Expression of Chemokine Receptor CXCR6 in Human Colorectal Adenocarcinomas

Abstract

Infiltration of inflammatory cells into colorectal adenocarcinomas is considered of importance for tumour progression. Tumour-associated macrophages and T cells are predominant components of the chemokine-guided filtrate of most colorectal tumours. CXCR6 is a chemokine receptor expressed by Th1, Tc, NKT cells and smooth muscle cells. To determine whether CXCR6 is expressed in human colorectal cancer and corresponding normal tissue, we analysed CXCR6 protein expression in 32 surgical specimens. Immunohistochemistry revealed CXCR6 protein predominantly localised in normal epithelial cells and some scattered stromal cells. No or weak expression was found in cancerous tissue. Western blot analysis showed, in 41 % of the cases, a notable suppression of CXCR6 protein (p<0.05) in cancerous tissue compared with non-cancerous tissue. Up-regulation was found in 9% of the cases. CXCR6 protein expression, in 25% of the cases, showed no difference between tumour and adjacent normal tissue. Furthermore, 25% of the cases revealed undetectable levels of CXCR6 protein in tumour as well as corresponding normal tissue. The results may reflect one of the immunological features of normal and cancerous colorectal tissue and studies on regulation of CXCR6 are necessary in order to determine its role in colorectal carcinogenesis.