| Multidrug resistance(MDR) describes the phenomenon that tumor cells exposed to one antitumor agent become resistant to other chemically and structurally diverse chemotherapeutic agents,including intrinsic resistance and acquire resistance. Resistance of cancer cells to antitumor agents is a major problem in chemotherapy,particularly in solid tumors.The response rate of gastric tumors to chemotherapy is only 20%~50%, suggesting that the intrinsic drug resistance exist in the tumor cells.Since the early 1980s,many agents that can reverse MDR have been found investigated extensively,the abilities that these agents reverse the MDR of tumor are weak,there are toxic at high doses,restricting clinical application.So,there is more important significance to find low poison and highly efficient reversal agents.Arsenic trioxide(As2O3)is mainly applicated in acute promyelocytic leukemia (APL),it,s function is Induction of partial differentiation to APL cell or induction of apoptosis;at same time the inhibition of P-gp expression implicates that arsenic trioxide may play a important role in combating multidrug resistance.The resistance of K562/ADR reversed by Arsenic trioxide in recent research showed that As2O3 can increase the sensitivity of k562/ADM cells to adriamycin.This study initially explores the reversal effect and possible mechanism for As2O3 reversing the resistance of human gastric cancer cell line SGC7901/ADR to ADM,which will provide theoretical basis for clinical application.Methods:3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide (MTT) method is used to detect the uncytotoxicity concentrations of As2O3 to sensitive cell line SGC7901 and multidrug resistance cell line SGC7901/ADR,disposing cells with the As2O3 of uncytotoxicity concentrations and different concentration adriamycin,detecting 50% cell inhibitory concentration(IC50) by the method of MTT,analyzing arsenic trioxide to the impact of IC50 of two cells to adriamycin.the impact of fluorescene density in the cells by arsenic trioxide is detected with flow cytometry(FCM),P-gp function detected by the Rhodamine123 of P-gp specific substrate; the impact of arsenic trioxide to the expression of P-gp,GST-π and TopoⅡ determined by immune tissue chemical methods.Results:The IC50 of SGC7901 cells to adriamycin is 0.095mg/L, the IC50 of SGC7901/ADM cells is 5.861 mg/L and is 61.69 times of sensitive cell SGC7901;the fluorescene density in SGC7901 cells is 11.63,that in SGC7901/ADM cells is 6.06 and reduces 0.92 time(P<0.05). The positive expression rates of P-gp,GST-πin SGC7901 cells are 29.6% and 31.6% respectively;that in SGC7901/ADR cells are 47.8% and 46.4% respectively,evidently high than SGC7901 cells(P<0.01);The positive expression rate of TopoⅡ in SGC7901/ADR cells is 16.4%,and is low to SGC7901 cells(P<0.01). The uncytotoxicity concentrations of As2O3 to 95% and 90% cells are 0.4μmol/L and 0.8μmol/L respectively, When disposing resistant cells with 0.4μmol/L,0.8μmol/L AS2O3 and ADM at the same time,the IC50 of SGC7901/ADR are 3.711mg/l and 2.773mg/l respectively, reveral fold(RF) is 1.58 and 2.11 times respectively,evidently reveral role(P<0.01)at the concentration of 0.8μmol/L AS2O3. After disposed with 0.4μmol/L and 0.8μmol/L AS2O3, the fluorescene density in SGC7901/ADR cells is 7.19 and 8.78 respectively,increasing 0.19 and 0.45 time respectively,the fluorescene density of ADM in the cells evidently increasing at 0.8μmol/L. When disposing with 0.8μmol/L AS2O3 and Rhodamine123 at the same time,the fluorescene density in the SGC7901/ADR cells is added to 503.48 from 48.21,increasing 9.44 times(P<0.01). After disposed with AS2O3,the positive expression rate of P-gp in SGC7901/ADR cells evidently reduces to 36.2%(P<0.01),the positive expression rate of GST-π evidently reducing to 39.6%(P<0.05),the positive expression rate of TopoⅡadding to 20.0%, evident difference not existing(P>0.05).Conclusion:SGC7901/ADR cell line is resistant cell line,it,P-gp high expression results in agent inside cells flowing... |
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