Biology, diagnosis and treatment of canine appendicular osteosarcoma: Similarities and differences with human osteosarcoma

Immunohistochemical Investigation into Protein Expression Patterns of FOXO4, IRF8 and LEF1 in Canine Osteosarcoma

Osteosarcoma (OSA) is the most common type of primary bone malignancy in people and dogs. Our previous molecular comparisons of canine OSA against healthy bone resulted in the identification of differentially expressed protein-expressing genes (forkhead box protein O4 (FOXO4), interferon regulatory factor 8 (IRF8), and lymphoid enhancer binding factor 1 (LEF1)). Immunohistochemistry (IHC) and H-scoring provided semi-quantitative assessment of nuclear and cytoplasmic staining alongside qualitative data to contextualise staining (n = 26 patients). FOXO4 was expressed predominantly in the cytoplasm with significantly lower nuclear H-scores. IRF8 H-scores ranged from 0 to 3 throughout the cohort in the nucleus and cytoplasm. LEF1 was expressed in all patients with significantly lower cytoplasmic staining compared to nuclear. No sex or anatomical location differences were observed. While reduced levels of FOXO4 might indicate malignancy, the weak or absent protein expression limits its primary use as diagnostic tumour marker. IRF8 and LEF1 have more potential for prognostic and diagnostic uses and facilitate further understanding of their roles within their respective molecular pathways, including Wnt/beta-catenin/LEF1 signalling and differential regulation of tumour suppressor genes. Deeper understanding of the mechanisms involved in OSA are essential contributions towards the development of novel diagnostic, prognostic, and treatment options in human and veterinary medicine contexts.

Review: The PI3K-AKT-mTOR signal transduction pathway in canine cancer

Tumors in dogs and humans share many similar molecular and genetic features, incentivizing a better understanding of canine neoplasms not only for the purpose of treating companion animals, but also to facilitate research of spontaneously developing tumors with similar biologic behavior and treatment approaches in an immunologically competent animal model. Multiple tumor types of both species have similar dysregulation of signal transduction through phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB; AKT), and mechanistic target of rapamycin (mTOR), collectively known as the PI3K-AKT-mTOR pathway. This review aims to delineate the pertinent aspects of the PI3K-AKT-mTOR signaling pathway in health and in tumor development. It will then present a synopsis of current understanding of PI3K-AKT-mTOR signaling in important canine cancers and advancements in targeted inhibitors of this pathway.

Osteosarcoma of the wing in a sulfur-crested cockatoo

A 26-year-old female sulfur-crested cockatoo (Cacatua galerita) was evaluated for vocalizing through the night and extending her right wing. Physical examination revealed a large, firm mass extending from the humerus to the distal aspect of the elbow. Computed tomography confirmed a large aggressive mass of the right distal humerus with a large soft tissue component, severe osteolysis, and adjacent periosteal proliferation. Fine-needle aspirates of the mass were most compatible with sarcoma, and osteosarcoma was prioritized. An unstained slide was treated with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indolyl phosphate toluidine salt-phosphatase (NBT/BCIP) substrate for ALP detection and was strongly positive, confirming a diagnosis of osteosarcoma. A month later, the patient underwent wing amputation and arrested during recovery from anesthesia. Post-mortem examination and histopathology were consistent with osteosarcoma. This case report highlights a rare occurrence of osteosarcoma in a cockatoo as well as its cytologic and histologic features. Additionally, this report provides support for NBT/BCIP application in ALP-expressing tumors, a cytochemical stain that has been minimally investigated in avian species.

Antioxidant 1 copper chaperone gene expression and copper levels in dog osteosarcoma patients

Twenty-four dogs with OS underwent limb amputation. Serum, OS tumour, and normal bone were harvested at time of surgery. RNA was extracted and gene expression was performed using quantitative polymerase chain reaction (qPCR). Tissue and blood copper concentrations were also determined with spectrophotometry. Compared to bone, tumour samples had significantly higher expressions of antioxidant 1 copper chaperone (ATOX1, p = .0003). OS tumour copper levels were significantly higher than that of serum (p < .010) and bone (p = .038). Similar to our previous observations in mouse and human OS, dog OS demonstrates overexpression of genes that regulate copper metabolism (ATOX1), and subsequent copper levels. Dogs with OS may provide a robust comparative oncology platform for the further study of these factors, as well as potential pharmacologic interventions.

Comparative Molecular Characterization and Pharmacokinetics of IgG1-Fc and Engineered Fc Human Antibody Variants to Insulin-like Growth Factor 2 Receptor (IGF2R)

Novel therapeutic approaches are much needed for the treatment of osteosarcoma. Targeted radionuclide therapy (TRT) and radioimmunotherapy (RIT) are promising approaches that deliver therapeutic radiation precisely to the tumor site. We have previously developed a fully human antibody, named IF3, that binds to insulin-like growth factor 2 receptor (IGF2R). IF3 was used in TRT to effectively inhibit tumor growth in osteosarcoma preclinical models. However, IF3's relatively short half-life in mice raised the need for improvement. We generated an Fc-engineered version of IF3, termed IF3δ, with amino acid substitutions known to enhance antibody half-life in human serum. In this study, we confirmed the specific binding of IF3δ to IGF2R with nanomolar affinity, similar to wild-type IF3. Additionally, IF3δ demonstrated binding to human and mouse neonatal Fc receptors (FcRn), indicating the potential for FcRn-mediated endocytosis and recycling. Biodistribution studies in mice showed a higher accumulation of IF3δ in the spleen and bone than wild-type IF3, likely attributed to abnormal spleen expression of IGF2R in mice. Therefore, the pharmacokinetics data from mouse xenograft models may not precisely reflect their behavior in canine and human patients. However, the findings suggest both IF3 and IF3δ as promising options for the RIT of osteosarcoma.

Dog breeds and conformations predisposed to osteosarcoma in the UK: a VetCompass study

BACKGROUND

Osteosarcoma is a malignant bone neoplasia that has high welfare consequences for affected dogs. Awareness of breed and canine conformational risk factors for osteosarcoma can assist with earlier diagnosis and improved clinical management. Study of osteosarcoma in dogs also offers translational value for humans. Anonymised clinical data within VetCompass on dogs under primary veterinary care in the UK were searched for osteosarcoma cases. Descriptive statistics reported overall and breed-specific prevalence. Risk factor analysis used multivariable logistic regression modelling.

RESULTS

From 905,552 study dogs, 331 osteosarcoma cases were confirmed yielding a one-year period prevalence of 0.037% (95% CI: 0.033-0.041). Breeds with the highest annual prevalence were the Scottish Deerhound (3.28%, 95% CI 0.90-8.18), Leonberger (1.48%, 95% CI 0.41- 3.75), Great Dane (0.87%, 95% CI 0.43- 1.55) and Rottweiler (0.84%, 95% CI 0.64-1.07). The median age at diagnosis was 9.64 years (IQR: 7.97-11.41). Following multivariable modelling, 11 breeds showed increased odds of osteosarcoma compared with crossbred dogs. Breeds with the highest odds included Scottish Deerhound (OR 118.40, 95% CI 41.12-340.95), Leonberger (OR 55.79, 95% CI 19.68-158.15), Great Dane (OR 34.24, 95% CI 17.81-65.83) and Rottweiler (OR 26.67, 95% CI 18.57-38.29). Compared with breeds with mesocephalic skull conformation, breeds with dolichocephalic skull conformation (OR 2.72, 95% CI 2.06-3.58) had increased odds while breeds with brachycephalic skull conformation showed reduced odds (OR 0.50, 95% CI 0.32-0.80). Chondrodystrophic breeds had 0.10 times the odds (95% CI 0.06-0.15) compared with non-chondrodystrophic breeds. Increasing adult bodyweight was associated with increasing odds of osteosarcoma.

CONCLUSIONS

The current study cements the concept that breed, bodyweight and longer leg or longer skull length are all strong risk factors for osteosarcoma in dogs. With this awareness, veterinarians can update their clinical suspicion and judgement, breeders can select towards lower-risk animals, and researchers can robustly define more useful study populations for fundamental and translational bioscience.

