Abstract: Objective To investigate the function of colon cancer cell-derived exosomes in between neutrophils and colon cancer cells and its possible mechanism. Methods The neutrophils and colon cancer cells SW480 were cultured in vitro. The SW480 cells were transfected with sh-NC and sh-HMGB1, respectively, and the exosomes SW480-exo, sh-NC-exo, and sh-HMGB1-exo were isolated. Neutrophils were treated with exosomes in each group, and a PBS group was set at the same time. The neutrophil supernatant was extracted from each group, then co-cultured with SW480 cells, which were recorded as SW480-exo+Neutrophils group, sh-NC-exo+Neutrophils group, sh-HMGB1-exo+Neutrophils group and PBS+Neutrophils group, respectively. Sytox green staining was used to detect the formation of neutrophil extracellular traps(NETs); Western blot was used to detect the expression of HMGB1 protein; CCK-8 was used to detect the cell viability; Clone formation experiment was used to detect the cell proliferation; Transwell assay was used to detect the migration and invasion of cells. Results The HMGB1 knockdown colon cancer cell model was successfully constructed and SW480-exo, sh-NC-exo and sh-HMGB1-exo were isolated. Compared with the PBS group, the neutrophil Sytox green fluorescence unit and the expression of HMGB1 protein in the SW480-exo group were significantly increased (all P<0.05). Compared with the sh-NC-exo group, there was no significant difference in HMGB1 protein expression and Sytox green fluorescence unit in neutrophils in the SW480-exo group (all P>0.05), but HMGB1 protein expression and Sytox green fluorescence unit in the sh-HMGB1-exo group were significantly decreased (all P<0.05). Compared with the the PBS+Neutrophils group, the SW480 cells viability, the number of colonies, the number of migrating cells and the number of invasive cells in the SW480-exo+Neutrophils group were significantly increased(all P<0.05), but there was no significant difference compared with the sh-NC-exo+Neutrophils group (all P>0.05). Compared with the sh-NC-exo+Neutrophils group, the SW480 cells viability, the number of colonies, the number of migrating cells and the number of invasive cells in the sh-HMGB1-exo+Neutrophils group were significantly reduced (all P<0.05). Conclusions The colon cancer cell-derived exosomes may induce the formation of neutrophil NETs through HMGB1, thereby promoting the proliferation, migration and invasion of colon cancer cells.

Key words: Colon cancer, Exosomes, High mobility group protein 1, Neutrophils, Neutrophil extracellular traps