Ktrans For Anti-angiogenic Effects Evaluation In Nude Mice With Orthotopic Transplantation Tumor Model Of Gastric Cancer

Gastric carcinoma, a common malignant tumor worldwide, has a poor prognosis. It is suggested that tumor-mediated angiogenesis due to high levels of angiogenic stimulators and down-regulation of endogenous angiogenic inhibitors play a basic role in the pathogenesis of gastric cancer. Angiogenesis refers to the formation of new capillaries from existing blood vessels and is an essential component of normal physiological as well as pathological processes. Microvessel density(MVD) is an effective index to evaluate the angiogenic activity, growth and progression of gastric cancer. Previous gastric cancer studies have shown that angiogenesis plays an important role in gastric cancer development and prognosis, and given the biological behavior of gastric cancer, differentiation degree and lymph node metastasis are closely related. However, MVD require specimens by invasive methods, and it does not reflect the functional status of the tumor dynamicly and repeatedly.Dynamic contrast enhanced magnetic resonance imaging(DCE-MRI), a robust imaging method, is commonly used non-invasively to characterize changes in tumor vascularity and to assess the therapeutic effect of anticancer strategies. T1 weighted DCE-MRI has been proposed as a non-invasive method to assess the permeability of the tumor vessel, which can be measured using quantitative parameters. Physiologically, Ktrans is the most important and significant tissue dependent parameter which can be assessed either in flow-limited or permeability-limited condition. In complex situations, it indicates the flow and permeability properties of tissue.The aim of our study was to assess the feasibility and mechanism of Ktrans from DCE-MRI in nude mice with orthotopic gastric cancer model.The research contents and results are as follows: Part I Establishment of orthotopic transplantation model of gastric cancer in nude mice and the feasibility study of DCE-MRI.Objective: To establish the orthotopic transplantation model of gastric cancer in nude mice and to study the feasibility of DCE-MRI application in the nude mice model of gastric cancer.Methods: Human gastric cancer SGC7901 was implanted subcutaneously into nude mice, to establish the orthotopic transplantation model of gastric cancer in nude mice after passage. DCE-MRI was performed using gadopentetate as contrast agents. Subsequently, the tumor was dissected from the adjacent tissues in order to detect the MVD. MVD were compared inorthotopic transplantation tumor model of gastric cancer and normal gastric mucosa.Results:Fifteen nude mice with orthotopic transplantation model of gastric cancer successfully underwent DCE-MRI examination. In terms of those mice in our study, the values of Ktrans, kep and Ve were 2.11±0.44 min-1,4.59±0.93 min-1,and 0.46±0.06, respectively. MVD in gastric cancer tissues was significantly higher than that in normal gastric mucosa(χ2=16.205,P<0.001;χ 2=13.575,P<0.001).Conclusion:1.DCE-MRI can be used for noninvasive quantitative evaluation of vascular parameters of gastric carcinoma;2.MVD showed a significant difference in the orthotopic transplantation model of gastric cancer in nude mice, as compared with normal gastric mucosa. Part II Ktrans value from DCE-MRI for anti-angiogenic effects evaluation in nude mice with orthotopic transplantation model of gastric cancerObjective: The aim of this study was to assess the feasibility and value of DCE-MRI in the evaluation of anti-angiogenic effects in nude mice with orthotopic transplantation tumor model of gastric cancer.Methods: Apatinib mesylate, a small molecule tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor-2, was used in this study. Nude mice with orthotopic transplantation model of gastric cancer were randomly assigned to one of the following two groups: the treatment group, in which mice were given apatinib intragastrically for 18 days(n=15;100mg/kg, dissolved in 0.1mldd H2O2),and the control group, in which mice were given the same doses of dd H2O2 in the same manner. After 18 days, DCE-MRI was performed, and the tumor was dissected from the adjacent tissues in order to detect the MVD and VEGF expression levels by immunohistochemistry. MVD and VEGF expression were compared in both treatment group and the control group.Results: The Ktrans of tumors in nude mice treated with apatinib for 18 days was significantly lower than that of control groups(0.62±0.05min-1 VS 1.66±0.23 min-1, t=17.05, P < 0.001).In the meantime, MVD and VEGF expressions of treatment group were much lower than those of control groups.(χ2=4.302,P=0.038;χ2=8.688,P=0.003).Conclusion: DCE-MRI could be utilized toassess the effects of apatinib on nude mice with orthotopic transplantation model of gastric cancer. The influencing factors on the value of ktrans include MVD and VEGF, the latter of which is more important. Part III Research and discussion the influencing of VEGF on Ktrans value of DCE-MRI quantitative parametersObjective: To anaylze the potential effect VEGF on Ktrans value, one of DCE-MRI quantitative parameters, in nude mice with orthotopic transplantation model of gastric cancer..Methods: We established the orthotopic transplantation model of gastric cancer in nude mice. Three weeks after that, tissue specimens were obtained from nude mice with tumor. The expressions of VEGF, EGFR and SET8 in tissues and their correlations were analyzed by immunohistochemistry..Results: In the orthotopic implantation models of gastric cancer in nude mice, the expression level of VEGF was associated the high expressions of SET8(χ2=5.104,P=0.024)and EGFR(χ2=4.538,P=0.033). In addition, the expression level of EGFR was associated with SET8 expression(χ2=5.104,P=0.024).Conclusion: SET8 may have a regulatory effect on VEGF.