Prognostic value of tumour-associated macrophages in canine mammary tumours

Tumor Immune Microenvironment and Its Clinicopathological and Prognostic Associations in Canine Splenic Hemangiosarcoma

Tumor cells can induce important cellular and molecular modifications in the tissue or host where they grow. The idea that the host and tumor interact with each other has led to the concept of a tumor microenvironment, composed of immune cells, stromal cells, blood vessels, and extracellular matrix, representing a unique environment participating and, in some cases, promoting cancer progression. The study of the tumor immune microenvironment, particularly focusing on the role of tumor-infiltrating lymphocytes (TILs), is highly relevant in oncology due to the prognostic and therapeutic significance of TILs in various tumors and their identification as targets for therapeutic intervention. Canine splenic hemangiosarcoma (HSA) is a common tumor; however, its immune microenvironment remains poorly understood. This retrospective study aimed to characterize the histological and immunohistochemical features of 56 cases of canine splenic HSA, focusing particularly on tumor-infiltrating lymphocytes (TILs). We assessed the correlations between the lymphocytic response, the macroscopic and histological characteristics of the tumor, and the survival data. Our study demonstrated that FoxP3 distribution was associated with tumor-related death and survival, while the CD20 count was associated with metastasis. This study provides an in-depth characterization of the tumor immune microenvironment in canine splenic HSA and describes potential prognostic factors.

Strategies for studying immune and non-immune human and canine mammary gland cancer tumour infiltrate

The tumour microenvironment (TME) is usually defined as a cell environment associated with tumours or cancerous stem cells where conditions are established affecting tumour development and progression through malignant cell interaction with non-malignant cells. The TME is made up of endothelial, immune and non-immune cells, extracellular matrix (ECM) components and signalling molecules acting specifically on tumour and non-tumour cells. Breast cancer (BC) is the commonest malignant neoplasm worldwide and the main cause of mortality in women globally; advances regarding BC study and understanding it are relevant for acquiring novel, personalised therapeutic tools. Studying canine mammary gland tumours (CMGT) is one of the most relevant options for understanding BC using animal models as they share common epidemiological, clinical, pathological, biological, environmental, genetic and molecular characteristics with human BC. In-depth, detailed investigation regarding knowledge of human BC-related TME and in its canine model is considered extremely relevant for understanding changes in TME composition during tumour development. This review addresses important aspects concerned with different methods used for studying BC- and CMGT-related TME that are important for developing new and more effective therapeutic strategies for attacking a tumour during specific evolutionary stages.

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.

Tumor-associated macrophages in tumor progression and the role of traditional Chinese medicine in regulating TAMs to enhance antitumor effects

Purpose

To emphasize the importance of tumor-associated macrophages (TAMs) in tumor immunity and to describe the ways in which extracts from Traditional Chinese Medicine (TCM) achieve tumor therapy by modulating macrophages.

Significance

By summarizing these available data, this review focused on TAMs and TCM and can build the foundation for future research on antitumor therapeutics.

Methods

In this review, we summarized the key functions of TAMs in cancer development and overviewed literature on TCM targeting TAMs together with other immune cells aiming to enhance antitumor immunity.

Conclusions

With an indispensable role in antitumor immunity, TAMs contribute to tumor progression, migration, invasion, angiogenesis, lymphangiogenesis, and immunosuppressive microenvironment. In recent years, TCM has gradually gained attention as a potential antitumor adjunctive therapy in preclinical and clinical trials. TCM is also a regulator of cytokine secretion and cell surface molecule expression in balancing the tumor microenvironment (TME), especially macrophage activation and polarization. Therefore, it is believed that TCM could serve as modifiers with immunomodulatory capability.

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.

Canine mammary cancer in overweight or obese female dogs is associated with intratumoral microvessel density and macrophage counts

Obesity is a major health condition owing to its effects on chronic diseases and cancers in humans, but little information is available regarding the role of obesity in canine mammary cancer (CMC). In the present study, we performed immunohistochemistry to investigate the effect of obesity on CMC by analyzing the number of tumor-associated macrophages, intratumoral microvessel density (iMVD), and the expression of prognostic factors including epidermal growth factor receptor (EGFR), cyclooxygenase 2 (COX-2), and Ki67 in CMC specimens. These data were compared in CMC specimens from lean or ideal body weight (Group 1) versus overweight or obese (Group 2) female dogs (n = 60 for each group). Associations between obesity status and histologic characteristics, such as histologic subtype, grading, and lymphatic invasion, were also investigated. Compared with lean or ideal body weight dogs, TAM (tumor-associated macrophage) counts (P < .005) and iMVD (P < .001) were significantly higher in overweight or obese dogs. CMC specimens of dogs in the overweight or obese group also showed higher histologic grade (P < .001). In addition, although no association was found between obesity status and either COX-2 or EGFR expression, Ki67 expression was greater in CMC specimens of overweight or obese dogs (P < .005). The results of this study suggest that obesity may influence CMC development and progression, being associated with higher histologic grade, greater infiltration of TAMs, and increased tumor angiogenesis.

