Morphology, immunohistochemistry, and genetic alterations in dog astrocytomas

Canine glioma in the first year of life: 5 cases

Most canine gliomas occur in adult and aged dogs, and reports in puppies < 12-mo-old are exceedingly rare. Here we describe the occurrence of gliomas in 5 dogs ≤ 12-mo-old. The affected patients (4 males, 1 female) were 3-12-mo-old (x̄ = 6.6-mo-old). None of the dogs were brachycephalic. Clinical signs consisted of dullness (2 cases), seizures (2 cases), vestibular signs, and deafness (1 case each). All patients were euthanized. Grossly, neoplasms were pale-tan or red, soft masses in the telencephalon (4 cases) or gelatinous leptomeningeal thickening in the brain and spinal cord (1 case). Neoplasms were classified as astrocytomas (3 cases) and oligodendrogliomas (2 cases) based on histology or histology and IHC. Our findings confirm that, while exceptionally rare, canine gliomas occur in the first year of life, and are clinically, morphologically, and immunohistochemically similar to gliomas in adult and aged dogs.

Domestic Animal Models of Central Nervous System Tumors: Focus on Meningiomas

Intracranial primary tumors (IPTs) are aggressive forms of malignancies that cause high mortality in both humans and domestic animals. Meningiomas are frequent adult IPTs in humans, dogs, and cats, and both benign and malignant forms cause a decrease in life quality and survival. Surgery is the primary therapeutic approach to treat meningiomas, but, in many cases, it is not resolutive. The chemotherapy and targeted therapy used to treat meningiomas also display low efficacy and many side effects. Therefore, it is essential to find novel pharmacological approaches to increase the spectrum of therapeutic options for meningiomas. This review analyzes the similarities between human and domestic animal (dogs and cats) meningiomas by evaluating the molecular and histological characteristics, diagnosis criteria, and treatment options and highlighting possible research areas to identify novel targets and pharmacological approaches, which are useful for the diagnosis and therapy of this neoplasia to be used in human and veterinary medicine.

A High Grade Astrocytoma with Pilocytic Morphology in a 5-Month-Old American Bulldog

Simple Summary

Dogs are valuable models for spontaneous intracranial neoplasia in humans. The most common intracranial neoplasm in dogs is meningioma, followed by glioma and choroid plexus tumors. Pilocytic astrocytoma (PA) is a form of glioma and is a common childhood and adolescent tumor in humans. There have been two previous reports of PA in dogs. These cases were both adult dogs and the clinical and imaging features were not described. This report describes a 23-week-old female intact American Bulldog with a 2-week progressive history of neurologic dysfunction. Magnetic resonance imaging (MRI) revealed a large hemorrhagic mass that was confirmed on post-mortem examination to be a high-grade astrocytoma with pilocytic morphology. This case is the first to report a high-grade astrocytoma with pilocytic morphology in a juvenile dog.

Abstract

A 23-week-old female intact American Bulldog was presented for a two-week history of progressive circling to the right, twitching, and altered mentation. Magnetic resonance imaging (MRI) revealed a non-contrast enhancing hemorrhagic mass centered in the right thalamus with concurrent subdural and intraventricular hemorrhage. Post-mortem histologic examination of the brain confirmed a mass centered on the thalamus with histomorphologic features consistent with a high-grade astrocytoma with pilocytic morphology. To the authors’ knowledge, the present case is the first to report clinical and imaging characteristics of a high-grade astrocytoma with pilocytic morphology in a young dog.

Developing a translational murine-to-canine pathway for an IL-2/agonist anti-CD40 antibody cancer immunotherapy

Human and canine sarcomas are difficult to treat soft tissue malignancies with an urgent need for new improved therapeutic options. Local recurrence rates for humans are between 10%-30%, and 30%-40% develop metastases. Outcomes for dogs with sarcoma vary with grade but can be similar. Pet dogs share the human environment and represent human cancer with genetic variation in hosts and tumours. We asked if our murine studies using genetically identical mice and cloned tumour cells were translatable to larger, genetically diverse domestic dogs with naturally occurring tumours, to (i) develop a canine cancer therapeutic, and (ii) to use as a translational pathway to humans. Our murine studies showed that intra-tumoral delivery of interleukin-2 (IL-2) plus an agonist anti-CD40 antibody (Ab) induces long-term curative responses ranging from 30% to 100%, depending on tumour type. We developed an agonist anti-canine-CD40 Ab and conducted a phase I dose finding/toxicology 3 + 3 clinical trial in dogs (n = 27) with soft tissue sarcomas on account of suitability for intratumoral injection and straightforward monitoring. Dogs were treated with IL-2 plus anti-CD40 antibody for 2 weeks. Three dose levels induced tumour regression with minimal side effects, measured by monitoring, haematological and biochemical assays. Importantly, our mouse and canine studies provide encouraging fundamental proof-of-concept data upon which we can develop veterinary and human immunotherapeutic strategies.

[Retinal tumors in adults: Part 2 nonvascular tumors of retina and retinal pigment epithelium]

Retinal tumors are a heterogeneous group of congenital and acquired lesions. In the second part of the article retinocytic and glial cell tumors of the retina, tumors of the retinal pigment epithelium, malignant tumors, such as lymphomas and metastases are presented. In benign and malignant tumors visual symptoms, such as exudative retinal detachment occur, which often lead to irreversible visual impairments. Because visual symptoms are often a manifestation of systemic diseases, the ophthalmologist plays an important role in the accurate and early diagnosis of retinal tumors. This article reviews the most important clinical and diagnostic features of retinal tumors in adults, the systemic associations and the literature on currently available treatment strategies.

Multiparametric magnetic resonance imaging features of a canine glioblastoma model

PURPOSE

To assess glioblastoma multiforme (GBM) formation with similar imaging characteristics to human GBM using multiparametric magnetic resonance imaging (MRI) in an orthotopic xenograft canine GBM model.

MATERIALS AND METHODS

The canine GBM cell line J3T1 was subcutaneously injected into 6-week-old female BALB/c nude mice to obtain tumour fragments. Tumour fragments were implanted into adult male mongrel dog brains through surgery. Multiparametric MRI was performed with conventional MRI, diffusion-weighted imaging, and dynamic susceptibility contrast-enhanced perfusion-weighted imaging at one week and two weeks after surgery in a total of 15 surgical success cases. The presence of tumour cells, the necrotic area fraction, and the microvessel density (MVD) of the tumour on the histologic specimen were assessed. Tumour volume, diffusion, and perfusion parameters were compared at each time point using Wilcoxon signed-rank tests, and the differences between tumour and normal parenchyma were compared using unpaired t-tests. Spearman correlation analysis was performed between the imaging and histologic parameters.

