Differentiation affects the release of exosomes from colon cancer cells and their ability to modulate the behavior of recipient cells

Exosomes are involved in inter-cellular communication. We previously reported that sodium butyrate–induced differentiation of HT29 colon cancer cells is associated with a reduced CD133 expression. Here, we analyzed the role of exosomes in the differentiation of HT29 cells. Exosomes were prepared using ultracentrifugation. Gene expression levels were evaluated by real time-PCR. Cell proliferation rate was assessed by MTT assay and with the ECIS system whereas cell motility was assessed using the scratch test and confocal microscopy. Sodium butyrate–induced differentiation of HT29 and Caco-2 cells increased the levels of released exosomes and their expression of CD133. Cell differentiation and the decrease of cellular CD133 expression levels were prevented by blocking multivescicular body maturation. Exosomes released by HT29 differentiating cells carried increased levels of microRNAs, induced an increased proliferation and motility of both colon cancer cells and normal fibroblasts, increased the colony-forming efficiency of cancer cells, and reduced the sodium butyrate-induced differentiation of HT29 cells. Such effects were associated with an increased phosphorylation level of both Src and Erk proteins and with an increased expression of epithelial-to-mesenchymal transition–related genes. Release of exosomes is affected by differentiation of colon cancer cells; exosomes might be used by differentiating cells to get rid of components that are no longer necessary but might continue to exert their effects on recipient cells.