Evaluation of progesterone and estrogen receptor expression in 15 meningiomas of dogs and cats

OBJECTIVE: To evaluate progesterone and estrogen receptor expression in meningiomas of the CNS in dogs and cats. ANIMAL: 8 dogs (1 of which was treated with gestrinone) and 5 cats with intracranial meningiomas and 2 dogs with spinal cord meningiomas; tissue samples were also obtained from 1 clinically normal dog and 1 clinically normal cat. PROCEDURE: Meningioma tissue was obtained during surgery or at necropsy; samples were processed for histologic classification and immunohistochemical evaluation of the proportion of tumor cells with progesterone and estrogen receptors. Correlation among receptor expression, tumor grade, and histologic subtypes was determined. RESULT: Several histologic subtypes of intracranial meningiomas were detected among tissue samples. In the cats, all intracranial meningiomas were benign. Progesterone receptor immunoreactivity was detected in 14 of 15 meningiomas. Progesterone receptor expression was identified in > 80% of cells in 8 intracranial meningiomas (4 dogs and 4 cats) and 2 spinal cord meningiomas. In samples of malignant transitional and granular cell meningiomas in dogs, progesterone receptors were detected in 32 and 4.8% of cells respectively. In 1 cat, 38% of tumor cells had progesterone receptors. In a dog treated with gestrinone, no progesterone receptors were detected in the intracranial meningioma. Estrogen receptors were only detected in the tumor of 1 dog. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate a high proportion of progesterone receptors in cells of meningiomas of the CNS in dogs and cats. Antiprogesterone treatment may have a role in the treatment of unresectable or recurrent meningiomas in dogs and cats.     

Telomerase enzyme activity as a diagnostic tool to distinguish effusions of malignant and benign origin

Telomerase enzyme activity is high in populations of cells that are dividing, and is low or undetectable in quiescent cell populations. Activation of telomerase in tissues that normally lack the capacity for self-renewal is strongly correlated with neoplasia. Telomerase activity can be detected in samples containing very small numbers of cells and studies of human patients suggest that measurement of telomerase activity may be useful for the evaluation of samples that can be obtained in a minimally invasive manner. This study compares the presence or absence of telomerase activity with cytologic evaluation of body cavity effusions, to determine if neoplasia is the underlying cause for the effusion in dogs and cats. Detection of telomerase in effusions was no more sensitive than cytologic evaluation for the identification of underlying neoplasia, and was less specific (telomerase assay: sensitivity = 50%, specificity = 83%; cytology: sensitivity = 50%, specificity = 100%). We conclude that although the telomerase assay may constitute a useful adjunctive test for the diagnosis of neoplasia in some dogs and cats with body cavity effusions, the results of this assay are not sufficiently reliable to be used as a sole diagnostic test.     

THE DURAL TAIL SIGN IN THE DIAGNOSIS OF MENINGIOMAS

In humans the dural tail is a sign seen on contrast enhanced T1 weighted magnetic resonance images. This finding is considered specific for meningioma. The purpose of this study was to determine how often the dural tail occurs in cats and dogs and whether it is a specific sign for meningiomas in these species. MR examinations for eighteen dogs and four cats with proven diagnoses were reviewed. Diagnoses included ten meningiomas (seven dogs and three cats), three gliomas, two pituitary tumors, single examples of two other tumor types and five patients with mass lesions due to inflammatory disease. Contrast enhanced T1 weighted images were evaluated independently by three of the authors for the presence of a dural tail, without knowledge of the diagnoses. The results were compared to the diagnosis for each patient and the performance of individual reviewers compared. When their results were averaged, the reviewers reported the presence of a dural tail in 6 of 10 (60%) meningiomas, although detection varied between observers from 40% to 80%. Each reviewer had one false positive result, two reported a dural tail with a chromophobe adenocarcinoma and one with a toxoplasma meningoencephalitis. When a dural tail is seen an associated mass is most likely a meningioma. It is uncertain whether the dural tail represents neoplastic infiltration beyond the margins of the meningioma. This should be considered when planning treatment.     

