MicroRNA-34a Regulates YAP To Influence Breast Cancer Biological Behavior And Its Mechanism

Objective:To observe the changes in the biological behavior of breast cancer cells MDA-MB-231 and BT-549 by up and down microRNA-34a,and to observe the relationship between YAP and hippo signaling pathway in order to explore miR-34a in breast cancer role and mechanism.Methods:Human normal breast cancer cell lines MCF-10A,breast cancer cell lines MDA-MB-231,BT-549 were used to verify the expression of miR-34a;After selecting breast cancer cell lines MDA-MB-231 and BT-549 transfected with miR-34a mimics and inhibitors,the CCK-8 experiment was used to detect the cell proliferation ability and the transwell experiment to detect cell invasion and migration ability;Then the qPCR experiment was used to detect the expression of YAP in the hippo signaling pathway after up-regulation and down-regulation of microRNA-34a;At the same time,western blot was used to detect the expression of YAP protein and epithelial mesenchymal phenotype proteins E-cadherin,N-cadherin,Vimentin;Finally,after simultaneous transfection with miR-34a inhibitor and YAP inhibitor,CCK-8 and transwell cell experiments were conducted to observe the cell proliferation ability and invasion and migration ability.Results:qPCR showed that miR-34a expression in breast cancer cells MDA-MB-231 and BT-549 was significantly lower than that of normal breast cancer cell line MCF-10A(P<0.05);The CCK-8experiment showed that after transfection with miR-34a mimic,the cell proliferation rate was significantly slowed down,and after transfection with its inhibitor,its proliferation ability was significantly enhanced(P<0.05);Transwell experiments showed that after increasing the expression of miR-34a,its invasion and migration ability was significantly lower than that of the control group(P<0.05),and after inhibiting the expression of miR-34a,its invasion and migration ability was significantly increased than that of the control group(P<0.05).Then,after up-regulating miR-34a in breast cancer cell lines MDA-MB-231 and BT-549,YAP gene and protein were both down-regulated(P<0.05),and after inhibiting the expression of miR-34a,the expression level of YAP was again significant increased(P<0.05);Western Blot results showed that the expression levels of interstitial cell markers N-cadherin and Vimentin of MDA-MB-231 and BT-549 decreased after up-regulation of miR-34a expression(P<0.05),while after down-regulation of miR-34a expression,The expression levels of interstitial cell markers N-cadherin and Vimentin increased significantly(P<0.05);in the BT-549 cell line,the expression level of epithelial phenotype protein E-cadherin was positively correlated with miR-34a,Compared with the control group,the difference was statistically significant(P<0.05);In addition,after inhibiting the expression of miR-34a,the proliferation,invasion and migration ability of breast cancer was significantly higher than that of the control group(P<0.05),and after being simultaneously transfected with miR-34a inhibitor and YAP inhibitor,its proliferation,invasion and migration ability compared with simple inhibition of miR-34a,it decreased correspondingly(P<0.05).Conclusions:miR-34a can affect the proliferation,invasion and migration of breast cancer cells,and its mechanism may be closely related to the hippo signaling pathway.The key factor YAP in the hippo signaling pathway may be the downstream target of miR-34a.miR-34a may affect the proliferation,invasion and migration of breast cancer cells by regulating the expression level of YAP and mediating the EMT process,thereby affecting the occurrence and development of breast cancer.