Invasive Front Grading and Epithelial-Mesenchymal Transition in Canine Oral and Cutaneous Squamous Cell Carcinomas

Oral and cutaneous tissues are the most frequent origin in canine squamous cell carcinoma (SSC). In SCC, changes in adhesion molecule expression and transition from epithelial to mesenchymal phenotype are thought to be important in development of invasive behavior of neoplastic cells at the leading front of the tumor. We therefore investigated histological invasive front grading and epithelial-mesenchymal transition (EMT) in both oral SCCs and cutaneous SCCs. EMT was assessed by evaluating immunohistochemical expression of E-cadherin, β-catenin, desmoglein, vimentin, and N-cadherin. Regardless of the anatomic location, invasive front grading resulted in higher histological grades than grading of the surface. Most oral SCCs were of significantly higher histologic grade than cutaneous SCCs ( P < .01). Expression of E-cadherin, β-catenin, and desmoglein was significantly lower in oral SCC compared with cutaneous SCC ( P < .01). A significant association was found between invasive front grading and loss of E-cadherin, β-catenin, and desmoglein ( P < .01). Also, vimentin-positive neoplastic cells had low immunoreactivity of these adhesion molecules, and a few of these neoplastic cells were positive for N-cadherin. These results suggest not only E-cadherin and β-catenin but also desmoglein as markers for predicting biological behavior of canine SCC. Depending on their primary sites, EMT correlates with biological behavior and therefore histological grade of canine SCC. We suggest that combining invasive front grading with assessment of immunohistochemical expression of E-cadherin, β-catenin, and desmoglein may allow more accurate prediction of biological behavior of canine SCCs.

Expression of Monocarboxylate Transporter 1 in Oral and Ocular Canine Melanocytic Tumors

Solid tumors are composed of a heterogeneous population of cells surviving in various concentrations of oxygen. In a hypoxic environment, tumor cells generally up-regulate glycolysis and, therefore, generate more lactate that must be expelled from the cell through proton transporters to prevent intracellular acidosis. Monocarboxylate transporter 1 (MCT1) is a major proton transporter in mammalian cells that transports monocarboxylates, such as lactate and pyruvate, together with a proton across the plasma membrane. Melanocytic neoplasia occurs frequently in dogs, but the prognosis is highly site-dependent. In this study, 50 oral canine melanomas, which were subdivided into 3 histologic subtypes, and 17 ocular canine melanocytic neoplasms (14 melanocytomas and 3 melanomas) were used to examine and compare MCT1 expression. Immunohistochemistry using a polyclonal chicken anti-rat MCT1 antibody showed that most oral melanoma exhibited cell membrane staining, although there were no significant differences observed among the 3 histologic subtypes. In contrast, the majority of ocular melanocytic tumors were not immunoreactive. Additionally, we documented the presence of a 45-kDa band in cell membrane protein Western blots, and sequencing of a reverse transcriptase polymerase chain reaction band of expected size confirmed its identity as a partial canine MCT1 transcript in 3 oral tumors. Increased MCT1 expression in oral melanomas compared with ocular melanocytic tumors may reflect the very different biology between these tumors in dogs. These results are the first to document canine MCT1 expression in canine tumors and suggest that increased MCT1 expression may provide a potential therapeutic target for oral melanoma.

Significance of caveolin-1 and matrix metalloproteinase 14 gene expression in canine mammary tumours

Canine mammary tumours (CMTs) are the most common neoplasms affecting female dogs. There is an urgent need for molecular biomarkers that can detect early stages of the disease in order to improve accuracy of CMT diagnosis. The aim of this study was to examine whether caveolin-1 (Cav-1) and matrix metalloproteinase 14 (MMP14) are associated with CMT histological malignancy and invasion. Sixty-five benign and malignant CMT samples and six normal canine mammary glands were analysed using quantitative reverse transcription-polymerase chain reaction. Cav-1 and MMP14 genes were highly expressed in CMT tissues compared to normal tissues. Cav-1 especially was overexpressed in malignant and invasive CMT tissues. When a CMT cell line was cultured on fluorescent gelatin-coated coverslips, localisation of Cav-1 was observed at invadopodia-mediated degradation sites of the gelatin matrix. These findings suggest that Cav-1 may be involved in CMT invasion and that the markers may be useful for estimating CMT malignancy.

Diversity of Histologic Patterns and Expression of Cytoskeletal Proteins in Canine Skeletal Osteosarcoma

Osteosarcoma (OS), the most common bone tumor, includes OS of the head (OSH) and appendicular OS (OSA). In dogs, it is classified into 6 histologic subtypes: osteoblastic, chondroblastic, fibroblastic, telangiectatic, giant cell, and poorly differentiated. This study investigated the significance of the histologic classification relevant to clinical outcome and the histologic and immunohistochemical relationships between pleomorphism and expression of cytoskeletal proteins in 60 cases each of OSH and OSA. Most neoplasms exhibited histologic diversity, and 64% of OS contained multiple subtypes. In addition to the above 6 subtypes, myxoid, round cell, and epithelioid subtypes were observed. Although the epithelioid subtypes were observed in only OSH, no significant difference in the frequency of other subtypes was observed. Also, no significant relevance was observed between the clinical outcome and histologic subtypes. Cytokeratin (CK) was expressed in both epithelioid and sarcomatoid tumor cells in various subtypes, and all CK-positive tumor cells also expressed vimentin. Vimentin and α-smooth muscle actin (SMA) were expressed in all subtypes. A few SMA-positive spindle-shaped tumor cells exhibited desmin expression. Glial fibrillary acidic protein-positive tumor cells were observed in many subtypes, and some of these cells showed neurofilament expression. Although OSH exhibited significantly stronger immunoreactivity for SMA than OSA, no significant difference in other cytoskeletal proteins was observed. Some tumor cells had cytoskeletal protein expression compatible with the corresponding histologic subtypes, such as CK in the epithelioid subtype and SMA in the fibroblastic subtype. Thus, canine skeletal OS is composed of pleomorphic and heterogenous tumor cells as is reflected in the diversity of histologic patterns and expression of cytoskeletal proteins.

