Study On Diagnostic Value Of Narrow-band Imaging Enhanced Magnifying Endoscopy For Early Gastric Cancer And The LncRNA Profiling And Function In Early Gastric Cancer

Gastric cancer is a common malignancy of digestive system, which is the second leading cause of cancer related mortality. Gastric cancer causes approximately 300,000 death each year in China. The 5-year survival rate could be largely improved for patients who are diagnosed at en early stage and treated properly. However, the gastric leision of patients with early stage disease is so small that the diagnostic rate of routine gastric endoscopy is relatively low. Recent years, the rapid development and use of narrow-band imaging and magnifying endoscopy have greatly improved the detection rate. Moreover, it is of great importance to identify novel biomarker for early gastric cancer and to further explore the carcinogenesis of early gastric cancer. Recent research reveal that Long non-coding RNA play an vital role in the development of tumor, which makes it a promising biomarker and target for the diagnosis and treatment of cancer. In general, this dissertation is consisted of two parts:the first one is the study on diagnostic value of narrow-band imagning enhanced magnifying endoscopy for early gastric cancer, and the second part is the LncRNA profiling and function in early gastric cancer.Part one:Study on diagnostic value of narrow-band imaging enhanced magnifying endoscopy for early gastric cancerObjective:To evaluate the diagnostic effectiveness of white light endoscopy, magnifying endoscopy, and magnifying narrow-band imaging endoscopy in detecting early gastric cancers.Methods:From March 2010 to June 2012, a total of 3616 patients received screening for gastric cancers by magnifying endoscopy. There were 3675 focal gastric lesions detected using conventional white light endoscopy (WLE) in four different referential hospitals that were recruited for further investigation using magnifying endoscopy (ME) and magnifying narrow-band imaging endoscopy (ME-NBI). The diagnosis of cancerous and non-cancerous lesions was conducted by evaluating the microvascular and microsurface patterns using the VS classification system. The final endoscopic diagnosis of each lesion was determined by consultation when a disagreement occurred. We used histopathological results as the gold standard for the diagnosis of EGC.Results:Among the 3675 lesions found there were 1508 chronic gastritis lesions,1279 chronic gastritis with intestinal metaplasia,631 low-grade neoplasias and 257 early gastric cancers validated by pathological findings. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of HD-WLE for the diagnosis of EGC were 71.2%,99.1%,85.5%,97.9%and 97.1%, respectively. The results of ME for diagnosing EGC were 81.3%,98.8%,83.3%,98.6% and 97.6%, respectively. The results of ME-NBI for the diagnosis of early gastric cancers were 87.2%,98.6%,82.1%, 99.0% and 97.8%, respectively. The diagnostic sensitivity and accuracy of paired ME and ME-NBI were significantly better than WLE (P<0.05).Conclusion:HD-WLE has a relatively high accuracy for diagnosing EGC and is an effective screening tool. Further investigations of ME and ME-NBI are required to achieve superior accuracy.Part two:LncRNA expression profile and function in early gastric cancerObjective:By analyzing the expression profile in patients diagnosed with early gastric cancer, this study aims at investigating the key LncRNAs in the early process of gastric carcinogenesis, and further exploring the biological function of these LncRNAs.Methods:Gene expression profiling was performed on the lesion tissue and paired chronic non-atrophic gastritis tissue samples of 6 patients diagnosed with early gastric cancer (EGC) using Agilent 8 X 60k Whole Human Genome microarrays. A GO (gene ontology) enrichment analysis was performed to explore the molecular functional correlation among these tissues. The differentially expressed LncRNAs, LOC389332, LOC400043 and LINC00982, together with LncRNA UCA1 were validated using a quantitative reverse-transcription polymerase chain reaction (qRT-PCR) assay in another group of independent tissue samples, including 28 low grade intraepithelial neoplasia (LGIN),30 high grade intraepithelial neoplasia (HGIN),18 EGC,19 advanced gastric cancer (AGC),30 gastritis, and cell line samples, including 2 gastric cancer cell lines and a human normal gastric epithelium cell line. To further explore the biological function of the elevated expressed LncRNAs LOC389332 and UCA1, RNA interference (RNAi) approach was used. The effect of LOC389332 and UCA1 on proliferation and migration was evaluated by CCK-8 and wound healing assay, respectively. We also investigated the gene expression profile on the LOC389332 knock-down cell line model and the UCA1 knock-down cell line model using Agilent 8 X 60k Whole Human Genome microarrays.Results:The gene expression profiling showed that 577 mRNA genes and 72 LncRNA genes were significantly differently expressed between EGC and gastritis. The GO enrichment analysis demonstrated that the differently expressed mRNA genes were mainly in the category of membrane function process, signal transmission process and cell adhesion process. Comparing with gastritis, LOC389332 was significantly up-regulated in EGC (P=0.0183), and LOC400043, LINC00982 significantly down-regulated (P value of 0.0489 and 0.0051, respectively). To validate the discovery of microarrays, qRT-PCR was performed. The result showed that in comparison with gastritis, the expression of LOC389332, UCA1 was markedly increased in LGIN, HGIN, EGC, AGC (P<0.001), and LOC400043, LINC00982 markedly decreased (P<0.001). Similarly, LOC389332 and UCA1 were also over-expressed in gastric cancer cell lines of HGC-27 and AGS. Furthermore, knock-down of LOC389332 and UCA1 expression by siRNA could inhibit cell proliferation and migration in vitro, which indicated that LOC389332 and UCA1 maybe potential oncogenes. According to the gene expression profiling analysis of LOC389332 and UCA1 knock-down cell line model, we found that comparing with negative control, there were 393 and 423 differentially expressed mRNA genes. The GO enrichment analysis indicated that the down-regulated genes were mainly in the category of cell membrane function process, signal transmission process and cell adhesion process. However, the up-regulated genes showed no GO terms.Conclusion:The LncRNA expression profile between EGC and gastritis was significantly different. LOC389332 and UCA1 were potential non-coding oncogenes in gastric cancer, the knock-down of which could inhibit cell proliferation and migration in vitro. LOC389332 and UCA1 may perform their function through altering cell membrane function, signal transmission and cell adhesion. But their detailed functional mechanisms need further exploration.