Immune Cells and Immunoglobulin Expression in the Mammary Gland Tumors of Dog

Inflammatory cells have a role in tumor progression and have prognostic and therapeutic potential. The immunohistochemical expression for Mast Cell Tryptase, Macrophage Marker, CD79a, IgA, IgM and IgG on 43 cases of canine mammary gland lesions was analyzed. In hyperplasia, a few B cells (BCs) and Tumor-Associated Macrophages (TAMs) were observed, while the number of Tumor-Associated Mast Cells (TAMCs) was the highest. In the peritumoral stroma of malignant lesions, low number of TAMCs and a high number of TAMAs and BCs were present. Immune cells of each type were always lower in the intratumoral than peritumoral stroma. Positivity to CD79a was also detected in the epithelial cells of simple and micropapillay carcinomas. Immunoglobulin reactivity was mainly located in the epithelial cells where an intense positivity to IgA and IgG and a weak positivity for IgM were detectable. On the basis of our preliminary results and literature data, we suggest that such cells and molecules could be directly involved in the biology of canine mammary gland tumors. In breast cancer, stromal inflammatory cells and cancer derived immunoglobulins have been correlated with the progression, malignancy and poor prognosis of the tumor. The results herein reported show that the dog's mammary gland epithelium also expresses immunoglobulins, and they mostly show a direct relationship with the infiltration of macrophages. In addition, this study shows that the infiltration of mast cells, B-cells and macrophages varies depending on the degree of malignancy of neoplasia.

Immunohistochemical expression of β-catenin, Ki67, CD3 and CD18 in canine colorectal adenomas and adenocarcinomas

Background

Inflammation is believed to influence human colorectal carcinogenesis and may have an impact on prognosis and survival. The mucosal immunophenotype in dogs with colorectal cancer is poorly described.

The aim of this study was to investigate whether the density, distribution and grade of tumor-infiltrating immune cells (TIIs) are different in normal colonic tissue vs benign stages (adenomas) and malignant stages (adenocarcinomas) of canine colorectal carcinogenesis, and thus, whether they can be considered as prognostic factors in dogs.

This retrospective case-control study was performed on formalin-fixed, paraffin-embedded tissue samples from dogs with histologically confirmed colorectal adenoma (n = 18) and adenocarcinoma (n = 13) collected from archived samples. The samples had been collected by colonoscopy, surgery or during postmortem examination. Healthy colonic tissue obtained post mortem from dogs euthanized for reasons not involving the gastrointestinal tract served as control tissue (n = 9).

Results

The tumor samples had significantly lower numbers of CD3+ T-cells in the epithelium compared to controls (adenocarcinoma vs control, Kruskal-Wallis test, p = 0.0004, and adenoma vs control, p = 0.002). Adenomas had a significantly lower number of CD18+ cells in the lamina propria, compared to control samples (Kruskal-Wallis test, p = 0.008). Colonic samples from control dogs had uniform staining of β-catenin along the cell membrane of epithelial cells. Compared to normal colonic cells, the expression levels of cytoplasmic β-catenin were significantly higher in adenomas and adenocarcinomas (adenoma vs control Kruskal-Wallis test, p = 0.004, and adenocarcinoma vs control, p = 0.002). None of the control samples showed positive staining of β-catenin in the nucleus of colonic cells. In contrast, adenocarcinomas and adenomas showed moderate to strong staining of the cell nucleus. The nuclear β-catenin expression (signal strength and distribution) was significantly higher in adenomas compared to adenocarcinomas (Kruskal-Wallis test, p < 0.05).

Conclusions

β-catenin and Ki67 were not useful markers for demonstrating tumor progression from adenomas to adenocarcinomas. The lower presence of CD18 and CD3+ cells in colorectal tumors compared to controls indicates a reduced presence of histiocytes and T-cells, which may have implications for the pathogenesis and progression of colorectal cancer in dogs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02829-6.

