Interestingly, in gastric cancer, CCL22 and CCL17 seem both important to recruit TReg cells to the tumors as demonstrated by in vivo study as well as in vitro migration assay, and the levels of CCL22 and CCL17 within tumors are correlated to the increased levels of TReg cells in early gastric cancer [33]. This evidence concerns the gene CCL17 and gastric cancer.