Non-immunosuppressive FTY720-derivative OSU-2S mediates reactive oxygen species-mediated cytotoxicity in canine B-cell lymphoma

OSU-2S is a FTY720 (Fingolimod) derivative that lacks immunosuppressive properties but exhibits strong anti-tumour activity in several haematological and solid tumour models. We have recently shown OSU-2S to mediate potent cytotoxicity in human mantle cell lymphoma cell lines and primary cells. We report here the pre-clinical activity of OSU-2S in spontaneous B-cell lymphoma of dogs which shares many characteristics of human lymphoma. OSU-2S mediated apoptosis in canine B-cell lines and primary B-cell lymphoma cells obtained from spontaneous lymphoma bearing dogs. OSU-2S induced reactive oxygen species (ROS) in canine lymphoma cells and inhibition of ROS partially rescued OSU-2S-mediated cell death. These studies provide a rational basis for the use of spontaneous lymphoma in pet dogs as a preclinical large animal model for the development of OSU-2S as small molecule for treating people and dogs with lymphoma.

Molecular profiling reveals prognostically significant subtypes of canine lymphoma

We performed genomewide gene expression analysis of 35 samples representing 6 common histologic subtypes of canine lymphoma and bioinformatics analyses to define their molecular characteristics. Three major groups were defined on the basis of gene expression profiles: (1) low-grade T-cell lymphoma, composed entirely by T-zone lymphoma; (2) high-grade T-cell lymphoma, consisting of lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified; and (3) B-cell lymphoma, consisting of marginal B-cell lymphoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Interspecies comparative analyses of gene expression profiles also showed that marginal B-cell lymphoma and diffuse large B-cell lymphoma in dogs and humans might represent a continuum of disease with similar drivers. The classification of these diverse tumors into 3 subgroups was prognostically significant, as the groups were directly correlated with event-free survival. Finally, we developed a benchtop diagnostic test based on expression of 4 genes that can robustly classify canine lymphomas into one of these 3 subgroups, enabling a direct clinical application for our results.

A tumor-related lymphoid progenitor population supports hierarchical tumor organization in canine B-cell lymphoma

BACKGROUND

Tumors have heterogeneous properties, which could be explained by the existence of hierarchically and biologically distinct tumor cells such as tumor-initiating cells (TICs). This model is clinically important, as TICs are promising targets for cancer therapies. However, TICs in spontaneous B-cell lymphoma have not been conclusively identified.

HYPOTHESIS/OBJECTIVES

Tumor cells with a progenitor phenotype exist in B-cell lymphoma, reflecting a hierarchical organization.

ANIMALS

Twenty-eight client-owned dogs with previously untreated B-cell lymphoma and 6 healthy dogs.

METHODS

This was a prospective study. Flow cytometry was used to identify lymphoid progenitor cells (LPCs) that coexpressed hematopoietic progenitor antigens CD34, CD117, and CD133, with lymphoid differentiation markers CD21 and/or CD22 in B-cell lymphoma. The polymerase chain reaction for antigen receptor rearrangements was used to analyze clonality and relatedness of tumor populations. A xenograft model with NOD/SCID/IL-2Rγ(-/-) mice was adapted to expand and serially transplant primary canine B-cell lymphoma.

RESULTS

LPCs were expanded in lymph nodes from 28 dogs with B-cell lymphoma compared with 6 healthy dogs (P= .0022). LPCs contained a clonal antigen receptor gene rearrangement identical to that of the bulk of tumor cells. Canine B-cell lymphoma xenografts in recipient mice that maintained LPCs in the tumors were recurrently observed.

CONCLUSIONS AND CLINICAL IMPORTANCE

These results suggest the presence of a hierarchy of tumor cells in B-cell lymphoma as has been demonstrated in other cancers. These findings have the potential to impact not only the understanding of lymphoma pathogenesis but also the development of lymphoma therapies by providing novel targets for therapy.

