| 5 Gastric cancer is one of the most malignant tumors,which has developed into a severe health problem.The gastric cancer is the second most frequently diagnosed cancer and the third leading cause of cancer death in China.80%-90% patients are detected at middle and later stage.The five-year survival rate for advanced gastric cancer patients is less than 10% due to the shortage of effective treatment method.The five-year survival rate for early gastric cancer(EGC)patients is beyond 90%.The reason for poor diagnosis and treatment is that current methods do not achieve the diagnosis of early gastric cancer.Endoscopy with biopsy is still the main method for confirming gastric cancer.But it is limited to identify early gastric cancer and it leads to the low diagnostic rate of early gastric cancer.Recently,some research suggest that narrow banding imaging(NBI)and endoscopy ultrasonography(EUS)are considered established means of diagnosis for EGC and depth.However,NBI and EUS are not widely used in the diagnosis of EGC.This means still has great limitations.The sensitivity of NBI diagnosis is only 60% which its high false positive rate,shorter wavelength and lighter penetration,and the result is influenced by histologic variety of EGC and inflammatory changes in the background mucosa.Although EUS achieves a diagnostic accuracy of over 80% and its tomographic views facilitate objective assessments,it is occasionally difficult to obtain images with adequate quality,and its evaluation is highly dependent on operators’ proficiency levels.Near-infrared endoscopic imaging is a new great potential method of diagnosis of early gastric cancer.Through intravenous injection of exogenous contrast medium,such as the ICG(Indocyanine green),it makes mucosal lesions highlight,and avoids the interference of background light.If specific target molecular is linked to the contrast medium,the specific imaging of the lesion can be presented.At present,the research in this aspect is very few.A few clinical research results show that the near-infrared endoscopic imaging has a larger value for differentiating between early gastric cancer and gastric adenoma,and its imaging characteristic is significantly correlated with the depth of cancer invasion.However,there is not a system research about the infrared imaging characteristics of gastric cancer and different precancerous status,and there is no infrared criteria of near-infrared endoscopic imaging assessment for diagnosis of gastric cancer.Therefore,we carry out the study about near-infrared endoscopic for diagnosing EGC and evaluating the invasion depth of the tumor,and the contrast agent was modified to connect with the targeted probe MG7 antibody,which was applied to the nude mouse model of subcutaneous tumor.Part 1 The clinical value of near-infrared endoscope to diagnose early gastric cancer and evaluate the invasive depth of tumorsObjective: Early gastric cancers and inflammatory lesions can be detected similarly by conventional endoscopy and be difficult to distinguish.The infrared light makes mucosal lesions highlight through intravenous injection of contrast medium and penetrates tissue more deeply than visible light.The purpose of this study is to discuss its feasibility and clinical value of near-infrared endoscopy to diagnose early gastric cancer and evaluate the invasive depth of tumors.Methods: This study included 40 patients,20 patients with early gastric cancers,willing to receive endoscopic submucosal dissection(ESD),20 patients with some general symptoms of dyspepsia epigastric pain who need to be examined by endoscopy.Each patient preparation was similar with the conventional endoscopy.First use standard white light to observe the lesion,and then inject the indocyanine green(ICG).2 minutes after injection,switch to near-infrared light to observe,record the image data,then accomplish the examination and record image data.Based on the results of near-infrared endoscopy,physicians discuss and establish classification criteria according to the observations(contrast,shape,color,etc.).We calculated the diagnostic sensitivity,specificity,accuracy and Spearman’s correlation coefficient between the staining intensity of near-infrared endoscope and the invasive depth of cancers.Specimens were obtained and immunohistochemical study was performed to explore the reason of staining.Specimens were obtained from ESD or biopsy and used to perform immunohistochemical staining for exploring the relationship between microvessel density(MVD)and tumor staining under near-infrared endoscope.Result: A total of 40 patients(including 20 patients with early gastric cancer and 20 with non-cancer)were recruited.They underwent near-infrared endoscopy after intravenous injection of indocyanine green.Observing by near-infrared endoscope,16 of early gastric cancer patients showed different degrees of tumor staining,while 14 of non-cancers were not stained.The sensitivity was 80.0%,the specificity was 70% and the overall accuracy was 75%.The Spearman’s correlation coefficient between staining intensity of the near-infrared endoscopic findings and the invasive depth of cancers was 0.583,meaning they were moderately correlated.Immunohistochemical study showed that positive staining was closely related to MVD.Conclusion: It has a certain significance that new near-infrared endoscope is used to diagnose early gastric cancer and evaluate the invasive depth of tumors.It is worth further large sample clinical study.Near infrared imaging may be related to the increase of MVD in the lesion.Part 2 The basic research of near-infrared endoscopic molecular imaging in the diagnosis of gastric cancer1.In vivo and in vitro studies of near-infrared endoscopic molecular imagingObjective: To explore the diagnosis of gastric cancer using the probe that MG7 antibody is linked to the contrast agent(ICG),which the near infrared endoscopy need to combine.Methods: ICG has a succinimidyl ester group,and can make a covalent bond with an amino group of the target protein MG7 antibody.We made the targeted molecular probe MG7-ICG.The absorbance was measured and its connection rate was calculated.Then through immunofluorescence study,to detect whether the combination between ICG and MG7 could affect its specificity or not.Finally,BGC-823 subcutaneous tumor model was established,while the diameter of subcutaneous tumor was 0.5-1cm,the nude mice were divided into three groups,respectively,the probe group,ICG group and blocking group.The probe,ICG was respectively injected via tail vein.And the mice of blocking group was injected with the probe 1 hours after the injection of MG7.The nude mice were monitored in real-time with small animal imaging.The mice were sacrificed after 72 hours,and the important organs were dissected and imaged.The data was collected for analysis.Results: The connection rate was 85%-92% by detecting the absorbance of the probe solution.At 6 hours after injection,the fluorescence signal was found in the liver of the nude mice.The fluorescence signal was observed in the subcutaneous tumor of the nude mice in the probe group at 24 hours and 72 hours,while the other two groups did not appear.There was a significant difference between the probe group and the other two groups(P <0.05).After 72 hours,the nude mice were sacrificed and the organs were taken out and the fluorescence signal was calculated.The ratio of tumor to liver or kidney was significantly different from that of the other groups(P <0.05).Conclusion: The molecular probe MG7-ICG has been successfully prepared and has good tumor targeting,which can make tumor-specific imaging and has great application value.2.The molecular target study of near-infrared molecular imagingObjective: To investigate the clinical value of near-infrared endoscopy combined with molecular imaging in the diagnosis of early gastric cancer.Methods: The histopathological samples of the patients were immunohistochemically stained with MG7 antibody,and the results were analyzed and to predict whether the sensitivity of the diagnosis of early cancer used with the probe.Results: There were 13 positive cases in the early cancer group and 6 cases in the control group.Among the four patients with negative stained with near-infrared endoscopy,the MG7 antibody was positive in them.It suggests that if the probe was used in clinical,it may be 20 cases of early gastric cancer screened out using ICG and the probe MG7-ICG.Conclusion: Immunohistochemical results suggest that MG7-ICG is useful in clinical,and it is very promising to improve the diagnosis rate of early gastric cancer. |
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