Vascular endothelial growth factor expression in canine intracranial meningiomas and association with patient survival

BACKGROUND: Vascular endothelial growth factor (VEGF) is a regulator of angiogenesis and vascular permeability. In human patients with meningiomas, increased VEGF expression is predictive of postsurgical recurrence. The objectives of this study were to evaluate VEGF expression in canine intracranial meningiomas and to determine whether an association between VEGF expression and patient survival existed. METHODOLOGY: Tumor tissue from 17 dogs with histologically confirmed intracranial meningiomas was obtained surgically. All dogs then were treated with radiotherapy. Immunohistochemistry was performed on 5-microm sections of paraffin-embedded tumor tissue with rabbit anti-human VEGF polyclonal antibody. The extent, intensity, and distribution of VEGF staining for each section were assessed with light microscopy by means of a semiquantitative scale. Survival was analyzed by the Kaplan-Meier procedure. Survival rates among groups were compared by log-rank tests with the significance set at P < or = .05. FINDINGS: VEGF expression was detected in all tumors, with >50% of cells staining positively in tissues from 15/17 dogs. Shorter survival times were associated with greater VEGF expression (P = .01). CONCLUSIONS: VEGF expression can be measured in canine intracranial meningiomas and may be associated with poor outcome. SIGNIFICANCE: The extent of VEGF expression in canine intracranial meningiomas may be used as a prognostic marker and suggests a potential future target for therapy.     

Thiopurine methyltransferase in red blood cells of dogs, cats, and horses

Our objective was to determine if thiopurine methyltransferase (TPMT), the enzyme important in the metabolism of azathioprine in human beings, is detectable in red blood cell lysates (RBCL) of healthy dogs, cats, and horses. Values for TPMT activity were determined from blood collected from 20 healthy dogs, cats, and horses. The TPMT activity in each animal's RBCL was determined using a radioenzymatic end point involving TPMT-facilitated metabolism of 6-mercaptopurine to 6-methylmercaptopurine (6-MMP). One unit of TPMT activity represents the formation of 1 nmol of 6-MMP per milliliter of packed red blood cells per hour of incubation at 37 degrees C. TPMT activity in RBCL was detectable in all species, with mean RBC values +/- standard deviation of 17.9 +/- 3.79 U/mL in dogs; 2.76 +/- 0.70 U/mL in cats; and 2.185 +/- 0.36 U/mL in horses. Values for TPMT in the 3 species were significantly (P < .05) different from one another. TPMT values for dogs were significantly higher than the other species, and TPMT values for cats were significantly higher than those for horses. We conclude that RBCL TPMT values are measurable in dogs. cats, and horses and that dogs have higher values than cats or horses. These findings are consistent with the lower tolerance for azathioprine in cats as compared with dogs. It remains to be determined whether RBCL TPMT values in these species correlate with TPMT activity in the liver, where most of the metabolization of azathioprine is believed to occur.     

Telomerase activity as a marker for malignancy in feline tissues

OBJECTIVE: To establish the diagnostic significance of the telomeric repeat amplification protocol (TRAP) assay in detecting feline malignancies. SAMPLE POPULATION: Solid tissue specimens collected from 33 client-owned cats undergoing diagnostic or therapeutic procedures at the University of Illinois Veterinary Medical Teaching Hospital between July 1997 and September 1999 and an additional 20 tissue samples were collected from 3 clinically normal control cats euthanatized at the conclusion of an unrelated study. PROCEDURE: The TRAP assay was used for detection of telomerase activity. Each result was compared to its respective histopathologic diagnosis. RESULTS: Twenty-nine of 31 malignant and 1 of 22 benign or normal tissue samples had telomerase activity, indicating 94% sensitivity and 95% specificity of the TRAP assay in our laboratory. CONCLUSIONS AND CLINICAL RELEVANCE: The diagnostic significance of telomerase activity has been demonstrated in humans and recently in dogs by our laboratory. We tested feline samples to determine whether similar patterns of telomerase activity exist. On the basis of our results, the TRAP assay may be clinically useful in providing a rapid diagnosis of malignancy in cats. The telomerase enzyme may also serve as a therapeutic target in feline tumors.     

