ß-Catenin transcriptional activity is minimal in canine osteosarcoma and its targeted inhibition results in minimal changes to cell line behaviour.

Canine osteosarcoma (OS) is an aggressive malignancy associated with poor outcomes. Therapeutic improvements are likely to develop from an improved understanding of signalling pathways contributing to OS development and progression. The Wnt signalling pathway is of interest for its role in osteoblast differentiation, its dysregulation in numerous cancer types, and the relative frequency of cytoplasmic accumulation of ß-catenin in canine OS. This study aimed to determine the biological impact of inhibiting canonical Wnt signalling in canine OS, by utilizing either ß-catenin siRNA or a dominant-negative T-cell factor (TCF) construct. There were no consistent, significant changes in cell line behaviour with either method compared to parental cell lines. Interestingly, ß-catenin transcriptional activity was three-fold higher in normal canine primary osteoblasts compared to canine OS cell lines. These results suggest canonical Wnt signalling is minimally active in canine OS and its targeted inhibition is not a relevant therapeutic strategy.

Third eyelid gland neoplasms of dogs and cats: a retrospective histopathologic study of 145 cases.

PURPOSE: To describe the various types of primary neoplasms affecting the third eyelid (TEL) gland of dogs and cats. METHODS: A retrospective search of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) database was performed. Veterinary ophthalmologists, primary care veterinarians, and, when appropriate, owners were contacted for patient follow-up information. Patient data points collected included species, age, sex, breed, laterality, tumor type, surgical margins, recurrence, metastasis, and length of follow-up. RESULTS: A total of 127 canine and 18 feline cases met the inclusion criteria. The most common canine TEL gland tumor was adenocarcinoma (n = 108; 85.0%) followed by adenoma (n = 18; 14.2%) and squamous cell carcinoma (SCC) (n = 1; 0.8%). For canine cases with follow-up information available (n = 62), 8.1% had confirmed or suspected metastasis and 11.3% had confirmed or suspected local recurrence of disease. The most common feline TEL gland tumor was adenocarcinoma (n = 15; 83.3%) followed by SCC (n = 3; 16.7%). For feline cases with follow-up information available (n = 9), 40.0% had confirmed or suspected metastasis and 30.0% had confirmed or suspected local recurrence of disease. CONCLUSIONS: This study determined that adenocarcinoma was the most common third eyelid gland tumor in both dogs and cats. The overall survival times were less, and metastatic occurrence and recurrence rates appeared to be higher for feline tumors as compared to those diagnosed in dogs. This is the first report of SCC originating from glandular ductular epithelium.

Clinical effects of vinorelbine administration in the management of various malignant tumor types in dogs: 58 cases (1997-2012).

OBJECTIVE: To evaluate the effectiveness of vinorelbine in the management of various malignant tumor types in dogs. DESIGN: Retrospective case series. ANIMALS: 58 dogs with malignant tumors, including pulmonary carcinoma (n = 31), histiocytic sarcoma (9), mast cell tumor (5), lymphoma (4), melanoma (2), and 7 other tumor types (1 each). PROCEDURES: Medical records of dogs treated with vinorelbine from December 1997 to December 2012 were reviewed for data regarding signalment, clinical signs, physical examination findings, clinicopathologic test results, diagnostic imaging results, vinorelbine doses and dose frequency, surgery and radiotherapy details when applicable, other chemotherapeutics administered, and outcomes. Descriptive, comparative, and survival statistics were computed for all dogs and for dogs by histologic subgroup of tumors. RESULTS: Vinorelbine was administered palliatively to 44 (76%) dogs. One (2%) dog had a complete response for 162 days, 5 (11%) dogs had a partial response for a median duration of 91 days, 19 (43%) dogs had stable disease for a median duration of 68 days, and 19 (43%) dogs developed progressive disease after a median duration of 21 days. Clinical benefit was more difficult to assess in the remaining 14 (24%) dogs that received vinorelbine as an adjuvant treatment. Overall median time to tumor progression was 103 days (range, 5 to 1,533 days). CONCLUSIONS AND CLINICAL RELEVANCE: Vinorelbine appeared to be effective in the treatment of several tumor types in dogs. Follow-up prospective studies of the clinical benefit of the drug in specific clinical scenarios will be necessary to support this conclusion.

6-Bromoindirubin-3'oxime (BIO) decreases proliferation and migration of canine melanoma cell lines.

