Cyclooxygenase-2 Expression in Canine Appendicular Osteosarcomas

A dog with extraskeletal osteosarcoma of the salivary glands survived long-term, following surgical resection and adjuvant therapy

A 12-year-old French bulldog presented with a mass on the right lower jaw. Computed tomography revealed that the mass originated from the salivary gland and was not continuous with the right mandible. The mass was surgically removed and subsequently diagnosed as extraskeletal osteosarcoma of the salivary gland following histopathological and immunohistochemical examinations. Although the surgical margin was clear, postoperative adjuvant therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) was initiated. Lung metastasis was observed 249 days after the initial examination; therefore, toceranib was initiated with NSAIDs. The dog died 496 days after the initial examination of this disease progression but had good long-term management with a combination of surgery, NSAIDs, and toceranib.

First study on the immunohistochemical expression of cyclooxygenase-2 and clinicopathological association in canine hepatoid gland neoplasms

Background and Aim: Hepatoid gland neoplasms (HGNs) constitute one of the most common cutaneous tumors that arise from perianal glands in dogs and are clinically characterized by rapid growth. Cyclooxygenase-2 (COX-2), the inducible form of the enzyme, is associated with several hallmarks of tumorigenesis. Its expression has been confirmed in several human and animal neoplastic tissues, but there are no reports in hepatoid gland tissues. Therefore, this study aimed to investigate COX-2 immunoexpression in canine HGNs, compare the expression among groups of normal hepatoid glands, hepatoid gland adenomas (HGAs), hepatoid gland epitheliomas (HGEs), and hepatoid gland carcinomas (HGCs), and assess the association of the COX-2 expression with clinicopathological features. Materials and Methods: Sixty-one formalin-fixed paraffin-embedded canine hepatoid gland tissues (20 samples of HGAs, 16 of HGEs, 15 of HGCs, and 10 of normal hepatoid glands) were analyzed for COX-2 expression using immunohistochemistry with scoring for percentage positivity and intensity. Multiple comparisons of COX-2 expression among normal and neoplastic hepatoid glands and the associations between COX-2 expression and clinicopathological features were analyzed. Results: Cyclooxygenase-2 expression was not detected in 60% of normal hepatoid glands and 25% of HGAs. Seventy-five percent of HGAs had a weak expression, while 43.7% and 56.3% of HGEs showed weak and moderate expression, respectively. The expression of HGCs ranged from weak (13.3%) to moderate (33.3%) and strong (53.3%). The immunoreactivity score of COX-2 labeling was significantly different among the normal and neoplastic hepatoid glands (p < 0.0001). The highest score was observed in the HGCs. Only in HGCs, the strong COX-2 expression was significantly associated with some clinicopathological features, including tissue invasion (p = 0.007) and necrosis (p = 0.029). Conclusion: These results suggest that COX-2 may play a role in the modulation of neoplastic cell growth. These preliminary data lead to further investigation on the potential of COX-2 expression as a prognostic indicator and COX-2 inhibitors for canine HGCs treatment.

Synergistic Antitumor Interaction of Risedronate Sodium and Standard Anticancer Agents in Canine (D-17) and Human Osteosarcoma (U-2 OS) Cell Lines

The study discusses in vitro cytotoxicity of a combination of cytostatic drugs (doxorubicin, cisplatin, carboplatin, etoposide) and risedronate sodium against canine and human osteosarcoma (D-17 and U-2 OS). Standard protocols were used for the preparation of cell cultures and evaluation of their viability and apoptosis. MTT assay assessed the culture viability and EC50, while the apoptotic effect of the drugs was checked with a TUNEL assay. Doxorubicin alone showed the strongest cytotoxicity against D-17 (0.056 ± 0.019 µg/mL) and U-2 OS (0.051 ± 0.003 µg/mL), while the lowest cytotoxicity was observed for carboplatin (D-17, 6.45 ± 0.2 µg/mL and U2-OS, 27.5 ± 2.3 µg/mL). Risedronate sodium at 100, 10 and 1 µg/mL lowered viability in OS cell lines by 53.38 ± 1.46 and 49.56 ± 0.7%, 97.08 ± 3.32 and 74.92 ± 4.01%, and 102.67 ± 3.56 and 94.56 ± 3.52%, respectively. In all analyzed drug combinations, risedronate sodium significantly (* p < 0.05) increased the cytotoxicity against tested osteosarcoma cell lines. The decrease in cell viability caused by the studied compound combinations was weaker in canine than in human cell cultures. A combination of doxorubicin (all concentrations), cisplatin (1 µg/mL) and etoposide (1 µg/mL) with 100 µg/mL of risedronate sodium significantly improved the cytotoxicity of the drugs against canine and human osteosarcoma. Administration of carboplatin (1 µg/mL) and risedronate sodium (100 µg/mL), compared to carboplatin per se, produced no significant differences in cytotoxicity against the D-17 cell culture but significantly enhanced cytotoxicity in the U-2 OS line. The strongest apoptosis in both lines was detected for 0.01 µg/mL doxorubicin combined with 100 µg/mL risedronate sodium or 1 µg/mL cisplatin and 100 µg/mL risedronate sodium. In all combinations, the tested compounds revealed a synergistic mechanism of action.

