| ObjectiveGastric cancer is one of the most common malignant tumors worldwide.In our country,the mortality of gastric cancer among cancer-related death occupied the second place.With the developments of endoscopic detection and multimodal therapies,the overall survival of gastric cancer has been prolonged.Unfortunately,the outcome of advanced gastric cancer patients remains unsatisfied.Therefore,it is crucial to improve the accuracy of diagnosis,to explore the target of therapy and a novel prognostic marker for patients with gastric cancer,especially for advanced gastric cancer patients.COP9 signalosome(CSN),an evolutionarily conserved multiprotein complex,was first described as a repressor of plant photomorphogenesis from Arabidopsis mutants.In mammals,CSN consists of eight subunits(CSN1 to CSN8)and has been shown to be implicated in the degradation of ubiquitin-mediated proteins,due to the sequence homology with the lid complex(19S)of the 26S proteasome.Studies focused on CSN6 demonstrated that it was involved in a wide variety of biological functions,such as embryonic development,cell cycle control and signal transduction.Recently,through their function to mediate the ubiquitylation and proteolysis,the role of CSN6 in carcinogenesis and cancer progression has been emerging.More evidence determined that the expression of CSN6 were increased in several human cancers,including breast cancer,ovarian cancer and colon cancer.In addition,the expression of CSN6 may be used as an independent prognostic marker in colon cancer.However,the functions of CSN6 in gastric cancer haven't been studied.As a result,it is urgent for us to explore their expression of CSN6 in gastric cancer,to detect the relationship between this gene and clinical characteristic,to analyze the prognostic value for gastric cancer patients.A definitely understanding of CSN6 may be helpful to improve the diagnosis and therapy for gastric cancer patients.Methods1.The genomic alternation of CSN6 was performed using cBioportal tool,which is based on TCGA database(Provisional database and Nature 2014 database).2.The differential protein expression of CSN6 in one immortalized gastric epithelial cell line and several gastric cancer cell lines were determined using Western blot analysis.3.The differential mRNA expression of CSN6 in gastric cancer tissues and gastric mucosa were detected according to Oncomine database.4.An immunohistochemistry staining was used to detect the CSN6 protein expression in 90 cases of gastric cancer tissues and corresponding adjacent normal tissues.The relationship between CSN6 and clinical characteristics was also explored.Furthermore,the correlation between different CSN6 expression status and overall survival time of gastric cancer patients was determined using Kaplan-Meier survival analysis.Cox proportional hazards regression model and receiver operating characteristic(ROC)analysis were used to evaluate the clinical significance of CSN6.5.The association between CSN6 and prognosis of 876 gastric cancer patients were demonstrated by Kaplan-Meier plotter,which was an online survival analysis software.It confirmed our findings,which indicated good reproducibility of CSN6 signature in predicting overall survival time of GC.Results1,Provisional database from TCGA revealed that CSN6 got 44.8 percentage(176/393)of gain and amplification alteration in 393 gastric cancer patients.Nature 2014 database from TCGA revealed that CSN6 got 42.8 percentage(123/287)of gain and amplification alteration in 287 gastric cancer patients.2.The results of Western blot analysis showed that the protein level expression of CSN6 in several gastric cancer cell lines was significantly higher than an immortalized normal gastric epithelial cell line(P<0.05).3.The results based on Oncomine database revealed that the expression of CSN6 at mRNA levels in both intestinal type and diffuse type were significantly higher than in gastric mucosa(P<0.05).4.The results of immunohistochemistry staining determined that the positive expression of CSN6 in gastric cancer tissues(62.2%,56/90)were significantly higher compared with corresponding adjacent normal tissues(41.4%,7/90)(P<0.05).Moreover,there was statistically positive relationship between CSN6 expression and tumor size of gastric cancer.No significant correlation was determined between the expression of CSN6 and other clinical characteristics,such as,age,sex,histological type,and AJCC TNM stage.6.The results based on Kaplan-Meier plotter detected that there were significant relationship between the prognosis of 876 gastric cancer patients and CSN5,CSN6 expression.The patients with high expression of CSN5 will prolong the overall survival time of gastric patients(P<0.001).The patients with high expression of CSN6 will shorten the overall survival time of gastric patients(P<0.001).5.Based on the results of immunohistochemistry staining,the overall survival time of gastric cancer patients with high CSN6 expression was significantly shorter than that with low CSN6 expression using Kaplan-Meier analysis.Negative association between the level of CSN6 expression and the outcome of patients with gastric cancer were observed using univariate and multivariate Cox model.We conducted ROC curve to evaluate the prognostic value of CSN6 expression and the area under the curve was 0.622(95%CI= 0.513-0.722,sensitivity =71.43%and specificity=52.94%).ConclusionOur study demonstrated that the upregulation of CSN6 were observed in both gastric cancer cell lines and human tissues.There was a significant correlation between CSN6 and the outcome of gastric cancer patients,especially for advanced gastric cancer patients.High expression of CSN6 will shorten the overall survival time of gastric cancer patients and low expression of CSN6 will prolonged the overall survival time of gastric cancer patients.All the above results reminded that CSN6 might be a promising candidate to evaluate the outcome of gastric cancer patients and may provide a novel target for gastric cancer targeted therapy. |
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