Sam68 Overexpressing Accelerates Epithelial-Mesenchymal Transition Of Breast Cancer MCF-7 Cells

Background: Breast cancer is the highest incidence of malignancy in women which accounts for 25% of the total number of new malignancies in women.Mortality accounts for 15% of female malignancies which seriously endangers the majority of women’s health and life safety.With the development of the treatment program and treatment,the effect of breast cancer treatment has been significantly improved that 5-year survival rate was 72.7%.But the high heterogeneity of breast cancer affects the prognosis factors of many patients.For example,different molecular types and metastatic tumor are closely related to prognosis.Especially in patients with distant metastases 5-year survival rate was only 23.3%,the median survival time was only 1.2 years[3].Therefore,screening and identification of molecular mechanisms of breast cancer metastasis and related tumor markers are beneficial to the development of new specific targeted drugs which has a very important theory and application value for improving the effectiveness of breast cancer treatment.In recent years,several articles at home and abroad reported: In the development and treatment of breast cancer,the emergence of tumor cell metastasis and epithelial mesenchymal transition(epithelial-mesenchymal transition,EMT)is closely related.When EMT occurs in tumor cells,cells will lose polarity and cause cell adhesion stability and cytoskeleton rearrangement,enhance the movement ability.It is easy to fall off from the primary lesion and it is also easier to penetrate the vessel wall and then migrate to the body.At the same time,EMT can induce breast cancer cells for stem cell changes to increase the proportion which enhances the anti-apoptosis and distant metastasis of tumor cells.Therefore,EMT is an early critical event of tumor local invasion and distant metastasis.In the preliminary study of this group,it was found that the expression level of Sam68 was up-regulated in breast cancer tissues and it was confirmed that the expression level of Sam68 was negatively correlated with E-cadherin.By down-regulated the expression of Sam68 in MDA-MB-231 cells with high invasive breast cancer,the expression level of E-cadherin protein can be up-regulated to inhibit the occurrence of tumor EMT,reduce the ability of tumor cell proliferation,invasion and distant metastasis.However,overexpression of Sam68 can promote the EMT transformation of breast cancer MCF-7 cells(epithelioid cells),and thus enhance the ability of tumor cell proliferation,invasion and distant metastasis which remains to be studied.Objective:To investigate the overexpression of Sam68(Src-associated in mitosis 68 kD)on epithelial-mesenchymal transition in breast cancer MCF-7 cells(epithelial-mesenchymal transition,EMT)and the effect of tumor cell proliferation,invasion and migrationMethods:Respectively,setting the experimental group,negative control group with construction of plasmid vector.The experimental group MCF-7 cells were transfected with pcDNA-3-Sam68 recombinant plasmid carrying Sam68 gene and the negative control group was transfected with pcDNA-3 empty plasmid.Real-time fluorescence quantitative PCR and western blotting were used to detect the two groups Sam68 and EMT markers E-cadherin,N-cadherin,Vimentin mRNA and Protein expression.CCK-8 method and transwell chamber were used to detect the proliferation,migration and invasion of the two groups.Results:After 48 h of transfection of MCF-7 cells,the expression of Sam68 mRNA and protein in the experimental group was significantly overexpressed(P<0.05).There were no significant changes in EMT markers including E-cadherin,N-cadherin and Vimentin mRNA(P>0.05).But the expression level of E-cadherin protein was significantly down-regulated(P <0.05).While the expression levels of N-cadherin and Vimentin protein were significantly up-regulated(P <0.05).And it is founded that tumor cell proliferation,migration and invasive ability was significantly enhanced(P <0.05).Conclusion: Sam68 overexpression promotes the development of breast cancer MCF-7 cells and it enhances cell proliferation,migration and invasion.