Molecular subtypes in canine hemangiosarcoma reveal similarities with human angiosarcoma

PIK3CA mutation fortifies molecular determinants for immune signaling in vascular cancers

Angiosarcomas are a group of vascular cancers that form malignant blood vessels. These malignancies are seemingly inflamed primarily due to their pathognomonic nature, which consists of irregular endothelium and tortuous blood channels. PIK3CA mutations are oncogenic and disrupt the PI3K pathway. In this study, we aimed to define the molecular and functional consequences of oncogenic PIK3CA mutations in angiosarcoma. We first generated two isogenic hemangiosarcoma cell lines harboring the H1047R hotspot mutations in PIK3CA gene using CRISPR/Cas9. We found PIK3CA-mutant cells established distinct molecular signatures in global gene expression and chromatin accessibility, which were associated with enrichment of immune cytokine signaling, including IL-6, IL-8, and MCP-1. These molecular processes were disrupted by the PI3K-α specific inhibitor, alpelisib. We also observed that the molecular distinctions in PIK3CA-mutant cells were linked to metabolic reprogramming in glycolytic activity and mitochondrial respiration. Our multi-omics analysis revealed that activating PIK3CA mutations regulate molecular machinery that contributes to phenotypic alterations and resistance to alpelisib. Furthermore, we identified potential therapeutic vulnerabilities of PIK3CA mutations in response to PI3K-α inhibition mediated by MAPK signaling. In summary, we demonstrate that PIK3CA mutations perpetuate PI3K activation and reinforce immune enrichment to promote drug resistance in vascular cancers.

Molecular and immune pathobiology of human angiosarcoma

Angiosarcoma is a rare endothelial-derived malignancy that is extremely diverse in anatomy, aetiology, molecular and immune characteristics. While novel therapeutic approaches incorporating targeted agents and immunotherapy have yielded significant improvements in patient outcomes across several cancers, their impact on angiosarcoma remains modest. Contributed by its heterogeneous nature, there is currently a lack of novel drug targets in this disease entity and no reliable biomarkers that predict response to conventional treatment. This review aims to examine the molecular and immune landscape of angiosarcoma in association with its aetiology, anatomical sites, prognosis and therapeutic options. We summarise current efforts to characterise angiosarcoma subtypes based on molecular and immune profiling. Finally, we highlight promising technologies such as single-cell spatial "omics" that may further our understanding of angiosarcoma and propose strategies that can be similarly applied for the study of other rare cancers.

The K9 lymphoma assay allows a genetic subgrouping of canine lymphomas with improved risk classification

We present here the K9 lymphoma assay, a novel 31-gene targeted next-generation sequencing panel designed for genomic profiling of canine lymphoid neoplasms. Addressing the growing demand for advanced diagnostics in veterinary oncology, this assay enables sensitive identification of known and actionable mutations specific to canine lymphomas, while evaluating its prognostic potential to facilitate diagnosis and prognosis. Our analysis, spanning several B- and T-cell lymphoma histotypes, unveiled distinct mutational landscapes distinguishing tumors derived from immature versus mature lymphocytes. Clustering analysis revealed a shared genetic origin between diffuse large B-cell lymphoma and marginal zone lymphoma, aligning with findings in human lymphomas, with TRAF3 emerging as the most frequently mutated gene across B-cell lymphoma subtypes. Significantly, TP53 mutations demonstrated universal adverse prognostic implications across B-cell lymphomas. Additionally, SETD2 mutations contributed to shorter time-to-progression, underscoring the role of epigenetic dysregulation in B-cell tumors. In T-cell lymphomas, SATB1 and FBXW7 were frequently mutated, warranting further investigation in larger cohorts. Our findings advocate for tailored therapeutic approaches based on the genetic profile, impacting treatment decisions and outcomes in canine lymphoma management. This study provides pivotal insights bridging veterinary and human oncology, paving the way for comprehensive genomic diagnostics and therapeutic strategies in comparative oncology.

Hemangiosarcoma Cells Promote Conserved Host-derived Hematopoietic Expansion

Hemangiosarcoma and angiosarcoma are soft-tissue sarcomas of blood vessel-forming cells in dogs and humans, respectively. These vasoformative sarcomas are aggressive and highly metastatic, with disorganized, irregular blood-filled vascular spaces. Our objective was to define molecular programs which support the niche that enables progression of canine hemangiosarcoma and human angiosarcoma. Dog-in-mouse hemangiosarcoma xenografts recapitulated the vasoformative and highly angiogenic morphology and molecular characteristics of primary tumors. Blood vessels in the tumors were complex and disorganized, and they were lined by both donor and host cells. In a series of xenografts, we observed that the transplanted hemangiosarcoma cells created exuberant myeloid hyperplasia and gave rise to lymphoproliferative tumors of mouse origin. Our functional analyses indicate that hemangiosarcoma cells generate a microenvironment that supports expansion and differentiation of hematopoietic progenitor populations. Furthermore, gene expression profiling data revealed hemangiosarcoma cells expressed a repertoire of hematopoietic cytokines capable of regulating the surrounding stromal cells. We conclude that canine hemangiosarcomas, and possibly human angiosarcomas, maintain molecular properties that provide hematopoietic support and facilitate stromal reactions, suggesting their potential involvement in promoting the growth of hematopoietic tumors.

