Frequent genetic defects in the p16/INK4A tumor suppressor in canine cell models of breast cancer and melanoma.

The cyclin-dependent kinase inhibitors (CKIs) belong to a group of key cell cycle proteins that regulate important cancer drug targets such as the cyclin/CDK complexes. Gene defects in the INK4A/B CKI tumor suppressor locus are frequently associated with human cancers and we have previously identified similar defects in canine models. Many of the cancer-associated genetic alterations, known to play roles in mammary tumor development and progression, appear similar in humans and dogs. The objectives of this study were to characterize expression defects in the INK4 genes, and the encoded p16 family proteins, in spontaneous canine primary mammary tumors (CMT) as well as in canine malignant melanoma (CML) cell lines to further develop these models of spontaneous cancers. Gene expression profiles and characterization of p16 protein were performed by rtPCR assay and immunoblotting followed by an analysis of relevant sequences with bioinformatics. The INK4 gene family were expressed differentially and the genes encoding the tumor suppressor p16, p14, and p15 proteins were often identified as defective in CMT and CML cell lines. The altered expression profiles for INK4 locus encoded tumor suppressor genes was also confirmed by the identification of similar gene defects in primary canine mammary tumor biopsy specimens which were also comparable to defects found in human breast cancer. These data strongly suggest that defects identified in the INK4 locus in canine cell lines are lesions originating in spontaneous canine cancers and are not the product of selection in culture. These findings further validate canine tumor models for use in developing a clear understanding of the gene defects present and may help identify new therapeutic cancer treatments that restore these tumor suppressor pathways based on precision medicine in canine cancers.

Circulating microRNA as biomarkers of canine mammary carcinoma in dogs.

BACKGROUND: Differentiating benign from canine malignant mammary tumors requires invasive surgical biopsy. Circulating microRNAs (miRNA) may represent promising minimally invasive cancer biomarkers in people and animals. OBJECTIVES: To evaluate the serum mRNA profile between dogs with and without mammary carcinoma, and to determine if any of these markers have prognostic significance. ANIMALS: Ten healthy client-owned female dogs (5 intact, 5 spayed) and 10 dogs with histologically confirmed mammary carcinoma were included; 9 were client-owned, whereas 1 was a research colony dog. METHODS: Retrospective study. Serum miRNA was evaluated by RNA deep-sequencing (RNAseq) and digital droplet PCR (dPCR).Expression of candidate biomarkers miR-18a, miR-19b, miR-29b, miR-34c, miR-122, miR-125a, and miR-181a was compared with clinical characteristics, including grade, metastasis, and survival. RESULTS: 452 unique serum miRNAs were detected by RNAseq. Sixty-five individual miRNAs were differentially expressed (>±1.5-fold) and statistically significant between groups. Serum miR-19b (P = .003) and miR-125a (P < .001) were significantly higher in the mammary carcinoma group by dPCR. Both had high accuracy based on receiver operator characteristic area under the curve (0.930 for miR-125a; 0.880 for miR-19b). Circulating miR-18a by RNAseq was significantly higher in mammary carcinoma dogs with histologic evidence of lymphatic invasion (P = 0.03). There was no significant association with any miRNA and survival or inflammatory status. CONCLUSIONS AND CLINICAL IMPORTANCE: Circulating miRNAs are differentially expressed in dogs with mammary carcinoma. Serum miR-19b and miR-18a represent candidate biomarkers for diagnosis and prognosis, respectively.

Autologous hybrid cell fusion vaccine in a spontaneous intermediate model of breast carcinoma.

