Identification Of Microrna Signature As An Independent Predictor Of Prognosis In Gastric Cancer Patients After Curative Resection

Objective: Gastric cancer is one of the most common malignant tumor in the world.Determining the important factors affecting the prognosis of gastric cancer and takingeffective measures to intervene can reduce the death rate from gastric cancer. Recentstudies show that the changing of microRNA (miRNA) expression level was associatedwith gastric cancer. It has been confirmed that microRNA (miRNA) expression level isclosely related to the prognosis of gastric cancer. In this experiment, we obtained somemiRNAs which were significantly differentially expressed in gastric cancer tissuescompared with adjacent normal tissue by screening.We then combine these three miRNAsto construct a signature which can better predict the prognosis of gastric cancer.Methods: We screened miRNAs which were significantly differentially expressed in5pairs of gastric cancer tissues and adjacent normal tissue using two-color tagmicroRNA chip which is bought from American LC laboratory and is the latest one in theworld. A total of110Paraffin specimens of gastric cancer obtained after radical surgery inchangzheng hospital from January2005to October2006were recruited. All the sampleswere randomly divided into test group and validation group which including55casesrespectively. MiRNAs expression level was detected by real-time quantitative PCR. ThemiRNAs which were significantly differentially expressed in gastric cancer tissuescompared with adjacent normal tissue were selected as single factor analysis variables inCOX regression model. The miRNAs which were associated with the prognosis of gastriccancer were obtained by screening. It is lack of specific marker for predicting theprognosis of patients with gastric cancer. In order to more fully and effectively determimethe prognosis of patients.We established a risk miRNA signature consisting of prognosisrelated miRNAs in gastric cancer and evaluated the risk of miRNAs signature usingmedian value of risk as the critical point. Meanwhile, the predictive value of this miRNAssignature on overall survival and disease-free survival time of gastric cancer was evaluatedusing Kaplan Meier survival analysis. The age, sex, tumor differentiation degree,pathological stage, tumor size and miRNA signaute were included in the multivariate Coxregression analysis model as research variables and the independent risk factors affectingsurvival prognosis of patients with gastric cancer was performed. The independentpredictive value of miRNA signature for the prognosis of patients with gastric cancer wasverified again using the55cases of validation group. At last, we studied the relationshipbetween miRNA signature and survival prognosis of patients with gastric cancer aftercombining the two groups and classifying all the patients according to differentpathological stage, tumor size, degree of differentiation.Results:7different miRNAs which were significantly differentially expressed ingastric cancer tissues compared with adjacent normal tissue were abtained by screeningusing miRNA gene chip.5kinds of which were highly expressed in gastric cancer（miR-21，miR-181d，miR-181a-1，miR-181a-2，miR-224）and2with low expressionin gastric carcinoma（let-7g，miR-148a）. The difference of expression level of7miRNAs in55gastric cancer patients of test group was verified using RT-PCR. We found that6kinds of miRNAs were expressed significantly different compared with adjacent normaltissue, in which2are high expression （miR-21,miR-181a-1）and4are low expression（miR-181a-2，miR-148a，let-7g，miR-181d）.3kinds of miRNAs were verified to beassociated with the prognosis of gastric cancer（miR-21high expression；miR-181a-2andmiR-148a low expression）. The risk miRNA signature consisting of3kinds of miRNAscan be used to predict the prognosis of gastric cancer patients effectively. The overallsurvival and disease-free survival time of patients expressing high risk miRNA signature isshort. On the contrary, these who expressed low risk miRNA signature is long. MultivariateCox regression analysis showed that miRNA risk signature was the independent risk factorfor the prognosis evaluation of gastric cancer. In addition, we found that miRNA risksignature was the important prognostic factor of gastric cancer which was independent ofpathological stage, differentiated degree and tumor size by using stratification analysis.Conclusion: Compared with adjacent normal tissue,3kinds of miRNAs（miR-21，miR-181a-2，miR-148a）were significantly differentially expressed in gastric cancer tissuesand were significantly related to the prognosis of patients with gastric cancer. The riskmiRNA signature composed of these3kinds of miRNAs can be more comprehensive andeffective in the prediction of overall survival time and disease-free survival time of gastriccancer patients. In addition to this, the risk miRNA signature was also independent riskfactors for the prognosis of gastric cancer.