Exosomes secreted from human colon cancer cells influence the adhesion of neighboring metastatic cells: Role of microRNA-210.
Cancer-secreted exosomes influence tumor microenvironment and support cancer growth and metastasis. MiR-210 is frequently up-regulated in colorectal cancer tissues and correlates with metastatic disease. We investigated whether exosomes are actively released by HCT-8 colon cancer cells, the role of exosomal miR-210 in the cross-talk between primary cancer cells and neighboring metastatic cells and its contribution in regulating epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). After 7 d of culture, a subpopulation of viable HCT-8 cells detached the monolayer and started to grow in suspension, suggesting anoikis resistance and a metastatic potential. The expression of key proteins of EMT revealed that these cells were E-cadherin negative and vimentin positive further confirming their metastatic phenotype and the acquisition of anoikis resistance. Metastatic cells, in the presence of adherently growing HCT-8, continued to grow in suspension whereas only if seeded in cell-free wells, were able to adhere again and to form E-cadherin positive and vimentin negative new colonies, suggesting the occurrence of MET. The chemosensitivity to 5 fluorouracil and to FOLFOX-like treatment of metastatic cells was significantly diminished compared to adherent HCT-8 cells. Of note, adherent new colonies undergoing MET, were insensitive to both chemotherapeutic strategies. Electron microscopy analysis demonstrated that adherently growing HCT-8, actually secreted exosomes and that exosomes in turn were taken up by metastatic cells. When exosomes secreted by adherently growing HCT-8 were administered to metastatic cells, MET was significantly inhibited. miR-210 was significantly upregulated in exosomes compared to its intracellular levels in adherently growing HCT-8 cells and correlated to anoikis resistance and EMT markers. Exosomes containing miR-210 might be considered as EMT promoting signals that preserve the local cancer-growth permissive milieu and also guide metastatic cells to free, new sites of dissemination.
a Department of Neuroscience, Psychology , Drug Research and Child Health - NEUROFARBA - Section of Pharmacology and Toxicology, University of Florence , Florence , Italy.
Elisabetta
E
Bigagli
a Department of Neuroscience, Psychology , Drug Research and Child Health - NEUROFARBA - Section of Pharmacology and Toxicology, University of Florence , Florence , Italy.
Cristina
C
Luceri
b Department of Experimental and Clinical Medicine - Research Unit of Histology and Embryology , University of Florence , Florence , Italy.
Daniele
D
Guasti
a Department of Neuroscience, Psychology , Drug Research and Child Health - NEUROFARBA - Section of Pharmacology and Toxicology, University of Florence , Florence , Italy.
Lorenzo
L
Cinci
Colon cancer; EMT; MET; chemoresistance; exosomes; metastasis; miR-210