Breast cancer is among the most common malignancies affecting women and reproductively intact female dogs, resulting in death from metastatic disease if not treated effectively. To better manage the disease progression, canine mammary tumor (CMT) cells derived from malignant canine mammary cancers were fused to autologous dendritic cells (DCs) to produce living hybrid-cell fusion vaccines for canine patients diagnosed with spontaneous mammary carcinoma. The high-speed sorting of rare autologous canine patient DCs from the peripheral blood provides the autologous component of fusion vaccines, and fusion to major histocompatibility complex-unmatched CMT cells were produced at high rates. The vaccinations were delivered to each patient following a surgical resection 3 times at 3-week intervals in combination with immuno-stimulatory oligonucleotides and Gemcitabine adjunct therapy. The immunized patient animals survived 3.3-times longer (median survival 611 days) than the control patients (median survival 184 days) and also appeared to exhibit an enhanced quality of life. A comparison of vaccinated patients diagnosed with inflammatory mammary carcinoma resulted in a very short median survival (42 days), suggesting no effect of vaccination. The data showed that the development of autologous living DC-based vaccine strategies in patient animals designed to improve the management of canine mammary carcinoma can be successful and may allow an identification of the antigens that can be translatable to promote effective immunity in canine and human patients.

Evaluation of 14-3-3 sigma as a potential partner of p16 in quiescence and differentiation.

p16 is an important tumor suppressor gene encoded by the INK4A/ARF/INK4B gene locus that is conserved in humans, rodents, and canids. p16 regulates cell cycle in early G1 phase inhibiting transition out of cell cycle from G1/S phase by regulating a multi-protein control complex. p16-associated proteins, cyclin D, CDK4, and CDK6, experience expression level decreases or do not change during cell differentiation and quiescence in contrast to constant p16 expression in post-proliferative cell phases. We hypothesized that p16 has alternate binding partners, other than classical proliferation-associated proteins such as CDKs, in these post-proliferative cell phases. Using co-immunoprecipitation, we have identified 14-3-3σ as a potential alternate binding partner for p16 in quiescent post-proliferative canine mammary cancer cells. Additionally, expression of 14-3-3σ was maintained as fibroblasts exit cell cycle and differentiate to adipocytes simultaneously with continued expression of p16. Based on these results, we suggest that 14-3-3σ protein may be an alternative binding partner for p16 active during cell quiescence and may associate with p16 during cell differentiation.

Malignant canine mammary epithelial cells shed exosomes containing differentially expressed microRNA that regulate oncogenic networks.

BACKGROUND: Breast (mammary) cancers in human (BC) and canine (CMT) patients share clinical, pathological, and molecular similarities that suggest dogs may be a useful translational model. Many cancers, including BC, shed exosomes that contain microRNAs (miRs) into the microenvironment and circulation, and these may represent biomarkers of metastasis and tumor phenotype. METHODS: Three normal canine mammary epithelial cell (CMEC) cultures and 5 CMT cell lines were grown in serum-free media. Exosomes were isolated from culture media by ultracentrifugation then profiled by transmission electron microscopy, dynamic light scattering, and Western blot. Exosomal small RNA was deep-sequenced on an Illumina HiSeq2500 sequencer and validated by qRT-PCR. In silico bioinformatic analysis was carried out to determine microRNA gene and pathway targets. RESULTS: CMEC and CMT cell lines shed round, "cup-shaped" exosomes approximately 150-200 nm, and were immunopositive for exosomal marker CD9. Deep-sequencing averaged ~ 15 million reads/sample. Three hundred thirty-eight unique miRs were detected, with 145 having > ±1.5-fold difference between one or more CMT and CMEC samples. Gene ontology analysis revealed that the upregulated miRs in this exosomal population regulate a number of relevant oncogenic networks. Several miRNAs including miR-18a, miR-19a and miR-181a were predicted in silico to target the canine estrogen receptor (ESR1α). CONCLUSIONS: CMEC and CMT cells shed exosomes in vitro that contain differentially expressed miRs. CMT exosomal RNA expresses a limited number of miRs that are up-regulated relative to CMEC, and these are predicted to target biologically relevant hormone receptors and oncogenic pathways. These results may inform future studies of circulating exosomes and the utility of miRs as biomarkers of breast cancer in women and dogs.