Naturally occurring canine sarcomas: Bridging the gap from mouse models to human patients through cross-disciplinary research partnerships

Fueled by support from the National Cancer Institute's "Cancer Moonshot" program, the past few years have witnessed a renewed interest in the canine spontaneous cancer model as an invaluable resource in translational oncology research. Increasingly, there is awareness that pet dogs with cancer provide an accessible bridge to improving the efficiency of cancer drug discovery and clinical therapeutic development. Canine tumors share many biological, genetic, and histologic features with their human tumor counterparts, and most importantly, retain the complexities of naturally occurring drug resistance, metastasis, and tumor-host immune interactions, all of which are difficult to recapitulate in induced or genetically engineered murine tumor models. The utility of canine models has been particularly apparent in sarcoma research, where the increased incidence of sarcomas in dogs as compared to people has facilitated comparative research resulting in treatment advances benefitting both species. Although there is an increasing awareness of the advantages in using spontaneous canine sarcoma models for research, these models remain underutilized, in part due to a lack of more permanent institutional and cross-institutional infrastructure to support partnerships between veterinary and human clinician-scientists. In this review, we provide an updated overview of historical and current applications of spontaneously occurring canine tumor models in sarcoma research, with particular attention to knowledge gaps, limitations, and growth opportunities within these applications. Furthermore, we propose considerations for working within existing veterinary translational and comparative oncology research infrastructures to maximize the benefit of partnerships between veterinary and human biomedical researchers within and across institutions to improve the utility and application of spontaneous canine sarcomas in translational oncology research.

Characterization of IGF2R Molecular Expression in Canine Osteosarcoma as Part of a Novel Comparative Oncology Approach

Progress in prognostic factors, treatments, and outcome for both canine and human osteosarcoma (OS) has been minimal over the last three decades. Surface overexpression of the cation independent mannose-6-phosphate/insulin-like growth factor receptor type 2 (IGF2R) has been proven to occur in human OS cells. Subsequently, radioimmunotherapy (RIT) targeting IGF2R has demonstrated promising preliminary results. The main aims of this study were to investigate the expression of IGF2R in spontaneously occurring canine OS cells using immunohistochemistry (IHC) on archived biopsy samples and to assess its prognostic significance. Thirty-four dogs were included in the study. All cases showed that 80-100% of OS cells stained positive for IGF2R. IGF2R overexpression alone was not shown to have prognostic significance using both visual and quantitative methods of IHC staining intensity. This study has established for the first time the consistent expression of IGF2R in spontaneously occurring canine OS. This comparative oncology approach will allow further investigation into RIT as a novel treatment modality; first in canines and then in humans with OS. In addition, further studies should be performed to assess the true prognostic significance of IGF2R overexpression.

Nanocarriers in Veterinary Medicine: A Challenge for Improving Osteosarcoma Conventional Treatments

In recent years, several nanocarrier-based drug delivery systems, such as polymeric nanoparticles, solid lipid nanoparticles, metallic nanoparticles, liposomes, and others, have been explored to target and treat a wide variety of diseases. Their employment has brought many benefits, not only to human medicine but also to veterinary medicine, albeit at a slower rate. Soon, the use of nanocarriers could revolutionize the animal health sector, and many veterinary therapies will be more effective as a result. The purpose of this review is to offer an overview of the main applications of nanocarriers in the veterinary field, from supplements for animal health and reproduction to nanovaccines and nanotherapies. Among the major pathologies that can affect animals, special attention is given to canine osteosarcoma (OSA): a comparison with human OSA is provided and the main treatment options are reviewed emphasizing the benefits that nanocarriers could bring in the treatment of this widespread disease.

Improving Osteosarcoma Treatment: Comparative Oncology in Action

Osteosarcoma (OSA) is the most common pediatric malignant bone tumor. Although surgery together with neoadjuvant/adjuvant chemotherapy has improved survival for localized OSA, most patients develop recurrent/metastatic disease with a dismally poor outcome. Therapeutic options have not improved for these OSA patients in recent decades. As OSA is a rare and "orphan" tumor, with no distinct targetable driver antigens, the development of new efficient therapies is still an unmet and challenging clinical need. Appropriate animal models are therefore critical for advancement in the field. Despite the undoubted relevance of pre-clinical mouse models in cancer research, they present some intrinsic limitations that may be responsible for the low translational success of novel therapies from the pre-clinical setting to the clinic. From this context emerges the concept of comparative oncology, which has spurred the study of pet dogs as a uniquely valuable model of spontaneous OSA that develops in an immune-competent system with high biological and clinical similarities to corresponding human tumors, including in its metastatic behavior and resistance to conventional therapies. For these reasons, the translational power of studies conducted on OSA-bearing dogs has seen increasing recognition. The most recent and relevant veterinary investigations of novel combinatorial approaches, with a focus on immune-based strategies, that can most likely benefit both canine and human OSA patients have been summarized in this commentary.

Canine osteosarcoma in comparative oncology: Molecular mechanisms through to treatment discovery

Cancer is a leading cause of non-communicable morbidity and mortality throughout the world, similarly, in dogs, the most frequent cause of mortality is tumors. Some types of cancer, including osteosarcoma (OSA), occur at much higher rates in dogs than people. Dogs therefore not only require treatment themselves but can also act as an effective parallel patient population for the human disease equivalent. It should be noted that although there are many similarities between canine and human OSA, there are also key differences and it is important to research and highlight these features. Despite progress using chorioallantoic membrane models, 2D and 3D in vitro models, and rodent OSA models, many more insights into the molecular and cellular mechanisms, drug development, and treatment are being discovered in a variety of canine OSA patient populations.

The mitotic regulator polo-like kinase 1 as a potential therapeutic target for c-Myc-overexpressing canine osteosarcomas

Osteosarcoma is the most common primary malignant bone tumour in dogs, characterized by a locally aggressive and highly metastatic behaviour. Despite the current standards of care, most dogs succumb to the disease, indicating the need for novel treatment strategies. Polo-like kinase 1 (PLK1) is dysregulated in a variety of human cancer types, including osteosarcoma, and induces c-Myc accumulation. The crosstalk between the two molecules coordinates cell proliferation, differentiation, self-renewal and apoptosis. Therefore, PLK1 has recently emerged as a potential therapeutic target, mainly in tumours overexpressing c-Myc. BI 2536 is a selective PLK1 inhibitor promoting mitotic arrest and apoptosis in a variety of cancer cells. This research aimed at evaluating PLK1 and c-Myc protein expression in 53 appendicular canine osteosarcoma (cOSA) samples and the in vitro effects of BI 2536 on a c-Myc and PLK1-overexpressing cOSA cell line (D17). PLK1 and c-Myc expression in cOSA samples showed no correlation with clinicopathological data. However, c-Myc overexpression was associated with a significantly reduced overall survival (p = .003). Western Blot and RT-qPCR assays revealed that D17 expressed high protein and transcript levels of both PLK1 and MYC. When treated with BI 2536 (range 2.5-15 nM) for 24 h, D17 showed a substantial decrease in cell growth, inducing apoptosis and G₂ /M cell cycle arrest. Interestingly, under BI 2536 treatment, D17 showed decreased c-Myc protein levels. Consistent with human OSA, these preliminary data outline the prognostic value of c-Myc expression in cOSA and highlight the potential role of PLK1 as an antiproliferative therapeutic target for tumours overexpressing c-Myc.

Characterization of primary canine Sertoli cells as a model to test male reproductive toxicant

Sertoli cells play critical roles in regulating spermatogenesis and testis development by providing structural and nutritional support. This study aimed to develop a standard protocol for canine Sertoli cell isolation and culture; and characterize its biological features, functionality, and application of compound toxicity testing. Canine testicles were received from the neuter clinic, and three-step of enzymatic digestion was applied to isolate Sertoli cells. We characterized the growth and purity of Sertoli cells with the expression of SOX9, GATA4, and Clusterin. In addition, we selected cadmium as a model toxicant to evaluate the toxic responses in the newly established Sertoli cells using High-content Analysis (HCA). With our optimized protocol, the purity of isolated Sertoli cells was above 95%, as determined with Sertoli cell-specific protein markers of SOX9 and GATA4. More importantly, primary Sertoli cell populations could be expanded rapidly in vitro, passaged (up to seven), and cryopreserved. The HCA-based assay revealed that cadmium at 1 μM induced both disruptions of cytoskeletal and DNA damage responses. Furthermore, we established an HCA assay with the newly isolated and optimized culture of canine Sertoli cells to evaluate the epigenetic markers of histone modification. We found cadmium-induced differential changes in histone modifications H3Me3K9, H3Me3K36, H4Me3K20, and H4acK5. In summary, we have established the standardized protocol to produce canine Sertoli cells with Sertoli cell-specific phenotype. The isolation and expansion of large quantities of canine Sertoli cells will provide broad applications in studying male infertility, reproductive toxicology, testicular cancer, and cell therapy.