Despite recent therapeutic advances, malignant melanoma is an aggressive tumor in dogs and is associated with a poor outcome. Novel, targeted agents are necessary to improve survival. In this study, 6-bromoindirubin-3'-oxime (BIO), a serine/threonine kinase inhibitor with reported specificity for glycogen synthase kinase-3 beta (GSK-3ß) inhibition, was evaluated in vitro in three canine melanoma cell lines (CML-10C2, UCDK9M2, and UCDK9M3) for ß-catenin-mediated transcriptional activity, Axin2 gene and protein expression levels, cell proliferation, chemotoxicity, migration and invasion assays. BIO treatment of canine malignant melanoma cell lines at 5 µM for 72 h enhanced ß-catenin-mediated transcriptional activity, suggesting GSK-3ß inhibition, and reduced cell proliferation and migration. There were no significant effects on invasion, chemotoxicity, or apoptosis. The results suggest that serine/threonine kinases may be viable therapeutic targets for the treatment of canine malignant melanoma.

c-Myc and transforming growth factor α enhance the development of hepatic lesions due to mutant ß-catenin in transgenic mice.

Alterations in the Wnt signaling pathway are associated with diverse cancers, including hepatocellular carcinoma (HCC). The development of HCC is thought to be a multistage process in which multiple genetic alterations are necessary. Few studies have assessed the effect of aberrant Wnt signaling activity in association with other molecular alterations in HCC. Here we sought to determine whether co-overexpression of c-Myc or TGFα, 2 signaling molecules known to contribute to HCC development, enhanced the development of hepatic lesions associated with a stabilized ß-catenin. The coexpression of mutant ß-catenin with either c-Myc or TGFα within hepatocytes increased the severity of hepatic lesions compared with that associated with any of the transgenes expressed individually. The coexpression of mutant ß-catenin with c-Myc or TGFα resulted in severe hepatomegaly necessitating the euthanasia of mice by an average of 156 and 128 d, respectively, after the cessation of doxycycline. The expression of mutant ß-catenin alone resulted in mild to moderate hepatomegaly that prompted the euthanasia of mice by an average of 75 d after the cessation of doxycycline. Collectively, these findings indicate that coexpression of c-Myc or TGFα delays the onset of endstage hepatic disease yet enhances the severity of hepatic lesions due to mutant ß-catenin.

Mutant Hras(G12V) and Kras(G12D) have overlapping, but non-identical effects on hepatocyte growth and transformation frequency in transgenic mice.

BACKGROUND: Mouse hepatocarcinogenesis is associated with mutations in Hras, but infrequently in Kras. The effect on carcinogenesis of developmental age at the time of ras mutation remains unknown. AIM: We sought to compare quantitatively the effects of expressing mutant H- or Kras genes in fetal vs. adult mouse liver. METHODS: We established an inducible system of gene expression in mouse liver to define disease pathogenesis associated with activation of oncogene expression. RESULTS: Diffuse expression of either oncogene in fetal or adult hepatocytes caused hepatomegaly. For mutant Hras(G12V), this phenotype was almost fully reversible and accompanied by apoptosis, indicating that maintenance of hepatomegaly requires continuous Hras(G12V) expression. We also examined the effect of ras expression on growth of transplanted hepatocytes in an in vivo system that allows us to quantify hepatocyte growth effects in both permissive and restrictive hepatic growth environments. Mutant Kras(G12D) had no effect on hepatocyte growth in this system. In contrast, Hras(G12V) induced increased hepatocyte focus growth in quiescent liver, the hallmark of a cell autonomous growth stimulus. Hras(G12V) also increased the fraction of donor hepatocyte foci that displayed extreme growth, a characteristic of preneoplastic lesions. CONCLUSIONS: The primary effect of diffuse, whole-liver expression of either mutant ras gene in fetal or adult mouse liver is diffuse and progressive hepatic growth. Hras(G12V) mutation influences hepatocarcinogenesis by conferring cell autonomous growth potential upon foci of expressing cells and by increasing the risk of neoplastic progression. Kras(G12D) does not share these latter carcinogenic effects in mouse liver.

Minimal cooperation between mutant Hras and c-myc or TGFα in the regulation of mouse hepatocyte growth or transformation in vivo.

BACKGROUND: Liver carcinogenesis is associated with multiple genetic changes in affected cells, including alterations in the Hras signalling pathway. AIM: To define the biological contributions of Hras to mouse hepatocarcinogenesis, we quantified in vivo interactions between mutant Hras and other genetic alterations frequently associated with liver cancer, including overexpression of the transcription factor c-myc and the epidermal growth factor receptor ligand transforming growth factor alpha (TGFα). METHODS: To accomplish this aim, we initiated expression of an activated Hras in hepatocytes of adult mice with or without simultaneous overexpression of either c-myc or TGFα. Potential interactions also were assessed through the use of the comparative hepatocyte growth assay, a hepatocyte transplantation assay that measures effects of altered gene expression on hepatocyte growth in vivo. RESULTS: Hras expression caused diffuse liver enlargement (hepatomegaly), and this phenotype was not changed by coexpression of c-myc or TGFα. Using the transplant system, we found that expression of mutant Hras alone was sufficient to induce hepatocyte focus growth in a quiescent liver. Paradoxically, adding expression of TGFα or c-myc reversed this Hras effect. Finally, the frequencies of transplant foci with the preneoplastic feature of extreme growth potential and of liver neoplasms were increased for Hras and both combinations when compared with control hepatocytes, but did not differ among oncogene-expressing groups. CONCLUSIONS: Hras-associated hepatocyte growth deregulation is not complemented by activation of c-myc or TGFα growth signalling pathways in mouse liver. This finding emphasizes the tissue-specific character of molecular growth regulation.