Estrogen receptor-α, progesterone receptor, and c-erbB/HER-family receptor mRNA detection and phenotype analysis in spontaneous canine models of breast cancer.

Well characterized, stable, p16-defective canine mammary cancer (CMT) cell lines and normal canine mammary epithelial cells were used to investigate expression of the major breast cancer-specific hormone receptors estrogen receptor alpha (ER1) and progesterone receptor (PR) as well as luminal epithelial-specific proto-oncogenes encoding c-erbB-1 (epidermal growth factor receptor/EGFr), c-erbB-2/HER2, c-erbB-3, and c-erbB-4 receptors. The investigation developed and validated quantitative reverse transcriptase polymerase chain reaction assays for each transcript to provide rapid assessment of breast cancer phenotypes for canine cancers, based on ER1, PR, and c-erbB-2/HER2 expressions, similar to those in human disease. Roles for relatively underexplored c-erbB-3 and c-erbB-4 receptor expressions in each of these breast cancer phenotypes were also evaluated. Each quantitative assay was validated by assessment of amplicon size and DNA sequencing following amplification. Differential expression of ER1, PR, and c-erbB-2 in CMT cell lines clearly defined distinct human-like breast cancer phenotypes for a selection of CMT-derived cell lines. Expression profiles for EGFr family genes c-erbB-3 and c-erbB-4 in CMT models also provided an enriched classification of canine breast cancer identifying new extended phenotypes beyond the conventional luminal-basal characterization used in human breast cancer.

Altered microRNA Expression Profiles and Regulation of INK4A/CDKN2A Tumor Suppressor Genes in Canine Breast Cancer Models.

microRNA (miRNA) expression profiling of cancer versus normal cells may reveal the characteristic regulatory features that can be correlated to altered gene expression in both human and animal models of cancers. In this study, the comprehensive expression profiles of the 277 highly characterized miRNAs from the canine genome were evaluated in spontaneous canine mammary tumor (CMT) models harboring defects in a group of cell cycle regulatory and potent tumor suppressor genes of INK4/CDKN2 family including p16/INK4A, p14ARF, and p15/INK4B. A large number of differentially expressed miRNAs were identified in three CMT cell lines to potentially target oncogenes, tumor suppressor genes and cancer biomarkers. A group of the altered miRNAs were identified by miRNA target prediction tools for regulation of the INK4/CDKN2 family tumor suppressor genes. miRNA-141 was experimentally validated for INK4A 3'-UTR target binding in the CMT cell lines providing an essential mechanism for the post-transcriptional regulation of the INK4A tumor suppressor gene in CMT models. A well-recognized group of miRNAs including miR-21, miR-155, miR-9, miR-34a, miR-143/145, and miR-31 were found to be altered in both CMTs and human breast cancer. These altered miRNAs might serve as potential targets for advancing the development of future therapeutic reagents. These findings further strengthen the validity and use of canine breast cancers as appropriate models for the study of human breast cancers.

Engraftment of canine peripheral blood lymphocytes into nonobese diabetic-severe combined immune deficient IL-2R common gamma chain null mice.

