Modulation of tumor-associated macrophages in colitis-associated colorectal cancer.

ABSTRACT

Intestinal macrophages are the most abundant immune cells in the small and large intestine, which maintain intestinal homeostasis by clearing invading bacteria and dead cells, secreting anti-inflammatory cytokines, and inducing tolerance to symbiotic bacteria and food particles. In addition, as antigen-presenting cells, they also participate in eliciting adaptive immune responses through bridging innate immune responses. After the intestinal homeostasis is disrupted, the damaged or apoptotic intestinal epithelial cells cannot be effectively cleared, and the infection of exogenous pathogens and leakage of endogenous antigens lead to persistent intestinal inflammation. Long-term chronic inflammation is one of the important causes of colitis-associated carcinogenesis (CAC). Tumor microenvironment (TME) is gradually formed around tumor cells, in which tumor associated macrophage (TAMs) is not only the builder, but also regulated by TME. This review just briefly summarized the role of intestinal macrophages under physiological and pathological inflammatory and cancerous conditions, and current therapeutic strategies for intestinal diseases targeting macrophages.