Establishing a model system for evaluating CAR T cell therapy using dogs with spontaneous diffuse large B cell lymphoma

Translational History and Hope of Immunotherapy of Canine Tumors

Companion dogs have served an important role in cancer immunotherapy research. Sharing similar environments and diets with humans, dogs naturally develop many of the same cancers. These shared exposures, coupled with dogs' diverse genetic makeup, make them ideal subjects for studying cancer therapies. Tumors like osteosarcoma, hemangiosarcoma, soft-tissue sarcoma, and non-Hodgkin lymphoma occur with greater frequency than their counterpart disease in humans. Canine brain tumors allow the study of therapy strategies with imaging, surgery, and radiotherapy equipment in veterinary patients with near-human geometry. Nonspecific immunostimulants, autologous and allogeneic vaccines, immune checkpoint inhibitors, and cellular therapies used in treating canine cancers have been tested in veterinary clinical trials. These treatments have not only improved outcomes for dogs but have also provided valuable insights for human cancer treatment. Advancements in radiation technology and the development of tools to characterize canine immune responses have further facilitated the ability to translate veterinary clinical trial results to human applications. Advancements in immunotherapy of canine tumors have directly supported translation to human clinical trials leading to approved therapies for patients with cancer around the world. The study of immunotherapy in dogs has been and will continue to be a promising avenue for advancing human cancer treatment.

Leveraging single-cell transcriptomic data to uncover immune suppressive cancer cell subsets in triple-negative canine breast cancers

Introduction

Single-cell RNA sequencing (scRNA-seq) has become an essential tool for uncovering the complexities of various physiological and immunopathological conditions in veterinary medicine. However, there is currently limited information on immune-suppressive cancer subsets in canine breast cancers. In this study, we aimed to identify and characterize immune-suppressive subsets of triple-negative canine breast cancer (TNBC) by utilizing integrated scRNA-seq data from published datasets.

Methods

Published scRNA-seq datasets, including data from six groups of 30 dogs, were subjected to integrated bioinformatic analysis.

Results

Immune modulatory TNBC subsets were identified through functional enrichment analysis using immune-suppressive gene sets, including those associated with anti-inflammatory and M2-like macrophages. Key immune-suppressive signaling, such as viral infection, angiogenesis, and leukocyte chemotaxis, was found to play a role in enabling TNBC to evade immune surveillance. In addition, interactome analysis revealed significant interactions between distinct subsets of cancer cells and effector T cells, suggesting potential T-cell suppression.

Discussion

The present study demonstrates a versatile and scalable approach to integrating and analyzing scRNA-seq data, which successfully identified immune-modulatory subsets of canine TNBC. It also revealed potential mechanisms through which TNBC promotes immune evasion in dogs. These findings are crucial for advancing the understanding of the immune pathogenesis of canine TNBC and may aid in the development of new immune-based therapeutic strategies.

Validation of a PD-1/CD28 chimeric switch receptor to augment CAR-T function in dogs with spontaneous B cell lymphoma

Chimeric antigen receptor (CAR) T cell therapy has achieved unprecedented clinical outcomes in patients with relapsed/refractory B cell leukemias; however, response rates in patients with large B cell lymphoma (LBCL) are less impressive. Expression of PD-1 on activated T cells and PD-L1 on malignant, stromal, and immune cells within the tumor microenvironment (TME) contribute to CAR-T exhaustion, hypofunction, and treatment failures. Here, a comparative approach is taken to develop a chimeric switch receptor (CSR) with potential to augment CAR-T persistence, function, and clinical efficacy in immune competent, pet dogs with spontaneous B cell lymphoma (BCL). We show that similar to human CAR-T cells, expression of a PD-1/CD28 CSR in canine CAR-T cells results in enhanced function against PD-L1+ targets and preserves central memory phenotype. We also demonstrate that these effects depend upon active CSR signaling. This work paves the way for in vivo studies in canine BCL patients to inform human trial design.

Pre-Clinical Models for CAR T-Cell Therapy for Glioma

Immunotherapy represents a transformative shift in cancer treatment. Among myriad immune-based approaches, chimeric antigen receptor (CAR) T-cell therapy has shown promising results in treating hematological malignancies. Despite aggressive treatment options, the prognosis for patients with malignant brain tumors remains poor. Research leveraging CAR T-cell therapy for brain tumors has surged in recent years. Pre-clinical models are crucial in evaluating the safety and efficacy of these therapies before they advance to clinical trials. However, current models recapitulate the human tumor environment to varying degrees. Novel in vitro and in vivo techniques offer the opportunity to validate CAR T-cell therapies but also have limitations. By evaluating the strengths and weaknesses of various pre-clinical glioma models, this review aims to provide a roadmap for the development and pre-clinical testing of CAR T-cell therapies for brain tumors.

