Maintenance therapy with toceranib following doxorubicin-based chemotherapy for canine splenic hemangiosarcoma

Acute and chronic systemic inflammation associated with canine nodular splenic lesions composed of heterogeneous cell components: four cases (2020-2024)

OBJECTIVES

To describe the clinical presentation and clinicopathological findings of dogs with nodular splenic lesions composed of heterogeneous cell components associated with systemic inflammation and to provide information on the outcome after surgical resection.

MATERIALS AND METHODS

Medical records were searched for dogs with histologically and immunohistochemically characterised nodular splenic lesions with mixed stromal, histiocytic and lymphoid cells and the presence of systemic inflammatory markers at the time of diagnosis.

RESULTS

Four dogs were included, of which three had an undifferentiated splenic stromal sarcoma and one had a splenic leiomyosarcoma. Fever and abdominal pain were reported in three and four cases, respectively. All dogs showed hyperglobulinaemia and marked changes in the serum protein electrophoresis profile. C-reactive protein and fibrinogen concentrations were both increased in three cases. These abnormalities completely resolved after splenectomy. Moreover, two dogs had concomitant glomerular disease and one dog had liver amyloidosis. Three dogs were still alive and asymptomatic 1, 6 and 9 months after surgery. One dog died 16 months after the initial presentation due to complications related to progressive renal failure.

CLINICAL SIGNIFICANCE

Based on this report, nodular splenic lesions with heterogeneous cell components may directly be associated with a pro-inflammatory state and should be considered as part of the differential diagnosis of fever and hyperglobulinaemia in dogs. Furthermore, early recognition and treatment of these lesions could reduce the risk of systemic complications potentially associated with amyloid deposit and organ failure.

Analysis of VEGFR-2 and PDGFR-β expression in canine splenic hemangiosarcoma to identify drug repositioning candidates

Splenic tumors are very common in dogs, and canine hemangiosarcoma (HSA) is one of the most important malignant splenic tumors. Surgery followed by chemotherapy (anthracycline-based protocols) is recommended for treating canine HSA; however, patients still do not achieve long-term survival. Therefore, this research aimed to assess vascular endothelial growth factor receptor-2 (VEGFR-2) and platelet-derived growth factor receptor-β (PDGFR-β) gene expression in formalin-fixed tissues, evaluate the quality of mRNA for quantitative polymerase chain reaction (qPCR) analysis and identify drug repositioning candidates based on VEGFR-2 and PDGFR-β. qPCR analysis identified the relative expression of heterogeneous VEGFR-2 and PDGFR-β, with samples showing no transcripts or very low expression and those with higher relative quantification for both genes. We then used immunohistochemistry to correlate the relative quantification of VEGFR-2 and PDGFR-β transcripts with respective higher protein expression to validate our results. In the next step, we evaluated drug repositioning candidates and identified small molecule inhibitors (i.e. sorafenib) and natural compounds (curcumin and resveratrol) with the ability to block VEGFR-2 and PDGFR-β genes. Overall, our results indicated that VEGFR-2 and PDGFR-β expression is highly variable among canine HSA samples and different drugs can block the expression of both genes. Therefore, a personalized approach could be useful for selecting anti-VEGFR-2 and PDGFR-β therapies and both genes are potential candidates for future oncological panels.

Prospective study of successful autologous dendritic cell therapy in dogs with splenic stage II hemangiosarcoma

Hemangiosarcoma is an aggressive tumour that most frequently occurs in larger, middle-aged dogs of certain breeds. The spleen is the most commonly affected organ. The aim of this prospective therapy study was to evaluate the clinical effect of autologous, monocyte-derived dendritic cell (DC) therapy in canine hemangiosarcoma stage II after splenectomy. Dogs (n=452) diagnosed with splenic hemangiosarcoma that underwent splenectomy were enrolled. Of these, 42 dogs with stage II entered the DC therapy study. The median survival time for the total group of 42 dogs was 203 days. The median survival for the group (n=34) that received the full DC therapy (≥3 vaccines) was 256 days, with a 29 % one-year survival rate and a hazard ratio of 0.30, adjusted to age and bodyweight (P=0.010). We further observed a significant increase in DC yield after each application and demonstrated that DC yield at the beginning of treatment is significantly related to patient survival. While further evidence is needed, we conclude that autologous, monocyte-derived DC therapy is a viable alternative to standard treatment methods of canine splenic stage II hemangiosarcoma.