SIGNIFICANCE

We demonstrate that hemangiosarcomas regulate molecular programs supporting hematopoietic expansion and differentiation, providing insights into their potential roles in creating a permissive stromal-immune environment for tumor progression.

Clinical Use of Molecular Biomarkers in Canine and Feline Oncology: Current and Future

Molecular biomarkers are central to personalised medicine for human cancer patients. It is gaining traction as part of standard veterinary clinical practice for dogs and cats with cancer. Molecular biomarkers can be somatic or germline genomic alterations and can be ascertained from tissues or body fluids using various techniques. This review discusses how these genomic alterations can be determined and the findings used in clinical settings as diagnostic, prognostic, predictive, and screening biomarkers. We showcase the somatic and germline genomic alterations currently available to date for testing dogs and cats in a clinical setting, discussing their utility in each biomarker class. We also look at some emerging molecular biomarkers that are promising for clinical use. Finally, we discuss the hurdles that need to be overcome in going 'bench to bedside', i.e., the translation from discovery of genomic alterations to adoption by veterinary clinicians. As we understand more of the genomics underlying canine and feline tumours, molecular biomarkers will undoubtedly become a mainstay in delivering precision veterinary care to dogs and cats with cancer.

Precision Medicine in Veterinary Science

Precision medicine focuses on the clinical management of the individual patient, not on population-based findings. Successes from human precision medicine inform veterinary oncology. Early evidence of success for canines shows how precision medicine can be integrated into practice. Decreasing genomic profiling costs will allow increased utilization and subsequent improvement of knowledge base from which to make better informed decisions. Utility of precision medicine in canine oncology will only increase for improved cancer characterization, enhanced therapy selection, and overall more successful management of canine cancer. As such, practitioners are called to interpret and leverage precision medicine reports for their patients.

Dysregulated miRNAs in a canine model of haemangiosarcoma metastatic to the brain

Haemangiosarcoma is a highly metastatic and lethal cancer of blood vessel-forming cells that commonly spreads to the brain in both humans and dogs. Dysregulations in phosphatase and tensin (PTEN) homologue have been identified in various types of cancers, including haemangiosarcoma. MicroRNAs (miRNAs) are short noncoding single-stranded RNA molecules that play a crucial role in regulating the gene expression. Some miRNAs can function as oncogenes or tumour suppressors, influencing important processes in cancer, such as angiogenesis. This study aimed to investigate whether miRNAs targeting PTEN were disrupted in canine haemangiosarcoma and its corresponding brain metastases (BM). The expression levels of miRNA-10b, miRNA-19b, miRNA-21, miRNA-141 and miRNA-494 were assessed in samples of primary canine cardiac haemangiosarcomas and their matched BM. Furthermore, the miRNA profile of the tumours was compared to samples of adjacent non-cancerous tissue and healthy control tissues. In primary cardiac haemangiosarcoma, miRNA-10b showed a significant increase in expression, while miRNA-494 and miRNA-141 exhibited downregulation. Moreover, the overexpression of miRNA-10b was retained in metastatic brain lesions. Healthy tissues demonstrated significantly different expression patterns compared to cancerous tissues. In particular, the expression of miRNA-10b was nearly undetectable in both control brain tissue and perimetastatic cerebral tissue. These findings can provide a rationale for the development of miRNA-based therapeutic strategies, aimed at selectively treating haemangiosarcoma.

Review of Molecular Technologies for Investigating Canine Cancer

Genetic molecular testing is starting to gain traction as part of standard clinical practice for dogs with cancer due to its multi-faceted benefits, such as potentially being able to provide diagnostic, prognostic and/or therapeutic information. However, the benefits and ultimate success of genomic analysis in the clinical setting are reliant on the robustness of the tools used to generate the results, which continually expand as new technologies are developed. To this end, we review the different materials from which tumour cells, DNA, RNA and the relevant proteins can be isolated and what methods are available for interrogating their molecular profile, including analysis of the genetic alterations (both somatic and germline), transcriptional changes and epigenetic modifications (including DNA methylation/acetylation and microRNAs). We also look to the future and the tools that are currently being developed, such as using artificial intelligence (AI) to identify genetic mutations from histomorphological criteria. In summary, we find that the molecular genetic characterisation of canine neoplasms has made a promising start. As we understand more of the genetics underlying these tumours and more targeted therapies become available, it will no doubt become a mainstay in the delivery of precision veterinary care to dogs with cancer.

