Identification and functional analysis of heterogeneous FOXP3+ Treg cell subpopulations in human pancreatic ductal adenocarcinoma

CD4+ CD25+ regulatory T (Treg) cells express the transcription factor FOXP3 and play an essential role in preventing autoimmunity. Abundant Treg cell accumulation in tumors and tumor draining lymph nodes (TDLNs) has been reported to correlate with both poor and favorable prognosis in various cancers, which suggests that Tregs may have multiple effects on antitumor immunity. However, the heterogeneity of tumor- and TDLN-infiltrating Treg cells remains unclear. Here we provide heterogeneity analysis of tumor infiltrating human CD4+ Treg cells and their matched adjacent tissues and TDLNs. We defined three different subpopulations of tumor- and TDLN-infiltrating Treg cells by Helios and CCR8 expression in pancreatic ductal adenocarcinoma (PDAC) and confirmed their functional heterogeneity. Helios+ CCR8+ Treg cells with potent suppressor function and limited IL-2 and IFN-γ secretion were identified in tumors and TDLNs. On the contrary, Helios− CCR8− Treg cells have impaired suppressive activity, and elevated expression of pro-inflammatory cytokines. More advanced grades of PDAC have predominantly Helios+ CCR8+ Treg cells and few Helios− CCR8− Treg cells both in tumors and TDLNs that suggests poor prognosis. These data could help further define the role of Treg cells and their functional role in tumors and TDLNs.