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

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

Current understanding of comparative pathology and prospective research approaches for canine hemangiosarcoma

Hemangiosarcoma (HSA) is a malignant tumor originating from endothelial cells. HSA typically develops in dogs, but is rare in other animals, including humans. Although surgery and chemotherapy are conventional treatments for HSA, neither treatment can significantly improve patient prognosis. To develop novel and effective therapeutics, a deeper understanding of HSA pathogenesis must be acquired. However, the limited research tools for HSA have been unable to make a breakthrough; therefore, it is crucial to widely utilize or establish novel research tools such as patient-derived xenograft models, organoids, and chicken embryo xenograft models. The pathogenesis of the human counterpart of HSA, angiosarcoma (AS), also remains incompletely understood, preventing the extrapolation of findings from humans to dogs, unlike other diseases. In this review, we summarize the clinicopathological and morphological features of HSA, and then we discuss the current understanding of the molecular pathology of HSA. Finally, we highlight promising research tools that may accelerate HSA basic research toward developing novel therapeutics. We also briefly summarize AS to help researchers comprehend HSA from the perspective of comparative pathology.

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.

[Adjuvant treatment of canine splenic hemangiosarcoma with autologous dendritic cell therapy - a prospective, randomized double-blind study]

OBJECTIVE

Canine splenic hemangiosarcomas (HSA) are malignant mesenchymal tumors with a high tendency for metastasis. Median survival times after splenectomy followed by adjuvant chemotherapy usually range between 5 and 8 months. The aim of this prospective randomized double-blinded study was to examine the efficacy of a commercially available dendritic cell therapy (PetBioCell) following splenectomy. In addition, possible side effects of this therapy were evaluated.

MATERIAL AND METHODS

Twenty-one dogs with histologically confirmed splenic HSA without metastasis (stages I or II) were included in the study. Ten dogs received the dendritic cell therapy, and 11 dogs received a placebo. Injections were administered according to the manufacturer's instructions monthly for the first 3 months and then every 3 months until death. Survival times and toxicoses of both groups were compared.

RESULTS

Follow-up data were available for all 21 patients; the observation period ranging until euthanasia or metastasis-related death. One patient that had received the dendritic cell therapy was euthanized due to prostatitis and experienced the longest survival time (668 days). One dog in the placebo-group lived for 448 days after splenectomy. The median survival times in the dendritic cell therapy and the placebo group amounted to 74 and 126 days, respectively. There was no significant difference in tumor-free interval (t(18) = 1.4, p = 0.911) and survival times (t(19) = -0.094, p = 0.463) between the 2 groups. Toxicoses reported in both groups were mild and self-limiting.

CONCLUSION

Immunotherapy using autologous, immature and unprimed dendritic cells according to the PetBioCell method failed to show efficacy on tumor-free interval and survival time in the presented dog population with splenic hemangiosarcoma.

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.

The role of toceranib phosphate in dogs with non-mast cell neoplasia: A systematic review

The use of tyrosine kinase inhibitors (TKI) has gained significant importance in veterinary cancer patients over the last decade. Toceranib phosphate has been licensed for the treatment of dogs with mast cell tumours. Its molecular similarity to sunitinib, a TKI used in human medicine, has led many veterinary oncologists to use this agent for multiple neoplastic diseases. The aim of the current study was to perform a systematic review of the evidence for the use of toceranib in dogs with non-mast cell neoplasia. Two electronic databases were searched. Publications were included if toceranib was used as a treatment option in canine patients. Studies and case reports were excluded if toceranib was used as part of a multi-modal treatment plan and response or outcome data related to toceranib therapy were not described. A total of 28 studies were included from 122 references. The most common types of neoplasias identified were neuroendocrine tumours, anal gland sac adenocarcinoma, and osteosarcoma. Multiple other neoplasias had one or two studies identified to describe the use of toceranib. Results of the study support that toceranib phosphate may have efficacy against certain types of neoplasia under certain conditions, such as neuroendocrine tumours, gastrointestinal stromal tumours and anal sac adenocarcinomas, while it is probably not effective for the management of metastatic osteosarcoma based on the findings of the review.