Correlation between Tumour Associated Macrophage (TAM) Infiltration and Mitotic Activity in Canine Soft Tissue Sarcomas

Tumour-associated macrophages (TAMs) are an important part of the tumour microenvironment but knowledge of their distribution in canine soft tissue sarcomas (STSs) is limited to absent. We analysed 38 STSs retrieved from the veterinary pathology archive; oral and visceral STSs, synovial cell sarcoma, tumours of histiocytic origin, haemangiosarcoma, carcinosarcomas, and undifferentiated tumours were excluded. Iba-1 positive, non-neoplastic tumour infiltrating cells (morphologically indicative of macrophages) were classified as TAMs and were counted in 10 consecutive tumours areas, where no necrosis or other inflammatory cells could be identified. Associations between numbers of TAMs and mitoses, differentiation, and necrosis scores or grade were investigated. TAMs were evident in all STSs and ranged between 6% to 62% of the cells in the microscopic field. The number of TAMs positively correlated with the STSs' histologic grade. When the components of the grade were analysed separately, TAMs were statistically correlated with mitoses, but not with differentiation or necrosis score. The present findings suggest that TAMs are present in higher numbers when STS proliferation is the predominant feature that drives tumour grade. The abundant presence of TAMs in high-grade STSs may also increase the likelihood of a pathologist misdiagnosing STS for histiocytic sarcoma.

M1 and M2 tumour-associated macrophages subsets in canine malignant mammary tumours: An immunohistochemical study

Among the innate and adaptative immune cells recruited to the tumour site, tumour associated macrophages (TAMs) are particularly abundant and by simplified classification can be classified into (M1) and (M2) TAMs. In the present study, we quantified by immunohistochemistry ionized calcium binding adaptor molecule 1 (Iba1)-positive total and CD204-positive M2-polarized TAMs in 60 canine malignant mammary tumours (CMMTs) to analyze the relationship between M1 or M2 response and the histopathologic features of examined CMMTs, the dogs' body condition score (BCS) and the progression of the neoplastic disease. The mean number of total and CD204+ TAMS were significantly higher in solid and in grade III than in grades I and II carcinomas. Moreover, the mean number of CD204-positive TAMs was significantly higher in CMMTs with lymphatic invasion and necrosis rather than CMMTs without. The presence of higher number of CD204-positive M2-polarized TAMs was associated with a worst outcome of the neoplastic disease: bitches bearing CMMTs with a prevalent M2-polarized TAM response had a median cancer-specific survival time of 449 days, while in animals with a M1-polarized TAM response the median cancer-specific survival time was 1209 days. The results of our study confirm that in CMMTs the presence of a M2-polarized TAMs response might affect the tumour development and behaviour. Finally, it strongly suggests the potential of CD204 expression as a prognostic factor.

Cyclooxygenase-2 expression is associated with infiltration of inflammatory cells in oral and skin canine melanomas

Melanoma is a fast-growing tumour in dogs and represents 7% of the total malignant neoplasms from the skin and is the most common tumour found in the oral cavity. In these tumours, high expression of cyclooxygenase-2 (COX-2) is associated with a poor prognosis. The aim of this study was to verify if the overexpression of COX-2 is related to the modulation of lymphocytes and if it is associated with the angiogenic and proliferative capacity of the melanoma. Canine melanoma samples (n = 85) were analysed by immunohistochemistry to detect the expression of S-100, Melan-A, PNL-2, COX-2, Factor VIII, Ki-67 and immune cells markers (CD3, CD4, FOXP3 and MAC387); and expression levels of MAC387, NOS and CD206 were determined by immunofluorescence. Our study showed a concurrent difference between the expression of COX-2 and inflammatory cell infiltration: Oral melanomas showed positivity for COX-2 in 34% of the cases and this expression was associated with CD3 positivity in the inflammatory infiltrate and angiogenesis; whereas cutaneous melanomas presented positivity for COX-2 in 42% of the cases and this expression was associated with positive staining for CD3, CD4, FOXP3 and MAC387. These markers are associated with inflammatory cells, angiogenesis and proliferation. Interestingly, melanomas were highly infiltrated by FOXP3+ cells, this is related to angiogenesis, whereas CD3, CD4 and MAC387 expression was only associated with cutaneous melanomas. The macrophage profile analysis showed that both oral and cutaneous melanomas with low COX-2 expression have an M1 phenoptype, whereas the cases with high COX-2 expression demonstrate a hybrid M1/M2 profile pattern. We concluded that the COX-2 is overexpressed in 42% of cutaneous melanomas and in 34% of oral melanomas, with a direct association with angiogenesis, proliferation, and intratumoral lymphocyte infiltration. We propose that COX-2 is a key regulator of immune cell infiltration and may drive tumour associated macrophage activation.

Clinical significance and prognostic role of tumor-associated macrophages infiltration according to histologic location in canine mammary carcinomas

Tumor-associated macrophages (TAMs) have been involved in growth and metastases of human and canine mammary tumors. However, the prognostic importance of TAM specific location in canine mammary tumors (CMT) was not evaluated. In this study, we evaluated the potential role of TAMs in specific histologic locations - intratumoral (iTAM) and stromal (sTAM), as well as total macrophage (tTAM) counts - as prognostic indicators in CMT. Clinicopathologic data from 66 animals with mammary carcinoma and their tumors were used in this study. Samples were stained with anti-macrophage antibody for subsequent TAM count. High levels of iTAM, sTAM, and tTAM were related with advanced clinical stage and vascular invasion. Additionally, tTAM revealed a relation with larger tumor size, while high levels of sTAM and tTAM were also correlated with node metastasis and a poor prognosis based on survival analysis. CMT with aggressive features can reveal higher TAM counts. TAMs are associated with vascular invasion and nodal metastasis, and sTAM and tTAM counts are correlated with overall survival, suggesting they could be used as prognostic indicators in canine mammary carcinomas.