Canine major histocompatibility complex class I (MHC-I) diversity landscape

The genes of the Major Histocompatibility Complex class I (MHC-I) are among the most diverse in the mammalian genome, playing a crucial role in immunology. Understanding the diversity landscape of MHC-I is therefore of paramount importance. The dog is a key translational model in various biomedical fields. However, our understanding of the canine MHC-I diversity landscape lags significantly behind that of humans. To address this deficiency, we used our newly developed software, KPR de novo assembler and genotyper, to genotype 1,325 samples from 1,025 dogs with paired-end RNA-seq data from 43 BioProjects, after extensive quality control. Among 926 dogs that pass the QC, 591 dogs (64%) have at least one allele genotyped, and a total of 97 known alleles and 52 putative new alleles were identified. Further analysis reveals that DLA-I gene expression levels vary among the tissues, with lowest for testis and brain tissues and highest for blood, corpus luteum, and spleen. We identified dominant alleles in each of the 17 canine breeds, as well as among the entire canine population. Furthermore, our analysis also identifies breed-specific alleles and mutually co-occurred/exclusive alleles. Our study indicates that canine DLA-88 is as diversified as human HLA-A/B/C genes within the entire population, but less diversified within a breed than with HLA-A/B/C within an ethnic group. Lastly, we examined the hypervariable regions (HVR) within or across human/canine MHC-I alleles and found that 80% of the HVRs overlap between the two species. We further noted that 80% of the HVRs are within 4A contact with the peptides, and that the dog-human difference overlaps with only 20% HVRs. Our research offers valuable insights for immunological studies involving dogs.

Parthenolide As a Therapeutic for Disseminated Canine Neoplasms

This study provides a unique translational research opportunity to help both humans and dogs diagnosed with diseases that carry dismal prognoses in both species: histiocytic sarcoma (HS), hemangiosarcoma (HSA), and disseminated mastocytosis/mast cell tumor (MCT). Although exceedingly rare in humans, these so called "orphan diseases" are relatively more common in dogs. For these and other more commonplace cancers like lymphoma (Lym), dogs are an excellent translational model for human disease due to remarkably similar disease biology. In this study, assays were performed to assess the therapeutic potential of parthenolide (PTL), a known canonical nuclear factor kappa B (NF-κB) signaling inhibitor with additional mechanisms of antineoplastic activity, including alteration of cellular reduction-oxidation balance. Canine cell lines and primary cells are sensitive to PTL and undergo dose-dependent apoptosis after exposure to drug. PTL exposure also leads to glutathione depletion, reactive oxygen species generation, and NF-κB inhibition in canine cells. Standard-of-care therapeutics broadly synergize with PTL. In two canine HS cell lines, expression of NF-κB pathway signaling partners is downregulated with PTL therapy. Preliminary data suggest that PTL inhibits NF-κB activity of cells and extends survival time in a mouse model of disseminated canine HS. These data support further investigation of compounds that can antagonize canonical NF-κB pathway signaling in these cancers and pave the way for clinical trials of PTL in affected dogs. As dogs are an excellent natural disease model for these cancers, these data will ultimately improve our understanding of their human disease counterparts and hopefully improve care for both species. SIGNIFICANCE STATEMENT: Disseminated neoplasms in human and canine cancers are challenging to treat, and novel therapeutic approaches are needed to improve outcomes. Parthenolide is a promising treatment for histiocytic sarcoma, hemangiosarcoma, and mast cell neoplasia.

Hemangiosarcoma in dogs as a potential non-rodent animal model for drug discovery research of angiosarcoma in humans

Since the domestication of dogs 10,000 years ago, they have shared their living environment with humans and have co-evolved. The breeding process that dogs have undergone in only a few centuries has led to a significant accumulation of specific genetic alterations that could induce particular diseases in certain breeds. These canine diseases are similar to what is found in humans with several differences; therefore, comparing such diseases occurring in humans and dogs can help discover novel disease mechanisms, pathways, and causal genetic factors. Human angiosarcoma (AS) and canine hemangiosarcoma (HSA), which are sarcomas originating from endothelium, are examples of diseases shared between humans and dogs. They exhibit similar characteristics and clinical behaviors, although with some critical differences resulting from evolution. In this review, we will describe the similarities and differences in terms of clinical and molecular characteristics between human AS and canine HSA, and discuss how these similarities and differences can be applied to advance the treatment of these diseases.