Canine and feline haemangiosarcoma

INTRODUCTION

Haemangiosarcoma (HSA) is a malignant neoplasm of dogs and cats that is suspected to originate from a pluripotent bone marrow progenitor with a complex and multifactorial pathogenesis.

APPROACH

Pertinent literature was identified, reviewed, and summarized for inclusion in the manuscript.

RESULTS/INTERPRETATION

Dogs are more frequently diagnosed with HSA than cats, and primary sites of this disease include dermal, subcutaneous/intramuscular, and visceral (most commonly the spleen). Dogs and cats with HSA generally have a poor prognosis owing to the rapid and widespread metastasis typically associated with this disease. However, some forms such as cutaneous HSA behave in a less aggressive fashion with improved outcomes. Surgical excision and anthracycline-based chemotherapy remain the mainstays of treatment, although novel treatment modalities are currently under investigation for potential roles in treatment of this disease.

CONCLUSION

This review aims to describe the clinical presentation and progression of the various forms of HSA in dogs and cats as well as to provide a systematic review of the veterinary literature with a focus on the various published treatment options and associated outcomes.

A Multi-Institutional Retrospective Analysis of Toceranib Phosphate for Presumed or Confirmed Canine Aortic Body Chemodectomas

Aortic body tumors, specifically chemodectomas, are the second most common type of canine cardiac tumor; however, information about treatment is currently lacking. This study included dogs with a presumptive or definitive diagnosis of an aortic body chemodectoma that underwent treatment with toceranib phosphate. Cases were solicited via the American College of Veterinary Internal Medicine Cardiology, Internal Medicine, and Oncology listservs using an electronic survey. Cox multivariate analysis of factors potentially impacting survival time was completed. Twenty-seven (27) cases were included in analysis. The clinical benefit rate (complete remission, partial remission, or stable disease >10 weeks) was 89%. A median survival time of 478 days was found for those receiving toceranib alone (n = 14), which was not statistically different from those treated with additional modalities (521 days). No factors evaluated statistically impacted outcome. Further, prospective studies are warranted to evaluate the use of toceranib for the treatment of canine aortic body chemodectomas.

Propranolol Sensitizes Vascular Sarcoma Cells to Doxorubicin by Altering Lysosomal Drug Sequestration and Drug Efflux

Angiosarcoma is a rare cancer of blood vessel-forming cells with a high patient mortality and few treatment options. Although chemotherapy often produces initial clinical responses, outcomes remain poor, largely due to the development of drug resistance. We previously identified a subset of doxorubicin-resistant cells in human angiosarcoma and canine hemangiosarcoma cell lines that exhibit high lysosomal accumulation of doxorubicin. Hydrophobic, weak base chemotherapeutics, like doxorubicin, are known to sequester within lysosomes, promoting resistance by limiting drug accessibility to cellular targets. Drug synergy between the beta adrenergic receptor (β-AR) antagonist, propranolol, and multiple chemotherapeutics has been documented in vitro, and clinical data have corroborated the increased therapeutic potential of propranolol with chemotherapy in angiosarcoma patients. Because propranolol is also a weak base and accumulates in lysosomes, we sought to determine whether propranolol enhanced doxorubicin cytotoxicity via antagonism of β-ARs or by preventing the lysosomal accumulation of doxorubicin. β-AR-like immunoreactivities were confirmed in primary tumor tissues and cell lines; receptor function was verified by monitoring downstream signaling pathways of β-ARs in response to receptor agonists and antagonists. Mechanistically, propranolol increased cytoplasmic doxorubicin concentrations in sarcoma cells by decreasing the lysosomal accumulation and cellular efflux of this chemotherapeutic agent. Equivalent concentrations of the receptor-active S-(-) and -inactive R-(+) enantiomers of propranolol produced similar effects, supporting a β-AR-independent mechanism. Long-term exposure of hemangiosarcoma cells to propranolol expanded both lysosomal size and number, yet cells remained sensitive to doxorubicin in the presence of propranolol. In contrast, removal of propranolol increased cellular resistance to doxorubicin, underscoring lysosomal doxorubicin sequestration as a key mechanism of resistance. Our results support the repurposing of the R-(+) enantiomer of propranolol with weak base chemotherapeutics to increase cytotoxicity and reduce the development of drug-resistant cell populations without the cardiovascular and other side effects associated with antagonism of β-ARs.

