Quantification of the chemokines CCL17 and CCL22 in human colorectal adenocarcinomas

Abstract

Chemokines are believed to play a crucial role in local immunoresponse by regulating leukocyte movement in various tissues, including the intestinal mucosa. It has been suggested that they are key players in cancer biology, and several studies have identified leukocyte infiltration as a hallmark of most cancers. The chemokines CCL17 and CCL22 attract CCR4-bearing cells, which are especially polarised to Th2-type cells and regulatory T cells (Treg). Recent studies have revealed the participation of the CCL17 and CCL22 proteins in diseases such as atopic dermatitis and lymphoma. The purpose of this study was to assess the role of CCL17 and CCL22 protein expression in colorectal cancer (CRC) and to ascertain whether an association exists between promoter -431C>T CCL17 and -961G>A CCL22 gene polymorphisms in CRC versus non-CRC subjects. Using the ELISA assay, we noted a significantly higher expression of CCL22 in tumour tissue with a 2.3-fold up-regulation (tumour vs. paired normal tissue, n=78) but no significant difference in CCL17 protein expression. Immunohistochemistry revealed protein expression of CCL22 and CCL17 in the epithelial compartment of cancer tissue, in epithelial cells at the resection border that reflects normal tissue, and in some stromal cells such as lymphocytes, macrophages, and fibroblasts. Using a TaqMan system we screened for -431C>T CCL17 and -961G>A CCL22 gene variants in 245 CRC patients and 256 controls, but could not find any significant difference in genotype distribution or in allelic frequencies between the two groups. The genotype and allelic distributions of CRC patients were not related to tissue levels of CCL17 and CCL22 protein, and none of the variables were associated with plasma levels or clinical characteristics. To ascertain whether the tissue expression of CCL17 and CCL22 exerts an influence on the pathogenesis of CRC, a forthcoming study on the 5-year survival rate of CRC patients will be conducted.