Quantification of plasma DNA as a prognostic indicator in canine lymphoid neoplasia

Dogs have a similar incidence of spontaneous cancers as people, and a noninvasive test to monitor disease status in dogs would be of great value. Humans with cancer often have increased levels of cell-free circulating DNA in their plasma, which has shown promise for diagnosis, prognosis and detection of residual disease. We hypothesized that dogs with cancer have increased circulating DNA compared with healthy dogs or dogs with non-neoplastic diseases. Plasma DNA was measured in 40 healthy dogs, 20 dogs with non-neoplastic diseases and 80 dogs with cancer. The reference interval for plasma DNA in healthy dogs was 1-15 ng mL(-1). Dogs with lymphoma and lymphoid leukaemia had significantly higher concentrations (range: 0-91 ng mL(-1), P < 0.0001). Antigen receptor rearrangement assays suggest that plasma DNA had the same clonality as the primary lymphoid tumours. Dogs with lymphoid neoplasia and plasma DNA >25 ng mL(-1) had shorter remission times than those with < 25 ng mL(-1) (P = 0.0116). In contrast to humans, where increased plasma DNA is seen in many diseases, dogs with nonlymphoid malignancies and non-neoplastic diseases had plasma DNA concentrations similar to healthy dogs. This study shows that a portion of dogs with lymphoid neoplasia have increased tumour-derived plasma DNA, which serves as a negative prognostic indicator.

3-Phosphoinositide-dependent protein kinase-1/Akt signalling and inhibition in a canine prostate carcinoma cell line

Deregulation of the 3-phosphoinositide-dependent protein kinase-1 (PDK-1)/Akt signalling pathway is associated with prostate cancer development and progression. Inhibition of PDK-1/Akt signalling can be achieved using structurally optimized celecoxib derivatives such as OSU-03012. In this study, we treated the novel canine prostate cancer cell line, Ace-1, with OSU-03012 or dimethyl sulphoxide in vitro. We found that Akt was constitutively phosphorylated in the canine prostate cancer cell line Ace-1 and that there was a dose-dependent decrease in cell viability, and Akt and glycogen synthase kinase-3beta phosphorylation, in response to OSU-03012 treatment. This was accompanied by a dose-dependent increase in apoptosis. These data suggest that Akt signalling pathway inhibition is a potential strategy for the treatment of dogs with prostate cancer and that canine prostate cancer is a relevant large animal model for evaluating Akt pathway inhibitors such as OSU-03012 for use in people.

NOD/SCID mouse model of canine T-cell lymphoma with humoral hypercalcaemia of malignancy: cytokine gene expression profiling and in vivo bioluminescent imaging

Lymphoma is a malignant neoplasm arising from B or T lymphocytes. In dogs, one-third of lymphomas are highly aggressive multicentric T-cell lymphomas that are often associated with humoral hypercalcaemia of malignancy (HHM). There are no cell lines or animal models to investigate the pathogenesis of T-cell lymphoma and HHM in dogs. We developed the first xenograft model by injecting lymphoma cells from an Irish Wolfhound intraperitoneally into NOD/SCID mice. The mice developed multicentric lymphoma along with HHM and increased parathyroid hormone-related protein (PTHrP) as occurs in dogs with T-cell lymphoma. Using cytokine complementary DNA arrays, we identified genes that have potential implications in the pathogenesis of T-cell lymphoma. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) of T-cell lymphoma samples from hypercalcaemic canine patients showed that PTHrP likely plays a central role in the pathogenesis of HHM and that hypercalcaemia is the result of a combinatorial effect of different hypercalcaemic factors. Finally, we monitored in vivo tumour progression and metastases in the mouse model by transducing the lymphoma cells with a lentiviral vector that encodes a luciferase-yellow fluorescent protein reporter and showed that in vivo trafficking patterns in this model were similar to those seen in dogs. This unique mouse model will be useful for translational research in lymphoma and for investigating the pathogenesis of T-cell lymphoma and HHM in the dog.