Clinical pharmacokinetics of anti-angiogenic photodynamic therapy with benzoporphyrin derivative monoacid ring-A in dogs having naturally occurring neoplasms

The aim of this study was to examine the pharmacokinetics of clinically applied benzoporphyrin derivative monoacid ring-A (BPD-MA; Verteporfin), a second-generation photosensitizer, during a trial of photodynamic therapy (PDT) in nine dogs having naturally occurring neoplasms. After injecting BPD-MA at 0.5 mg/kg intravenously, its mean half-life (t1/2) was found to be 8.14 +/- 5.34 h, mean clearance (Cl) 35.13 +/- 9.62 ml/(h kg), the mean value of the volume of distribution (Vc) 0.08 +/- 0.01 l/kg and the mean steady state volume of distribution (Vss) 0.38 +/- 0.31 l/kg respectively. With the exception of a transitional increase in serum alkaline phosphatase activity, no other clinical abnormalities were observed. The t1/2 in dogs with naturally occurring tumours was longer than that in humans, but similar to that in rats. The values of Cl and Vss in dogs having naturally occurring neoplasms were lower than those in humans. It is suggested that the pharmacokinetics of BPD-MA in tumour-bearing dogs would be helpful in determining the protocol of a short drug-light interval PDT with BPD-MA that mainly targets the tumour vasculature.

Urethral transitional cell carcinoma in a cat

A 15-year-old, male neutered cat was referred for investigation of dysuria. A retrograde urethrography was performed which showed two space-occupying masses within the lumen of the mid-to-proximal urethra. Exploratory coeliotomy revealed two urethral masses. Segmental urethrectomy was performed to resect the mass, and the lower urinary tract was reconstructed by vesico-urethral anastomosis. Histopathology showed the mass to be a transitional cell carcinoma with incomplete surgical margins. Tumour regrowth was suspected when dysuria was found approximately 318 days after surgery. Clinical signs were palliated by radiation using weekly fractions of 6 Gy for three weeks. The cat died of unknown causes 386 days postoperatively.

Neuroendocrine carcinoma in the nasal cavity of ten dogs

Neuroendocrine (NE) carcinoma was diagnosed in 10 dogs. In six cases examined by cephalometric radiography and computerized tomography, a large mass was seen to fill the nasal cavity. Histopathologically, sheets, nests or ribbons of neoplastic cells were separated by delicate or thick fibrovascular stroma. The neoplastic cells were round, oval, or spindle-shaped; cytoplasmic granules and hyperchromatic nuclei with prominent nucleoli were present. Neoplastic cells were invariably immunohistochemically positive for cytokeratin (CK) AE1/AE3, neuron-specific enolase, chromogranin A and vasoactive intestinal polypeptide. Eight dogs were positive for S100 protein, seven for synaptophysin, five for protein gene product 9.5, two for somatostatin, and one for Leu-7. Immunolabelling gave negative results for CK 8, CK 19, calcitonin, calcitonin gene-related polypeptide, neurofilaments, serotonin, gastrin and glial fibrillary acidic protein. Ultrastructurally, the neoplastic cells contained a large number of round, membrane-bounded, densely-cored granules corresponding to neurosecretory granules. These observations were consistent with the neuroendocrine nature of the carcinomas.

Canine Ganglioneuroblastoma in the Oral Mucosa

A ganglioneuroblastoma of the oral cavity in a dog was examined histologically and immunohistochemically. This rare neoplasm was considered to be derived from ectopic neural crest cells. This is the first report of a canine ectopic ganglioneuroblastoma located in the oral mucosa.

Biological Properties of Allogenic Articular Chondrocytes on the Surface of Bovine Cartilage Explants in vitro

Bovine cartilage explants were co-cultured with or without allogenic chondrocytes for 4 weeks. The attachment of the applied chondrocytes to cartilage after labelling with fluorescence was assessed using a confocal laser microscope. Morphological changes and the production of extracellular matrix (ECM) of co-cultured chondrocytes on intact and damaged surfaces of cartilage were evaluated by histological and immunohistochemical methods. Co-cultured chondrocytes attached to and proliferated on the intact and damaged areas of cartilage, and a new layer was created there. The defects were also filled with ECM produced by the co-cultured chondrocytes. Glycosaminoglycans and collagen type II were detected in the newly formed ECM, and large numbers of rounded chondrocytes were observed at primitive lacunae in this matrix at 4 weeks of culture. The results suggest that chondrocytes have the ability to attach to, to proliferate on and to establish a new matrix on the intact and damaged surfaces of cartilage explants.

Perianal rhabdomyosarcoma in a dog

A perianal rhabdomyosarcoma was diagnosed in an 11-year-old neutered male Labrador retriever. Following two incomplete surgical excisions of the tumour, the dog was treated by means of surgery combined with local radiotherapy and systemic chemotherapy using one cycle of vincristine sulphate, doxorubicin and cyclophosphamide (VAC protocol). The dog died 252 days after the first combined therapy. Radiography at this time demonstrated enlargement of the iliac lymph nodes, suggesting metastasis of the tumour. To the authors' knowledge, this is the first report of treatment of canine perianal rhabdomyosarcoma.

Establishment and characterization of a new canine mast cell tumor cell line

A new cell line (CoMS) was established from a 3-year-old male mongrel dog with mast cell tumor of the oral mucosa. CoMS cells grow in suspension with a doubling time of 27.0 +/- 0.7 hr. The cytoplasmic granules were formalin-sensitive, showed diverse appearances in their ultrastructural findings and contained heparin proteoglycan and neutral protease chymase. Calcium ionophore A23187, substance P and concanavalin A caused significant histamine release from CoMS cells, while compound 48/80 failed to release histamine. This cell line will make an available source for studies on canine mast cell tumors.

Evaluation effects of chitosan for the extracellular matrix production by fibroblasts and the growth factors production by macrophages

Chitosan is reported as an accelerator of wound healing. Histological findings of previous reports indicate that chitosan accelerates the reformation of connective tissue, however the details of the mechanism are not clear. In this study, firstly L929 mouse fibroblasts were cultured with chitosan and the production of extracellular matrix (ECM) was evaluated in vitro. Type I and III collagens and fibronectin were secreted by L929 with or without chitosan; however there was no significant difference in the amount of ECM between the control and the chitosan groups. Secondly, macrophages were stimulated with chitosan, and then transforming growth factor-beta 1 (TGF-beta1) and platelet-derived growth factor (PDGF) messenger ribonucleic acid (mRNA) expressions and production of their proteins were assayed in vitro. As a result, chitosan promoted the production of TGF-beta1 and PDGF. These results indicate that chitosan does not directly accelerate ECM production by fibroblast and the ECM production may increase by the growth factors.

