Notch Signaling Regulates the Secretion of Pro-Metastatic Factors in Extracellular Vesicles in Liposarcoma

Notch signaling is an emerging regulator of liposarcoma (LPS), but its role in mediating communication with the tumor microenvironment (TME) is unclear. Here, we investigate how Notch activation (NICD overexpression) alters the proteomes of LPS-derived extracellular vesicles (EVs). We used quantitative mass spectrometry to profile the EV proteome in multiple contexts: cultured LPS cells, LPS tumor, circulating EVs of LPS-bearing mice, and human LPS samples. We found that Notch signaling increases the secretion of EV proteins that favor tumor progression and metastasis but suppresses immune responses in murine LPS cells. Overlapping murine and human LPS data identifies 18 proteins that are increased in LPS EVs of both species, including endotrophin as a biomarker of LPS. Functional analysis supports a role of LPS EVs in regulating gene expression and behaviors of endothelial cells in TME. Together, these data demonstrate that in addition to its known function in driving tumorigenesis, Notch signaling also regulates TME through EV secretion.