Metastatic immune infiltrates correlate with those of the primary tumour in canine osteosarcoma

Tumor-associated macrophages in canine visceral hemangiosarcoma

Canine hemangiosarcoma (HSA) is a highly malignant tumor derived from hematopoietic stem cells and commonly occurs in visceral organs or skin. Visceral HSAs are particularly aggressive and progress rapidly despite multimodal treatment. Tumor-associated macrophages (TAMs) play a central role in carcinogenesis, tumor progression, and metastasis in humans and murine models. In this retrospective study, we investigated the prevalence and phenotype of TAMs in privately owned, treatment-naïve dogs with naturally occurring HSA. We used CD204 as a general macrophage marker and CD206 as a marker for M2-polarized macrophages. Formalin-fixed paraffin-embedded tissues from HSAs in the spleen (n = 9), heart (n = 6), and other locations (n = 12) from 17 dogs were sectioned and immunohistochemically labeled with CD204 and CD206 antibodies. The mean number of log(CD204)- and log(CD206)-positive cells and the ratio of log(CD206/CD204)-positive cells were compared with normal surrounding tissues and between tumor locations. There were significantly more macrophages and M2 macrophages, and a higher ratio of M2 macrophages to total macrophages in tumor hot spots (P = .0002, P < .0001, and P = .0002, respectively) and in tumor tissues outside of hot spots (P = .009, P = .002, and P = .007, respectively) than in normal surrounding tissues. There were no significant differences between tumor locations, but there was a trend toward higher numbers of CD204-positive macrophages within the splenic tumors. There was no association between histological parameters or clinical stage and TAM numbers or phenotype. As in humans, TAMs in dogs with HSA have a predominantly M2-skewed phenotype. Dogs with HSA could serve as excellent models to evaluate new TAM-reprogramming therapies.

Tumor-associated macrophages: Prognostic and therapeutic targets for cancer in humans and dogs

Macrophages are ancient, phagocytic immune cells thought to have their origins 500 million years ago in metazoan phylogeny. The understanding of macrophages has evolved to encompass their foundational roles in development, homeostasis, tissue repair, inflammation, and immunity. Notably, macrophages display high plasticity in response to environmental cues, capable of a strikingly wide variety of dynamic gene signatures and phenotypes. Macrophages are also involved in many pathological states including neural disease, asthma, liver disease, heart disease, cancer, and others. In cancer, most tumor-associated immune cells are macrophages, coined tumor-associated macrophages (TAMs). While some TAMs can display anti-tumor properties such as phagocytizing tumor cells and orchestrating an immune response, most macrophages in the tumor microenvironment are immunosuppressive and pro-tumorigenic. Macrophages have been implicated in all stages of cancer. Therefore, interest in manipulating macrophages as a therapeutic strategy against cancer developed as early as the 1970s. Companion dogs are a strong comparative immuno-oncology model for people due to documented similarities in the immune system and spontaneous cancers between the species. Data from clinical trials in humans and dogs can be leveraged to further scientific advancements that benefit both species. This review aims to provide a summary of the current state of knowledge on macrophages in general, and an in-depth review of macrophages as a therapeutic strategy against cancer in humans and companion dogs.

Comparative Evaluation of Tumor-Infiltrating Lymphocytes in Companion Animals: Immuno-Oncology as a Relevant Translational Model for Cancer Therapy

Simple Summary

Laboratory experiments studying solid tumors are limited by the inability to adequately model the tumor microenvironment and important immune interactions. Immune cells that infiltrate the tumor bed or periphery have been documented as reliable biomarkers in human studies. Veterinary oncology provides a naturally occurring cancer model that could complement biomarker discovery, clinical trials, and drug development.

Abstract

Despite the important role of preclinical experiments to characterize tumor biology and molecular pathways, there are ongoing challenges to model the tumor microenvironment, specifically the dynamic interactions between tumor cells and immune infiltrates. Comprehensive models of host-tumor immune interactions will enhance the development of emerging treatment strategies, such as immunotherapies. Although in vitro and murine models are important for the early modelling of cancer and treatment-response mechanisms, comparative research studies involving veterinary oncology may bridge the translational pathway to human studies. The natural progression of several malignancies in animals exhibits similar pathogenesis to human cancers, and previous studies have shown a relevant and evaluable immune system. Veterinary oncologists working alongside oncologists and cancer researchers have the potential to advance discovery. Understanding the host-tumor-immune interactions can accelerate drug and biomarker discovery in a clinically relevant setting. This review presents discoveries in comparative immuno-oncology and implications to cancer therapy.