A blocking antibody against canine CSF-1R maturated by limited CDR mutagenesis

CSF-1R is a receptor mostly associated with the mononuclear phagocytic system. However, its expression within tumors has been linked with poor prognosis in both humans and dogs. Accordingly, several reports have demonstrated the beneficial effects of blocking CSF-1R in model systems of cancer. In this study, we generated a monoclonal antibody that could block CSF-1R in dogs as the first step to develop an anticancer drug for this species. Initially, an antibody was raised by the hybridoma methodology against the fragment responsible for receptor dimerization. mAb3.1, one of the resulting hybridoma clones, was able to bind macrophages in fixed tissues and was shown to inhibit cells of the mononuclear phagocytic line. Nevertheless, mAb 3.1 could not bind to some glycoforms of the receptor in its native form, while also demonstrating cross-reactivity with other proteins. To enhance binding properties of the mAb, five amino acids of the complementarity-determining region 2 of the variable heavy chain of mAb3.1 were mutated by PCR, and the variant scFv clones were screened by phage display. The selected scFv clones demonstrated improved binding to the native receptor as well as increased anti-macrophage activity. The resulting scFv antibody fragment presented here has the potential for use in cancer patients and in inflammatory diseases. Furthermore, this work provides insights into the use of such restricted mutations in antibody engineering.

Establishment and Characterization of Monoclonal Antibody Against Canine CD8 Alpha

Understanding of the microenvironment of cancer plays a crucial role in cancer research. A tool is needed to evaluate the immune cells surrounding the cancer cells. This study establishes and evaluates a novel monoclonal antibody against canine CD8α (cCD8α). The antibody was produced by immunization of rats with cCD8α-expressing cells. After establishment and selection of hybridoma cells, the clone F3-B2 was established. The reactivity of F3-B2 was confirmed using cCD8α-overexpressing murine cells. Flow cytometric analysis also demonstrated that F3-B2 reacts with cCD8α naturally expressed in canine peripheral blood mononuclear cells and a canine T cell lymphoma cell line. The specimens of lymphoid tissue showed immunohistochemical staining for F3-B2. Moreover, we also found that F3-B2 exhibited reactivity against feline CD8. Thus, this antibody provides a good research tool to analyze CD8-positive cytotoxic lymphocytes in canine and feline tumors.

The Expression of Selected Factors Related to T Lymphocyte Activity in Canine Mammary Tumors

Crosstalk between neoplastic and immune cells in the tumor microenvironment (TME) influences the progression of disease in human and canine cancer patients. Given that canine mammary tumors are a useful model to study breast cancer biology, we aimed to evaluate the expression of genes associated with T lymphocyte activity in benign, malignant, and metastatic canine mammary tumors. Interestingly, metastatic tumors exhibit increased expression of CXCR3, CCR2, IL-4, IL-12p40, and IL-17. In particular, we focused on IL-17, a key interleukin associated with the Th17 lymphocyte phenotype. Th17 cells have been shown to play a contradictory role in tumor immunity. Although IL-17 showed a high expression in the metastatic tumors, the expression of RORγt, a crucial transcription factor for Th17 differentiation was barely detected. We further investigated IL-17 expression using immunohistochemistry, through which we confirmed the increased expression of this interleukin in malignant and metastatic mammary tumors. Finally, we compared the plasma levels of IL-17 in healthy and malignant mammary tumor-bearing dogs using ELISA but found no differences between the groups. Our data indicate that the IL-17 in metastatic tumors may be produced by other cell types, but not by Th17 lymphocytes. Overall, our results broaden the available knowledge on the interactions in canine mammary tumors and provide insight into the development of new therapeutic strategies, with potential benefits for human immune oncology.

