The role of IL-17 in modulation of antitumour immunity and progression of colitis-associated cancer

Colorectal carcinoma is one of the most frequent malignancies worldwide. There is a strong belief that it is initiated in the inflammatory bowel disease microenvironment. Pro-inflammatory cytokines produced by malignant cells as well as by tumor infiltrating leukocytes facilitate origination, growth and progression of cancer. An important role of T cells in antitumor immunity is well established. CD4+ Th lymphocytes can be classified into a few functional phenotypes: T helper 1 (Th1), T helper 2 (Th2), T helper 17 (Th17), according to the ability to secrete different cytokines. Th1 lymphocytes play important role in induction of cellular immunity, while Th2 lymphocytes suppress cellular immunity and enhance humoral immune response. Th17 lymphocytes are the key players in inducing inflammation by recruitment of neutrophils and macrophages. The polarization of T-mediated immune response has multiple effects on tumor progression. Although Th2-type cytokines can induce acute tumor rejection, Th1- type cytokines provide a greater antitumor effect and can promote durable anti-tumor CD8+T cell response. However, the role of IL-17 in pathogenesis of colitis-associated cancer (CAC) has not been fully understood. The aim of this paper is to clarify the role of IL-17 in modulation of antitumor immunity and progression of colorectal carcinoma