| Objective:Gastric cancer is the fourth most common cancer worldwidewith an estimated1million new cases each year, of which nearly70%occur indeveloping countries. In2007, there were about80million people died ofgastric cancer in the world. In China average annual mortality rate ofgastric cancer approximately is25.2/10million populations.5-fluorouracil(5-FU) is widely used in the chemotherapy of gastric cancer, which requirescontinuous intravenous infusion.The application of5-FU is not convenientenough.Although the embedded central venous catheter to solve this problem,but the embedded central venous catheter also increases the care andcosts.Raltitrexed is a quinazoline folate analogue for a novel water-solublethymidylate synthase (TS) inhibitors. Raltitrexed is mainly for treatment ofadvanced colorectal cancer. In the study of gastric cancer, clinical trials ofraltitrexed plus other cytotoxic drugs has shown to be effective, but yet to be alarge-scale clinical trials to confirm. Raltitrexed deserves further study in theapplication of gastric cancer.In this study, we established a model of thehuman gastric cancer(MGC-803) xenograft transplanted in nude mice thatwere given raltitrexed,5-fluorouracil (5-Fu), normal saline drugintervention,and explored the effects and mechanisms of raltitrexed on thegrowth of gastric cancer.Methods:1The models of the human gastric cancer(MGC-803)xenograft transplanted in nude mice were established.2Experimental groupand drug intervention:Twenty-four nude mice models of human gastriccancer xenograft (MGC-803) were randomly divided into raltitrexedgroup,5-Fu group and control group(each group, n=8). Mice wereadministered intraperitoneally by raltitrexed,5-Fu and normal saline (0.2ml permouse). The administered dose of raltitrexed and5-Fu group were 7.5mg/Kg/day,15mg/Kg/day respectively.The drug were administered dailyfor5days,followed by a2-day interval,then another5days of dailyadministration. The body weight, mental state, eating and stool of the nudemice were monitored closely.3Evaluation of tumor inhibiting effects:Tumorvolume was measured by vernier caliper every three days, calculatedaccording to the formula: Tumor volume(cm3)=A×B2/2, where A,B are themajor dimension, minor dimension. And then draw the curve according to thetumor volume. Two days after the last treatment,the mice were sacrificedand the tumors were immediately removed for further studies. Tumor weightwas measured and calculated the rate of tumor inhibition according to theformula: The rate of tumor inhibition=(tumor weight of control group-tumorweight of experimental group)/tumor weight of control group*100%.4Distribution and apoptosis of cell cycle of tumor cells were examined by FlowCytometry Assay.5P53mRNA and protein expression level were detected byRT-PCR and Western blot and compared changes between three groups.6Statistic analysis: The data were presented with mean and standard deviation,analyzed with One-way ANOVA with Statistic software of SPSS13.0edition,P<0.05was considered statistically significant.Results:1Body weight of nude mice bearing cancer:Body weights of nude micein raltitrexed,5-Fu,control group were19.60±1.78g,17.79±1.16g,21.75±2.13g,respectively. Body weights of nude mice in raltitrexed and5-Fu groupwere lower than that of the control group (P<0.01).Aslo body weight of nudemice in5-Fu group is lower than that of raltitrexed group(P<0.05).2Tumor volume of nude mice bearing cancer:Tumor volume of nudemice in raltitrexed,5-Fu, control group were657.89±59.47mm~3,706.14±64.42mm~3,1232.02±109.69mm~3,respectively.Tumor volume of nudemice in control group was higher than that of raltitrexed and5-Fugroup(P<0.01). But there was no significant difference between raltitrexed and5-Fu group(P>0.05).3Tumor weight and the rate of tumor inhibition of nude mice bearing cancer:Tumor weights of nude mice in raltitrexed,5-Fu, control group were0.78±0.06g,0.83±0.08g,1.53±0.13g,respectively. Tumor weights of nude micein raltitrexed and5-Fu group were lower than that of the control (P<0.01).Butthere was no significant difference between raltitrexed and5-Fugroup(P>0.05).The rate of tumor inhibition in raltitrexed and5-Fu group were49.02%,45.75%,respectively.4Distribution of cell cycle and apoptosis of tumor cells:For the G0/G1stage,the number of cells decreased in raltitrexed and5-Fu group,there wassignificant difference comparing to the control group (P<0.01). For the Sstage,the number of cells increased in raltitrexed and5-Fu group, there wassignificant difference comparing to the control group (P<0.01).But there wasno significant difference between raltitrexed and5-Fu group for the G0/G1andS stage (P>0.05).Aslo, there was no significant difference for the G2/S stagein three groups(P>0.05).Compared the control group,the apoptotic rate ofraltitrexed and5-Fu group were higher than that of the controlgroup(P<0.01).Aslo the apoptotic rate of raltitrexed group was higher thanthat of5-Fu group(P<0.05).5P53mRNA relative expression in raltitrexed and5-Fu group was0.521±0.046,0.487±0.041respectively, while in the control group was0.159±0.025. P53protein relative expression in raltitrexed and5-Fu group was0.509±0.049,0.474±0.034,respectively,while in the control group was0.193±0.021.Compared with the control group,p53mRNA and proteinexpressions in raltitrexed and5-Fu group were significantly higer (P <0.01).But there was no significant difference between raltitrexed and5-Fugroup(P>0.05).Conclusion:1Raltitrexed can inhibit the growth of the human gastriccancer(MGC-803) xenograft transplanted in nude mice. And raltitrexed hasthe same inhibitory effects with5-Fu.2Raltitrexed can induce S-phase block of the cell cycle in human gastriccancer cell MGC-803xenografts in nude mice,then inhibit MGC-803cells proliferation.3Raltitrexed can induce cells apoptosis in human gastric cancer cellMGC-803xenografts in nude mice.4Raltitrexed may play an anti-tumor effect by up-regulating p53mRNAand protein expression levels. |
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