Canine Idiopathic Arteriopathy, Appendicular Bone Infarcts, and Neoplastic Transformation of Bone Infarcts in 108 Dogs (Canis lupus familiaris)

Osteosarcoma (OSA) is the most common primary bone tumor in both dogs and humans. The dog is an important research model for OSA, yet dogs have much higher prevalence of bone tumors than do humans, a disparity that has yet to be explained. Neoplastic transformation of cells within or adjacent to bone infarcts into primary bone tumors has been described in humans but only sparsely characterized in the veterinary literature. In this study, 653 cases of canine bone infarcts were received through a referral veterinary osteopathology service over a 14-y period. We identified an idiopathic disorder affecting the nutrient artery, termed canine idiopathic arteriopathy (CIA), which to our knowledge has no direct counterpart in human medicine. This disorder was documented alongside ischemic necrosis of the medullary cavity in 114 bone infarcts in 108 dogs. We hypothesize that CIA precipitated an ischemic environment, resulting in development of a bone infarct down- stream of the abnormal artery. In 52% (59 of 114) of cases, bone infarcts demonstrated evidence of repair (termed reparative bone infarcts [RBI]), while in 48% (55 of 114) of infarcts, a bone tumor was also present, including pleomorphic sarcoma, OSA, fibrosarcoma, and chondrosarcoma. In some cases, a spectrum of tumors was present. We hypothesize that the ischemic infarct environment provoked bone marrow mesenchymal stem cells (MSCs) to attempt repair of the stroma, and in approximately half of cases, MSCs underwent neoplastic transformation (BINT) to produce tumors. The most common sites of bone infarcts were the distal femur, distal radius, proximal humerus, and distal tibia, coinciding with common sites of canine OSA. The authors propose that CIA leading to bone infarcts and infarct-derived tumors, in combination with possible underdiagnosis of canine bone infarcts and misdiagnosis of some RBI as neoplasia, may contribute to the higher reported proportion of bone tumors in dogs compared with humans.

Anticancer activity of an Artemisia annua L. hydroalcoholic extract on canine osteosarcoma cell lines

Since ancient times, Artemisia annua (A. annua) has been used as a medicinal plant in Traditional Chinese Medicine. In addition, recent studies have investigated the cytotoxic effects of A. annua extracts towards cancer cells. The leading aim of the present research is to evaluate the cytotoxic effects of an hydroalcoholic extract of A. annua on two canine osteosarcoma (OSA) cell lines, OSCA-8 and OSCA-40, focusing on the possible involvement of ferroptosis. The quantitative determination of artemisinin concentration in the extract, culture medium and OSA cells was carried out through the use of an instrumental analytical method based on liquid chromatography coupled with spectrophotometric detection and tandem mass spectrometry (LC-DAD-MS/MS). OSCA-8 and OSCA-40 were exposed to different dilutions of the extract for the EC₅₀ calculation then the uptake of artemisinin by the cells, the effects on the cell cycle, the intracellular iron level, the cellular morphology and the lipid oxidation state were evaluated. A concentration of artemisinin of 63.8 ± 3.4 μg/mL was detected in the extract. A dose-dependent cytotoxic effect was evidenced. In OSCA-40 alterations of the cell cycle and a significantly higher intracellular iron content were observed. In both cell lines the treatment with the extract was associated with lipid peroxidation and with the appearance of a "ballooning" phenotype suggesting the activation of ferroptosis. In conclusion the A. annua idroalcoholic extract utilized in this study showed anticancer activity on canine OSA cell lines that could be useful in treating drug resistant canine OSAs.

Origin and Therapies of Osteosarcoma

Simple Summary

Osteosarcoma is the most common malignant bone tumor in children, with a 5-year survival rate ranging from 70% to 20% depending on the aggressiveness of the disease. The current treatments have not evolved over the past four decades due in part to the genetic complexity of the disease and its heterogeneity. This review will summarize the current knowledge of OS origin, diagnosis and therapies.

Abstract

Osteosarcoma (OS) is the most frequent primary bone tumor, mainly affecting children and young adults. Despite therapeutic advances, the 5-year survival rate is 70% but drastically decreases to 20–30% for poor responders to therapies or for patients with metastasis. No real evolution of the survival rates has been observed for four decades, explained by poor knowledge of the origin, difficulties related to diagnosis and the lack of targeted therapies for this pediatric tumor. This review will describe a non-exhaustive overview of osteosarcoma disease from a clinical and biological point of view, describing the origin, diagnosis and therapies.

Doxorubicin-Loaded Lipid Nanoparticles Coated with Calcium Phosphate as a Potential Tool in Human and Canine Osteosarcoma Therapy

Osteosarcoma (OSA) is the most frequently diagnosed primary malignant bone tumor in humans and dogs. In both species, standard chemotherapy can be limited by multidrug resistance of neoplastic cells, which prevents intracellular accumulation of cytotoxic drugs, resulting in chemotherapy failure. In this study, a lipophilic ester of doxorubicin (C12DOXO) was loaded into nanoparticles (NPs) using the “cold microemulsion dilution” method. The resulting NPs were then coated with calcium phosphate (CaP) in two different ways to have calcium or phosphate ions externally exposed on the surface. These systems were characterized by determining mean diameter, zeta potential, and drug entrapment efficiency; afterward, they were tested on human and canine OSA cells to study the role that the coating might play in increasing both drug uptake into tumor cells and cytotoxicity. Mean diameter of the developed NPs was in the 200–300 nm range, zeta potential depended on the coating type, and C12DOXO entrapment efficiency was in the 60–75% range. Results of studies on human and canine OSA cells were very similar and showed an increase in drug uptake and cytotoxicity for CaP-coated NPs, especially when calcium ions were externally exposed. Therefore, applications in both human and veterinary medicine can be planned in the near future.

Canine and murine models of osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor in children. Despite efforts to develop and implement new therapies, patient outcomes have not measurably improved since the 1980s. Metastasis continues to be the main source of patient mortality, with 30% of cases developing metastatic disease within 5 years of diagnosis. Research models are critical in the advancement of cancer research and include a variety of species. For example, xenograft and patient-derived xenograft (PDX) mouse models provide opportunities to study human tumor cells in vivo while transgenic models have offered significant insight into the molecular mechanisms underlying OS development. A growing recognition of naturally occurring cancers in companion species has led to new insights into how veterinary patients can contribute to studies of cancer biology and drug development. The study of canine cases, including the use of diagnostic tissue archives and clinical trials, offers a potential mechanism to further canine and human cancer research. Advancement in the field of OS research requires continued development and appropriate use of animal models. In this review, animal models of OS are described with a focus on the mouse and tumor-bearing pet dog as parallel and complementary models of human OS.

Histotripsy Ablation in Preclinical Animal Models of Cancer and Spontaneous Tumors in Veterinary Patients: A Review

New therapeutic strategies are direly needed in the fight against cancer. Over the last decade, several tumor ablation strategies have emerged as stand-alone or combination therapies. Histotripsy is the first completely noninvasive, nonthermal, and nonionizing tumor ablation method. Histotripsy can produce consistent and rapid ablations, even near critical structures. Additional benefits include real-time image guidance, high precision, and the ability to treat tumors of any predetermined size and shape. Unfortunately, the lack of clinically and physiologically relevant preclinical cancer models is often a significant limitation with all focal tumor ablation strategies. The majority of studies testing histotripsy for cancer treatment have focused on small animal models, which have been critical in moving this field forward and will continue to be essential for providing mechanistic insight. While these small animal models have notable translational value, there are significant limitations in terms of scale and anatomical relevance. To address these limitations, a diverse range of large animal models and spontaneous tumor studies in veterinary patients have emerged to complement existing rodent models. These models and veterinary patients are excellent at providing realistic avenues for developing and testing histotripsy devices and techniques designed for future use in human patients. Here, we provide a review of animal models used in preclinical histotripsy studies and compare histotripsy ablation in these models using a series of original case reports across a broad spectrum of preclinical animal models and spontaneous tumors in veterinary patients.

Genome-Wide Analyses for Osteosarcoma in Leonberger Dogs Reveal the CDKN2A/B Gene Locus as a Major Risk Locus

Dogs represent a unique spontaneous cancer model. Osteosarcoma (OSA) is the most common primary bone tumor in dogs (OMIA 001441-9615), and strongly resembles human forms of OSA. Several large- to giant-sized dog breeds, including the Leonberger, have a greatly increased risk of developing OSA. We performed genome-wide association analysis with high-density imputed SNP genotype data from 273 Leonberger cases with a median age of 8.1 [3.1–13.5] years and 365 controls older than eight years. This analysis revealed significant associations at the CDKN2A/B gene locus on canine chromosome 11, mirroring previous findings in other dog breeds, such as the greyhound, that also show an elevated risk for OSA. Heritability (h²_SNP) was determined to be 20.6% (SE = 0.08; p-value = 5.7 × 10⁻⁴) based on a breed prevalence of 20%. The 2563 SNPs across the genome accounted for nearly all the h²_SNP of OSA, with 2183 SNPs of small effect, 316 SNPs of moderate effect, and 64 SNPs of large effect. As with many other cancers it is likely that regulatory, non-coding variants underlie the increased risk for cancer development. Our findings confirm a complex genetic basis of OSA, moderate heritability, and the crucial role of the CDKN2A/B locus leading to strong cancer predisposition in dogs. It will ultimately be interesting to study and compare the known genetic loci associated with canine OSA in human OSA.

