A genome-wide approach to comparative oncology: high-resolution oligonucleotide aCGH of canine and human osteosarcoma pinpoints shared microaberrations

Cancer Immunotherapy

The enhanced understanding of immunology experienced over the last 5 decades afforded through the tools of molecular biology has recently translated into cancer immunotherapy becoming one of the most exciting and rapidly expanding fields. Human cancer immunotherapy is now recognized as one of the pillars of treatment alongside surgery, radiation, and chemotherapy. The field of veterinary cancer immunotherapy has also rapidly advanced in the last decade with a handful of commercially available products and a plethora of investigational cancer immunotherapies, which will hopefully expand our veterinary oncology treatment toolkit over time.

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.

The AGMK1-9T7 cell model of neoplasia: Evolution of DNA copy-number aberrations and miRNA expression during transition from normal to metastatic cancer cells

To study neoplasia in tissue culture, cell lines representing the evolution of normal cells to tumor cells are needed. To produce such cells, we developed the AGMK1-9T7 cell line, established cell banks at 10-passage intervals, and characterized their biological properties. Here we examine the evolution of chromosomal DNA copy-number aberrations and miRNA expression in this cell line from passage 1 to the acquisition of a tumorigenic phenotype at passage 40. We demonstrated the use of a human microarray platform for DNA copy-number profiling of AGMK1-9T7 cells using knowledge of synteny to 'recode' data from human chromosome coordinates to those of the African green monkey. This approach revealed the accumulation of DNA copy-number gains and losses in AGMK1-9T7 cells from passage 3 to passage 40, which spans the period in which neoplastic transformation occurred. These alterations occurred in the sequences of genes regulating DNA copy-number imbalance of several genes that regulate endothelial cell angiogenesis, survival, migration, and proliferation. Regarding miRNA expression, 195 miRNAs were up- or down-regulated at passage 1 at levels that appear to be biologically relevant (i.e., log2 fold change >2.0 (q<0.05)). At passage 10, the number of up/down-regulated miRNAs fell to 63; this number increased to 93 at passage 40. Principal-component analysis grouped these miRNAs into 3 clusters; miRNAs in sub-clusters of these groups could be correlated with initiation, promotion, and progression, stages that have been described for neoplastic development. Thirty-four of the AGMK1-9T7 miRNAs have been associated with these stages in human cancer. Based on these data, we propose that the evolution of AGMK1-9T7 cells represents a detailed model of neoplasia in vitro.

Transcriptomic Analysis of Conserved Telomere Maintenance Component 1 (CTC1) and Its Association with Leukemia

Telomere length (TEL) regulation is important for genome stability and is governed by the coordinated role of shelterin proteins, telomerase (TERT), and CST (CTC1/OBFC1/TEN1) complex. Previous studies have shown the association of telomerase expression with the risk of acute lymphoblastic leukemia (ALL). However, no data are available for CST association with the ALL. The current pilot study was designed to evaluate the CST expression levels in ALL. In total, 350 subjects were recruited, including 250 ALL cases and 100 controls. The subjects were stratified by age and categorized into pediatrics (1–18 years) and adults (19–54 years). TEL and expression patterns of CTC1, OBFC1, and TERT genes were determined by qPCR. The univariable logistic regression analysis was performed to determine the association of gene expression with ALL, and the results were adjusted for age and sex in multivariable analyses. Pediatric and adult cases did not reflect any change in telomere lengths relative to controls. However, expression of CTC1, OBFC1, and TERT genes were induced among ALL cases. Multivariable logistic regression analyses showed association of CTC1 with ALL in pediatric [β estimate (standard error (SE)= −0.013 (0.007), p = 0.049, and adults [0.053 (0.023), p = 0.025]. The association of CTC1 remained significant when taken together with OBFC1 and TERT in a multivariable model. Furthermore, CTC1 showed significant association with B-cell ALL [−0.057(0.017), p = 0.002) and T-cell ALL [−0.050 (0.018), p = 0.008] in pediatric group while no such association was noted in adults. Together, our findings demonstrated that telomere modulating genes, particularly CTC1, are strongly associated with ALL. Therefore, CTC1 can potentially be used as a risk biomarker for the identification of ALL in both pediatrics and adults.

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.

Functional analysis of the miR-145/Fascin1 cascade in canine oral squamous cell carcinoma

OBJECTIVES

Canine oral squamous cell carcinoma (SCC) often develops in the gingiva and tonsils. The biological behaviour of canine oral SCC is similar to that of human head and neck SCC (HNSCC). Inhibiting invasion and metastasis is major importance for the treatment of canine and human HNSCC. In this study, the significance of microRNA (miR)-145 and Fascin1 (FSCN1) in the invasion of canine oral SCC was explored.

MATERIALS AND METHODS

Canine oral SCC tissues and cell lines were used for miR-145 and FSCN1 expression analysis via real-time PCR and immunohistochemistry. Canine oral SCC cell lines were used for in vitro assays.

RESULTS

miR-145 was downregulated while FSCN1 mRNA was upregulated in canine oral SCC. Immunohistochemistry revealed that FSCN1 was upregulated in SCC when compared to normal mucosa. Transfection of canine SCC cells with miR-145 or FSCN1 siRNA suppressed cell growth and attenuated cell migration as well as invasion by inhibiting the epithelial-to-mesenchymal transition. Furthermore, the promoter region of miR-145 was highly methylated in SCC cell lines and tissues.

CONCLUSION

The expression profile and functions of miR-145 in canine oral SCC are similar to those in human HNSCC. Thus, canine oral SCC may represent a valuable preclinical model for human HNSCC.

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.

Adjuvant Sirolimus Does Not Improve Outcome in Pet Dogs Receiving Standard-of-Care Therapy for Appendicular Osteosarcoma: A Prospective, Randomized Trial of 324 Dogs

PURPOSE

The mTOR pathway has been identified as a key nutrient signaling hub that participates in metastatic progression of high-grade osteosarcoma. Inhibition of mTOR signaling is biologically achievable with sirolimus, and might slow the outgrowth of distant metastases. In this study, pet dogs with appendicular osteosarcoma were leveraged as high-value biologic models for pediatric osteosarcoma, to assess mTOR inhibition as a therapeutic strategy for attenuating metastatic disease progression.

PATIENTS AND METHODS

A total of 324 pet dogs diagnosed with treatment-naïve appendicular osteosarcoma were randomized into a two-arm, multicenter, parallel superiority trial whereby dogs received amputation of the affected limb, followed by adjuvant carboplatin chemotherapy ± oral sirolimus therapy. The primary outcome measure was disease-free interval (DFI), as assessed by serial physical and radiologic detection of emergent macroscopic metastases; secondary outcomes included overall 1- and 2-year survival rates, and sirolimus pharmacokinetic variables and their correlative relationship to adverse events and clinical outcomes.