Efficacy of enamel matrix proteins on apical periodontal regeneration after experimental apicoectomy in dogs

Adult dogs have a complex apical delta structure in all root apexes of teeth. This complex structure may affect the formation of apical lesions in the teeth such as apical abscesses. The purpose of this study was to evaluate the efficacy of enamel matrix protein (EMP) which was used for periodontal regeneration therapy after an experimental apicoectomy for an assumed apical lesions of the teeth in dogs. The maxillar canine roots and maxillar fourth premolar buccal mesial roots in five beagles were experimentally apicoectomized under general inhalation anesthesia. After the root apex was exposed and excised, EMP was applied on the surface of the exposed dentin. After 12 weeks, dogs were euthanized. and the experimental teeth together with the surrounding soft and hard periodontal tissues were collected for histological evaluation under a light microscope. In the EMP group, the size of the defect where the root apex was removed was smaller than that of the control group. New cementum was dominantly achieved in the EMP group compared to the control group. Furthermore, new collagen fibers that bridged area between the new cementum and new alveolar bone were detected only in the EMP group. The present results demonstrated marked apical periodontal regeneration after apicoectomy in the EMP group. These results, therefore, suggest that the application of EMP can effectively induce the regeneration of periodontal strUctures in apicoectomized dogs.

Biomechanical and morphologic evaluation of a three-dimensional fabric sheep artificial intervertebral disc: in vitro and in vivo analysis

STUDY DESIGN

We have developed a new artificial intervertebral disc consisting of triaxial three-dimensional fabric for the sheep lumbar spine. To clarify the characteristics of the new implant, a series of biomechanical tests and morphologic evaluations were conducted.

OBJECTIVES

To investigate the static, viscoelastic, and fatigue properties of the three-dimensional fabric disc in comparison with natural sheep disc and to evaluate their biomechanical and morphologic alteration in vivo.

SUMMARY OF BACKGROUND DATA

In its human dimensions the three-dimensional fabric disc revealed mechanical properties similar to a natural human disc.

METHODS

The disc-body units from sheep spine and the sheep three-dimensional fabric discs underwent tensile-compressive (200 N), torsional (5 Nm), and creep-recovery tests (30 minutes-30 minutes, 200 N). After fatigue loading (2 million, compressive 200 N) the biomechanical changes and the debris were investigated. For in vivo evaluation after placing in the sheep psoas muscles for 6 months, the surface of the three-dimensional fabric disc was evaluated using macroscopy and scanning electron microscopy, followed by previous biomechanical tests.

RESULTS

The behavior of the sheep three-dimensional fabric disc was similar to that of natural sheep disc in tensile-compressive and creep-recovery tests. In torsional testing the behavior of natural sheep disc was more rigid than that of the sheep three-dimensional fabric disc. After fatigue loading there was no biomechanical change and no debris detected. Six months after surgery no morphologic deterioration was observed nor were there changes in biomechanical parameters.

CONCLUSIONS

The sheep three-dimensional fabric disc exhibited biomechanical and morphologic biostability, appropriate viscoelasticity, and excellent fatigue properties. The three-dimensional fabric disc has a potential for clinical application of human intervertebral disc replacement.

The formation of apical delta of the permanent teeth in dogs

To determine the process of formation of apical delta, a histological study on the permanent teeth was carried out in dogs. A litter of 7 clinically healthy beagle dogs and 33 adult dogs (4- to 15- year-old) of 12 breeds with periodontal disease were used for the experiments. Teeth extracted from 6-,7-,8- and 9-month-old beagles were sectioned and stained with HE solution. Tooth roots obtained from adult dogs with periodontal disease were ground. Each tooth was classified into the following root types under a light microscope: Type I (no apical delta = no apical closure), II (few apical delta), IIIA (low apical delta) and IIIB (high apical delta). In the 6-month-old beagles, more than half the tooth roots were classified as type I. In the 7-month-old beagles, type IIIB apical delta was the most predominant and types I, II and IIIA apical delta were occassionally seen. Apical closure and delta were observed in all beagles at 8 months of age histologically. In the 8- and 9-month-old beagles, all root apexes observed were type IIIB. Most of the 314 tooth roots extracted from 33 adult dogs were type IIIB, but a few were type IIIA.

Acute respiratory failure caused by leukaemic infiltration of the lung of a dog

A seven-year-old crossbred male dog with a suspected leukaemic condition was referred for investigation and treatment. A bone marrow aspirate revealed an acute myeloid leukaemia. Combination chemotherapy was administered and the dog initially improved, but 18 days after the initiation of therapy its body condition deteriorated and the animal developed acute respiratory distress. On postmortem examination, extensive leukaemic pulmonary infiltrates were evident.

Chitosan accelerates the production of osteopontin from polymorphonuclear leukocytes

Chitosan is a copolymer of beta(1 --> 4) glucosamine and N-acetyl-D-glucosamine, which accelerates the infiltration of polymorphonuclear leukocytes (PMN) in the early phase of wound healing. In the granulation tissue treated with chitosan in canine experimental wound, osteopontin (OPN) was strongly positive in PMN immunohistochemically. OPN is a glycosylated phosphoprotein and promotes the attachment or spread of a variety of cell types. In addition, OPN may play a role in granulomatous inflammation. Production of OPN in PMN was therefore investigated in vitro using human PMN in this study. PMN stimulated with granulocyte-colony stimulating factor (G-CSF) and chitosan accumulated OPN mRNA, and released OPN into their culture supernatants. These findings suggest that OPN is synthesized by migrating PMN which plays the novel role of regulating the evolution of wound healing with chitosan treatment at the early phase of healing.

Association between exogenous atrial natriuretic peptide and hemodynamics in dogs with congestive heart failure produced by experimental mitral regurgitation

Association between exogenous atrial natriuretic peptide (ANP) and hemodynamic changes was ascertained in 3 dogs with overt congestive heart failure (CHF(+)) and 3 dogs without congestive heart failure (CHF(-)) caused by experimental mitral regurgitation (MR). The hemodynamic measurements were recorded in all dogs during and after 1 hr infusion of ANP at the rate of 0.1 (low dose), 0.5 (medium dose) and 1.0 (high dose) microg/kg/min, respectively. Heart rate, mean arterial pressure, pulmonary capillary wedge pressure (PCWP) and systemic vascular resistance decreased significantly during and after ANP infusion even with low dose in the CHF(+). Stroke volume, stroke volume index and cardiac output in the CHF(+) during and after ANP infusion showed an increasing trend as compared with the CHF(-). Double product, an indicator of myocardial oxygen consumption, significantly decreased during and after ANP administration at all doses in the CHF(+). These findings indicate that even at low dose, exogenous ANP improves cardiac performance and reduces myocardial oxygen consumption in the CHF(+), and suggest that ANP has beneficial effects in the treatment of dogs with overt congestive heart failure resulting from MR.