Histotripsy Ablation of Bone Tumors: Feasibility Study in Excised Canine Osteosarcoma Tumors

Osteosarcoma (OS) is a primary bone tumor affecting both dogs and humans. Histotripsy is a non-thermal, non-invasive focused ultrasound method using controlled acoustic cavitation to mechanically disintegrate tissue. In this study, we investigated the feasibility of treating primary OS tumors with histotripsy using a 500-kHz transducer on excised canine OS samples harvested after surgery at the Veterinary Teaching Hospital at Virginia Tech. Samples were embedded in gelatin tissue phantoms and treated with the 500-kHz histotripsy system using one- or two-cycle pulses at a pulse repetition frequency of 250 Hz and a dosage of 4000 pulses/point. Separate experiments also assessed histotripsy effects on normal canine bone and nerve using the same pulsing parameters. After treatment, histopathological evaluation of the samples was completed. To determine the feasibility of treating OS through intact skin/soft tissue, additional histotripsy experiments assessed OS with overlying tissues. Generation of bubble clouds was achieved at the focus in all tumor samples at peak negative pressures of 26.2 ± 4.5 MPa. Histopathology revealed effective cell ablation in treated areas for OS tumors, with no evidence of cell death or tissue damage in normal tissues. Treatment through tissue/skin resulted in generation of well-confined bubble clouds and ablation zones inside OS tumors. Results illustrate the feasibility of treating OS tumors with histotripsy.

Development of an exosomal gene signature to detect residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning

Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal messenger RNAs (mRNAs). The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by real-time quantitative reverse transcription PCR (qRT-PCR), while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups ("healthy", "osteosarcoma", "other bone tumor", or "non-neoplastic disease"). Pre-treatment samples from osteosarcoma cases were used as the training set, and a validation set from post-treatment samples was used for testing, classifying as "osteosarcoma detected" or "osteosarcoma-NOT detected". Dogs in a validation set whose post-treatment samples were classified as "osteosarcoma-NOT detected" had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof of concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.

Early immunohistochemical detection of pulmonary micrometastases in dogs with osteosarcoma

Background

Despite decades of research, the early phases of metastatic development are still not fully understood. Canine osteosarcoma (OS) is a highly aggressive cancer, with a high metastatic rate (> 90%), despite a low overt metastatic prevalence at initial diagnosis (< 15%). Canine OS is generally regarded as a good clinically relevant model for human OS. The aim of this hypothesis-generating study was to evaluate a method to detect pulmonary micrometastases and study their prevalence in dogs with OS without macroscopic metastases. We prospectively enrolled dogs with OS that received no cancer-specific treatment (n = 12) and control dogs without cancer (n = 2). Dogs were necropsied and sampled immediately after euthanasia. The OS dogs were classified as having macroscopic metastases (n = 2) or not (n = 10). We immunohistochemically stained one tissue sample from each of the seven lung lobes from each dog with a monoclonal antibody (TP-3) to identify micrometastases (defined as clusters of 5–50 tumour cells), microscopic metastases (> 50 tumour cells) and TP-3 positive single cells (< 5 tumour cells).

Results

We showed that pulmonary micrometastases easily overseen on routine histology could be detected with TP-3. Pulmonary micrometastases and microscopic metastases were present in two dogs with OS without macroscopic metastases (20%). Micrometastases were visualised in three (43%) and four (57%) of seven samples from these two dogs, with a mean of 0.6 and 1.7 micrometastases per sample. Microscopic metastases were present in one (14%) and four (57%) of seven samples from the same two dogs, with a mean of 0.14 and 1.0 microscopic metastases per sample. There were four (57%) and two (29%) samples with neither microscopic metastases nor micrometastases for each of these two dogs. The prevalence of pulmonary micrometastases (20%) was significantly lower than expected (> 90%) based on commonly expected metastatic rates after amputation (P < 0.0001). There was no statistically significant difference in the number of TP-3 positive single cells in between groups (P = 0.85).

Conclusions

Pulmonary micrometastases could be detected with TP-3 immunohistochemistry in a subset of dogs with OS before macroscopic metastases had developed. We propose that dogs with spontaneous OS represent clinically relevant models to study early micrometastatic disease.

In Vitro Studies on the Influence of Meloxicam on Cytotoxic Activity Induced by Risedronate Sodium in Canine (D-17) and Human (U-2 OS) Osteosarcoma Cell Lines

Simple Summary

The aim of this in vitro study was to reveal the pharmacological interactions between meloxicam and risedronate sodium, used jointly to induce a cytotoxic effect in canine (D-17) and human (U-2 OS) osteosarcoma cell lines. Meloxicam, a non-steroidal anti-inflammatory drug, is capable of intensifying the cytotoxic activity of risedronate sodium routinely used in bone tissue metabolic diseases. The cell cultures were incubated, tested, and evaluated according to standard protocols. The study demonstrated a greater susceptibility of canine osteosarcoma cells in vitro to the investigated drug combination than the human. In both cases, meloxicam alone showed low cytotoxic activity against the tested cell lines, but the two compounds combined were synergic.

Abstract

The study describes the cytotoxic effect against human and canine osteosarcoma (U-2 OS and D-17) cell lines induced by risedronate sodium and meloxicam per se and in combination. Both cell lines were prepared according to standard procedures for cell cultures studies. The cell viability was estimated in both cell lines treated with chosen concentrations of risedronate sodium and meloxicam. The apoptosis assessment was carried out using TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay. EC₅₀ values, computed for risedronate sodium and meloxicam cytotoxicity, showed comparable effects against the canine OS cell line in similar concentration of both drugs. In case of human OS, the stronger cytotoxic effect of risedronate sodium was proved. The EC₅₀ values for meloxicam in both cell lines were, statistically, significantly different (* p < 0.05). Moreover, the cytotoxic effect of a combined administration of meloxicam and risedronate sodium in doses 100 µg/mL, compared with the negative control showed statistically significant differences. The human OS cell line was more resistant to both compounds than the canine OS cell line. The apoptotic effect in canine and human osteosarcoma triggered by risedronate sodium and meloxicam was statistically significant (p < 0.05). The cytotoxic effect induced with 100 µg/mL of risedronate sodium proved statistically significant differences between both tested cell lines compared to negative control. The results obtained with 10 and 100 µg/mL of meloxicam were not statistically significant. The study showed the synergic mechanism of action of risedronate sodium and meloxicam, but the concentrations used in vitro will not be possible to achieve in in vivo. Therefore, our results serve as basis only to design future studies on the tissue level.

Role of Periostin Expression in Canine Osteosarcoma Biology and Clinical Outcome

Periostin is a matricellular protein important in regulating bone, tooth, and cardiac development. In pathologic conditions, periostin drives allergic and fibrotic inflammatory diseases and is also overexpressed in certain cancers. Periostin signaling in tumors has been shown to promote angiogenesis, metastasis, and cancer stem cell survival in rodent models, and its overexpression is associated with poor prognosis in human glioblastoma. However, the role of periostin in regulating tumorigenesis of canine cancers has not been evaluated. Given its role in bone development, we sought to evaluate mRNA and protein expression of periostin in canine osteosarcoma (OS) and assess its association with patient outcome. We validated an anti-human periostin antibody cross-reactive to canine periostin via western blot and immunohistochemistry and evaluated periostin expression in microarray data from 49 primary canine OS tumors and 8 normal bone samples. Periostin mRNA was upregulated greater than 40-fold in canine OS tumors compared to normal bone and was significantly correlated with periostin protein expression based on quantitative image analysis. However, neither periostin mRNA nor protein expression were associated with time to metastasis in this cohort. Gene Set Enrichment Analysis demonstrated significant enhancement of pro-tumorigenic pathways including canonical WNT signaling, epithelial-mesenchymal transition, and angiogenesis in periostin-high tumors, while periostin-low tumors demonstrated evidence of heightened antitumor immune responses. Overall, these data identify a novel antibody that can be used as a tool for evaluation of periostin expression in dogs and suggest that investigation of Wnt pathway-targeted drugs in periostin overexpressing canine OS may be a potential therapeutic target.