Evaluation of an autologous cancer vaccine for the treatment of metastatic canine hemangiosarcoma: a preliminary study

Background

Canine hemangiosarcoma (HSA) is an aggressive cancer arising from multipotential bone marrow-derived stem cells. Anthracycline chemotherapy drugs have been the mainstay adjuvant chemotherapy following surgery with only modest improvement in survival and an attendant risk for adverse events. Immunotherapy, using a whole cell autologous cancer vaccine adjuvanted with MIM-SIS, may improve outcomes for dogs with HSA with a lower risk for adverse events compared with chemotherapy.

Results

In cultured DH82 canine monocyte-like cells, autologous cancer vaccines prepared from 13 dogs with HSA increased MHC-II surface expression ranging from 20.0-60.4% on single-stained cells, CD80 surface expression ranging from 23.7–45.9% on single-stained cells, and MHC-II/CD80 surface expression ranging from 7.2–20.1% on double-stained cells. Autologous cancer vaccines were able to, on average, stimulate an up-regulation of MHC-II and CD80 by 48-fold as compared to media only (MHC-II + CD80 + cells: 12.19 ± 3.70% vs. 0.25 ± 0.06%; p < 0.001). The overall median survival time for dogs treated with the autologous cancer vaccine was 142 days (range, 61 to 373 days). Dogs treated with the autologous cancer vaccine or maximum tolerated dose (MTD) chemotherapy had significantly (P < 0.001) longer survival than dogs treated with surgery alone. The 1-year survival rate was 12.5% for dogs treated with the autologous cancer vaccine, and 0% for dogs treated with surgery alone or MTD chemotherapy. No adverse events were observed in the dogs treated with the autologous cancer vaccine.

Conclusions

The adjuvanted autologous cancer vaccine is capable of up-regulating MHC-II and CD80 in cultured canine monocyte-derived cells, which are important stimulatory molecules in generating an immune response and improves survival time in dogs with metastatic (stage III) HSA when compared to surgical treatment alone. Autologous cancer vaccine-treated dogs had survival similar to those dogs treated with MTD chemotherapy without any observed adverse events. This autologous cancer vaccine represents an effective form of individualized immunotherapy that is an appealing option for dog owners not wanting to pursue adjuvant chemotherapy for HSA.

Impact of repeated cycles of EGF bispecific angiotoxin (eBAT) administered at a reduced interval from doxorubicin chemotherapy in dogs with splenic haemangiosarcoma

We previously reported that eBAT, an EGF-targeted angiotoxin, was safe and it improved the overall survival for dogs with splenic haemangiosarcoma when added to the standard of care in a single cycle of three administrations in the minimal residual disease setting. Our objective for the SRCBST-2 trial was to assess whether increased dosing through multiple cycles of eBAT would be well tolerated and would further enhance the benefits of eBAT. Eligibility was expanded to dogs with stage 3 haemangiosarcoma, provided that gross lesions could be surgically excised. The interval between eBAT and the start of chemotherapy was reduced, and the experimental therapy was expanded to three cycles, each administered at the biologically active dose (50 μg/kg) on a Monday/Wednesday/Friday schedule following splenectomy, and scheduled 1 week prior to the first, second and fifth doxorubicin chemotherapy. Twenty-five dogs were enrolled; six experienced acute hypotension with two requiring hospitalization. Self-limiting elevation of ALT was observed in one dog. A statistically significant survival benefit was not seen in this study in eBAT-treated dogs compared with a Contemporary comparison group of dogs with stages 1-3 haemangiosarcoma treated with standard of care alone. Our results indicate that repeated dosing cycles of eBAT starting 1 week prior to doxorubicin chemotherapy led to greater toxicity and reduced efficacy compared with a single cycle given between surgery and a delayed start of chemotherapy. Further work is needed to understand the precise mechanisms of action of eBAT in order to optimize its clinical benefits in the treatment of canine haemangiosarcoma and other tumours. IACUC Protocols 1110A06186 and 1507-32804A.