RESULTS

There was no significant difference in the median DFI or overall survival between the two arms of this trial; the median DFI and survival for standard-of-care (SOC; defined as amputation and carboplatin therapy) dogs was 180 days [95% confidence interval (CI), 144-237] and 282 days (95% CI, 224-383) and for SOC + sirolimus dogs, it was 204 days (95% CI, 157-217) and 280 days (95% CI, 252-332), respectively.

CONCLUSIONS

In a population of pet dogs nongenomically segmented for predicted mTOR inhibition response, sequentially administered adjuvant sirolimus, although well tolerated when added to a backbone of therapy, did not extend DFI or survival in dogs with appendicular osteosarcoma.

Genomics and transcriptomics in veterinary oncology

The sequencing of the canine genome, combined with additional genomic technologies, has created opportunities for research linking veterinary genomics with naturally occurring cancer in dogs. Also, as numerous canine cancers have features in common with human cancers, comparative studies can be performed to evaluate the use of cancers in dogs as models for human cancer. There have been several reviews of veterinary genomics but, to the best of our knowledge, there has been no comprehensive review of the literature of canine cancer genomics. PubMed and CAB Abstracts databases were searched to retrieve relevant literature using the search terms ‘veterinary’, ‘cancer’ or ‘oncology’, and ‘genomics’ or ‘transcriptomics’. Results were manually assessed and grouped based on the techniques used, the cancer type investigated and genomic lesions targeted. The search resulted in the retrieval of 44 genomic and transcriptomic studies, with the most common technique employed being comparative genomic hybridization. Across both fields, the most commonly studied cancer type was canine osteosarcoma. Genomic and transcriptomic aberrations in canine cancer often reflected those reported in the corresponding human cancers. Analysis of the literature indicated that employing genomic and transcriptomic technologies has been instrumental in developing the understanding of the origin, development and pathogenesis of several canine cancers. However, their use in canine oncology is at an early phase, and there appears to be comparatively little understanding of certain canine cancer types in contrast to their human forms. Aberrations detected in all tumors were tabulated, and the results for osteosarcoma, lymphoma and leukemia, mast cell tumor, transmissible venereal tumor and urothelial carcinoma discussed in detail.

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.

Improving human cancer therapy through the evaluation of pet dogs

Comparative oncology clinical trials play an important and growing role in cancer research and drug development efforts. These trials, typically conducted in companion (pet) dogs, allow assessment of novel anticancer agents and combination therapies in a veterinary clinical setting that supports serial biologic sample collections and exploration of dose, schedule and corresponding pharmacokinetic/pharmacodynamic relationships. Further, an intact immune system and natural co-evolution of tumour and microenvironment support exploration of novel immunotherapeutic strategies. Substantial improvements in our collective understanding of the molecular landscape of canine cancers have occurred in the past 10 years, facilitating translational research and supporting the inclusion of comparative studies in drug development. The value of the approach is demonstrated in various clinical trial settings, including single-agent or combination response rates, inhibition of metastatic progression and randomized comparison of multiple agents in a head-to-head fashion. Such comparative oncology studies have been purposefully included in the developmental plan for several US FDA-approved and up-and-coming anticancer drugs. Challenges for this field include keeping pace with technology and data dissemination/harmonization, improving annotation of the canine genome and immune system, and generation of canine-specific validated reagents to support integration of correlative biology within clinical trial efforts.

A Comparative Oncology Drug Discovery Pipeline to Identify and Validate New Treatments for Osteosarcoma

Simple Summary

Osteosarcoma is a rare bone cancer that occurs primarily in children. The discovery of new treatments for osteosarcoma and other rare cancer types has been severely limited by access to patient samples to study these often-complex diseases. Here we capitalize on naturally-occurring cancers in pet dogs to study the biology of these rare cancers. Using living cells from canine and human patients to test thousands of drugs simultaneously, we identify a unique combination of drugs that disrupts protein degradation and protein trafficking in cancer cells. This drug combination represents a promising new treatment to treat both dogs and people with osteosarcoma.

Abstract

Background: Osteosarcoma is a rare but aggressive bone cancer that occurs primarily in children. Like other rare cancers, treatment advances for osteosarcoma have stagnated, with little improvement in survival for the past several decades. Developing new treatments has been hampered by extensive genomic heterogeneity and limited access to patient samples to study the biology of this complex disease. Methods: To overcome these barriers, we combined the power of comparative oncology with patient-derived models of cancer and high-throughput chemical screens in a cross-species drug discovery pipeline. Results: Coupling in vitro high-throughput drug screens on low-passage and established cell lines with in vivo validation in patient-derived xenografts we identify the proteasome and CRM1 nuclear export pathways as therapeutic sensitivities in osteosarcoma, with dual inhibition of these pathways inducing synergistic cytotoxicity. Conclusions: These collective efforts provide an experimental framework and set of new tools for osteosarcoma and other rare cancers to identify and study new therapeutic vulnerabilities.

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.

Emerging Translational Opportunities in Comparative Oncology With Companion Canine Cancers: Radiation Oncology

It is estimated that more than 6 million pet dogs are diagnosed with cancer annually in the USA. Both primary care and specialist veterinarians are frequently called upon to provide clinical care that improves the quality and/or quantity of life for affected animals. Because these cancers develop spontaneously in animals that often share the same environment as their owners, have intact immune systems and are of similar size to humans, and because the diagnostic tests and treatments for these cancers are similar to those used for management of human cancers, canine cancer provides an opportunity for research that simultaneously helps improve both canine and human health care. This is especially true in the field of radiation oncology, for which there is a rich and continually evolving history of learning from the careful study of pet dogs undergoing various forms of radiotherapy. The purpose of this review article is to inform readers of the potential utility and limitations of using dogs in that manner; the peer-reviewed literature will be critically reviewed, and current research efforts will be discussed. The article concludes with a look toward promising future directions and applications of this pet dog “model.”

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.

The interaction between RUNX2 and core binding factor beta as a potential therapeutic target in canine osteosarcoma

Osteosarcoma remains the most common primary bone tumour in dogs with half of affected dogs unable to survive 1 year beyond diagnosis. New therapeutic options are needed to improve outcomes for this disease. Recent investigations into potential therapeutic targets have focused on cell surface molecules with little clear therapeutic benefit. Transcription factors and protein interactions represent underdeveloped areas of therapeutic drug development. We have utilized allosteric inhibitors of the core binding factor transcriptional complex, comprised of core binding factor beta (CBFβ) and RUNX2, in four canine osteosarcoma cell lines Active inhibitor compounds demonstrate anti-tumour activities with concentrations demonstrated to be achievable in vivo while an inactive, structural analogue has no activity. We show that CBFβ inhibitors are capable of inducing apoptosis, inhibiting clonogenic cell growth, altering cell cycle progression and impeding migration and invasion in a cell line-dependent manner. These effects coincide with a reduced interaction between RUNX2 and CBFβ and alterations in expression of RUNX2 target genes. We also show that addition of CBFβ inhibitors to the commonly used cytotoxic chemotherapeutic drugs doxorubicin and carboplatin leads to additive and/or synergistic anti-proliferative effects in canine osteosarcoma cell lines. Taken together, we have identified the interaction between components of the core binding factor transcriptional complex, RUNX2 and CBFβ, as a potential novel therapeutic target in canine osteosarcoma and provide justification for further investigations into the anti-tumour activities we describe here.