The role of COX expression in the prognostication of overall survival of canine and feline cancer: A systematic review

Cyclooxygenase (COX) isoforms-1 and -2 have been extensively investigated in cancer. Although COX-2 is the isoform most studied and has been described in several malignancies associated with histologic criteria of malignancy and worse prognosis, COX-1 has also been linked to some forms of cancer. With the present review our aim was to summarize the current state of knowledge and clarify if and in which type of tumours COX-1 and/or COX-2 expression have real prognostic implications. We searched PubMed database for prognostic studies using predefined inclusion criteria in order to ascertain the prognostic value of COX-1 and COX-2 in malignant neoplasia in dogs and cats. Eighteen studies were analysed. COX-2 was shown to be a negative prognostic factor in canine and feline mammary tumours, canine mast cell tumour, canine melanoma, canine osteosarcoma and canine renal cell carcinoma. COX-1 showed a negative prognostic value in feline oral squamous cell carcinoma (SCC). We found high heterogeneity among studies regarding COX immunohistochemical evaluation methodology even in the same type of neoplasia pointing out the need for its standardization at least by tumour type. The available data support the use of COX-2 as a prognostic factor in canine (mammary carcinoma, mast cell tumour, melanoma, osteosarcoma and renal carcinoma) and feline (mammary carcinoma) cancers. For COX-1, its use is advised in feline oral SCC.

Osteosarcoma of the hard palate in a dog ˗ case report

ABSTRACT The osteosarcoma (OSA) is the most diagnosed primary bone cancer in canine patients. This work reports a case of a canine, six years old, mongrel, female, intact, with an OSA in the hard palate. Physical examination detected a firm mass in the palate. Thoracic radiographs, hematological and biochemical exams, histopathological exams and computed tomography were requested. A chondroblastic OSA was diagnosed and the tumor was characterized by immunohistochemistry. There was never evidence of metastasis in this case. The treatment consisted of the combination of conventional chemotherapy, metronomic chemotherapy, and palliative care, aiming at greater survival and well-being of the patient since surgical excision was not possible due to the location and extension of the tumor. Osteogenic sarcomas of the hard palate are rarely seen and described in the literature. In this article we present a characterization of the osteosarcoma with uncommon localization in the hard palate.

COX-2 Signaling in the Tumor Microenvironment

Tumorigenesis is a multistep, complicated process, and many studies have been completed over the last few decades to elucidate this process. Increasingly, many studies have shifted focus toward the critical role of the tumor microenvironment (TME), which consists of cellular players, cell-cell communications, and extracellular matrix (ECM). In the TME, cyclooxygenase-2 (COX-2) has been found to be a key molecule mediating the microenvironment changes. COX-2 is an inducible form of the enzyme that converts arachidonic acid into the signal transduction molecules (thromboxanes and prostaglandins). COX-2 is frequently expressed in many types of cancers and has been closely linked to its occurrence, progression, and prognosis. For example, COX-2 has been shown to (1) regulate tumor cell growth, (2) promote tissue invasion and metastasis, (3) inhibit apoptosis, (4) suppress antitumor immunity, and (5) promote sustainable angiogenesis. In this chapter, we summarize recent advances of studies that have evaluated COX-2 signaling in TME.

Effect of Selected Nonsteroidal Anti-inflammatory Drugs on the Viability of Canine Osteosarcoma Cells of the D-17 Line: In Vitro Studies

Introduction

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in veterinary medicine. They are used in pain control and in anti-inflammatory and antipyretic therapies. Some NSAIDs, e.g piroxicam, also have a documented anticancer effect. The objective of this study was to evaluate which of the commonly used NSAIDs (etodolac, flunixin, tolfenamic acid, carprofen, and ketoprofen) are cytotoxic to the D-17 cell line of canine osteosarcoma.

Material and Methods

The viability of the cells was evaluated using the MTT assay. Four independent repetitions were performed and the results are given as the average of these values; EC₅₀ values (half maximal effective concentration) were also calculated.

Results

The analysis of results showed that carprofen and tolfenamic acid displayed the highest cytotoxicity. Other drugs either did not provide such effects or they were very poor. For carprofen, it was possible to determine an EC₅₀ which fell within the limits of concentrations obtainable in canine serum after the administration of routinely used doses.

Conclusion

The results are promising but further studies should be conducted to confirm them, since this study is only preliminary. The possibility of introducing carprofen and tolfenamic acid into the routine treatment of osteosarcoma in dogs should be considered.

The selective cyclooxygenase-2 inhibitor mavacoxib (Trocoxil) exerts anti-tumour effects in vitro independent of cyclooxygenase-2 expression levels

The inducible inflammatory enzyme cyclooxygenase-2 (COX-2) and its product prostaglandin E2 (PGE₂ ) are prominent tumour promoters, and expression of COX-2 is elevated in a number of tumours of both humans and canines. Targeting COX-2 in cancer is an attractive option because of readily available non-steroidal anti-inflammatory drugs (NSAIDs), and there is a clear epidemiological link between NSAID use and cancer risk. In this study, we aim to establish the anti-tumourigenic effects of the selective, long-acting COX-2 inhibitor mavacoxib. We show here that mavacoxib is cytotoxic to a panel of human and canine osteosarcoma, mammary and bladder carcinoma cancer cell lines; that it can induce apoptosis and inhibit the migration of these cells. Interestingly, we establish that mavacoxib can exert these effects independently of elevated COX-2 expression. This study highlights the potential novel use of mavacoxib as a cancer therapeutic, suggesting that mavacoxib may be an effective anti-cancer agent independent of tumour COX-2 expression.

Prognostic significance of circulating microRNA-214 and -126 in dogs with appendicular osteosarcoma receiving amputation and chemotherapy

BACKGROUND

Dogs with appendicular osteosarcoma (OSA) receiving standard amputation and adjuvant chemotherapy demonstrate variable outcome with treatment; however, additional biomarkers would be helpful for predicting their outcome. In the present study, we assessed the potential of circulating microRNA-214 (miR-214) and - 126 (miR-126) to predict time to metastasis and death in dogs with OSA treated with amputation and chemotherapy.