To study the canine immune system we generated a mouse model engrafted with canine lymphocytes using NOD SCID IL2R common gamma chain -/- (NSG) mice as recipients (Ca-PBL-SCID). Engraftment of canine peripheral blood lymphocytes (PBLs) was determined post-injection with 10(7) peripheral blood mononuclear cells (PBMCs) into irradiated NSG mice using flow cytometry and fluorescently labeled antibodies specific to canine helper T cells (CD45(+) CD4(+)), cytotoxic lymphocytes (CD45(+) CD8(+)), regulatory T cells (CD45(+) CD4(+) Foxp3(+)), and B cells (CD45(+) Ig(+) CD21lo). Canine CD45(+) lymphocytes were detectable as early as day 1 in the peritoneal cavity, and beginning at 9 days in the blood, bone marrow, and spleen. CD4(+) T cells, of which Foxp-3(+) CD25hi cells constituted a minor percentage, were the predominant lymphocyte population at 9 days post engraftment contrasting with increasing proportions of CD8(+) CTL's and Ig(+) B cells beginning at 16 days. Canine immunoglobulin was initially detected in the serum of Ca-PBL-SCID mice at 9 days post-engraftment and peaked in concentration at day 36. From day 28 to 52 post-engraftment 30% of the Ca-PBL-SCID mice became markedly anemic and thrombocytopenic, yet gross and histopathologic examination of bone marrow, kidneys, spleen, liver, and intestine revealed no obvious lesions. Blood smear evaluation revealed agglutination of mature red blood cells, reticulocytes and a regenerative anemia. These findings demonstrate that NSG mice are capable of engraftment of canine PBLs yet develop graft versus host disease similar to Hu-PBL-SCID mice.

Novel frameshift mutation in the p16/INK4A tumor suppressor gene in canine breast cancer alters expression from the p16/INK4A/p14ARF locus.

The INK4 family of cyclin-dependent kinase inhibitors (CKI) encode important cell cycle regulators that tightly control cell cycle during G1 to S phase. These related genes are considered tumor suppressors as loss of function contributes to the malignant phenotype. Expression of CKIs p16, p14ARF, or p15 were defective in six different canine mammary tumor (CMT) cell lines compared to normal thoracic canine fibroblasts. This suggests CKI defects are frequently responsible for neoplastic transformation in canine mammary carcinomas. p16 and p14ARF are two alternatively spliced products derived from the canine p16/INK4A/p14ARF gene locus. Despite omissions in the published p16 transcript and canine genome and the presence of GC-rich repeats, we determined the complete coding sequence of canine p16 revealing a deletion and frameshift mutation in p16 exon 1α in CMT28 cells. In addition, we determined canine p14ARF mRNA and protein sequences. Mapping of these mutations uncovered important aspects of p16 and p14ARF expression and defects in CMT28 cells shifting the p16 reading frame into p14ARF making a fusion protein that was predicted to be truncated, unstable and devoid of structural and functional integrity. This data describes an important neoplastic mechanism in the p16/INK4A/p14ARF locus in a spontaneous canine model of breast cancer.

Tumor suppressor gene p16/INK4A/CDKN2A-dependent regulation into and out of the cell cycle in a spontaneous canine model of breast cancer.

p16/INK4A/CDKN2A is an important tumor suppressor gene that arrests cell cycle in G1 phase inhibiting binding of CDK4/6 with cyclin D1, leaving the Rb tumor suppressor protein unphosphorylated and E2F bound and inactive. We hypothesized that p16 has a role in exit from cell cycle that becomes defective in cancer cells. Well characterized p16-defective canine mammary cancer cell lines (CMT28, CMT27, and CMT12), derived stably p16-transfected CMT cell clones (CMT27A, CMT27H, CMT28A, and CMT28F), and normal canine fibroblasts (NCF), were used to investigate expression of p16 after serum starvation into quiescence followed by re-feeding to induce cell cycle re-entry. The parental CMT cell lines used lack p16 expression either at the mRNA or protein expression levels, while p27 and other p16-associated proteins, including CDK4, CDK6, cyclin D1, and Rb, were expressed. We have successfully demonstrated cell cycle arrest and relatively synchronous cell cycle re-entry in parental CMT12, CMT28 and NCF cells as well as p16 transfected CMT27A, CMT27H, CMT28A, and CMT28F cells and confirmed this by (3)H-thymidine incorporation and flow cytometric analysis of cell cycle phase distribution. p16-transfected CMT27A and CMT27H cells exited cell cycle post-serum-starvation in contrast to parental CMT27 cells. NCF, CMT27A, and CMT28F cells expressed upregulated levels of p27 and p16 mRNA, post-serum starvation, as cells exited cell cycle and entered quiescence. Because quiescence and differentiation are associated with increased levels of p27, our data demonstrating that p16 was upregulated along with p27 during quiescence, suggests a potential role for p16 in maintaining these non-proliferative states.