RESULTS

All animals showed a peripheral enhancing lesion on MRI and confirmed the presence of a tumour through histologic analysis (92.3%). The normalized perfusion values did not show significant decreases through at least 2 weeks after the surgery (P > 0.05). There was greater cerebral blood volume and flow in the GBM than in the normal-appearing white matter (1.46 ± 0.25 vs. 1.13 ± 0.16 and 1.30 ± 0.22 vs. 1.02 ± 0.14; P < 0.001 and P < 0.001, respectively). The MVD in the histologic specimens was correlated with the cerebral blood volume in the GBM tissue (r = 0.850, P = 0.004).

CONCLUSION

Our results suggest that the canine GBM model showed perfusion imaging characteristics similar to those of humans, and it might have potential as a model to assess novel technical developments for GBM treatment.

Immunohistochemical evaluation of immune cell infiltration in canine gliomas

Evasion of the immune response is an integral part of the pathogenesis of glioma. In humans, important mechanisms of immune evasion include recruitment of regulatory T cells (Tregs) and polarization of macrophages toward an M2 phenotype. Canine glioma has a robust immune cell infiltrate that has not been extensively characterized. The purpose of this study was to determine the distribution of immune cells infiltrating spontaneous intracranial canine gliomas. Seventy-three formalin-fixed, paraffin-embedded tumor samples were evaluated using immunohistochemistry for CD3, forkhead box 3 (FOXP3), CD20, Iba1, calprotectin (Mac387), CD163, and indoleamine 2,3-dioxygenase (IDO). Immune cell infiltration was present in all tumors. Low-grade and high-grade gliomas significantly differed in the numbers of FoxP3+ cells, Mac387+ cells, and CD163+ cells (P = .006, .01, and .01, respectively). Considering all tumors, there was a significant increase in tumor area fraction of CD163 compared to Mac387 (P < .0001), and this ratio was greater in high-grade tumors than in low-grade tumors (P = .005). These data warrant further exploration into the roles of macrophage repolarization or Treg interference therapy in canine glioma.

The Role of Bcl-xL Protein Research in Veterinary Oncology

Due to their significant impact on human and animal health, cancer diseases are an area of considerable concern for both human and veterinary medicine. Research on the cancer pathogenesis in companion animals, such as dogs, allows not only for improving canine cancer treatment, but also for translating the results into human oncology. Disruption of apoptosis in tumor-transformed cells is a well-known mechanism leading to the development of cancer. One of the main factors involved in this process are proteins belonging to the B-cell lymphoma 2 (Bcl-2) family, and the imbalance between pro-apoptotic and anti-apoptotic members of this family contributes to the development of cancer. Studies on the function of these proteins, including B-cell lymphoma-extra large (Bcl-xL), have also been intensively conducted in companion animals. The Bcl-xL gene was sequenced and found to share over 99% homology with the human protein. Research showed that the Bcl-2 family plays the same role in human and canine cells, and data from studies in dogs are fully translatable to other species, including humans. The role of this protein family in cancer development was also confirmed. The article presents the current state of knowledge on the importance of the Bcl-xL protein in veterinary oncology.

Companion animal models of neurological disease

Clinical translation of novel therapeutics that improve the survival and quality of life of patients with neurological disease remains a challenge, with many investigational drug and device candidates failing in advanced stage clinical trials. Naturally occurring inherited and acquired neurological diseases, such as epilepsy, inborn errors of metabolism, brain tumors, spinal cord injury, and stroke occur frequently in companion animals, and many of these share epidemiologic, pathophysiologic and clinical features with their human counterparts. As companion animals have a relatively abbreviated lifespan and genetic background, are immunocompetent, share their environment with human caregivers, and can be clinically managed using techniques and tools similar to those used in humans, they have tremendous potential for increasing the predictive value of preclinical drug and device studies. Here, we review comparative features of spontaneous neurological diseases in companion animals with an emphasis on neuroimaging methods and features, illustrate their historical use in translational studies, and discuss inherent limitations associated with each disease model. Integration of companion animals with naturally occurring disease into preclinical studies can complement and expand the knowledge gained from studies in other animal models, accelerate or improve the manner in which research is translated to the human clinic, and ultimately generate discoveries that will benefit the health of humans and animals.

Procaspase-3 Overexpression in Cancer: A Paradoxical Observation with Therapeutic Potential

Many anticancer strategies rely on the promotion of apoptosis in cancer cells as a means to shrink tumors. Crucial for apoptotic function are executioner caspases, most notably caspase-3, that proteolyze a variety of proteins, inducing cell death. Paradoxically, overexpression of procaspase-3 (PC-3), the low-activity zymogen precursor to caspase-3, has been reported in a variety of cancer types. Until recently, this counterintuitive overexpression of a pro-apoptotic protein in cancer has been puzzling. Recent studies suggest subapoptotic caspase-3 activity may promote oncogenic transformation, a possible explanation for the enigmatic overexpression of PC-3. Herein, the overexpression of PC-3 in cancer and its mechanistic basis is reviewed; collectively, the data suggest the potential for exploitation of PC-3 overexpression with PC-3 activators as a targeted anticancer strategy.

Microtubule-Associated Protein 2 Expression in Canine Glioma

Canine glioma is considered a potential model for human glioma, with recent studies of occurrence, therapy, and reclassification supporting the value of the canine model. The current diagnosis of canine glioma is based on morphologic criteria and immunohistochemistry (IHC), including oligodendrocyte transcription factor 2 (Olig2), glial fibrillary acidic protein (GFAP), and 2′, 3′ cyclic nucleotide phosphatase (CNPase). Microtubule-associated protein 2 (MAP2) is a proven marker of human glioma and is used to complement the diagnosis and its specific immunoreactivity pattern contributes to the differentiation of astrocytomas from other glial tumors. The objective of this study was to evaluate whether canine gliomas express MAP2 and to explore differences in the pattern of immunolabeling between different gliomas. Seventy-eight cases of canine glioma were evaluated for MAP2 expression by immunohistochemistry. A glial origin was supported by Olig2 IHC in all cases. MAP2 immunolabeling was evaluated on a semi-quantitative basis, including the percentage of immunolabeled neoplastic cells, as well as the signal intensity, distribution, and pattern of immunolabeling. MAP2 was expressed in all cases, with significant correlation between diagnosis and signal intensity (P = 0.04). MAP2 immunolabeling distribution was dominated by diffuse (34/78; 44%), followed by patchy (20/78; 26%), multifocal to coalescing (16/78; 21%), and scattered (8/78; 10%). All oligodendrogliomas (53/53; 100%) and undefined gliomas (12/12; 100%) revealed a combination of perinuclear and cytoplasmic immunolabeling, and all but 3 astrocytomas had a combination of perinuclear and cytoplasmic processes immunolabeling (10/13; 77%). Significant correlation between immunolabeling pattern and diagnosis was obtained (P = 0.001). The study demonstrates that MAP2 is expressed in canine gliomas and the pattern of expression can also be applied to help distinguish astrocytomas from oligodendrogliomas and undefined gliomas.

