IL-17A in the tumor microenvironment of the human colorectal adenoma-carcinoma sequence

Objectives. Interleukin (IL)-17A is an important pro-inflammatory cytokine and involved in the colorectal carcinogenesis. In this study, the authors evaluated the dynamic change of IL-17A expression in the tumor microenvironment throughout the colorectal adenoma-carcinoma sequence. Materials & methods. Using quantitative real-time PCR (polymerase chain reaction) and semi-quantitative immunohistochemistry, the authors examined the expression level of IL-17A in 50 of human colorectal adenoma tissues, 50 of colorectal cancer (CRC) tissues and 15 controls. The relationship between IL-17A expression and clinicopathological parameters throughout the sequence was also evaluated. Results. The results revealed a step-up increased IL-17A mRNA level throughout the colorectal adenoma-carcinoma sequence, which began to increase in the adenomas and became even higher in the CRCs; notably, the increase of IL-17A mRNA level in the adenomatous tissues was associated with the severity of dysplasia. Immunohistochemical analysis confirmed the real-time PCR results and revealed gradually increasing IL-17A cells in both the stroma and adenomatous/cancerous epithelium. In addition, the quantitative real-time PCR result has also revealed an increased expression of TH17-stimulating factors throughout the sequence. Conclusions. IL-17A and TH17 are highly activated throughout the colorectal adenoma-carcinoma sequence.