Provocative questions in osteosarcoma basic and translational biology: A report from the Children's Oncology Group

Patients who are diagnosed with osteosarcoma (OS) today receive the same therapy that patients have received over the last 4 decades. Extensive efforts to identify more effective or less toxic regimens have proved disappointing. As we enter a postgenomic era in which we now recognize OS not as a cancer of mutations but as one defined by p53 loss, chromosomal complexity, copy number alteration, and profound heterogeneity, emerging threads of discovery leave many hopeful that an improving understanding of biology will drive discoveries that improve clinical care. Under the organization of the Bone Tumor Biology Committee of the Children's Oncology Group, a team of clinicians and scientists sought to define the state of the science and to identify questions that, if answered, have the greatest potential to drive fundamental clinical advances. Having discussed these questions in a series of meetings, each led by invited experts, we distilled these conversations into a series of seven Provocative Questions. These include questions about the molecular events that trigger oncogenesis, the genomic and epigenomic drivers of disease, the biology of lung metastasis, research models that best predict clinical outcomes, and processes for translating findings into clinical trials. Here, we briefly present each Provocative Question, review the current scientific evidence, note the immediate opportunities, and speculate on the impact that answered questions might have on the field. We do so with an intent to provide a framework around which investigators can build programs and collaborations to tackle the hardest problems and to establish research priorities for those developing policies and providing funding.

Canine osteosarcoma genome sequencing identifies recurrent mutations in DMD and the histone methyltransferase gene SETD2

Osteosarcoma (OS) is a rare, metastatic, human adolescent cancer that also occurs in pet dogs. To define the genomic underpinnings of canine OS, we performed multi-platform analysis of OS tumors from 59 dogs, including whole genome sequencing (n = 24) and whole exome sequencing (WES; n = 13) of primary tumors and matched normal tissue, WES (n = 10) of matched primary/metastatic/normal samples and RNA sequencing (n = 54) of primary tumors. We found that canine OS recapitulates features of human OS including low point mutation burden (median 1.98 per Mb) with a trend towards higher burden in metastases, high structural complexity, frequent TP53 (71%), PI3K pathway (37%), and MAPK pathway mutations (17%), and low expression of immune-associated genes. We also identified novel features of canine OS including putatively inactivating somatic SETD2 (42%) and DMD (50%) aberrations. These findings set the stage for understanding OS development in dogs and humans, and establish genomic contexts for future comparative analyses.

Cancer Immunotherapies

The enhanced understanding of immunology experienced over the last 4 decades afforded through the tools of molecular biology has recently translated into cancer immunotherapy becoming one of the most exciting and rapidly expanding fields. Human cancer immunotherapy is now recognized as one of the pillars of treatment alongside surgery, radiation, and chemotherapy. The field of veterinary cancer immunotherapy has also rapidly advanced in the last decade with a handful of commercially available products and a plethora of investigational cancer immunotherapies that will hopefully expand the veterinary oncology treatment toolkit over time.

Exploring the Potential Utility of Pet Dogs With Cancer for Studying Radiation-Induced Immunogenic Cell Death Strategies

Radiotherapy serves as a foundational pillar for the therapeutic management of diverse solid tumors through the generation of lethal DNA damage and induction of cell death. While the direct cytotoxic effects of radiation therapy remain a cornerstone for cancer management, in the era of immunooncology there is renewed and focused interest in exploiting the indirect bystander activities of radiation, termed abscopal effects. In radioimmunobiologic terms, abscopal effects describe the radiotherapy-induced regression of cancerous lesions distant from the primary site of radiation delivery and rely upon the induction of immunogenic cell death and consequent systemic anticancer immune activation. Despite the promise of radiation therapy for awaking potent anticancer immune responses, the purposeful harnessing of abscopal effects with radiotherapy remain clinically elusive. In part, failure to fully leverage and clinically implement the promise of radiation-induced abscopal effects stems from limitations associated with existing conventional tumor models which inadequately recapitulate the complexity of malignant transformation and the dynamic nature of tumor immune surveillance. To supplement this existing gap in modeling systems, pet dogs diagnosed with solid tumors including melanoma and osteosarcoma, which are both metastatic and immunogenic in nature, could potentially serve as unique resources for exploring the fundamental underpinnings required for maximizing radiation-induced abscopal effects. Given the spontaneous course of cancer development in the context of operative immune mechanisms, pet dogs treated with radiotherapy for metastatic solid tumors might be leveraged as valuable model systems for realizing the science and best clinical practices necessary to generate potent abscopal effects with anti-metastatic immune activities.

The cancer-related transcription factor RUNX2 modulates expression and secretion of the matricellular protein osteopontin in osteosarcoma cells to promote adhesion to endothelial pulmonary cells and lung metastasis

Osteosarcomas are bone tumors that frequently metastasize to the lung. Aberrant expression of the transcription factor, runt-related transcription factor 2 (RUNX2), is a key pathological feature in osteosarcoma and associated with loss of p53 and miR-34 expression. Elevated RUNX2 may transcriptionally activate genes mediating tumor progression and metastasis, including the RUNX2 target gene osteopontin (OPN/SPP1). This gene encodes a secreted matricellular protein produced by osteoblasts to regulate bone matrix remodeling and tissue calcification. Here we investigated whether and how the RUNX2/OPN axis regulates lung metastasis of osteosarcoma. Importantly, RUNX2 depletion attenuates lung metastasis of osteosarcoma cells in vivo. Using next-generation RNA-sequencing, protein-based assays, as well as the loss- and gain-of-function approaches in selected osteosarcoma cell lines, we show that osteopontin messenger RNA levels closely correlate with RUNX2 expression and that RUNX2 controls the levels of secreted osteopontin. Elevated osteopontin levels promote heterotypic cell-cell adhesion of osteosarcoma cells to human pulmonary microvascular endothelial cells, but not in the presence of neutralizing antibodies. Collectively, these findings indicate that the RUNX2/OPN axis regulates the ability of osteosarcoma cells to attach to pulmonary endothelial cells as a key step in metastasis of osteosarcoma cells to the lung.