Know Thy Model: Charting Molecular Homology in Stromal Reprogramming Between Canine and Human Mammary Tumors

Spontaneous canine simple mammary tumors (CMTs) are often viewed as models of human breast cancer. Cancer-associated stroma (CAS) is central for initiation and progression of human cancer, and is likely to play a key role in canine tumors as well. Until recently, however, canine CAS in general, and in CMT in particular, lacked detailed characterization and it remained unclear how canine and human CAS compare. This void in knowledge regarding canine CAS and the resulting lack of unbiased cross-species analysis of molecular homologies and differences undermined the validity of the canine model for human disease. To assess stromal reprogramming in canine breast tumors, we have recently established a protocol to specifically isolate and analyze CAS and matched normal stroma from archival, formalin-fixed paraffin embedded (FFPE) clinical tumor samples using laser-capture microdissection followed by next-generation RNA-sequencing. Using this approach, we have analyzed stromal reprogramming in both malignant canine mammary carcinomas (mCAs) as well as benign canine mammary adenomas in a series of studies. Our results demonstrate strong stromal reprogramming in CMTs and identify high-grade molecular homology between human and canine CAS. Here, I aim to give a short background on the value of comparative oncology in general, and spontaneous CMT in particular. This will be followed by a concise review of the current knowledge of stromal reprogramming in both malignant canine mCA and benign adenoma. Finally, I will conclude with insights on highly conserved aspects of stromal reprogramming between CMT and human breast cancer that accentuate the relevance of CAS in CMT as a model for the human disease.

Of Mice, Dogs, Pigs, and Men: Choosing the Appropriate Model for Immuno-Oncology Research

The immune system plays dual roles in response to cancer. The host immune system protects against tumor formation via immunosurveillance; however, recognition of the tumor by immune cells also induces sculpting mechanisms leading to a Darwinian selection of tumor cell variants with reduced immunogenicity. Cancer immunoediting is the concept used to describe the complex interplay between tumor cells and the immune system. This concept, commonly referred to as the three E's, is encompassed by 3 distinct phases of elimination, equilibrium, and escape. Despite impressive results in the clinic, cancer immunotherapy still has room for improvement as many patients remain unresponsive to therapy. Moreover, many of the preclinical results obtained in the widely used mouse models of cancer are lost in translation to human patients. To improve the success rate of immuno-oncology research and preclinical testing of immune-based anticancer therapies, using alternative animal models more closely related to humans is a promising approach. Here, we describe 2 of the major alternative model systems: canine (spontaneous) and porcine (experimental) cancer models. Although dogs display a high rate of spontaneous tumor formation, an increased number of genetically modified porcine models exist. We suggest that the optimal immuno-oncology model may depend on the stage of cancer immunoediting in question. In particular, the spontaneous canine tumor models provide a unique platform for evaluating therapies aimed at the escape phase of cancer, while genetically engineered swine allow for elucidation of tumor-immune cell interactions especially during the phases of elimination and equilibrium.

Water extract of ginseng and astragalus regulates macrophage polarization and synergistically enhances DDP's anticancer effect

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, supplementing Qi and strengthening body resistance are an important principle of anticancer treatment. Panax ginseng C.A.Mey. (ginseng) and Astragalus membranaceus Bunge (astragalus) are the representative herbs for this therapeutic principle.

AIM OF THE STUDY

This study aims to explore the effect of the water extract of ginseng and astragalus (WEGA) on regulating macrophage polarization and mediating anticancer in the tumor microenvironment.

MATERIALS AND METHODS

A549 cells were cultured in tumor-associated macrophage (TAM) supernatant with various concentrations of WEGA (0, 5, 10, 20 mg/mL). A549 cell proliferation was determined through methyl thiazole tetrazolium (MTT) assay and real-time cell analysis (RTCA), respectively. In vivo experiments were performed with a Lewis lung cancer (LLC) xenograft mouse model. Forty-eight mice were divided into six groups and treated with saline, WEGA, or cis-diamine dichloro platinum (DDP) with dosage of WEGA (0, 30, 60, 120 mg/kg body weight/day). The different groups were administered with drugs via oral or intraperitoneal injection once a day for 21 consecutive days. Tumor inhibition rate, spleen index, thymus index, cytokine, protein, and mRNA expression levels were detected in mice.

RESULTS

In a co-culture system, WEGA remarkably inhibited A549 cell proliferation, promoted the expression of M1 macrophage markers and inhibited M2 TAMs markers. Therefore, WEGA affected the biological behavior of cancer cells by regulating the expression of some markers relevant to macrophage polarization. In addition, the group of WEGA and DDP chemotherapy effectively inhibited the transplanted tumor growth in mice and improved weight loss and immunosuppressive with the cisplatin inducing.

CONCLUSIONS

This study provides mechanistic insights into the anticancer effect of WEGA through the regulation of macrophage polarization and highlights that WEGA could be a novel option for integrative cancer therapies.