Canine extracutaneous mast-cell tumours consisting of connective tissue mast cells

Two cases of canine extracutaneous mast-cell tumours were encountered, originating from the mucosa of either the oral cavity or the small intestine. The dogs had no neoplasms in the skin. Immunohistochemical and ultrastructural studies demonstrated that the neoplastic cells had the features of connective tissue mast cells. It would seem, therefore, that at least some extracutaneous forms of the neoplasm originate from connective tissue mast cells. Heparin was a useful cytological marker to diagnose this type of mast-cell tumour.

Effect of all-trans and 9-cis retinoic acid on growth and metastasis of xenotransplanted canine osteosarcoma cells in athymic mice

OBJECTIVE

To determine effects of all-trans and 9-cis retinoic acid (RA) on tumor growth and metastatic ability of canine osteosarcoma cells transplanted into athymic (nude) mice.

ANIMALS

Forty-five 5-week-old female BALB/c nude mice.

PROCEDURE

1 X 10(7) POS osteosarcoma cells were transplanted subcutaneously into the intrascapular region of mice. All-trans RA (3 or 30 microg/kg of body weight in 0.1 ml of sesame oil), 9-cis RA (3 or 30 mg/kg in 0.1 ml of sesame oil), or sesame oil (0.1 ml; control treatment) were administered intragastrically 5 d/wk for 4 weeks beginning 3 days after transplantation (n = 4 mice/group) or after formation of a palpable tumor (5 mice/group). Tumor weight was estimated weekly by measuring tumor length and width, and retinoid toxic effects were evaluated daily. Two weeks after the final treatment, mice were euthanatized, and number of mice with pulmonary metastases was determined.

RESULTS

Adverse treatment effects were not detected. Tumor weight was less in mice treated with either dose of 9-cis RA than in control mice, although this difference was not significant. Treatment with 30 mg of 9-cis RA/kg initiated after tumor formation significantly reduced the incidence of pulmonary metastasis, compared with the control group.

CONCLUSIONS AND CLINICAL RELEVANCE

9-cis RA decreased the incidence of pulmonary metastasis in nude mice transplanted with canine osteosarcoma cells and may be a potential adjunct therapy for treatment of osteosarcoma in dogs.

Endothelial cell responses to chitin and its derivatives

The effects of chitin and its derivatives on the proliferation of human umbilical vein endothelial cells (HUVECs) and on the production of cytokines were examined in vitro. Chitin and its derivatives had no effect on the proliferation of cultured HUVECs. N-Sulfonated 70% deacetylated chitin (S-DAC70) stimulated the production of interleukin (IL)-1beta, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha from HUVECs. Compared to S-DAC70, the other materials tested in the present study showed less effect in the stimulation of IL-8 and TNF-alpha production and had no effect in the stimulation of IL-1beta and IL-6 production. These results indicated that S-DAC70 affects HUVECs function but not proliferation.

Retinoid receptors and the induction of apoptosis in canine osteosarcoma cells

Retinoids, all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid (9-cis-RA), induced morphological changes and apoptosis-like cell death characterized by cell shrinkage, chromatin condensation and nuclear disintegration in three canine osteosarcoma cells, OOS, HOS and POS, at a concentration of 10(-5) M. Both retinoid receptors, RARs and RXRs, were identified in these cells. 9-cis-RA bound to both the RXRs and the RARs, whereas ATRA bound to only the RARs in these cells. Those results indicate that the induction of apoptosis in canine osteosarcoma cells may be mediated by the specific control of RARs and RXRs.

Influence of vitamin D and retinoids on the induction of functional differentiation in vitro of canine osteosarcoma clonal cells

The efficacy of 22-oxacalcitriol (OCT), calcitriol, cholecalciferol, all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) to differentiate in vitro four clonal cells of the canine osteosarcoma cell line POS into cells having properties of a functionally mature osteoblast bone cell were investigated. The induction of intracellular alkaline phosphatase (ALP) activity, osteocalcin (GLA-OC) and type I collagen (PIP) production after 72 h treatment were used as markers of differentiation. At a concentration of 10(-8)M, OCT and calcitriol significantly induced all markers, and ATRA only the ALP of osteoblast, chondroblast and undifferentiated clonal cells. At the same concentration, 9-cis RA and cholecalciferol induced ALP of chondroblast and osteoblast cells, respectively; ATRA, 9-cis RA and cholecalciferol induced PIP of chondroblast and undifferentiated cells. None of the drugs significantly differentiated fibroblast cells. The ability of these agents to differentiate osteosarcoma cells into cells that exhibit properties of functionally mature osteoblastic bone cells may promote normal osteogenesis and reverse the loss of control of their differentiation.

Surgical salvage from comminuted metatarsal fracture using a weight-bearing pin-putty apparatus in a dog

Comminuted metatarsal fractures in a dog were treated using intramedullary pins externally connected and stabilized by epoxy resin putty and application of a fibreglass cast. Two weeks later the cast was removed. After further 2 weeks application of a Robert-Jones bandage the dog could stand and walk with the pin-putty apparatus in position. The pin-putty apparatus was removed 3 months postoperatively, and the dog resumed normal activity. This fixation method could be an easy, economical and effective alternative treatment for managing comminuted fractures of the metatarsal and possibly metacarpal bones in selected cases.

Differentiation induction of canine osteosarcoma cell lines by retinoids

The effect of two retinoids, all- trans and 9- cis retinoic acid, on the differentiation of three canine osteosarcoma cells (OOS, HOS, and POS) was examined using markers specifically expressed by phenotypic osteoblasts. Both retinoids induced morphologic differentiation in all the canine osteosarcoma cells. Retinoids enhanced cell flattening and spreading, as well as reduction in cell overlapping. Alkaline phosphatase (ALP) activity and ALP staining was enhanced in OOS, and HOS cells, but decreased in POS cells. These results may suggest that OOS and HOS cells have immature osteoblastic properties and POS cells have mature osteoblastic properties. Retinoids decreased osteocalcin production in all the osteosarcoma cells. They induced an increase in production of type I collagen in HOS and POS cells, but a decrease in OOS cells. These results indicate that retinoids induce differentiation of canine osteosarcoma cells, resulting in an altered expression of their malignant phenotype.

