| ObjectiveBreast cancer is a serious malignant tumor which hazards to the health of women. Epithelial-mesenchymal transition(EMT) is a transdifferentiation of epithelial cells to mesenchymal cells. There is a closely relationship between EMT and tumors’ invasion, metastasis, drug resistance and cancer stem cells. Epidermal Growth Factor (EGF) is one of the cell factors which can induce EMT.CTEN(COOH-terminus tensin-like molecule) gene is a member of the tension genes family, which participates in cell adhesion, migration and signal transmitting. Over-expression of CTEN is associated correlated with invasion and migration of the malignant tumor and the prognosis of the patients. Researches showed that, CTEN participated in the EMT of colorectal cancer.There are no deep investigations on CTEN and its influences on breast cancer. How does CTEN influence the generation of breast cancer? In this study, we tested the CTEN expression in breast cancer tissues and cell lines, and discussed the possible mechanism of CTEN on EMT. It will increase the recognition to CTEN and uncover new molecular mechanism of the EMT in breast cancer.Methods1. The expression of CTEN and p-ERK1/2was detected in invasive breast cancer by immunohistochemistry, then analysising the relationship between protein expression and clinicopathological parameters, and the association of two proteins.2. Exogenous EGF was used to stimulate MCF-7cells, then morphological changes of cells were observed, and the expression of CTEN, E-cadherin and vimentin was detected by Western blot. The specific CTEN-small interference RNA (siRNA) was constructed and transfected into MCF-7cells using lipofectamine, the expression of CTEN mRNA was detected by real-time fluorescence quantitative PCR, finally the most efficient siRNA was screened out for the follow-up experiments.3. EGF was used to stimulate MCF-7cells, then transfecting CTEN-siRNA and using U0126to blocking the ERK signal pathway, the morphological changes of cells were observed, and the expression of CTEN, E-cadherin, vimentin, ERK1/2, p-ERK1/2, Raf-1and Snail protein was detected by Western blot. The number of invasive cells was determined by Transwell assay.Results1. The positive rate of CTEN in breast cancer was88.1%, while p-ERK1/2was83.3%. CTEN and p-ERK1/2both associated with the loss of tumor differentiation, clinical stage, lymph node metastasis and N-cadherin expression (P＜0.05). There was a significant positive correlation between the expression strength of CTEN and p-ERK1/2(r=0.526, P＜0.01).2. After EGF was used to stimulate MCF-7cells, epithelial-like to mesenchymal-like changes in cells morphology were observed, and the expression of CTEN and vimentin protein was increased, as well as E-cadherin protein was decreased. CTEN-siRNA can suppress CTEN mRNA expression effectively (inhibition＞90%).3. EGF was used to stimulate MCF-7cells. After transfection, it was found that mesenchymal-like to epithelial-like changes in cells morphology, and the expression of CTEN, vimentin, ERK1/2, p-ERK1/2, Raf-1and Snail protein was decreased, E-cadherin protein was increased. The expression of p-ERK1/2and Snail protein was decreased, but Raf-1protein expression did not change after using U0126.After transfection, the number of invasive cells did not significantly increase even if using exogenous EGF to stimulate MCF-7cells (P＜0.05).Conclusion1. It suggested that the expression level of CTEN protein was closely related to biological behavior of breast cancer, and there was a significant positive correlation between the expression strength of CTEN and p-ERK1/2.2. Exogenous EGF could promote breast cancer MCF-7cells occurring EMT, and the expression of CTEN protein was increased after occurring EMT.3. Suppressing CTEN expression could partly inverse EMT by EGF-induced, because CTEN silencing could block activation of Ras/Raf/MEK/ERK/Snail signal pathways due to reducing Raf-1protein expression.4. Suppressing CTEN expression could partly inverse invasive ability of MCF-7cells enhancing by EGF-induced. |
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