Canine Primary Intracranial Cancer: A Clinicopathologic and Comparative Review of Glioma, Meningioma, and Choroid Plexus Tumors

In the dog, primary intracranial neoplasia represents ~2-5% of all cancers and is especially common in certain breeds including English and French bulldogs and Boxers. The most common types of primary intracranial cancer in the dog are meningioma, glioma, and choroid plexus tumors, generally occurring in middle aged to older dogs. Much work has recently been done to understand the characteristic imaging and clinicopathologic features of these tumors. The gross and histologic landscape of these tumors in the dog compare favorably to their human counterparts with many similarities noted in histologic patterns, subtype, and grades. Data informing the underlying molecular abnormalities in the canine tumors have only begun to be unraveled, but reveal similar pathways are mutated between canine and human primary intracranial neoplasia. This review will provide an overview of the clinicopathologic features of the three most common forms of primary intracranial cancer in the dog, delve into the comparative aspects between the dog and human neoplasms, and provide an introduction to current standard of care while also highlighting novel, experimental treatments that may help bridge the gap between canine and human cancer therapies.

A Revised Diagnostic Classification of Canine Glioma: Towards Validation of the Canine Glioma Patient as a Naturally Occurring Preclinical Model for Human Glioma

The National Cancer Institute-led multidisciplinary Comparative Brain Tumor Consortium (CBTC) convened a glioma pathology board, comprising both veterinarian and physician neuropathologists, and conducted a comprehensive review of 193 cases of canine glioma. The immediate goal was to improve existing glioma classification methods through creation of a histologic atlas of features, thus yielding greater harmonization of phenotypic characterization. The long-term goal was to support future incorporation of clinical outcomes and genomic data into proposed simplified diagnostic schema, so as to further bridge the worlds of veterinary and physician neuropathology and strengthen validity of the dog as a naturally occurring, translationally relevant animal model of human glioma. All cases were morphologically reclassified according to a new schema devised by the entire board, yielding a majority opinion diagnosis of astrocytoma (43, 22.3%), 19 of which were low-grade and 24 high-grade, and oligodendroglioma (134, 69.4%), 35 of which were low-grade and 99 were high-grade. Sixteen cases (8.3%) could not be classified as oligodendroglioma or astrocytoma based on morphology alone and were designated as undefined gliomas. The simplified classification scheme proposed herein provides a tractable means for future addition of molecular data, and also serves to highlight histologic similarities and differences between human and canine glioma.

Inter- and Intraobserver Agreement of Canine and Feline Nervous System Tumors

In routine diagnostic activity, pathologists may be confronted with nervous system tumors. The lack of clinical information, economic restrictions for additional testing, and the lack of expertise in neuropathology may render the diagnosis challenging. The goals of this study were to assess the agreement in diagnosing nervous system tumors in domestic carnivores among 4 board-certified surgical pathologists without particular expertise in neuropathology and a neuropathologist expert, and to investigate the utility of special stains frequently used in routine diagnostic laboratories. Forty-six tumors (7 cats, 38 dogs, and 1 unknown carnivore) were retrieved and 1 hematoxylin and eosin-stained slide per tumor was selected. Diagnoses (tumor type and subtype) were formulated based on histological features and available clinical information. Confidence in the diagnosis was also scored. Subsequently, a panel of histochemical and immunohistochemical stains (Gordon Sweet silver stain and immunohistochemistry for AE1/AE3, vimentin, glial fibrillary acid protein, S100, neuron-specific enolase and neurofilament) was evaluated by the pathologists, who either confirmed or changed their original diagnoses. Intraobserver and interobserver agreement and confidence in relation to diagnosis before and after analysis of special stains were assessed. The use of special stains increased the complete agreement among surgical pathologists, with regard to tumor type, from 63% to 74%. Cases with a high confidence score had a higher interobserver agreement than cases with a low confidence score. These results suggest that pathologists without expertise in neuropathology agree in the diagnosis of most nervous system tumors, and special stains available in most laboratories only slightly increase this agreement.

Isocitrate Dehydrogenase 1 Expression in Canine Gliomas

Mutation of the isocitrate dehydrogenase 1 (IDH1) gene at codon 132 has been identified in approximately 70% of low-grade (II and III) human gliomas and secondary glioblastomas, with the IDH1 R132H point mutation representing 92.7% of these mutations. In people, the presence of an IDH1 gene mutation is associated with a better prognosis (both progression-free survival time and overall survival time) and a better response to therapy, including chemotherapy and radiation therapy. Furthermore, IDH1 mutations are included in diagnostic panels to improve diagnosis and molecular classification. Canine gliomas resemble their human counterpart both morphologically and immunohistochemically, therefore they are likely to share similar genetic abnormalities. The IDH1 gene is also comparable between man and dogs. If the IDH1 R132H point mutation is demonstrated in canine gliomas, the prognostic significance of this mutation in people may be transferable to the dog. The objective of this study was to investigate canine gliomas for the IDH1 R132H point mutation using immunohistochemistry. Thirty-one formalin-fixed and paraffin wax-embedded canine gliomas were examined for both IDH1 R132H expression and pan-IDH1 (IDH1 wild-type and point mutated IDH1). Glial tumour specimens were recorded to be either positive or negative for expression. Pan-IDH1 expression was identified in all 31 tumours (100%), while the IDH1 R132H point mutation was identified in none of the tumours (0%). Therefore, the IDH1 R132H point mutation was not identified in this population of canine gliomas and may not be a suitable biomarker or treatment target in canine gliomas. Further investigation is required to determine if other point mutations occur in the IDH1 gene of canine gliomas.

In vitro effect of chlorambucil on human glioma cell lines (SF767 and U87-MG), and human microvascular endothelial cell (HMVEC) and endothelial progenitor cells (ECFCs), in the context of plasma chlorambucil concentrations in tumor-bearing dogs

The objective of this study was to investigate a possible mechanism of action of metronomic chlorambucil on glioma by studying the in vitro cytotoxicity and anti-angiogenic effects on glioma and endothelial cells, respectively. The in vitro LD50 and IC50 of chlorambucil were determined using human SF767 and U87-MG glioma cell lines, human microvascular endothelial cells (HMVECs) and human endothelial colony forming cells (ECFCs). Results were analyzed in the context of chlorambucil concentrations measured in the plasma of tumor-bearing dogs receiving 4 mg m-2 metronomic chlorambucil. The LD50 and IC50 of chlorambucil were 270 μM and 114 μM for SF767, and 390 μM and 96 μM for U87-MG, respectively. The IC50 of chlorambucil was 0.53 μM and 145 μM for the HMVECs and ECFCs, respectively. In pharmacokinetic studies, the mean plasma Cmax of chlorambucil was 0.06 μM. Results suggest that metronomic chlorambucil in dogs does not achieve plasma concentrations high enough to cause direct cytotoxic or growth inhibitory effects on either glioma or endothelial cells.

