CCL17 and CCL22 chemokines within tumor microenvironment are related to accumulation of Foxp3⁺ regulatory T cells in gastric cancer

Abstract

It has been reported that an increased population of regulatory T cells (Tregs) is one of the reasons for impaired anti-tumor immunity. Recently, Foxp3 has been reported as a reliable marker of Tregs. The authors investigated the frequency of Foxp3 1 Tregs within CD4 1 cells in TILs, regional lymph nodes and PBLs of gastric cancer patients (n 5 45). Furthermore, to elucidate the mechanisms behind Treg accumulation within tumors, they evaluated the relationship between CCL17 or CCL22 expression and the frequency of Foxp3 1 Tregs in gastric cancer. CD4 1 CD25 1 Foxp3 1 Tregs as a percentage of CD4 1 cells were counted by flow cytometry and evaluated by immunohistochemistry. Moreover, an in vitro migration assay using Tregs derived from gastric cancers was performed in the presence of CCL17 or CCL22. As a result, the frequency of Foxp3 1 Tregs in TILs was significantly higher than that in normal gastric mucosa (12.4% 6 7.5% vs. 4.1% 6 5.3%, p < 0.01). Importantly, the increase in Tregs in TILs occurred to the same extent in early and advanced disease. Furthermore, the frequency of CCL17 1 or CCL22 1 cells among CD14 1 cells within tumors was significantly higher than that of normal gastric mucosa, and there was a significant correlation between the frequency of CCL17 1 or CCL22 1 cells and Foxp3 1 Tregs in TILs. In addition, the in vitro migration assay indicated that Tregs were significantly induced to migrate by CCL17 or CCL22. In conclusion, CCL17 and CCL22 within the tumor are related to the increased population of Foxp3 1 Tregs, with such an observation occurring in early gastric cancer. ' 2008 Wiley-Liss, Inc.Key words: CCL17; CCL22; Foxp3; regulatory T cells; gastric cancer It has been reported that regulatory T cells (T regs) play important roles in immunological self-tolerance, 1-4 and are functionally immune-suppressive subsets of T cells. T regs are identified as a small population of CD4 1 cells that constitutively express CD25 (IL-2 receptor a chain) on their surface, and several other markers, including CD45RO, glucocorticoid-induced tumor-necrosis factor receptor-related protein (GITR), or cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), are also known to be expressed on T regs. [3][4][5] Recently, it has been reported that Foxp3, forkhead/ winged helix transcription factor, is the most reliable marker of T regs 6,7 ; therefore, it is possible to define T regs more strictly as CD4 1 CD25 1 Foxp3 1 cells.In mice, it is known that auto-immune diseases such as ulcerative colitis or Crohn's disease occur due to the depletion of T regs. 6,8 Also in humans, immune dysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) is an auto-immune disease developed from a deficiency of T regs. [8][9][10][11] These observations indicate that T regs play important roles in immunological homeostasis. Although the mechanisms of suppression by T regs are still unclear, it has been reported that T regs can inhibit the function of effector T cells directly by cell to cell contact or indirectly via the se...

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