Somatostatin Receptor 2 Expression in Canine Meningioma

Expression of somatostatin receptors in canine and feline meningioma

OBJECTIVES

The standard treatment for canine and feline meningiomas includes radiotherapy, surgical excision or combined therapy. However, new therapeutic approaches are required due to the possible recurrence or progression of meningiomas despite initial therapy. Adjunctive therapy with synthetic long-acting somatostatin (SST) analogues has been described in humans with SST-expressing tumours. The expression of SST receptors (SSTRs) by feline meningiomas is currently unknown, and there are little data about canine meningiomas. We hypothesized that SSTR is expressed by canine and feline meningiomas (S1).

METHODS

Seven canines and 11 felines with histologically confirmed meningiomas underwent STTR screening. RNA expressions of SSTR1, SSTR2, SSTR3 and SSTR5 (canine) and SSTR1-SSTR 5 (feline) in fresh frozen and formalin-fixed and paraffin-embedded (FFPE) samples were investigated using real-time (RT)-qPCR. The expression of SSTR1 and SSTR2 in FFPE samples was evaluated using immunohistochemistry (IHC). The specificity of applied antibodies for canine and feline species was confirmed by western blotting.

RESULTS

In canine meningiomas (n = 7), RNA expression of SSTR1, SSTR2 and SSTR5 was detected in all samples; SSTR3 RNA expression was detected in only 33% of samples. In feline meningiomas (n = 12), RNA expression of SSTR1, SSTR4, SSTR5 and SSTR2 was detected in 91%, 46%, 46% and 36% of samples, respectively; SSTR3 was not expressed. Overall, the detection rate was lower in FFPE samples. IHC revealed the expression of SSTR1 and SSTR2 in all samples from both species. However, it is important to exercise caution when interpreting IHC results due to the presence of diffuse background staining.

CONCLUSIONS

SSTRs are widely expressed in canine and feline meningiomas, thereby encouraging further studies investigating SSTR expression to conduct trials about the effect of adjunctive therapy with long-acting SST-analogues.

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.

Cytotoxicity on low-grade canine meningioma with the use of somatostatin analog (octreotide): An in vitro study

Background

Meningioma is the most common tumor of the central nervous system of dogs. For this tumor, surgery remains the treatment of choice, either alone or in combination with radiotherapy. Unfortunately, chemotherapeutic strategies are practically absent in dogs and palliative therapies are the only option to surgery. Somatostatin receptor subtype 2 (SSTR2) is expressed in canine meningioma. Since the potent cell-proliferation inhibiting effect of somatostatin (SST), the aim of this study was to investigate in vitro the effects of octreotide, as SST analog, in the viability of canine meningioma.

Methods

Four surgical canine meningiomas were used in this study to establish cell cultures. Expression of SSTR2 was verified with immunolabelling in FFPE samples and cell cultures. The effects of octreotide on cell viability were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). After 24 hours they were exposed to different concentrations of octreotide (0.1 nM, 1 nM, 10 nM, 100 nM) for 24 and 48 hours.

Results

All meningiomas consisted of grade I tumors. The cultured neoplastic cells expressed SSTR2 from 80% to 100%. Octreotide significantly increased cell death after 48 hours of continuous exposure, with 10 and 100 nM octreotide doses. The percentage of cell viability was 80.92 ± 4.9 and 80.49 ± 3.61, compared to the control, respectively, consistent with decreased cell viability of about 20% for both doses.

Conclusions

Octreotide reduced the alive neoplastic cultured cells of low-grade canine meningioma in a dose-dependent pattern with continuous exposition for 48 hours. These results support an alternative systemic treatment of meningioma with octreotide in the dog.

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.

Meningothelial hamartoma on the forehead of a young cat

A 1 year and 2-months-old neutered male cat underwent surgical resection of a cutaneous nodule on the midline of the forehead that had been present since approximately 6 months of age. Histopathologically, the nodule was composed of interlacing collagenous fibres interspersed with varying numbers of spindloid cells with round to oval nuclei and moderate to abundant amounts of pale eosinophilic cytoplasm. Similar to meningothelial cells, the spindloid cells were immunopositive for vimentin, neuron-specific enolase, E-cadherin and somatostatin receptor 2. Based on these findings and the absence of nuclear atypia and mitotic figures, the nodule was diagnosed as meningothelial hamartoma. Although cases of cutaneous meningioma have been reported, this is the first report of meningothelial hamartoma in a domestic animal.

Biodistribution of 18F-AlF-NOTA-octreotide in Different Organs and Characterization of Uptake in Neuroendocrine Neoplasms

PURPOSE

The aims of this study were threefold: [1] to describe the biodistribution of ¹⁸F-AlF-NOTA-octreotide (¹⁸F-OC) in normal organs; [2] to evaluate the range of uptake of NEN and benign lesions using the maximum standardized uptake value (SUV_max); and [3] to compare the difference in ¹⁸F-OC uptake among tumors of different grades.