Exploring the association of intratumoral immune cell infiltrates with histopathologic grade in canine mast cell tumors

Cutaneous canine mast cell tumors (ccMCTs) vary in their biological behavior, treatment, and prognosis, based on their grade. Immune cell infiltration has been associated with prognosis and response to treatments in some human cancers, and immune-targeting therapeutics are increasingly being explored in veterinary oncology. However, currently little is known about the tumor microenvironment (TME) in ccMCTs. Therefore, the objective of this study was to determine the prevalence of T lymphocytes, T regulatory lymphocytes, PD-1+ cells and macrophages in low- and high-grade ccMCTs. Thirty low-grade and 20 high-grade formalin-fixed paraffin-embedded ccMCT samples were included. Immunohistochemistry (IHC) was performed to detect CD3, FOXP3, Iba1, and PD-1 on sequential sections. Three 400x fields with the highest numbers of CD3+ cells were identified for each tumor. The percentage of CD3+, FOXP3+, and Iba1+ cells, and the number of PD-1+ cells, was quantified in each of these three "hot-spot" fields using ImageJ software. Iba1 expression was significantly greater in high-grade compared to low-grade ccMCTs (mean = 12.5% vs. 9.6%, p = 0.043). PD-1 expression was low overall, but a significantly higher number of PD-1-expressing cells was observed in high-grade ccMCTs (median 1 vs. 0, p = 0.001). No significant difference was noted in CD3 and FOXP3 expression between ccMCT grades. Macrophages and PD-1+ cells were more frequent in high-grade, compared to low-grade ccMCTs. Further studies are needed to define the role of macrophages and rare PD-1+ cells in high-grade ccMCTs.

Osteoclasts differential-related prognostic biomarker for osteosarcoma based on single cell, bulk cell and gene expression datasets

Osteosarcoma (OS) is one of the most common primary bone malignant tumors. Osteoclasts have been shown to have a valuable role in OS. In the present study, we analyzed the differentiation states of osteoclasts in OS and their prognostic significance based on integrated scRNA-seq and bulk RNA-seq data. Osteoclasts in distinct differentiation states were characterized, and 661 osteoclasts differentiation-related genes (ODRGs) were obtained. ORDGs in distinct differentiation states were enriched in distinct functions and pathways. TPM1, S100A13, LOXL1, PSMD10, ST3GAL4, PEF1, SERPINE2, TUBB, FAM207A, TUBA1A, and DCN were identified as the significant survival-predicting ODRGs. We successfully developed a risk score model based on these survival-predicting ODRGs. In addition, we generated a nomogram applicable for clinical with both ODRGs signatures and clinicopathological parameters, and validated in OS cohorts to predict OS patient outcome. This study proposed and verified the important roles of osteoclasts differentiation in the prognosis of patients with OS, suggesting promising therapeutic targets for OS.

Natural Killer and T Cell Infiltration in Canine Osteosarcoma: Clinical Implications and Translational Relevance

Metastatic osteosarcoma has a bleak prognosis in both humans and dogs, and there have been minimal therapeutic advances in recent decades to improve outcomes. Naturally occurring osteosarcoma in dogs is shown to be a highly suitable model for human osteosarcoma, and limited data suggest the similarities between species extend into immune responses to cancer. Studies show that immune infiltrates in canine osteosarcoma resemble those of human osteosarcoma, and the analysis of tumor immune constituents as predictors of therapeutic response is a promising direction for future research. Additionally, clinical studies in dogs have piloted the use of NK transfer to treat osteosarcoma and can serve as valuable precursors to clinical trials in humans. Cytotoxic lymphocytes in dogs and humans with osteosarcoma have increased activation and exhaustion markers within tumors compared with blood. Accordingly, NK and T cells have complex interactions among cancer cells and other immune cells, which can lead to changes in pathways that work both for and against the tumor. Studies focused on NK and T cell interactions within the tumor microenvironment can open the door to targeted therapies, such as checkpoint inhibitors. Specifically, PD-1/PD-L1 checkpoint expression is conserved across tumors in both species, but further characterization of PD-L1 in canine osteosarcoma is needed to assess its prognostic significance compared with humans. Ultimately, a comparative understanding of T and NK cells in the osteosarcoma tumor microenvironment in both dogs and humans can be a platform for translational studies that improve outcomes in both dogs and humans with this frequently aggressive disease.

