We observed that mean concentration of E2 was ~2 to 3-fold higher in tumour-derived Treg cells (294.4 pg/105 cells) when compared with CD4+ effector T-cells (Teff cells) (97.3 pg/105 cells), CD8+ effector T-cells (138 pg/105 cells), or peripheral blood naïve T cells (94.9 pg/105 cells) (n = 20, P < 0.0001; Fig. 2B). This evidence concerns the gene CD8A and neoplasm.