Applications and Opportunities for Immune Cell CAR Engineering in Comparative Oncology

Chimeric antigen receptor (CAR) T-adoptive cell therapy has transformed the treatment of human hematologic malignancies. However, its application for the treatment of solid tumors remains challenging. An exciting avenue for advancing this field lies in the use of pet dogs, in which cancers that recapitulate the biology, immunological features, and clinical course of human malignancies arise spontaneously. Moreover, their large size, outbred genetic background, shared environment with humans, and immunocompetency make dogs ideal for investigating and optimizing CAR therapies before human trials. Here, we will outline how challenges in early clinical trials in patients with canine lymphoma, including issues related to autologous CAR T-cell manufacturing, limited CAR T-cell persistence, and tumor antigen escape, mirrored challenges observed in human CAR T trials. We will then highlight emerging adoptive cell therapy strategies currently under investigation in dogs with hematological and solid cancers, which will provide crucial safety and efficacy data on novel CAR T regimens that can be used to support clinical trials. By drawing from ongoing studies, we will illustrate how canine patients with spontaneous cancer may serve as compelling screening platforms to establish innovative CAR therapy approaches and identify predictive biomarkers of response, with a specific emphasis on solid tumors. With increased funding for canine immunotherapy studies, multi-institutional investigations are poised to generate highly impactful clinical data that should translate into more effective human trials, ultimately benefiting both human and canine cancer patients.

Breaking barriers in trauma research: A narrative review of opportunities to leverage veterinary trauma for accelerated translation to clinical solutions for pets and people

Trauma is a common cause of morbidity and mortality in humans and companion animals. Recent efforts in procedural development, training, quality systems, data collection, and research have positively impacted patient outcomes; however, significant unmet need still exists. Coordinated efforts by collaborative, translational, multidisciplinary teams to advance trauma care and improve outcomes have the potential to benefit both human and veterinary patient populations. Strategic use of veterinary clinical trials informed by expertise along the research spectrum (i.e., benchtop discovery, applied science and engineering, large laboratory animal models, clinical veterinary studies, and human randomized trials) can lead to increased therapeutic options for animals while accelerating and enhancing translation by providing early data to reduce the cost and the risk of failed human clinical trials. Active topics of collaboration across the translational continuum include advancements in resuscitation (including austere environments), acute traumatic coagulopathy, trauma-induced coagulopathy, traumatic brain injury, systems biology, and trauma immunology. Mechanisms to improve funding and support innovative team science approaches to current problems in trauma care can accelerate needed, sustainable, and impactful progress in the field. This review article summarizes our current understanding of veterinary and human trauma, thereby identifying knowledge gaps and opportunities for collaborative, translational research to improve multispecies outcomes. This translational trauma group of MDs, PhDs, and DVMs posit that a common understanding of injury patterns and resulting cellular dysregulation in humans and companion animals has the potential to accelerate translation of research findings into clinical solutions.

Targeting osteosarcoma with canine B7-H3 CAR T cells and impact of CXCR2 Co-expression on functional activity

The use of large animal spontaneous models of solid cancers, such as dogs with osteosarcoma (OS), can help develop new cancer immunotherapy approaches, including chimeric antigen receptor (CAR) T cells. The goal of the present study was to generate canine CAR T cells targeting the B7-H3 (CD276) co-stimulatory molecule overexpressed by several solid cancers, including OS in both humans and dogs, and to assess their ability to recognize B7-H3 expressed by canine OS cell lines or by canine tumors in xenograft models. A second objective was to determine whether a novel dual CAR that expressed a chemokine receptor together with the B7-H3 CAR improved the activity of the canine CAR T cells. Therefore, in the studies reported here we examined B7-H3 expression by canine OS tumors, evaluated target engagement by canine B7-H3 CAR T cells in vitro, and compared the relative effectiveness of B7-H3 CAR T cells versus B7-H3-CXCR2 dual CAR T cells in canine xenograft models. We found that most canine OS tumors expressed B7-H3; whereas, levels were undetectable on normal dog tissues. Both B7-H3 CAR T cells demonstrated activation and OS-specific target killing in vitro, but there was significantly greater cytokine production by B7-H3-CXCR2 CAR T cells. In canine OS xenograft models, little anti-tumor activity was generated by B7-H3 CAR T cells; whereas, B7-H3-CXCR2 CAR T cells significantly inhibited tumor growth, inducing complete tumor elimination in most treated mice. These findings indicated therefore that addition of a chemokine receptor could significantly improve the anti-tumor activity of canine B7-H3 CAR T cells, and that evaluation of this new dual CAR construct in dogs with primary or metastatic OS is warranted since such studies could provide a critical and realistic validation of the chemokine receptor concept.

Direct comparison of canine and human immune responses using transcriptomic and functional analyses

The canine spontaneous cancer model is increasingly utilized to evaluate new combined cancer immunotherapy approaches. While the major leukocyte subsets and phenotypes are closely related in dogs and humans, the functionality of T cells and antigen presenting cells in the two species has not been previously compared in detail. Such information would be important in interpreting immune response data and evaluating the potential toxicities of new cancer immunotherapies in dogs. To address this question, we used in vitro assays to compare the transcriptomic, cytokine, and proliferative responses of activated canine and human T cells, and also compared responses in activated macrophages. Transcriptomic analysis following T cell activation revealed shared expression of 515 significantly upregulated genes and 360 significantly downregulated immune genes. Pathway analysis identified 33 immune pathways shared between canine and human activated T cells, along with 34 immune pathways that were unique to each species. Activated human T cells exhibited a marked Th1 bias, whereas canine T cells were transcriptionally less active overall. Despite similar proliferative responses to activation, canine T cells produced significantly less IFN-γ than human T cells. Moreover, canine macrophages were significantly more responsive to activation by IFN-γ than human macrophages, as reflected by co-stimulatory molecule expression and TNF-α production. Thus, these studies revealed overall broad similarity in responses to immune activation between dogs and humans, but also uncovered important key quantitative and qualitative differences, particularly with respect to T cell responses, that should be considered in designing and evaluating cancer immunotherapy studies in dogs.