Mucosal defence along the gastrointestinal tract of cats and dogs

Diseases that are associated with infections or allergic reactions in the gastrointestinal and respiratory tracts are major causes of morbidity in both cats and dogs. Future strategies for the control of these conditions require a greater understanding of the cellular and molecular mechanisms involved in the induction and regulation of responses at the mucosal surfaces. Historically, the majority of the fundamental studies have been carried out in rodents or with tissues obtained from man, but the expanding range of reagents available for the study of farm and companion animals provides opportunities for study in a wider range of animals including cats and dogs. To date, these studies have tended to be focussed on characterising the cellular distributions in healthy animals and in groups of cats and dogs identified as having an increased risk of mucosal disturbance. Where species comparisons of mucosal immune systems have been made, the results have tended to be divided between monogastric and ruminant animals. It is then not surprising that the mucosal immune systems of both cats and dogs bear greatest similarity to that documented for man and pigs. For example, IgA is the dominant immunoglobulin in mucosal secretions of cats and dogs and oral tolerance can be induced following the introduction of novel antigens into the diet. Also like several other species, cats become transiently hypersensitive to the newly introduced dietary antigen prior to the establishment of tolerance. In contrast, there are a number of potentially important differences. In particular, there are significant differences between cats and dogs in the expression MHC class II molecules on gut epithelial cells. Similarly, it has been reported that cats have elevated numbers of intraepithelial lymphocytes (IEL) and that a proportion of these express surface IgM. It remains to be determined if these differences reflect the way in which the animals are maintained and if they may have greater biological significance.     

Characteristics of cisternal cerebrospinal fluid associated with intracranial meningiomas in dogs: 56 cases (1985-2004)

OBJECTIVE: To determine CSF characteristics associated with intracranial meningiomas in dogs. DESIGN: Retrospective case series. ANIMALS: 56 dogs with intracranial meningiomas. PROCEDURES: Medical records of dogs with a histopathologic diagnosis of intracranial meningioma, in which CSF analysis had been performed, were reviewed. Information concerning total nucleated cell counts (TNCCs) and differential nucleated cell counts, RBC counts, and total protein concentration in CSF; seizure history and glucocorticoid administration; and location of meningiomas was recorded. RESULTS: TNCCs < 5 cells/microL were detected in 41 of 56 (73%) dogs; 5 of 56 (9%) dogs had TNCCs > 50 cells/microL. Analysis of CSF revealed predominantly neutrophilic pleocytosis in < 20% of dogs. There was a significant association between meningioma location (caudal portion of the cranial fossa or middle and rostral portion of the cranial fossae) and increased TNCCs (> or = 5 cells/microL). CONCLUSIONS AND CLINICAL RELEVANCE: Results were significantly different from those routinely reported in the veterinary literature. Neutrophilic pleocytosis, especially with TNCCs > 50 cells/microL, was not typical in CSF samples from dogs with intracranial meningiomas. Neutrophilic pleocytosis may not be detected in CSF samples from dogs with meningiomas located within the middle or rostral portion of the cranial fossae.     

Canine and feline intracranial meningiomas: an updated review

Meningiomas are the most common primary brain tumours in dogs and cats. There are several morphological phenotypes of this extra-axial neoplasm and they show predilections for certain anatomical locations. There have been a number of attempts to apply the current World Health Organization (WHO) classification for human meningiomas to dogs and cats and to obtain a universal classification scheme for domestic animals. Recently, certain enzymes involved in tumour growth have been recognised as biological markers and have been related to degrees of malignancy. The secondary effects of meningiomas have also been investigated, and vascular endothelial growth factor and peritumoural oedema have been reported to reduce survival rate. Breed and age predisposition are recognised in both dogs and cats and the presenting clinical signs are quite consistent. Magnetic resonance imaging and computed tomography are the techniques of choice for the presumptive diagnosis of meningiomas in domestic animals but advanced imaging techniques are constantly being developed and applied. Treatment methods for meningiomas involve a combination of de-bulking surgery, chemotherapy and radiotherapy, and detailed accounts of several treatment protocols have been reported.     