Inactivation of the p16 cyclin-dependent kinase inhibitor in high-grade canine non-Hodgkin's T-cell lymphoma

The significance of p16/Rb tumor suppressor pathway inactivation in T-cell non-Hodgkin's lymphoma (NHL) remains incompletely understood. We used naturally occurring canine NHL to test the hypothesis that p16 inactivation has specific pathologic correlates. Forty-eight samples (22 T-cell NHL and 26 B-cell NHL) were included. As applicable, metaphase- or array-based comparative genomic hybridization, Southern blotting, promoter methylation, and Rb phosphorylation were used to determine the presence, expression, and activity of p16. Fisher's exact test was used to test for significance. Deletion of p16 (or loss of dog chromosome 11) was restricted to high-grade T-cell NHL (lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified). These were characterized by a concomitant increase of tumor cells with Rb phosphorylation at canonical CDK4 sites. Rb phosphorylation also was seen in high-grade B-cell NHL (diffuse large B-cell lymphoma and Burkitt-type lymphoma), but in those cases, it appeared to be associated with c-Myc overexpression. The data show that p16 deletion or inactivation occurs almost exclusively in high-grade T-cell NHL; however, alternative pathways can generate functional phenotypes of Rb deficiency in low-grade T-cell NHL and in high-grade B-cell NHL. Both morphologic classification according to World Health Organization criteria and assessment of Rb phosphorylation are prognostically valuable parameters for canine NHL.

Salivary gland neoplasia in the dog and cat: survival times and prognostic factors

Twenty-four dogs and 30 cats with histopathologically confirmed salivary gland neoplasia were retrospectively reviewed in a multi-institutional study. The predominant presenting complaint for animals with salivary gland neoplasia was that of a mass being noted by the owner; other common complaints included halitosis, dysphagia, and exophthalmia. Siamese cats were overrepresented, indicating a possible breed predisposition. The most common histopathological type was simple adenocarcinoma. Cats had more advanced disease at diagnosis than did dogs, and clinical staging was prognostic in dogs. The median survival times for dogs and cats were 550 days and 516 days, respectively.

Ubiquitous expression of marker transgenes in mice and rats

The ability to unambiguously mark a cell's genotype is essential for studies in which genetically distinct cell populations must be distinguished from one another in vivo. One approach to this challenge has been the creation of transgenic mice expressing a transgene marker that is easily detectable, with no background staining. Multiple transgenic mouse strains bearing constructs with different combinations of promoter elements and coding sequences have been described, each with its own advantages and limitations. In this report we describe the use of an 800-bp promoter fragment isolated from the beta(geo) integration site in ROSA26 mice to target expression of two marker genes. We demonstrate that the ROSA26 promoter directs ubiquitous expression of human placental alkaline phosphatase and enhanced green fluorescent protein during embryonic and postnatal development in mouse and rat. We further demonstrate the general utility of these transgenes for marking donor cells in transplantation studies.

Expression of stem cell factor receptor (c-kit) by the malignant mast cells from spontaneous canine mast cell tumours