Unedited allogeneic iNKT cells show extended persistence in MHC-mismatched canine recipients

Allogeneic invariant natural killer T cells (allo-iNKTs) induce clinical remission in patients with otherwise incurable cancers and COVID-19-related acute respiratory failure. However, their functionality is inconsistent among individuals, and they become rapidly undetectable after infusion, raising concerns over rejection and limited therapeutic potential. We validate a strategy to promote allo-iNKT persistence in dogs, an established large-animal model for novel cellular therapies. We identify donor-specific iNKT biomarkers of survival and sustained functionality, conserved in dogs and humans and retained upon chimeric antigen receptor engineering. We reason that infusing optimal allo-iNKTs enriched in these biomarkers will prolong their persistence without requiring MHC ablation, high-intensity chemotherapy, or cytokine supplementation. Optimal allo-iNKTs transferred into MHC-mismatched dogs remain detectable for at least 78 days, exhibiting sustained immunomodulatory effects. Our canine model will accelerate biomarker discovery of optimal allo-iNKT products, furthering application of MHC-unedited allo-iNKTs as a readily accessible universal platform to treat incurable conditions worldwide.

Isolation, cloning and analysis of parvovirus-specific canine antibodies from peripheral blood B cells

B-cell cloning methods enable the analysis of antibody responses against target antigens and can be used to reveal the host antibody repertoire, antigenic sites (epitopes), and details of protective immunity against pathogens. Here, we describe improved methods for isolation of canine peripheral blood B cells producing antibodies against canine parvovirus (CPV) capsids by fluorescence-activated cell sorting, followed by cell cloning. We cultured sorted B cells from an immunized dog in vitro and screened for CPV-specific antibody production. Updated canine-specific primer sets were used to amplify and clone the heavy and light chain immunoglobulin sequences directly from the B cells by reverse transcription and PCR. Monoclonal canine IgGs were produced by cloning heavy and light chain sequences into antibody expression vectors, which were screened for CPV binding. Three different canine monoclonal antibodies were analyzed, including two that shared the same heavy chain, and one that had distinct heavy and light chains. The antibodies showed broad binding to CPV variants, and epitopes were mapped to antigenic sites on the capsid. The methods described here are applicable for the isolation of canine B cells and monoclonal antibodies against many antigens.

Negative Influence of Aging on Differentiation and Proliferation of CD8+ T-Cells in Dogs

Immunosenescence is an age-related change in the immune system characterized by a reduction in naïve T-cells and an impaired proliferative capacity of CD8+ T-cells in older individuals. Recent research revealed the crucial impact of immunosenescence on the development and control of cancer, and aging is one of the causes that diminish the therapeutic efficacy of cancer immunotherapies targeting CD8+ T-cell activation. Despite dog cancer being defined as an age-related disease, there are few fundamental understandings regarding the relationship between aging and the canine immune system. Therefore, we aimed to elucidate the characteristics of immunosenescence in dogs and analyzed the effects of aging on the differentiation status and proliferation of canine CD8+ T cells using T-cell specific stimulation with anti-canine CD3/CD28 antibody-coated beads and interleukin-2. As a result, we found that older dogs have a lower proliferative capacity of CD8+ T-cells and a reduction in the naïve subset in their peripheral blood. Further analysis showed that older dogs had attenuated proliferation of the effector and central memory subsets. These results indicate the importance of maintaining less differentiated subsets to expand CD8+ T-cells in dogs and provide helpful insight into the development of dog immune therapies that require T-cell expansion ex vivo.

Racing CARs to veterinary immuno-oncology

Chimeric antigen receptors (CARs) have demonstrated remarkable promise in human oncology over the past two decades, yet similar strategies in veterinary medicine are still in development. CARs are synthetically engineered proteins comprised of a specific antigen-binding single chain variable fragment (ScFv) fused to the signaling domain of a T cell receptor and co-receptors. Patient T cells engineered to express a CAR are directed to recognize and kill target cells, most commonly hematological malignancies. The U.S Food and Drug Administration (FDA) has approved multiple human CAR T therapies, but translation of these therapies into veterinary medicine faces many challenges. In this review, we discuss considerations for veterinary use including CAR design and cell carrier choice, and discuss the future promise of translating CAR therapy into veterinary oncology.

