Immunohistochemical Characterization of Immune Cell Infiltration in Feline Glioma

Diagnostic immunohistochemistry of primary and secondary central nervous system neoplasms of dogs and cats

The diagnosis of primary and secondary CNS neoplasms of dogs and cats relies on histologic examination of autopsy or biopsy samples. In addition, many neoplasms must be further characterized by immunohistochemistry (IHC) for a more refined diagnosis in specific cases. Given the many investigations assessing the diagnostic and prognostic IHC profile of CNS neoplasms in the veterinary literature, it may be difficult for the diagnostic pathologist or pathology trainee to narrow the list of reliable diagnostic IHCs when facing a challenging case. Here we compile a comprehensive list of the most diagnostically relevant immunomarkers that should be utilized for the diagnostic support or confirmation of the most common primary and secondary CNS neoplasms of dogs and cats.

CDYL knockdown reduces glioma development through an antitumor immune response in the tumor microenvironment

Gliomas are highly prevalent and aggressive brain tumors. Growing evidence shows that epigenetic changes are closely related to cancer development. Here we report the roles of Chromodomain Y-like (CDYL), an important epigenetic transcriptional corepressor in the central nervous system in glioma progression. We found that CDYL was highly expressed in glioma tissues and cell lines. CDYL knockdown decreased cell mobility in vitro and significantly reduced tumor burden in the xenograft mouse in vivo. RNA sequencing analysis revealed the upregulation of immune pathways after CDYL knockdown, as well as chemokine (C-C motif) ligand 2 (CCL2) and chemokine (C-X-C motif) ligand 12. The immunohistochemistry staining and macrophage polarization assays showed increased infiltration of M1-like tumor-associated macrophages/microglia (TAMs) while decreased infiltration of M2-like TAMs after CDYL knockdown in vivo and in vitro. Following the in situ TAMs depletion or CCL2 antibody neutralization, the tumor-suppressive role of CDYL knockdown was abolished. Collectively, our results show that CDYL knockdown suppresses glioma progression, which is associated with CCL2-recruited monocytes/macrophages and the polarization of M1-like TAMs in the tumor microenvironment, indicating CDYL as a promising target for glioma treatment.

A review of primary central nervous system neoplasms of cats

Primary central nervous system (CNS) neoplasms are uncommonly diagnosed in cats. The majority of primary feline CNS neoplasms described in the veterinary literature consist of meningioma and glioma occurring mainly in the brain and less often in the spinal cord. Although most neoplasms can be diagnosed based on routine histologic evaluation, less typical tumors need to be further characterized using immunohistochemistry. This review compiles the relevant information about the most common primary CNS neoplasms of cats available in the veterinary literature, aiming to serve as a converging source of information for the topic.

Mast Cell Tumors and Histiocytomas in Domestic Goats and Diagnostic Utility of CD117/c-Kit and Iba1 Immunohistochemistry

Cutaneous round cell tumors in goats present a diagnostic challenge. In this article, we provide a description of caprine cutaneous mast cell tumors (MCT) and histiocytomas, and report on the validation of anti-human antibodies to CD117/KIT and Iba1 by immunohistochemistry on a range of caprine tissues. Cells immunolabeled for CD117/KIT included resident mast cells in normal lung and skin, interstitial cells of Cajal (intestine), and neuronal cell bodies (brain). Cells immunolabeled for Iba1 included resident macrophages in many tissues including normal lung, dendritic cells (hemolymphatic tissues), Kupffer cells, and microglia. Of 5 cutaneous MCT, only one had metachromasia of cytoplasmic granules; however, neoplastic cells of all 5 MCT had positive immunolabeling for CD117/KIT. The CD117/KIT immunolabeling pattern was predominately focal paranuclear in 3 cases, and cytoplasmic or membranous in 1 case each. Two histiocytomas were identified and had strong positive immunolabeling for Iba1 but not CD117/KIT. All 7 cutaneous round cell tumors described herein occurred in goats less than 4 years of age; the 2 cutaneous histiocytomas were in goats less than 14 months of age. Neither of the cutaneous histiocytomas recurred within 24 months of surgical removal.

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

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.

Characterization of Fetal Brain Damage in Early Abortions of Ovine Toxoplasmosis

There is an unacknowledged clinical presentation of ovine toxoplasmosis characterized by early abortions and lesions of fetal leukoencephalomalacia. To investigate the pathogenesis of this condition, the extent and distribution of leukomalacia and the variations in the cell populations associated with it were characterized in 32 fetal brains from 2 previously published experimental studies of Toxoplasma gondii infection in pregnant sheep. Immunohistochemical labeling of βAPP allowed for the detection of leukomalacia in 100/110 (91%) studied samples. There was no clear influence of the challenge dose or the area of the brain (frontal lobe, corpus callosum, midbrain, and cerebellum). In tissues with leukomalacia, there was loss of oligodendrocytes and increased number of astrocytes and microglia both in the areas of necrosis but also in the surrounding area. These findings were similar to those described in ovine experimental models (inflammation syndrome and hypoxic models) of periventricular leukomalacia in humans. Thus, a fetal inflammatory syndrome may be involved in the pathogenesis of early abortion in ovine toxoplasmosis. However, further studies are needed to determine the pathogenesis of this clinical presentation because placental thrombosis and resulting hypoxia could also be responsible for the leukomalacia.

Clinicopathologic Features, Diagnosis, and Characterization of the Immune Cell Population in Canine Choroid Plexus Tumors

The World Health Organization characterizes human choroid plexus tumor (CPT) as papilloma (CPP), atypical CPP (ACPP), and carcinoma (CPC). CPCs can disseminate via cerebrospinal fluid and be mistaken for metastatic carcinoma, creating a diagnostic challenge. Kir7.1 immunohistochemistry (IHC) is a highly reliable tool for diagnostic confirmation of CPTs and their differentiation from metastatic carcinomas in human beings and dogs. This study describes the neuropathology, Kir7.1 staining profile, and the immune cell population within the tumor microenvironment in 11 CPTs in dogs. Archived tissue sections with a diagnosis of CPT were examined and immunolabelled with Kir7.1 for diagnostic confirmation. The number of Ki67-positive neoplastic cells was calculated in 2.4 mm² (equivalent to 10 FN22/40X fields), and a mean value was generated for each neoplasm. IHC for CD3, CD20, MAC387, and Iba1 was performed for immune cell characterization, and the number of stained cells for each antibody was counted in 2.4 mm², generating individual cumulative values for each antibody. T-tests with Bonferroni correction evaluated IHC differences between tumor types, and Spearman's rank correlations evaluated relationships among IHC markers. Kir7.1 immunoreactivity was intense at the apical cell membrane in CPPs and ACPPs, and at the apical cell membrane and cytoplasm in CPCs. Ki67 immunoreactivity was detected in all cases. CD3+ and CD20+ lymphocytes trended together (p = 0.005) and were present within and around all CPTs. Five cases had intravascular MAC387+ monocytes. Iba1 immunoreactivity was robust within and around all tumors. Statistical differences in immune cell markers were not found among tumor types. As previously reported, Kir7.1 is a reliable antibody for the diagnosis of canine CPTs. Although immune cells were present in all cases, no significant associations were found between the type of cells and tumor diagnosis. The characterization of the immune cells within CPTs could be useful in future studies involving immunotherapy.