Prion diseases are transmissible neurodegenerative disorders of humans and animals for which no effective treatment is available. Conformationally altered, protease-resistant forms of the prion protein (PrP) termed PrP ^Sc are critical for disease transmissibility and pathogenesis, thus representing a primary target for therapeutic strategies. Based on previous findings that tetracyclines revert abnormal physicochemical properties and abolish neurotoxicity of PrP peptides in vitro , we tested the ability of these compounds to interact with PrP ^Sc from patients with the new variant of Creutzfeldt–Jakob disease (vCJD) and cattle with bovine spongiform encephalopathy (BSE). The incubation with tetracycline hydrochloride or doxycycline hyclate at concentrations ranging from 10 μM to 1 mM resulted in a dose-dependent decrease in protease resistance of PrP ^Sc . This finding prompted us to investigate whether tetracyclines affect prion infectivity by using an animal model of disease. Syrian hamsters were injected intracerebrally with 263K scrapie-infected brain homogenate that was coincubated with 1 mM tetracycline hydrochloride, 1 mM doxycycline hyclate, or vehicle solution before inoculation. Hamsters injected with tetracycline-treated inoculum showed a significant delay in the onset of clinical signs of disease and prolonged survival time. These effects were paralleled by a delay in the appearance of magnetic-resonance abnormalities in the thalamus, neuropathological changes, and PrP ^Sc accumulation. When tetracycline was preincubated with highly diluted scrapie-infected inoculum, one third of hamsters did not develop disease. Our data suggest that these well characterized antibiotics reduce prion infectivity through a direct interaction with PrP ^Sc and are potentially useful for inactivation of BSE- or vCJD-contaminated products and prevention strategies.

Objective—To compare the Kiupel (2 categories) and Patnaik (3 categories) histologic grading systems for predicting the presence of metastasis at the time of initial examination in dogs with cutaneous mast cell tumors (MCTs). Design—Retrospective case series. Animals—386 client-owned dogs with cutaneous MCTs. Procedures—Medical records of dogs with newly diagnosed, histologically confirmed cutaneous MCTs that had undergone complete clinical staging were reviewed for clinical and histopathologic data. Results—All Patnaik grade 1 MCTs (n = 52) were classified as Kiupel low-grade MCTs, and all Patnaik grade 3 MCTs (43) were classified as Kiupel high-grade MCTs. Of the 291 Patnaik grade 2 MCTs, 243 (83.5%) were classified as Kiupel low-grade tumors, and 48 (16.5%) were classified as Kiupel high-grade MCTs. Dogs with Patnaik grade 3 MCTs were significantly more likely to have metastases at the time of initial examination than were dogs with grade 1 or 2 MCTs (OR, 5.46), and dogs with Kiupel high-grade MCTs were significantly more likely to have metastases than were dogs with Kiupel low-grade MCTs (OR, 2.54). However, 3 of 52 (5.8%) dogs with Patnaik grade 1 tumors, 48 of 291 (16.5%) dogs with Patnaik grade 2 tumors, and 44 of 295 (14.9%) dogs with Kiupel low-grade tumors had metastatic disease. Conclusions and Clinical Relevance—Findings indicated that in dogs with cutaneous MCTs, prognostication should not rely on histologic grade alone, regardless of grading system used, but should take into account results of clinical staging.

Companion animal spontaneous tumors are suitable models for human cancer, primarily because both animal population and the tumors are genetically heterogeneous. Feline mammary carcinoma (FMC) is a highly aggressive, mainly hormone receptor–negative cancer, which has been proposed as a model for poor prognosis human breast cancer. We have identified and studied the feline orthologue of the HER2 gene, which is both an important prognostic marker and therapeutic target in human cancer. Feline HER2 (f-HER2) gene kinase domain is 92% similar to the human HER2 kinase. F-HER2–specific mRNA was found 3- to 18-fold increased in 3 of 3 FMC cell lines, in 1 of 4 mammary adenomas and 6 of 11 FMC samples using quantitative reverse transcription-PCR. Western blot showed that an anti-human HER2 antibody recognized a protein comigrating with the human p185HER2 in FMC cell lines. The same antibodies strongly stained 13 of 36 FMC archival samples. These data show that feline HER2 overexpression qualifies FMC as homologous to the subset of HER2 overexpressing, poor prognosis human breast carcinomas and as a suitable model to test innovative approaches to therapy of aggressive tumors.

Thanks to striking progress in both the understanding of anti-tumor immune response and the characterization of several tumor associated antigens (TAA), a more rational design and more sophisticated strategies for anti-tumor vaccination have been possible. However, the effectiveness of cancer vaccines in clinical trial is still partial, indicating that additional studies are needed to optimize their design and their pre-clinical testing. Indeed, anti-tumor vaccination success relies on the choice of the best TAA to be targeted and on the translational power of the pre-clinical model used to assess its efficacy. The chondroitin sulfate proteoglycan-4 (CSPG4) is a cell surface proteoglycan overexpressed in a huge range of human and canine neoplastic lesions by tumor cells, tumor microenvironment and cancer initiating cells. CSPG4 plays a central role in the oncogenic pathways required for malignant progression and metastatization. Thanks to these features and to its poor expression in adult healthy tissues, CSPG4 represents an ideal oncoantigen and thus an attractive target for anti-tumor immunotherapy. In this review we explore the potential of CSPG4 immune-targeting. Moreover, since it has been clearly demonstrated that spontaneous canine tumors mimic the progression of human malignancies better than any other pre-clinical model available so far, we reported also our results indicating that CSPG4 DNA vaccination is safe and effective in significantly increasing the survival of canine melanoma patients. Therefore, anti-CSPG4 vaccination strategy could have a substantial impact for the treatment of the wider population of spontaneous CSPG4-positive tumor affected dogs with a priceless translational value and a revolutionary implication for human oncological patients.

Purpose: Due to the many similarities with its human counterpart, canine malignant melanoma (cMM) is a valuable model in which to assess the efficacy of novel therapeutic strategies. The model is herein used to evaluate the immunogenicity, safety, and therapeutic efficacy of a human chondroitin sulfate proteoglycan-4 (hCSPG4) DNA-based vaccine. The fact that homology between hCSPG4 and cCSPG4 amino-acidic sequences stands at more than 80% provides the rationale for using an hCSPG4 DNA vaccine in the cMM model.Experimental Design: Dogs with stage II–III surgically resected CSPG4-positive oral MM were subjected to monthly intramuscular plasmid administration, which was followed immediately by electroporation (electrovaccination) for at least 6, and up to 20, months. The immunogenicity, safety, and therapeutic efficacy of the vaccine have been evaluated.Results: hCSPG4 electrovaccination caused no clinically relevant local or systemic side effects and resulted in significantly longer overall and disease-free survival times in 14 vaccinated dogs as compared with 13 nonvaccinated controls. All vaccinated dogs developed antibodies against both hCSPG4 and cCSPG4. Seven vaccinated dogs were also tested for a cCSPG4-specific T-cell response and only two gave a detectable interferon (IFN)γ response.Conclusion: Xenogeneic electrovaccination against CSPG4 is able to overcome host unresponsiveness to the “self” antigen and seems to be effective in treating cMM, laying the foundation for its translation to a human clinical setting. Clin Cancer Res; 20(14); 3753–62. ©2014 AACR.