Identification of genomic alterations with clinical impact in canine splenic hemangiosarcoma

Canine hemangiosarcoma (HSA) is an aggressive cancer of endothelial cells with short survival times. Understanding the genomic landscape of HSA may aid in developing therapeutic strategies for dogs and may also inform therapies for the rare and aggressive human cancer angiosarcoma. The objectives of this study were to build a framework for leveraging real-world genomic and clinical data that could provide the foundation for precision medicine in veterinary oncology, and to determine the relationships between genomic and clinical features in canine splenic HSA. One hundred and nine dogs with primary splenic HSA treated by splenectomy that had tumour sequencing via the FidoCure® Precision Medicine Platform targeted sequencing panel were enrolled. Patient signalment, weight, metastasis at diagnosis and overall survival time were retrospectively evaluated. The incidence of genomic alterations in individual genes and their relationship to patient variables including outcome were assessed. Somatic mutations in TP53 (n = 44), NRAS (n = 20) and PIK3CA (n = 19) were most common. Survival was associated with presence of metastases at diagnosis and germline variants in SETD2 and NOTCH1. Age at diagnosis was associated with somatic NRAS mutations and breed. TP53 and PIK3CA somatic mutations were found in larger dogs, while germline SETD2 variants were found in smaller dogs. We identified both somatic mutations and germline variants associated with clinical variables including age, breed and overall survival. These genetic changes may be useful prognostic factors and provide insight into the genomic landscape of hemangiosarcoma.

Descriptive analysis of haemangiosarcoma occurrence in dogs enrolled in the Golden Retriever lifetime study

Haemangiosarcoma is a relatively common malignant tumour in dogs, and one of the primary outcomes of interest for the Golden Retriever Lifetime Study. This study collects longitudinal data and samples from a cohort of golden retrievers, with the aim of identification of nutritional, genetic, environmental, lifestyle and reproductive risk factors for cancers and other important diseases in dogs. This analysis describes the accumulating data and samples, which are available for use by researchers to fulfil the study's objectives. As of September 2022, 233/3044 dogs enrolled in the study had been diagnosed with haemangiosarcoma (7.65%), with an incidence rate of 1.10 cases per 100 dog-years. Visceral haemangiosarcoma was the most common, affecting 211/3044 study dogs (6.9%). One hundred and twenty eight visceral haemangiosarcoma diagnoses specified the presence of splenic tumours (60.7%) and 119 specified the presence of cardiac tumours (56.4%). The probability of remaining without a haemangiosarcoma diagnosis declined from 100% from approximately 4 years of age, to a 12 year probability of 91.1% in intact females (95% CI 84.4%-98.3%), 60.7% in neutered females (95% CI 41.6%-88.6%), 72.9% in intact males (95% CI 62.9%-84.6%) and 70.0% in neutered males (95% CI 53.4%-92.0%). The 1 year survival probability for visceral haemangiosarcoma was 1.42% (95% CI 0.37%-5.47%); for cutaneous haemangiosarcoma, it was 84.6% (95% CI 67.1%-99.99%). The accumulated data and samples are a considerable resource for further investigation of canine haemangiosarcoma and have a potential role in translational medicine.

New molecular targets in canine hemangiosarcoma-Comparative review and future of the precision medicine

Human angiosarcoma and canine hemangiosarcoma reveal similarities not only in their aggressive clinical behaviour, but especially in molecular landscape and genetic alterations involved in tumorigenesis and metastasis formation. Currently, no satisfying treatment that allows for achieving long overall survival or even prolonged time to progression does not exist. Due to the progress that has been made in targeted therapies and precision medicine the basis for a new treatment design is to uncover mutations and their functions as possible targets to provide tailored drugs for individual cases. Whole exome or genome sequencing studies and immunohistochemistry brought in the last few years important discoveries and identified the most common mutations with probably crucial role in this tumour development. Also, despite a lack of mutation in some of the culprit genes, the cancerogenesis cause may be buried in main cellular pathways connected with proteins encoded by those genes and involving, for example, pathological angiogenesis. The aim of this review is to highlight the most promising molecular targets for precision oncology treatment from the veterinary perspective aided by the principles of comparative science. Some of the drugs are only undergoing laboratory in vitro studies and others entered the clinic in the management of other cancer types in humans, but those used in dogs with promising responses have been mentioned as priorities.

Shared hotspot mutations in oncogenes position dogs as an unparalleled comparative model for precision therapeutics

Naturally occurring canine cancers have remarkable similarities to their human counterparts. To better understand these similarities, we investigated 671 client-owned dogs from 96 breeds with 23 common tumor types, including those whose mutation profile are unknown (anal sac carcinoma and neuroendocrine carcinoma) or understudied (thyroid carcinoma, soft tissue sarcoma and hepatocellular carcinoma). We discovered mutations in 50 well-established oncogenes and tumor suppressors, and compared them to those reported in human cancers. As in human cancer, TP53 is the most commonly mutated gene, detected in 22.5% of canine tumors overall. Canine tumors share mutational hotspots with human tumors in oncogenes including PIK3CA, KRAS, NRAS, BRAF, KIT and EGFR. Hotspot mutations with significant association to tumor type include NRAS G61R and PIK3CA H1047R in hemangiosarcoma, ERBB2 V659E in pulmonary carcinoma, and BRAF V588E (equivalent of V600E in humans) in urothelial carcinoma. Our findings better position canines as a translational model of human cancer to investigate a wide spectrum of targeted therapies.