Primary central nervous system neoplasms in African hedgehogs

In this retrospective study, we describe the clinicopathologic and immunohistochemical findings in a series of primary central nervous system (CNS) neoplasms in African hedgehogs ( Atelerix albiventris). Twelve CNS neoplasms were found among 762 African hedgehog submissions (1.6%) to a private diagnostic laboratory in an 18-y period. The median age of affected hedgehogs was 3.5 y. No sex predilection was found. Hindlimb paresis, weakness, and ataxia were the most commonly reported clinical signs. Gangliogliomas ( n = 6) and astrocytomas ( n = 5) were the most commonly observed neoplasms; one oligodendroglioma was found. Gangliogliomas were found in the cerebellar white matter (2 of 6), brainstem (4 of 6), cervical spinal cord (1 of 6), and frontal lobe (1 of 6); one metastasized to the tongue. Gangliogliomas were immunoreactive for neurofilament protein (NFP), glial fibrillary acidic protein (GFAP), S100, and CD34. All astrocytomas were gemistocytic, located in the cerebrum, and none of these neoplasms metastasized. Astrocytomas were positive for GFAP, S100, and CD34, but negative for NFP. The oligodendroglioma was located in the cerebrum, and was positive for S100, but negative for GFAP and NFP.

Convection-Enhanced Delivery of Polymeric Nanoparticles Encapsulating Chemotherapy in Canines with Spontaneous Supratentorial Tumors

BACKGROUND

Despite aggressive multimodal treatment, survival for patients with glioblastoma remains dismal. One obstacle to improving patient outcomes is the difficulty in delivering adequate therapeutic to the central nervous system due to the presence of the blood-brain barrier. Although direct drug infusion by convection-enhanced delivery (CED) can bypass the blood-brain barrier and facilitate delivery to intracranial tumors, determining the distribution of delivered therapeutic remains problematic. Image guidance is a strategy that can optimize the accuracy of therapeutic delivery.

METHODS

Here we performed an open-label clinical trial in 10 pet dogs with spontaneous intracranial tumors to examine the target coverage accuracy of delivering polymeric magnetite nanoparticles (PMNPs) encapsulating temozolomide (TMZ). A modified small animal frame was applied to the head of each subject, and PMNPs were delivered stereotactically to the center of the tumor. Magnetic resonance imaging (MRI) was performed immediately postoperatively to examine PMNP distribution, and the animals were followed until death.

RESULTS

Nine of the 10 dogs underwent PMNP infusion without complications. No infusate backflow was observed during any procedure. In 70% of the cases, the infusion accurately targeted the tumor mass, as determined by the presence of PMNP signal in the tumor on immediate postoperative MRI.

CONCLUSIONS

These data suggest that CED of PMNPs carrying TMZ is safe in dogs with intracranial tumors and can lead to nanoparticle distribution in the region of the target. Image guidance is an important adjunct to CED, because distribution is unpredictable, with the potential for missed target delivery.

Convection-enhanced delivery of cetuximab conjugated iron-oxide nanoparticles for treatment of spontaneous canine intracranial gliomas

Cetuximab conjugated iron-oxide nanoparticles (cetuximab-IONPs) have shown both in-vitro and in-vivo anti-tumor efficacy against gliomas. The purpose of this pilot study was to evaluate the safety and potential efficacy of cetuximab-IONPs for treatment of spontaneously occurring intracranial gliomas in canines after convection-enhanced delivery (CED). The use of CED allowed for direct infusion of the cetuximab-IONPs both intratumorally and peritumorally avoiding the blood brain barrier (BBB) and limiting systemic effects. A total of eight dogs participated in the study and only two developed mild post-operative complications, which resolved with medical therapy. All canines underwent a single CED treatment of the cetuximab-IONPs over 3 days and did not receive any further adjuvant treatments. Volumetric analysis showed a median reduction in tumor size of 54.9% by MRI at 1-month (4-6 weeks) follow-up. Five dogs were euthanized due to recurrence of neurological signs other than seizures, two due to recurrent seizures, and one dog died in his sleep. Median survival time after surgery was 248 days (mean 367 days).

Immunologic and gene expression profiles of spontaneous canine oligodendrogliomas

Malignant glioma (MG), the most common primary brain tumor in adults, is extremely aggressive and uniformly fatal. Several treatment strategies have shown significant preclinical promise in murine models of glioma; however, none have produced meaningful clinical responses in human patients. We hypothesize that introduction of an additional preclinical animal model better approximating the complexity of human MG, particularly in interactions with host immune responses, will bridge the existing gap between these two stages of testing. Here, we characterize the immunologic landscape and gene expression profiles of spontaneous canine glioma and evaluate its potential for serving as such a translational model. RNA in situ hybridization, flowcytometry, and RNA sequencing were used to evaluate immune cell presence and gene expression in healthy and glioma-bearing canines. Similar to human MGs, canine gliomas demonstrated increased intratumoral immune cell infiltration (CD4+, CD8+ and CD4+Foxp3+ T cells). The peripheral blood of glioma-bearing dogs also contained a relatively greater proportion of CD4+Foxp3+ regulatory T cells and plasmacytoid dendritic cells. Tumors were strongly positive for PD-L1 expression and glioma-bearing animals also possessed a greater proportion of immune cells expressing the immune checkpoint receptors CTLA-4 and PD-1. Analysis of differentially expressed genes in our canine populations revealed several genetic changes paralleling those known to occur in human disease. Naturally occurring canine glioma has many characteristics closely resembling human disease, particularly with respect to genetic dysregulation and host immune responses to tumors, supporting its use as a translational model in the preclinical testing of prospective anti-glioma therapies proven successful in murine studies.

