BMP-2 Promotes Breast Cancer Metastasis by Inducing EMT via PI3K/Akt Signaling Pathway

Abstract

Abstract Purpose:Bone morphogenetic proteins (BMPs) are important members of the TGF-β superfamily and can be abnormally expressed in various tumors. The purpose of this paper is to investigate the expression of bone morphogenetic proteins-2(BMP-2) in breast cancer and its effects on breast tumor cells and the regulation mechanism.Method:The effects of BMP-2 on the proliferation, cloning, apoptosis, migration and invasion of breast cancer cells were investigated by MTT assay, plate cloning experiment, flow cytometry (FCM), scratch test and transwell assay. The relationship between BMP-2 and epithelial-mesenchymal transition (EMT)-related indicators in cell lines, and the relationship between BMP-2 and PI3K/Akt pathway-related proteins were analyzed using real-time PCR and Western blot. Breast cancer xenograft models were established to observe effects of BMP-2 on the growth and metastasis of xenograft tumors, and real-time PCR and immunohistochemistry were used to detect changes in EMT-related protein expression in xenograft tumors.Results:BMP-2 was highly expressed in MBA-MD-231 and T47D cell lines. The results of in vitro experiments showed that rhBMP-2 could promote the proliferation, colony formation, migration and invasion of breast cancer cells, and reduce the apoptosis ability. The expression of BMP-2 was significantly correlated with EMT. With increasing BMP-2 concentration, the expression of E-cadherin and Cx43 was significantly down-regulated in the epithelial phenotype, while the expression of N-cadherin, fibronectin (FN), and vimentin mRNA was significantly up-regulated in the mesenchymal phenotype. BMP-2 could promote p-PI3K, p-Akt and p-mTOR expression in the PI3K/Akt signaling pathway, which in turn regulated the EMT process. However, after the addition of LY294002, an inhibitor of this signaling pathway, no significant up-regulation of p-PI3K, p-Akt, and p-mTOR was observed, and there was no significant change in EMT-related indicators. Through the establishment of the BMP-2 high expression xenograft model in nude mice, it was found that the growth rate of xenograft in the BMP-2 group was significantly faster than that in the control group, and metastasis to lymph node and bone were likely to occur. Compared with the control group, E-cadherin expression was attenuated and vimentin expression was enhanced in the BMP-2 group, suggesting EMT.Conclusion:BMP-2 is highly expressed in breast cancer tissues and is a malignant regulator of breast cancer cells. Its mechanism of action may be the induction of the EMT via PI3K/Akt pathway. BMP-2 is expected to be a new target for controlling the growth and metastasis of breast cancer.