Abstract
Regulatory T (Treg) cells are often found in human tumors; however, their functional characteristics have been difficult to evaluate due to low cell numbers and the inability to adequately distinguish between activated and Treg cell populations. Using a novel approach, we examined the intracellular cytokine production capacity of tumor-infiltrating T cells in the single-cell suspensions of enzymatically digested tumors to differentiate Treg cells from effector T cells. Similar to Treg cells in the peripheral blood of healthy individuals, tumor-infiltrating FOXP3+CD4 T cells, unlike FOXP3− T cells, were unable to produce IL-2 and IFN-γ upon ex vivo stimulation, indicating that FOXP3 expression is a valid biological marker for human Treg cells even in the tumor microenvironment. Accordingly, we enumerated FOXP3+CD4 Treg cells in intratumoral and peritumoral sections of metastatic melanoma tumors and found a significant increase in proportion of FOXP3+CD4 Treg cells in the intratumoral compared with peritumoral areas. Moreover, their frequencies were 3- to 5-fold higher in tumors than in peripheral blood from the same patients or healthy donors, respectively. These findings demonstrate that the tumor-infiltrating CD4 Treg cell population is accurately depicted by FOXP3 expression, they selectively accumulate in tumors, and their frequency in peripheral blood does not properly reflect tumor microenvironment.
Elevated neutrophil and monocyte counts in peripheral blood are associated with poor survival in patients with metastatic melanoma: a prognostic model