Pain Treatment in the Companion Canine Model to Validate Rodent Results and Incentivize the Transition to Human Clinical Trials

One of the biggest challenges for analgesic drug development is how to decide if a potential analgesic candidate will work in humans. What preclinical data are the most convincing, incentivizing and most predictive of success? Such a predicament is not unique to analgesics, and the pain field has certain advantages over drug development efforts in areas like neuropsychiatry where the etiological origins are either unknown or difficult to ascertain. For pain, the origin of the problem frequently is known, and the causative peripheral tissue insult might be observable. The main conundrum centers around evaluation of translational cell- and rodent-based results. While cell and rodent models are undeniably important first steps for screening, probing mechanism of action, and understanding factors of adsorption, distribution metabolism and excretion, two questions arise from such studies. First, are they reliable indicators of analgesic performance of a candidate drug in human acute and chronic pain? Second, what additional model systems might be capable of increasing translational confidence? We address this second question by assessing, primarily, the companion canine model, which can provide particularly strong predictive information for candidate analgesic agents in humans. This statement is mainly derived from our studies with resiniferatoxin (RTX) a potent TRPV1 agonist but also from protein therapeutics using a conjugate of Substance P and saporin. Our experience, to date, is that rodent models might be very well suited for acute pain translation, but companion canine models, and other large animal studies, can augment initial discovery research using rodent models for neuropathic or chronic pain. The larger animal models also provide strong translational predictive capacity for analgesic performance in humans, better predict dosing parameters for human trials and provide insight into behavior changes (bladder, bowel, mood, etc.) that are not readily assessed in laboratory animals. They are, however, not without problems that can be encountered with any experimental drug treatment or clinical trial. It also is important to recognize that pain treatment is a major veterinary concern and is an intrinsically worthwhile endeavor for animals as well as humans.

Immunohistochemical Characterisation of GLUT1, MMP3 and NRF2 in Osteosarcoma

Osteosarcoma (OSA) is an aggressive bone malignancy. Unlike many other malignancies, OSA outcomes have not improved in recent decades. One challenge to the development of better diagnostic and therapeutic methods for OSA has been the lack of well characterized experimental model systems. Spontaneous OSA in dogs provides a good model for the disease seen in people and also remains an important veterinary clinical challenge. We recently used RNA sequencing and qRT-PCR to provide a detailed molecular characterization of OSA relative to non-malignant bone in dogs. We identified differential mRNA expression of the solute carrier family 2 member 1 (SLC2A1/GLUT1), matrix metallopeptidase 3 (MMP3) and nuclear factor erythroid 2–related factor 2 (NFE2L2/NRF2) genes in canine OSA tissue in comparison to paired non-tumor tissue. Our present work characterizes protein expression of GLUT1, MMP3 and NRF2 using immunohistochemistry. As these proteins affect key processes such as Wnt activation, heme biosynthesis, glucose transport, understanding their expression and the enriched pathways and gene ontologies enables us to further understand the potential molecular pathways and mechanisms involved in OSA. This study further supports spontaneous OSA in dogs as a model system to inform the development of new methods to diagnose and treat OSA in both dogs and people.

Genomic and Transcriptomic Characterization of Canine Osteosarcoma Cell Lines: A Valuable Resource in Translational Medicine

Osteosarcoma (OSA) represents the most common primary bone tumor in dogs and is characterized by a highly aggressive behavior. Cell lines represent one of the most suitable and reproducible pre-clinical models, and therefore the knowledge of their molecular landscape is mandatory to investigate oncogenic mechanisms and drug response. The present study aims at determining variants, putative driver genes, and gene expression aberrations by integrating whole-exome and RNA sequencing. For this purpose, eight canine OSA cell lines and one matched pair of primary tumor and normal tissue were analyzed. Overall, cell lines revealed a mean tumor mutational burden of 9.6 mutations/Mb (range 3.9–16.8). Several known oncogenes and tumor suppressor genes, such as ALK, MYC, and MET, were prioritized as having a likely role in canine OSA. Mutations in eight genes, previously described as human OSA drivers and including TP53, PTCH1, MED12, and PI3KCA, were retrieved in our cell lines. When variants were cross-referenced with human OSA driver mutations, the E273K mutation of TP53 was identified in the Wall cell line and tumor sample. The transcriptome profiling detected two possible p53 inactivation mechanisms in the Wall cell line on the one hand, and in D17 and D22 on the other. Moreover, MET overexpression, potentially leading to MAPK/ERK pathway activation, was observed in D17 and D22 cell lines. In conclusion, our data provide the molecular characterization of a large number of canine OSA cell lines, allowing future investigations on potential therapeutic targets and associated biomarkers. Notably, the Wall cell line represents a valuable model to empower prospective in vitro studies both in human and in dogs, since the TP53 driver mutation was maintained during cell line establishment and was widely reported as a mutation hotspot in several human cancers.

The prognostic significance of metabolic tumour volume and total lesion glycolysis for dogs staged for appendicular osteosarcoma with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography

Metabolic tumour volumes (MTV) and total lesion glycolysis (TLG) are metabolic parameters that are becoming more commonly reported in human medicine to quantify tumours detected on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸ F-FDG PET/CT). In this retrospective study dogs afflicted with appendicular osteosarcoma that were staged with ¹⁸ F-FDG PET/CT had MTV and TLG at a variety of set and fixed thresholds calculated by two observers. These values, along with SUV_max , were evaluated for prognostic significance in this population of dogs. There was excellent correlation between two observers for all values. Multiple volumetric parameters were significantly associated with survival. SUV_max had the highest sensitivity for survival and TLG at 2.5 SUV*cm³ had the highest specificity for prediction of survival based on ROC calculations. The SUV_max , MTV at 2.5 SUV and TLG at 2.5 SUV*cm³ were significantly different between dogs that survived more than or less than 1 year. This study is the first of its kind in veterinary medicine that retrospectively evaluated volumetric tumour values for prognostic significance and may provide a basis for standardized method of reporting ¹⁸ F-FDG PET/CT results.

Roles of Parathyroid Hormone-Related Protein (PTHrP) and Its Receptor (PTHR1) in Normal and Tumor Tissues: Focus on Their Roles in Osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor and originates from bone forming mesenchymal cells and primarily affects children and adolescents. The 5-year survival rate for OS is 60 to 65%, with little improvement in prognosis during the last four decades. Studies have demonstrated the evolving roles of parathyroid hormone-related protein (PTHrP) and its receptor (PTHR1) in bone formation, bone remodeling, regulation of calcium transport from blood to milk, regulation of maternal calcium transport to the fetus and reabsorption of calcium in kidneys. These two molecules also play critical roles in the development, progression and metastasis of several tumors such as breast cancer, lung carcinoma, chondrosarcoma, squamous cell carcinoma, melanoma and OS. The protein expression of both PTHrP and PTHR1 have been demonstrated in OS, and their functions and proposed signaling pathways have been investigated yet their roles in OS have not been fully elucidated. This review aims to discuss the latest research with PTHrP and PTHR1 in OS tumorigenesis and possible mechanistic pathways.

This review is dedicated to Professor Michael Day who died in May 2020 and was a very generous collaborator.

Dog breeds and body conformations with predisposition to osteosarcoma in the UK: a case-control study

Background

Osteosarcoma is an aggressive and painful bone neoplasm in dogs. Previous studies have reported epidemiological associations suggesting that large body mass, long bone length and the genetics of certain breeds including the Rottweiler are associated with elevated osteosarcoma risk. However, these studies were often limited by selection bias and confounding factors, and have rarely offered insights into breed-associated protection for osteosarcoma. The current study includes 1756 appendicular and axial osteosarcoma cases presenting to VPG Histology (Bristol, UK) compared against a control population of 905,211 dogs without osteosarcoma from primary care electronic patient records in the VetCompass™ dataset.

Methods and study design

Retrospective, case-control study. Multivariable logistic regression analysis explored associations between demographic risk factors (including breed, chondrodystrophy, age, sex/neuter status, skull-shape, and body mass) and osteosarcoma of all anatomical sites.

Results

We identified several breeds with increased and reduced odds of osteosarcoma. At highest risk were the Rottweiler and Great Dane, with > 10 times the odds of osteosarcoma compared with crossbreds, and the Rhodesian Ridgeback, which has not featured in previous lists of at-risk breeds for osteosarcoma, and had an odds ratio of 11.31 (95% confidence interval 7.37–17.35). Breeds at lowest risk of osteosarcoma (protected breeds) included the Bichon Frise, the French Bulldog and the Cavalier King Charles Spaniel, all with odd ratios of less than 0.30 compared with crossbreds. Body mass was strongly associated with osteosarcoma risk; dogs over 40 kg exhibited osteosarcoma odds of 45.44 (95% confidence interval 33.74–61.20) compared with dogs less than 10 kg. Chondrodystrophic breeds had an osteosarcoma odds ratio of 0.13 (95% confidence interval 0.11–0.16) compared with non-chondrodystrophic breeds.

