Peritoneal cavity-derived small extracellular vesicles from aged tumor-naïve hosts promote ovarian cancer adhesion and invasion.

BACKGROUND: Epithelial ovarian cancer (OvCa) remains a leading cause of mortality among gynecological cancers. Metastasis to the peritoneum, characterized by tumor cell adhesion to and invasion of the mesothelial lining of the abdominal cavity, represents a critical early event in OvCa metastatic progression. The median age of diagnosis is 63 and there exists a strong correlation between advanced age, OvCa incidence and disease stage. Moreover, the aged peritoneal cavity represents a permissive niche for metastatic dissemination. METHODS: To investigate age-related factors that influence host-tumor communication in metastatic progression, the current study isolated small extracellular vesicles (sEVs) from the peritoneal lavage of healthy tumor-naïve young (3-6 month) and aged (20-22 month) mice. sEVs were analyzed using LC-MS/MS to identify sEV protein cargoes and incubated with murine and human OvCa cells to evaluate effect on pro-metastatic behaviors. RESULTS: Treatment of human or murine OvCa cells with sEVs from healthy aged hosts significantly enhanced adhesion to peritoneal mesothelial cells in a three-dimensional in vitro meso-mimetic culture assay and to the intact omentum in a short-term in vivo adhesion assay relative to OvCa cells treated with sEVs from young hosts. OvCa cell invasion of collagen gels was also enhanced by aged host-derived sEVs. Proteomic analysis of sEV protein cargos identified differentially expressed proteins in sEVs obtained from aged vs. young hosts that may play a significant role in regulation of adhesion. This was confirmed using meso-mimetic adhesion assays with function blocking antibodies or small molecule inhibitors, supporting a potential role for several proteins in promoting intra-peritoneal dissemination in the aged host. CONCLUSIONS: Results suggest that sEVs derived from the aged peritoneal microenvironment can contribute significantly to disease progression, highlighting sEV-mediated host: tumor communication as a potential therapeutic target for intervention in OvCa progression or recurrence in the aged host.