METHODS

This study included 162 patients (67 females and 95 males) who received ¹⁸F-OC positron emission tomography (PET)/computed tomography (CT), 128 of whom were diagnosed with neuroendocrine neoplasms (NENs). The SUV_max and SUV_mean of ¹⁸F-OC were measured in 21 normal anatomical structures. We compared the differences among G1, G2, and G3 NENs, as well as between NENs and benign lesions.

RESULTS

High physiological uptake of ¹⁸F-OC (SUV_max > 6.77) was detected in the spleen, adrenal gland, renal parenchyma, pituitary gland, and liver. Moderate uptake (SUV_max 3.00-6.77) was found in the uncinate process of the pancreas (PU), prostate, thyroid, and uterus. Mild uptake (SUV_max 1.34-3.00) was observed in the small intestine, pancreas (pancreas uptake except for the head of the pancreas), gallbladder, and transverse colon. The SUV_max of NENs was higher than that of benign lesions, including fractures, inflamed tissue, reactive hyperplasia, and degenerative disease. However, overlap was noted between the two groups. The SUV_max of ¹⁸F-OC uptake by tumors was significantly correlated with tumor grade in primary lesions and those of the lymph node, bone, and other sites (all P < 0.01).

CONCLUSIONS

The results obtained from the majority of the samples in this study show the biodistribution of ¹⁸F-OC in normal organs and have significance as a reference. Although some benign lesions show variable uptake, the uptake by these lesions is still different from that of NENs. NENs of different grades have differences in ¹⁸F-OC uptake levels.

Do Canine Pancreatic Neuroendocrine Neoplasms Resemble Human Pancreatic Neuroendocrine Tumours? A Comparative Morphological and Immunohistochemical Investigation

Although canine pancreatic neuroendocrine neoplasms (PanNENs) have been proposed as a model for the counterpart human neoplasms, the type or grade of human PanNEN that they resemble is unclear. PanNENs in animals are classified as adenoma or carcinoma, whereas in humans they are classified as pancreatic neuroendocrine tumour (PanNET) if well-differentiated, or as pancreatic neuroendocrine carcinoma (PanNEC) if poorly differentiated. We evaluated 16 canine primary PanNENs and two metastases histologically and immunohistochemically, and graded them using the animal and human grading systems. All neoplasms had local or vascular invasion and were classified as pancreatic islet cell carcinomas according to the current WHO classification. The Ki-67 index was low in all cases (0.01-1.50%). All had cytoplasmic expression of synaptophysin and insulin but were immunonegative for glucagon, confirming a functional diagnosis of canine insulinoma. Membranous expression of SSTR2A and nuclear expression of ATRX, but no p53 expression, was found in all neoplasms. One primary tumour was diagnosed as a mixed neuroendocrine-non-neuroendocrine neoplasm, which is the first report of this neoplasm in dogs. The other 15 primary tumours and both metastatic tumours were graded as PanNET G1, according to the human WHO classification. We conclude that canine PanNENs share well-differentiated histomorphology, SSTR2A expression and absence of nuclear p53 immunolabelling with human PanNETs G1. However, they differ in ATRX gene expression and functionality, and seem to have a worse prognosis than human PanNETs G1, although their generally low Ki-67 index precludes more precise assessment of prognosis. Membranous SSTR2A expression renders canine PanNENs potentially amenable to treatment with somatostatin analogues or SSTR targeted in-vivo imaging methods.

Immunoexpression of epithelial membrane antigen in canine meningioma: Novel results for perspective considerations

Epithelial membrane antigen (EMA) is one of the most widely used diagnostic immunohistochemical markers for human meningioma. To date, no published study on EMA expression in formalin-fixed paraffin-embedded (FFPE) tissue samples of canine meningioma is available. Here, we describe the results of an immunohistochemical study on 25 FFPE canine meningiomas using a monoclonal anti-human EMA antibody. All meningiomas showed positive staining for EMA with cytoplasmic pattern, in nine cases associated with membranous staining. Area and intensity of staining were highly variable among cases. No clear relationships between tumour subtype/grade and area/intensity of staining were found. However, epithelial-like patterns showed a higher affinity for EMA compared to the mesenchymal one. The present study provides the basis to explore the potential diagnostic application of this marker in canine meningioma. To investigate EMA expression in other central nervous system tumours of dogs are necessary to assess the specificity of this marker.

An Overview of Managements in Meningiomas

Meningioma is the most frequent primary tumor of the central nervous system. Important advances have been achieved in the treatment of meningioma in recent decades. Although most meningiomas are benign and have a good prognosis after surgery, clinicians often face challenges when the morphology of the tumor is complicated or the tumor is close to vital brain structures. At present, the longstanding treatment strategies of meningioma are mainly surgery and radiotherapy. The effectiveness of systemic therapy, such as chemotherapy or targeted therapy, has not been confirmed by big data series, and some clinical trials are still in progress. In this review, we summarize current treatment strategies and future research directions for meningiomas.

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.