Current nonclinical approaches for immune assessments of immuno-oncology biotherapeutics

Harnessing the immune system to kill tumors has been revolutionary and, as a result, has had an enormous benefit for patients in extending life and resulting in effective cures in some. However, activation of the immune system can come at the cost of undesirable adverse events such as cytokine release syndrome, immune-related adverse events, on-target/off-tumor toxicity, neurotoxicity and tumor lysis syndrome, which are safety risks that can be challenging to assess non-clinically. This article provides a review of the biology and mechanisms that can result in immune-mediated adverse effects and describes industry approaches using in vitro and in vivo models to aid in the nonclinical safety risk assessments for immune-oncology modalities. Challenges and limitations of knowledge and models are also discussed.

Development and pharmacokinetic assessment of a fully canine anti-PD-1 monoclonal antibody for comparative translational research in dogs with spontaneous tumors

PD-1 checkpoint inhibitors have revolutionized the treatment of patients with different cancer histologies including melanoma, renal cell carcinoma, and non-small cell lung carcinoma. However, only a subset of patients show a dramatic clinical response to treatment. Despite intense biomarker discovery efforts, no single robust, prognostic correlation has emerged as a valid outcome predictor. Immune competent, pet dogs develop spontaneous tumors that share similar features to human cancers including chromosome aberrations, molecular subtypes, immune signatures, tumor heterogeneity, metastatic behavior, and chemotherapeutic response. As such, they represent a valuable parallel patient population in which to investigate predictive biomarkers of checkpoint inhibition. However, the lack of a validated, non-immunogenic, canine anti-PD-1 antibody for pre-clinical use hinders this comparative approach and prevents potential clinical benefits of PD-1 blockade being realized in the veterinary clinic. To address this, fully canine single-chain variable fragments (scFvs) that bind canine (c)PD-1 were isolated from a comprehensive canine scFv phage display library. Lead candidates were identified that bound with high affinity to cPD-1 and inhibited its interaction with canine PD-L1 (cPD-L1). The lead scFv candidate re-formatted into a fully canine IgGD reversed the inhibitory effects of cPD-1:cPD-L1 interaction on canine chimeric antigen receptor (CAR) T cell function. In vivo administration showed no toxicity and revealed favorable pharmacokinetics for a reasonable dosing schedule. These results pave the way for clinical trials with anti-cPD-1 in canine cancer patients to investigate predictive biomarkers and combination regimens to inform human clinical trials and bring a promising checkpoint inhibitor into the veterinary armamentarium.

Applying a Clinical Lens to Animal Models of CAR-T Cell Therapies

Chimeric antigen receptor (CAR)-T cells have emerged as a promising treatment modality for various hematologic and solid malignancies over the past decade. Animal models remain the cornerstone of pre-clinical evaluation of human CAR-T cell products and are generally required by regulatory agencies prior to clinical translation. However, pharmacokinetics and pharmacodynamics of adoptively transferred T cells are dependent on various recipient factors, posing challenges for accurately predicting human engineered T cell behavior in non-human animal models. For example, murine xenograft models did not forecast now well-established cytokine-driven systemic toxicities of CAR-T cells seen in humans, highlighting the limitations of animal models that do not perfectly recapitulate complex human immune systems. Understanding the concordance as well as discrepancies between existing pre-clinical animal data and human clinical experiences, along with established advantages and limitations of each model, will facilitate investigators’ ability to appropriately select and design animal models for optimal evaluation of future CAR-T cell products. We summarize the current state of animal models in this field, and the advantages and disadvantages of each approach depending on the pre-clinical questions being asked.

Advances and challenges of CAR T therapy and suitability of animal models (Review)

Chimeric antigen receptors (CARs) recently gained momentum in cancer treatment due to their ability to promote T-cell mediated responses to a specific tumor-associated antigen. CARs are part of the adoptive cell transfer (ACT) strategies that utilize patients' T lymphocytes, genetically engineered to kill cancer cells. However, despite the therapy's success against blood-related malignancies, treating solid tumors has not reached its fullest potential yet. The reasons include the complex suppressive tumor microenvironment, mutations on cancer cells' target receptors, lethal side-effects, restricted trafficking into the tumor, suboptimal persistence in vivo and the lack of animal models that faithfully resemble human tumor's immunological responses. Currently, rodent models are used to investigate the safety and efficacy of CAR therapies. However, these models are limited in representing the human disease faithfully, fail to predict the adverse treatment events and overestimate the efficacy of the therapy. On the other hand, spontaneously developed tumors in dogs are more suited in CAR research and their efficacy has been demonstrated in a number of diseases, including lymphoma, osteosarcoma and mammary tumors. The present review discusses the design and evolution of CARs, challenges of CAR in solid tumors, human and canine clinical trials and advantages of the canine model.

Case Report: Clinical and Serological Hallmarks of Cytokine Release Syndrome in a Canine B Cell Lymphoma Patient Treated With Autologous CAR-T Cells

Background

Chimeric antigen receptor-T (CAR-T) cells have transformed the treatment of human B cell malignancies. With the advent of CAR-T therapy, specific and in some cases severe toxicities have been documented with cytokine release syndrome (CRS) being the most frequently reported. As dogs develop tumors spontaneously and in an immunocompetent setting, they provide a unique translational opportunity to further investigate the activity and toxicities associated with CAR-T therapy. Although various adoptive cellular therapy (ACT) trials have been documented and several more are ongoing in canine oncology, CRS has not been comprehensively described in canine cancer patients.