Association of macrophage and lymphocyte infiltration with outcome in canine osteosarcoma

Immunotherapeutic strategies have shown promise for the treatment of canine osteosarcoma (cOSA). Very little is known about the immune microenvironment within cOSA, however, limiting our ability to identify potential immune targets and biomarkers of therapeutic response. We therefore prospectively assessed the disease-free interval (DFI) and overall survival time (ST) of 30 dogs with cOSA treated with amputation and six doses of adjuvant carboplatin. We then quantified lymphocytic (CD3+, FOXP3+) and macrophage (CD204+) infiltrates within the primary tumours of this cohort using immunohistochemistry, and evaluated their association with outcome. Overall, the median DFI and ST were 392 and 455 days, respectively. The median number of CD3+ and FOXP3+ infiltrates were 45.8 cells/mm² (4.6-607.6 cells/mm² ) and 8.5 mm² (0-163.1 cells/mm² ), respectively. The median area of CD204+ macrophages was 4.7% (1.3%-23.3%), and dogs with tumours containing greater than 4.7% CD204+ macrophages experienced a significantly longer DFI (P = 0.016). Interestingly, a significantly lower percentage of CD204+ macrophages was detected in cOSA arising from the proximal humerus compared to other appendicular bone locations (P = 0.016). Lymphocytic infiltrates did not appear to correlate with outcome in cOSA. Overall, our findings suggest that macrophages may play a role in inhibiting cOSA progression, as has been suggested in human osteosarcoma.

Relationship between the inflammatory tumor microenvironment and different histologic types of canine mammary tumors

Mammary neoplasms are the tumors with higher incidence in female dogs. Among the factors that contribute for the development of this and other neoplasms, the inflammatory tumor microenvironment plays a crucial role. Several studies reported important roles for lymphocytes, macrophages, plasma cells, neutrophils, eosinophils and mast cells in this context. In the present study, our aim was to evaluate the number of profile cells of inflammatory cells and area of tumor fibrosis and the relation of these features with canine mammary tumors of different histologic and clinical presentation (benign mixed tumor, carcinoma in mixed tumor, solid carcinoma and tubular carcinoma) Counting and staining of inflammatory cells and tumor fibrosis were performed through histochemistry, while counting and staining of CD4⁺, TCD8⁺ and FOXP3⁺ lymphocytes were performed through immunohistochemistry. Statistical analysis of the association between densities of inflammatory cells, tumor fibrosis and histologic types revealed significant difference for plasma cells (p = .035), neutrophils (p = .0113), macrophages (p = .0047), and tumor fibrosis (p = .05). The found data suggest associations between high number of neutrophils and aggressive mammary tumors, between high densities of plasma cells, macrophages and CD8⁺ cells and between low number of profile cells of CD4⁺ cells and less aggressive tumors. Larger areas of tumor fibrosis showed relation to more aggressive canine mammary tumors.

Bidirectional Regulation of COX-2 Expression Between Cancer Cells and Macrophages

BACKGROUND/AIM

Our aim was to investigate the crosstalk between tumor and immune cells (M2 macrophages) and its effects on cyclo-oxygenase-2 (COX2) regulation in canine mammary tumors (CMT).

MATERIALS AND METHODS

Sh1b CMT cells and human BT474 mammary or HT29 colon cancer cells were co-cultured with canine peripheral blood mononuclear cells (PBMCs) or with macrophage-like differentiated THP1 monocytes (dTHP1). Intracellular COX2 expression by PBMCs, dTHP1 and cancer cells was evaluated by flow cytometry.

RESULTS

Co-culturing of Sh1b and canine PBMCs induced COX2 overexpression in CMT cells. In turn, COX2 expression by PBMCs, mostly CD68⁺ macrophages, was attenuated by co-culture with Sh1b (p=0.0001). In accordance, co-culture with dTHP1 prompted intracellular production of COX2 in both Sh1b CMT cells and HT29 human colon cancer cells and reduced production of COX2 in BT474 human mammary cancer cells. The intracellular COX2 expression from dTHP1 decreased when treated with conditioned medium from cultured Sh1b and HT29 cancer cells.

CONCLUSION

Bidirectional COX2 regulation between cancer and monocytes/macrophages might shape a tolerogenic tumor microenvironment in CMT.

Distribution of Glutathione-Stabilized Gold Nanoparticles in Feline Fibrosarcomas and Their Role as a Drug Delivery System for Doxorubicin-Preclinical Studies in a Murine Model

Feline injection site sarcomas (FISS) are malignant skin tumors with high recurrence rates despite the primary treatment of radical surgical resections. Adjunctive radiotherapy or chemotherapy with doxorubicin is mostly ineffective. Cellular and molecular causes of multidrug resistance, specific physio-chemical properties of solid tumors impairing drug transport, and the tumor microenvironment have been indicated for causing standard chemotherapy failure. Gold nanoparticles are promising imaging tools, nanotherapeutics, and drug delivery systems (DDS) for chemotherapeutics, improving drug transport within solid tumors. This study was conducted to assess the distribution of 4-nm glutathione-stabilized gold nanoparticles in FISS and their influence on kidney and liver parameters in nude mice. The role of gold nanoparticles as a doxorubicin DDS in FISS was examined to determine the potential reasons for failure to translate results from in vitro to in vivo studies. Grade III tumors characterized by a large area of necrosis at their core displayed positive immuneexpression of tumor-associated macrophages (TAM) at both the periphery and within the tumor core near the area of necrosis. Gold nanoparticles did not cause necrosis at the injection site and had no negative effect on liver and kidney parameters in nude mice. Gold nanoparticles accumulated in the tumor core and at the periphery and co-internalized with TAM—an important observation and potential therapeutic target warranting further investigation. The large area of necrosis and high immunoexpression of TAM, indicating “pro-tumor macrophages”, may be responsible for FISS tumor progression and therapeutic failure. However, further studies are required to test this hypothesis.

