The processes of the epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are strongly linked to breast cancer metastasis via their ability to generate cells of increased invasive capacity and enhanced tumor-initiating phenotypes. Numerous growth factors, cytokines and chemotherapies present in the tumor microenvironment are capable of inducing EMT, but the role of extracellular matrix (ECM) components in this process remains less well understood. Analysis of the METABRIC dataset strongly linked high-level FN expression to decreased patient survival. However, in vitro analysis of the MCF-10A progression series indicated that autocrine FN expression was associated with nonmetastatic cells. Therefore, we utilized differential bioluminescent imaging to track the metastasis of these isogenic epithelial and mesenchymal cells within heterogeneous primary tumors. Using this approach, we demonstrate that tumor cells expressing autocrine FN display a constitutively mesenchymal phenotype and are incapable of completing the metastatic process, even when grown within a tumor containing epithelial tumor cells. Importantly, depletion of FN allows tumor cells to exit their mesenchymal state, regain epithelial characteristics and initiate tumor growth in a metastatic microenvironment. Using a tessellated three-dimensional polymer scaffolding, we show that depletion of FN or pharmacologic inhibition of focal adhesion kinase prevents mesenchymal tumor cells from producing structural fibrils and thus supporting the growth and migration of metastatic-competent epithelial tumor cells. Finally, dynamic FN coating of this 3D growth scaffold resulted in formation of a functionalized fibrillar FN network that was sufficient to induce transient EMT events as metastatic cells migrated along FN fibrils. Taken together, our data indicate that autocrine expression of FN by tumor cells supports a stable mesenchymal phenotype limiting their metastatic potential. Instead, this tumor cell-derived production of fibrillar FN acts in a paracrine fashion to support transient EMT events in metastatic competent cells within a heterogeneous tumor microenvironment.
Citation Format: Aparna Shinde, Ammara Abdullah, Luis Solorio, Michael Wendt. Autocrine fibronectin inhibits breast cancer metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2128.