Conclusions

This study provides evidence of strong breed-associated osteosarcoma risk and protection, suggesting a genetic basis for osteosarcoma pathogenesis. It highlights that breeds selected for long legs/large body mass are generally overrepresented amongst at-risk breeds, whilst those selected for short leg length/small body mass are generally protected. These findings could inform genetic studies to identify osteosarcoma risk alleles in canines and humans; as well as increasing awareness amongst veterinarians and owners, resulting in improved breeding practices and clinical management of osteosarcoma in dogs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40575-021-00100-7.

Evaluation of tumor immunity after administration of conditionally replicative adenoviral vector in canine osteosarcoma patients

Osteosarcoma is one among the most common neoplasms in dogs. Current treatments show limited efficacy and fail to prevent metastasis. Conditionally replicative adenoviruses (CRAd) replicate exclusively in targeted tumor cells and release new virus particles to infect additional cells. We proposed that OC-CAVE1 (CAV2 with the E1A promoter replaced with the osteocalcin promotor) may also enhance existing immunity against tumors by overcoming immune tolerance via exposure of new epitopes and cytokine signaling. Eleven client-owned dogs with spontaneously occurring osteosarcomas were enrolled in a pilot study. All dogs were injected with OC-CAVE1 following amputation of the affected limb or limb-sparing surgery. Dogs were monitored for viremia and viral shedding. There was minimal virus shedding in urine and feces by the 6th day and no virus was present in blood after 4 weeks. CAV-2 antibody-titers increased in all of the patients, post-CRAd injection. Immunological assays were performed to monitor 1) humoral response against tumors, 2) levels of circulatory CD11c + cells, 3) levels of regulatory T cells, and 4) cytotoxic activity of tumor specific T cells against autologous tumor cells between pre-CRAd administration and 4 weeks post-CRAd administration samples. Administration of the CRAd OC-CAVE1 resulted in alteration of some immune response parameters but did not appear to result in increased survival duration. However, 2 dogs in the study achieved survival times in excess of 1 year. Weak replication of OC-CAVE1 in metastatic cells and delay of chemotherapy following CRAd treatment may contribute to the lack of immune response and improvement in survival time of the clinical patients.

Unraveling the chaotic genomic landscape of primary and metastatic canine appendicular osteosarcoma with current sequencing technologies and bioinformatic approaches

Osteosarcoma is a rare disease in children but is one of the most common cancers in adult large breed dogs. The mutational landscape of both the primary and pulmonary metastatic tumor in two dogs with appendicular osteosarcoma (OSA) was comprehensively evaluated using an automated whole genome sequencing, exome and RNA-seq pipeline that was adapted for this study for use in dogs. Chromosomal lesions were the most common type of mutation. The mutational landscape varied substantially between dogs but the lesions within the same patient were similar. Copy number neutral loss of heterozygosity in mutant TP53 was the most significant driver mutation and involved a large region in the middle of chromosome 5. Canine and human OSA is characterized by loss of cell cycle checkpoint integrity and DNA damage response pathways. Mutational profiling of individual patients with canine OSA would be recommended prior to targeted therapy, given the heterogeneity seen in our study and previous studies.

The occurrence of osteosarcoma after tibial fracture repair in a dog

Background:

There are few detailed reports on implant-associated sarcoma in dogs; however, loose implants, metal type, and infection have not been shown as specific risk factors for this condition.

Case Description:

A 14-year-old spayed female Labrador retriever was referred to our hospital with a main complaint of chronic right hind lameness after previous tibial fracture repair. On radiographs, rupture of the bone plate and screws with swelling of the surrounding soft tissue was observed, and osteosarcoma (OSA) was diagnosed after histopathological examinations. During amputation surgery, a plastic band was found associated with the implant.

Conclusion:

Veterinary surgeons should be aware of implant-associated OSA and refrain from using non-medical materials in the implants. Furthermore, they should recommend the removal of orthopedic implants after fracture repair.

Comparative Immunology and Immunotherapy of Canine Osteosarcoma

Approximately 800 people are diagnosed with osteosarcoma (OSA) per year in the USA. Although 70% of patients with localized OSA are cured with multiagent chemotherapy and surgical resection, the prognosis for patients with metastatic or relapsed disease is guarded. The small number of patients diagnosed annually contributes to an incomplete understanding of disease pathogenesis, and challenges in performing appropriately powered clinical trials and detecting correlative biomarkers of response. While mouse models of OSA are becoming increasingly sophisticated, they generally fail to accurately recapitulate tumor heterogeneity, tumor microenvironment (TME), systemic immune dysfunction, and the clinical features of tumor recurrence, metastases, and chemoresistance, which influence outcome. Pet dogs spontaneously develop OSA with an incidence that is 30-50 times higher than humans. Canine OSA parallels the human disease in its clinical presentation, biological behavior, genetic complexity, and therapeutic management. However, despite therapy, most dogs die from metastatic disease within 1 year of diagnosis. Since OSA occurs in immune-competent dogs, immune factors that sculpt tumor immunogenicity and influence responses to immune modulation are in effect. In both species, immune modulation has shown beneficial effects on patient outcome and work is now underway to identify the most effective immunotherapies, combination of immunotherapies, and correlative biomarkers that will further improve clinical response. In this chapter, the immune landscape of canine OSA and the immunotherapeutic strategies used to modulate antitumor immunity in dogs with the disease will be reviewed. From this immunological viewpoint, the value of employing dogs with spontaneous OSA to accelerate and inform the translation of immunotherapies into the human clinic will be underscored.

Targeting Mechanotransduction in Osteosarcoma: A Comparative Oncology Perspective

Mechanotransduction is the process in which cells can convert extracellular mechanical stimuli into biochemical changes within a cell. While this a normal process for physiological development and function in many organ systems, tumour cells can exploit this process to promote tumour progression. Here we summarise the current state of knowledge of mechanotransduction in osteosarcoma (OSA), the most common primary bone tumour, referencing both human and canine models and other similar mesenchymal malignancies (e.g., Ewing sarcoma). Specifically, we discuss the mechanical properties of OSA cells, the pathways that these cells utilise to respond to external mechanical cues, and mechanotransduction-targeting strategies tested in OSA so far. We point out gaps in the literature and propose avenues to address them. Understanding how the physical microenvironment influences cell signalling and behaviour will lead to the improved design of strategies to target the mechanical vulnerabilities of OSA cells.

Relationship Between Clinicopathological Features and Prognosis in Appendicular Osteosarcoma in Dogs

Osteosarcoma is the most common primary bone neoplasm in dogs and often involves the appendicular skeleton. We report the clinicopathological and prognostic features of appendicular osteosarcomas diagnosed in 153 dogs from 2008 to 2018. The survival data for 22 dogs that underwent surgery and chemotherapy were statistically compared with the clinical, histopathological and immunohistochemical data for correlation with prognosis. The affected dogs had a mean age of 9.1 years and a mean body weight of 33.4 kg. No sex predilection was detected, although the incidence was slightly higher in females (52%). Large mixed and purebred dogs were most commonly affected. Long bones were affected in 124 cases (92.5%; 124/134). The extremities affected within long bones were the metaphysis of the proximal humerus (29%), distal radius (17.7%), distal femur (15.3%) and proximal tibia (7.2%). Histologically, osteoblastic osteosarcoma was most commonly detected (56.9%), followed by chondroblastic (13.7%), telangiectatic (11.8%), fibroblastic (7.8%), giant cell-rich (5.2%) and poorly differentiated neoplasms (4.6%). Regional lymph nodes were available for analysis in 28 out of 70 excisional biopsies from amputated entire limbs. Metastases to regional lymph nodes were observed in 14.3% (4/28) of these cases. Distant metastases were found in 75% (39/52) of cases in which diagnostic imaging or necropsy was carried out. The lungs were the most common site of metastasis (87.2%; 34/39 cases). Weight, age, sex, affected limb or bone, histological classification, mitotic count or histological grade did not influence survival (P >0.05). Neoplasms located at proximal extremities (n = 7) of affected limbs had a tendency for a poorer prognosis than those at distal extremities (n = 15) (P = 0.06). For these cases, the 1-year survival rate was 14.3% compared with 40% for neoplasms at distal extremities. There was no significant difference in the survival rate when amputation (n = 16) or limb preservation (n = 6) techniques were employed with chemotherapy (P = 0.20). The survival period of dogs that had undergone limb amputation, or limb preservation surgery, and chemotherapy was 73-1,185 days, with a mean and median of 376 and 256 days, respectively. Mild to marked cytoplasmic immunolabelling of osteopontin was found in all cases but the intensity (P = 0.66) and percentage of neoplastic cells labelled (P = 0.49) did not influence survival.