Landscape phages and their fusion proteins targeted to breast cancer cells.

Breast cancer is a leading cause of death among women in the USA. The efficacy of existing anticancer therapeutics can be improved by targeting them through conjugation with ligands binding to cellular receptors. Recently, we developed a novel drug targeting strategy based on the use of pre-selected cancer-specific 'fusion pVIII proteins' (fpVIII), as targeting ligands. To study the efficiency of this approach in animal models, we developed a panel of breast cancer cell-binding phages as a source of targeted fpVIIIs. Two landscape phage peptide libraries (8-mer f8/8 and 9-mer f8/9) were screened to isolate 132 phage variants that recognize breast carcinoma cells MCF-7 and ZR-75-1 and internalize into the cells. When tested for their interaction with the breast cancer cells in comparison with liver cancer cells HepG2, human mammary cells MCF-10A cells and serum, 16 of the phage probes selectively interacted with the breast cancer cells whereas 32 bound both breast and liver cancer cells. The most prominent cancer-specific phage DMPGTVLP, demonstrating sub-nanomolar Kd in interaction with target cells, was used for affinity chromatography of cellular membrane molecules to reveal its potential binding receptor. The isolated protein was identified by direct sequencing as cellular surface nucleolin. This conclusion was confirmed by inhibition of the phage-cell interaction with nucleolin antibodies. Other prominent phage binders VPTDTDYS, VEEGGYIAA, and DWRGDSMDS demonstrate consensus motifs common to previously identified cancer-specific peptides. Isolated phage proteins exhibit inherent binding specificity towards cancer cells, demonstrating the functional activity of the selected fused peptides. The selected phages, their peptide inserts and intact fusion proteins can serve as promising ligands for the development of targeted nanomedicines and their study in model mice with xenograft of human cells MCF-7 and ZR-75-1.

Delivery of siRNA into breast cancer cells via phage fusion protein-targeted liposomes.

Efficacy of siRNAs as potential anticancer therapeutics can be increased by their targeted delivery into cancer cells via tumor-specific ligands. Phage display offers a unique approach to identify highly specific and selective ligands that can deliver nanocarriers to the site of disease. In this study, we proved a novel approach for intracellular delivery of siRNAs into breast cancer cells through their encapsulation into liposomes targeted to the tumor cells with preselected intact phage proteins. The targeted siRNA liposomes were obtained by a fusion of two parental liposomes containing spontaneously inserted siRNA and fusion phage proteins. The presence of pVIII coat protein fused to a MCF-7 cell-targeting peptide DMPGTVLP in the liposomes was confirmed by Western blotting. The novel phage-targeted siRNA-nanopharmaceuticals demonstrate significant down-regulation of PRDM14 gene expression and PRDM14 protein synthesis in the target MCF-7 cells. This approach offers the potential for development of new anticancer siRNA-based targeted nanomedicines. FROM THE CLINICAL EDITOR: In this study, the authors report a novel approach for targeted intracellular delivery of siRNAs into breast cancer cells through encapsulation into liposomes targeted to the tumor cells with preselected intact phage proteins.

An autologous dendritic cell canine mammary tumor hybrid-cell fusion vaccine.