Resident forum abstractsEVALUATION OF THROMBOELASTOGRAPHY (TEG) IN NORMAL CATS

Objective: To establish normal parameters of thromboelastography (TEG) in healthy adult cats. Background: Thromboelastography (TEG) is an in vitro test of coagulation that has been shown to be useful in humans, dogs and select species to identify and quantify alterations of hemostasis (e.g., hypercoagulable and hypocoagulable states). It has also been demonstrated to be useful in monitoring effects of anticoagulant therapies. This test has not been evaluated in cats. Methods: Blood was collected from 25 clinically normal cats by venipuncture using a 21 gauge×3 1/2 inch butterfly catheter and syringe for medial saphenous or jugular venipuncture. A single 1.8 mL sample in 3.8% Sodium Citrate (9:1) was collected from each cat. Recalcified whole blood was analyzed 30 minutes following collection with the TEG® 5000 analyzer (Haemoscope, Niles, IL). Analysis temperature was 37.6°C. TEG parameters recorded included: R‐value (represents initial fibrin formation), K (time from R to standard fixed measure of clot firmness which represents contributions of platelets and fibrinogen), maximum amplitude (MA; represents absolute clot strength), and alpha angle (α; the slope of TEG tracing which represents rate of clot formation). The coagulation index (CI) was derived from the formula generated for humans to provide an overall assessment of whether the sample was hyper‐ or hypocoagulable. Results: Values for the 25 normal cat samples are reported as mean ±2 standard deviations. R=2.97; 1.23–4.72; K=1.54, 0.38–2.71; α=70.70, 57.76–83.65; MA=58.50, 45.26–71.74 and CI=2.27, 0.07–4.46. Compared to historical information obtained on normal dogs, cats have significantly shorter R and K and larger α, MA and CI. Conclusions: TEG does have reproducible performance when used to evaluate coagulation status in normal cats. Compared to dogs, normal cats favor a hypercoagulable state. Species‐specific normal values are necessary for interpretation of TEG results. This test bears potential value for use in future experimental and clinical work to investigate hemostasis in cats receiving anticoagulant therapies or in cats suffering from diseases such as cardiomyopathy which are thought to be associated with altered coagulation status.     

A cohort study of telomere and telomerase biology in cats

OBJECTIVE: To investigate telomere lengths in tissues of domestic shorthair (DSH) cats of various ages, evaluate the relationship between telomere length and age of cats, and investigate telomerase activity in the somatic tissues of cats. SAMPLE POPULATION: Tissues obtained from 2 DSH cats and blood samples obtained from 30 DSH cats. PROCEDURE: DNA isolated from blood cells and somatic tissue samples was subjected to terminal restriction fragment (TRF) analysis to determine mean telomere repeat lengths. Protein samples were subjected to analysis by use of a telomeric repeat-amplification protocol to assess telomerase activity. RESULTS: MeanTRF values of cats ranged from 4.7 to 26.3 kilobase pairs, and there was significant telomeric attrition with increasing age of cat. Telomerase activity was not found in a wide range of normal tissues obtained from 2 cats. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of these results clearly indicates that telomeres are shorter in older cats, compared with young cats; therefore, telomeres are implicated in the aging process. The analysis of telomerase activity in normal somatic tissues of cats reveals a pattern of expression similar to that found in human tissues. IMPACT FOR HUMAN MEDICINE: Fundamental differences in the biological characteristics of telomeres and telomerase exist between humans and the other most widely studied species (ie, mice). The results reported here reveal similarities in telomere and telomerase biologic characteristics between DSH cats and humans. Hence, as well as developing our understanding of aging in cats, these data may be usefully extrapolated to aging in humans.     

Practical management of obesity in dogs and cats

Obesity is the most common form of malnutrition encountered in small animal practice in the western world. In a survey of cats presented to the author's clinic, 40 per cent were overweight or obese; the incidence of obesity was highlighted in neutered cats, those that were kept indoors and those over 36 months of age. A number of clinical conditions of dogs and cats can be associated with obesity, therefore its prevention and control represents an important challenge for the small animal veterinarian and its success is largely dependent on effective client education. Treatment of obesity involves a suitable diet formulation and continual patient monitoring to maintain the owner's enthusiasm and cooperation. Commercial low calorie diets provide an effective and convenient means of weight loss in obese dogs and cats.     

