Colorectal cancer cell-derived interleukin-6 enhances the phagocytic capacity and migration of THP-1 cells

• Effects of IL-6 secreted by colorectal cancer cells on THP-1 cells were evaluated.
• Colorectal cancer cell-secreted IL-6 enhanced THP-1 cell phagocytosis and migration.
• IL-6-induced macrophage migration and phagocytosis is mediated by STAT3 activation.

Macrophages perform a versatile range of functions in response to environmental stimuli. In the present study, we evaluated whether interleukin-6 (IL-6), a cytokine released from colorectal cancer (CRC) cells and associated with CRC pathogenesis and metastasis, modulates the phagocytic capacity and migratory ability of macrophages, using a monocyte-macrophage THP-1 cell model and human peripheral monocytes. We found that CRC cells enhanced the phagocytic capacity and migration of THP-1 cells and human peripheral monocytes. CRC cell culture supernatants and recombinant IL-6 neutralized with anti-IL-6 and anti-gp130 antibodies considerably decreased IL-6–mediated phagocytosis by and migration of THP-1 cells and human peripheral monocytes, via the phosphorylation of signal transducer and activator of transcription 3 (STAT3). Our data suggest that CRC cells secreting IL-6 via STAT3 phosphorylation can enhance the phagocytic capacity and migration of macrophages in the tumor microenvironment.