Foxp3 expression in CD4+CD25+Foxp3+ regulatory T cells promotes development of colorectal cancer by inhibiting tumor immunity

The mechanism underlying CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) promoting the development of colorectal cancer (CRC) was elucidated in the present study. Forty-eight cases of colorectal carcinomas, 22 cases of colon polyps and 21 cases of normal colorectal tissues were collected. The correlation among Foxp3, IL-10 and Stat3, and the clinical relevance of these three indexes were analyzed. The results showed that the levels of Foxp3 expressed in infiltrating CD4⁺CD25⁺Foxp3⁺Tregs, and IL-10 and Stat3 in CRC tissues were all significantly higher than those in polypus tissues and normal colon tissues (P< 0.01). Pearson correlation analysis indicated that the expression level of Foxp3 was positively correlated with Stat3 at mRNA level (r=0.526, P=0.036), and was positively correlated with IL-10 at protein level (r=0.314, P=0.030). The Foxp3 expressed in CD4⁺CD25⁺Foxp3⁺Tregs was correlated with the histological grade, lymph node metastasis and TNM stage of CRC (P<0.05 for all). The IL-10 expression was correlated with the histological grade and TNM stage (both P<0.05). The Stat3 expression was correlated with the lymph node metastasis and TNM stage (both P<0.05). It was concluded that CD4⁺CD25⁺Foxp3⁺Tregs can inhibit tumor immunity in combination with some other related inhibitory cytokines and that Foxp3 expression in CD4⁺CD25⁺Foxp3⁺Tregs correlates with CRC progression.