| Background Chemotherapy plays an important role in comprehensive therapy of gastric cancer. But the Multidrug Resistance (MDR)limits the application of chemotherapy drugs. It has important clinical significance for guiding rational chemotherapy to study the mechanisms of the incidence and impact of MDR. The mechanism of MDR is complicated, in which the activation and overexpression of Multidrug Resistance genes is considered to be the main reason for MDR.Lung resistance protein(LRP) and glucosylceramide synthase(GCS) are two common multidrug resistance genes,which can be found overexpressed in gastric cancer cell lines and are considered to be the major reason for multi-drug resistance of gastric cancer.Studies showed that LRP and GCS all imprence at higher level in gastric cancer tissuce,and COX-2 has Positive correlation with LRP\GCS impression level in gastric cancer tissuce. But the selective COX-2 inhibitors can increase the sensitivity of malignant tumors to chemotherapeutic drugs. The specific mechanism is still unknown, maybe concerned with COX-2 down regulate LRP,GCS impression level. Found this point we designed this study.Objective To observe the growth of gastric adenocarcinoma cell line and the expression of LRP,GCS in difference group of gastric adenocarcinoma cell lines with or without selective COX-2 inhibitor interference and to explore the mechanism of COX-2 invlove in multidrug resistance of gastric cance.The finding of this study may provide experimental and theoretical basis on reversing Multidrug Resistance of gastric cancer in clinic therapy with the use of COX-2 inhibitors . ?Methods Different concentration of selective COX-2 inhibitor celecoxib was used to intervene in the growth of gastric adenocarcinoma cell line (SGC7901/VCR), while control group gastric cancer cell line was cultured without any intervence. MTT method was used to observe the influence of the growth of gastric adenocarcinoma cell line (SGC7901/VCR); ELISA and immunohistochemical method were used to detect the expression of LRP, GCS in difference group of gastric cancer cell lines at some point time.variance analysis and t test method statistical method was used to analyze the influence of celecoxib on Multidrug Resistance in gastric cancer cell line.Results 1) The influence of celixiob to proliferation of gastric adenocarcinoma cell line (SGC7901/VCR) MTT method was used to measure different concentrations celecoxib intervence gastric cancer cells at 24, 48, 72h, livability of gastric adenocarcinoma cell line 12.5μmol/L celexiob intervenced were 98.7%,94.3%,91.2%; 25μmol/L were93.6%,86.4%,71.7%,50μmol/L were 88.5%,79.8%,58.3%,100μmol/L were 75.7%,53.2%,35.4%;200μmol/L were 42.3%,35.1%,17.2%. Prompting celecoxib inhibit the growth and enhance the apoptosis of gastric adenocarcinoma cell line SGC7901/VCR dependent of time and dose.2) ELISA Results LRP, GCS were all fined expressed in gastric cancer cell line SGC7901/VCR,The protein content of LRP, GCS was 87.84±5.85 ng / ml, 12.16±0.92ng/ml respectively. The protein content of LRP in four different group of gastric cancer cell lines treated with different doses of celecoxib decreased compared with control group, the content of LRP in very low dose group,low dose group,medium dose group ,high dose group( VLD, LD, MD, HD ) were 71.50±5.90 ng/ml,(t=18.891,P<0.01);53.54±3.79 ng/ml ,(t=8.973,P<0.01);38.90±4.20 ng/ml,(t=5.710, P<0.01);17.48±3.92 ng/ml,(t=4.234,P<0.01),respectively, the level of LRP in LD was lower than that of VLD (t = 14.246 , P <0.01), the level of LRP in MD was lower than that of LD or VLD (t = 12.899, P <0.01,t = 7.346, P <0.01 respectively). the level of LRP in HD was lower than that of MD,LD or VLD(t = 11.240, P <0.01,t = 6.759, P <0.01, t = 4.947, P <0.05 respectively). The protein content of GCS in four different group of gastric cancer cell lines treated with different doses of celecoxib decreased compared with control group, the content of LRP in very low dose group,low dose group,medium dose group ,high dose group( VLD, LD, MD, HD ) were 9.22±0.53g/ml,(t=17.148,P<0.01);7.86±0.55ng/ml ,(t=12.861,P<0.01);6.24±0.45 ng/ml,(t=8.945,P<0.01),3.27±0.33ng/ml,(t=5.968,P<0.01),respectively, the level of GCS in LD was lower than that of VLD (t=19.601,P<0.01), the level of LRP in MD was lower than that of LD or VLD (t=19.039,P<0.01, t=11.940,P<0.01 respectively). the level of GCS in HD was lower than that of MD,LD or VLD(t =12.651, P <0.01, t=8.945, P <0.01, t=7.039, P<0.01, respectively).Immunohistochemical results Image-pro plus soft ware was used to compare LRP Immunohistochemical OD of the experiment group with the comtrol group . Variance analysis was used to analyze OD of same time but different content celecoxib group.24h: F=182.83, P < 0.01; multiple comparison: P < 0.05. 48h: F=233.46, P < 0.01; multiple comparison: P<0.05. T test was used to analyze OD of same content celecoxib groups between 24h and 48h. VLD group:t=18.26,P<0.01; LD group:t=20.09,P<0.01;MD group:t=9.43, P<0.01;HD group: t=6.19, P<0.01. Similar image-pro plus soft ware was used to compare GCS Immunohistochemical OD of the experiment group with the comtrol group . Variance analysis was used to analyze OD of same time but different content celecoxib group.24h: F=90.57, P<0.01; multiple comparison: P<0.05. 48h: F=470.89, P<0.01; multiple comparison: P<0.05. T test was used to analyze OD of same content celecoxib groups between 24h and 48h. VLD group:t=15.22, P<0.01; LD group: t=20.09,P<0.01。MD group:t=17.13, P<0.01;HD group:t=10.65, P<0.01Conclusion 1) The selective COX-2 inhibitor celecoxib can inhibit the growth and enhance the apoptosis of gastric adenocarcinoma cell line SGC7901/VCR . 2) The selective COX-2 inhibitor celecoxib can reduce the expression of LRP, GCS in gastric cancer cell lines and comformed that COX-2-mediated multidrug resistance of gastric cancer is assosiated with influencing the expression of LRP, GCS.
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