STAT6 controls the stability and suppressive function of regulatory T cells

Area of Science:

• Immunology
• Cancer Biology
• Molecular Biology

Background:

• Signal transducer and activator of transcription 6 (STAT6) is implicated in tumorigenesis by reducing regulatory T cell (Treg) frequency.
• STAT6 signaling may influence the development and function of Tregs in inflammatory conditions, particularly in colitis-associated cancer (CAC).

Purpose of the Study:

• To investigate the role of STAT6 in the generation and function of inducible Tregs (iTregs) in vitro and peripheral Tregs (pTregs) in vivo under inflammatory conditions.
• To determine how STAT6 deficiency affects Treg stability, suppressive capacity, and gene expression profiles in the context of gut inflammation and CAC.

Main Methods:

• In vitro assays to assess iTreg generation, stability, phenotype (Foxp3, CD25, PD-1, CTLA-4, IFN-γ), and suppressive function in STAT6-deficient conditions.
• Analysis of FOXP3 Treg-specific demethylated region (TSDR) demethylation status and DNA methyltransferase 1 (DNMT1) mRNA expression in iTregs.
• Utilizing a mouse model of CAC to evaluate the phenotype, suppressive capacity, and expression of PD-1 and latency-associated peptide of TGF-β (LAP) in STAT6-/- pTregs within the intestine.

Main Results:

• STAT6 deficiency led to stable iTregs with high Foxp3 and CD25 expression, enhanced suppressive ability, increased PD-1 and CTLA-4, and decreased IFN-γ.
• STAT6-deficient iTregs exhibited increased FOXP3 TSDR demethylation and reduced DNMT1 mRNA expression, suggesting STAT6 promotes Foxp3 silencing.
• In a CAC model, STAT6-/- pTregs showed an activated phenotype, higher suppressive capacity, and increased PD-1 and LAP expression, correlating with attenuated tumor development.

Conclusions:

• STAT6 signaling negatively impacts the induction, stability, and suppressive function of Tregs in both in vitro and in vivo settings during gut inflammation.
• Targeting STAT6 may represent a therapeutic strategy to enhance Treg-mediated immune suppression and control tumor development in colitis-associated cancer.