Ki-67 and Vascular Endothelial Growth Factor Expression in Intracranial Meningiomas in Dogs

Background: Tumor proliferation in human intracranial meningiomas can be defined by the reactivity of the monoclonal antibody MIB-1 to the Ki-67 antigen. Vascular endothelial growth factor (VEGF), a pro-angiogenic factor, is a predictive marker for survival of dogs with intracranial meningiomas.
Hypothesis: Ki-67 is expressed in canine intracranial meningiomas and is associated with VEGF expression. Ki-67 expression is a prognostic marker for patient outcome.
Animals: Seventy client-owned dogs with WHO grade I intracranial meningiomas.
Methods: Retrospective study assessing the degree of immunostaining for Ki-67 by MIB-1 and VEGF expression in intracranial meningioma tissue from dogs. MIB-1 Labeling Index (LI) was calculated with Image J NIH-software. Extent, intensity, and distribution of VEGF-expression was assessed semiquantitatively. Cross tabulations with Fisher's exact tests and nonparametric Spearman's rank correlations were performed to identify associations between VEGF expression and MIB-1 LI. Fifteen dogs underwent postsurgical radiotherapy and were included in survival analysis. The effect of MIB-1 LI on survival was examined by Kaplan-Meier and Cox proportional hazards regression procedures.
Results: Ki-67 staining was positive in 91% (64/70) and VEGF expression was detected in 96% (67/70). There was no significant association between VEGF expression and MIB-1 LI. MIB-1 LI was not associated with survival.
Conclusions and Clinical Importance: MIB-1 antibody can be used to document cell proliferation in intracranial meningiomas in dogs, but does not predict outcome. No association between VEGF as a marker of angiogenesis and tumor proliferation was found. Angiogenesis might be a more important predictor of meningioma activity in dogs than is Ki-67.     

Evaluation of telomerase-targeted therapies in canine cancer cell lines

Despite advances in conventional therapeutics, cancer remains an invariably fatal disease, the major challenge being to develop tumour‐specific cancer treatment strategies. Current treatments such as chemotherapy and radiotherapy rely on a crude distinction between cancer cells and normal cells. However, with an increased understanding of the molecular events in the development of cancer, it is possible that far more innovative and targeted approaches can be developed. From studies on humans and dogs, the enzyme telomerase has emerged as a central unifying mechanism underlying the immortal phenotype of cancer and has thus become a candidate for differentiating between normal and cancer cells. The level and frequency of telomerase activity and component gene expression in cancers reinforces this as a potential target for cancer therapies. This article describes two approaches to target cancer by capitalizing on the expression of this enzyme. In the first approach, we target the enzyme itself, the goal being to cause cancer cell death. In the second approach, we utilize the respective gene promoters for telomerase component enzymes to drive expression of a reporter gene in cancer cell lines. The results demonstrated that targeted gene expression using promoter elements can be achieved specifically in telomerase‐positive cell lines. However, targeting the enzyme itself proved less successful and warrants investigations into alternative approaches.     

Expression of receptor activator of nuclear factor kappa-B ligand (RANKL) in neoplasms of dogs and cats

BACKGROUND: Receptor activator of nuclear factor kappa-B (RANK), RANK-ligand (RANKL), and the soluble decoy receptor osteoprotegerin (OPG) form a key axis modulating osteoclastogenesis. In health, RANKL-expressing bone stromal cells and osteoblasts activate osteoclasts through RANK ligation, resulting in homeostatic bone resorption. Skeletal tumors of dogs and cats, whether primary or metastatic, may express RANKL and directly induce malignant osteolysis. HYPOTHESIS: Bone malignancies of dogs and cats may express RANKL, thereby contributing to pathologic bone resorption and pain. Furthermore, relative RANKL expression in bone tumors may correlate with radiographic characteristics of bone pathology. ANIMALS: Forty-two dogs and 6 cats with spontaneously-occurring tumors involving bones or soft tissues were evaluated. METHODS: A polyclonal anti-human RANKL antibody was validated for use in canine and feline cells by flow cytometry and immunocytochemistry. Fifty cytologic specimens were collected from bone and soft tissue tumors of 48 tumor-bearing animals and assessed for RANKL expression. In 15 canine osteosarcoma (OSA) samples, relative RANKL expression was correlated with radiographic characteristics of bone pathology. RESULTS: Expression of RANKL by neoplastic cells was identified in 32/44 canine and 5/6 feline tumor samples. In 15 dogs with OSA, relative RANKL expression did not correlate with either radiographic osteolysis or bone mineral density as assessed by dual energy x-ray absorptiometry. CONCLUSIONS AND CLINICAL IMPORTANCE: In dogs and cats, tumors classically involving bone and causing pain, often may express RANKL. Confirming RANKL expression in tumors is a necessary step toward the rational institution of novel therapies targeting malignant osteolysis via RANKL antagonism.     

