Mononuclear cells phagocytic activity affects the crosstalk between immune and cancer cells

The "professional phagocytes", i.e. monocytes and macrophages, play an important role as eliminators of pathogens and as essential components of the immune system. It is well established that monocytes induced for phagocytosis by various stimulators, produce cytokines that are closely related to inflammation. Considering the role of inflammation in carcinogenesis and the existence of an immune dialog between mononuclear and cancer cells, the aim of the present work was to examine cytokine production by immune cells stimulated for phagocytosis by latex particles and incubated with cells from HT-29 and RKO human cancer lines. Human peripheral blood mononuclear cells (PBMC) were incubated with various numbers of polysterene latex beads, 0.8. μm in diameter and the secretion of the following cytokines: TNF-α, IL-1β and IL-6, IL-10 and IL-1ra was examined before and after further incubation with cells of the both cancer lines. Phagocytosis of latex beads by PBMC caused an increased production of TNF-α, IL-1β and IL-10, whereas that of IL-6 declined. PBMC activated by latex beads and co-cultured with cancer cells generated lesser amount of the three pro-inflammatory cytokines TNF-α, IL-1β and IL-6, while that of the anti-inflammatory IL-10 and IL-1ra remained unchanged. The results indicate that phagocytosis of polystyrene latex beads by human PBMC alters the dialogue between immune and cells of human colon carcinoma lines, an observation that may clarify the role of the immune cells in attenuating inflammation and restraining carcinogenesis.