied, aiming to find effective strategy and its theoretical basis for reversing MDR in clinic.Methods: The major group were divided as fllows: (1).K562/S cell line. (2). K562/ADM cell line. (3). K562/ADM cell line with As2O3.(4). K562/ADM cell line with matrine.(5). K562/ADM cell line with As2O3 and matrine . Cell toxicity and reversal times of As2O3 and/or matrine on tumor cells were determined by MTT assay. Intracellular drug concentration and cell apoptosis percentage were determined by spectrophotofluorometry and flow cytometry respectively. The above-mentioned index were used to value the reversal effect of As2Oj and matrine along with ADM on K562/ADM singlely or combined used. In order to discuss the mechanism of reversal effect of As2O3 and matrine, the following index were measured: P-gp coded by mdr-1 gene and GST- n expression were observed via immunohistochemical technique andsemi-quantified by computer image analysis system; changes of P-gp were determined by flow cytometry and changes of GSTs enzymic activity by biochemical method.Results: 1. As2O3 or matrine could obviously inhibit the growth of K562/S and K562/ADM, its' IC50 had not statistical difference (P>0.05).Non-cytotoxic dosage and low-cytotoxic dosage of As2O3 and matrine were determined by MTT assay .Non-cytotoxic dosage was selected as reversal dosage. 2.Used along with ADM, IC50 of both K562/ADM with As2O3 and K562/ADM with matrine were lower than that of K562/ADM(P < 0.01),but still higher than that of K562/ADM with As2O3 and martrine(P<0.01). Two agents combined together, the reversal effect was better than that of the sum of As2O3 or matrine singely. Intracellular ADM concentration and cell apoptosis percentage of K562/ADM with As2O3 or matrine was higher than that of K562/ADM (P<0.05,P<0.01,respectively), but still lower than that of K562/ADM with As2O3 and matrine(P<0.01,P<0.05,respectively) S.Immunohistochemical results showed that P-gp and GST- n overexpress in K562/ADM.GSTs enzymic activity were enhanced.at the same time.4.Compared with K562/ADM,intracellular GST- n content and GSTs enzymic activity were lower in K562/ADM with As2O3 (P<0.01). No significant changes were found in K562/ADM with matrine.( P>0.05).5. P-gp expression in K562/ADM with matrine was lower than that of K562/ADM(P< 0.01),but still higher than that of K562/ADM with As2O3 and matrine(P<0.01). There was no significant changes of P-gp expression in K562/ADM with As2O3 compared with K562/ADM(P>0.05).Conclusions: 1. As2O3 and matrine were effective antitumor drugs with obvious inhibiting effect on tumor cells. K562/ADM had no drug resistance to As2O3 and matrine.2.Non cytotoxic dosage of As2O3 and matrine could partly reverse the MDR of K562/ADM. The effect of combination of two agents were superior to that of single uses due to their coordinate effect.3.Overexpression of P-gp and GST- π and enhanced enzymic activity of GSTs were related to mechanism of MDRAThe reversal mechanisms of As2O3 and mat...
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