Mammary cancer is among the most prevalent canine tumors and frequently resulting in death due to metastatic disease that is highly homologous to human breast cancer. Most canine tumors fail to raise effective immune reactions yet, some spontaneous remissions do occur. Hybrid canine dendritic cell-tumor cell fusion vaccines were designed to enhance antigen presentation and tumor immune recognition. Peripheral blood-derived autologous dendritic cell enriched populations were isolated from dogs based on CD11c(+) expression and fused with canine mammary tumor (CMT) cells for vaccination of laboratory Beagles. These hybrid cells were injected into popliteal lymph nodes of normal dogs, guided by ultrasound, and included CpG-oligonucleotide adjuvants. Three rounds of vaccination were delivered. Significant IgG responses were observed in all vaccinated dogs compared to vehicle-injected controls. Canine IgG antibodies recognized shared CMT antigens as was demonstrated by IgG-recognition of three unrelated/independently derived CMT cell lines, and recognition of freshly isolated, unrelated, primary biopsy-derived CMT cells. A bias toward an IgG2 isotype response was observed after two vaccinations in most dogs. Neither significant cytotoxic T cell responses were detected, nor adverse or side-effects due to vaccination or due to the induced immune responses noted. These data provide proof-of-principle for this cancer vaccine strategy and demonstrate the presence of shared CMT antigens that promote immune recognition of mammary cancer.

Landscape phage fusion protein-mediated targeting of nanomedicines enhances their prostate tumor cell association and cytotoxic efficiency.

Tumor-specific cytotoxicity of drugs can be enhanced by targeting them to tumor receptors using tumor-specific ligands. Phage display offers a high-throughput approach to screen for the targeting ligands. We have successfully isolated phage fusion peptides selective and specific for PC3 prostate cancer cells. Also, we have demonstrated a novel approach of targeting liposomes through tumor-specific phage fusion coat proteins, exploiting the intrinsic properties of the phage coat protein as an integral membrane protein. Here we describe the production of Rhodamine-labeled liposomes as well as doxorubicin-loaded long-circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides, as an extension of our previous studies. Targeting of labeled liposomes was demonstrated using fluorescence microscopy as well as flow cytometry. Targeting of doxorubicin-loaded liposomes enhanced their cytotoxic effect against PC3 cells in vitro, indicating a possible therapeutic advantage. The simplicity of the approach for generating targeted liposomes coupled with the ability to rapidly obtain tumor-specific phage fusion proteins via phage display may contribute to a combinatorial system for the production of targeted liposomal therapeutics for advanced stages of prostate tumor. From the clinical editor: This paper demonstrates targeting cytotoxic agents to tumor receptors using tumor-specific ligands. The authors describe the production of Rhodamine-labeled liposomes as well as doxorubicin loaded long circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides. This approach may be especially relevant for advanced prostate tumors.

Phenotype-rescue of cyclin-dependent kinase inhibitor p16/INK4A defects in a spontaneous canine cell model of breast cancer.

Mammary cancer is among the most frequently observed canine tumors in unspayed female dogs resulting in death due to metastatic disease. These tumors are excellent models of human breast cancer but until recently there was only anecdotal evidence regarding underlying genetic defects. We recently reported expression defects in the cyclin-dependent kinase p21/Cip1 and p53 among three independent canine mammary tumor (CMT) cell lines derived from spontaneous canine mammary cancers. We investigated further defects in the same three cell lines focusing on additional tumor suppressor gene defects in cyclin-dependent kinase inhibitors. p27/KIP1 appeared normally expressed and did not appear to encode inactivating mutations. In contrast, expression of p16/INK4A was defective/absent in two cell lines and normal/slightly induced in the third cell line. To determine if defects were causative in maintaining the transformed phenotype, a p16/INK4A transgene was permanently transfected followed by selection and single cell cloning. CMT/p16 clones were characterized for transgene expression, p16 protein content and phenotype including proliferation rate, cell cycle phase distribution, contact inhibition, substrate dependent cell growth and cell morphology. All cell lines appeared unique yet clear indications of phenotype rescue due to p16/INK4A transgene complementation were observed suggesting that defects in p16 expression were present in all three. In some cases cellular senescence also appeared to be induced. These data provide evidence supporting p16/INK4A mutations as causative defects promoting transformation in canine mammary cancer and further characterizes tumor suppressor gene defects with functional consequences in these cells supporting their application as spontaneous animal models of human disease.