Toceranib phosphate in the treatment of canine thyroid carcinoma: 42 cases (2009-2018)

Thyroid carcinoma is the most common endocrine malignancy in dogs. Thyroidectomy and radiation therapy control local disease, yet are not always feasible, and efficacious medical therapies need to be identified. Toceranib phosphate has been reported to provide clinical benefit (CB) in dogs with thyroid carcinoma, while its role in treatment-naïve thyroid tumours has not been well-described. The objective of this study was to describe the use of toceranib in the management of thyroid carcinomas in dogs in both the naïve-disease and prior therapy- settings. A medical record search identified 42 dogs diagnosed with thyroid carcinoma and treated with toceranib, of which 26 and 16 dogs were in settings of naïve-disease and after prior therapy, respectively. Twenty-three (88.4%) and twelve (75%) dogs experienced CB in the naïve and prior therapy settings, respectively. The median [95% confidence interval] progression free interval (PFI) for dogs in the naïve and prior therapy settings were 206 [106,740] and 1015 [92,1015] days, respectively. The median overall survival time (OST) for dogs in the naïve and prior therapy settings were 563 [246,916] and 1082 [289,1894] days, respectively. Overall, the data provided no evidence for differences in overall PFI (P > .20) or OST (P = .15) between settings. However, when asymptomatic at the time of diagnosis, dogs in the naïve setting showed poorer survival prognosis (estimated hazard ratio 17.2 [1.8, 163]) relative to dogs in the prior therapy setting. This study characterizes PFI, OST and CB with minimal AE in dogs with thyroid carcinoma treated with toceranib in both the naïve and prior therapy settings.

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

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

Emerging therapeutic approaches for canine sarcomas: Pushing the boundaries beyond the conventional

Sarcomas represent a group of genomically chaotic, highly heterogenous tumours of mesenchymal origin with variable mutational load. Conventional therapy with surgery and radiation therapy is effective for managing small, low-grade sarcomas and remains the standard therapeutic approach. For advanced, high-grade, recurrent, or metastatic sarcomas, systemic chemotherapy provides minimal benefit, therefore, there is a drive to develop novel approaches. The discovery of "Coley's toxins" in the 19th century, and their use to stimulate the immune system supported the application of unconventional therapies for the treatment of sarcomas. While promising, this initial work was abandoned and treatment paradigm and disease course of sarcomas was largely unchanged for several decades. Exciting new therapies are currently changing treatment algorithms for advanced carcinomas and melanomas, and similar approaches are being applied to advance the field of sarcoma research. Recent discoveries in subtype-specific cancer biology and the identification of distinct molecular targets have led to the development of promising targeted strategies with remarkable potential to change the landscape of sarcoma therapy in dogs. The purpose of this review article is to describe the current standard of care and limitations as well as emerging approaches for sarcoma therapy that span many of the most active paradigms in oncologic research, including immunotherapies, checkpoint inhibitors, and drugs capable of cellular metabolic reprogramming.

Comparative Genomics Reveals Shared Mutational Landscape in Canine Hemangiosarcoma and Human Angiosarcoma

Angiosarcoma is a highly aggressive cancer of blood vessel-forming cells with few effective treatment options and high patient mortality. It is both rare and heterogenous, making large, well-powered genomic studies nearly impossible. Dogs commonly suffer from a similar cancer, called hemangiosarcoma, with breeds like the golden retriever carrying heritable genetic factors that put them at high risk. If the clinical similarity of canine hemangiosarcoma and human angiosarcoma reflects shared genomic etiology, dogs could be a critically needed model for advancing angiosarcoma research. We assessed the genomic landscape of canine hemangiosarcoma via whole-exome sequencing (47 golden retriever hemangiosarcomas) and RNA sequencing (74 hemangiosarcomas from multiple breeds). Somatic coding mutations occurred most frequently in the tumor suppressor TP53 (59.6% of cases) as well as two genes in the PI3K pathway: the oncogene PIK3CA (29.8%) and its regulatory subunit PIK3R1 (8.5%). The predominant mutational signature was the age-associated deamination of cytosine to thymine. As reported in human angiosarcoma, CDKN2A/B was recurrently deleted and VEGFA, KDR, and KIT recurrently gained. We compared the canine data to human data recently released by The Angiosarcoma Project, and found many of the same genes and pathways significantly enriched for somatic mutations, particularly in breast and visceral angiosarcomas. Canine hemangiosarcoma closely models the genomic landscape of human angiosarcoma of the breast and viscera, and is a powerful tool for investigating the pathogenesis of this devastating disease. IMPLICATIONS: We characterize the genomic landscape of canine hemangiosarcoma and demonstrate its similarity to human angiosarcoma.