Case Presentation

Here we present the clinical and serologic changes in a dog treated with autologous CAR-T for relapsed B cell lymphoma that presented with lethargy and fever 3 days following CAR-T. Multiplexed serum cytokine profiling revealed increases in key cytokines implicated in human CRS including IL-6, MCP-1, IFNγ and IL-10 at or shortly after peak CAR-T levels in vivo.

Conclusion

The observations noted in this case report are consistent with CRS development following CAR-T therapy in a canine patient. The dog represents a compelling model to study the pathophysiology of CRS and pre-clinically screen novel therapeutics to prevent and treat this life-threatening condition in the setting of a complex and naturally evolved immune system.

B7-H3 Specific CAR T Cells for the Naturally Occurring, Spontaneous Canine Sarcoma Model

One obstacle for human solid tumor immunotherapy research is the lack of clinically relevant animal models. In this study, we sought to establish a chimeric antigen receptor (CAR) T-cell treatment model for naturally occurring canine sarcomas as a model for human CAR T-cell therapy. Canine CARs specific for B7-H3 were constructed using a single-chain variable fragment derived from the human B7-H3-specific antibody MGA271, which we confirmed to be cross-reactive with canine B7-H3. After refining activation, transduction, and expansion methods, we confirmed target killing in a tumor spheroid three-dimensional assay. We designed a B7-H3 canine CAR T-cell and achieved consistently high levels of transduction efficacy, expansion, and in vitro tumor killing. Safety of the CAR T cells were confirmed in two purposely bred healthy canine subjects following lymphodepletion by cyclophosphamide and fludarabine. Immune response, clinical parameters, and manifestation were closely monitored after treatments and were shown to resemble that of humans. No severe adverse events were observed. In summary, we demonstrated that similar to human cancers, B7-H3 can serve as a target for canine solid tumors. We successfully generated highly functional canine B7-H3-specific CAR T-cell products using a production protocol that closely models human CAR T-cell production procedure. The treatment regimen that we designed was confirmed to be safe in vivo. Our research provides a promising direction to establish in vitro and in vivo models for immunotherapy for canine and human solid tumor treatment.

Increased tumor-infiltrating lymphocyte density is associated with favorable outcomes in a comparative study of canine histiocytic sarcoma

Histiocytic sarcoma (HS) is a rare and aggressive tumor in humans with no universally agreed standard of care therapy. Spontaneous canine HS exhibits increased prevalence in specific breeds, shares key genetic and biologic similarities with the human disease, and occurs in an immunocompetent setting. Previous data allude to the immunogenicity of this disease in both species, highlighting the potential for their successful treatment with immunotherapy. Quantification of CD3 tumor-infiltrating lymphocytes (TIL) in five cases of human HS revealed variable intra-tumoral T cell infiltration. Due to the paucity of human cases and lack of current model systems in which to appraise associations between anti-tumor immunity and treatment-outcome in HS, we analyzed clinical data and quantified TIL in 18 dogs that were previously diagnosed with localized HS and treated with curative-intent tumor resection with or without adjuvant chemotherapy. As in humans, assessment of TIL in biopsy tissues taken at diagnosis reveal a spectrum of immunologically "cold" to "hot" tumors. Importantly, we show that increased CD3 and granzyme B TIL are positively associated with favorable outcomes in dogs following surgical resection. NanoString transcriptional analyses revealed increased T cell and antigen presentation transcripts associated with prolonged survival in canine pulmonary HS and a decreased tumor immunogenicity profile associated with shorter survivals in splenic HS. Based on these findings, we propose that spontaneous canine HS is an accessible and powerful novel model to study tumor immunology and will provide a unique platform to preclinically appraise the efficacy and tolerability of anti-cancer immunotherapies for HS.

A bitesize introduction to canine hematologic malignancies

Hematologic malignancies are frequently diagnosed in dogs and result in a spectrum of clinical signs associated with specific disease types. The most frequently encountered hematologic tumors in dogs include lymphoma, lymphoid and myeloid leukemias, and mast cell, plasma cell, and histiocytic neoplasias. Coupled with the heterogeneous presentations of the different categories and subtypes of canine hematologic malignancies, outcomes for these tumors are also variable. Considering this, appropriate treatment options range from active surveillance to curative intent approaches harnessing surgical, chemotherapeutic, and radiation-based modalities. The underlying pathology of many of these diseases bears remarkable resemblance to that of the corresponding diagnosis made in human patients. We introduce some of the pathogenic drivers of canine hematologic cancers alongside their clinical presentations. An overview of standard-of-care therapies for each of these diseases is also provided. As comparative oncology gains recognition as a valuable setting in which to investigate the pathogenesis of neoplasia and provide powerful, clinically relevant, immunocompetent models for the evaluation of novel therapies, the number of clinicians and scientists participating in cancer research involving dogs is expected to increase. This review aims at providing an introductory overview of canine hematologic malignancies.

