Expression of FOXP3 in Canine Gliomas: Immunohistochemical Study of Tumor-Infiltrating Regulatory Lymphocytes

Abstract

Dogs develop gliomas with similar histopathological features to human gliomas and share with them the limited success of current therapeutic regimens such as surgery and radiation. The tumor microenvironment in gliomas is influenced by immune cell infiltrates. The present study aims to immunohistochemically characterize the tumor-infiltrating lymphocyte (TIL) population of naturally occurring canine gliomas, focusing on the expression of Forkhead box P3-positive (FOXP3+) regulatory T-cells (Tregs). Forty-three canine gliomas were evaluated immunohistochemically for the presence of CD3+, FOXP3+, and CD20+ TILs. In low-grade gliomas, CD3+ TILs were found exclusively within the tumor tissue. In high-grade gliomas, they were present in significantly higher numbers throughout the tumor and in the brain-tumor junction. CD20+ TILs were rarely found in comparison to CD3+ TILs. FOXP3+ TILs shared a similar distribution with CD3+ TILs. The accumulation of FOXP3+ Tregs within the tumor was more pronounced in astrocytic gliomas than in tumors of oligodendroglial lineage and the difference in expression was significant when comparing low-grade oligodendrogliomas and high-grade astrocytomas. Only high-grade astrocytomas presented FOXP3+ cells with tumoral morphology. In spontaneous canine gliomas, TILs display similar characteristics (density and distribution) as described for human gliomas, supporting the use of the dog as an animal model for translational immunotherapeutic studies.

Immunohistochemical evaluation of immune cell infiltration in canine gliomas

“…This study is the largest and most comprehensive characterization of inflammatory infiltrates in canine glioma to date, adding to the few previous studies in the dog. 1,18,55,63 In this study, we found robust infiltration of Iba1þ microglia and macrophages into gliomas, with smaller numbers of CD3þ and CD20þ lymphocytes. FoxP3þ cells were found in all cases but were more numerous in high-grade tumors.…”

Safety and interim survival data after intracranial administration of M032, a genetically engineered oncolytic HSV-1 expressing IL-12, in pet dogs with sporadic gliomas

“…35,36 Prior studies have demonstrated elevated numbers of CD4+ Foxp3+ regulatory T cells intratumorally and in the peripheral blood of dogs with gliomas, as well as an increased proportion of plasmacytoid dendritic cells. 29,37 In humans, the IDO pathway has been shown to play an important role in plasmacytoid dendritic cell-induced Foxp3+ regulatory T-cell differentiation. 38 Forthcoming immunohistochemical analyses of our tumor specimens will allow us to validate the importance of IDO expression in canine gliomas.…”

Immune Checkpoint-Associated Locations of Diffuse Gliomas Comparing Pediatric With Adult Patients Based on Voxel-Wise Analysis

“…The expression level of three immune checkpoint molecules was determined by the percentage of positive cells and the staining intensity: low (negative intensity and intensity 1, and intensity 2 with positive cells < 10%) and high (intensity 2 with positive cells ≥ 10% and intensity 3) expression (19). The expression of TILs/TAMs was similarly evaluated as previously described (20,21).…”