Targeted Therapies in Veterinary Oncology

Advances in molecular biology have permitted a much more detailed understanding of cellular dysfunction at the molecular and genetic levels in cancer cells. This has resulted in the identification of novel targets for therapeutic intervention, including proteins that regulate signal transduction, gene expression, and protein turnover. In many instances, small molecules are used to disrupt the function of these targets, often through competitive inhibition of ATP binding or the prevention of necessary protein-protein interactions. More than 40 small molecule inhibitors are now approved to treat a variety of human cancers, substantially impacting patient outcomes.

Histiocytic Sarcoma and Hemangiosarcoma Update

Histiocytic sarcoma (HS) and hemangiosarcoma (HSA) are uncommon and aggressive neoplasms that develop much more frequently in dogs than in cats. Breed-specific predispositions have been identified for both cancers. The development of novel diagnostics is underway and may aid in earlier diagnosis. Therapeutic approaches to HS and HSA depend on the stage of disease and may include surgery, radiation therapy, and chemotherapy. Such interventions improve outcome; however, aside from a small number of clinical circumstances, both diseases are considered largely incurable. Continued efforts toward the identification of driver mutations and subsequent druggable targets may lead to improvements in long-term prognosis.

In vitro effects of the chemotherapy agent water-soluble micellar paclitaxel (Paccal Vet) on canine hemangiosarcoma cell lines

Paccal Vet (Osamia Pharmaceuticals) is a water-soluble nanoparticle micellar formulation of the drug paclitaxel that is well tolerated in dogs. This study evaluated the in vitro effect of Paccal Vet on two canine hemangiosarcoma (HSA) cell lines and their expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Paccal Vet caused HSA cell death in a dose- and time-dependent manner. The 50% inhibitory concentration (IC₅₀ ) for the two HSA cell lines were 7 to 610 ng/mL, which are clinically achievable. Cell cycle analysis through flow cytometry showed cell cycle arrest at G2/M phase. Annexin-V and caspase 3/7 activity assays showed significant increases in apoptosis in correlation with the IC₅₀ in each cell line. Reverse transcriptase-PCR was performed on the cell lines to validate the gene expression of VEGF and bFGF. Results obtained from this study support future studies involving the use of paclitaxel (micellar) for treatment of canine HSA.

The addition of metronomic chemotherapy does not improve outcome for canine splenic haemangiosarcoma

OBJECTIVES

To determine whether the addition of metronomic chemotherapy improved outcome for dogs with splenic haemangiosarcoma treated with splenectomy and adjuvant maximum tolerated dose chemotherapy.

MATERIALS AND METHODS

Medical records were examined retrospectively for dogs with splenic haemangiosarcoma that had undergone splenectomy followed by anthracycline-based chemotherapy. Thirty-nine dogs underwent splenectomy followed by maximum tolerated dose chemotherapy with an anthracycline, cyclophosphamide, or both (Group 1). Twenty-two dogs underwent splenectomy followed by adjuvant maximum tolerated dose chemotherapy with an anthracycline, cyclophosphamide, or both, plus metronomic chemotherapy (Group 2). Dogs in both groups were further separated into those treated with either maximum tolerated dose anthracycline or maximum tolerated dose anthracycline and cyclophosphamide.

RESULTS

Median progression-free survival was 165 days and median overall survival time was 180 days in Group 1. Median progression-free survival was 185 days and median overall survival time was 212 days in Group 2. In both groups, the overall survival was shorter in dogs that had received maximum tolerated dose cyclophosphamide.

CLINICAL SIGNIFICANCE

The addition of metronomic to maximum tolerated dose chemotherapy protocols does not appear to improve outcome in dogs with splenic haemangiosarcoma treated with splenectomy and maximum tolerated dose chemotherapy.