Wnt/ß-catenin expression does not correlate with serum alkaline phosphatase concentration in canine osteosarcoma patients.

Osteosarcoma is an aggressive malignancy of the bone and an increase in serum alkaline phosphatase concentration has clinical prognostic value in both humans and canines. Increased serum alkaline phosphatase concentration at the time of diagnosis has been associated with poorer outcomes for osteosarcoma patients. The biology underlying this negative prognostic factor is poorly understood. Given that activation of the Wnt signaling pathway has been associated with alkaline phosphatase expression in osteoblasts, we hypothesized that the Wnt/ß-catenin signaling pathway would be differentially activated in osteosarcoma tissue based on serum ALP status. Archived canine osteosarcoma samples and primary canine osteosarcoma cell lines were used to evaluate the status of Wnt/ß-catenin signaling pathway activity through immunohistochemical staining, western immunoblot analyses, quantitative reverse-transcription polymerase chain reaction, and a Wnt-responsive promoter activity assay. We found no significant difference in ß-catenin expression or activation between OSA populations differing in serum ALP concentration. Pathway activity was mildly increased in the primary OSA cell line generated from a patient with increased serum ALP compared to the normal serum ALP OSA cell line. Further investigation into the mechanisms underlying differences in serum ALP concentration is necessary to improve our understanding of the biological implications of this negative prognostic indicator.

Effect of mutant ß-catenin on liver growth homeostasis and hepatocarcinogenesis in transgenic mice.

BACKGROUND: Mutations in the Wnt signalling pathway molecule ß-catenin are associated with liver cancer. AIMS: Our aim was to confirm the effects of stabilized ß-catenin on liver growth, identify whether those effects were reversible and cell autonomous or non-cell autonomous and to model ß-catenin-induced liver cancer in mice. METHODS: Using a liver-specific inducible promoter, we generated transgenic mice in which the expression of mutant ß-catenin can be induced or repressed within hepatocytes in mice of different ages. RESULTS: Similar to other models, the hepatic expression of mutant ß-catenin in our model beginning in utero or induced in quiescent adult liver resulted in a two-fold liver enlargement and development of disease with a latency of 1-5 months, and mice displayed elevated blood ammonia and altered hepatic gene expression. Our model additionally allowed us to discover that molecular and phenotypic abnormalities were reversible following the inhibition of transgene expression. Hepatocyte transplant studies indicated that mutant ß-catenin could not increase the growth of transgene-expressing foci in either growth-permissive or -restrictive hepatic environments, but still directly altered hepatocyte gene expression. Mice with continuous but focal transgene expression developed hepatic neoplasms after the age of 1 year. CONCLUSIONS: Our findings indicate that hepatocyte gene expression is directly affected by mutant ß-catenin in a cell autonomous manner. However, hepatomegaly associated with diffuse hepatocyte-specific expression of mutant ß-catenin is secondary to liver functional alteration or non-cell autonomous. Both phenotypes are reversible. Nevertheless, some foci of transgene-expressing cells progressed to carcinoma, confirming the association of mutant ß-catenin with liver cancer.

Treatment of feline gastrointestinal small-cell lymphoma with chlorambucil and glucocorticoids.

Gastrointestinal (GI) lymphoma is the most frequently diagnosed form of lymphoma in the cat and is categorized into two distinct forms based on the size of neoplastic lymphocytes. Treatments for both large- and small-cell GI lymphoma have been described previously; however, multiple chemotherapy protocols were used, a minimal amount of histopathological characterization was provided, and, in most studies, the majority of diagnoses were obtained via endoscopic pinch biopsies. Twenty-eight cats (24 with full-thickness intestinal biopsies) were diagnosed with small-cell GI lymphoma and treated with a combination of chlorambucil and glucocorticoids. The majority of cases were strongly CD3+, and many displayed epitheliotropism. The overall clinical response rate was 96%, with a median clinical remission duration of 786 days. Follow-up identified seven cats with relapsed disease-all of which were treated with a rescue protocol of cyclophosphamide and glucocorticoids; the response rate was 100%, and four of the 28 cats were diagnosed with a second malignancy.