RESULTS

Seventy-six dogs that fully met inclusion criteria were included in the analysis. The criteria included (1) a diagnosis of appendicular OSA without metastases at diagnosis, (2) treatment by amputation and chemotherapy using carboplatin, doxorubicin, cisplatin, or a combination of these agents. Circulating miR-214 and -126 levels at the time before treatment were measured by using RT-qPCR. High circulating miR-214 and serum alkaline phosphatase (ALP) significantly predicted short disease-free survival (DFS) and overall survival (OS). Conversely, high circulating miR-126 significantly predicted prolonged DFS and OS. An integrated approach using circulating miR-214, - 126, and serum ALP showed better accuracy in the prediction of DFS and OS and identification of long-term survivors than prediction using only ALP. Other variables (age, weight, sex, monocyte counts, and primary tumor site) were associated with neither DFS nor OS. miRNA levels did not strongly correlate with histopathological indices.

CONCLUSIONS

Circulating miR-214, - 126, and an integrated prognostic score have strong potential to predict the outcome of canine appendicular OSA patients receiving amputation and chemotherapy.

Canine sarcomas as a surrogate for the human disease

Pet dogs are becoming increasingly recognized as a population with the potential to inform medical research through their treatment for a variety of maladies by veterinary health professionals. This is the basis of the One Health initiative, supporting the idea of collaboration between human and animal health researchers and clinicians to study spontaneous disease processes and treatment in animals to inform human health. Cancer is a major health burden in pet dogs, accounting for approximately 30% of deaths across breeds. As such, pet dogs with cancer are becoming increasingly recognized as a resource for studying the pharmacology and therapeutic potential of anticancer drugs and therapies under development. This was recently highlighted by a National Academy of Medicine Workshop on Comparative Oncology that took place in mid-2015 (http://www.nap.edu/21830). One component of cancer burden in dogs is their significantly higher incidence of sarcomas as compared to humans. This increased incidence led to canine osteosarcoma being an important component in the development of surgical approaches for osteosarcoma in children. Included in this review of sarcomas in dogs is a description of the incidence, pathology, molecular characteristics and previous translational therapeutic studies associated with these tumors. An understanding of the patho-physiological and molecular characteristics of these naturally occurring canine sarcomas holds great promise for effective incorporation into drug development schemas, for evaluation of target modulation or other pharmacodynamic measures associated with therapeutic response. These data could serve to supplement other preclinical data and bolster clinical investigations in tumor types for which there is a paucity of human patients for clinical trials.

Effects of etoposide alone and in combination with piroxicam on canine osteosarcoma cell lines

Osteosarcoma (OSA) is the most common primary bone tumour in dogs. The poor survival rate in dogs with OSA highlights the need for new therapeutic approaches. This study evaluated the cytotoxic effects of etoposide, alone and in combination with piroxicam, on canine OSA cell cultures. Etoposide alone significantly suppressed cell growth and viability, whereas etoposide in combination with piroxicam exhibited concentration dependent cytotoxicity. The anti-proliferative effect was a result of inactivity of the Cdc2-cyclin B1 complex, which correlated with an increase in the G₂/M fraction. This subsequently activated the apoptosis cascade, as indicated by elevated apoptosis levels and up-regulation of poly (ADP-ribose) polymerase proteolytic cleavage. Down-regulation of survivin expression induced by the combination treatment may have contributed to the enhanced cytotoxicity. The results of this study suggest that further investigation of etoposide and piroxicam as a therapeutic combination for canine OSA is warranted.

Cyclooxygenase-2 Expression in Normal and Neoplastic Canine Mammary Cell Lines

Mammary cancer is the most common cancer in female dogs. Induction of cyclooxygenase-2 (COX-2), a key enzyme in prostaglandins (PGs) biosynthesis, has been demonstrated in various cancers in humans and dogs, including mammary cancer. The objective of this study was to investigate the expression and regulation of COX-2 in canine mammary epithelial cells. Cell lines derived from normal and neoplastic canine mammary glands were cultured in the absence or presence of phorbol 12-myristate 13-acetate (PMA), and immunoblots, immunocytochemistry, radioimmunoassays, and a cell proliferation assay were used to study COX-2 expression and PGs production. Results showed that the neoplastic cell line CMT12 constitutively overexpressed COX-2 protein whereas other mammary cell lines expressed low to undetectable basal levels of COX-2 protein. Basal PGE2 production was significantly higher ( P < .05) in CMT12 compared to other cell lines. Levels of COX-2 protein in CMT12 decreased in a time-dependent manner with serum starvation, and PMA stimulation induced a strong time-dependent increase in COX-2 protein. Treatment of CMT12 cells with NS-398 (a specific COX-2 inhibitor) significantly blocked PGE2 synthesis and reduced cell proliferation ( P < .05). These results indicate that some neoplastic canine mammary cell lines constitutively overexpress COX-2, and that COX-2 inhibition decreases PGE2 production and cell proliferation, supporting a role for COX-2 and PGs in canine mammary oncogenesis.

Cyclooxygenase-2 Expression in Feline Pancreatic Adenocarcinomas

Cyclooxygenase-2 (COX-II) is an inducible enzyme that is responsible for the production of prostaglandin E2 (PGE2), which is often upregulated in neoplastic conditions. Expression of COX-II is documented in the majority of human pancreatic adenocarcinomas and in many epithelial neoplasms in humans and animals. The purpose of this study was to assess a series of feline pancreatic adenocarcinomas for the expression of COX-II. Eight feline pancreatic adenocarcinomas (5 poorly differentiated ductular variants and 3 well-differentiated acinar variants) were included. Immunohistochemical staining showed that COX-II was expressed in 2 (both poorly differentiated ductular variants) of the 8 neoplasms (25%). Approximately 10% of the epithelial cells from these 2 neoplasms expressed intense cytoplasmic staining. However, because feline pancreatic adenocarcinoma does not appear to consistently express COX-II, it is not a useful prognostic indicator for this group of feline neoplasma. In addition, COX-II inhibitors are not likely to be effective therapeutics for cats with this neoplasm.

