The αvβ6 integrin in cancer cell-derived small extracellular vesicles enhances angiogenesis.

Prostate cancer (PrCa) cells crosstalk with the tumour microenvironment by releasing small extracellular vesicles (sEVs). sEVs, as well as large extracellular vesicles (LEVs), isolated via iodixanol density gradients from PrCa cell culture media, express the epithelial-specific alpha v beta 6 integrin, which is known to be induced in cancer. In this study, we show sEV-mediated protein transfer of alpha v beta 6 integrin to microvascular endothelial cells (human microvascular endothelial cells 1 - HMEC1) and demonstrate that de novo alpha v beta 6 integrin expression is not caused by increased mRNA levels. Incubation of HMEC1 with sEVs isolated from PrCa PC3 cells that express the alpha v beta 6 integrin results in a highly significant increase in the number of nodes, junctions and tubules. In contrast, incubation of HMEC1 with sEVs isolated from beta 6 negative PC3 cells, generated by shRNA against beta 6, results in a reduction in the number of nodes, junctions and tubules, a decrease in survivin levels and an increase in a negative regulator of angiogenesis, pSTAT1. Furthermore, treatment of HMEC1 with sEVs generated by CRISPR/Cas9-mediated down-regulation of beta 6, causes up-regulation of pSTAT1. Overall, our findings suggest that alpha v beta 6 integrin in cancer sEVs regulates angiogenesis during PrCa progression.