Inhibitory Effects of a Reengineered Anthrax Toxin on Canine and Human Osteosarcoma Cells

Canine and human osteosarcomas (OSA) share similarities. Novel therapies are necessary for these tumours. The Bacillus anthracis toxin was reengineered to target and kill cells with high expressions of matrix metalloproteinases (MMPs) and urokinase plasminogen activator (uPA). Since canine OSA express MMPs and uPA, we assessed whether the reengineered toxin could show efficacy against these tumours. Two OSA cell lines (canine D17 and human MG63) and a non-neoplastic canine osteoblastic cell line (COBS) were used. Cells were treated with different concentrations of the reengineered anthrax toxin and cell viability was quantified using MTT assay. The cell cycle, apoptosis, and necrosis were analysed by flow cytometry. The wound-healing assay was performed to quantify the migration capacity of treated cells. D17 and MG63 cells had significantly decreased viability after 24 h of treatment. Cell cycle analysis revealed that OSA cells underwent apoptosis when treated with the toxin, whereas COBS cells arrested in the G1 phase. The wound-healing assay showed that D17 and MG63 cells had a significantly reduced migration capacity after treatment. These results point for the first time towards the in vitro inhibitory effects of the reengineered anthrax toxin on OSA cells; this reengineered toxin could be further tested as a new therapy for OSA.

Circular RNAs Are Regulators of Diverse Animal Transcriptomes: One Health Perspective

Derived from linear (parental) precursor mRNA, circRNA are recycled exons and introns whose ends are ligated. By titrating microRNAs and RNA binding proteins, circRNA interconnect networks of competing endogenous RNAs. Without altering chromosomal DNA, circRNA regulates skeletal muscle development and proliferation, lactation, ovulation, brain development, and responses to infections and metabolic stress. This review integrates emerging knowledge of circRNA activity coming from genome-wide characterizations in many clades of animals. circRNA research addresses one of the main pillars of the One Health vision – to improve the health and productivity of food animals and generate translational knowledge in animal species.

Clinical significance and in vitro cellular regulation of hypoxia mimicry on HIF-1α and downstream genes in canine appendicular osteosarcoma

Cellular adaptation to a hypoxic microenvironment is essential for tumour progression and is largely mediated by HIF-1α and hypoxia-regulated factors, including CXCR4, VEGF-A and GLUT-1. In human osteosarcoma, hypoxia is associated with resistance to chemotherapy as well as with metastasis and poor survival, whereas little is known about its role in canine osteosarcoma (cOSA). This study aimed primarily to evaluate the prognostic value of several known hypoxic markers in cOSA. Immunohistochemical analysis for HIF-1α, CXCR4, VEGF-A and GLUT-1 was performed on 56 appendicular OSA samples; correlations with clinicopathological features and outcome was investigated. The second aim was to investigate the in vitro regulation of markers under chemically induced hypoxia (CoCl₂). Two primary canine osteosarcoma cell lines were selected, and Western blotting, immunofluorescence and qRT-PCR were used to study protein and gene expression. Dogs with high-grade OSA (35.7%) were more susceptible to the development of metastases (P = 0.047) and showed high HIF-1α protein expression (P = 0.007). Moreover, HIF-1α overexpression (56%) was correlated with a shorter disease-free interval (DFI; P = 0.01), indicating that it is a reliable negative prognostic marker. The in vitro experiments identified an accumulation of HIF-1α in cOSA cells after chemically induced hypoxia, leading to a significant increase in GLUT-1 transcript (P = 0.02). HIF-1α might be a promising prognostic marker, highlighting opportunities for the use of therapeutic strategies targeting the hypoxic microenvironment in cOSA. These results reinforce the role of the dog as a comparative animal model since similar hypoxic mechanisms are reported in human osteosarcoma.

miR-106B-25 Cluster expression: a comparative human and canine osteosarcoma study

Background

Osteosarcoma (OS) is the most common primary malignant bone tumour in dogs and human beings, characterised by similar genetic and clinical features. With the aim to define similarities and differences in the biological aspects involved in OS progression, a comparative study was performed to create a model to improve patient outcome.

Methods

First, the expression of microRNAs (miRNAs) belonging to the cluster miR-106b-25 (miR-106b, miR-25 and miR-93-5p) in human and canine OS tissue was compared.

Results

miR-25 and miR-106b presented a variable expression not significantly different from the corresponding normal bone, while miR-93-5p expression was increased in all OS specimens, with higher levels in the canine subset compared with human. Accordingly, its target p21 presented a weaker and less homogeneous immunostaining distribution in the canine group. Given the high expression of miR-93-5p in all OS specimens, the functional response of human 143B and canine DAN OS cells to miRNA inhibition was evaluated. Although p21 expression increased after miR-93-5p inhibition both at mRNA and protein level, a more significant cell response in terms of proliferation and apoptosis was seen in canine OS cells.

Conclusions

In conclusion, canine OS tissue and cell line presented higher expression levels of miR-93-5p than human OS. In addition, the introduction of miR-93-5p inhibitor caused a cell response in 143B and DAN that differed for the more intense functional impact in the canine OS cell line.

Parathyroid hormone receptor 1 (PTHR1) is a prognostic indicator in canine osteosarcoma

Osteosarcoma (OS) is the most common malignant primary bone tumour in humans and dogs. Several studies have established the vital role of parathyroid hormone-related protein (PTHrP) and its receptor (PTHR1) in bone formation and remodeling. In addition, these molecules play a role in the progression and metastasis of many human tumour types. This study investigated the expression of PTHR1 and PTHrP in canine OS tissues and assessed their prognostic value. Formalin-fixed, paraffin-embedded tissue samples from 50 dogs diagnosed with primary OS were immunolabeled with antibodies specific for PTHR1 and PTHrP. The immunostaining intensity of tumours from patients with OS was correlated with survival time. Both PTHR1 and PTHrP were detected in all OS samples (n = 50). Dogs with OS tumours showing high immunostaining intensity for PTHR1 (n = 36) had significantly shorter survival times (p = 0.028, Log Rank; p = 0.04, Cox regression) when compared with OS that had low immunostaining intensity for PTHR1 (n = 14).PTHrP immunostaining intensity did not correlate with survival time (p > 0.05). The results of this study indicate that increased expression of PTHR1 antigen in canine OS is associated with poor prognosis. This suggests that PTHR1 may be useful as a prognostic indicator in canine OS.

In vitro and in vivo effects of toceranib phosphate on canine osteosarcoma cell lines and xenograft orthotopic models

Canine osteosarcoma (OSA) is the most common primary malignant bone tumour in dogs, and it has a high metastatic rate and poor prognosis. Toceranib phosphate (TOC; Palladia, Zoetis) is a veterinary tyrosine kinase inhibitor that selectively inhibits VEGFR-2, PDGFRs and c-Kit, but its efficacy is not yet fully understood in the treatment of canine OSA. Here, we evaluated the functional effects of TOC on six OSA cell lines by transwell, wound healing and colony formation assays. Subsequently, two cell lines (Wall and Penny) were selected and were inoculated in mice by intrafemoral injection to develop an orthotopic xenograft model of canine OSA. For each cell line, 30 mice were xenografted; half of them were used as controls, and the other half were treated with TOC at 40 mg/kg body weight for 20 days. TOC inhibited cell growth of all cell lines, but reduced invasion and migration was only observed in Penny and Wall cell lines. In mice engrafted with Penny cells and subjected to TOC treatment, decreased tumour growth was observed, and PDGFRs and c-Kit mRNA were downregulated. Immunohistochemical analyses demonstrated a significant reduction of Ki67 staining in treated mice when compared to controls. The results obtained here demonstrate that TOC is able to slightly inhibit cell growth in vitro, while its effect is evident only in a Penny cell xenograft model, in which TOC significantly reduced tumour size and the Ki67 index without modifying apoptosis markers.

