Regulatory T cells that co-express RORγt and FOXP3 are pro-inflammatory and immunosuppressive and expand in human pancreatic cancer

ABSTRACT

Pancreatic ductal adenocarcinoma (PDAC) is highly infiltrated by CD4⁺T cells that express RORγt and IL-17 (T_H17). Compelling evidence from the tumor microenvironment suggest that regulatory T cells (T_reg) contribute to T_H17 mediated inflammation. Concurrently, PDAC patients have elevated levels of pro-inflammatory cytokines that may lead to T_H17 associated functional plasticity in T_reg. In this study, we investigated the phenotype and functional properties of T_reg in patients with PDAC. We report that PDAC patients have elevated frequency of FOXP3⁺T_reg, which exclusively occurred within the FOXP3⁺RORγt⁺T_reg compartment. The FOXP3⁺RORγt⁺T_reg retained FOXP3⁺T_reg markers and represented an activated subset. The expression of RORγt in T_reg may indicate a phenotypic switch toward T_H17 cells. However, the FOXP3⁺RORγt⁺T_reg produced both T_H17 and T_H2 associated pro-inflammatory cytokines, which corresponded with elevated T_H17 and T_H2 immune responses in PDAC patients. Both the FOXP3⁺T_reg and FOXP3⁺RORγt⁺T_reg from PDAC patients strongly suppressed T cell immune responses, but they had impaired anti-inflammatory properties. We conclude that FOXP3⁺RORγt⁺T_reg have a dual phenotype with combined pro-inflammatory and immunosuppressive activity, which may be involved in the pathogenesis of PDAC.

KEYWORDS:

• FOXP3
• plasticity
• RORγt
• regulatory T Cells
• suppression
• surface Markers
• Th2 cell
• Th17 cell

Acknowledgments

We thank Dr Arnold Kirshenbaum (Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA) for providing the LAD2 human mast cell line. We also thank the Oslo University Hospital Blood Center for providing healthy donor samples and Saranya Subramani (NCMM, University of Oslo) for spectrophotometry suggestions. This work was supported by the grants from the Research Council of Norway (221938, 204784 and 187615), the Norwegian Cancer Society (741746 and 419544), the KG Jebsen Foundation (2012/21 and 2012/23), and the South Eastern Norway Regional Health Authority (2010038).