Association of Canine Osteosarcoma and Monocyte Phenotype and Chemotactic Function

Background

Monocytes/macrophages are likely key cells in immune modulation in dogs with osteosarcoma (OSA). Increased peripheral monocyte counts are negatively correlated with shorter disease‐free intervals in dogs with OSA. Understanding the monocyte/macrophage's modulatory role in dogs with OSA can direct further studies in immunotherapy development for OSA.

Hypothesis/Objectives

That OSA evades the immune response by down‐regulating monocyte chemokine receptor expression and migratory function, and suppresses host immune responses.

Animals

Eighteen dogs with OSA that have not received definitive treatment and 14 healthy age‐matched controls

Methods

Clinical study—expression of peripheral blood monocyte cell surface receptors, monocyte mRNA expression and cytokine secretion, monocyte chemotaxis, and survival were compared between clinical dogs with OSA and healthy control dogs.

Results

Cell surface expression of multiple chemokine receptors is significantly down‐regulated in peripheral blood monocytes of dogs with OSA. The percentage expression of CCR2 (median 58%, range 2–94%) and CXCR2 expression (median 54%, range 2–92%) was higher in control dogs compared to dogs with OSA (CCR2 median 29%, range 3–45%, P = 0.0006; CXCR2 median 23%, range 0.2–52%, P = 0.0007). Prostaglandin E₂ (PGE₂) (OSA, median 347.36 pg/mL, range 103.4–1268.5; control, 136.23 pg/mL, range 69.93–542.6, P = .04) and tumor necrosis factor‐alpha (TNF‐α) (P = .02) levels are increased in OSA monocyte culture supernatants compared to controls. Peripheral blood monocytes of dogs with OSA exhibit decreased chemotactic function when compared to control dogs (OSA, median 1.2 directed to random migration, range 0.8–1.25; control, 1.6, range of 0.9–1.8, P = .018).

Conclusions and Clinical Importance

Dogs with OSA have decreased monocyte chemokine receptor expression and monocyte chemotaxis, potential mechanisms by which OSA might evade the immune response. Reversal of monocyte dysfunction using immunotherapy could improve survival in dogs with OSA.

The long-acting COX-2 inhibitor mavacoxib (Trocoxil™) has anti-proliferative and pro-apoptotic effects on canine cancer cell lines and cancer stem cells in vitro

BACKGROUND

The NSAID mavacoxib (Trocoxcil™) is a recently described selective COX-2 inhibitor used for the management of inflammatory disease in dogs. It has a long plasma half-life, requiring less frequent dosing and supporting increased owner compliance in treating their dogs. Although the use of NSAIDs has been described in cancer treatment in dogs, there are no studies to date that have examined the utility of mavacoxib specifically.

RESULTS

In this study we compared the in vitro activity of a short-acting non-selective COX inhibitor (carprofen) with mavacoxib, on cancer cell and cancer stem cell survival. We demonstrate that mavacoxib has a direct cell killing effect on cancer cells, increases apoptosis in cancer cells in a manner that may be independent of caspase activity, and has an inhibitory effect on cell migration. Importantly, we demonstrate that cancer stem cells derived from osteosarcoma cell lines are sensitive to the cytotoxic effect of mavacoxib.

CONCLUSIONS

Both NSAIDs can inhibit cancer cell proliferation and induce apoptosis in vitro. Importantly, cancer stem cells derived from an osteosarcoma cell line are sensitive to the cytotoxic effect of mavacoxib. Our results suggest that mavacoxib has anti-tumour effects and that this in vitro anti-cancer activity warrants further study.

Survivin inhibition via EZN-3042 in canine lymphoma and osteosarcoma

Canine lymphoma (LSA) and osteosarcoma (OS) have high mortality rates and remain in need of more effective therapeutic approaches. Survivin, an inhibitor of apoptosis (IAP) family member protein that inhibits apoptosis and drives cell proliferation, is commonly elevated in human and canine cancer. Survivin expression is a negative prognostic factor in dogs with LSA and OS, and canine LSA and OS cell lines express high levels of survivin. In this study, we demonstrate that survivin downregulation in canine LSA and OS cells using a clinically applicable locked nucleic acid antisense oligonucleotide (EZN-3042, Enzon Pharmaceuticals, Piscataway Township, NJ, USA) inhibits growth, induces apoptosis and enhances chemosensitivity in vitro, and inhibits survivin transcription and protein production in orthotopic canine OS xenografts. Our findings strongly suggest that survivin-directed therapies might be effective in treatment of canine LSA and OS and support evaluation of EZN-3042 in dogs with cancer.

Evaluation of toxicities from combined metronomic and maximal-tolerated dose chemotherapy in dogs with osteosarcoma

OBJECTIVE

To evaluate the tolerability of a piroxicam and cyclophosphamide metronomic treatment protocol combined with carboplatin alone or carboplatin and doxorubicin at maximal-tolerated doses.

METHODS

Retrospective study of 30 dogs diagnosed with osteosarcoma. All dogs underwent amputation and chemotherapy treatment with one of the two maximal-tolerated dose protocols. Metronomic chemotherapy was administered in conjunction with these protocols, and continued subsequently. The protocols included 0 · 3 mg/kg piroxicam and 10 to 12 mg/M(2) cyclophosphamide with 300 mg/M(2) carboplatin alone, or 300 mg/M(2) carboplatin alternating with 30 mg/M(2) doxorubicin.

RESULTS

Fourteen dogs were treated with the carboplatin and metronomic protocol and 16 were treated with the carboplatin alternating with doxorubicin and metronomic protocol. Grades 3 and 4 toxicities overall were significantly (P = 0 · 018) more common in the former group. The disease-free interval of the carboplatin and metronomic group was 192 days, which was not significantly different (P = 0 · 916) to the 182 days for the carboplatin alternating with doxorubicin and metronomic group. The median survival times of the two groups were 217 and 189 days, respectively.

CLINICAL SIGNIFICANCE

Piroxicam and cyclophosphamide metronomic protocols can be safely administered in combination with maximal-tolerated dose chemotherapy protocols. A significantly higher frequency of toxicities was observed in dogs treated with the carboplatin and metronomic protocol.

