Suppression of Metastasis of Colon Cancer to Liver in Mouse Models by Pretreatment with Extracellular Vesicles Derived from Nanog-Overexpressing Colon-26 Cancer Cells

It has been demonstrated that cancer cells that have survived cancer treatment may be more malignant than the original cancer cells. These cells are considered the main cause of metastasis in prognosis. A <i>Nanog</i>-overexpressing colon-26 (<i>Nanog</i>⁺colon26) was generated to obtain such a malignant cancer cell model, which was confirmed by enhancement of metastatic potential by in vivo tests using mice. Extracellular vesicles (EVs) secreted from <i>Nanog</i>⁺colon26 cells (<i>Nanog</i>⁺colon26EVs) were administered to mice three times per week for three weeks. Subsequently, <i>Nanog</i>⁺colon26 cells were administered, and metastatic colonies were analyzed two weeks later. The results demonstrated that the administration of EVs suppressed metastasis. <i>Nanog</i>⁺colon26EVs enhanced phagocytic activity and M1 marker CD80 of a macrophage cell line J774.1. These suggested the enforcement of tumor-suppressive properties of macrophages and their contribution to the in vivo suppression of metastasis. Small RNA sequencing was conducted to identify <i>Nanog</i>-dependent miRNAs that exhibited significant changes (Fc ≥ 1.5 or Fc ≤ 1/1.5; <i>p</i> < 0.05) in <i>Nanog</i>⁺colon26EVs relative to colon26EVs. Nine miRNAs (up-regulated: four, down-regulated: five) were identified, and 623 genes were predicted to be their target genes. Of the 623 genes identified, nine genes were predicted to be highly relevant to macrophage functions such as phagocytosis.