Feline glioma: a retrospective study and review of the literature

Case series summary This study aimed to evaluate the pathologic and diagnostic features of 13 cases of feline glioma diagnosed at two veterinary diagnostic institutions over 16 years. A retrospective search was conducted using the laboratory information system. Selected cases were reviewed, tumors were classified according to the 2007 World Health Organization Classification of Tumours of the Central Nervous System, and tissue sections were submitted to an immunohistochemistry panel for further characterization. Affected cats were adults (average age 8 years), and male neutered (9/13) domestic shorthair cats (12/13) were over-represented. Clinical signs had acute onset and were progressive, lasting from 1-60 days (average course 20.7 days). Euthanasia was elected in all but one case, owing to a poor prognosis or because of a suspicion of rabies. Tumors occurred in the telencephalon (8/13), spinal cord (3/13) and brainstem (2/13). Gross changes in seven cases consisted of well- or poorly demarcated, gray-to-brown, soft, gelatinous masses that often caused secondary changes to the brain. The final diagnosis and classification were made based on histopathology and immunohistochemistry. Diagnoses consisted of oligodendroglioma (six cases), anaplastic astrocytoma (two cases), oligoastrocytoma, anaplastic ependymoma, gliomatosis cerebri, glioblastoma and anaplastic oligodendroglioma (one case each). Relevance and novel information This article confirms the need for a full neurologic and neuropathologic examination in cats with clinical neurologic disease. In addition, it highlights and proposes a complete routine immunohistochemical panel for diagnostic confirmation and differentiation between glioma and other morphologically similar central nervous system neoplasms in cats.

Modeling phenotypes of malignant gliomas

Malignant gliomas are primary tumors of the central nervous system characterized by diffuse infiltration into the brain and a high recurrence rate. Advances in comprehensive genomic studies have provided unprecedented insight into the genetic and molecular heterogeneity of these tumors and refined our understanding of their evolution from low to high grade. However, similar levels of phenotypic characterization are indispensable to understanding the complexity of malignant gliomas. Experimental glioma models have also achieved great progress in recent years. Advances in transgenic technologies and cell culture have allowed the establishment of mouse models that mirror the human disease with increasing fidelity and which support single-cell resolution for phenotypic analyses. Here we review the major types of preclinical glioma models, with an emphasis on how recent developments in experimental modeling have shed new light on two fundamental aspects of glioma phenotype, their cell of origin and their invasive potential.

Dogs are man's best friend: in sickness and in health

With the median survival of 14.6 months following best available standard of care, malignant gliomas (MGs) remain one of the biggest therapeutic challenges of the modern time. Although the last several decades have witnessed tremendous advancement in our understanding of MG and evolution of many successful preclinical therapeutic strategies, even the most successful preclinical therapeutic strategies often fail to cross the phase I/II clinical trial threshold. One of the significant, but less commonly discussed, barriers in developing effective glioma therapy is the lack of a robust preclinical model. For the last 30 years, rodent orthotopic xenograft models have been extensively used in the preclinical setting. Although they provide a good basic model for understanding tumor biology, their value in successfully translating preclinical therapeutic triumph into clinical success is extremely poor. Companion dogs, which share the same environmental stress as their human counterparts, also spontaneously develop MGs. Dog gliomas that develop spontaneously in an immunocompetent host are very similar to human gliomas and potentially provide a stronger platform for validating the efficacy of therapeutic strategies proven successful in preclinical mouse models. Integrating this model can accelerate development of effective therapeutic options that will benefit both human subjects and pet dogs.

Synergistic and targeted therapy with a procaspase-3 activator and temozolomide extends survival in glioma rodent models and is feasible for the treatment of canine malignant glioma patients

Purpose

Glioblastoma is a deadly brain cancer with a median survival time of ∼15 months. Ionizing radiation plus the DNA alkylator temozolomide (TMZ) is the current standard therapy. PAC-1, a procaspase-3 activating small molecule, is blood-brain barrier penetrant and has previously demonstrated ability to synergize with diverse pro-apoptotic chemotherapeutics. We studied if PAC-1 could enhance the activity of TMZ, and whether addition of PAC-1 to standard treatment would be feasible in spontaneous canine malignant gliomas.

Experimental Design

Using cell lines and online gene expression data, we identified procaspase-3 as a potential molecular target for most glioblastomas. We investigated PAC-1 as a single agent and in combination with TMZ against glioma cells in culture and in orthotopic rodent models of glioma. Three dogs with spontaneous gliomas were treated with an analogous human glioblastoma treatment protocol, with concurrent PAC-1.

Results

Procaspase-3 is expressed in gliomas, with higher gene expression correlating with increased tumor grade and decreased prognosis. PAC-1 is cytotoxic to glioma cells in culture and active in orthotopic rodent glioma models. PAC-1 added to TMZ treatments in cell culture increases apoptotic death, and the combination significantly increases survival in orthotopic glioma models. Addition of PAC-1 to TMZ and radiation was well-tolerated in 3 out of 3 pet dogs with spontaneous glioma, and partial to complete tumor reductions were observed.

Conclusions

Procaspase-3 is a clinically relevant target for treatment of glioblastoma. Synergistic activity of PAC-1/TMZ in rodent models and the demonstration of feasibility of the combined regime in canine patients suggest potential for PAC-1 in the treatment of glioblastoma.

Creation of an NCI comparative brain tumor consortium: informing the translation of new knowledge from canine to human brain tumor patients

On September 14-15, 2015, a meeting of clinicians and investigators in the fields of veterinary and human neuro-oncology, clinical trials, neuropathology, and drug development was convened at the National Institutes of Health campus in Bethesda, Maryland. This meeting served as the inaugural event launching a new consortium focused on improving the knowledge, development of, and access to naturally occurring canine brain cancer, specifically glioma, as a model for human disease. Within the meeting, a SWOT (strengths, weaknesses, opportunities, and threats) assessment was undertaken to critically evaluate the role that naturally occurring canine brain tumors could have in advancing this aspect of comparative oncology aimed at improving outcomes for dogs and human beings. A summary of this meeting and subsequent discussion are provided to inform the scientific and clinical community of the potential for this initiative. Canine and human comparisons represent an unprecedented opportunity to complement conventional brain tumor research paradigms, addressing a devastating disease for which innovative diagnostic and treatment strategies are clearly needed.

Low-grade Glial Tumor with Features of Astroblastoma in a Dog

A 12-year-old, neutered, male Belgian Malinois/Great Dane cross dog presented with a 5-month history of weakness and lack of endurance followed by acute onset of rear limb ataxia. At autopsy, a 9 x 16 mm, multilobular, firm, white to tan, expansile mass was found in the cerebellum. Mild dilatation of the lateral ventricles was also noted. Histologically, there was a well-demarcated glial neoplasm composed of medium-sized astrocytic elements that had homogeneous cytoplasm, sometimes with globular eosinophilic inclusions, irregular peripherally located nuclei with a single nucleolus, and short cytoplasmic processes. Prominent peri-vascular pseudorosettes with cellular processes in contact with blood vessels were present. Some blood vessels exhibited hyalinized walls. Mitotic figures were not observed. Immunohistochemically, neoplastic cells expressed glial fibrillary acidic protein and vimentin. These features are consistent with an astroblastoma. This is the first clinicopathologic correlation and detailed description of a low-grade glial tumor with features of astroblastoma in a dog.