Use of urine albumin/creatinine ratio for estimation of proteinuria in cats and dogs

The clinical utility of the urine albumin/creatinine ratio (UAC) using a simplified analyzer for estimation of proteinuria was studied in cats and dogs. Measurement results for diluted feline and canine albumin standard solutions showed linearity. Although conversion formulas (y=1.28x+1.04 and y=1.67x+10.47 for cats and dogs, respectively) were necessary, urine albumin concentrations could be determined in both animals. In cats and dogs with proteinuria, the UAC changed parallel with the urine protein/ creatinine ratio (UPC), and the Log UAC and Log UPC were significantly correlated (r=0.803 (p<0.01) in cats, r=0.801 (p<0.01) in dogs). The UAC using an UAC analyzer could be used clinically as one of the basic in-hospital laboratory tests for estimation of proteinuria in cats and dogs.     

Surgical treatment and radiation therapy of frontal lobe meningiomas in 7 dogs

The cases of 7 adult dogs with generalized seizures managed by surgical excision and radiation therapy for frontal lobe meningiomas were reviewed. The neurological examination was unremarkable in 6 of the 7 dogs. Five dogs were operated on using a bilateral transfrontal sinus approach and 2 using a unilateral sinotemporal approach to the frontal lobe. One dog was euthanized 14 d after surgery; radiation therapy was initiated 3 wk after surgery in the remaining 6 dogs. Long-term follow-up consisted of neurological examination and magnetic resonance imaging (MRI) and/or computed tomography (CT) scan after radiation therapy. The mean survival time for dogs that had surgery and radiation therapy was 18 mo after surgery. Frontal lobe meningiomas have been associated with poor prognosis. However, the surgical approaches used in these cases, combined with radiation therapy, allow a survival rate for frontal lobe meningiomas similar to that for meningiomas located over the cerebral convexities.     

Surgical approach for tentorial meningiomas in cats: a review of six cases

The surgical technique for removal of tentorial meningiomas is described on six cats using a unilateral temporal supracerebellar transtentorial approach. Complete gross tumour resection was achieved in four of six cats. In one cat, only subtotal resection was achieved. One cat died shortly after surgery because of extensive cerebral haemorrhage. The surgical approach, combined with cisternal or ventricular cerebrospinal fluid puncture and an open-window technique (tumour fenestration and enucleation) provided sufficient visibility and tumour accessibility without excessive manipulation of the brain parenchyma. In all patients, a postoperative transient worsening of the clinical signs was observed. The neurological signs resolved with time with the exception of blindness in two cats. All five surviving cats were monitored for a mean follow-up time of 19 months (median 20 months; range 6-30 months). All patients died or were euthanased because of tumour regrowth within the follow-up period. Although challenging, surgical treatment is a useful therapeutic measure in the treatment of cats presenting with tentorial meningiomas.     

Intracranial meningioma: a comparative pathologic study of 28 dogs

Intracranial meningiomas were identified in 28 dogs based on histologic examination of tissue. The average age of the dogs was 11 years, and 83% (20/24) were 10 years old or older. German shepherd and mixed breed were most common (31% each, 8/26). Grossly, meningiomas were oval, dome-shaped and flattened masses adherent to the dura and compressing the brain. Forty-eight percent (15/26) of the tumors affected the dorsal surface of the brain, and two thirds of these were located in the anterior half. Histologically, tumor types were transitional (13), meningotheliomatous (11), angioblastic (three), and fibroblastic (one). There was direct invasion of the brain in 27% (6/22) although we observed neurologic signs and pathologic changes in 88% (23/26) and 90% (18/20) of the dogs, respectively. Intracranial meningioma can be compared and contrasted with this tumor in man and cats.