A genetically engineered microRNA-34a prodrug demonstrates anti-tumor activity in a canine model of osteosarcoma

Osteosarcoma (OSA) represents the most common primary bone tumor in humans and pet dogs. Little progress has been made with regard to viable treatment options in the past three decades and patients presenting with metastatic disease continue to have a poor prognosis. Recent mouse studies have suggested that microRNA-34a (miR-34a) may have anti-tumor activities in human OSA models. Due to the conservation of microRNA across species, we hypothesized that a bioengineered miR-34a prodrug (tRNA/miR-34a) would have similar effects in canine OSA, providing a valuable preclinical model for development of this therapeutic modality. Using a panel of canine OSA cell lines, we found that tRNA/miR-34a reduced viability, clonogenic growth, and migration and invasion while increasing tumor cell apoptosis. Furthermore, canine OSA cells successfully process the tRNA/miR-34a into mature miR-34a which reduces expression of target proteins such as platelet derived growth factor receptor alpha (PDGFRα), Notch1 and vascular endothelial growth factor (VEGF). Additionally, our subcutaneous OSA xenograft model demonstrated in vivo tumor growth delay, increased necrosis and apoptosis by tRNA/miR-34a, and decreased cellular proliferation ability. Taken together, these data support that this novel microRNA-based therapy may possess clinical utility in a spontaneously-occurring large animal model of OSA, which can then serve to inform the clinical development of this therapy for human OSA patients.

Somatic inactivating PTPRJ mutations and dysregulated pathways identified in canine malignant melanoma by integrated comparative genomic analysis

Canine malignant melanoma, a significant cause of mortality in domestic dogs, is a powerful comparative model for human melanoma, but little is known about its genetic etiology. We mapped the genomic landscape of canine melanoma through multi-platform analysis of 37 tumors (31 mucosal, 3 acral, 2 cutaneous, and 1 uveal) and 17 matching constitutional samples including long- and short-insert whole genome sequencing, RNA sequencing, array comparative genomic hybridization, single nucleotide polymorphism array, and targeted Sanger sequencing analyses. We identified novel predominantly truncating mutations in the putative tumor suppressor gene PTPRJ in 19% of cases. No BRAF mutations were detected, but activating RAS mutations (24% of cases) occurred in conserved hotspots in all cutaneous and acral and 13% of mucosal subtypes. MDM2 amplifications (24%) and TP53 mutations (19%) were mutually exclusive. Additional low-frequency recurrent alterations were observed amidst low point mutation rates, an absence of ultraviolet light mutational signatures, and an abundance of copy number and structural alterations. Mutations that modulate cell proliferation and cell cycle control were common and highlight therapeutic axes such as MEK and MDM2 inhibition. This mutational landscape resembles that seen in BRAF wild-type and sun-shielded human melanoma subtypes. Overall, these data inform biological comparisons between canine and human melanoma while suggesting actionable targets in both species.

Cross-species genomics identifies DLG2 as a tumor suppressor in osteosarcoma

Leveraging the conserved cancer genomes across mammals has the potential to transform driver gene discovery in orphan cancers. Here, we combine cross-species genomics with validation across human–dog–mouse systems to uncover a new bone tumor suppressor gene. Comparative genomics of spontaneous human and dog osteosarcomas (OS) expose Disks Large Homolog 2 (DLG2) as a tumor suppressor candidate. DLG2 copy number loss occurs in 42% of human and 56% of canine OS. Functional validation through pertinent human and canine OS DLG2-deficient cell lines identifies a regulatory role of DLG2 in cell division, migration and tumorigenesis. Moreover, osteoblast-specific deletion of Dlg2 in a clinically relevant genetically engineered mouse model leads to acceleration of OS development, establishing DLG2 as a critical determinant of OS. This widely applicable cross-species approach serves as a platform to expedite the search of cancer drivers in rare human malignancies, offering new targets for cancer therapy.

Canine sarcomas as a surrogate for the human disease

Pet dogs are becoming increasingly recognized as a population with the potential to inform medical research through their treatment for a variety of maladies by veterinary health professionals. This is the basis of the One Health initiative, supporting the idea of collaboration between human and animal health researchers and clinicians to study spontaneous disease processes and treatment in animals to inform human health. Cancer is a major health burden in pet dogs, accounting for approximately 30% of deaths across breeds. As such, pet dogs with cancer are becoming increasingly recognized as a resource for studying the pharmacology and therapeutic potential of anticancer drugs and therapies under development. This was recently highlighted by a National Academy of Medicine Workshop on Comparative Oncology that took place in mid-2015 (http://www.nap.edu/21830). One component of cancer burden in dogs is their significantly higher incidence of sarcomas as compared to humans. This increased incidence led to canine osteosarcoma being an important component in the development of surgical approaches for osteosarcoma in children. Included in this review of sarcomas in dogs is a description of the incidence, pathology, molecular characteristics and previous translational therapeutic studies associated with these tumors. An understanding of the patho-physiological and molecular characteristics of these naturally occurring canine sarcomas holds great promise for effective incorporation into drug development schemas, for evaluation of target modulation or other pharmacodynamic measures associated with therapeutic response. These data could serve to supplement other preclinical data and bolster clinical investigations in tumor types for which there is a paucity of human patients for clinical trials.

From humans to hydra: patterns of cancer across the tree of life

Cancer is a disease of multicellularity; it originates when cells become dysregulated due to mutations and grow out of control, invading other tissues and provoking discomfort, disability, and eventually death. Human life expectancy has greatly increased in the last two centuries, and consequently so has the incidence of cancer. However, how cancer patterns in humans compare to those of other species remains largely unknown. In this review, we search for clues about cancer and its evolutionary underpinnings across the tree of life. We discuss data from a wide range of species, drawing comparisons with humans when adequate, and interpret our findings from an evolutionary perspective. We conclude that certain cancers are uniquely common in humans, such as lung, prostate, and testicular cancer; while others are common across many species. Lymphomas appear in almost every animal analysed, including in young animals, which may be related to pathogens imposing selection on the immune system. Cancers unique to humans may be due to our modern environment or may be evolutionary accidents: random events in the evolution of our species. Finally, we find that cancer‐resistant animals such as whales and mole‐rats have evolved cellular mechanisms that help them avoid neoplasia, and we argue that there are multiple natural routes to cancer resistance.

Emerging roles of CST in maintaining genome stability and human disease

The human CTC1-STN1-TEN1 (CST) complex is a single-stranded DNA binding protein that shares homology with RPA and interacts with DNA polymerase alpha/primase. CST complexes are conserved from yeasts to humans and function in telomere maintenance. A common role of CST across species is in the regulation of telomere extension by telomerase and C-strand fill-in synthesis. However, recent studies also indicate that CST promotes telomere duplex replication as well the rescue of stalled DNA replication at non-telomeric sites. Furthermore, CST dysfunction and mutation is associated with several genetic diseases and cancers. In this review, we will summarize what is known about CST with a particular focus on the emerging roles of CST in DNA replication and human disease.