An allogeneic hybrid-cell fusion vaccine against canine mammary cancer.

Mammary cancer is among the most prevalent of canine tumors frequently resulting in death due to metastatic disease. Most tumors fail to raise an effective immune reaction making improving immune recognition a priority. Hybrid-cell fusion strategies have been employed to load dendritic cell populations with tumor cell antigens to stimulate immune recognition; however, recovery, heterogeneity and quality of primary cells from patients present enormous challenges. We employed allogeneic cell lines to develop an improved hybrid-cell fusion strategy and evaluated immune reactions in normal laboratory beagles. Such a strategy relies on enhanced immune recognition of allogeneic tumor cell antigens by antigen presenting cells. Optimized PEG-promoted fusions between uniquely stained canine mammary tumor CMT12 or CMT28 cells and a dendritic cell-like DH82 cell fusion partner resulted in greater than 40% hybrid-cell fusion populations by flow cytometry and fluorescence microscopy. Hybrid-cell fusions were delivered by direct ultrasound guided injection into popliteal lymph nodes of laboratory beagles. Only hybrid-cell fusions provided statistically significant enhancement of cell-mediated immunity ((51)Cr-release assay) compared to innate reactions in naïve vehicle injected dogs while dogs vaccinated with either single cell component alone did not. Vaccination with hybrid-cell fusions enhanced IFN-gamma expression in sorted CD8+ and CD4+ cells but not in CD4-/CD8- cells consistent with a CTL response. Cell-mediated immune assays revealed strong reactions against matched (vaccine component) CMT cells and unmatched CMT cells indicative of an immune response to mammary cancer antigens common to both cell lines. These results provide proof of principle for development of an allogeneic vaccination strategy against canine mammary cancer.

Experimental infection of cats (Felis catus) with Tritrichomonas foetus isolated from cattle.

Tritrichomonas foetus is recognized as the causative agent of venereal trichomoniasis in cattle. It is characterized by embryonic and early fetal death and post-coital pyometra, and feline trichomoniasis, manifest as chronic, large bowel diarrhea. Many of the infected cats are less than 2 years old and specific routes of transmission remain unknown. We recently demonstrated that feline isolates of T. foetus can successfully infect heifers, resulting in pathologic changes similar, but not identical to those previously reported as representative of bovine trichomoniasis. In this study, we experimentally infected six cats less than 1 year of age with a bovine (D-1) isolate of T. foetus and one cat with a feline (AUTf-1) isolate of T. foetus. Within 2 weeks, the cat infected with the feline (AUTf-1) isolate was culture positive for trichomonads in weekly fecal samples. At the end of 5 weeks, only one cat infected with the bovine (D-1) isolate was fecal culture positive for trichomonads. At necropsy, the intestine of each cat was removed and divided into five sections (ileum, cecum, anterior, medial and posterior colon). Contents from each section were collected and cultured. The cat infected with the feline (AUTf-1) isolate was culture positive in the ileum, cecum, medial and posterior colon. Two cats infected with the bovine (D-1) isolate were culture positive in the cecum only. Additionally, each intestinal section was submitted to a pathologist for histopathological examination. The combined results indicate that there are demonstrable differences between the feline (AUTf-1) and bovine (D-1) isolates regarding their infectivity in cats.

Alterations in CDK1 expression and nuclear/nucleolar localization following induction in a spontaneous canine mammary cancer model.