Companion Animal Model in Translational Oncology; Feline Oral Squamous Cell Carcinoma and Canine Oral Melanoma

Simple Summary

Laboratory rodents are the most common animal models used in preclinical cancer research. Companion animals with naturally occurring cancers are an under-utilized natural model for the development of new anti-cancer drugs. Dogs and cats develop several types of cancers that resemble those arising in humans with similar clinical and histopathological features and often with similar molecular and genetic backgrounds. Exposure to environmental carcinogens, including air, food and water are also common between people and their pets. Dogs and cats are a unique model that could be integrated between the preclinical laboratory animal model and human clinical trials.

Abstract

Companion animals with naturally occurring cancers can provide an advantageous model for cancer research and in particular anticancer drug development. Compared to commonly utilized mouse models, companion animals, specifically dogs and cats, share a closer phylogenetical distance, body size, and genome organization. Most importantly, pets develop spontaneous, rather than artificially induced, cancers. The incidence of cancer in people and companion animals is quite similar and cancer is the leading cause of death in dogs over 10 years of age. Many cancer types in dogs and cats have similar pathological, molecular, and clinical features to their human counterparts. Drug toxicity and response to anti-cancer treatment in dogs and cats are also similar to those in people. Companion animals share their lives with their owners, including the environmental and socioeconomic cancer-risk factors. In contrast to humans, pets have a shorter life span and cancer progression is often more rapid. Clinical trials in companion animals are cheaper and less time consuming compared to human trials. Dogs and cats with naturally occurring cancers are an ideal and unique model for human cancer research. Model selection for the specific type of cancer is of pivotal importance. Although companion animal models for translational research have been reviewed previously, this review will try to summarize the most important advantages and disadvantages of this model. Feline oral squamous cell carcinoma as a model for head and neck squamous cell carcinoma and canine oral melanoma as a model for mucosal melanoma and immunotherapy in people will be discussed as examples.

A Retrospective Analysis: Autologous Peripheral Blood Hematopoietic Stem Cell Transplant Combined With Adoptive T-Cell Therapy for the Treatment of High-Grade B-Cell Lymphoma in Ten Dogs

In humans, a type of cellular immunotherapy, called adoptive T cell transfer (ACT), can elicit curative responses against hematological malignancies and melanoma. ACT using ex vivo expanded peripheral blood T-cells after multiagent chemotherapy enhances tumor-free survival of dogs with B-cell lymphoma (LSA). Since 2008, our group has been performing autologous peripheral blood hematopoietic stem cell transplants (autoPBHSCT) for the treatment of canine high-grade B-cell LSA, although relapse of residual disease is a common cause of reduced survival in ~70% of treated dogs. We reasoned that a more aggressive treatment protocol combining CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) chemotherapy, autoPBHSCT, and ACT to treat 10 dogs with B-cell LSA could lead to better outcomes when compared to dogs treated with CHOP chemotherapy and autoPBHSCT alone. Using this protocol, once dogs achieved complete hematologic reconstitution post-autoPBHSCT, CD3+ CD8+ and CD3+CD4+ T-cells were expanded from the peripheral blood at a commercial laboratory. Two to four ACT infusions were given to each dog, with a total of 23 infusions given. Infusions were administered with no complications or adverse events. The median cell dose for all infusions was 5.62 x 10⁶ cells/kg (range: 2.59 x 10⁶-8.55 x 10⁶ cells/kg). 4/10 (40%) of dogs were cured of their disease (defined as disease-free for ≥2 years post-autoPBHSCT). Our results confirm that the autoPBHSCT protocol did not hinder the in vitro expansion of autologous peripheral blood T-cells and that the final product could be administered safely, with no adverse events recorded. Finally, since only ten dogs were treated, our results can only suggest that the administration of ACT to dogs after multiagent chemotherapy and autoPHSCT did not lead to a statistically significant increase in median disease-free interval and overall survival when compared to dogs who received CHOP chemotherapy and autoPHSCT alone.

Genetic re-direction of canine primary T cells for clinical trial use in pet dogs with spontaneous cancer

Immunocompetent pet dogs develop spontaneous, human-like cancers, representing a parallel patient population for the investigation of chimeric antigen receptor (CAR) therapies. We have optimized a retrovirus-based protocol to efficiently CAR transduce primary T cells from healthy and tumor-bearing dogs. While transduction efficiencies and CAR-T expansion vary among dogs, CAR expression is typically higher and more stable compared with previous protocols, thus enabling human and comparative oncology researchers to use the dog as a pre-clinical model for human CAR-T cell research. For complete details on the use and execution of this protocol, please refer to Panjwani et al. (2020).

Cancer-Immunity Cycle and Therapeutic Interventions- Opportunities for Including Pet Dogs With Cancer

The tumor-immune interplay represents a dynamic series of events executed by cellular and soluble participants that either promote or inhibit successful tumor formation and growth. Throughout a tumor’s development and progression, the host organism’s immune system reacts by generating anti-cancer defenses through various incremental and combinatorial mechanisms, and this reactive orchestration is termed the cancer-immunity cycle. Success or failure of the cancer-immunity cycle dictates the fate of both host and tumor as winner or loser. Insights into how the tumor and host immune system continuously adapt to each other throughout the lifecycle of the tumor is necessary to rationally develop new effective immunotherapies. Additionally, the evolving nature of the cancer-immunity cycle necessitates therapeutic agility, requiring real-time serial assessment of immunobiologic markers that permits tailoring of therapies to the everchanging tumor immune microenvironment. In order to accelerate advances in the field of immuno-oncology, this review summarizes the steps comprising the cancer-immunity cycle, and underscores key breakpoints in the cycle that either favor cancer regression or progression, as well as shaping of the tumor microenvironment and associated immune phenotypes. Furthermore, specific large animal models of spontaneous cancers that are deemed immunogenic will be reviewed and proposed as unique resources for validating investigational immunotherapeutic protocols that are informed by the cancer-immunity cycle. Collectively, this review will provide a progressive look into the dynamic interplay between tumor and host immune responses and raise awareness for how large animal models can be included for developing combinatorial and sequenced immunotherapies to maximizing favorable treatment outcomes.

