The Expression And Function Of Stathmin 1 In Non-small Cell Lung Cancer

Background: Lung cancer is the most common malignant tumor as well as the leading cause of cancer-relateddeaths around the world.According to the 2010 China tumor registration annual report,the incidence rates of lung cancer occupies the first position in China.Lung cancer has become an important diseases endangering human health,brought heavy economic burden to society and family.Non-small cell lung cancer(NSCLC),which accounts for about 85% of all lung cancer,is an important part of lung cancer.While early NSCLC can get cured by surgery,however,due to symptoms of early NSCLC is not obvious,many patients have lost the best operation time when diagnosed.Although some advanced patients can improve symptoms and prolong life by chemotherapy,radiotherapy and comprehensive treatment such as molecular target therapy,given the cancer development mechanism is complex,its difficult to maximize treatment effect and limit side effects at the same time,NSCLC remains one of the most clinically challenging cancers.Thus,to provide better treatment strategies,there is anurgent requirementto identify new prognostic biomarkers andtherapeutic targets for NSCLC.Stathmin 1(STMN1)is a major cytosolic phosphoprotein,which plays a crucial rolein the control of cellular division and proliferation by regulating thedynamics of the microtubules.In addition to its role in mitosis and cell cycle progression,STMN1 is involved in a wide variety of human cancers,including gastric cancer,nasopharyngeal carcinoma,colorectal cancer,and endometrial carcinoma,etc.And the differential expression often highly associated with the postoperative survival of cancer patients.For example,Kang et al.showed that STMN1 was upregulated in gastric cancer cell lines andprimary gastric adenocarcinomas.Ke and coworkers suggested thatoverexpression of STMN1 was associated with poor prognosis of patients with gastric cancer.Additionally,high STMN1 expressionwas associated with poorrecurrence-free and overall survival inendometrial carcinoma.Taken together,these facts indicated that there may be a strong correlation between STMN1 expression and cancer aggressiveness.Chen et al.suggested that overexpression of STMN1 correlated with poor differentiation in lung adenocarcinomas.However,whether the aberrant expression of STMN1 in NSCLC is associated with malignancy,metastasis,or prognosis remains unknown.In this study,we examined STMN1 expression in tissue of patients with NSCLC,and analyzed its expression with clinicopathological parameters and prognosis,and byin vitro cell function experiment,we verified the preliminary biological function of STMN1 in NSCLC.Experiment was divided into two parts: First,collect the fresh carcinoma and adjacent normal tissues of NSCLC patients and paraffin specimens,detected the STMN1 m RNA and protein expression in clinical samples of NSCLC patients,and then analyzed its correlation with clinicopathological parameters and prognosis of NSCLC patients,as well as its clinical application value;Second,by gene transfection technology,the two-way knockdown the STMN1 level in NSCLC cell lines,detected the influence of STMN1 on in vitro NSCLC proliferation and metastasis,clearifiedthe function STMN1 in the development of NSCLC.Part I: The expression and clinical significance of STMN1 in gastric cancerObjective:toexamine the STMN1 expression level in tissue of patients with NSCLC,and analyzed its expression with clinicopathological parameters and prognosisMethods: NSCLC tissues and matched adjacent normal tissue were collected and extracted RNA.At the same time,collected the paraffin embedded tissues of patients with NSCLC.The expression pattern of STMN1 messenger RNA(m RNA)was analyzed by quantitative real-time polymerase chain reaction(q RT-PCR)in 37 cases of NSCLC and in corresponding non-tumor tissue samples.Furthermore,immunohistochemistry was performed to detect STMN1 protein expression in 113 primary NSCLC tissues.Significant between-group differences were estimated using chi-squared tests,Student's t-tests,or Fish's exact test,as appropriate.Kaplan-Meier analysis with the log-rank test was employed to evaluate the relationship between STMN1 expression and DSS.The univariate and multivariate Cox proportional hazards model was utilized to estimate the hazard ratios(HRs)and 95% confidence intervals(CIs)for the outcome.Variables with a value of P<0.05 in univariate analysis were used in subsequent multivariate analysis on the basis of Cox proportional hazards model.Results: STMN1 m RNA and protein levels in NSCLC tissues were significantly higher than those in corresponding non-tumor tissues(P<0.001).In addition,increased STMN1 expression was correlated with poor tumor differentiation(P<0.001),large tumorsize(P=0.022),advanced N stage(P=0.033),and advanced TNM stage(P<0.001).Kaplan-Meier analysis indicatedthat NSCLC patients with higher STMN1 expression showed significantly worse survival.Moreover,multivariate analysis indicated that higher STMN1 protein expression was an independent prognostic factor of disease-specific survival.Conclusion: The relative expression levels of STMN1 was significantly higher in tumor tissues compared with adjacent normal tissues.In addition,high expression of STMN1 was correlated with larger tumor size,lymph node metastasis,and TNM stage.Patients with high STMN1 expression had a poor disease-specific survival(DSS),and increased expression of STMN1 was an independent predictor of DSS.Part II: The function of STMN1 in NSCLCObjective: to analysis the biological function of STMN1 on in vitroproliferation and invasion.Methods:(1)the specific si RNA of STMN1 were transfected into NSCLC cells through Dharma FECT 1,and the expression level of STMN1 was detected by q RT-PCR and Western blot(2)The functional role of STMN1 in lung cancer cell lines were evaluated by small interfering RNA-mediated depletion,followed by analyses of cell proliferation and invasion.by CCK-8 and Transwell method,respectively.Results:(1)q RT-PCR and Western blot results showed that STMNl-si RNA successfully knockdown the expression level of STMN1 in NSCLC cell lines.(2)knockdown of STMN1 in lung cancer cells resulted in a decrease in cellular proliferation and invasion.Conclusion: Our findings suggested that STMN1 may play an important role in NSCLC progression.