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Published on: September 1, 2018
The CCL2-CCR4 axis promotes Regulatory T cell trafficking to canine glioma tissues
W K Panek1,2, R G Toedebusch3, B E Mclaughlin4
1Department of Surgical and Radiological Sciences, University of California, Davis, One Shields Avenue, 2112 Tupper Hall, Davis, CA, 95616-5270, USA. wkp@upenn.edu.
Purpose:
Spontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high-grade glioma and human glioblastomas share many molecular similarities, including the accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford to target the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic glioma model. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.
Methods:
We performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.
Results:
We established a flow cytometry gating strategy for identifying and isolating FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines, and expression increased when exposed to Tregs but not CD4 + helper T-cells.
Conclusion:
Our study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma.
Insights
Canine glioma research reveals the CCL2-CCR4 signaling pathway drives immunosuppressive regulatory T cells (Tregs) into tumors. Targeting this axis may offer new glioblastoma treatments in dogs and humans.
Area of Science:
- Comparative oncology
- Immunology
- Molecular biology
Background:
- Spontaneously occurring canine gliomas serve as a translational model for human glioblastoma.
- Both canine high-grade glioma and human glioblastomas exhibit immunosuppressive regulatory T cells (Tregs) that hinder anti-tumor immune responses.
- Understanding Treg recruitment mechanisms in dogs can inform targeted therapies for immunosuppression in human glioblastoma.
Purpose of the Study:
- To investigate the role of C-C motif chemokine 2 (CCL2) and its receptor CCR4 in canine Treg recruitment to gliomas.
- To validate the CCL2-CCR4 signaling axis as a target for modulating the tumor microenvironment in canine high-grade glioma.
Main Methods:
- In vitro experiments utilizing canine Tregs and patient-derived canine glioma cell lines.
- Flow cytometry to identify and isolate FOXP3+ Tregs.
- Assessment of canine Treg migration in response to CCL2 and glioma cell line supernatants.
- Evaluation of the CCL2-CCR4 axis blockade on Treg migration.
- Analysis of CCL2 mRNA expression in glioma cells and its modulation by T cells.
Main Results:
- A reliable flow cytometry strategy was established for canine FOXP3+ Tregs.
- Canine CD4+CD25high T cells were confirmed as Tregs expressing FOXP3 and CCR4.
- CCL2 significantly enhanced canine Treg migration, a process inhibited by CCL2-CCR4 axis blockade.
- Glioma cell lines expressed CCL2 mRNA, with increased expression upon co-culture with Tregs.
- A bi-directional interaction was observed where Tregs also influenced glioma cell CCL2 expression.
Conclusions:
- The study confirms CCL2-CCR4 signaling as a critical axis in canine high-grade glioma.
- This axis mediates a bi-directional immunosuppressive and tumor-promoting interaction between Tregs and glioma cells.
- Findings provide a strong rationale for targeting the CCL2-CCR4 pathway in canine and human glioma therapies.