Stem cell factor receptor (SCFR, c-kit), normally expressed on haematopoietic and mast cells, plays a regulatory role in cellular growth and differentiation. Dysregulated expression of SCFR may contribute to neoplastic transformation. We investigated expression of SCFR on malignant canine mast cells obtained directly from spontaneous canine mast cell neoplasms, in an attempt to determine whether these undifferentiated cells maintained expression of this growth-promoting cytokine receptor. Malignant mast cells (histological grade 2) from skin tumours or lymph node metastases were collected from canine patients, and SCFRs were detected by flow cytometric analysis of these cells. All of the tumours bound mouse and canine recombinant stem cell factor (SCF), indicating that the cells not only expressed SCFRs, but that the receptors possessed the functional property of ligand binding. Immunoglobulin Fc receptors for canine IgE were identified on these cells by flow cytometry, a further indication that the cells analysed were mast cells and retained some differentiated features. Immunohistochemical analysis of formalin-fixed, paraffin wax-embedded mast cell tumour biopsies confirmed expression of SCFRs by malignant cells from each tumour. The relative binding of SCF to suspensions of tumour cells, as assessed by flow cytometry, correlated with the intensity of immunolabelling for SCFR in sections of the same tumours, suggesting variability in SCFR expression between tumours. Agarose gel electrophoresis of the products of SCFR reverse transcription-polymerase chain reaction derived from each tumour had the molecular weight predicted for canine SCFR cDNA on the basis of the mouse and human counterparts. This further confirmed SCFR expression by malignant canine mast cells. Taken together, these results show that a membrane receptor capable of triggering cell growth is expressed by malignant canine mast cells, suggesting a role for this receptor in the aetiology of canine mast cell cancer. This relatively common malignancy of the dog would seem to present an opportunity for the investigation of the potential role of the SCF/SCFR pathway in the development of spontaneous malignancies of mast cells.

Frequency of argyrophilic nucleolar organizer regions in fine-needle aspirates and biopsy specimens from mast cell tumors in dogs

OBJECTIVE

To determine for mast cell tumors in dogs whether frequency of argyrophilic nucleolar organizer regions (AgNOR) determined by examining fine-needle aspirates (FNA) correlated with frequencies determined by examining biopsy specimens or with histologic grade.

DESIGN

Case series.

ANIMALS

25 dogs with 32 histologically confirmed tumors.

PROCEDURE

Biopsy specimens and FNA were collected from each tumor. Histologic grade and AgNOR frequency were determined.

RESULTS

Frequency of AgNOR in FNA was significantly correlated with frequency in biopsy specimens and was significantly associated with histologic grade of the tumor.

CLINICAL IMPLICATIONS

Determining AgNOR frequency in FNA of mast cell tumors in dogs is a rapid, minimally invasive means of obtaining information that potentially could be used to help predict biological behavior of the tumor and to guide clinicians and owners in making decisions about further diagnostic tests and treatment.

Assessment of potential doubling time (Tpot), argyrophilic nucleolar organizer regions (AgNOR), and proliferating cell nuclear antigen (PCNA) as predictors of therapy response in canine non-Hodgkin's lymphoma

The predictive potential of several proliferation indices for therapeutic outcome was investigated in 55 dogs with spontaneously occurring non-Hodgkin's lymphoma (NHL). Indices included potential doubling time (Tpot), argyrophilic nucleolar organizer region (AgNOR) frequency, and proliferating cell nuclear antigen labeling index (PCNA-LI). All tumors were of intermediate- or high-grade histology as assessed by the Working Formulation, and all dogs presented with disease of advanced clinical stage. All tumors were treated with an identical chemotherapeutic protocol. Tpot determination by a bromodeoxyuridine (BrdU) delayed-biopsy technique was readily applied in the dog. AgNOR frequency and PCNA-LI were easily obtained from archival, formalin-fixed, paraffin-embedded canine tissues. When accounting for all other prognostic variables by employing multivariate analysis, Tpot (p=0.017), and AgNOR frequency (p=0.021), but not PCNA-LI, were predictive of first remission duration. AgNOR frequency (p=0.033) was also predictive of survival time, and the predictive potential of Tpot approached significance (p=0.076). We conclude that Tpot and AgNOR frequency can be used as predictors of outcome in dogs with NHL, and spontaneous NHL in the dog may have significant potential as a model for further characterization of the association between tumor cell kinetics and chemoresponsiveness.

