Degenerative Myelopathy and Neuropathy in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) Mice Caused by Lactate Dehydrogenase-Elevating Virus (LDV).

Following implantation of patient-derived xenograft (PDX) breast carcinomas from three separate individuals, 33/51 female NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice presented with progressive, unilateral to bilateral, ascending hindlimb paresis to paralysis. Mice were mildly dehydrated, in thin to poor body condition, with reduced to absent hindlimb withdrawal reflex and deep pain sensation. Microscopically, there was variable axonal swelling, vacuolation, and dilation of myelin sheaths within the ventral spinal cord and spinal nerve roots of the thoracolumbar and sacral spinal cord, as well as within corresponding sciatic nerves. Results of PCR screening of PDX samples obtained at necropsy and pooled environmental swabs from the racks housing affected animals were positive for lactate dehydrogenase-elevating virus (LDV). LDV is transmitted through animal-animal contact or commonly as a contaminant of biologic materials of mouse origin. Infection is associated with progressive degenerative myelopathy and neuropathy in strains of mice harboring endogenous retrovirus (AKR, C58), or in immunosuppressed strains (NOD-SCID, Foxn1nu), and can interfere with normal immune responses and alter engraftment and growth of xenograft tumors in immunosuppressed mice. This is the first reported series of LDV-induced poliomyelitis in NSG mice and should be recognized as a potentially significant confounder to biomedical studies utilizing immunodeficient xenograft models.

F344/NTac Rats Chronically Exposed to Bromodichloroacetic Acid Develop Mammary Adenocarcinomas With Mixed Luminal/Basal Phenotype and Tgfß Dysregulation.

Breast cancer is the most common cancer and the second-leading cause of cancer mortality in women in the United States. A recent 2-year National Toxicology Program carcinogenicity study showed an increased incidence of proliferative mammary lesions (hyperplasia, fibroadenoma, adenocarcinoma) in F344/NTac rats exposed to bromodichloroacetic acid (BDCA), a disinfection by-product in finished drinking water with widespread human exposure. We hypothesized that the increase in mammary tumors observed in BDCA-exposed F344/NTac rats may be due to underlying molecular changes relevant for human breast cancer. The objective of the study was to compare (1) gene and protein expression and (2) mutation spectra of relevant human breast cancer genes between normal untreated mammary gland and mammary tumors from control and BDCA-exposed animals to identify molecular changes relevant for human cancer. Histologically, adenocarcinomas from control and BDCA-exposed animals were morphologically very similar, were estrogen/progesterone receptor positive, and displayed a mixed luminal/basal phenotype. Gene expression analysis showed a positive trend in the number of genes associated with human breast cancer, with proportionally more genes represented in the BDCA-treated tumor group. Additionally, a 5-gene signature representing possible Tgfß pathway activation in BDCA-treated adenocarcinomas was observed, suggesting that this pathway may be involved in the increased incidence of mammary tumors in BDCA-exposed animals.

Inhibition of transforming growth factor-ß-activated kinase-1 blocks cancer cell adhesion, invasion, and metastasis.

BACKGROUND: Tumour cell metastasis involves cell adhesion and invasion, processes that depend on signal transduction, which can be influenced by the tumour microenvironment. N-6 polyunsaturated fatty acids, found both in the diet and in response to inflammatory responses, are important components of this microenvironment. METHODS: We used short hairpin RNA (shRNA) knockdown of TGF-ß-activated kinase-1 (TAK1) in human tumour cells to examine its involvement in fatty acid-stimulated cell adhesion and invasion in vitro. An in vivo model of metastasis was developed in which cells, stably expressing firefly luciferase and either a control shRNA or a TAK1-specific shRNA, were injected into the mammary fat pads of mice fed diets, rich in n-6 polyunsaturated fatty acids. Tumour growth and spontaneous metastasis were monitored with in vivo and in situ imaging of bioluminescence. RESULTS: Arachidonic acid activated TAK1 and downstream kinases in MDA-MB-435 breast cancer cells and led to increased adhesion and invasion. Knockdown of TAK1 blocked this activation and inhibited both cell adhesion and invasion in vitro. Tumour growth at the site of injection was not affected by TAK1 knockdown, but both the incidence and extent of metastasis to the lung were significantly reduced in mice injected with TAK1 knockdown cells compared with mice carrying control tumour cells. CONCLUSION: These data demonstrate the importance of TAK1 signalling in tumour metastasis in vivo and suggest an opportunity for antimetastatic therapies.