Comparative oncology: Integrating human and veterinary medicine

Cancer constitutes the major health problem both in human and veterinary medicine. Comparative oncology as an integrative approach offers to learn more about naturally occurring cancers across different species. Canine models have many advantages as they experience spontaneous disease, have many genes similar to human genes, five to seven-fold accelerated ageing compared to humans, respond to treatments similarly as humans do and health care levels second only to humans. Also, the clinical trials in canines could generate more robust data, as their spontaneous nature mimics real-life situations and could be translated to humans.

Osteosarcoma: Accelerating Progress Makes for a Hopeful Future

Patients who develop osteosarcoma in 2017 receive treatment that remains essentially unchanged since the 1970s. Outcomes likewise remain largely unimproved. Large, collaborative, multinational efforts to improve therapy have evaluated strategies leveraging both cytotoxic intensification and immunomodulatory agents. While these have confirmed our capacity to conduct such trials, results have proved largely disappointing. This has motivated efforts to focus on the basic biology of osteosarcoma, where understanding remains poor but has improved significantly. Recent advances have identified characteristic genetic features of osteosarcoma, including profound chromosomal disruption, marked patient-patient heterogeneity, and a paucity of recurrent mutations. Analyses suggest genesis in early catastrophic genetic events, although the nature of the inciting events remains unclear. While p53 and Rb inactivation occurs in most osteosarcomas, the landscape of associated driver mutations has proved extensive. Few mutations recur with high frequency, though patterns continue to emerge that suggest recurrent alterations within specific pathways. Biological pathways implicated in osteosarcoma biology through genetic and other preclinical studies include PI3K/mTOR, WNT/βcatenin, TGFβ, RANKL/NF-κB, and IGF. Unfortunately, clinical studies evaluating targeted agents have to date yielded disappointing results, as have studies examining modern immunotherapeutics. It remains unclear whether this pattern of clinical failures exposes inadequacies of our preclinical models, unrealistic expectations for single-agent responses in heavily pretreated patients, or biology less relevant than suggested. Nearly all patients who succumb to osteosarcoma develop lung metastases, which exhibit marked chemoresistance. Much scientific effort has recently sought to enhance our mechanistic understanding of metastasis biology. This research has potential to reveal novel targets for preventing and treating metastasis and for uncovering key vulnerabilities of osteosarcoma cells. Efforts to implement drug development strategies that leverage clinical studies in veterinary patients have potential to accelerate the translation of novel experimental regimens toward human studies. These could reduce costs and development timelines, prioritize agents, and refine regimens prior to human clinical trials. The rise of philanthropic groups focused on osteosarcoma has enhanced cross-disciplinary and cross-institutional focus and provided much needed resources. Transformative new therapies will likely arise from collaborative, interdisciplinary efforts that extend our understanding of osteosarcoma's most basic inner workings.

MiR-34a regulates the invasive capacity of canine osteosarcoma cell lines

BACKGROUND

Osteosarcoma (OSA) is the most common bone tumor in children and dogs; however, no substantial improvement in clinical outcome has occurred in either species over the past 30 years. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression and play a fundamental role in cancer. The purpose of this study was to investigate the potential contribution of miR-34a loss to the biology of canine OSA, a well-established spontaneous model of the human disease.

METHODOLOGY AND PRINCIPAL FINDINGS

RT-qPCR demonstrated that miR-34a expression levels were significantly reduced in primary canine OSA tumors and canine OSA cell lines as compared to normal canine osteoblasts. In canine OSA cell lines stably transduced with empty vector or pre-miR-34a lentiviral constructs, overexpression of miR-34a inhibited cellular invasion and migration but had no effect on cell proliferation or cell cycle distribution. Transcriptional profiling of canine OSA8 cells possessing enforced miR-34a expression demonstrated dysregulation of numerous genes, including significant down-regulation of multiple putative targets of miR-34a. Moreover, gene ontology analysis of down-regulated miR-34a target genes showed enrichment of several biological processes related to cell invasion and motility. Lastly, we validated changes in miR-34a putative target gene expression, including decreased expression of KLF4, SEM3A, and VEGFA transcripts in canine OSA cells overexpressing miR-34a and identified KLF4 and VEGFA as direct target genes of miR-34a. Concordant with these data, primary canine OSA tumor tissues demonstrated increased expression levels of putative miR-34a target genes.

CONCLUSIONS

These data demonstrate that miR-34a contributes to invasion and migration in canine OSA cells and suggest that loss of miR-34a may promote a pattern of gene expression contributing to the metastatic phenotype in canine OSA.

Comparative Transcriptome Analysis Quantifies Immune Cell Transcript Levels, Metastatic Progression, and Survival in Osteosarcoma

Overall survival of patients with osteosarcoma (OS) has improved little in the past three decades, and better models for study are needed. OS is common in large dog breeds and is genetically inducible in mice, making the disease ideal for comparative genomic analyses across species. Understanding the level of conservation of intertumor transcriptional variation across species and how it is associated with progression to metastasis will enable us to more efficiently develop effective strategies to manage OS and to improve therapy. In this study, transcriptional profiles of OS tumors and cell lines derived from humans (n = 49), mice (n = 103), and dogs (n = 34) were generated using RNA sequencing. Conserved intertumor transcriptional variation was present in tumor sets from all three species and comprised gene clusters associated with cell cycle and mitosis and with the presence or absence of immune cells. Further, we developed a novel gene cluster expression summary score (GCESS) to quantify intertumor transcriptional variation and demonstrated that these GCESS values associated with patient outcome. Human OS tumors with GCESS values suggesting decreased immune cell presence were associated with metastasis and poor survival. We validated these results in an independent human OS tumor cohort and in 15 different tumor data sets obtained from The Cancer Genome Atlas. Our results suggest that quantification of immune cell absence and tumor cell proliferation may better inform therapeutic decisions and improve overall survival for OS patients.Significance: This study offers new tools to quantify tumor heterogeneity in osteosarcoma, identifying potentially useful prognostic biomarkers for metastatic progression and survival in patients. Cancer Res; 78(2); 326-37. ©2017 AACR.

