It has been well stated that mature DCs preferentially attract Treg cells among circulating CD4+ T cells, by secretion of CCR4 ligands CCL17 and CCL22,62 and CCL17 and CCL22 chemokines within tumour microenvironment are related to the accumulation of Foxp3+ regulatory T cells in gastric cancer.63 This evidence concerns the gene CCL17 and gastric cancer.