Clinical Study Of The Relationship Between COX-2 And Biological Behavior In Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the common digestive malignancies worldwide[1].Obviously, the the first treatment choice for resectable ESCC is surgery. Though combined therapies for ESCC have a great advance, the prognosis of patients remains poor and the 5-year survival rate is desperate, merely 20-30%[2,3].More than half of the patients developed recurrence within 2-3 years after surgery [4]. As far as we know,the prognosis of ESCC patients is tumor-node-metastasis (TNM) staging-specific. But we could not just estimate prognosis through TNM stage.Because the TNM stage is lack of sensitivity and accuracy. Therefore, finding a biomarker may assist in identifying the high-risk patient with poor prognosis,which is significant to guide further treatment. There are plenty of reports about biomarkers of prognosis of ESCC patients [5]. However,no specific biomarker has been adopted pervasively and applied routinely in ESCC until now. Therefore,more receivable biomarkers,which could exactly predict prognosis of ESCC patients, are imminently required.The cyclooxygenase(COX) system played an crucial role in the carcinogenesis of esophogeal carcinoma by promoting the process from esophagitis to dysplasia and carcinoma[6].COX2,one of the two iso-enzymes of COX,is absent or low in normal adult tissues,whereas has been involved in the increased proliferation. As an important regulator of cell growth,differentiation,apoptosis,and transformation,COX2 overexpression significantly associates with the tumorigenesis and progression of diverse cancers,including the squamous cell carcinomas(SCCs) of the head and neck,lung,vagina and uterine cervix[7,8,9]. It has been clarified that overexpression of COX2 correlates with a dismal prognosis in gastrointestinal tumors by decrease the apoptosis and increase invasiveness[10]. But there were few reports about the expression of COX2 in ESCC and the clinicopathological significance and prognostic value of COX2 in ESCC is still unclear. In this study,we aimed to investigate the expression of COX2 in 118 ESCC patients and explore whether the expression of COX2 can predict prognosis of ESCC after surgery or not.While nowadays the reports on the role of COX-2 in metastasis of esophageal cancer were very rare. In this study,we aimed to investigate the expression of COX2 in 118 ESCC patients and explore whether the expression of COX2 can predict prognosis of ESCC after surgery or not.ObjectiveThe incidence of lymph node metastasis of esophageal squamous cell carcinoma (ESCC) was shown to be positive correlated with tumor chemotactic migration and lymphangiogenesis. This study was to to investigate the expression of COX-2 and its relationship to prognosis in ESCC after esophagectomy.MethodFrom October 2006 to September 2009, we analyzed retrospectively the mid-thoracic ESCC patients who received complete resection (R0 resection) in Provincial Hospital Affiliated to Shandong University with intact clinical information. The specimens consisted of 91 male and 27 female patients aged 38-74 years (mean 60 years).All of them accepted Ivor-Lewis esophagectomy. Preoperative radiotherapy or chemotherapy was not taken to all cases. We detected the expression of COX-2 by the way of immunohistochemistry and western blot. According to the clinicopathologic factors, we compared the difference of COX-2 expression through the way of ?2 test. Kaplan-meier method was performed to count the survival rate, Cox regression multivariate analysis was performed to identify the independent prognostic factors.The SPSS 19.0 statistical software was used for all statistical analyses. When the P value was<0.05,the difference was regarded as significant.Then, Eca109 cells were transfected by lentivirus with COX-2siRNA to block the expression of COX-2. Western blotting was employed to identify the downregulation of the COX-2 expression in the transfected Eca109 lines. Meanwhile, lentivirus without COX-2siRNA was used to transfect Eca109 lines as the blank control group. Transwell assay and MTT assay was used to investigate the influence of downregulating the expression of COX-2 on cell proliferation and invasion.ResultsThe expression rate of COX-2 in ?+? stage and ?+? stage was separately 54.3% and 83.1%, the difference of COX-2 expression in ?+? stage and ?+? stage was obviously significant in statistical analysis (?2=12.219, P=0.002). The rate of COX-2 expression inTl, T2 stage and T3+T4 stage was separately 50.0%? 60.0% and 82.5%, the difference of COX-2 expression in T1 stage, T2 stage and T3+T4 stage was obviously significant in statistical analysis (?2=8.559, P=0.014). The positive expression of COX-2 in patients without lymph node metastasis was significantly lower than those with lymph node metastasis (?2=6.805, P=0.009). Kaplan-Meier analysis revealed that the overall 5-year survival rate was 20.34% and patients without COX-2 protein overexpression had a 5-year survival rate of 50.00% compared to 10.22% of those with COX-2 protein overexpression; the 5-year survival rate in patients without COX-2 positive expression was significantly higher than those with COX-2 positive expression (P< 0.01). The result of Cox analysis demonstrated that histological differentiation, TNM stage of tumors and COX-2 positive expression were independent prognostic factors.Then, the recombinant lentiviral vector was transfected into human ESCC cell line Eca109 successfully. After transfected by lentivirus with COX-2siRNA, Eca109 cells were detected with constant downregulation of COX-2 expression by RT-PCR and western blot. We found that downregulating the expression of COX-2 can inhibit cell proliferation and invasion in Eca109 cells.Conclusionswe demonstrated that overexpression of COX2 was significantly associated with key adverse clinicopathological features. Cox regression analysis indicated that the high expression of COX2 protein is an independent risk factor for prognosis. COX-2siRNA can block the expression of COX-2,which is associated with the cell proliferation and invasion in esophageal squamous cancer Eca109 cell lines.These results suggest that COX2 must be a prognostic factor and might be a new potential therapeutic target for ESCC.