Global gene expression analysis of canine osteosarcoma stem cells reveals a novel role for COX-2 in tumour initiation

Osteosarcoma is the most common primary bone tumour of both children and dogs. It is an aggressive tumour in both species with a rapid clinical course leading ultimately to metastasis. In dogs and children distant metastasis occurs in >80% of individuals treated by surgery alone. Both canine and human osteosarcoma has been shown to contain a sub-population of cancer stem cells (CSCs), which may drive tumour growth, recurrence and metastasis, suggesting that naturally occurring canine osteosarcoma could act as a preclinical model for the human disease. Here we report the successful isolation of CSCs from primary canine osteosarcoma, as well as established cell lines. We show that these cells can form tumourspheres, and demonstrate relative resistance to chemotherapy. We demonstrate similar results for the human osteosarcma cell lines, U2OS and SAOS2. Utilizing the Affymetrix canine microarray, we are able to definitively show that there are significant differences in global gene expression profiles of isolated osteosarcoma stem cells and the daughter adherent cells. We identified 13,221 significant differences (p = 0.05), and significantly, COX-2 was expressed 141-fold more in CSC spheres than daughter adherent cells. To study the role of COX-2 expression in CSCs we utilized the COX-2 inhibitors meloxicam and mavacoxib. We found that COX-2 inhibition had no effect on CSC growth, or resistance to chemotherapy. However inhibition of COX-2 in daughter cells prevented sphere formation, indicating a potential significant role for COX-2 in tumour initiation.

Anticancer effects of geopropolis produced by stingless bees on canine osteosarcoma cells in vitro

Geopropolis is produced by indigenous stingless bees from the resinous material of plants, adding soil or clay. Its biological properties have not been investigated, such as propolis, and herein its cytotoxic action on canine osteosarcoma (OSA) cells was evaluated. OSA is a primary bone neoplasm diagnosed in dogs being an excellent model in vivo to study human OSA. spOS-2 primary cultures were isolated from the tumor of a dog with osteosarcoma and incubated with geopropolis, 70% ethanol (geopropolis solvent), and carboplatin after 6, 24, 48, and 72 hours. Cell viability was analyzed by the crystal violet method. Geopropolis was efficient against canine OSA cells in a dose- and time-dependent way, leading to a distinct morphology compared to control. Geopropolis cytotoxic action was exclusively due to its constituents since 70% ethanol (its solvent) had no effect on cell viability. Carboplatin had no effect on OSA cells. Geopropolis exerted a cytotoxic effect on canine osteosarcoma, and its introduction as a possible therapeutic agent in vivo could be investigated, providing a new contribution to OSA treatment.

Cytotoxic action of Brazilian propolis in vitro on canine osteosarcoma cells

Osteosarcoma (OSA) is a primary bone neoplasm frequently diagnosed in dogs. The biology of OSA in pet dogs is identical to that of pediatric patients, and it has been considered an excellent model in vivo to study human OSA. Since the individual response to chemotherapy is unpredictable and considering that propolis is a natural product with several biological properties, this work evaluated the cytotoxic action of propolis on canine OSA cells. The primary cell culture of canine OSA was obtained from the tumor of a dog with OSA. Cell viability was assessed after incubation with propolis, 70% ethanol (propolis solvent), and carboplatin after 6, 24, 48, and 72 h. Cell viability was analyzed by the crystal violet method. Data showed that canine OSA cells were sensitive to propolis in a dose- and time-dependent manner and had a distinct morphology compared to control. Its solvent (70% ethanol) had no effect on cell viability, suggesting that the cytotoxic action was exclusively due to propolis. Our propolis sample exerted a cytotoxic effect on canine OSA cells, and its introduction as a possible therapeutic agent in vivo could be investigated, providing a new contribution to OSA treatment.

The cyclooxygenase-2 inhibitor NS-398 inhibits proliferation and induces apoptosis in human osteosarcoma cells via downregulation of the survivin pathway

Cyclooxygenase-2 (COX-2) is frequently overexpressed in human malignancies and plays a crucial role in tumorigenesis and cancer progression. The present study aimed to investigate the expression and clinical significance of COX-2 and survivin (SUV) in human osteosarcomas (OS), and explore the effects and molecular mechanisms of a selective COX-2 inhibitor NS-398 and SUV on tumor proliferation and apoptosis. Fifty cases of human OS and osteochondromas (OC) were collected. The expression of COX-2 and SUV was assessed using immunohistochemical assays in biopsy samples. MG-63 human OS cells were treated with different concentrations of NS-398, used to investigate their effects on cell proliferation and apoptosis. The recombinant small hairpin RNA adenovirus vector rAd5-SUV was constructed, and the effects and molecular mechanisms of knockdown of SUV on proliferation and apoptosis were evaluated in MG-63 cells. A subcutaneous xenograft tumor model was established, validating the effects of rAd5-SUV on tumor growth in vivo. Based on the results, the expression of COX-2 and SUV in OS showed a higher strong reactivity rate compared with OC (73.3 vs. 25.0%, P=0.001; 63.3 vs. 30.0%, P=0.02), but it did not correlate with the clinicopathological characteristics of OS. NS-398 inhibited proliferation, induced apoptosis and decreased the mRNA expression of COX-2 and SUV in MG-63 cells. Furthermore, adenovirus-mediated knockdown of SUV inhibited proliferation, induced apoptosis, reduced the expression of proliferating cell nuclear antigen (PCNA), increased the expression of caspase-3 (CAS-3) and slowed the growth of xenograft tumors in MG-63 cells. Taken together, the expression of COX-2 and SUV is closely correlated with human OS, and inhibition of COX-2 or knockdown of SUV suppresses tumor proliferation and induces apoptosis, suggesting that COX-2 may be involved in OS cell proliferation and apoptosis through SUV-mediated regulation of PCNA and CAS-3 expression, and provides a potential therapeutic strategy for the treatment of cancer.

