Possible involvement of regulatory T cells in tumor onset and progression in primary breast cancer

The FOXP3 mRNA expression and the other regulatory T cell-related molecules were investigated and compared with clinicopathological parameters in human primary breast cancer. This study included 136 breast cancer patients operated in our department from 2003 to 2006. Total RNA was extracted from frozen normal breast and breast cancer tissues, and the expression of FOXP3, IL-10, TGF beta 1 and CCL22 mRNA was evaluated using quantitative real-time RT-PCR. FOXP3, IL-10, TGF beta 1 and CCL22 mRNA expressions were significantly higher in cancer tissue than in normal tissue, not only at pT1, 2, and 3 stages but also at the DCIS stage. There were positive correlations between FOXP3 and IL-10, FOXP3 and TGF beta 1, as well as FOXP3 and CCL22 mRNA expressions, respectively. FOXP3 and IL-10 mRNA expressions were significantly upregulated in PgR-negative or HER2-positive tumors. These results suggest that regulatory T cells are involved in tumor onset and progression in human primary breast cancer, possibly contributing to poor prognosis of patients with breast cancer.