Inflammation-associated immune suppression in cancer: The roles played by cytokines, chemokines and additional mediators

Chronic inflammation and presence of inflammatory cells, primarily macrophages, at tumor sites are highly associated with specific malignancies. In these cases, the inflammatory milieu is overloaded with mediators that suppress immune activities at many levels: recognition of tumor-associated antigens, activation, the actual cytolysis of tumor cells and more. Local suppression of leukocyte functions at the inflammatory tumor site further contributes to profound immunosuppression of potential anti-tumor immune functions. The present review discusses the inflammatory setup in tumors and the factors inducing the presence of detrimental inflammatory macrophages at tumor sites. Moreover, the different mediators that contribute to inflammation-associated immune suppression, including primarily cytokines and chemokines but also prostaglandins and oxidants, are described. Bearing in mind the notion that under specific conditions the inflammatory mediators clearly contribute to malignancy, while in others they may exert surveillance missions against tumor cells, the potential therapeutic value of the inflammatory components is discussed.