Immunohistochemical investigation of cell cycle and apoptosis regulators (survivin, β-catenin, p53, caspase 3) in canine appendicular osteosarcoma

Background

Osteosarcoma (OSA) represents the most common canine primary bone tumour. Despite several pathways have been investigated so far, few molecules have been identified as prognostic tools or potential therapeutic targets, and there is still the need to find out molecular pathways with specific influence over OSA progression to facilitate earlier prognosis and treatment.

Aims of the present study were to evaluate the immunohistochemical pattern and levels of expression of a panel of molecules (survivin, β-catenin, caspase 3 -inactive and active forms- and p53) involved in cell cycle and apoptosis regulation in canine OSA samples, known to be of interest in the study also of human OSA, and to detect specific relations among them and with histological tumour grade, disease free interval (DFI) and overall survival (OS).

Results

Nuclear β-catenin immunostaining was detected in normal osteoblasts adjacent to the tumour, and in 47% of the cases. Cytoplasmic and/or membranous immunostaining were also observed. Nuclear survivin and p53 positive cells were found in all cases. Moderate/high cytoplasmic β-catenin expression (≥10% positive cells) was significantly associated with the development of metastasis (P = 0.014); moderate/high nuclear p53 expression (≥10% positive cells) was significantly associated with moderate/high histological grade (P = 0.017) and shorter OS (P = 0.049). Moderate/high nuclear survivin expression (≥15% positive cells) showed a tendency toward a longer OS (P = 0,088).

Conclusions

The present results confirmed p53 as negative prognostic marker, while suggested survivin as a potential positive prognostic indicator, rather than indicative of a poor prognosis. The detection of nuclear β-catenin immunostaining in normal osteoblasts and the absent/low expression in most of the OSAs, suggested that this pathway could not play a major role in oncogenic transformation of canine osteoblasts. Further studies are needed to confirm these hypotheses.

Expression of Ki67, BCL-2, and COX-2 in canine cutaneous mast cell tumors: association with grading and prognosis

The expression of Ki67, BCL-2, and COX-2 was investigated in 53 canine cutaneous mast cell tumors (MCTs) by immunohistochemistry and quantitative real time polymerase chain reaction (qPCR) to evaluate their prognostic significance and the association with the histologic grading and the mitotic index (MI). MCTs were graded according to the Patnaik grading system and the novel 2-tier grading system proposed by Kiupel. The numbers of mitotic figures/10 high-power fields (MI) were counted. Both grading systems were significantly associated with prognosis. The Patnaik grading was of limited prognostic value for grade 2 MCTs, with 23% being associated with mortality. The concordance among pathologists was strongly improved by the application of the 2-tier grading system, and 71% of high-grade MCTs were associated with a high mortality rate. MI and Ki67 protein expression were significantly associated with grading and survival. No significant association between BCL-2 protein expression and either grading system or health status was observed. BCL-2 mRNA expression was significantly higher in grade 2 than in grade 1 MCTs, while no statistically significant differences were detected between low- and high-grade MCTs. The increased BCL-2 mRNA level was significantly associated with increased mortality rate. The COX-2 protein expression was detected in 78% of the MCTs investigated. However, neither association with the tumor grade nor with the health status was observed. COX-2 mRNA was significantly up-regulated in MCTs compared to surgical margins and control skin tissue, but it was neither associated with tumor grade nor with survival.

Immunohistochemical expression of COX-2, mPGES and EP2 receptor in normal and reactive canine bone and in canine osteosarcoma

Accumulating evidence suggests that cyclooxygenase (COX)-2 is involved in the pathogenesis of human and canine osteosarcoma. The aim of this study was to investigate the expression of COX-2 in normal, reactive and neoplastic canine bone and the events downstream to COX-2 that lead to prostaglandin E(2) (PGE(2)) production. COX-2, microsomal PGE(2) synthase-1 (mPGES-1) and the PGE(2) receptor (EP2) were assessed by immunohistochemistry in 12 samples of normal bone, 14 cases of fracture callus and 27 appendicular osteosarcomas. No immunoreactivity to COX-2, mPGES-1 or EP2 receptor was observed in normal bone. Fifty percent of reactive bone samples expressed COX-2 and 57% expressed mPGES-1 and EP2 receptor, although with weak labelling intensity. Ninety-three percent of osteosarcomas expressed COX-2, while mPGES-1 was expressed by 85% and EP2 receptor by 89% of the tumours. The data confirm that COX-2 is expressed at high level in osteosarcoma and support the use of COX-2 inhibitors to improve the response to chemotherapy. The possibility of blocking the EP2 or the selective inhibition of mPGES-1, rather than COX-2 activity, might decrease the incidence of adverse effects that occur due to the inhibition of prostanoids other than PGE(2).

Prognostic factors in canine appendicular osteosarcoma - a meta-analysis

Background

Appendicular osteosarcoma is the most common malignant primary canine bone tumor. When treated by amputation or tumor removal alone, median survival times (MST) do not exceed 5 months, with the majority of dogs suffering from metastatic disease. This period can be extended with adequate local intervention and adjuvant chemotherapy, which has become common practice. Several prognostic factors have been reported in many different studies, e.g. age, breed, weight, sex, neuter status, location of tumor, serum alkaline phosphatase (SALP), bone alkaline phosphatase (BALP), infection, percentage of bone length affected, histological grade or histological subtype of tumor. Most of these factors are, however, only reported as confounding factors in larger studies. Insight in truly significant prognostic factors at time of diagnosis may contribute to tailoring adjuvant therapy for individual dogs suffering from osteosarcoma. The objective of this study was to systematically review the prognostic factors that are described for canine appendicular osteosarcoma and validate their scientific importance.