The Dog as a Model to Study the Tumor Microenvironment

Cancer is a complex and dynamic disease with an outcome that depends on a strict crosstalk between tumor cells and other components in tumor microenvironment, namely, tumor-infiltrating immune cells, fibroblasts, cancer stem cells, adipocytes, and endothelial cells. Within the tumor microenvironment, macrophages and T-lymphocytes appear to be key effectors during the several steps of tumor initiation and progression. Tumor cells, through the release of a plethora of signaling molecules, can induce immune tolerance, by avoiding immune surveillance, and inhibit immune cells cytotoxic functions. Furthermore, as the tumor grows, tumor microenvironment reveals a series of dysfunctional conditions that potentiate a polarization of harmful humoral Th2 and Th17, an upregulation of Treg cells, and a differentiation of macrophages into the M2 subtype, which contribute to the activation of several signaling pathways involving important tissue biomarkers (COX-2, EGFR, VEGF) implicated in cancer aggressiveness and poor clinical outcomes. In order to maintain the tumor growth, cancer cells acquire several adaptations such as neovascularization and metabolic reprogramming. An extensive intracellular production of lactate and protons is observed in tumor cells as a result of their high glycolytic metabolism. This contributes not only for the microenvironment pH alteration but also to shape the immune response that ultimately impairs immune cells capabilities and effector functions.In this chapter, the complexity of tumor microenvironment, with special focus on macrophages, T-lymphocytes, and the impact of lactate efflux, was reviewed, always trying to demonstrate the strong similarities between data from studies of humans and dogs, a widely proposed model for comparative oncology studies.

Recent Advances in the Discovery of Biomarkers for Canine Osteosarcoma

Canine osteosarcoma (OSA) is an aggressive malignancy that frequently metastasizes to the lung and bone. Not only has there been essentially no improvement in therapeutic outcome over the past 3 decades, but there is also a lack of reliable biomarkers in clinical practice. This makes it difficult to discriminate which patients will most benefit from the standard treatment of amputation and adjuvant chemotherapy. The development of reliable diagnostic biomarkers could aid in the clinical diagnosis of primary OSA and metastasis; while prognostic, and predictive biomarkers could allow clinicians to stratify patients to predict response to treatment and outcome. This review summarizes biomarkers that have been explored in canine OSA to date. The focus is on molecular biomarkers identified in tumor samples as well as emerging biomarkers that have been identified in blood-based (liquid) biopsies, including circulating tumor cells, microRNAs, and extracellular vesicles. Lastly, we propose future directions in biomarker research to ensure they can be incorporated into a clinical setting.

Blood-Based Liquid Biopsy for Comprehensive Cancer Genomic Profiling Using Next-Generation Sequencing: An Emerging Paradigm for Non-invasive Cancer Detection and Management in Dogs

This proof-of-concept study demonstrates that blood-based liquid biopsy using next generation sequencing of cell-free DNA can non-invasively detect multiple classes of genomic alterations in dogs with cancer, including alterations that originate from spatially separated tumor sites. Eleven dogs with a variety of confirmed cancer diagnoses (including localized and disseminated disease) who were scheduled for surgical resection, and five presumably cancer-free dogs, were enrolled. Blood was collected from each subject, and multiple spatially separated tumor tissue samples were collected during surgery from 9 of the cancer subjects. All samples were analyzed using an advanced prototype of a novel liquid biopsy test designed to non-invasively interrogate multiple classes of genomic alterations for the detection, characterization, and management of cancer in dogs. In five of the nine cancer patients with matched tumor and plasma samples, pre-surgical liquid biopsy testing identified genomic alterations, including single nucleotide variants and copy number variants, that matched alterations independently detected in corresponding tumor tissue samples. Importantly, the pre-surgical liquid biopsy test detected alterations observed in spatially separated tissue samples from the same subject, demonstrating the potential of blood-based testing for comprehensive genomic profiling of heterogeneous tumors. Among the three patients with post-surgical blood samples, genomic alterations remained detectable in one patient with incomplete tumor resection, suggesting utility for non-invasive detection of minimal residual disease following curative-intent treatment. Liquid biopsy allows for non-invasive profiling of cancer-associated genomic alterations with a simple blood draw and has potential to overcome the limitations of tissue-based testing posed by tissue-level genomic heterogeneity.