Molecular Profile of Canine Hemangiosarcoma and Potential Novel Therapeutic Targets

Canine hemangiosarcoma (HSA) is a relatively common neoplasia, occurring mainly in the skin, spleen, liver and right atrium. Despite the numerous studies investigating the treatment of canine HSA, no significant improvement in survival has been achieved in the last 20 years. Advancements in genetic and molecular profiling presented molecular similarities between canine HSA and human angiosarcoma. It could therefore serve as a valuable model for investigating new and more effective treatments in people and dogs. The most common genetic abnormalities in canine HSA have been found in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and neuroblastoma RAS viral oncogene homolog (NRAS) pathways. Mutations are also found in tumor protein p53 (TP53), phosphatase and tensin homolog (PTEN) and cyclin dependent kinase inhibitor 2A (CDKN2A). Known abnormal protein expression could be exploited to trial new target treatments that could be beneficial for both canine and human patients. Despite the high expression of vascular endothelial growth factor (VEGF) and its receptor (VEGFR), no correlation with overall survival time has ever been found. In this review, we explore the most recent developments in molecular profiling in canine HSA and discuss their possible applications in the prognosis and treatment of this fatal disease.

Diagnosis, Prognosis, and Treatment of Canine Hemangiosarcoma: A Review Based on a Consensus Organized by the Brazilian Association of Veterinary Oncology, ABROVET

Hemangiosarcoma is a mesenchymal neoplasm originating in the endothelial cells of blood vessels; they can be classified as non-visceral and visceral types. Non-visceral hemangiosarcomas can affect the skin, subcutaneous tissues, and muscle tissues; visceral hemangiosarcomas can affect the spleen, liver, heart, lungs, kidneys, oral cavity, bones, bladder, uterus, tongue, and retroperitoneum. Among domestic species, dogs are most affected by cutaneous HSA. Cutaneous HSA represents approximately 14% of all HSA diagnosed in this species and less than 5% of dermal tumors, according to North American studies. However, Brazilian epidemiological data demonstrate a higher prevalence, which may represent 27 to 80% of all canine HSAs and 13.9% of all skin neoplasms diagnosed in this species. Cutaneous HSA most commonly affects middle-aged to elderly dogs (between 8 and 15 years old), with no gender predisposition for either the actinic or non-actinic forms. The higher prevalence of cutaneous HSA in some canine breeds is related to lower protection from solar radiation, as low skin pigmentation and hair coverage lead to greater sun exposure. Actinic changes, such as solar dermatosis, are frequent in these patients, confirming the influence of solar radiation on the development of this neoplasm. There are multiple clinical manifestations of hemangiosarcoma in canines. The diagnostic approach and staging classification of cutaneous HSAs are similar between the different subtypes. The definitive diagnosis is obtained through histopathological analysis of incisional or excisional biopsies. Cytology can be used as a presurgical screening test; however, it has little diagnostic utility in cases of HSA because there is a high risk of blood contamination and sample hemodilution. Surgery is generally the treatment of choice for dogs with localized non-visceral HSA without evidence of metastatic disease. Recently, electrochemotherapy (ECT) has emerged as an alternative therapy for the local ablative treatment of different neoplastic types; the use of radiotherapy for the treatment of dogs with cutaneous HSA is uncommon. There is greater consensus in the literature regarding the indications for adjuvant chemotherapy in subcutaneous and muscular HSA; doxorubicin is the most frequently used antineoplastic agent for subcutaneous and muscular subtypes and can be administered alone or in combination with other drugs. Other therapies include antiangiogenic therapy, photodynamic therapy, the association of chemotherapy with the metronomic dose, targeted therapies, and natural products. The benefits of these therapies are presented and discussed. In general, the prognosis of splenic and cardiac HSA is unfavorable. As a challenging neoplasm, studies of new protocols and treatment modalities are necessary to control this aggressive disease.

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.

Analyses of canine cancer mutations and treatment outcomes using real-world clinico-genomics data of 2119 dogs

Spontaneous tumors in canines share significant genetic and histological similarities with human tumors, positioning them as valuable models to guide drug development. However, current translational studies have limited real world evidence as cancer outcomes are dispersed across veterinary clinics and genomic tests are rarely performed on dogs. In this study, we aim to expand the value of canine models by systematically characterizing genetic mutations in tumors and their response to targeted treatments. In total, we collect and analyze survival outcomes for 2119 tumor-bearing dogs and the prognostic effect of genomic alterations in a subset of 1108 dogs. Our analysis identifies prognostic concordance between canines and humans in several key oncogenes, including TP53 and PIK3CA. We also find that several targeted treatments designed for humans are associated with a positive prognosis when used to treat canine tumors with specific genomic alterations, underscoring the value of canine models in advancing drug discovery for personalized oncology.