Results

A literature review was performed on selected studies and eligible data were extracted. Meta-analyses were done for two of the three selected possible prognostic factors (SALP and location), looking at both survival time (ST) and disease free interval (DFI). The third factor (age) was studied in a qualitative manner. Both elevated SALP level and the (proximal) humerus as location of the primary tumor are significant negative prognostic factors for both ST and DFI in dogs with appendicular osteosarcoma. Increasing age was associated with shorter ST and DFI, however, was not statistically significant because information of this factor was available in only a limited number of papers.

Conclusions

Elevated SALP and proximal humeral location are significant negative prognosticators for canine osteosarcoma.

Prevalence of 5-lipoxygenase expression in canine osteosarcoma and the effects of a dual 5-lipoxygenase/cyclooxygenase inhibitor on osteosarcoma cells in vitro and in vivo

Canine osteosarcoma is an insidious disease with few effective treatment modalities; therefore, use of pharmacologic intervention to improve mortality or morbidity is constantly sought. The use of cyclooxygenase enzyme inhibitors has been an area of interest with limited efficacy based on retrospective examination of tumor expression and in vivo cell proliferation models. Recently, examination of dual cyclooxygenase and 5-lipoxygenase inhibitors in human and canine oncology suggests that 5-lipoxygenase inhibitors may be an effective approach in vitro and during tumor induction in rodent models. Therefore, the authors decided to examine 5-lipoxygenase expression in primary canine osteosarcoma samples and have shown that approximately 65% of osteosarcomas label positive for cytoplasmic 5-lipoxygenase. Further examination of a cell culture and xenograft model shows similar 5-lipoxygenase expression. Surprisingly, a canine 5-lipoxygenase inhibitor (tepoxalin) significantly reduced cell proliferation at physiologic doses in vitro and diminished xenograft tumor growth in nude mice, suggesting that further investigation is needed. Traditionally, 5-lipoxygense leads to production of lipid mediators, such as leukotriene B(4) and 5-oxo-eicosatetraenoic acid, which, when added back to the media of tepoxalin-treated cells, did not recover cell proliferation. The lack of nuclear staining in primary and xenografted tumors and the lack of response to eicoasanoids suggest that lipid mediator production is not the primary means by which tepoxalin acts to alter proliferation. Regardless of the mechanisms involved in retarding cell proliferation, future investigation is warranted.

Expression and function of survivin in canine osteosarcoma

Osteosarcoma has a high mortality rate and remains in need of more effective therapeutic approaches. Survivin is an inhibitor of apoptosis family member protein that blocks apoptosis and drives proliferation in human cancer cells where it is commonly elevated. In this study, we illustrate the superiority of a canine osteosarcoma model as a translational tool for evaluating survivin-directed therapies, owing to the striking similarities in gross and microscopic appearance, biologic behavior, gene expression, and signaling pathway alterations. Elevated survivin expression in primary canine osteosarcoma tissue correlated with increased histologic grade and mitotic index and a decreased disease-free interval (DFI). Survivin attenuation in canine osteosarcoma cells inhibited cell-cycle progression, increased apoptosis, mitotic arrest, and chemosensitivity, and cooperated with chemotherapy to significantly improve in vivo tumor control. Our findings illustrate the utility of a canine system to more accurately model human osteosarcoma and strongly suggest that survivin-directed therapies might be highly effective in its treatment.

Cyclooxygenase-2 expression in animal cancers

Cyclooxygenase (COX; also known as prostaglandin endoperoxide synthase) is a key enzyme in the biochemical pathway leading to the synthesis of prostaglandins. A large amount of epidemiological and experimental evidence supports a role for COX-2, the inducible form of the enzyme, in human tumorigenesis, notably in colorectal cancer. COX-2 mediates this role through the production of PGE(2) that acts to inhibit apoptosis, promote cell proliferation, stimulate angiogenesis, and decrease immunity. Similarly, COX-2 is believed to be involved in the oncogenesis of some cancers in domestic animals. Here, the author reviews the current knowledge on COX-2 expression and role in cancers of dogs, cats, and horses. Data indicate that COX-2 upregulation is present in many animal cancers, but there is presently not enough information to clearly define the prognostic significance of COX-2 expression. To date, only few reports document an association between COX-2 expression and survival, notably in canine mammary cancers and osteosarcomas. Some evidence suggests that COX inhibitors could be useful in the prevention and/or treatment of certain cancers in domestic animals, the best example being urinary transitional cell carcinomas in dogs. However, determination of the levels of COX-2 in a tumor does not appear to be a good prognostic factor or a good indicator for the response to nonsteroidal anti-inflammatory drug therapy. Clearly, additional research, including the development of in vitro cell systems, is needed to determine if COX-2 expression can be used as a reliable prognostic factor and as a definite therapeutic target in animal cancers.

Induction of VEGF by tepoxalin does not lead to increased tumour growth in a canine osteosarcoma xenograft

The purpose of this study was to determine the impact of the non-steroidal anti-inflammatory drug tepoxalin on canine tumour cell growth and describe the changes associated with tepoxalin treatment. In vitro experiments were performed to assess tepoxalin-associated alterations in tumour cell growth. Clinically achievable tepoxalin concentrations did not significantly alter tumour cell growth in vitro. Vascular endothelial growth factor (VEGF) production and hypoxia-inducible factor-1α dose-dependently increased in vitro in the presence of tepoxalin. A canine osteosarcoma xenograft was used to determine in vivo effects of tepoxalin on tumour growth and angiogenesis. Despite increased VEGF in vitro, there was a significant growth delay associated with tepoxalin treatment. Normal dogs were administered tepoxalin to assess effects on systemic VEGF production, but not found to have significantly increased VEGF. These data suggest that tepoxalin may moderately inhibit tumour growth and may be administered as an analgesic to tumour-bearing dogs.