Chromosomal Aberrations in Canine Gliomas Define Candidate Genes and Common Pathways in Dogs and Humans

Spontaneous gliomas in dogs occur at a frequency similar to that in humans and may provide a translational model for therapeutic development and comparative biological investigations. Copy number alterations in 38 canine gliomas, including diffuse astrocytomas, glioblastomas, oligodendrogliomas, and mixed oligoastrocytomas, were defined using an Illumina 170K single nucleotide polymorphism array. Highly recurrent alterations were seen in up to 85% of some tumor types, most notably involving chromosomes 13, 22, and 38, and gliomas clustered into 2 major groups consisting of high-grade IV astrocytomas, or oligodendrogliomas and other tumors. Tumor types were characterized by specific broad and focal chromosomal events including focal loss of the INK4A/B locus in glioblastoma and loss of the RB1 gene and amplification of the PDGFRA gene in oligodendrogliomas. Genes associated with the 3 critical pathways in human high-grade gliomas (TP53, RB1, and RTK/RAS/PI3K) were frequently associated with canine aberrations. Analysis of oligodendrogliomas revealed regions of chromosomal losses syntenic to human 1p involving tumor suppressor genes, such as CDKN2C, as well as genes associated with apoptosis, autophagy, and response to chemotherapy and radiation. Analysis of high frequency chromosomal aberrations with respect to human orthologues may provide insight into both novel and common pathways in gliomagenesis and response to therapy.

Utilizing the Dog Genome in the Search for Novel Candidate Genes Involved in Glioma Development-Genome Wide Association Mapping followed by Targeted Massive Parallel Sequencing Identifies a Strongly Associated Locus

Gliomas are the most common form of malignant primary brain tumors in humans and second most common in dogs, occurring with similar frequencies in both species. Dogs are valuable spontaneous models of human complex diseases including cancers and may provide insight into disease susceptibility and oncogenesis. Several brachycephalic breeds such as Boxer, Bulldog and Boston Terrier have an elevated risk of developing glioma, but others, including Pug and Pekingese, are not at higher risk. To identify glioma-associated genetic susceptibility factors, an across-breed genome-wide association study (GWAS) was performed on 39 dog glioma cases and 141 controls from 25 dog breeds, identifying a genome-wide significant locus on canine chromosome (CFA) 26 (p = 2.8 x 10-8). Targeted re-sequencing of the 3.4 Mb candidate region was performed, followed by genotyping of the 56 SNVs that best fit the association pattern between the re-sequenced cases and controls. We identified three candidate genes that were highly associated with glioma susceptibility: CAMKK2, P2RX7 and DENR. CAMKK2 showed reduced expression in both canine and human brain tumors, and a non-synonymous variant in P2RX7, previously demonstrated to have a 50% decrease in receptor function, was also associated with disease. Thus, one or more of these genes appear to affect glioma susceptibility.

Epidermal Growth Factor Receptor and Ki-67 Expression in Canine Gliomas

Novel therapies, including molecular targeted therapies, are being developed for the treatment of human gliomas. To use such therapies for canine gliomas, more complete characterization of molecular targets is required. Epidermal growth factor receptor (EGFR) is one such therapeutic target used in human glioma trials, and the Ki-67 labeling index (LI) is a marker of proliferation and a prognostic indicator. The objectives of this cross-sectional study were to evaluate the expression of EGFR and Ki-67 in canine gliomas and to determine if immunopositivity is associated with tumor type and histologic grade. Thirty-one formalin-fixed, paraffin-embedded canine gliomas were evaluated for EGFR and Ki-67 expression by immunohistochemistry. EGFR immunopositivity was evaluated using a semi-quantitative score and the Ki-67 LI calculated based on the percentage of positive cells. EGFR and Ki-67 expression were identified in 16 of 31 (52%) and 28 of 31 (90%) tumors, respectively. EGFR expression was significantly greater in high-grade tumors compared with low-grade tumors (P = .04) and was significantly greater in gliomatosis cerebri compared with oligodendroglioma (P = .002), astrocytoma (P = .01), and oligoastrocytoma (P = .04). The Ki-67 LI was significantly greater in high-grade tumors compared with low grade tumors (P = .02); the median Ki-67 LI was 2.3% (range, 0%-17.6%) for low-grade tumors and 9.3% (range, 1.7%-41.0%) for high-grade tumors. A significant moderate correlation was identified between EGFR immunopositivity and Ki-67 LI (r = 0.47, P = .007). Overall, EGFR may be a suitable therapeutic target for some canine gliomas, particularly gliomatosis cerebri.

Safety and feasibility of the NanoKnife system for irreversible electroporation ablative treatment of canine spontaneous intracranial gliomas

OBJECT

Irreversible electroporation (IRE) is a novel nonthermal ablation technique that has been used for the treatment of solid cancers. However, it has not been evaluated for use in brain tumors. Here, the authors report on the safety and feasibility of using the NanoKnife IRE system for the treatment of spontaneous intracranial gliomas in dogs.

METHODS

Client-owned dogs with a telencephalic glioma shown on MRI were eligible. Dog-specific treatment plans were generated by using MRI-based tissue segmentation, volumetric meshing, and finite element modeling. After biopsy confirmation of glioma, IRE treatment was delivered stereotactically with the NanoKnife system using pulse parameters and electrode configurations derived from therapeutic plans. The primary end point was an evaluation of safety over the 14 days immediately after treatment. Follow-up was continued for 12 months or until death with serial physical, neurological, laboratory, and MRI examinations.

RESULTS

Seven dogs with glioma were treated. The mean age of the dogs was 9.3 ± 1.6 years, and the mean pretreatment tumor volume was 1.9 ± 1.4 cm3. The median preoperative Karnofsky Performance Scale score was 70 (range 30–75). Severe posttreatment toxicity was observed in 2 of the 7 dogs; one developed fatal (Grade 5) aspiration pneumonia, and the other developed treatment-associated cerebral edema, which resulted in transient neurological deterioration. Results of posttreatment diagnostic imaging, tumor biopsies, and neurological examinations indicated that tumor ablation was achieved without significant direct neurotoxicity in 6 of the 7 dogs. The median 14-day post-IRE Karnofsky Performance Scale score of the 6 dogs that survived to discharge was 80 (range 60–90), and this score was improved over the pretreatment value in every case. Objective tumor responses were seen in 4 (80%) of 5 dogs with quantifiable target lesions. The median survival was 119 days (range 1 to > 940 days).

CONCLUSION

With the incorporation of additional therapeutic planning procedures, the NanoKnife system is a novel technology capable of controlled IRE ablation of telencephalic gliomas.