Strengths and Weaknesses of Pre-Clinical Models for Human Melanoma Treatment: Dawn of Dogs' Revolution for Immunotherapy

Despite several therapeutic advances, malignant melanoma still remains a fatal disease for which novel and long-term curative treatments are needed. The successful development of innovative therapies strongly depends on the availability of appropriate pre-clinical models. For this purpose, several mouse models holding the promise to provide insight into molecular biology and clinical behavior of melanoma have been generated. The most relevant ones and their contribution for the advancement of therapeutic approaches for the treatment of human melanoma patients will be here summarized. However, as models, mice do not recapitulate all the features of human melanoma, thus their strengths and weaknesses need to be carefully identified and considered for the translation of the results into the human clinics. In this panorama, the concept of comparative oncology acquires a priceless value. The revolutionary importance of spontaneous canine melanoma as a translational model for the pre-clinical investigation of melanoma progression and treatment will be here discussed, with a special consideration to the development of innovative immunotherapeutic approaches.

CD204-Expressing Tumor-Associated Macrophages Are Associated With Malignant, High-Grade, and Hormone Receptor-Negative Canine Mammary Gland Tumors

Tumor-associated macrophages (TAMs) are an important component of leukocyte infiltration in tumors. TAMs can be classified into M1 and M2 phenotypes. In the present study, the expression of CD204, an M2-polarized macrophage receptor, was investigated by immunohistochemistry in the area surrounding TAMs in 101 cases of canine mammary gland tumor (CMT). We examined the relationship between M2-polarized TAMs and malignancy, histological subtype, histological grade, molecular subtype, hormone receptor (HR) status, and clinical obesity indices. The mean number of CD204-positive macrophages was significantly higher in malignant CMTs than in benign CMTs ( P = .000). The number of CD204-positive macrophages differed significantly between histological grades ( P = .000) and were significantly higher in grade III than in grades I and II. Moreover, the mean number of CD204-positive macrophages was significantly higher in HR-negative malignant CMTs than in HR-positive malignant CMTs ( P = .035) and in malignant CMTs with lymphatic invasion compared to malignant CMTs without lymphatic invasion ( P = .000). These findings suggest that CD204-positive macrophages might affect the development and behavior of CMTs and highlight the potential of CD204 as a prognostic factor.

Usefulness of cytologic criteria in ultrasound-guided fine-needle aspirates from subcentimeter canine mammary tumors

We determined cytologic features of histologically confirmed subcentimeter canine mammary tumors (CMTs) to determine reasonable criteria for an accurate cytologic diagnosis. Fifty-three CMTs from 28 bitches were included. All cytologic samples were collected by ultrasound-guided fine-needle aspiration biopsy, stained with May-Grünwald/Giemsa, and retrospectively evaluated using a scoring system established for 18 cytologic features. Mean nuclear area (MNA) was also measured for each sample by a computer-assisted program. Based on the histologic diagnosis, CMTs were divided into 2 groups: malignant tumors (25) and benign lesions (15). Data were statistically analyzed using Fisher and Mann–Whitney tests. Chromatin pattern ( p < 0.05) and macrophage infiltration ( p < 0.05) were significantly different between the groups. Median MNA was significantly ( p < 0.05) larger in malignant tumors. The evaluation of these cytologic features in subcentimeter CMTs may increase the sensitivity of cytology.

Canine cancer immunotherapy studies: linking mouse and human

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.

A Comparative Approach of Tumor-Associated Inflammation in Mammary Cancer between Humans and Dogs

Infiltrating cells of the immune system are widely accepted to be generic constituents of tumor microenvironment. It has been well established that the development of mammary cancer, both in humans and in dogs, is associated with alterations in numbers and functions of immune cells at the sites of tumor progression. These tumor infiltrating immune cells seem to exhibit exclusive phenotypic and functional characteristics and mammary cancer cells can take advantage of signaling molecules released by them. Cancer related inflammation has an important role in mammary carcinogenesis, contributing to the acquisition of core hallmark capabilities that allow cancer cells to survive, proliferate, and disseminate. Indeed, recent studies in human breast cancer and in canine mammary tumors have identified a growing list of signaling molecules released by inflammatory cells that serve as effectors of their tumor-promoting actions. These include the COX-2, the tumor EGF, the angiogenic VEGF, other proangiogenic factors, and a large variety of chemokines and cytokines that amplify the inflammatory state. This review describes the intertwined signaling pathways shared by T-lymphocytic/macrophage infiltrates and important tissue biomarkers in both human and dog mammary carcinogenesis.