Comparative Immunology and Immunotherapy of Canine Osteosarcoma

Approximately 800 people are diagnosed with osteosarcoma (OSA) per year in the USA. Although 70% of patients with localized OSA are cured with multiagent chemotherapy and surgical resection, the prognosis for patients with metastatic or relapsed disease is guarded. The small number of patients diagnosed annually contributes to an incomplete understanding of disease pathogenesis, and challenges in performing appropriately powered clinical trials and detecting correlative biomarkers of response. While mouse models of OSA are becoming increasingly sophisticated, they generally fail to accurately recapitulate tumor heterogeneity, tumor microenvironment (TME), systemic immune dysfunction, and the clinical features of tumor recurrence, metastases, and chemoresistance, which influence outcome. Pet dogs spontaneously develop OSA with an incidence that is 30-50 times higher than humans. Canine OSA parallels the human disease in its clinical presentation, biological behavior, genetic complexity, and therapeutic management. However, despite therapy, most dogs die from metastatic disease within 1 year of diagnosis. Since OSA occurs in immune-competent dogs, immune factors that sculpt tumor immunogenicity and influence responses to immune modulation are in effect. In both species, immune modulation has shown beneficial effects on patient outcome and work is now underway to identify the most effective immunotherapies, combination of immunotherapies, and correlative biomarkers that will further improve clinical response. In this chapter, the immune landscape of canine OSA and the immunotherapeutic strategies used to modulate antitumor immunity in dogs with the disease will be reviewed. From this immunological viewpoint, the value of employing dogs with spontaneous OSA to accelerate and inform the translation of immunotherapies into the human clinic will be underscored.

Improving human cancer therapy through the evaluation of pet dogs

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

FOXP3, CD208, and CD206 Expression in Canine Cutaneous Histiocytoma

Canine cutaneous histiocytoma (CCH) is a noninfectious tumor that spontaneously regresses. It is suggested that this regression is due to tumor cell maturation, which is responsible for CD8 lymphocyte activation and tumor cell destruction. Nevertheless, the possible role of the immune microenvironment in tumor regression has not been investigated to date. The aim of this study was to investigate the expression of CD208 and FoxP3 as markers of dendritic cells and regulatory T lymphocytes, respectively, and tumor cell expression of CD206 as a marker of Langerhans cell activation, and relate these parameters to the different phases of CCH and to intratumoral T cell infiltration. Formalin-fixed, paraffin-embedded samples from 31 CCH were evaluated. In each case, the mitotic count and regression phase were recorded. Within the tumor, a quantitative evaluation of immunolabeled CD208⁺ cells, FoxP3⁺ cells, and CD3⁺ lymphocytes was performed, as well as the CD206⁺ tumor cell location. Intratumoral CD208⁺ cells correlated with CD3⁺ lymphocytic infiltration. The possible role of dendritic cells in tumor regression was not confirmed since CD208 seemed to be a nonspecific marker for canine dendritic cells. FoxP3⁺ lymphocyte density was not correlated with any parameter. Neoplastic Langerhans cells presented progressive CD206 expression, from the bottom of the tumor to the epidermis, which correlated with the tumor regression phase and with intratumoral T lymphocyte infiltration. In conclusion, we confirmed a CD206 phenotype change in tumor cells in a spatial group-related pattern, supporting the hypothesis that tumoral Langerhans cells acquire a mature phenotype with tumor regression.

Sarcomas-A barren immunological wasteland or field of opportunity for immunotherapy?