Genetic and epigenetic aberrations of p16 in feline primary neoplastic diseases and tumor cell lines of lymphoid and non-lymphoid origins

The p16 gene acts as a tumor suppressor by regulating the cell cycle and is frequently inactivated in human and canine cancers. The aim of this study was to characterize genetic and epigenetic alterations of the p16 in feline lymphoid and non-lymphoid malignancies, using 74 primary tumors and 11 tumor cell lines. Cloning of feline p16 and subsequent sequence analysis revealed 11 germline sequence polymorphisms in control cats. Bisulfite sequencing analysis of the p16 promoter region in a feline lymphoma cell line revealed that promoter methylation was associated with decreased mRNA expression. Treatment with a demethylating agent restored mRNA expression of the silenced p16. PCR amplification and sequencing analysis detected homozygous loss (five tumors, 6.7%) and a missense mutation (one tumor, 1.4%) in the 74 primary tumors analyzed. Methylation-specific PCR analysis revealed promoter methylation in 10 primary tumors (14%). Promoter methylation was frequent in B cell lymphoid tumors (7/21 tumors, 33%). These genetic and epigenetic alterations were also observed in lymphoma and mammary gland carcinoma cell lines, but not detected in non-neoplastic control specimens. These data indicate that molecular alterations of the p16 locus may be involved in the development of specific types of feline cancer, and warrant further studies to evaluate the clinical value of this evolutionarily-conserved molecular alteration in feline cancers.

MiR-9 is overexpressed in spontaneous canine osteosarcoma and promotes a metastatic phenotype including invasion and migration in osteoblasts and osteosarcoma cell lines

Background

MicroRNAs (miRNAs) regulate the expression of networks of genes and their dysregulation is well documented in human malignancies; however, limited information exists regarding the impact of miRNAs on the development and progression of osteosarcoma (OS). Canine OS exhibits clinical and molecular features that closely resemble the corresponding human disease and it is considered a well-established spontaneous animal model to study OS biology. The purpose of this study was to investigate miRNA dysregulation in canine OS.

Methods

We evaluated miRNA expression in primary canine OS tumors and normal canine osteoblast cells using the nanoString nCounter system. Quantitative PCR was used to validate the nanoString findings and to assess miR-9 expression in canine OS tumors, OS cell lines, and normal osteoblasts. Canine osteoblasts and OS cell lines were stably transduced with pre-miR-9 or anti-miR-9 lentiviral constructs to determine the consequences of miR-9 on cell proliferation, apoptosis, invasion and migration. Proteomic and gene expression profiling of normal canine osteoblasts with enforced miR-9 expression was performed using 2D-DIGE/tandem mass spectrometry and RNA sequencing and changes in protein and mRNA expression were validated with Western blotting and quantitative PCR. OS cell lines were transduced with gelsolin (GSN) shRNAs to investigate the impact of GSN knockdown on OS cell invasion.

Results

We identified a unique miRNA signature associated with primary canine OS and identified miR-9 as being significantly overexpressed in canine OS tumors and cell lines compared to normal osteoblasts. Additionally, high miR-9 expression was demonstrated in tumor-specific tissue obtained from primary OS tumors. In normal osteoblasts and OS cell lines transduced with miR-9 lentivirus, enhanced invasion and migration were observed, but miR-9 did not affect cell proliferation or apoptosis. Proteomic and transcriptional profiling of normal canine osteoblasts overexpressing miR-9 identified alterations in numerous genes, including upregulation of GSN, an actin filament-severing protein involved in cytoskeletal remodeling. Lastly, stable downregulation of miR-9 in OS cell lines reduced GSN expression with a concomitant decrease in cell invasion and migration; concordantly, cells transduced with GSN shRNA demonstrated decreased invasive properties.

Conclusions

Our findings demonstrate that miR-9 promotes a metastatic phenotype in normal canine osteoblasts and malignant OS cell lines, and that this is mediated in part by enhanced GSN expression. As such, miR-9 represents a novel target for therapeutic intervention in OS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2837-5) contains supplementary material, which is available to authorized users.

Pamidronate functionalized nanoconjugates for targeted therapy of focal skeletal malignant osteolysis

Malignant osteolysis associated with inoperable primary bone tumors and multifocal skeletal metastases remains a challenging clinical problem in cancer patients. Nanomedicine that is able to target and deliver therapeutic agents to diseased bone sites could potentially provide an effective treatment option for different types of skeletal cancers. Here, we report the development of polylactide nanoparticles (NPs) loaded with doxorubicin (Doxo) and coated with bone-seeking pamidronate (Pam) for the targeted treatment of malignant skeletal tumors. In vivo biodistribution of radiolabeled targeted Pam-NPs demonstrated enhanced bone tumor accumulation and prolonged retention compared with nontargeted NPs. In a murine model of focal malignant osteolysis, Pam-functionalized, Doxo-loaded NPs (Pam-Doxo-NPs) significantly attenuated localized osteosarcoma (OS) progression compared with nontargeted Doxo-NPs. Importantly, we report on the first evaluation to our knowlege of Pam-Doxo-NPs in dogs with OS, which possess tumors of anatomic size and physiology comparable to those in humans. The repeat dosing of Pam-Doxo-NPs in dogs with naturally occurring OS indicated the therapeutic was well tolerated without hematologic, nonhematologic, and cardiac toxicities. By nuclear scintigraphy, the biodistribution of Pam-Doxo-NPs demonstrated malignant bone-targeting capability and exerted measurable anticancer activities as confirmed with percent tumor necrosis histopathology assessment.

Comparative oncology: what dogs and other species can teach us about humans with cancer

Over 1.66 million humans (approx. 500/100,000 population rate) and over 4.2 million dogs (approx. 5300/100,000 population rate) are diagnosed with cancer annually in the USA. The interdisciplinary field of comparative oncology offers a unique and strong opportunity to learn more about universal cancer risk and development through epidemiology, genetic and genomic investigations. Working across species, researchers from human and veterinary medicine can combine scientific findings to understand more quickly the origins of cancer and translate these findings to novel therapies to benefit both human and animals. This review begins with the genetic origins of canines and their advantage in cancer research. We next focus on recent findings in comparative oncology related to inherited, or genetic, risk for tumour development. We then detail the somatic, or genomic, changes within tumours and the similarities between species. The shared cancers between humans and dogs that we discuss include sarcoma (osteosarcoma, soft tissue sarcoma, histiocytic sarcoma, hemangiosarcoma), haematological malignancies (lymphoma, leukaemia), bladder cancer, intracranial neoplasms (meningioma, glioma) and melanoma. Tumour risk in other animal species is also briefly discussed. As the field of genomics advances, we predict that comparative oncology will continue to benefit both humans and the animals that live among us.