High COX-2 expression in canine mast cell tumours is associated with proliferation, angiogenesis and decreased overall survival

COX-2 overexpression is associated with several hallmarks of carcinogenesis such as proliferation, angiogenesis, invasion and metastasis. Fifty cases of canine mast cell tumours (MCT) were retrospectively evaluated and submitted to immunohistochemistry for COX-2, CD31, Ki-67, MAC-387 and CD3. Furthermore its relationship with clinicopathological variables and overall survival (OS) was analysed. COX-2 intensity (P = 0.016), but not COX-2 extension nor score was associated with decreased OS and higher grades of malignancy according to Patnaik (P = 0.002) and Kiupel (P < 0.001) grading systems. Cox-2 intensity was also associated with higher Ki-67 scores (P = 0.009), higher mitotic index (P = 0.022) and higher microvascularization density (P = 0.045). No association was observed for COX-2 intensity and CD3-T lymphocyte (P = 0.377) and macrophage infiltration (P = 0.261) by MAC-387 immunollabelling, suggesting an active role of COX-2 in MCT oncogenesis mainly through proliferation and angiogenesis stimulation making it a potentially clinical relevant prognosis marker and therapeutic target.

Role of monocyte recruitment in hemangiosarcoma metastasis in dogs

Canine hemangiosarcoma (HSA) is a highly malignant tumour associated with short survival times because of early and widespread metastasis. In humans and rodents, monocytes play key roles in promoting tumour metastasis through stimulating tumour cell extravasation, seeding, growth and angiogenesis. Therefore, we investigated the potential association between monocyte infiltration and tumour metastasis in HSA and other common canine tumours. Immunohistochemistry was used to quantify CD18⁺ monocytes within metastases. We found that HSA metastases had significantly greater numbers of CD18⁺ monocytes compared with metastases from other tumour types. HSA cells were the highest producers of the monocyte chemokine CCL2, and stimulated canine monocyte migration in a CCL2 dependent manner. These results are consistent with the hypothesis that overexpression of CCL2 and recruitment of large numbers of monocytes may explain in part the aggressive metastatic nature of canine HSA. Thus, therapies designed to block monocyte recruitment may be an effective adjuvant strategy for suppressing HSA metastasis in dogs.

Ki-67 and PCNA Expression in Canine Mammary Tumors and Adjacent Nonneoplastic Mammary Glands: Prognostic Impact by a Multivariate Survival Analysis

The assessment of tumor proliferation has been considered a determining prognostic factor in canine mammary tumors (CMTs). However, no studies have assessed the prognostic importance of proliferation in adjacent nonneoplastic mammary glands. We included 64 CMTs (21 benign and 43 malignant) and studied the proliferation index (PI) of Ki-67 and proliferating cell nuclear antigen (PCNA) together with several clinicopathological characteristics. A positive and statistically significant correlation between the PI of Ki-67 and PCNA in tumors and adjacent nonneoplastic mammary glands was observed in benign and malignant tumors. Tumor size, skin ulceration, histological type, mitotic index, nuclear grade, differentiation grade, histological grade of malignancy, lymph node metastasis, Ki-67, and PCNA expression in tumors and adjacent nonneoplastic mammary glands were statistically associated with overall survival by univariate analysis in malignant cases (n = 43). Histological grade of malignancy and high intratumoral PCNA retained their significance by multivariate analysis arising as independent predictors of overall survival. Interestingly, the PI of Ki-67 and PCNA of adjacent nontumoral mammary glands were associated with clinicopathological features of tumor aggressiveness and shorter overall survival, demonstrating the need to better explore this adjacent non-neoplastic tissue.

Inflammation and cancer: till death tears them apart

Advances in biotechnology have enabled the collection of an immeasurable amount of information from genomic, transcriptomic, metabolomic and proteomic studies of tumours within their microenvironments. The dissection of cytokine and chemokine networks has provided new clues to the interactions between cancer cells and their surrounding inflammatory landscape. To bridge the gap between chronic inflammation and cancer, dynamic participants in the tumour microenvironment have been identified, including tumour-associated macrophages (TAMs) and regulatory T cells (Tregs). Both of these cell types are notable for their ability to cause immunosuppressive conditions and support the evasion of tumour immune surveillance. It is clear now that the tumour-promoting inflammatory environment has to be included as one of the major cancer hallmarks. This review explores the recent advances in the understanding of cancer-related inflammation and how this is being applied to comparative oncology studies in humans and domestic species, such as the dog.