TNF-α secreted by myeloid cells in ascites regulate colorectal cancer

Abstract Background CD14 + macrophages within a tumor or in peripheral blood are cytotoxic to during the early stages but support cancer cell proliferation in the late stages. We investigated the role of inflammatory cells in ascites in colorectal cancer (CRC) patients. Methods We prospectively enrolled 18 consecutive CRC patients who required surgery and 5 patients (healthy donors) requiring inguinal hernia surgery. Inflammatory cells in the peritoneal fluid were enumerated using FACS. Demographic and clinical characteristic such as age, gender, peritoneal inflammatory CD14+, CD4+, CD8+, and CD19 + cells in ascites were compared between the two groups. The M1 (TNF-α iNOS CCR2) and M2 (ARG1 IL-10 TGF- β) characteristics of macrophages in ascites in cancer patients and those from the peripheral blood (PB) of healthy donors were investigated. HCT116 cells (colon cancer) were co-cultured with CD14 + from ascites and PB of CRC patients and with CD14 + macrophages from healthy donors. Results There were no significant differences in CD14 + cell numbers (mean, 5.5 vs. 10.1%) in the peritoneal fluid of the two groups, but TNF-α levels in CRC ascites macrophages were significantly higher than those from PB of healthy donors (p < 0.01). CD14 + cells from ascites of CRC patients better suppressed cancer cell proliferation (p < 0.01), but cancer cell proliferation persisted in the presence of TNF-α antibodies (p < 0.01). Conclusions Myeloid-derived CD14 + cells in the environment of ascites can infiltrate it in CRC patients, they appear to be M1 macrophages, and secreted TNF-α can suppress the growth of CRC cells.