Inhibitory effects of 22-oxa-calcitriol and all- trans retinoic acid on the growth of a canine osteosarcoma derived cell-line in vivo and its pulmonary metastasis in vivo

Pulmonary metastasis is a major cause of death and a major obstacle to the successful treatment of canine osteosarcoma. However, the residual capacity of the neoplasia for differentiation and its susceptibility to undergo apoptosis may be used to suppress its growth and metastatic properties. The highly metastasizing POS (HMPOS) canine osteosarcoma cell line which preferentially metastasize to the lungs was used to test the possible efficacy of 22-oxa-calcitriol (OCT) and all- trans retinoic acid (ATRA) to inhibit growth and pulmonary metastasis of the subcutaneously grown osteosarcoma in nude mice. Treatments in vitro, morphologically elongated and increased alkaline phosphatase activity and staining of cells. Tumour growth in vivo was inhibited significantly and the combination treatment of OCT and ATRA (OCT + ATRA) exerted a synergistic and stronger suppression at concentration of 1.0 microg kg(-1)body weight when given subcutaneously three times a week for 5 weeks. The subcutaneous tumours of the control mice consisted of osteoblast-like cells and isolated chondroblast-like cells, but formed several areas of osteoid and increased amount of collagen tissue in all treated mice. Pinpoint macrometastatic nodules developed only in all control mice. Micrometastatic nodule developed only in two of six mice treated with ATRA. However, nodule size and number, and lung wet weight were all reduced significantly. Metastasis were not seen in the mice treated with OCT or OCT + ATRA. This study demonstrated that inhibition of growth and pulmonary metastasis was induced by subcutaneous treatment with these drugs and suggest that both its differentiating and apoptotic inducing activities may be responsible for the antitumour effects. These drugs may be useful in the clinic as an adjunct for the treatment of canine osteosarcoma.

Visceral mast cell tumors in dogs: 10 cases (1982-1997)

OBJECTIVE

To characterize the clinical features of visceral mast cell tumors (MCT) without associated cutaneous involvement in dogs.

DESIGN

Retrospective study.

ANIMALS

10 dogs with histologically confirmed MCT without associated cutaneous lesions.

PROCEDURE

Information on signalment, clinical signs, laboratory examinations, and time from first admission to death was obtained from the medical record of each dog.

RESULTS

Purebred male dogs of miniature breeds appeared to have a higher prevalence of visceral MCT. Clinical signs included anorexia, lethargy, vomiting, and diarrhea. Anemia (n = 7), hypoproteinemia (5), and mastocythemia (5) were detected. Treatments, including glucocorticoids, were not successful. Primary sites of tumors were the gastrointestinal tract (n = 6) and the spleen or liver (1); the primary site was not confirmed in the remaining 3 dogs. In 7 dogs, tumors were categorized as grade II or III, on the basis of histologic findings. The prognoses were poor, and all dogs died within 2 months after first admission.

CONCLUSIONS AND CLINICAL RELEVANCE

Visceral MCT is uncommon in dogs, and the prognosis is extremely poor. Biological behavior and drug susceptibility of visceral MCT may be different from cutaneous MCT. The lack of specific clinical signs may result in delay of a definitive diagnosis. The rapid progression of clinical signs and difficulty in diagnosis contributes to a short survival time.

In vitro retinoid-induced growth inhibition and morphologic differentiation of canine osteosarcoma cells

OBJECTIVE

To determine differentiation and growth inhibition effects of retinoids on canine osteosarcoma cells.

SAMPLE POPULATION

3 osteosarcoma cell lines established from osteosarcomas in dogs.

PROCEDURE

Osteosarcoma cells were incubated with various concentrations of all-trans-retinoic acid and 9-cis-retinoic acid or control medium, counted daily for 10 days, and evaluated for morphologic changes. Synthesis of DNA was measured by use of a cell proliferation ELISA. To analyze effect of retinoids on colony formation on plastic dishes, cells were cultured for 14 days, fixed, and stained; number of colonies was counted.

RESULTS

In a dose-dependent manner, both retinoids induced morphologic differentiation and growth inhibition in the 3 osteosarcoma cell lines and inhibited each cell's ability to form anchorage-dependent colonies.

CONCLUSION AND CLINICAL RELEVANCE

Retinoids induced differentiation of osteosarcoma cells of dogs, resulting in altered expression of their malignant phenotype. Induction of differentiation by retinoids may have potential as an adjunctive treatment for osteosarcoma in dogs.

Induction of functional differentiation and growth inhibition in vitro of canine osteosarcoma by 22-oxacalcitriol, calcitriol and all-trans retinoic acid

The effects of 22-oxacalcitriol (OCT), calcitriol and all-trans retinoic acid (ATRA) on the induction of functional differentiation and growth inhibition of the canine osteosarcoma cell line POS were investigated in vitro via bone differentiation markers and proliferation assays, respectively. The intracellular alkaline phosphatase (ALP) activity and the gamma-carboxyglutamic acid osteocalcin (GLA-OC) and procollagen type I C peptide (PIP) production were used as markers of differentiation. Treatment with 10(-8) M concentrations of all drugs for 72 h significantly inhibited growth (P < 0.0001) and increased ALP activity and GLA-OC and PIP production in POS. OCT, calcitriol and ATRA significantly increased the: ALP activity from 1.58 +/- 0.14 mumol/min/mg protein (mean +/- SD; control) to 2.50 +/- 0.09 (P < 0.0001), 2.30 +/- 0.14 (P < 0.0001) and 2.00 +/- 0.14 (P = 0.0008), respectively; GLA-OC production from 0.71 +/- 0.01 ng/ml (control) to 2.87 +/- 0.01 (P < 0.0001), 2.87 +/- 0.11 (P < 0.0001) and 1.36 +/- 0.06 (P < 0.0001), respectively; and PIP production from 433.91 +/- 23.29 ng/ml (control) to 536.54 +/- 15.46 (P = 0.0002), 497.06 +/- 1.99 (P = 0.0028) and 481.66 +/- 0.01 (P = 0.0104), respectively. This study demonstrated that treatment with these drugs induced a phenotypic maturation of POS cells into cells that exhibit the properties of functionally mature bone cells with parallel growth inhibition. The effects of these drugs on functional differentiation may be useful to complement the progression of a normal osteogenic differentiation process in the sarcoma.