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine adjuvant immunotherapy for splenic hemangiosarcoma in the dog: a randomized multi-institutional clinical trial

Canine splenic hemangiosarcoma (HSA) is a spontaneous tumor with high metastatic potential. Despite surgical excision, most dogs die within 2 months of diagnosis as a result of widespread visceral metastasis. This study was designed to determine the efficacy of liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) when used in combination with splenectomy and systemic chemotherapy for the treatment of HSA in the dog. Thirty-two dogs with HSA and without gross evidence of metastases were treated with splenectomy, stratified by clinical stage, and randomized to receive doxorubicin/cyclophosphamide chemotherapy and either L-MTP-PE immunotherapy or lipid equivalent (placebo liposomes). Dogs were subsequently followed to determine disease-free survival and overall survival times. The effects of L-MTP-PE on serum tumor necrosis factor-alpha and interleukin 6 activity were assessed on a small subset of dogs. Dogs receiving L-MTP-PE had significantly prolonged disease-free survival (P = 0.037) and overall survival (P = 0.029) compared with dogs receiving placebo. Dogs with clinical stage I disease had significantly prolonged disease-free survival (P = 0. 026) and overall survival (P = 0.017) compared with dogs with clinical stage II disease. Dogs receiving L-MTP-PE had significantly greater serum tumor necrosis factor-alpha (P < 0.001) and interleukin 6 (P = 0.007) activities compared with placebo-treated dogs. L-MTP-PE has significant antimetastatic activity in highly malignant, spontaneously occurring, splenic HSA in the dog. Canine HSA may have potential as a large animal model for additional investigation of antimetastatic chemoimmunotherapy.

GFAP promoter directs astrocyte-specific expression in transgenic mice

Glial fibrillary acidic protein (GFAP) is an intermediate-filament protein expressed abundantly and almost exclusively in astrocytes of the CNS. We are studying transcriptional regulation of the GFAP gene to gain insight into astrocyte function and also to develop an astrocyte-specific expression system for manipulating brain physiology. In this work, we have produced transgenic mice carrying the bacterial lacZ reporter gene linked to a 2.2 kilobase 5'-flanking sequence derived from the human GFAP gene that previously was shown to direct astrocyte-specific transcription in cultured cells. We report that this promoter directs expression to astrocytes in the CNS. In addition, the upregulation of GFAP gene activity that follows injury to the brain was mimicked by the transgene. One of the transgenes was found to be X-linked and appeared to undergo the usual random inactivation that achieves gene dosage compensation in females. The brains of hemizygous females stained uniformly rather than displaying mosaic patches, indicating that astrocytes intermingle following their formation. The specific expression of the GFAP-lacZ transgene means that it is now possible to target expression of other heterologous genes to astrocytes in vivo, and to study the mechanisms for reactive gliosis at the DNA level.

Toxicology of selected pesticides, drugs, and chemicals. Illicit and abused drugs

Toxicoses involving exposures to illicit and abused substances are an occasional problem in veterinary patients. The difficulties of clinical diagnosis and the importance of obtaining a good history are emphasized. A discussion of some of the more common poisonings is presented, including available sources, clinical signs, toxicity, metabolism, mechanism of action, and the treatment for each agent.

Preferential grazing by cattle on glyphosate-treated fescue pastures

Cattle grazing preferences on fescue pastures treated with the herbicide glyphosate at a rate of 2.52 kg/ha by surface application were determined, and the time course of the effect was characterized. An initial grazing preference for treated pasture was observed for the first 5 to 7 days. Over the next 15 days, this preference was lost because of decreasing amounts of herbicide on the herbage and/or desiccation of the herbage.

Industrial lead contamination of an Illinois wildlife refuge and indigenous small mammals

Deer mice (Peromyscus maniculatus) were trapped from a sand prairie at various distances from an adjacent battery lead reclamation plant. Analysis of liver, kidney, and bone for lead concentrations showed an increase of tissue lead concentrations over controls to a distance of approximately 400 m. Soil and plant lead concentrations roughly correlated with the findings in deer mouse tissues. At higher tissue lead concentrations, acid-fast staining intranuclear inclusions within renal tubular epithelial cells were an occasional finding.