Inflammation induces myeloid-derived suppressor cells that facilitate tumor progression.
Epidemiological and experimental observations support the hypothesis that chronic inflammation contributes to cancer development and progression; however, the mechanisms underlying the relationship between inflammation and cancer are poorly understood. To study these mechanisms, we have transfected the mouse 4T1 mammary carcinoma with the proinflammatory cytokine IL-1beta to produce a chronic inflammatory microenvironment at the tumor site. Mice with 4T1/IL-1beta tumors have a decreased survival time and elevated levels of immature splenic Gr1+CD11b+ myeloid-derived cells. These myeloid suppressor cells (MSC) are present in many patients with cancer and inhibit the activation of CD4+ and CD8+ T lymphocytes. 4T1/IL-1beta-induced MSC do not express the IL-1R, suggesting that the cytokine does not directly activate MSC. Neither T or B cells nor NKT cells are involved in the IL-1beta-induced increase of MSC because RAG2-/- mice and nude mice with 4T1/IL-1beta tumors also have elevated MSC levels. MSC levels remain elevated in mice inoculated with 4T1/IL-1beta even after the primary tumor is surgically removed, indicating that the IL-1beta effect is long lived. Collectively, these findings suggest that inflammation promotes malignancy via proinflammatory cytokines, such as IL-1beta, which enhance immune suppression through the induction of MSC, thereby counteracting immune surveillance and allowing the outgrowth and proliferation of malignant cells.
Bunt
Stephanie K
SK
Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
Sinha
Pratima
P
Clements
Virginia K
VK
Leips
Jeff
J
Ostrand-Rosenberg
Suzanne
S
D000818:Animals; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D007249:Inflammation / Q000276:immunology* / Q000503:physiopathology; D007375:Interleukin-1 / Q000276:immunology / Q000378:metabolism*; D007694:Killer Cells, Natural / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D008325:Mammary Neoplasms, Experimental / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D022423:Myeloid Cells / Q000276:immunology*; D014162:Transfection
D007375:Interleukin-1