Accelerating effects of chitosan for healing at early phase of experimental open wound in dogs

Chitosan is a polymeric beta(1 --> 4) glucosamine (2-amino-2-deoxy-D-glucose) and N-acetyl-D-glucosamine (2-acetamido-2-deoxy-D-glucose) which has been reported as a wound healing accelerator. In order to evaluate the efficacy of chitosan as an accelerator of wound healing, experimental open skin wounds were made on the dorsal side in three normal beagles. Cottonfiber-type chitosan (degree of acetylation = 18%) was applied for 15 days, and the process of wound healing was evaluated histologically and immunohistochemically. On day 3 postwounding, the chitosan-treated wounds showed histologically severe infiltration of polymorphonuclear (PMN) cells and an increase in effusion compared with that in the control. Granulation was more pronounced by the chitosan treatment on day 9 and 15 postwounding. Immunohistochemical typing of collagen I, III and IV showed increase of the production of type III collagen in the chitosan group. The appearance of mitotic cells occurred numerously in the control on postwounding day 3, and in the chitosan group on postwounding day 6. These results suggest chitosan to be having a function in the acceleration of infiltration of PMN cells at the early stage of wound healing, followed by the production of collagen by fibroblasts.

Arteriovenous malformation of the cervical spinal cord in a dog

An 8-year-old female German Shepherd dog showed first order Horner's syndrome associated with progressive right-sided hemiplegia and mega-oesophagus. Intramedullary and leptomeningeal arteriovenous malformation (AVM) was identified in the cervical spinal cord. The morphological characteristics were arteriovenous shunting, intramedullary multiple thromboses and haemorrhage, non-inflammatory necrosis of white and grey matter around the shunt, and intervening neural gliosis with neovascularization. These findings suggested that the malformation induced a focal circulatory disturbance within the cervical spinal cord and that fatal thrombosis was responsible for the sudden onset of the nervous signs and progressive neurological deterioration. This is the first report of intramedullary spinal AVM in a dog.

1,25-Dihydroxyvitamin D3, recombinant human transforming growth factor-beta 1, and recombinant human bone morphogenetic protein-2 induce in vitro differentiation of canine osteosarcoma cells

Effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), recombinant human transforming growth factor (rhTGF)-beta 1 and recombinant human bone morphogenetic protein (rhBMP)-2 on differentiation in four different canine osteosarcoma cell lines (POS53B, 53C, 53D and 14A) were examined using markers specifically expressed by phenotypic osteoblasts. 1,25(OH)2D3 increased alkaline phosphatase (ALP) activity in one cell line, osteocalcin production in two lines and type I collagen production in three lines. RhTGF-beta 1 increased ALP activity in one clonal cell, osteocalcin production in one clonal cell and type I collagen production in two clonal cells. RhBMP-2 increased ALP activity in all clonal cells, osteocalcin production in two clonal cells and type I collagen production in three clonal cells. Thus, these agents induced differentiation in osteosarcoma cells at different efficacies. Electron microscopic study revealed that these agents increased cellular activity in all cell lines with no evidence of degeneration of cell organelle by drug cytotoxicity. In some cultures treated with either 1,25(OH)2D3 or rhBMP-2, apoptotic cells were observed. Based on the change in markers, rhBMP-2 and 1,25(OH)2D3 seemed to be more effective than rhTGF-beta 1. These agents are potential inducers of apoptosis.

Effects of vitamin D and retinoids on the differentiation and growth in vitro of canine osteosarcoma and its clonal cell lines

Although canine osteosarcoma is one of the most malignant, aggressive and lethal neoplasms originating from undifferentiated bone cells, it may retain some capacity for normal differentiation. The purpose of this study was to ascertain if the residual capacity for differentiation could be used to suppress its malignant properties. We tested the efficacy of vitamin D and retinoids in inducing differentiation and inhibiting growth of the POS canine osteosarcoma and four of its clonal cell lines, POS 14A (fibroblast type), POS 53B (chondroblast type), POS 53C (undifferentiated type) and POS 53D (osteoblastic type). Treatment with 10(-10)to 10(-8)M concentrations of calcitriol, OCT, cholecalciferol, all-trans retinoic acid (ATRA) and 9-cis retinoic acid for 48-120 hours changed the morphology of POS, POS 53B, POS 53C and POS 53D cells to cells that were elongated and spindle-shaped. Increased number of cytoplasmic organelles and pronounced nuclear activities were induced by concentrations of 10(-8)M and 10(-7)M for 120 hours. All drugs at concentrations of 10(-10)to 10(-8)M for 72 hours inhibited POS growth dose-dependently. OCT significantly reduced the cell number in all cell lines when used at concentrations between 10(-9)and 10(-8)M for 72 hours and exerted significant anti-proliferative effects for eight days culture. This study demonstrated that changed morphology and inhibition of growth was induced by treatment of the cells with these vitamins, that the loss of control of differentiation in the neoplasia was not irreversible and that these drugs may be useful in the clinic.

Plasma atrial and brain natriuretic peptide levels in dogs with congestive heart failure

Plasma concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were measured in 6 dogs with experimental mitral regurgitation (MR) and 19 canine patients with asymptomatic and symptomatic congestive heart failure (CHF). In dogs with experimental MR, ANP and BNP concentrations were significantly correlated with pulmonary capillary wedge pressure (PCWP) (ANP; r=0.852, P=0.0004, BNP; r=0.832, P=0.0008). ANP level was shown to have a predominant effect on PCWP in comparison with BNP using multiple regression analysis. In canine patients with asymptomatic and symptomatic CHF, ANP and BNP concentrations were significantly different among the heart failure classes according to the New York Heart Association functional classification (ANP; P=0.0165, BNP; P=0.0005). In addition, ANP and BNP levels in dogs with decompensated heart failure (n=10) significantly increased in comparison with those in dogs with compensated heart failure (n=9). There was however no correlation between ANP and BNP levels in each heart failure class. In conclusion, plasma ANP and BNP levels may become predictors of PCWP and the severity of heart failure in dogs with MR, although further investigations on ANP and BNP levels in more clinical cases are required.

