Proteomic characterization of epithelial-like extracellular vesicles in advanced endometrial cancer.

Endometrial cancer (EC) is the most frequent gynecological cancer. Tumor dissemination affecting around 20% of EC patients is characterized at the primary carcinoma by epithelial-to-mesenchymal transition (EMT) associated with myometrial infiltration. At distant sites, the interaction of circulating tumor cells (CTCs) with the microenvironment results crucial for metastatic colonization, with a participation of the extracellular vesicles (EVs). We comprehensively approached these primary and secondary sites to study the impact of tumor EVs on the metastatic efficiency of CTCs in EC. Tumor EVs in circulation reproduce the epithelial phenotype predominant in the primary carcinoma, while CTCs are characterized by an EMT phenotype. We modelled this EMT-related clinical scenario in the Hec1A endometrial cell line and characterized the epithelial-like EVs in circulation by SILAC proteome analysis. Identification of proteins involved in cell-cell and cell-matrix interaction and binding, together with in vitro evidences of an improved adhesion of CTC to a functionalized endothelium suggest a contribution of the epithelial-like EVs in the homing of CTCs at metastatic sites. Accordingly, adhesion protein LGALS3BP was found significantly enriched in circulating EVs from a cohort of EC patients with high risk of recurrence by targeted proteomics (MRM), highlighting their potential as liquid biopsy in EC.