Genomic landscapes of canine splenic angiosarcoma (hemangiosarcoma) contain extensive heterogeneity within and between patients

Cancer genomic heterogeneity presents significant challenges for understanding oncogenic processes and for cancer’s clinical management. Variation in driver mutation frequency between patients with the same tumor type as well as within an individual patients’ cancer can shape the use of mutations as diagnostic, prognostic, and predictive biomarkers. We have characterized genomic heterogeneity between and within canine splenic hemangiosarcoma (HSA), a common naturally occurring cancer in pet dogs that is similar to human angiosarcoma (AS). HSA is a clinically, physiologically, and genomically complex canine cancer that may serve as a valuable model for understanding the origin and clinical impact of cancer heterogeneity. We conducted a prospective collection of 52 splenic masses from 43 dogs (27 HSA, 15 benign masses, and 1 stromal sarcoma) presenting for emergency care with hemoperitoneum secondary to a ruptured splenic mass. Multi-platform genomic analysis included matched tumor/normal targeted sequencing panel and exome sequencing. We found candidate somatic cancer driver mutations in 14/27 (52%) HSAs. Among recurrent candidate driver mutations, TP53 was most commonly mutated (30%) followed by PIK3CA (15%), AKT1 (11%), and CDKN2AIP (11%). We also identified significant intratumoral genomic heterogeneity, consistent with a branched evolution model, through multi-region exome sequencing of three distinct tumor regions from selected primary splenic tumors. These data provide new perspectives on the genomic landscape of this veterinary cancer and suggest a cross-species value for using HSA in pet dogs as a naturally occurring model of intratumoral heterogeneity.

The immunohistochemical detection of peroxiredoxin 1 and 2 in canine spontaneous vascular endothelial tumors

Peroxiredoxin (PRDX) is an antioxidant enzyme family with six isoforms (PRDX1-6). The main function of PRDXs is to decrease cellular oxidative stress by reducing reactive oxygen species, such as hydrogen peroxide, to H2O. Recently, it has been reported that PRDXs are overexpressed in various malignant tumors in humans, and are involved in the development, proliferation, and metastasis of tumors. However, studies on the expression of PRDXs in tumors of animals are limited. Therefore, in the present study, we immunohistochemically investigated the expression of PRDX1 and 2 in spontaneous canine hemangiosarcoma (HSA) and hemangioma (HA), as well as in selected normal tissue and granulation tissue, including newly formed blood vessels. Although there were some exceptions, immunolocalization of PRDX1 and 2 in normal canine tissues was similar to those in humans, rats, or mice. In granulation tissue, angiogenic endothelial cells were strongly positive for PRDX1 and 2, whereas quiescent endothelial cells in mature vessels were negative. Both PRDX1 and 2 were significantly highly expressed in HSA compared to HA. There were no significant differences in the expression of PRDX1 and 2 among the subtypes and primary sites of HSA. These results suggest that PRDX1 and 2 may be involved in the angiogenic phenotypes of endothelial cells in granulation tissue as well as in the behavior in the malignant endothelial tumors.

Review: NF-kB activation in canine cancer

Spontaneous tumors in dogs share several environmental, epidemiologic, biologic, clinical and molecular features with a wide variety of human cancers, making this companion animal an attractive model. Nuclear factor kappa B (NF-kB) transcription factor overactivation is common in several human cancers, and there is evidence that similar signaling aberrations also occur in canine cancers including lymphoma, leukemia, hemangiosarcoma, mammary cancer, melanoma, glioma, and prostate cancer. This review provides an overview of NF-kB signaling biology, both in health and in cancer development. It also summarizes available evidence of aberrant NF-kB signaling in canine cancer, and reviews antineoplastic compounds that have been shown to inhibit NF-kB activity used in various types of canine cancers. Available data suggest that dogs may be an excellent model for human cancers that have overactivation of NF-kB.

Genetic context of oncogenic drivers dictates vascular sarcoma development in aP2‐Cre mice

Angiosarcomas are aggressive vascular sarcomas that arise from endothelial cells and have an extremely poor prognosis. Because of the rarity of angiosarcomas, knowledge of molecular drivers and optimized treatment strategies is lacking, highlighting the need for in vivo models to study the disease. Previously, we generated genetically engineered mouse models of angiosarcoma driven by aP2‐Cre‐mediated biallelic loss of Dicer1 or conditional activation of Kras^G12D with Cdkn2a loss that histologically and genetically resemble human tumors. In the present study, we found that DICER1 functions as a potent tumor suppressor and its deletion, in combination with either KRAS^G12D expression or Cdkn2a loss, is associated with angiosarcoma development. Independent of the genetic driver, the mTOR pathway was activated in all murine angiosarcoma models. Direct activation of the mTOR pathway by conditional deletion of Tsc1 with aP2‐Cre resulted in tumors that resemble intermediate grade human kaposiform hemangioendotheliomas, indicating that mTOR activation was not sufficient to drive the malignant angiosarcoma phenotype. Genetic dissection of the spectrum of vascular tumors identified genes specifically regulated in the aggressive murine angiosarcomas that are also enriched in human angiosarcoma. The genetic dissection driving the transition across the malignant spectrum of endothelial sarcomas provides an opportunity to identify key determinants of the malignant phenotype, novel therapies for angiosarcoma, and novel in vivo models to further explore angiosarcoma pathogenesis. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Phase I/II Trial of Vemurafenib in Dogs with Naturally Occurring, BRAF-mutated Urothelial Carcinoma