Establishment and characterization of the growth and pulmonary metastasis of a highly lung metastasizing cell line from canine osteosarcoma in nude mice

Highly lung metastasizing model of canine osteosarcoma in nude mice was established from five subcutaneous implantation cycles of lung tumor deposits. The selection of cells with increased metastatic properties from the parent POS canine osteosarcoma cell line recovered medium sized and polygonal Highly Metastasizing POS cells (HMPOS). The doubling time of HMPOS and POS in culture averaged 30 +/- 1.2 hr and 32 +/- 1.3 hr respectively, and their cell growth patterns in vitro were comparable to their in vivo growth patterns. HMPOS cells produced more tumor deposits (> 20 nodules, > 1 -mm in diameter) of various sizes with replacement of lung tissues at 12 weeks after implantation. POS cells produced fewer and smaller lung deposits (< 10 nodules, 1-mm in diameter). Tumor size and number of metastatic tumor deposits showed a regular association. HMPOS cells developed an osteoblastic type of cellular differentiation subcutaneously and in the lungs. HMPOS micrometastasis along the alveolar walls and blood vessels at 4 weeks averaged 6-7 small tumor locus. Each micrometastatic locus contained an average of 5-7 tumor cells, and developed a pleomorphic osteoblastic type of cellular differentiation. An average of 4 macrometastatic nodules could be seen at 6 weeks, composed of an average of 23 tumor cells, 10 nodules at 8 weeks, 12 nodules at 10 weeks and 20 nodules at 12 weeks. These model provides an opportunity for the evaluation of new treatments against canine lung metastatic osteosarcoma in a nude mice model.

Peri-operative changes in echocardiographic measurements and plasma atrial and brain natriuretic peptide concentrations in 3 dogs with patent ductus arteriosus

Peri-operative changes in echocardiographic measurements and plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were investigated for 1 month in 3 dogs with patent ductus arteriosus (PDA). Post-operative left ventricular end-diastolic dimention and fractional shortening decreased in all cases. Pre-operatively increased plasma ANP concentrations reduced dramatically after the operation. Peri-operative changes in plasma BNP levels had slightly S-shaped curves in all cases. These observations suggest that post-operative responsiveness of ANP and cardiac function are rapid in comparison with cardiac morphological changes, and BNP has a different pathophysiological significance from ANP in dogs with PDA.

Surgical correction of temporomandibular joint ankylosis in two cats

Two cats with temporomandibular joint ankylosis were examined. Difficulty in opening the mouth and malocclusion were associated with trauma and fracture around the zygomatic arch and the condyle of the mandible after an automobile accident. Unilateral condylectomy or aggressive caudal mandibulectomy was performed to improve quality of life. Excision arthroplasty of the temporomandibular joint improved mandibular function and appearance. Some malocclusion remained but had no clinical significance.

Apoptosis induction of POS canine osteosarcoma cells by vitamin D and retinoids

Vitamin D3: 1-alpha, 25(OH)2D3 (calcitriol), 22-oxa-1,25(OH)2D3 (OCT), cholecalciferol (vitamin D3), and retinoids: all-trans retinoic acid (ATRA) and 9-cis retinoic acid, induced morphological changes in POS canine osteosarcoma cells into elongated, spindle or fibroblast like-shaped cells, and apoptotic like cell death characterized by cell shrinkage, condensation and margination of the nucleus for all drugs at 10(-6)M-10(-9)M after 72 to 120 hr culture. Apoptosis as shown by DNA laddering was induced at 48 hr by all drugs at 10(-6)M, 10(-7)M at 96 hr, 10(-8)M and 10(-9)M at 120 hr respectively. These vitamins are suggested to adjunct antineoplastic agents in canine osteosarcoma therapy by induction of apoptosis.

Establishment and characterization of two cell lines derived from canine spontaneous osteosarcoma

Two new canine osteosarcoma cell lines were established. One (OOS) was established from a 10-year-old female maltese dog with mandibular osteosarcoma and the other (HOS) from a 7-year-old male mongrel dog with scapular osteosarcoma. Histopathological types of OOS and HOS were mixed and fibroblastic cell type, respectively. Transmission electron microscopic features of HOS revealed prominent rough endoplasmic reticulum, suggesting higher malignancy comparing to OOS. Doubling time of OOS and HOS were 45.0 +/- 0.5 hr and 42.0 +/- 0.1 hr, respectively. Alkaline phosphatase activities of OOS and HOS were quite low. Histological features of tumor tissues produced by transplantation of these cells into nude mice were identical to those of original osteosarcomas.

Femoral nonunion fracture treated with recombinant human bone morphogenetic protein-2 in a dog

This is the first report on successful treatment of spontaneous nonunion fracture of a dog by use of recombinant human bone morphogenetic protein-2 (rhBMP-2). A 4-year-old Pomeranian dog with a 2-year history of femoral nonunion fracture was treated with implantation of rhBMP-2. The dog had received surgical correction twice prior to the admission but radiography of the affected limb revealed a typical figure of nonunion fracture. Glossly, the fractured ends were sclerotic and the area between the ends was filled with fibrous tissue. After debridement the femoral shaft was fixed by an 8-hole plate. rhBMP-2 at a total dose of 256 micrograms was implanted with a synthetic carrier into the 8-mm defect formed by the debridement. Callus formation responding to rhBMP-2 was radiographically observed at 2 weeks after implantation and the defect reached radiographic union by 8 weeks after implantation. The plate was removed at 9 months after implantation. Any complications were not observed for 5 months after removal of the plate.

Repair of ulnar segmental defect by recombinant human bone morphogenetic protein-2 in dogs

The efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with poly D, L lactic-co-glycolic acid (PLGA)/gelatin sponge complex (PGS) as a carrier on the repair of segmental long-bone defects was evaluated using an ulnar model in dogs. The defect was 2 cm in length and was fixed with bone plating. After implantation of PGS with or without rhBMP-2, the repair process of the defect was evaluated by serial radiography until 16 postoperative weeks. All defects treated with 160 micrograms or 640 micrograms of rhBMP-2/PGS revealed bone union radiographically by 12 postoperative weeks, whereas all defects treated with PGS alone revealed no radiographic evidence of healing throughout the experimental period. In defects treated with 40 micrograms of rhBMP-2/PGS, new bone appeared partially at the defects but did not accomplish union. Bone mineral contents at the defect sites after harvest at 16 weeks postoperatively were significantly (p < 0.05) higher in those treated with 160 micrograms or 640 micrograms of rhBMP-2 than in those treated with 40 micrograms of rhBMP-2 or PGS alone. Histologically, defects radiographically diagnosed as having achieved union showed the appearance of cortical bone and bone marrow cells. These findings suggest the use of rhBMP-2/PGS as a potential bone graft substitute in reconstructive surgery in dogs.

