Background:Regulatory T (Treg) cells are immunosuppressor lymphocytes that play a critical role in the establishment and progression of cancers. A number of markers, especially FOXP3, CTLA-4 and GITR influence the function of Treg cells. This investigation aimed to evaluate the expression of a number of important Treg cell-related markers by peripheral blood mononuclear cells (PBMCs) from newly-diagnosed women with breast cancer.Methods:The fresh PBMCs were obtained from 20 women with breast cancer and 20 healthy individuals. The PBMCs from both groups were cultured for 32 hours in the presence or absence of PHA (10 μg/ml). After total RNA extraction from cultured PBMCs, the expression of the FOXP3, CTLA-4 and GITR transcripts was assessed using real time-PCR.Results:The mRNA expression of FOXP3, CTLA-4 and GITR in unstimulated PBMCs from patients with breast cancer were significantly higher than healthy control group (P<0.05, P<0.03 and P<0.04, respectively). Similarly, the expression of FOXP3, CTLA-4 and GITR transcripts in PHA-stimulated PBMCs from patients with breast cancer were significantly increased in comparison with healthy individuals (P<0.01, P<0.005 and P<0.01, respectively).Conclusion:The increased expression of FOXP3, CTLA-4 and GITR represent higher activity of Treg cells in patients with breast cancer that may play an important role in the tumor establishment and development.