Transcription of CDK1 is induced as cells re-enter the cell cycle from quiescence and these early cell cycle re-entry events have been modeled by okadaic acid treatment due to its activity on specific enhancer sequences in the human CDK1 promoter. To investigate heterogeneity of control of this mechanism in the context of neoplastic transformation, a cellular model derived from spontaneous canine mammary cancer (CMT) was developed that includes six cell lines derived from different animals. Notable heterogeneity in response to okadaic acid was observed in expression of CDK1 mRNA and protein. In response to okadaic acid treatment, two CMT cell lines exhibited a CDK1 mRNA induction while one cell line exhibited CDK1 mRNA suppression, and three remained unchanged. Despite this variability, three CMT cell lines arrested in S or G2/M phase and five exhibited marked increases in apoptosis. Moderation of some of these differences were observed at the level of CDK1 protein as three of six CMT cell lines exhibited only moderate enhancement in CDK1 protein levels while three remained essentially unchanged. Some additional differences in distribution of CDK1 protein, favoring enhanced nuclear over cytoplasmic CDK1 localization, were observed in treated cells in the form of concentrated nuclear CDK1 labeled foci. Confocal microscopy revealed the presence of brightly labeled punctate foci containing CDK1 protein within nuclei as well as nucleoli in okadaic acid treated non-mitotic cells suggesting a role for this kinase outside the normal G2/mitotic phase of the cell cycle and suggesting a possible new function within the nucleolus.

Cytokine gene expression in response to SnSAG1 in horses with equine protozoal myeloencephalitis.

Equine protozoal myeloencephalitis (EPM) is a neurologic syndrome seen in horses from the Americas and is mainly caused by Sarcocystis neurona. Recently, a 29-kDa surface antigen from S. neurona merozoites was identified as being highly immunodominant on a Western blot. This antigen has been sequenced and cloned, and the expressed protein has been named SnSAG1. In a previous study, cell-mediated immune responses to SnSAG1 were shown to be statistically significantly reduced in horses with EPM in comparison to EPM-negative control horses. It therefore appears as though the parasite is able to induce immunosuppression towards parasite-derived antigens as parasite-specific responses are decreased. Isolated peripheral blood lymphocytes from 21 EPM (cerebrospinal fluid [CSF] Western blot)-negative horses with no clinical signs and 21 horses with clinical signs of EPM (CSF Western blot positive) were cocultured with SnSAG1 for 48 and 72 h, and the effect on cytokine production was investigated by means of reverse transcriptase PCR. Cytokines assayed include gamma interferon (IFN-gamma), tumor necrosis factor alpha, interleukin (IL)-2, IL-4, and IL-6. beta-Actin was used as the housekeeping gene. A Wilcoxon signed-rank test of the findings indicated that there was a statistically significant decrease in IFN-gamma production after 48 h in culture for samples from horses with clinical disease. There was also a statistically significant increase in IL-4 production after 72 h in culture for samples from horses with EPM. These results further support the notion that this parasite is able to subvert the immune system in horses with clinical disease.

Characterization of the CDP-like/CTAS-1 binding site in the okadaic acid response element (OARE) of the human CDK1(p34cdc2) promoter.

BACKGROUND: Transcription of CDK1 is induced at the G0/G1-phase of the cell cycle and after okadaic acid treatment and we identified the Site I okadaic acid response element (OARE -944 to -763nt) enhancer in the human CDK1 promoter. MATERIALS AND METHODS: The OARE region of the CDK1 promoter was characterized for enhancer/repressor activities. RESULTS: Transient transfection of upper and lower Site I subregions suggested enhanced transcription activity was divided between both while mobility shift assays demonstrated sequence-specific protein binding to Site IA. Site IA also formed shift complexes following serum starvation/refeeding and putative transcription factor binding sites clustered in Site IA. Oligonucleotides encoding a consensus CDP transcription factor binding site effectively competed against authentic Site IA in mobility shift assays. Mutation of the CDP-like binding sequence substantially reduced competition. DNaseI footprinting revealed binding at this site. CONCLUSION: The CDP-like recognition sequence appears to comprise the OARE binding authentic CDP and/or related factors. We termed this site the CDK1 transcription activation sequence-1 (CTAS-1) enhancer of the human CDK1 promoter.