Tumoral hypoxic extracellular vesicles create a protective microenvironment for triple-negative breast cancer

Abstract

The highly metastatic triple-negative breast cancer (TNBC) relies on its tumor microenvironment (TME) to maintain phenotypic heterogeneity and progression. Extracellular vesicles from hypoxic TNBC were previously shown to aid tumoral invasion but their function in the tumor microenvironment is still unclear. We used a novel method to investigate the TME in vitro called multicellular circulating co-culture, to characterize how TNBC-derived hypoxic EVs (EVh) interfere with tumoral and endothelial cells, fibroblasts, monocytes and macrophages. EVh promoted monocyte differentiation to M2-like macrophages and inhibited macrophage-derived phagocytosis in endothelial and tumoral cells. The protection of endothelial, tumoral and stromal cellular integrity by EVh increased pro-tumoral and pro-angiogenic signaling, collagen matrix synthesis and a potential differentiation to cancer-associated fibroblasts. Our findings highlighted the critical role of EVh in protecting tumor cells, indicating its cooperation towards a protective TME, which was demonstrated by the multicellular circulating co-culture and conventional co-culture protocols, leading to an adequate system with potential for investigating other tumor-related processes, including circulating tumor cells and metastasis.