Regulation of extracellular vesicle biogenesis through cell adhesion

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Abstract Metastasis is a well-known driver of cancer-related deaths. Nevertheless, limited success has been achieved in targeting cancer metastasis because it is an exceedingly complex process driven by multiple, integrated mechanisms. Collaborative studies in the Zijlstra and Weaver laboratories studied two separate aspects of cell motility: a) the dynamics of cell-cell adhesion controlled by proteolytic shedding of adhesion receptor and b) the release of motility promoting extracellular vesicles (EV). Since these two events take place in the same cells and contributed to the same phenotype, we speculated that these two biological processes were coordinated. Indeed, preliminary studies demonstrated that syntenin-1, a key component of the EV biogenesis pathways, was part of a cell adhesion complex anchored by the IgG superfamily member Activated Leukocyte Cell Adhesion Molecule (ALCAM) and its companion-tetraspanin CD151. Altering the expression and/or shedding of ALCAM drastically impacted EV biogenesis, confirming our original idea that cell-cell adhesion could be coordinated with EV biogenesis. The hypothesis that this occurred through an intracellular link between ALCAM and syntenin is further supported by the ability of free intracellular domain to suppress EV biogenesis. Based on these observations and our published expertise in cell adhesion, EV biology and metastasis, we propose to investigate the integration between cell-adhesion and the production of motility-promoting EVs during cancer progression. Specifically, the proposed studies will investigate: 1) the mechanistic integration between cell-adhesion and EV biogenesis, 2) the consequences for cargo incorporated in motility-promoting EVs, and 3) the functional contribution to autocrine and paracrine communication. Moreover, the relevance of this biology will be tested in the context of bladder cancer where ALCAM shedding is an independent prognostic indicator of survival. For this purpose we have developed a novel ex vivo organotypic culture system for bladder urothelium and bladder cancer in which we can replicate the clinical phenotypes of both papilloma and carcinoma of the bladder. Considering that tumor cells have a large number of divergent mechanisms at their disposal by which they can enhance their malignant behavior, determining how mechanisms of cell adhesion and EV biogenesis integrate is not only an innovative way to deconvolve complex metastatic behavior, it will also have significant clinical impact. With findings from the propose studies, will provide novel avenues of intervention where a therapy may target a point of synergy and integration rather than a direct mode of action.