Inflammation, Microenvironment, and the Immune System in Cancer Progression

Since Virchow first proposed in 1863 that tumors could originate from sites of chronic inflammation, it has been well established that chronic inflammation both contributes to cancer progression and predisposes tissue to various types of cancer. Experimental, clinical, and epidemiological studies have all demonstrated the strong association between chronic inflammation and cancer, and many studies have correlated the prolonged presence of the inflammatory milieu with an increased risk for developing cancer. Proinflammatory cytokines, chemokines and adhesion molecules, which regulate the sequential recruitment of leukocytes, are frequently observed in tumor microenvironment. These early desmoplastic changes could stimulate fibroblasts and endothelial cell division and produce components for tissue remodeling and neovascularization, ultimately promoting neoplastic processes. In this review article we overview the current understanding of the role of chronic inflammation in neoangiogenesis, tumor initiation, promotion, and progression.