BRAF-targeted therapies including vemurafenib (Zelboraf) induce dramatic cancer remission; however, drug resistance commonly emerges. The purpose was to characterize a naturally occurring canine cancer model harboring complex features of human cancer, to complement experimental models to improve BRAF-targeted therapy. A phase I/II clinical trial of vemurafenib was performed in pet dogs with naturally occurring invasive urothelial carcinoma (InvUC) harboring the canine homologue of human BRAF ^V600E The safety, MTD, pharmacokinetics, and antitumor activity were determined. Changes in signaling and immune gene expression were assessed by RNA sequencing and phosphoproteomic analyses of cystoscopic biopsies obtained before and during treatment, and at progression. The vemurafenib MTD was 37.5 mg/kg twice daily. Anorexia was the most common adverse event. At the MTD, partial remission occurred in 9 of 24 dogs (38%), with a median progression-free interval of 181 days (range, 53-608 days). In 18% of the dogs, new cutaneous squamous cell carcinoma and papillomas occurred, a known pharmacodynamic effect of vemurafenib in humans. Upregulation of genes in the classical and alternative MAPK-related pathways occurred in subsets of dogs at cancer progression. The most consistent transcriptomic changes were the increase in patterns of T lymphocyte infiltration during the first month of vemurafenib, and of immune failure accompanying cancer progression. In conclusion, the safety, antitumor activity, and cutaneous pharmacodynamic effects of vemurafenib, and the development of drug resistance in dogs closely mimic those reported in humans. This suggests BRAF-mutated canine InvUC offers an important complementary animal model to improve BRAF-targeted therapies in humans.

Canine tumor mutational burden is correlated with TP53 mutation across tumor types and breeds

Spontaneous canine cancers are valuable but relatively understudied and underutilized models. To enhance their usage, we reanalyze whole exome and genome sequencing data published for 684 cases of >7 common tumor types and >35 breeds, with rigorous quality control and breed validation. Our results indicate that canine tumor alteration landscape is tumor type-dependent, but likely breed-independent. Each tumor type harbors major pathway alterations also found in its human counterpart (e.g., PI3K in mammary tumor and p53 in osteosarcoma). Mammary tumor and glioma have lower tumor mutational burden (TMB) (median < 0.5 mutations per Mb), whereas oral melanoma, osteosarcoma and hemangiosarcoma have higher TMB (median ≥ 1 mutations per Mb). Across tumor types and breeds, TMB is associated with mutation of TP53 but not PIK3CA, the most mutated genes. Golden Retrievers harbor a TMB-associated and osteosarcoma-enriched mutation signature. Here, we provide a snapshot of canine mutations across major tumor types and breeds.

Canine Oncopanel: A capture-based, NGS platform for evaluating the mutational landscape and detecting putative driver mutations in canine cancers

Canine cancer, a significant cause of mortality in domestic dogs, is a powerful comparative model for human cancers. Revealing genetic alterations driving the oncogenesis of canine cancers holds great potential to deepen our understanding of the cancer biology, guide therapeutic development, and improve cancer management in both dogs and people. Next generation sequencing (NGS) based-diagnostic panels have been routinely used in human oncology for the identification of clinically-actionable mutations, enabling tailored treatments based on the individual's unique mutation profiles. Here, we report the development of a comprehensive canine cancer gene panel, the Canine Oncopanel, using a hybridization capture-based targeted NGS method. The Canine Oncopanel allows deep sequencing of 283 cancer genes and the detection of somatic mutations within these genes. Vigorous optimization was performed to achieve robust, high-standard performance using metrics of similar cancer panels in human oncology as benchmarks. Validation of the Canine Oncopanel on reference tumour samples with known mutations demonstrated that it can detect variants previously identified by alternative methods, with high accuracy and sensitivity. Putative drivers were detected in over 90% of clinical samples, showing high sensitivity. The Canine Oncopanel is suitable to map mutation profiles and identify putative driver mutations across common and rare cancer types in dogs. The data generated by the Canine Oncopanel presents a rich resource of putative oncogenic driver mutations and potential clinically relevant markers, paving the way for personalized diagnostics and precision medicine in canine oncology.

