Helios serves as a suppression marker to reduce regulatory T cell function in pancreatic cancer patients

Destabilizing and reprogramming regulatory T (Treg) cells have become a potential strategy to treat tumor. Mounting evidence indicates that the transcription factor Helios is required for the stable differentiation of Treg lineage. Hence, we investigated whether Helios suppression could be a potential treatment option for pancreatic cancer patients. We found that Helios⁺ cells were predominantly in Foxp3⁺ Treg cells. By contrast, Foxp3⁺ Treg cells can be Helios⁺ or Helios^-, but the level of Foxp3 expression was significantly higher in Helios⁺Foxp3⁺ Treg cells than in Helios^-Foxp3⁺ Treg cells. Resected pancreatic tumors were highly enriched with both Helios⁺Foxp3⁺ Treg cells and Helios^-Foxp3⁺ Treg cells. Also, the proportion of Helios⁺ cells in total Foxp3⁺ Treg cells was significantly higher in peripheral blood mononuclear cells (PBMCs) of patients than in PBMCs of healthy controls and further increased in patient tumors. Using shRNA, we knocked down Helios expression without significant downregulation of Foxp3. After Helios knockdown, CD4⁺CD25⁺CD127^- Treg cells presented significantly lower levels of TGF-β secretion, lower levels of IL-10 secretion, and higher levels of IFN-γ secretion. In addition, Helios shRNA-transfected CD4⁺CD25⁺CD127^- Treg cells presented lower capacity to inhibit CD4⁺CD25^-CD127⁺ T conventional cell proliferation than control shRNA-transfected CD4⁺CD25⁺CD127^- Treg cells. Of note, CD4⁺CD25⁺CD127^- Treg cells from pancreatic cancer patients demonstrated higher TGF-β expression and higher suppression capacity than the cells from healthy controls. Overall, these results suggest that in pancreatic cancer patients, Helios may serve as a candidate to suppress Treg function, which could be used as a target to treat pancreatic cancer.