Of Mice, Dogs, Pigs, and Men: Choosing the Appropriate Model for Immuno-Oncology Research

The immune system plays dual roles in response to cancer. The host immune system protects against tumor formation via immunosurveillance; however, recognition of the tumor by immune cells also induces sculpting mechanisms leading to a Darwinian selection of tumor cell variants with reduced immunogenicity. Cancer immunoediting is the concept used to describe the complex interplay between tumor cells and the immune system. This concept, commonly referred to as the three E's, is encompassed by 3 distinct phases of elimination, equilibrium, and escape. Despite impressive results in the clinic, cancer immunotherapy still has room for improvement as many patients remain unresponsive to therapy. Moreover, many of the preclinical results obtained in the widely used mouse models of cancer are lost in translation to human patients. To improve the success rate of immuno-oncology research and preclinical testing of immune-based anticancer therapies, using alternative animal models more closely related to humans is a promising approach. Here, we describe 2 of the major alternative model systems: canine (spontaneous) and porcine (experimental) cancer models. Although dogs display a high rate of spontaneous tumor formation, an increased number of genetically modified porcine models exist. We suggest that the optimal immuno-oncology model may depend on the stage of cancer immunoediting in question. In particular, the spontaneous canine tumor models provide a unique platform for evaluating therapies aimed at the escape phase of cancer, while genetically engineered swine allow for elucidation of tumor-immune cell interactions especially during the phases of elimination and equilibrium.

Characterization of five newly derived canine osteosarcoma cell lines

BACKGROUND

Canine and human osteosarcomas (OS) are notably similar and have a high rate of metastasis. There is a poor understanding of the tumor development process, predisposing causes, and varying levels of aggression among different cell lines. By characterizing newly developed canine osteosarcoma cell lines, treatments for people and pets can be developed. Of the seven subtypes of OS, three are represented in this group: osteoblastic (the most common), fibroblastic, and giant cell variant. To our knowledge, there are no other giant cell variant canine OS cell lines in the published literature and only one canine fibroblastic osteosarcoma cell line. Understanding the differences between the histologic subtypes in dogs will help to guide comparative research.

RESULTS

Alkaline phosphatase expression was ubiquitous in all cell lines tested and invasiveness was variable between the cell lines tested. Invasiveness and oxidative damage were not correlated with in vivo growth rates, where TOT grew the fastest and had the higher percentage of mice with metastatic lesions. TOL was determined to be the most chemo-resistant during cisplatin chemotherapy while TOM was the most chemo-sensitive.

CONCLUSIONS

Further comparisons and studies using these cell lines may identify a variety of characteristics valuable for understanding the disease process and developing treatments for osteosarcoma in both species. Some of this data was presented as a poster by KMF at the August 5th, 2017 National Veterinary Scholars Program in Bethesda, MA. Characterization of 5 newly generated canine osteosarcoma cell lines. Kelli Franks, Tasha Miller, Heather Wilson-Robles.

Establishment and characterization of a novel human osteosarcoma cell line for spontaneous pulmonary metastasis research in vivo

Background

A large number of osteosarcoma patients are dying of pulmonary metastasis in spite of the recent progress achieved in treatment research. Therefore, there is an urgent need for an in vivo experiment, whose purpose is to investigate the growth and metastasis of human osteosarcoma tumor. In this study, a novel human osteosarcoma cell line was established and characterized for osteosarcoma metastatic research in vivo.

Methods

Small pieces of parental primary osteosarcoma samples from a 16-year-old boy were xeno-transplanted into NOD/SCID mice. Then, osteosarcoma cells from the xeno-grafts were isolated and further passaged in vitro. Expression profiling was confirmed using HE staining and immunohistochemistry. The tumorigenic and metastatic ability of the established cell line was analyzed by cell scratch and CCK8 assay in vitro, and tumor transplantation in NOD/SCID mice.

Results

Parental cells were pleomorphic and positive with ALP, SSEA-4, and CD44. Osteosarcoma cells, named Well5 cells, were successfully isolated and had the ability of adipogenesis and osteogenesis. Well5 cells were mostly positive for SSEA-4 protein, and possessed morphological characteristics such as osteoblastic nature during the cultivation and hetero transplantation. Cell scratch and CCK8 assay indicated Well5 cells obtained a better capacity for migration and proliferation than the MG63 cell line. In NOD/SCID mice, orthotopic tumors were established at the primary site, and spontaneous pulmonary metastases were developed.

Conclusions

A novel human osteosarcoma cell line was successfully established, which may be helpful for spontaneous pulmonary metastasis research in vivo.

Toward zonally tailored scaffolds for osteochondral differentiation of synovial mesenchymal stem cells

Synovium-derived mesenchymal stem cells (SMSCs) are an emerging cell source for regenerative medicine applications, including osteochondral defect (OCD) repair. However, in contrast to bone marrow MSCs, scaffold compositions which promote SMSC chondrogenesis/osteogenesis are still being identified. In the present manuscript, we examine poly(ethylene) glycol (PEG)-based scaffolds containing zonally-specific biochemical cues to guide SMSC osteochondral differentiation. Specifically, SMSCs were encapsulated in PEG-based scaffolds incorporating glycosaminoglycans (hyaluronan or chondroitin-6-sulfate [CSC]), low-dose of chondrogenic and osteogenic growth factors (TGFβ1 and BMP2, respectively), or osteoinductive poly(dimethylsiloxane) (PDMS). Initial studies suggested that PEG-CSC-TGFβ1 scaffolds promoted enhanced SMSC chondrogenic differentiation, as assessed by significant increases in Sox9 and aggrecan. Conversely, PEG-PDMS-BMP2 scaffolds stimulated increased levels of osteoblastic markers with significant mineral deposition. A "Transition" zone formulation was then developed containing a graded mixture of the chondrogenic and osteogenic signals present in the PEG-CSC-TGFβ1 and PEG-PDMS-BMP2 constructs. SMSCs within the "Transition" formulation displayed a phenotypic profile similar to hypertrophic chondrocytes, with the highest expression of collagen X, intermediate levels of osteopontin, and mineralization levels equivalent to "bone" formulations. Overall, these results suggest that a graded transition from PEG-CSC-TGFβ1 to PEG-PDMS-BMP2 scaffolds elicits a gradual SMSC phenotypic shift from chondrocyte to hypertrophic chondrocyte to osteoblast-like. As such, further development of these scaffold formulations for use in SMSC-based OCD repair is warranted. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2019-2029, 2019.

Personalized 3D-printed endoprostheses for limb sparing in dogs: Modeling and in vitro testing

Osteosarcoma is the most common type of bone cancer in dogs, treatable by amputation or limb-sparing surgery. For the latter, commercially available plate - endoprosthesis assemblies require contouring, to be adapted to the patient's bone geometry, and lead to sub-optimal results. The use of additively-manufactured personalized endoprostheses and cutting guides for distal radius limb-sparing surgery in dogs presents a promising alternative. Specialized software is used for the bone structure reconstruction from the patient's CT scans and for the design of endoprostheses and cutting guides. The prostheses are manufactured from a titanium alloy using a laser powder bed fusion system, while the cutting guides are manufactured from an ABS plastic using a fused deposition modeling system. A finite element model of an instrumented limb was developed and validated using experimental testing of a cadaveric limb implanted with a personalized endoprosthesis. Personalized endoprostheses and cutting guides can reduce limb sparing surgery time by 25-50% and may reduce the risk of implant failure. The numerical model was validated using the kinematics and force-displacement diagrams of the implant-limb construct. The model indicated that a modulus of elasticity of an implant material ranging from 25 to 50 GPa would improve the stress distribution within the implant. The results of the current study will allow optimization of the design of the personal implants in both veterinary and human patients.

YM155 enhances the cytotoxic activity of etoposide against canine osteosarcoma cells

Canine osteosarcoma (OSA) is an aggressive and highly malignant primary bone tumor. Its poor survival outcome remains problematic despite recent advances in anti-cancer therapy, therefore highlighting the need for alternative treatment options or drug repositioning. The aim of this study was to determine if YM155, a small-molecule survivin inhibitor, potentiates the chemotherapeutic efficacy of etoposide against canine OSA in vitro and in vivo. In cell culture, YM155 enhanced the cytotoxic effect of etoposide against canine OSA cell lines; however, the molecular mechanism behind this effect was heterogeneous, as only one cell line had an elevated apoptotic level. In addition, this effect was not associated with survivin suppression in two of the cell lines. These results suggest that the molecular target of YM155 is not restricted to survivin alone. When tested on a murine xenograft model, the average tumor volume of the combination treatment group (YM155, 5 mg/kg, intraperitoneally, 5 consecutive days/week; and etoposide, 20 mg/kg, intraperitoneally, every 5 days) was 66% smaller than the control group, although this difference was not statistically significant (P=0.17). Further studies to improve the treatment protocol are necessary to confirm the findings of this study.