Canine brain tumours: a model for the human disease?

Canine brain tumours are becoming established as naturally occurring models of disease to advance diagnostic and therapeutic understanding successfully. The size and structure of the dog's brain, histopathology and molecular characteristics of canine brain tumours, as well as the presence of an intact immune system, all support the potential success of this model. The limited success of current therapeutic regimens such as surgery and radiation for dogs with intracranial tumours means that there can be tremendous mutual benefit from collaboration with our human counterparts resulting in the development of new treatments. The similarities and differences between the canine and human diseases are described in this article, emphasizing both the importance and limitations of canines in brain tumour research. Recent clinical veterinary therapeutic trials are also described to demonstrate the areas of research in which canines have already been utilized and to highlight the important potential benefits of translational research to companion dogs.

Molecular signalling pathways in canine gliomas

In this study, we determined the expression of key signalling pathway proteins TP53, MDM2, P21, AKT, PTEN, RB1, P16, MTOR and MAPK in canine gliomas using western blotting. Protein expression was defined in three canine astrocytic glioma cell lines treated with CCNU, temozolamide or CPT-11 and was further evaluated in 22 spontaneous gliomas including high and low grade astrocytomas, high grade oligodendrogliomas and mixed oligoastrocytomas. Response to chemotherapeutic agents and cell survival were similar to that reported in human glioma cell lines. Alterations in expression of key human gliomagenesis pathway proteins were common in canine glioma tumour samples and segregated between oligodendroglial and astrocytic tumour types for some pathways. Both similarities and differences in protein expression were defined for canine gliomas compared to those reported in human tumour counterparts. The findings may inform more defined assessment of specific signalling pathways for targeted therapy of canine gliomas.

Advances in diagnostic and treatment modalities for intracranial tumors

Intracranial neoplasia is a common clinical condition in domestic companion animals, particularly in dogs. Application of advances in standard diagnostic and therapeutic modalities together with a broad interest in the development of novel translational therapeutic strategies in dogs has resulted in clinically relevant improvements in outcome for many canine patients. This review highlights the status of current diagnostic and therapeutic approaches to intracranial neoplasia and areas of novel treatment currently in development.

A comparison of clinical, magnetic resonance imaging and pathological findings in dogs with gliomatosis cerebri, focusing on cases with minimal magnetic resonance imaging changes(‡)

The primary study objective was to determine whether clinical examination and magnetic resonance imaging (MRI) can underestimate canine gliomatosis cerebri (GC); we also investigated immunohistochemical features. Seven dogs with GC were studied; four recruited specifically because of minimal MRI changes. Neuroanatomic localization and the distribution of MRI, gross and sub-gross lesions were compared with the actual histological distribution of neoplastic cells. In six cases, clinical examination predicted focal disease and MRI demonstrated a single lesion or appeared normal. Neoplastic cells infiltrated many regions deemed normal by clinical examination and MRI, and were Olig2-positive and glial fibrillary acid protein-negative. Four dogs had concurrent gliomas. GC is a differential diagnosis for dogs with focal neurological deficits and a normal MRI or a focal MRI lesion. Canine GC is probably mainly oligodendrocytic. Type II GC, a solid glioma accompanying diffuse central nervous system neoplastic infiltration, occurs in dogs as in people.

Victory and defeat in the induction of a therapeutic response through vaccine therapy for human and canine brain tumors: a review of the state of the art

Anti-tumor immunotherapy using tumor lysate-based vaccines has made great advances over recent decades. Cancer vaccines aim to elicit adaptive immune responses through various pathways by providing tumor and tumor-associated antigens with an immune stimulant or adjuvant. These anti-tumor vaccines are therefore developed as personalized treatments. Utilizing tumors as a source of vaccine antigens in immunotherapy has demonstrated promising results with minimal toxicity. However, to date, researchers have failed to overcome the overpowering immune suppressive effects within the tumor microenvironment. Immune suppression occurs naturally via multiple mechanisms. These mechanisms serve an important homeostatic role restoring a normal tissue microenvironment following an inflammatory response. Due to these suppressive mechanisms and the inherent heterogeneity of tumors, it is imperative to then elicit and maintain a specific tumoricidal response if vaccine therapy or some other combination of reagents is chosen. In this review, we focus on the historical use of tumors as a source of antigens to elicit a tumoricidal response and the limitations encountered that prevent greater success in immunotherapy. We describe the advantages and disadvantages of various vaccines and their ineffectiveness due to tumor-induced immune suppression.

Diagnostic immunohistochemistry of canine and feline intracalvarial tumors in the age of brain biopsies

The focus of immunohistochemistry as applied to nervous system tumors is in identifying the neoplasm present and evaluating margins between normal and neoplastic tissue. Although not always utilized by specialists in neuropathology, immunohistochemistry remains useful to resolve concerns about the differentiation and rate of tumor growth. The aims of this review are to discuss the utility of immunohistochemical reagents currently used in diagnosis of canine and feline intracalvarial tumors, to indicate the applicability of some tests currently used in human nervous system tumors for domestic species, and to evaluate a few less commonly used reagents. A panel of biomarkers is usually needed to confirm a diagnosis, with groups of reagents for leptomeningeal, intraparenchymal, and ventricular neoplasms. In the future, signature genetic alterations found among feline and canine brain tumors--as correlated prospectively with diagnosis, rate of enlargement, or response to treatment--may result in new immunohistochemical reagents to simplify the task of diagnosis. Prospective studies determining the type and proportion of stem cell marker expression on patient longevity are likely to be fruitful and suggest new therapies. Due to increased frequency of biopsy or partial resection of tumors from the living patient, biomarkers are needed to serve as accurate prognostic indicators and assist in determining the efficacy of developing therapeutic options in nervous system tumors of dogs and cats.

ZIP4 is a novel molecular marker for glioma

BACKGROUND

Dysregulated zinc transport has been observed in many cancers. However, the status of zinc homeostasis and the expression profile of zinc transporters in brain and brain tumors have not been reported.

METHODS

The gene profiles of 14 zinc importers (ZIPs) and 10 zinc exporters (ZnTs) in patients with glioma were studied by investigating the association between the zinc transporters and brain tumor characteristics (tumor grade and overall survival time). Three independent cohorts were analyzed to cross-validate the findings: the Chinese Glioma Genome Atlas (CGCA) cohort (n = 186), the US National Cancer Institute Repository for Molecular Brain Neoplasia Data (REMBRANDT) cohort (n = 335), and The University of Texas (UT) cohort (n = 34).