Ultrasonographic evaluation of portal vein hemodynamics in experimentally bile duct ligated dogs

The purpose of this study was to evaluate the relationship between the results of laboratory examinations and ultrasonographic findings, especially portal vein hemodynamics in experimentally bile duct ligated dogs. Biliary obstruction was accomplished by surgically occluding the common bile duct in five dogs. All the dogs became visibly jaundiced within 24 hours after surgery. The total protein and albumin/globulin ratio showed a gradual decrease throughout the examination period, while blood urea nitrogen reached its peak in the 6th week and decreased to pre ligation values by the 10th week. Similar trends were noted in the alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and direct and total bilirubin. Total cholesterol and fasting serum bile acid levels rapidly increased after surgery to peak values between the 2nd and 4th week, and then gradually decreased, but still remained high throughout the experiment period. The portal flow volume and velocity significantly (p < 0.05) decreased while only a slight increase was noted in the congestion index after bile duct ligation. The cross sectional area of the portal vein changed insignificantly. Bile duct and gallbladder distention was evident within the 1st week after ligation but there was little change in the echogenicity of the liver parenchyma. The results of this study suggest that the determination of Doppler ultrasound parameters of hepatic hemodynamics, especially the portal vein flow indices, may contribute to a better noninvasive assessment of the canine patient with biliary obstructive disease.

Ultrasonography, biochemical and hematological profiles in liver disease caused by intravenous administration of dimethylnitrosamine in dogs

The results of liver function tests and ultrasonographical findings were analysed in 7 dogs that were intravenously injected dimethylnitrosamine (DMNA 2 mg/kg body weight) on 2 consecutive days each week for 10 weeks. Typical clinical signs and similar changes in liver enzyme concentrations that develop in dogs with natural cirrhosis were observed in this canine model. Severe anaemia and a significant reduction in the platelet numbers occurred in the dogs that died in the 5th week, while in all the other dogs these parameters decreased slightly. Serum total protein and the albumin/globulin ratio decreased gradually while the alkaline phosphatase, alanine amino transferase, aspartate amino transferase and gamma glutamyl transpeptidase activities increased significantly (p < 0.05) in all dogs after beginning the administration of DMNA. Ultrasound findings of a coarsened and heterogeneous echo pattern with increased echogenicity that are characteristic of canine cirrhosis were noticed at the same time when the changes in liver enzymes became evident. Present results suggest that ultrasonography in conjunction with liver function tests may be useful in the evaluation of experimentally induced liver cirrhosis.

Inhibitory effects of glucocorticoids on proliferation of canine mast cell tumor

The inhibitory effect of glucocorticoids (GCs) on proliferation of canine mast cell tumor (MCT) was studied using two types of MCT cells; JuMC cells and LuMC cells derived from spontaneous canine cutaneous and intestinal MCT, respectively. In in vitro study, growth of JuMC cells was significantly inhibited with more than 1 nM GCs and apoptotic-like cell death was seen, while that of LuMC cells was never inhibited even with 10 microM GCs. Growth rate of masses in nude mice developed by inoculation of JuMC cells was reduced in a dose-dependent manner by administration of GC, while growth inhibition of masses developed by inoculation of LuMC cells was minimal with increasing GC doses. Competitive binding studies and Scatchard analysis demonstrated the presence of high-affinity, low capacity GC receptors in both JuMC and LuMC cells. Kd was estimated to be 1.30 nM in JuMC cells and 0.45 nM in LuMC cells, respectively. It is concluded that canine cutaneous MCT cells responded to GCs in vitro and in vivo, whereas intestinal MCT cells did not, though both types of cells had specific GC receptors.

Histopathological changes in digits of dairy cows affected with sole ulcers

Forty-eight digits of 8 dairy cows, which had been diagnosed as sole ulcers in one or two hooves, were examined histopathologically and classified into 5 grades on the basis of the severity of the circulatory disturbances and of keratogenesis. All the cows had significantly higher grades than normal cows. Although hind lateral digits were most severely damaged, there were no significant differences in the grades among claw positions except hind lateral digits. From these results, it is suggested that the cows affected with sole ulcers had some systemic factors predisposing all the digits to digital disorders.

Syringomyelia and hydrocephalus in a dog

A 7-year-old spayed female Pomeranian with a 6-month history of progressive paraparesis was determined to have syringomyelia accompanied with hydrocephalus. Magnetic resonance imaging clearly revealed severe syringomyelia in the cervical portion of the spinal cord, which was directly connected to the marked dilated fourth ventricle. Acetazolamide was prescribed for 3 weeks, but the neurologic deficits progressed. Laminectomy of the first and second vertebrae, which is one method of treating this type of syringomyelia in human beings, was performed, and then, acetazolamide was continued. The dog had partial amelioration, and further deterioration was not evident in the 12 months after surgery.

Prognosis of malignant mammary tumor in 53 cats

Medical records of fifty-three cats diagnosed as malignant mammary tumor from 1982 to 1993 were reviewed. The mean age of the cats at diagnosis was 11.1 years, and Japanese domestic and Siamese breeds were predominant. Survival rates after 1 and 2 years of diagnosis were 31.8% and 17.7%, respectively, suggesting poor prognosis of this malignancy. The survival time was significantly associated with tumor size or WHO clinical stage, but not with breed, age, or gender. Twenty-nine cats with pulmonary metastasis died within 5 months following metastatic detection. Postoperative prognosis was significantly related to the tumor size at surgery, but not with type of surgery and adjuvant chemotherapy using cyclophosphamide and/or vincristine.

Effects of 20 alpha-hydroxysteroid dehydrogenase and its inhibitors on canine osteosarcoma cell growth in vitro

Cytotoxic effect of progesterone on the neoplastic cells was investigated using POS cells, a cell line established from a spontaneous osteosarcoma in a dog. The 20 alpha-HSD activity of POS cells was 0.85 +/- 0.26 NADPH nmol/min mg protein, demonstrating that a considerable activity was present in this tumor cell. When progesterone was added to the medium and cultured for 48 hr, progesterone dose-dependently inhibited the cell growth, showing that progesterone was cytotoxic on this osteosarcoma cells in vitro. In order to assure the role of 20 alpha-HSD on the cell growth, various concentrations of four types of steroid derivatives, STZ 20, 23, 25, and 26, potent inhibitors of 20 alpha-HSD, were added to the medium with 0.1 microM progesterone. Then, the POS cell growth was more strongly inhibited, which may suggest that the cytotoxicity of progesterone was enhanced by inactivation of 20 alpha-HSD by STZs. From these results, POS osteosarcoma cells have 20 alpha-HSD, which might play an important role in tumor cell growth against the cell toxicity of progesterone.