Pathologic progression of mammary carcinomas in a C3(1)/SV40 T/t-antigen transgenic rat model of human triple-negative and Her2-positive breast cancer.

The C3(1) component of the rat prostate steroid binding protein has been used to target expression of the SV40 T/t-antigen to the mammary epithelium of mice resulting in pre-neoplastic lesions that progress to invasive and metastatic cancer with molecular features of human basal-type breast cancer. However, there are major differences in the histologic architecture of the stromal and epithelial elements between the mouse and human mammary glands. The rat mammary gland is more enriched with epithelial and stromal components than the mouse and more closely resembles the cellular composition of the human gland. Additionally, existing rat models of mammary cancer are typically estrogen receptor positive and hormone responsive, unlike most genetically engineered mouse mammary cancer models. In an attempt to develop a mammary cancer model that might more closely resemble the pathology of human breast cancer, we generated a novel C3(1)/SV40 T/t-antigen transgenic rat model that developed progressive mammary lesions leading to highly invasive adenocarcinomas. However, aggressive tumor development prevented the establishment of transgenic lines. Characterization of the tumors revealed that they were primarily estrogen receptor and progesterone receptor negative, and either her2/neu positive or negative, resembling human triple-negative or Her2 positive breast cancer. Tumors expressed the basal marker K14, as well as the luminal marker K18, and were negative for smooth muscle actin. The triple negative phenotype has not been previously reported in a rat mammary cancer model. Further development of a C3(1)SV40 T/t-antigen based model could establish valuable transgenic rat lines that develop basal-type mammary tumors.

BMI1 cooperates with H-RAS to induce an aggressive breast cancer phenotype with brain metastases.

B-lymphoma Moloney murine leukaemia virus insertion region-1 (BMI1) is a member of the polycomb group of transcription repressors, which functions in stem cell maintenance and oncogenesis through the inhibition of the INK4A/ARF tumour suppressor locus. Overexpression of BMI1 is associated with poor prognosis in several human cancers, including breast cancer. We have previously shown that BMI1 collaborates with H-RAS to induce transformation of MCF10A human mammary epithelial cells through dysregulation of multiple growth pathways independent of the INK4A/ARF locus. In this study, we show that BMI1 collaborates with H-RAS to promote increased proliferation, invasion and resistance to apoptosis in vitro, and an increased rate of spontaneous metastases from mammary fat pad xenografts including novel metastases to the brain. Furthermore, in collaboration with H-RAS, BMI1 induced fulminant metastatic disease in the lung using a tail vein model of haematogenous spread through accelerated cellular proliferation and inhibition of apoptosis. Finally, we show that knockdown of BMI1 in several established breast cancer cell lines leads to decreased oncogenic behaviour in vitro and in vivo. In summary, BMI1 collaborates with H-RAS to induce an aggressive and metastatic phenotype with the unusual occurrence of brain metastasis, making it an important target for diagnosis and treatment of aggressive breast cancer.

Choroid plexus papilloma in a Scottish highland cow.

Choroid plexus papilloma, a rare tumour in bovids, arising from the roof of the third ventricle was diagnosed at necropsy in a 4-year-old Scottish Highland cow. The animal presented with a 2-month history of progressive ataxia, ventromedial strabismus, and hyperaesthesia. Neoplastic epithelial cells were positive immunohistochemically for pancytokeratin and S-100, and negative for GFAP. Ultrastructurally, epithelial cells were characterized by intercellular junctions, zonulae adherens, and zonulae occludens. Neither cilia nor basal bodies were identified. The gross, microscopical, immunohistochemical and ultrastructural findings were consistent with those of a choroid plexus papilloma.

Eosinophilic crystalline pneumonia as a major cause of death in 129S4/SvJae mice.