Understanding the Osteosarcoma Pathobiology: A Comparative Oncology Approach

Osteosarcoma is an aggressive primary bone tumor in humans and is among the most common cancer afflicting dogs. Despite surgical advancements and intensification of chemo- and targeted therapies, the survival outcome for osteosarcoma patients is, as of yet, suboptimal. The presence of metastatic disease at diagnosis or its recurrence after initial therapy is a major factor for the poor outcomes. It is thought that most human and canine patients have at least microscopic metastatic lesions at diagnosis. Osteosarcoma in dogs occurs naturally with greater frequency and shares many biological and clinical similarities with osteosarcoma in humans. From a genetic perspective, osteosarcoma in both humans and dogs is characterized by complex karyotypes with highly variable structural and numerical chromosomal aberrations. Similar molecular abnormalities have been observed in human and canine osteosarcoma. For instance, loss of TP53 and RB regulated pathways are common. While there are several oncogenes that are commonly amplified in both humans and dogs, such as MYC and RAS, no commonly activated proto-oncogene has been identified that could form the basis for targeted therapies. It remains possible that recurrent aberrant gene expression changes due to gene amplification or epigenetic alterations could be uncovered and these could be used for developing new, targeted therapies. However, the remarkably high genomic complexity of osteosarcoma has precluded their definitive identification. Several advantageous murine models of osteosarcoma have been generated. These include spontaneous and genetically engineered mouse models, including a model based on forward genetics and transposon mutagenesis allowing new genes and genetic pathways to be implicated in osteosarcoma development. The proposition of this review is that careful comparative genomic studies between human, canine and mouse models of osteosarcoma may help identify commonly affected and targetable pathways for alternative therapies for osteosarcoma patients. Translational research may be found through a path that begins in mouse models, and then moves through canine patients, and then human patients.

Human CST abundance determines recovery from diverse forms of DNA damage and replication stress

Mammalian CST (CTC1-STN1-TEN1) is a telomere-associated complex that functions in telomere duplex replication and fill-in synthesis of the telomeric C-strand following telomerase action. CST also facilitates genome-wide replication recovery after HU-induced fork stalling by increasing origin firing. CTC1 and STN1 were originally isolated as a DNA polymerase α stimulatory factor. Here we explore how CST abundance affects recovery from drugs that cause different types of DNA damage and replication stress. We show that recovery from HU and aphidicolin induced replication stress is increased by CST over-expression. Elevated CST increases dNTP incorporation and origin firing after HU release and decreases the incidence of anaphase bridges and micronuclei after aphidicolin removal. While the frequency of origin firing after HU release is proportional to CST abundance, the number of cells entering S-phase to initiate replication is unchanged by CST overexpression or STN1 depletion. Instead the CST-related changes in origin firing take place in cells that were already in S-phase at the time of HU addition, indicating that CST modulates firing of late or dormant origins. CST abundance also influences cell viability after treatment with HU, aphidicolin, MMS and camptothecin. Viability is increased by elevated CST and decreased by STN1 depletion, indicating that endogenous CST levels are limiting. However, CST abundance does not affect viability after MMC treatment. Thus, CST facilitates recovery from many, but not all, forms of exogenous DNA damage. Overall our results suggest that CST is needed in stoichiometric amounts to facilitate re-initiation of DNA replication at repaired forks and/or dormant origins.

Comparative Aspects of Osteosarcoma Pathogenesis in Humans and Dogs

Osteosarcoma (OS) is a primary and aggressive bone sarcoma affecting the skeleton of two principal species, human beings and canines. The biologic behavior of OS is conserved between people and dogs, and evidence suggests that fundamental discoveries in OS biology can be facilitated through detailed and comparative studies. In particular, the relative genetic homogeneity associated with specific dog breeds can provide opportunities to facilitate the discovery of key genetic drivers involved in OS pathogenesis, which, to-date, remain elusive. In this review, known causative factors that predispose to the development OS in human beings and dogs are summarized in detail. Based upon the commonalities shared in OS pathogenesis, it is likely that foundational discoveries in one species will be translationally relevant to the other and emphasizes the unique opportunities that might be gained through comparative scientific approaches.

Genome-wide assessment of recurrent genomic imbalances in canine leukemia identifies evolutionarily conserved regions for subtype differentiation

Leukemia in dogs is a heterogeneous disease with survival ranging from days to years, depending on the subtype. Strides have been made in both human and canine leukemia to improve classification and understanding of pathogenesis through immunophenotyping, yet classification and choosing appropriate therapy remains challenging. In this study, we assessed 123 cases of canine leukemia (28 ALLs, 24 AMLs, 25 B-CLLs, and 46 T-CLLs) using high-resolution oligonucleotide array comparative genomic hybridization (oaCGH) to detect DNA copy number alterations (CNAs). For the first time, such data were used to identify recurrent CNAs and inclusive genes that may be potential drivers of subtype-specific pathogenesis. We performed predictive modeling to identify CNAs that could reliably differentiate acute subtypes (ALL vs. AML) and chronic subtypes (B-CLL vs. T-CLL) and used this model to differentiate cases with up to 83.3 and 95.8 % precision, respectively, based on CNAs at only one to three genomic regions. In addition, CGH datasets for canine and human leukemia were compared to reveal evolutionarily conserved copy number changes between species, including the shared gain of HSA 21q in ALL and ∼25 Mb of shared gain of HSA 12 and loss of HSA 13q14 in CLL. These findings support the use of canine leukemia as a relevant in vivo model for human leukemia and justify the need to further explore the conserved genomic regions of interest for their clinical impact.

Comparative cytogenetic characterization of primary canine melanocytic lesions using array CGH and fluorescence in situ hybridization

Melanocytic lesions originating from the oral mucosa or cutaneous epithelium are common in the general dog population, with up to 100,000 diagnoses each year in the USA. Oral melanoma is the most frequent canine neoplasm of the oral cavity, exhibiting a highly aggressive course. Cutaneous melanocytomas occur frequently, but rarely develop into a malignant form. Despite the differential prognosis, it has been assumed that subtypes of melanocytic lesions represent the same disease. To address the relative paucity of information about their genomic status, molecular cytogenetic analysis was performed on the three recognized subtypes of canine melanocytic lesions. Using array comparative genomic hybridization (aCGH) analysis, highly aberrant distinct copy number status across the tumor genome for both of the malignant melanoma subtypes was revealed. The most frequent aberrations included gain of dog chromosome (CFA) 13 and 17 and loss of CFA 22. Melanocytomas possessed fewer genome wide aberrations, yet showed a recurrent gain of CFA 20q15.3-17. A distinctive copy number profile, evident only in oral melanomas, displayed a sigmoidal pattern of copy number loss followed immediately by a gain, around CFA 30q14. Moreover, when assessed by fluorescence in situ hybridization (FISH), copy number aberrations of targeted genes, such as gain of c-MYC (80 % of cases) and loss of CDKN2A (68 % of cases), were observed. This study suggests that in concordance with what is known for human melanomas, canine melanomas of the oral mucosa and cutaneous epithelium are discrete and initiated by different molecular pathways.