Key advances in our understanding of immunobiology and the immunosuppressive mechanisms of the tumour microenvironment have led to significant breakthroughs in manipulating the immune system to successfully treat cancer. Remarkable therapeutic responses have occurred with tumours that carry a high mutational burden. In these cases, pre-existing tumour-specific T cells can be rejuvenated via checkpoint inhibition to eliminate tumours. Furthermore, durable remissions have been achieved in haematological malignancies following adoptive transfer of T cells that specifically target cell surface proteins where expression is restricted to the malignancy's cell of origin. Soft tissue sarcomas and bone sarcomas have a paucity of non-synonymous somatic mutations and do not commonly express known, targetable, tumour-specific antigens. Historically, soft tissue sarcomas have been considered immunologically 'cold' and as such, unlikely candidates for immune therapy. Here, we review the immune landscape of canine and feline sarcomas and the immunotherapeutic strategies that have been employed in veterinary clinical trials to improve patient outcome. We also provide insight into immunotherapeutic approaches being used to treat human sarcomas. Together, current data indicates that, rather than a barren immunological wasteland, sarcomas represent a field of opportunities for immunotherapies. Furthermore, we and others would suggest that strategic combinations of immunotherapeutic approaches may hold promise for more effective treatments for high grade soft tissue sarcomas and bone sarcomas.

Bone sarcomas in the immunotherapy era

Bone sarcomas are primary bone tumours found mainly in children and adolescents, as osteosarcoma and Ewing's sarcoma, and in adults in their 40s as chondrosarcoma. The last four decades the development of therapeutic approaches was based on drug combinations have shown no real improvement in overall survival. Recently oncoimmunology has allowed a better understand of the crucial role played by the immune system in the oncologic process. This led to clinical trials with the aim of reprogramming the immune system to facilitate cancer cell recognition. Immune infiltrates of bone sarcomas have been characterized and their molecular profiling identified as immune therapeutic targets. Unfortunately, the clinical responses in trials remain anecdotal but highlight the necessity to improve the characterization of tumour micro-environment to unlock the immunotherapeutic response, especially in their paediatric forms. Bone sarcomas have entered the immunotherapy era and here we overview the recent developments in immunotherapies in these sarcomas. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

Naturally-Occurring Invasive Urothelial Carcinoma in Dogs, a Unique Model to Drive Advances in Managing Muscle Invasive Bladder Cancer in Humans

There is a great need to improve the outlook for people facing urinary bladder cancer, especially for patients with invasive urothelial carcinoma (InvUC) which is lethal in 50% of cases. Improved outcomes for patients with InvUC could come from advances on several fronts including emerging immunotherapies, targeted therapies, and new drug combinations; selection of patients most likely to respond to a given treatment based on molecular subtypes, immune signatures, and other characteristics; and prevention, early detection, and early intervention. Progress on all of these fronts will require clinically relevant animal models for translational research. The animal model(s) should possess key features that drive success or failure of cancer drugs in humans including tumor heterogeneity, genetic-epigenetic crosstalk, immune cell responsiveness, invasive and metastatic behavior, and molecular subtypes (e.g., luminal, basal). Experimental animal models, while essential in bladder cancer research, do not possess these collective features to accurately predict outcomes in humans. These key features, however, are present in naturally-occurring InvUC in pet dogs. Canine InvUC closely mimics muscle-invasive bladder cancer in humans in cellular and molecular features, molecular subtypes, immune response patterns, biological behavior (sites and frequency of metastasis), and response to therapy. Thus, dogs can offer a highly relevant animal model to complement other models in research for new therapies for bladder cancer. Clinical treatment trials in pet dogs with InvUC are considered a win-win-win scenario; the individual dog benefits from effective treatment, the results are expected to help other dogs, and the findings are expected to translate to better treatment outcomes in humans. In addition, the high breed-associated risk for InvUC in dogs (e.g., 20-fold increased risk in Scottish Terriers) offers an unparalleled opportunity to test new strategies in primary prevention, early detection, and early intervention. This review will provide an overview of canine InvUC, summarize the similarities (and differences) between canine and human InvUC, and provide evidence for the expanding value of this canine model in bladder cancer research.