FOXP3 and breast cancer: Briefly, BC patients at an advanced T stage showed a notably higher number of Foxp3+ Tregs and an increased S1P1 level in the tumor microenvironment (P = 0.002 and 0.008, Table 1), whereas no significant correlations were observed between the density of Foxp3+ Tregs or S1P1 expression and the other clinical parameters, including N stage, M stage, grade stage or treatment model (P > 0.05).