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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, R G Toedebusch1, B E Mclaughlin2
1University of California, Davis.
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 accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford targeting 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 model of glioma. 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 identification and isolation of 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 to 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, a model for human glioblastoma, shows increased C-C motif chemokine 2 (CCL2) that recruits immunosuppressive regulatory T cells (Tregs). Targeting the CCL2-CCR4 axis may offer new glioblastoma treatments.
Area of Science:
- Comparative oncology
- Immunology
- Neuro-oncology
Background:
- Canine glioma serves as a valuable translational model for human glioblastoma.
- Both conditions exhibit molecular similarities, including the accumulation of immunosuppressive regulatory T cells (Tregs).
- Understanding Treg recruitment mechanisms in dogs can inform human glioblastoma treatment strategies.
Purpose of the Study:
- To investigate the C-C motif chemokine 2 (CCL2) and chemokine receptor 4 (CCR4) signaling axis in canine glioma.
- To determine the role of this axis in regulatory T cell (Treg) recruitment and immunosuppression in canine glioma.
- To establish a rationale for targeting this pathway in translational clinical studies for human glioblastoma.
Main Methods:
- In vitro experiments using canine Tregs and patient-derived canine glioma cell lines.
- Development of a flow cytometry gating strategy to identify and isolate FOXP3+ Tregs.
- Assessment of canine Treg migration in response to CCL2 and glioma cell line supernatants, and the effect of CCL2-CCR4 axis blockade.
Main Results:
- Canine CD4+CD25high T cells were confirmed as Tregs based on FOXP3 and CCR4 expression.
- CCL2 significantly enhanced canine Treg migration, as did glioma cell line supernatants.
- Blockade of the CCL2-CCR4 axis markedly reduced canine Treg migration, and CCL2 expression was upregulated in glioma cells upon Treg co-culture.
Conclusions:
- The CCL2-CCR4 axis is validated as a bi-directional signaling pathway in canine high-grade glioma.
- This axis promotes immunosuppression and tumor growth by mediating Treg-glioma interactions.
- Findings support the CCL2-CCR4 axis as a potential therapeutic target for canine and human glioblastoma.
