The Mechanism of the Development of Macrophage Tolerance in Tumor Microenvironment

Bacteria forming the resident microbiome of the tumor are an integral component of its microenvironment. The interaction of the tumor microbiome with the tumor or tumor stromal cells is not well understood. We hypothesized that bacteria in the tumor microenvironment induce macrophage tolerance. Macrophage tolerance is a phenomenon of macrophage inability to respond to a repetitive inflammatory stimulus, which leads to a loss of cytotoxic activity. We studied the development of macrophage tolerance under the influence of bacteria and cytokines of the tumor microenvironment in vitro. It was found that the macrophage tolerance in the tumor stroma can develop in response to bacterial cell wall components and inflammatory factors. The acquired tolerance is inability of macrophages to produce proinflammatory cytokines TNFα, IL-1β, and MCP-1 and activation of the production of immunosuppressive IL-10.