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Adipose-derived stem cells (ASCs) are abundantly present in the mammary microenvironment and can promote breast cancer malignancy by differentiating into myofibroblasts. However, it remains largely unclear which role tumor-derived extracellular vesicles (TEVs) play in this process. Here, we used microfabricated, type I collagen-based 3-D tissue culture platforms to investigate the effect of breast cancer cell-derived TEVs on ASCs myofibroblast differentiation and consequential changes in extracellular matrix remodeling and vascular sprouting. TEVs collected from MDA MB-231 human metastatic breast cancer cells (MDAs) promoted ASC myofibroblast differentiation in both 2-D and 3-D cultures as indicated by increased alpha smooth muscle actin (α-SMA) and fibronectin (Fn) levels. Correspondingly, TEV-treated ASCs were more contractile, secreted more vascular endothelial growth factor (VEGF), and promoted angiogenic sprouting of human umbilical vein endothelial cells (HUVECs). These changes were dependent on transforming growth factor beta (TGF-β)-related signaling and tumor cell glutaminase activity as their inhibition decreased TEV-related myofibroblastic differentiation of ASCs and related functional consequences. In summary, our data suggest that TEVs are important signaling factors that contribute to ASC desmoplastic reprogramming in the tumor microenvironment, and suggest that tumor cell glutamine metabolism may be used as a therapeutic target to interfere with this process. [ABSTRACT FROM AUTHOR]

Breast cancer cells recruit surrounding stromal cells, such as cancer-associated fibroblasts (CAFs), to remodel their extracellular matrix (ECM) and promote invasive tumor growth. Two major ECM components, fibronectin (Fn) and collagen I (Col I), are known to interact with each other to regulate cellular behavior. In this study, we seek to understand how Fn and Col I interplay and promote a dysregulated signaling pathway to facilitate tumor progression. Specifically, we investigated the evolution of tumor-conditioned stromal ECM composition, structure, and relaxation. Furthermore, we assessed how evolving Fn-Col I interactions gradually affected pro-angiogenic signaling. Our data first indicate that CAFs initially assembled a strained, viscous, and unfolded Fn matrix. This early altered Fn matrix was later remodeled into a thick Col I-rich matrix that was characteristic of a dense tumor mass. Next, our results suggest that this ECM remodeling was primarily mediated by matrix metalloproteinases (MMPs). This MMP activity caused profound structural and mechanical changes in the developing ECM, which then modified vascular endothelial growth factor (VEGF) secretion by CAFs and matrix sequestration. Collectively, these findings enhance our understanding of the mechanisms by which Fn and Col I synergistically interplay in promoting a sustained altered signaling cascade to remodel the breast tumor stroma for invasive breast tumor growth. [ABSTRACT FROM AUTHOR]