RESULTS

The expression of ZIP3, 4, 8, 14, ZnT5, 6, and 7 were increased, and the expression of ZnT10 was decreased in grade IV gliomas, compared with grade II gliomas. Among all 24 zinc transporters, ZIP4 is most significantly associated with tumor grade and overall survival; this finding is consistent across 2 independent cohorts (CGCA and REMBRANDT) and is partially validated by the third cohort (UT). High ZIP4 expression was significantly associated with higher grade of gliomas and shorter overall survival (hazard ratio = 1.61, 95% confidence interval = 1.02-2.53, P = .040 in CGCA cohort; hazard ratio = 1.32, 95% confidence interval = 1.08-1.61, P = .007 in REMBRANDT cohort).

CONCLUSIONS

Dysregulated expression of zinc transporters is involved in the progression of gliomas. Our results suggest that ZIP4 may serve as a potential diagnostic and prognostic marker for gliomas.

Long-term follow-up of surgical treatment of spinal anaplastic astrocytoma in a cat

A 10-year-old spayed female chinchilla feline presented with gradually progressive tetraparesis and cervical pain that had begun 1 month before the onset of a 4-day tetraplegic episode. Magnetic resonance imaging revealed a large elliptical intramedullary mass at the fourth cervical vertebrae. The mass was removed surgically and diagnosed as an anaplastic astrocytoma. No neurological abnormalities were observed 3 weeks postsurgery. Magnetic resonance at 3.5 year follow-up revealed neither mass regrowth nor recurrence of signs.

Medium-grade astrocytoma in a cougar (Puma concolor)

A 17-year-old, male castrated cougar (Puma concolor) was presented minimally responsive and severely depressed, with bilateral mydriasis and absent pupillary light response. On gross examination of the brain, there was a tan-to-gray, invasive mass with a central cavitation on the ventral aspect in the left cerebral hemisphere, rostral to the caudate nucleus. On histopathologic examination, the mass was composed of sheets of medium-sized, round-to-polygonal cells that were multifocally separated by islands of neuropil. Approximately 80% of the neoplastic cells showed strong cytoplasmic labeling for glial fibrillary acidic protein. These findings were consistent with a medium-grade astrocytoma. To the authors' knowledge, neoplastic disease of the central nervous system has not been previously reported in cougars.

Identification of the rostral migratory stream in the canine and feline brain

In the adult rodent brain, neural progenitor cells migrate from the subventricular zone of the lateral ventricle towards the olfactory bulb in a track known as the rostral migratory stream (RMS). To facilitate the study of neural progenitor cells and stem cell therapy in large animal models of CNS disease, we now report the location and characteristics of the normal canine and feline RMS. The RMS was found in Nissl-stained sagittal sections of adult canine and feline brains as a prominent, dense, continuous cellular track beginning at the base of the anterior horn of the lateral ventricle, curving around the head of the caudate nucleus and continuing laterally and ventrally to the olfactory peduncle before entering the olfactory tract and bulb. To determine if cells in the RMS were proliferating, the thymidine analog 5-bromo-2-deoxyuridine (BrdU) was administered and detected by immunostaining. BrdU-immunoreactive cells were present throughout this track. The RMS was also immunoreactive for markers of proliferating cells, progenitor cells and immature neurons (Ki-67 and doublecortin), but not for NeuN, a marker of mature neurons. Luxol fast blue and CNPase staining indicated that myelin is closely apposed to the RMS along much of its length and may provide guidance cues for the migrating cells. Identification and characterization of the RMS in canine and feline brain will facilitate studies of neural progenitor cell biology and migration in large animal models of neurologic disease.

TP53 mutations in canine brain tumors

The p53 tumor suppressor gene (TP53) is the most frequently altered gene in human cancer. Mutation of the gene has been shown to be an important mechanism of p53 pathway inactivation in a variety of human brain tumors, particularly those of astrocytic origin. Genomic DNA from a series of 37 glial and 51 nonglial canine brain tumors was sequenced to determine the frequency of TP53 gene mutations involving exons 3-9. Exonic mutations were found in 3 of 88 tumors (3.4%) and specifically in 1 of 18 astrocytic tumors (5.5%). This is markedly lower than that reported in comparable human tumors, suggesting that alternative mechanisms of p53 inactivation are likely to be present if p53 function contributes significantly to oncogenesis in canine brain tumors.

Non-thermal irreversible electroporation (N-TIRE) and adjuvant fractionated radiotherapeutic multimodal therapy for intracranial malignant glioma in a canine patient

Non-thermal irreversible electroporation (N-TIRE) has shown promise as an ablative therapy for a variety of soft-tissue neoplasms. Here we describe the therapeutic planning aspects and first clinical application of N-TIRE for the treatment of an inoperable, spontaneous malignant intracranial glioma in a canine patient. The N-TIRE ablation was performed safely, effectively reduced the tumor volume and associated intracranial hypertension, and provided sufficient improvement in neurological function of the patient to safely undergo adjunctive fractionated radiotherapy (RT) according to current standards of care. Complete remission was achieved based on serial magnetic resonance imaging examinations of the brain, although progressive radiation encephalopathy resulted in the death of the dog 149 days after N-TIRE therapy. The length of survival of this patient was comparable to dogs with intracranial tumors treated via standard excisional surgery and adjunctive fractionated external beam RT. Our results illustrate the potential benefits of N-TIRE for in vivo ablation of undesirable brain tissue, especially when traditional methods of cytoreductive surgery are not possible or ideal, and highlight the potential radiosensitizing effects of N-TIRE on the brain.

Desmoplastic ganglioglioma of the spinal cord in a western European hedgehog (Erinaceus europaeus)

Gangliogliomas are composed of neoplastic glial and neuronal cells and are extremely rare tumors of the central nervous system of domestic animals. The present report describes the clinical presentation and the pathomorphological and immunophenotypical characteristics of a desmoplastic ganglioglioma in the spinal cord of a 3-year-old male western European hedgehog (Erinaceus europaeus). Clinically, the hedgehog exhibited a skin wound and therapy-resistant paresis of the left hind limb. Necropsy showed dilatation of the urinary bladder. Histologic examination of the thoracic spinal cord revealed a focally extensive infiltrative mass, which consisted of multiple nodules of smaller bipolar or oligopolar glial cells and variably sized polygonal, ganglionic, neuron-like cells embedded in variable amounts of microcystic neuropilic matrix. An area of spindle-shaped cells arranged in interwoven fascicles and surrounded by a prominent network of reticulin fibers was interpreted as desmoplastic leptomeningeal stroma. Immunohistochemistry revealed a moderate number of glial fibrillary acidic protein and S-100-positive cells and processes. In addition, the ganglionic neuron-like cells expressed neurofilament, microtubule-associated protein-2, and neuron-specific enolase. In summary, this spinal cord tumor was composed of astroglial and neuronal cellular elements, justifying the diagnosis of a desmoplastic ganglioglioma.