Eosinophilic crystalline pneumonia is an idiopathic disease that occurs in many strains and stocks of mice, more commonly in strains on a C57BL/6 background. The disease occurs sporadically in most strains of mice and varies from mild and subclinical to severe and fulminating, sometimes resulting in respiratory distress and death. In this study, 94 aged male and female 129S4/SvJae mice were evaluated for eosinophilic crystalline pneumonia lesions. There was an 87% incidence, with females overrepresented. Histologically, there were multifocal to coalescing inflammatory infiltrates composed of numerous large eosinophilic macrophages and multinucleate cells admixed with eosinophils, neutrophils, lymphocytes, and plasma cells within alveolar and bronchiolar spaces, associated with refractile, brightly eosinophilic, angular crystals. Alveolar macrophages and multinucleate cells contained fine needlelike to rectangular intracytoplasmic crystalline material. Similar crystals were often free within alveoli and conducting airways, often associated with mucous metaplasia of bronchiolar epithelium. This disease may occur spontaneously or in concert with other pulmonary lesions, such as pulmonary adenomas, lymphoproliferative disease, allergic pulmonary disease, and parasitic or fungal infections. The characteristic crystals morphologically resemble Charcot-Leyden crystals, which represent eosinophil breakdown products in humans with eosinophil-related disease. However, crystals in eosinophilic crystalline pneumonia are composed predominantly of Ym1 protein, a chitinase-like protein associated with neutrophil granule products and secreted by activated macrophages. The function of Ym1 protein is not fully understood but is believed to be involved in host immune defense, eosinophil recruitment, and cell-cell and cell-matrix interactions consistent with tissue repair. The mechanism of induction of eosinophilic crystalline pneumonia with Ym1 crystal formation is unknown.

Fatal herpesvirus encephalitis in a reticulated giraffe (Giraffa camelopardalis reticulata).

Fatal meningoencephalitis caused by equine herpesvirus-1 (EHV-1) was diagnosed in a reticulated giraffe (Giraffa camelopardalis reticulate). The giraffe died following a history of stumbling, incoordination, and abdominal pain. Gross examination of the brain revealed asymmetric edema and red-brown discoloration, predominantly within the telencephalon. Microscopically, there was perivascular lymphohistiocytic cuffing, multifocal gliosis, and neuronal necrosis in the cerebrum. Necrotic neurons contained acidophilic intranuclear inclusions. EHV-1 was isolated from the brain of the giraffe, and polymerase chain reaction was positive on sections of the brain. Immunohistochemistry using an EHV-1-specific antibody identified positive staining in neurons, astrocytes, and endothelial cells. The giraffe had been housed with a group of zebras that were serologically positive for EHV-1 and suspected as the source of infection. This raises concerns for cross-species transmission of EHV-1 when housing equids together with other species in zoologic collections.

Multipotential osteosarcoma with various mesenchymal differentiations in a young dog.

Apparently synchronous, aggressive, mixed mesenchymal tumors in the right tibia, right femur, left femur, and rib cage produced multiple microscopic metastases in the lungs and macroscopic metastases in the liver, kidney, and spleen in a 1.5-year-old, neutered male, mixed-breed dog. No primary soft tissue tumor mass was present. Microscopically, the neoplasm exhibited osteosarcomatous, chondrosarcomatous, liposarcomatous, leiomyosarcomatous, fibrosarcomatous, angiosarcomatous, and leukocytic differentiation and was diagnosed as a multipotential osteosarcoma with various mesenchymal differentiation. Immunohistochemically, the neoplasm was cytoplasmically immunoreactive for vimentin, osteonectin, osteocalcin, CD 18, CD 31, desmin, and muscle-specific actin. Oil Red O staining was positive within liposarcomatous areas. Skeletal metastases from a primary bone tumor are exceedingly rare in human and veterinary medicine. However, the history, clinical signs, location, microscopic and immunohistochemical features were similar to those described in aggressive, poorly differentiated osteosarcomas of children. In addition, the wide range of mesenchymal tissue differentiation of this neoplasm was unusual, and to the authors' knowledge, an osteosarcoma with this degree of multiple differentiation has not been previously reported in the dog.