EZH2Influence The Porgnosis Of Cervical Cancer And Regulate The Proliferation Of Caski Cervical Cancer Cells

BackgroundCervical cancer is the third most common female cancer ranking after breast (1.38million cases) and colorectal cancer (0.57million cases) in the world. It is accounting for9%(529,800) of the total new cancer cases and8%(275,100) of the total cancer deaths among females in2008and more than85%of these cases and deaths occur in developing countries. Although cervical cytology screening has greatly decrease the incidence and mortality of cervical cancer in the world, cervical cancer is still a major cause of cancer related death in developing countries. Even in developed countries, the cost and morbidity associated with management of cervical cancer is still substantial. To improve better prognostic and develop new therapeutic strategies for cervical cancer, deep research into molecular and biological mechanisms of tumorigenesis is critical.As we all know, persistent human papillomavirus infection is the main cause of cervical cancer. Holland had found that HPV-positive dysplastic and tumorigenic cervical lesions were characterized by high levels of enhancer of zeste homolog2(EZH2) protein in vivo, which belongs to polycomb group protein (PcG) and functions as a catalytic subunit of the polycomb repressive complex2(PRC2). PRC2, which is composed of EZH2, EED and SUZ12, plays crucial roles in transcriptional regulation through nucleosome modification, chromatin remodeling. Moreover, EZH2, is found to act as a histone methyltransferase for lysine27of histone H3, contributing to the maintenance of cell proliferation and cell cycle regulation. EZH2was shown to be overexpressed or amplified in aggressive forms of several malignancies (including gastric cancer, gallbladder adenocarcinoma, ovarian cancer and bladder cancer) and suggested to be a factor for poor prognostic of cancers.ObjectiveTo illustrate the role of EZH2in proliferation, progression and prognosis of cervical cancer and assess the function and mechanism in tumorigenesis.MethodsWe detected EZH2and Ki-67expression using immunohistochemistry in20normal cervical tissues,20cervical intraepithelial neoplasia (CIN) and101cervical cancer tissues. The relationships between EZH2expression and Ki-67expression, conventional clinicopathological characteristics of cervical cancer and patient outcomes were evaluated. The effect of EZH2expression on cancer specific survival was assessed by multivariate Cox regression analyses. To investigate the biological effect of EZH2expression in ovarian cancer cells, we chose the strategy to specifically silence EZH2expression by siRNA and subsequently analyzed the effect of EZH2on the proliferation of cervical cancer cells. To evaluate the effect of EHZ2depletion on the resulting gene expression, real-time PCR and western blot were performed to detect the expression of the resulting gene mRNA and protein in cervical cancer cells transfected EZH2-siRNA.Results:1. EZH2was low expression in normal cervical tissues and Positive expression rate of EZH2was10%(2/20); in CIN tissues positive expression rate of EZH2(60%12/20) was higher than normal cervical tissues and the difference between two groups have statistical sense (P<0.05); positive expression rate of EZH2(68.3%69/101)in cervical cancer was higher than CIN tissues and the difference between two groups have statistical sense; The difference between cervical cancer group and CIN group have no statistical sense (P=0.470). The expression of EZH2gradually increased from the normal cervical, CIN to cervical cancer.2. The expression of Ki-67gradually increased from the normal cervical, CIN to cervical cancer and their positive rate were5%(1/20)、50%(10/20),57.4%(58/101) respectively. The expression of Ki-67is positively correlated with EZH2expression in cervical cancer tissues (r=0.440, P<0.05)3. The expression of EZH2was significantly associated with clinical stage, histological differentiation, infiltration depth and lymphnode metastasis (P<0.05). EZH2exhibited no significant association with other clinicopathological characteristics, such as age, tumor size, and histological type.4. Kaplan-Meier analysis showed that the average survival time in EZH2-positive cases was42.3months, significantly lower than the average survival time(53.3months) in those cases with negative EZH2expression(53.3), and the difference between two groups have statistical sense (P<0.05). Multivariate Cox regression analysis suggested that EZH2was an independent predictor of poor prognosis in cervical cancer.5.48hours after transfection, the suppressive effect of EZH2on the proliferation of cervical cancer cells was the most obvious. And EZH2knockdown could depress the proliferation ability of cervical cancer cells.6. By using RT-PCR and Western-Blot, the efficiency of siRNA-mediated EZH2silencing was monitored at both the mRNA and protein expression level and it also increased the expression of P57on protein and mRNA level.ConclusionEZH2was overexpression in cervical cancer and significantly associated with clinical stage, histological differentiation, infiltration depth, lymphnode metastasis and prognosis of cervical cancer. Aberrant up-regulation of EZH2expression was often associated with more proliferative characters. But EHZ2depletion can heighten the expression of p57, which could suppress the proliferation of cancer cells. Our findings imply the potential of EZH2to serve as a novel targets for therapeutic intervention and a diagnostic for patients with ovarian cancer marker.