Canine visceral hemangiosarcoma treated with surgery alone or surgery and doxorubicin: 37 cases (2005-2014)

The purpose of this retrospective study was to determine survival times and prognostic factors of dogs with visceral hemangiosarcoma (HSA) treated with surgery alone or surgery and doxorubicin. Medical records from 2 hospitals from 2005 to 2014 were searched for dogs with histopathologically confirmed visceral HSA. Data relevant to patient demographics, tumor characteristics, and outcomes were abstracted. The most common primary organ affected was the spleen; however, primary tumor location had no influence on prognosis. Twenty-three dogs were treated with surgery alone, while 14 dogs were treated with surgery and doxorubicin. There was a significant difference in survival times between dogs treated with surgery alone and with surgery followed by doxorubicin (66 days versus 274 days). Dogs with stage I tumors (196 days) had a longer median survival time (MST) than dogs with stage II (117 days) and stage III (23 days) disease. The overall MST was 179 days with a 1-year survival rate of 29.2%.

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.

Update on Cancer Treatment in Exotics

Treatment options for animals with cancer are rapidly expanding, including in exotic animal medicine. Limited information is available about treatment effects in exotic pet species beyond individual case reports. Most cancer treatment protocols in exotic animals are extrapolated from those described in humans, dogs, and cats. This review provides an update on cancer treatment in exotic animal species. The Exotic Species Cancer Research Alliance accumulates clinical cases in a central location with standardized clinical information, with resources to help clinicians find and enter their cases for the collective good of exotic clinicians and their patients.

Does thalidomide prolong survival in dogs with splenic haemangiosarcoma?

OBJECTIVES

To investigate thalidomide as an adjuvant treatment for canine haemangiosarcoma.

MATERIALS AND METHODS

Fifteen dogs with splenic haemangiosarcoma, initially treated by splenectomy, were included. Following recovery from surgery, all dogs received thalidomide continuously until their death. Tumour stage was established using CT scans of the chest and abdomen immediately before starting thalidomide treatment and again three months later. Cause of death was confirmed by post mortem examination.

RESULTS

The median survival time of dogs receiving thalidomide was 172 days (95% confidence interval: 93 to 250 days). Five dogs (33% of the population receiving thalidomide) survived more than 1 year (range 458 to 660 days) after surgery. Dogs with stage 2 disease that received thalidomide also had a longer survival time than dogs with stage 3 disease (median survival time 303 versus 40 days). Of 15 dogs, 13 died from metastatic haemangiosarcoma.

CLINICAL SIGNIFICANCE

Treatment using thalidomide may improve survival of dogs with splenic haemangiosarcoma and should be considered a possible adjuvant therapy.

Safe and Effective Sarcoma Therapy through Bispecific Targeting of EGFR and uPAR

Sarcomas differ from carcinomas in their mesenchymal origin. Therapeutic advancements have come slowly, so alternative drugs and models are urgently needed. These studies report a new drug for sarcomas that simultaneously targets both tumor and tumor neovasculature. eBAT is a bispecific angiotoxin consisting of truncated, deimmunized Pseudomonas exotoxin fused to EGF and the amino terminal fragment of urokinase. Here, we study the drug in an in vivo "ontarget" companion dog trial as eBAT effectively kills canine hemangiosarcoma and human sarcoma cells in vitro We reasoned the model has value due to the common occurrence of spontaneous sarcomas in dogs and a limited lifespan allowing for rapid accrual and data collection. Splenectomized dogs with minimal residual disease were given one cycle of eBAT followed by adjuvant doxorubicin in an adaptive dose-finding, phase I-II study of 23 dogs with spontaneous, stage I-II, splenic hemangiosarcoma. eBAT improved 6-month survival from <40% in a comparison population to approximately 70% in dogs treated at a biologically active dose (50 μg/kg). Six dogs were long-term survivors, living >450 days. eBAT abated expected toxicity associated with EGFR targeting, a finding supported by mouse studies. Urokinase plasminogen activator receptor and EGFR are targets for human sarcomas, so thorough evaluation is crucial for validation of the dog model. Thus, we validated these markers for human sarcoma targeting in the study of 212 human and 97 canine sarcoma samples. Our results support further translation of eBAT for human patients with sarcomas and perhaps other EGFR-expressing malignancies. Mol Cancer Ther; 16(5); 956-65. ©2017 AACR.