Canine spontaneous head and neck squamous cell carcinomas represent their human counterparts at the molecular level

Spontaneous canine head and neck squamous cell carcinoma (HNSCC) represents an excellent model of human HNSCC but is greatly understudied. To better understand and utilize this valuable resource, we performed a pilot study that represents its first genome-wide characterization by investigating 12 canine HNSCC cases, of which 9 are oral, via high density array comparative genomic hybridization and RNA-seq. The analyses reveal that these canine cancers recapitulate many molecular features of human HNSCC. These include analogous genomic copy number abnormality landscapes and sequence mutation patterns, recurrent alteration of known HNSCC genes and pathways (e.g., cell cycle, PI3K/AKT signaling), and comparably extensive heterogeneity. Amplification or overexpression of protein kinase genes, matrix metalloproteinase genes, and epithelial-mesenchymal transition genes TWIST1 and SNAI1 are also prominent in these canine tumors. This pilot study, along with a rapidly growing body of literature on canine cancer, reemphasizes the potential value of spontaneous canine cancers in HNSCC basic and translational research.

Genomic heterogeneity of osteosarcoma - shift from single candidates to functional modules

Osteosarcoma (OS), a bone tumor, exhibit a complex karyotype. On the genomic level a highly variable degree of alterations in nearly all chromosomal regions and between individual tumors is observable. This hampers the identification of common drivers in OS biology. To identify the common molecular mechanisms involved in the maintenance of OS, we follow the hypothesis that all the copy number-associated differences between the patients are intercepted on the level of the functional modules. The implementation is based on a network approach utilizing copy number associated genes in OS, paired expression data and protein interaction data. The resulting functional modules of tightly connected genes were interpreted regarding their biological functions in OS and their potential prognostic significance. We identified an osteosarcoma network assembling well-known and lesser-known candidates. The derived network shows a significant connectivity and modularity suggesting that the genes affected by the heterogeneous genetic alterations share the same biological context. The network modules participate in several critical aspects of cancer biology like DNA damage response, cell growth, and cell motility which is in line with the hypothesis of specifically deregulated but functional modules in cancer. Further, we could deduce genes with possible prognostic significance in OS for further investigation (e.g. EZR, CDKN2A, MAP3K5). Several of those module genes were located on chromosome 6q. The given systems biological approach provides evidence that heterogeneity on the genomic and expression level is ordered by the biological system on the level of the functional modules. Different genomic aberrations are pointing to the same cellular network vicinity to form vital, but already neoplastically altered, functional modules maintaining OS. This observation, exemplarily now shown for OS, has been under discussion already for a longer time, but often in a hypothetical manner, and can here be exemplified for OS.

Canine urothelial carcinoma: genomically aberrant and comparatively relevant

Urothelial carcinoma (UC), also referred to as transitional cell carcinoma (TCC), is the most common bladder malignancy in both human and canine populations. In human UC, numerous studies have demonstrated the prevalence of chromosomal imbalances. Although the histopathology of the disease is similar in both species, studies evaluating the genomic profile of canine UC are lacking, limiting the discovery of key comparative molecular markers associated with driving UC pathogenesis. In the present study, we evaluated 31 primary canine UC biopsies by oligonucleotide array comparative genomic hybridization (oaCGH). Results highlighted the presence of three highly recurrent numerical aberrations: gain of dog chromosome (CFA) 13 and 36 and loss of CFA 19. Regional gains of CFA 13 and 36 were present in 97 % and 84 % of cases, respectively, and losses on CFA 19 were present in 77 % of cases. Fluorescence in situ hybridization (FISH), using targeted bacterial artificial chromosome (BAC) clones and custom Agilent SureFISH probes, was performed to detect and quantify these regions in paraffin-embedded biopsy sections and urine-derived urothelial cells. The data indicate that these three aberrations are potentially diagnostic of UC. Comparison of our canine oaCGH data with that of 285 human cases identified a series of shared copy number aberrations. Using an informatics approach to interrogate the frequency of copy number aberrations across both species, we identified those that had the highest joint probability of association with UC. The most significant joint region contained the gene PABPC1, which should be considered further for its role in UC progression. In addition, cross-species filtering of genome-wide copy number data highlighted several genes as high-profile candidates for further analysis, including CDKN2A, S100A8/9, and LRP1B. We propose that these common aberrations are indicative of an evolutionarily conserved mechanism of pathogenesis and harbor genes key to urothelial neoplasia, warranting investigation for diagnostic, prognostic, and therapeutic applications.

Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology

Osteosarcoma (OSA) is the most common form of malignant bone cancer in children and dogs, although the disease occurs in dogs approximately 10 times more frequently than in people. Multidrug chemotherapy and aggressive surgical techniques have improved survival; however, new therapies for OSA are critical, as little improvement in survival times has been achieved in either dogs or people over the past 15 years, even with significant efforts directed at the incorporation of novel therapeutic approaches. Both clinical and molecular evidence suggests that human and canine OSA share many key features, including tumor location, presence of microscopic metastatic disease at diagnosis, development of chemotherapy-resistant metastases, and altered expression/activation of several proteins (e.g. Met, ezrin, phosphatase and tensin homolog, signal transducer and activator of transcription 3), and p53 mutations, among others. Additionally, canine and pediatric OSA exhibit overlapping transcriptional profiles and shared DNA copy number aberrations, supporting the notion that these diseases are similar at the molecular level. This review will discuss the similarities between pediatric and canine OSA with regard to histology, biologic behavior, and molecular genetic alterations that indicate canine OSA is a relevant, spontaneous, large animal model of the pediatric disease and outline how the study of naturally occurring OSA in dogs will offer additional insights into the biology and future treatment of this disease in both children and dogs.

The importance of comparative oncology in translational medicine

Human cancer is so complex that in vivo preclinical models are needed if effective therapies are to be developed. Naturally occurring cancers in companion animals are therefore a great resource, as shown by the remarkable growth that comparative oncology has seen over the last 30 years. Cancer has become a leading cause of death in companion animals now that more pets are living long enough to develop the disease. Furthermore, more owners are seeking advanced and novel therapies for their pets as they are very much considered family members. Living in the same environments, pets and humans are often afflicted by the same types of cancer which show similar behavior and, in some species, express the same antigen molecules. The treatment of pet tumors using novel therapies is of compelling translational significance.

Immunotherapy in veterinary oncology

Tumor immunology and immunotherapy is one of the most exciting and rapidly expanding fields. The immune system is divided into 2 primary components: the innate immune response and the highly specific, but more slowly developing, adaptive or acquired immune response. Immune responses are separated by whether they are induced by exposure to a foreign antigen (active response) or transferred through serum or lymphocytes from an immunized individual (passive response). The ideal cancer immunotherapy agent should discriminate between cancer and normal cells (specificity), be potent enough to kill small or large numbers of tumor cells (sensitivity), and prevent recurrence of a tumor (durability).