Prognostic and predictive biomarkers of canine osteosarcoma

Canine osteosarcoma (OS) is an aggressive tumour that accounts for approximately 90% of primary bone tumours in the dog. Although the standard treatments (including limb amputation/sparing, chemotherapy and palliative radiotherapy) have significantly increased survival rates, almost 90% of animals will eventually develop predominantly pulmonary metastases. Despite advances in various therapies, prognosis remains poor, with median survival times ranging from 3 months to 1 year and <20% of dogs survive for >2 years following diagnosis. Various clinical and epidemiological markers have facilitated decision-making with respect to therapy but no single molecular biomarker has been shown to enhance prediction of disease progression. The publication of the canine genome in 2005 raised the possibility of increasing understanding of the genetic mechanisms underpinning canine OS. This review explores the use of biomarkers within the multi-disciplinary management of dogs with OS, and highlights the few known, potential prognostic/predictive molecular markers including their potential value as 'bridging biomarkers' for human OS. Although high-throughput profiling of canine OS remains in its infancy, research within the next decade using leading-edge screening technologies has the potential to identify biomarkers that may enhance diagnostic and prognostic accuracy and result in more effective, individually tailored, treatment and management protocols for affected dogs.

Cyclooxygenase-2 Expression in Equine Tumors

The enzyme cyclooxygenase-2 (COX-2) is expressed in some tumor and stromal tissues, and catalyzes production of prostaglandins with growth stimulatory, antiapoptotic, proangiogenic, and immunosuppressive properties. Pharmacologic inhibition of COX-2 is associated with antitumor activity in various human and canine malignancies. The purpose of this study was to assess COX-2 expression in a series of equine sarcoids, melanomas, and squamous-cell carcinomas (SCC). COX-2 expression was assessed in formalin-fixed paraffin-embedded tissues from 14 sarcoids, 11 melanomas, and 37 SCC that represent various anatomic sites by using standard immunohistochemical methods. COX-2 was expressed in 2 of 14 sarcoids, 7 of 11 melanomas, and 32 of 37 SCC, 56% of which demonstrated moderate-to-strong immunoreactivity. There were no differences in expression between anatomic sites. In conclusion, most equine SCC and many melanomas appear to express COX-2 and thus could respond to COX-2 inhibitor therapy.

Heritability and segregation analysis of osteosarcoma in the Scottish deerhound

Osteosarcoma is the most common malignant bone tumor in dogs and, like its human orthologue, is characterized by aggressive local behavior and high metastatic rates. The Scottish deerhound is a breed of dog with a >15% incidence of osteosarcoma and represents an excellent spontaneously occurring large-animal model of the human disease. We modeled the transmission of the osteosarcoma phenotype in a population of over 1000 related deerhounds ascertained as part of a prospective health study. Variance component analysis, segregation analysis, and linear modeling were performed to evaluate heritability, to infer the presumptive transmission model, and to identify covariate effects for this phenotype within the breed, respectively. Based on variance component analysis, heritability (h2) was estimated to be 0.69. Six transmission models were analyzed by segregation analysis; based on Akaike's information criteria, the most parsimonious model was the Mendelian major gene model with dominant expression. Linear modeling identified gender and genotype as significant predictors of disease outcome. Importantly, duration of gonadal hormone exposure, weight, and height at maturity were not significant predictors of outcome. Inheritance of the putative high-risk allele was thus associated with >75% risk of disease occurrence compared to the <5% baseline risk. These results support the hypothesis that a major gene with a dominant effect explains most of the osteosarcoma phenotype within the Scottish deerhound.

Nonsteroidal anti-inflammatory drugs in cats: a review

OBJECTIVE

To review the evidence regarding the use of nonsteroidal anti-inflammatory drugs (NSAIDs) in cats.

DATABASES USED

PubMed, CAB abstracts.

CONCLUSIONS

Nonsteroidal anti-inflammatory drugs should be used with caution in cats because of their low capacity for hepatic glucuronidation, which is the major mechanism of metabolism and excretion for this category of drugs. However, the evidence presented supports the short-term use of carprofen, flunixin, ketoprofen, meloxicam and tolfenamic acid as analgesics in cats. There were no data to support the safe chronic use of NSAIDs in cats.

Overexpression of Cox-2 in Human Osteosarcoma Cells Decreases Proliferation and Increases Apoptosis

Overexpression of cyclooxygenase-2 (COX-2) is generally considered to promote tumorigenesis. To investigate a potential role of COX-2 in osteosarcoma, we overexpressed COX-2 in human osteosarcoma cells. Saos-2 cells deficient in COX-2 expression were retrovirally transduced or stably transfected with murine COX-2 cDNA. Functional expression of COX-2 was confirmed by Northern and Western analyses and prostaglandin production. Overexpression of COX-2 reduced cell numbers by 50% to 70% compared with controls. Decreased proliferation in COX-2-overexpressing cells was associated with cell cycle prolongation in G(2)-M. Apoptosis, measured by both Annexin V binding assay and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, was increased in cells overexpressing COX-2, and the increase was not reversed by treatment with NS-398, indicating that the effects were not mediated by prostaglandins. Retroviral COX-2 overexpression in two other human osteosarcoma cell lines, U2OS and TE85, also decreased cell viability. However, in the human colon carcinoma HCT-116 cell line, which is deficient in COX-2, retroviral overexpression of COX-2, at similar efficiency as in Saos-2 cells, increased resistance to apoptosis. Reactive oxygen species (ROS), measured by flow cytometry, were increased by COX-2 overexpression in Saos-2 cells but not in HCT-116 cells. Inhibition of peroxidase activity, but not of COX activity, blocked the ROS increase. Antioxidants blocked the increase in ROS and the increase in apoptosis due to COX-2 overexpression in Saos-2 cells. Our results suggest that (a) COX-2 overexpression in osteosarcoma cells may increase resistance to tumorigenesis by increasing ROS to levels that decrease cell viability and (b) the effects of COX-2 overexpression are cell type/tissue dependent.