Efeito das interações célula-matriz extracelular na transição epitélio-mesênquima do carcinoma de mama: papel de integrinas

Abstract

Alterations in the composition and architecture of the extracellular matrix (ECM) can influence cancer growth and dissemination. ECM is a complex physical barrier that must be overcome by tumor cells to allow their escape from primary sites and invasion of tissues during metastasis. Epithelial-mesenchymal transition (EMT) is a cellular process that allows a polarized epithelial cell to assume a mesenchymal cell phenotype, contributing to metastasis. During EMT, epithelial cells change their profile from cell-cell contacts to mostly cell-matrix interactions. Breast tumors usually present cells at different stages of differentiation that are able to produce distinct extracellular matrices. However, the contribution of ECM derived from metastatic tumor cells to EMT has not yet been investigated. Here, we have investigated the mechanisms involved in the effects resulting from the interaction of MCF-7, a low-metastatic epithelial breast cancer cell line, with the ECM produced by MDAMB-231, a high-metastatic breast tumor cell line. Our data show that compared to the ECM derived from MCF-7 (MCF-ECM), the ECM produced by MDAMB-231 cells (MDA-ECM) has considerably different composition, with higher expression of tenascin-C, laminin, osteopontin, and vitronectin contents and lower expression of fibronectin. The interaction of MCF-7 cells with MDA-ECM induced morphological changes in MCF-7 cells, characteristics of mesenchymal cells. There was a decrease in expression of the epithelial marker E-cadherin and up-regulated mesenchymal markers, contributing to the increase in their migration capability. Induction of EMT was independent of the presence of TGF-β and dependent on the direct contact of MCF-7 cells with MDA-ECM. These interactions triggered the activation of integrin-associated signaling, increasing the phosphorylation of FAK, ERK, and AKT and activating SMAD2 and SMAD4 nuclear translocation in MCF-7 cells. Blockage of integrins impaired the shift to the EMT profile induced by MDA-ECM, maintaining epithelial morphology and E-cadherin-mediated adhesions, and inhibited SMAD2 phosphorylation. Preliminary analysis, by microarray, of MCF-7 cells that interacted with the MDA-MEC showed modification of genes involved in cell-ECM adhesion, migration, EMT and tumor progression. Our findings revealed ECM derived from metastatic tumors may act as a trigger of EMT in breast cancer epithelial cells, mediated by integrin-associated signaling, leading to a mesenchymal cell transition. These data contribute to the understanding of adhesion-related interactions during breast cancer progression and may aid in the development of antimetastatic therapies.