Comparison of the oncogenomic landscape of canine and feline hemangiosarcoma shows novel parallels with human angiosarcoma

Angiosarcoma (AS) is a highly aggressive tumor of blood and lymphatic vessels in humans that shares many similarities with spontaneously occurring hemangiosarcoma (HSA) in dogs and cats. To investigate the genetic suitability of HSA as a model for AS, we sequenced ∼1000 cancer genes in 41 cases of HSA and matched germline tissue: 15 canine visceral HSAs, 13 canine skin HSAs and 13 feline skin HSAs. Analysis of visceral HSAs from dogs presenting with concurrent splenic and cardiac neoplasms showed that the tumors were not independent primaries, consistent with the highly metastatic nature of HSA. Comparison of HSA to AS revealed that several driver genes were recurrently mutated in both species, such as TP53, PIK3CA, ATRX, GRIN2A and LRP1B. Similar to AS, a UV mutational signature was found in a subset of canine cutaneous HSAs and both species show differing mutational profiles between tissue sites. Our characterization of canine and feline HSA demonstrates many important parallels to AS and provides hope that future studies on these cancers will benefit of all three species.

Genomically Complex Human Angiosarcoma and Canine Hemangiosarcoma Establish Convergent Angiogenic Transcriptional Programs Driven by Novel Gene Fusions

Sporadic angiosarcomas are aggressive vascular sarcomas whose rarity and genomic complexity present significant obstacles in deciphering the pathogenic significance of individual genetic alterations. Numerous fusion genes have been identified across multiple types of cancers, but their existence and significance remain unclear in sporadic angiosarcomas. In this study, we leveraged RNA-sequencing data from 13 human angiosarcomas and 76 spontaneous canine hemangiosarcomas to identify fusion genes associated with spontaneous vascular malignancies. Ten novel protein-coding fusion genes, including TEX2-PECAM1 and ATP8A2-FLT1, were identified in seven of the 13 human tumors, with two tumors showing mutations of TP53. HRAS and NRAS mutations were found in angiosarcomas without fusions or TP53 mutations. We found 15 novel protein-coding fusion genes including MYO16-PTK2, GABRA3-FLT1, and AKT3-XPNPEP1 in 11 of the 76 canine hemangiosarcomas; these fusion genes were seen exclusively in tumors of the angiogenic molecular subtype that contained recurrent mutations in TP53, PIK3CA, PIK3R1, and NRAS. In particular, fusion genes and mutations of TP53 cooccurred in tumors with higher frequency than expected by random chance, and they enriched gene signatures predicting activation of angiogenic pathways. Comparative transcriptomic analysis of human angiosarcomas and canine hemangiosarcomas identified shared molecular signatures associated with activation of PI3K/AKT/mTOR pathways. Our data suggest that genome instability induced by TP53 mutations might create a predisposition for fusion events that may contribute to tumor progression by promoting selection and/or enhancing fitness through activation of convergent angiogenic pathways in this vascular malignancy. IMPLICATIONS: This study shows that, while drive events of malignant vasoformative tumors of humans and dogs include diverse mutations and stochastic rearrangements that create novel fusion genes, convergent transcriptional programs govern the highly conserved morphologic organization and biological behavior of these tumors in both species.

Machine learning application identifies novel gene signatures from transcriptomic data of spontaneous canine hemangiosarcoma

Angiosarcomas are soft-tissue sarcomas that form malignant vascular tissues. Angiosarcomas are very rare, and due to their aggressive behavior and high metastatic propensity, they have poor clinical outcomes. Hemangiosarcomas commonly occur in domestic dogs, and share pathological and clinical features with human angiosarcomas. Typical pathognomonic features of this tumor are irregular vascular channels that are filled with blood and are lined by a mixture of malignant and nonmalignant endothelial cells. The current gold standard is the histological diagnosis of angiosarcoma; however, microscopic evaluation may be complicated, particularly when tumor cells are undetectable due to the presence of excessive amounts of nontumor cells or when tissue specimens have insufficient tumor content. In this study, we implemented machine learning applications from next-generation transcriptomic data of canine hemangiosarcoma tumor samples (n = 76) and nonmalignant tissues (n = 10) to evaluate their training performance for diagnostic utility. The 10-fold cross-validation test and multiple feature selection methods were applied. We found that extra trees and random forest learning models were the best classifiers for hemangiosarcoma in our testing datasets. We also identified novel gene signatures using the mutual information and Monte Carlo feature selection method. The extra trees model revealed high classification accuracy for hemangiosarcoma in validation sets. We demonstrate that high-throughput sequencing data of canine hemangiosarcoma are trainable for machine learning applications. Furthermore, our approach enables us to identify novel gene signatures as reliable determinants of hemangiosarcoma, providing significant insights into the development of potential applications for this vascular malignancy.