| Background Chemotherapy plays an important role in comprehensive therapy of gastric cancer. But the Multidrug Resistance (MDR)limits the further 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),glutathione S-transferase-π(GST-π) ,and glucosylceramide synthase(GCS) are three common multidrug resistance genes,which can be found overexpressed in gastric cancer tissues or gastric cancer cell lines and are considered to be the major reason for multi-drug resistance of gastric cancer.Studies showed that COX-2 involved in the occurrence of multidrug resistance, and the selective COX-2 inhibitors can increase the sensitivity of malignant tumors to chemotherapeutic drugs. The specific mechanism is still unknown. It has become the research focus in this field with COX-2 as a target to reverse multidrug resistanceObjective To study the expression of COX-2 and LRP,GCS, GST-πin gastric cancer tissues and to investigate the correlationship between the expression of COX-2 and that of LRP,GCS, GST-πin gastric carcinoma.To observe the expression of LRP,GCS, GST-πin difference group of gastric cancer 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 63 samples of gastric adenocarcinoma tissue and 30 samples of non-cancerous gastric tissue were collected from patients who were resected in Surgical Department of Anhui Provincial Hospital from June 2008 to October 2008, all these samples were confirmed to be correct diagnosis pathologically.All patients didn't receive any form of radiotherapy and chemotherapy before surgery.Immunohistochemical method were used to observe the expression of COX-2, LRP, GCS and GST-πand the correlationship between the expression of COX-2 and that of LRP, GCS, GST-πwas analyzed by statistical method.In addition, different concentration of selective COX-2 inhibitor celecoxib was used to intervene in the growth of gastric cancer cell line (SGC-7901), while control group gastric cancer cell line was cultured without any intervence. ELISA method was used to detect the expression of LRP, GCS, GST-πin difference group of gastric cancer cell lines and t test statistical method was used to analyze the influence of celecoxib on Multidrug Resistance in gastric cancer cell line.Results 1) Immunohistochemical results The expression of COX-2, LRP, GST-π, GCS in gastric canacer tissues was higher than that of non-gastric carcinoma, the positive expression rates were 87.3% vs36.7%,66.7% vs43.3%,63.5% vs 40.0%, 49.2% vs23.3% respectively(all P<0.05). The positive expression rate of COX-2 in gastric cancer tissues with lymph node metastasis was higher than that without lymph node metastasis (100% vs 69.2%, P<0.05).There is no significant difference in the possitive expression rate of COX-2 in different group of ages, gender, differentiation, depth of invasion in gastric tissues. There is also no significant difference in the possitive expression rate of LRP, GST-π, GCS in different group of ages, gender, differentiation, depth of invasion in gastric tissues,with or without lymph node metastasis.The correlation between the expression of COX-2 and that of LRP (r=0.337 ,P=0.007), GST-π(r=0.301,P=0.015), GCS (r=0.394,P=0.004) in gastric carcinoma was significant, whereas the correlation between the expression of LRP and GST-π(r=0.233,P=0.066), LRP and GCS (r=0.225,P= 0.077), GST-πand GCS (r=0.153,P=0.232) was not significant.2) ELISA Results LRP, GST-π, GCS were all fined expressed In gastric cancer cell line SGC-7901,The protein content of LRP, GST-π, GCS was 83.76±7.20 ng / ml, 41.46±1.85ng/ml, 11.56±0.76ng/ml respectively. The protein content of LRP in three different group of gastric cancer cell lines treated with different doses of celecoxib decreased compared with control group, the content of LRP in low dose group,medium dose group ,high dose group( LD, MD, HD ) was73.78±6.83 ng / ml(t = 2.465, P <0.05),56.95±3.62 ng / ml(t = 8.153, P <0.01),36.49±4.16 ng / ml(t=13.928, P <0.01) respectively, the level of LRP in MD was lower than that of LD (t = 5.330 , P <0.01), the level of LRP in HD was lower than that of MD or LD (t = 11.413, P <0.01,t = 9.080, P <0.01 respectively). The protein level of GST-πin three different group of gastric cancer cell lines treated with different doses of celecoxib decreased compared with control group, the content of GST-πin the LD, MD, HD group was 36.88±2.50 ng / ml( t = 3.610, P <0.01),30.61±1.98 ng / ml(t = 9.821, P <0.01) 22.35±2.96ng/ml(t=13.426,P <0.01 ) respectively, the level of GST-πin MD was lower than that of LD (t = 4.815, P <0.01), the level of GST-πin HD was lower than that of MD or LD (t = 9.188, P <0.01, t = 5.698, P <0.01 respectively). The protein level of GCS in three different group of gastric cancer cell lines treated with different doses of celecoxib decreased compared with control group, the content of GCS in the LD, MD, HD group was9.60±1.01ng/ml(t=3.804 P <0.01), 7.75±0.76ng/ml( t=8.709, P <0.01),6.33±0.87ng/ml(t = 11.11, P <0.01)respectively, the level of GCS inMD was lower than that of LD (t = 3.608, P <0.01), the level of GCS in HD was lower than that of MD or LD (t = 6.032, P <0.01, t = 3.187, P <0.05 respectively ).Conclusion 1)The positive expression rate of LRP,GCS, GST-πwas high in gastric cancer tissues and LRP,GCS, GST-πare the primary cause of multidrug resistant in gastric cancer independently. 2) There is significant correlationship between the expression of COX-2and that of LRP,GCS, GST-πin gastric cancer tissues.3) The selective COX-2 inhibitor celecoxib can reduce the expression of LRP, GCS, GST-πin gastric cancer cell lines and comformed that COX-2-mediated multidrug resistance of gastric cancer is assosiated with influencing the expression of LRP, GCS, GST-π. |
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