Cell Therapy in Veterinary Medicine as a Proof-of-Concept for Human Therapies: Perspectives From the North American Veterinary Regenerative Medicine Association

In the past decade, the potential to translate scientific discoveries in the area of regenerative therapeutics in veterinary species to novel, effective human therapies has gained interest from the scientific and public domains. Translational research using a One Health approach provides a fundamental link between basic biomedical research and medical clinical practice, with the goal of developing strategies for curing or preventing disease and ameliorating pain and suffering in companion animals and humans alike. Veterinary clinical trials in client-owned companion animals affected with naturally occurring, spontaneous disease can inform human clinical trials and significantly improve their outcomes. Innovative cell therapies are an area of rapid development that can benefit from non-traditional and clinically relevant animal models of disease. This manuscript outlines cell types and therapeutic applications that are currently being investigated in companion animals that are affected by naturally occurring diseases. We further discuss how such investigations impact translational efforts into the human medical field, including a critical evaluation of their benefits and shortcomings. Here, leaders in the field of veterinary regenerative medicine argue that experience gained through the use of cell therapies in companion animals with naturally occurring diseases represent a unique and under-utilized resource that could serve as a critical bridge between laboratory/preclinical models and successful human clinical trials through a One-Health approach.

Preclinical pharmacology modeling of chimeric antigen receptor T therapies

Chimeric antigen receptor (CAR) T cells have largely been successful in treating hematological malignancies in the clinic but have not been as effective in treating solid tumors, in part, owing to poor access and the immunosuppressive tumor microenvironment. In addition, CAR-T therapy can cause potentially life-threatening side effects, including cytokine release syndrome and neurotoxicity. Current preclinical testing of CAR-T therapy efficacy is typically performed in mouse tumor models, which often fails to predict toxicity. Recent developments in humanized models and transgenic mice as well as in vitro three-dimensional organoids in early development and nonhuman primate models are being adopted for CAR-T cell efficacy and toxicity assessment. However, because no single model perfectly recapitulates the human immune system and tumor microenvironment, careful model selection based on their respective pros and cons is crucial for adequate evaluation of different CAR-T treatments, so that their clinical development can be better supported.

Meningeal B Cell Clusters Correlate with Submeningeal Pathology in a Natural Model of Multiple Sclerosis

Multiple sclerosis (MS) is an idiopathic demyelinating disease in which meningeal inflammation correlates with accelerated disease progression. The study of meningeal inflammation in MS has been limited because of constrained access to MS brain/spinal cord specimens and the lack of experimental models recapitulating progressive MS. Unlike induced models, a spontaneously occurring model would offer a unique opportunity to understand MS immunopathogenesis and provide a compelling framework for translational research. We propose granulomatous meningoencephalomyelitis (GME) as a natural model to study neuropathological aspects of MS. GME is an idiopathic, progressive neuroinflammatory disease of young dogs with a female bias. In the GME cases examined in this study, the meninges displayed focal and disseminated leptomeningeal enhancement on magnetic resonance imaging, which correlated with heavy leptomeningeal lymphocytic infiltration. These leptomeningeal infiltrates resembled tertiary lymphoid organs containing large B cell clusters that included few proliferating Ki67+ cells, plasma cells, follicular dendritic/reticular cells, and germinal center B cell-like cells. These B cell collections were confined in a specialized network of collagen fibers associated with the expression of the lympho-organogenic chemokines CXCL13 and CCL21. Although neuroparenchymal perivascular infiltrates contained B cells, they lacked the immune signature of aggregates in the meningeal compartment. Finally, meningeal B cell accumulation correlated significantly with cortical demyelination reflecting neuropathological similarities to MS. Hence, during chronic neuroinflammation, the meningeal microenvironment sustains B cell accumulation that is accompanied by underlying neuroparenchymal injury, indicating GME as a novel, naturally occurring model to study compartmentalized neuroinflammation and the associated pathology thought to contribute to progressive MS.

