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Author Spotlight: Achieving High-Purity In Vitro Differentiation of Th17 Cells Using Cytokine Concentration Modulation
Published on: October 25, 2024
The differentiation and plasticity of Tc17 cells are regulated by CTLA-4-mediated effects on STATs
Aditya Arra1, Holger Lingel1, Benno Kuropka2
1Department of Pediatrics, University Hospital, Health Campus Immunology, Infectiology and Inflammation, Otto-von-Guericke-University , Magdeburg, Germany.
Abstract:
As the blockade of inhibitory surface-molecules such as CTLA-4 on T cells has led to recent advances in antitumor immune therapy, there is great interest in identifying novel mechanisms of action of CD8+ T cells to evoke effective cytotoxic antitumor responses. Using in vitro and in vivo models, we investigated the molecular pathways underlying the CTLA-4-mediated differentiation of IL-17-producing CD8+ T cells (Tc17 cells) that strongly impairs cytotoxicity. Our studies demonstrate that Tc17 cells lacking CTLA-4 signaling have limited production of STAT3-target gene products such as IL-17, IL-21, IL-23R and RORγt. Upon re-stimulation with IL-12, these cells display fast downregulation of Tc17 hallmarks and acquire Tc1 characteristics such as IFNγ and TNF-α co-expression, which is known to correlate with tumor control. Indeed, upon adoptive transfer, these cells were highly efficient in the antigen-specific rejection of established OVA-expressing B16 melanoma in vivo. Mechanistically, in primary and re-stimulated Tc17 cells, STAT3 binding to the IL-17 promoter was strongly augmented by CTLA-4, associated with less binding of STAT5 and reduced relative activation of STAT1 which is known to block STAT3 activity. Inhibiting CTLA-4-induced STAT3 activity reverses enhancement of signature Tc17 gene products, rendering Tc17 cells susceptible to conversion to Tc1-like cells with enhanced cytotoxic potential. Thus, CTLA-4 critically shapes the characteristics of Tc17 cells by regulating relative STAT3 activation, which provides new perspectives to enhance cytotoxicity of antitumor responses.
Insights
Blocking CTLA-4 signaling in CD8+ T cells (Tc17 cells) limits IL-17 production and enhances their cytotoxic potential. This promotes conversion to Tc1-like cells, improving antitumor immune responses against melanoma.
Area of Science:
- Immunology
- Cancer Biology
- Molecular Biology
Background:
- Cytotoxic T-Lymphocyte-Associated protein 4 (CTLA-4) blockade is a key strategy in antitumor immunotherapy.
- CD8+ T cells play a crucial role in mediating cytotoxic antitumor responses.
- IL-17-producing CD8+ T cells (Tc17 cells) can impair anti-tumor immunity.
Purpose of the Study:
- To investigate the molecular mechanisms by which CTLA-4 signaling influences Tc17 cell differentiation and function.
- To determine if modulating CTLA-4 signaling can enhance the cytotoxic potential of CD8+ T cells for cancer therapy.
Main Methods:
- Utilized in vitro and in vivo models to study CTLA-4's role in Tc17 cell differentiation.
- Analyzed STAT3 target gene expression and STAT protein binding to gene promoters.
- Performed adoptive transfer of modified T cells in a B16 melanoma model.
Main Results:
- CTLA-4 signaling is essential for robust production of Tc17 signature genes (IL-17, IL-21, IL-23R, RORγt) via STAT3 activation.
- Inhibition of CTLA-4 signaling in Tc17 cells led to reduced Tc17 markers and acquisition of Tc1 markers (IFNγ, TNF-α) upon IL-12 stimulation.
- Adoptive transfer of CTLA-4-modulated T cells demonstrated efficient antigen-specific rejection of established melanoma in vivo.
- Mechanistically, CTLA-4 enhances STAT3 binding to the IL-17 promoter, suppressing STAT1 activity.
Conclusions:
- CTLA-4 critically regulates STAT3 activity, thereby shaping Tc17 cell characteristics and impairing their cytotoxic potential.
- Inhibiting CTLA-4-induced STAT3 activity converts Tc17 cells into potent Tc1-like cytotoxic cells.
- Targeting CTLA-4 signaling offers a novel strategy to enhance CD8+ T cell-mediated antitumor immunity.
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