Evaluation of 18-F-fluoro-2-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) as a staging and monitoring tool for dogs with stage-2 splenic hemangiosarcoma - A pilot study

Positron Emission Tomography-Computed Tomography (PET-CT) is routinely used for staging and monitoring of human cancer patients and is becoming increasingly available in veterinary medicine. In this study, 18-fluorodeoxyglucose (18FDG)-PET-CT was used in dogs with naturally occurring splenic hemangiosarcoma (HSA) to assess its utility as a staging and monitoring modality as compared to standard radiography and ultrasonography. Nine dogs with stage-2 HSA underwent 18FDG-PET-CT following splenectomy and prior to commencement of chemotherapy. Routine staging (thoracic radiography and abdominal ultrasonography) was performed prior to 18FDG-PET-CT in all dogs. When abnormalities not identified on routine tests were noted on 18FDG-PET-CT, owners were given the option to repeat a PET-CT following treatment with eBAT. A PET-CT scan was repeated on Day 21 in three dogs. Abnormalities not observed on conventional staging tools, and most consistent with malignant disease based on location, appearance, and outcome, were detected in two dogs and included a right atrial mass and a hepatic nodule, respectively. These lesions were larger and had higher metabolic activity on the second scans. 18FDG-PET-CT has potential to provide important prognostic information and influence treatment recommendations for dogs with stage-2 HSA. Additional studies will be needed to precisely define the value of this imaging tool for staging and therapy monitoring in dogs with this and other cancers.

Magnetic resonance imaging and immunohistochemistry of primary vertebral hemangiosarcoma in a dog and implications for diagnosis and therapy

A vertebral mass in a dog with an acute onset paraparesis was identified by magnetic resonance imaging. A poorly differentiated hemangiosarcoma was diagnosed by histopathology and immunohistochemistry. Endothelial nitric oxide synthase could be a new differential marker for poorly differentiated hemangiosarcoma in dogs. Immunohistochemical detection of p53 phosphorylated at Serine³⁹², p53, CD117, and CD44 suggest targets for design of therapeutic strategies.

Effects of inhibitors of vascular endothelial growth factor receptor 2 and downstream pathways of receptor tyrosine kinases involving phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin or mitogen-activated protein kinase in canine hemangiosarcoma cell lines

Canine hemangiosarcoma (HSA) is a progressive malignant neoplasm with no current effective treatment. Previous studies showed that receptor tyrosine kinases and molecules within their downstream pathways involving phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (m-TOR) or mitogen-activated protein kinase (MAPK) were overexpressed in canine, human, and murine tumors, including HSA. The present study investigated the effects of inhibitors of these pathways in canine splenic and hepatic HSA cell lines using assays of cell viability and apoptosis. Inhibitors of the MAPK pathway did not affect canine HSA cell viability. However, cell viability was significantly reduced by exposure to inhibitors of vascular endothelial growth factor receptor 2 and the PI3K/Akt/m-TOR pathway; these inhibitors also induced apoptosis in these cell lines. These results suggest that these inhibitors reduce the proliferation of canine HSA cells by inducing apoptosis. Further study of these inhibitors, using xenograft mouse models of canine HSA, are warranted to explore their potential for clinical application.

A retrospective analysis of chemotherapy switch suggests improved outcome in surgically removed, biologically aggressive canine haemangiosarcoma

Haemangiosarcoma (HSA) has an aggressive biological behaviour and carries a poor prognosis, with less than 10% of treated dogs surviving longer than 1 year. In this retrospective study a varied metronomic chemotherapy (MC) regimen preceded by adjuvant doxorubicin-based maximum-tolerated dose chemotherapy (MTDC) was compared with MTDC, in terms of efficacy [time to metastasis, (TTM) and survival time (ST)] and safety in dogs with biologically aggressive HSA. Dogs were eligible if they had no metastasis after MTDC and received either no further chemotherapy or MC maintenance. Twelve dogs received MTDC, and 10 received MC thereafter. Median TTM and ST were significantly longer for dogs receiving MTDC-MC (not reached versus 150 days, P = 0.028; and not reached versus 168 days, P = 0.030, respectively). Treatment was well tolerated. MTDC followed by MC is safe and suggests improved TTM and ST in dogs with surgically removed, biologically aggressive HSA that are treated in the microscopic setting.