Expression of DEP Domain-Containing 1B in Canine Lymphoma and Other Types of Canine Tumours

Canine lymphoma is the most common haematological malignancy in dogs and is typically treated with multidrug chemotherapy. Most cases are at risk of relapse after several courses of chemotherapy and the oncogenic mechanism remains unknown. This study was aimed at identifying genes expressed in canine lymphoma by cDNA microarray. We found elevated expression of Dishevelled, EGL-10 and pleckstrin (DEP) domain-containing 1B (DEPDC1B) in canine lymphoma cells compared with cells and tissues from healthy dogs. Canine DEPDC1B protein was detected in 13 of 41 lymphoma specimens by immunohistochemistry, but was not detected in lymph nodes from normal dogs. Immunoreactive DEPDC1B protein was also detected in several other types of canine tumour. This is the first report documenting the association of DEPDC1B with canine cancer and the results suggest that DEPDC1B might serve as a potential marker or therapeutic target for canine malignancies.

Effective Activation and Expansion of Canine Lymphocytes Using a Novel Nano-Sized Magnetic Beads Approach

Expansion protocols for human T lymphocytes using magnetic beads, which serve as artificial antigen presenting cells (aAPCs), is well-studied. Yet, the efficacy of magnetic beads for propagation and functionality of peripheral blood lymphocytes (PBLs) isolated from companion dogs still remains limited. Domestic dog models are important in immuno-oncology field. Thus, we built the platform for induction of canine PBLs function, proliferation and biological activity using nano-sized magnetic beads (termed as MicroBeads) coated with anti-canine CD3 and CD28 antibodies. Herein we reveal that activation of canine PBLs via MicroBeads induces a range of genes involved in immediate-early response to T cell activation in dogs. Furthermore, canine T lymphocytes are effectively activated by MicroBeads, as measured by cluster formation and induction of activation marker CD25 on canine T cells as quickly as 24 h post stimulation. Similar to human T cells, canine PBLs require lower activation signal strength for efficient proliferation and expansion, as revealed by titration studies using a range of MicroBeads in the culture. Additionally, the impact of temperature was assessed in multiple stimulation settings, showing that both 37°C and 38.5°C are optimal for the expansion of canine T cells. In contrast to stimulation using plant mitogen Concanavalin A (ConA), MicroBead-based activation did not increase activation-induced cell death. In turn, MicroBeads supported the propagation of T cells with an effector memory phenotype that secreted substantial IL-2 and IFN-γ. Thus, MicroBeads represent an accessible and affordable tool for conducting immunological studies on domestic dog models. Similarities in inducing intracellular signaling pathways further underscore the importance of this model in comparative medicine. Presented herein MicroBead-based expansion platforms for canine PBLs may benefit adoptive immunotherapy in dogs and facilitate the design of next-generation clinical trials in humans.

Elucidating tumor immunosurveillance and immunoediting: a comprehensive review

Abstract The action of the immune system against neoplastic diseases has become one of the main sources of research. The biological pathways of this system are known to contribute in limiting the progression and elimination of the tumor, and are delineated by concepts and mechanisms of immunosurveillance and immunoediting. Immunosurveillance is considered the process by which the immune system recognizes and inhibits the neoplastic process. The concept of immunoediting arises in the sense that immune system is able to shape the antigenic profile of the tumor due to selective pressure, based on the stages of tumor elimination, balance and evasion. The immune response occurs against tumor antigens and changes in the tumor microenvironment, involving different components of the innate immune system, such as T cells, natural Killer cells, B lymphocytes and macrophages. In this sense, knowing these concepts and understanding their respective mechanisms becomes essential in the investigation of new strategies for cancer prevention and cure. Thus, this review presents historical aspects and definitions of immunosurveillance and tumor immunoediting, with emphasis on its importance and applicability, such as on the different methods used in immunotherapy.

Improving human cancer therapy through the evaluation of pet dogs

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

The Importance of the Tumor Microenvironment and Hypoxia in Delivering a Precision Medicine Approach to Veterinary Oncology

Treating individual patients on the basis of specific factors, such as biomarkers, molecular signatures, phenotypes, environment, and lifestyle is what differentiates the precision medicine initiative from standard treatment regimens. Although precision medicine can be applied to almost any branch of medicine, it is perhaps most easily applied to the field of oncology. Cancer is a heterogeneous disease, meaning that even though patients may be histologically diagnosed with the same cancer type, their tumors may have different molecular characteristics, genetic mutations or tumor microenvironments that can influence prognosis or treatment response. In this review, we describe what methods are currently available to clinicians that allow them to monitor key tumor microenvironmental parameters in a way that could be used to achieve precision medicine for cancer patients. We further describe exciting novel research involving the use of implantable medical devices for precision medicine, including those developed for mapping tumor microenvironment parameters (e.g., O2, pH, and cancer biomarkers), delivering local drug treatments, assessing treatment responses, and monitoring for recurrence and metastasis. Although these research studies have predominantly focused on and were tailored to humans, the results and concepts are equally applicable to veterinary patients. While veterinary clinical studies that have adopted a precision medicine approach are still in their infancy, there have been some exciting success stories. These have included the development of a receptor tyrosine kinase inhibitor for canine mast cell tumors and the production of a PCR assay to monitor the chemotherapeutic response of canine high-grade B-cell lymphomas. Although precision medicine is an exciting area of research, it currently has failed to gain significant translation into human and veterinary healthcare practices. In order to begin to address this issue, there is increasing awareness that cross-disciplinary approaches involving human and veterinary clinicians, engineers and chemists may be needed to help advance precision medicine toward its full integration into human and veterinary clinical practices.