Background We have previously shown that radiotherapy (RT) augments natural killer (NK) functions in pre-clinical models of human and mouse cancers, including sarcomas. Since dogs are an excellent outbred model for immunotherapy studies, we sought to assess RT plus local autologous NK transfer in canine sarcomas. Methods Dog NK cells (CD5^dim, NKp46+) were isolated from PBMCs and expanded with irradiated K562-C9-mIL21 feeder cells and 100 IU/mL recombinant human IL-2. NK homing and cytotoxicity ± RT were evaluated using canine osteosarcoma tumor lines and dog patient-derived xenografts (PDX). In a first-in-dog clinical trial for spontaneous osteosarcoma, we evaluated RT and intra-tumoral autologous NK transfer. Results After 14 days, mean NK expansion and yield were 19.0-fold (±8.6) and 258.9(±76.1) ×10⁶ cells, respectively. Post-RT, NK cytotoxicity increased in a dose-dependent fashion in vitro reaching ~ 80% at effector:target ratios of ≥10:1 (P < 0.001). In dog PDX models, allogeneic NK cells were cytotoxic in ex vivo killing assays and produced significant PDX tumor growth delay (P < 0.01) in vivo. After focal RT and intravenous NK transfer, we also observed significantly increased NK homing to tumors in vivo. Of 10 dogs with spontaneous osteosarcoma treated with focal RT and autologous NK transfer, 5 remain metastasis-free at the 6-month primary endpoint with resolution of suspicious pulmonary nodules in one patient. We also observed increased activation of circulating NK cells after treatment and persistence of labelled NK cells in vivo. Conclusions NK cell homing and cytotoxicity are increased following RT in canine models of sarcoma. Results from a first-in-dog clinical trial are promising, including possible abscopal effects.

Despite recent major clinical breakthroughs in human cancer immunotherapy including the use of checkpoint inhibitors and engineered T cells, important challenges remain, including determining the sub-populations of patients who will respond and who will experience at times significant toxicities. Although advances in cancer immunotherapy depend on preclinical testing, the majority of in-vivo testing currently relies on genetically identical inbred mouse models which, while offering critical insights regarding efficacy and mechanism of action, also vastly underrepresent the heterogeneity and complex interplay of human immune cells and cancers. Additionally, laboratory mice uncommonly develop spontaneous tumors, are housed under specific-pathogen free conditions which markedly impacts immune development, and incompletely model key aspects of the tumor/immune microenvironment. The canine model represents a powerful tool in cancer immunotherapy research as an important link between murine models and human clinical studies. Dogs represent an attractive outbred combination of companion animals that experience spontaneous cancer development in the setting of an intact immune system. This allows for study of complex immune interactions during the course of treatment while also directly addressing long-term efficacy and toxicity of cancer immunotherapies. However, immune dissection requires access to robust and validated immune assays and reagents as well as appropriate numbers for statistical evaluation. Canine studies will need further optimization of these important mechanistic tools for this model to fulfill its promise as a model for immunotherapy. This review aims to discuss the canine model in the context of existing preclinical cancer immunotherapy models to evaluate both its advantages and limitations, as well as highlighting its growth as a powerful tool in the burgeoning field of both human and veterinary immunotherapy.

Objective—To describe the clinical signs, physical examination findings, clinical laboratory abnormalities, etiology, and outcome in cats with spontaneous hemoperitoneum. Design—Retrospective case series. Animals—65 client-owned cats with spontaneous hemoperitoneum. Procedures—Medical records of cats with spontaneous hemoperitoneum at 7 large referral clinics were reviewed. Cats were included if a definitive diagnosis of spontaneous hemoperitoneum could be obtained from review of the medical records. Results—65 cats met inclusion criteria. The most common historical findings were lethargy, anorexia, and vomiting. Common findings on physical examination included inadequate hydration status and hypothermia. The most common clinicopathologic abnormalities were high serum AST activity, anemia, prolonged prothrombin time, and prolonged partial thromboplastin time. Forty-six percent (30/65) of cats had abdominal neoplasia, and 54% (35/65) had nonneoplastic conditions. Hemangiosarcoma was the most often diagnosed neoplasm (18/30; 60%), and the spleen was the most common location for neoplasia (11/30; 37%). Eight cats survived to be discharged from the hospital. Cats with neoplasia were significantly older and had significantly lower PCVs than cats with non-neoplastic disease. Conclusions and Clinical Relevance—Spontaneous hemoperitoneum in cats often results in debilitating clinical consequences. In contrast to dogs with hemoperitoneum, the cause of hemoperitoneum in cats is approximately evenly distributed between neoplastic and nonneoplastic diseases. Although only a few cats were treated in this study, the prognosis appears poor.

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.

Objective—To evaluate clinical characteristics, outcome, and prognostic variables in a cohort of dogs surviving > 1 year after an initial diagnosis of osteosarcoma. Design—Retrospective case series. Animals—90 client-owned dogs. Procedures—Medical records for an 11-year period from 1997 through 2008 were reviewed, and patients with appendicular osteosarcoma that lived > 1 year after initial histopathologic diagnosis were studied. Variables including signalment, weight, serum alkaline phosphatase activity, tumor location, surgery, and adjuvant therapies were recorded. Median survival times were calculated by means of a Kaplan-Meier survival function. Univariate analysis was conducted to compare the survival function for categorical variables, and the Cox proportional hazard model was used to evaluate the likelihood of death > 1 year after diagnosis on the basis of the selected risk factors. Results—90 dogs met the inclusion criteria; clinical laboratory information was not available in all cases. Median age was 8.2 years (range, 2.7 to 13.3 years), and median weight was 38 kg (83.6 lb; range, 21 to 80 kg [46.2 to 176 lb]). Serum alkaline phosphatase activity was high in 29 of 60 (48%) dogs. The most common tumor location was the distal portion of the radius (54/90 [60%]). Eighty-nine of 90 (99%) dogs underwent surgery, and 78 (87%) received chemotherapy. Overall, 49 of 90 (54%) dogs developed metastatic disease. The median survival time beyond 1 year was 243 days (range, 1 to 1,899 days). Dogs that developed a surgical-site infection after limb-sparing surgery had a significantly improved prognosis > 1 year after osteosarcoma diagnosis, compared with dogs that did not develop infections. Conclusions and Clinical Relevance—Results of the present study indicated that dogs with an initial diagnosis of osteosarcoma that lived > 1 year had a median survival time beyond the initial year of approximately 8 months. As reported previously, the development of a surgical-site infection in dogs undergoing a limb-sparing surgery significantly affected prognosis and warrants further study.