Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology

Initial insights into the interaction of antibodies radiolabeled with Lutetium-177 and Actinium-225 with tumor microenvironment in experimental human and canine osteosarcoma

BACKGROUND

Osteosarcoma (OS) is a prevalent primary bone cancer affecting both humans and canines. This study describes initial insights into the interaction of the human monoclonal antibody IF3 to an insulin-like growth factor 2 receptor (IGF2R) radiolabeled with either alpha-emitting Actinium-225 (225Ac) or beta-emitting Lutetium-177 (177Lu) radionuclides with the OS cells and tumor microenvironment (TME) in experimental human and canine OS.

BASIC PROCEDURES

SCID mice bearing canine Gracie or human OS-33 OS tumors were treated with 177Lu- or 225Ac-labeled IF3 antibody, sacrificed at 24, 72 or 168 h post-treatment and their tumors were analyzed by immunohistochemistry (IHC) for the presence of OS cells, various elements of TME as well as for the double DNA strand breaks with γH2AX and caspase 3 assays.

MAIN FINDINGS

IHC revealed a reduction in IGF2R-positive OS cells and OS stem cell populations post therapy with 225Ac- and 177Lu-labeled IF3 antibody. Notably, radiolabeled IF3 antibody effectively diminished pro-tumorigenic M2 macrophages, highlighting its therapeutic promise. The study also unveiled varied responses of natural killer (NK) cells and M1 macrophages, shedding light on the intricate TME interplay. Time-dependent increase in γ-H2AX staining in canine Gracie and human OS-33 tumors treated with [177Lu]Lu-IF3 and [225Ac]Ac-IF3 was observed at 24 and 72 h post-RIT.

PRINCIPAL CONCLUSIONS

These findings suggest that radiolabeled antibodies offer a hopeful avenue for personalized OS treatment, emphasizing the importance of understanding their impact on the TME and potential synergies with immunotherapy.

Immunohistochemical Investigation into Protein Expression Patterns of FOXO4, IRF8 and LEF1 in Canine Osteosarcoma

Osteosarcoma (OSA) is the most common type of primary bone malignancy in people and dogs. Our previous molecular comparisons of canine OSA against healthy bone resulted in the identification of differentially expressed protein-expressing genes (forkhead box protein O4 (FOXO4), interferon regulatory factor 8 (IRF8), and lymphoid enhancer binding factor 1 (LEF1)). Immunohistochemistry (IHC) and H-scoring provided semi-quantitative assessment of nuclear and cytoplasmic staining alongside qualitative data to contextualise staining (n = 26 patients). FOXO4 was expressed predominantly in the cytoplasm with significantly lower nuclear H-scores. IRF8 H-scores ranged from 0 to 3 throughout the cohort in the nucleus and cytoplasm. LEF1 was expressed in all patients with significantly lower cytoplasmic staining compared to nuclear. No sex or anatomical location differences were observed. While reduced levels of FOXO4 might indicate malignancy, the weak or absent protein expression limits its primary use as diagnostic tumour marker. IRF8 and LEF1 have more potential for prognostic and diagnostic uses and facilitate further understanding of their roles within their respective molecular pathways, including Wnt/beta-catenin/LEF1 signalling and differential regulation of tumour suppressor genes. Deeper understanding of the mechanisms involved in OSA are essential contributions towards the development of novel diagnostic, prognostic, and treatment options in human and veterinary medicine contexts.

Preclinical evaluation and first-in-dog clinical trials of PBMC-expanded natural killer cells for adoptive immunotherapy in dogs with cancer

BACKGROUND

Natural killer (NK) cells are cytotoxic cells capable of recognizing heterogeneous cancer targets without prior sensitization, making them promising prospects for use in cellular immunotherapy. Companion dogs develop spontaneous cancers in the context of an intact immune system, representing a valid cancer immunotherapy model. Previously, CD5 depletion of peripheral blood mononuclear cells (PBMCs) was used in dogs to isolate a CD5dim-expressing NK subset prior to co-culture with an irradiated feeder line, but this can limit the yield of the final NK product. This study aimed to assess NK activation, expansion, and preliminary clinical activity in first-in-dog clinical trials using a novel system with unmanipulated PBMCs to generate our NK cell product.

METHODS

Starting populations of CD5-depleted cells and PBMCs from healthy beagle donors were co-cultured for 14 days, phenotype, cytotoxicity, and cytokine secretion were measured, and samples were sequenced using the 3'-Tag-RNA-Seq protocol. Co-cultured human PBMCs and NK-isolated cells were also sequenced for comparative analysis. In addition, two first-in-dog clinical trials were performed in dogs with melanoma and osteosarcoma using autologous and allogeneic NK cells, respectively, to establish safety and proof-of-concept of this manufacturing approach.

RESULTS

Calculated cell counts, viability, killing, and cytokine secretion were equivalent or higher in expanded NK cells from canine PBMCs versus CD5-depleted cells, and immune phenotyping confirmed a CD3-NKp46+ product from PBMC-expanded cells at day 14. Transcriptomic analysis of expanded cell populations confirmed upregulation of NK activation genes and related pathways, and human NK cells using well-characterized NK markers closely mirrored canine gene expression patterns. Autologous and allogeneic PBMC-derived NK cells were successfully expanded for use in first-in-dog clinical trials, resulting in no serious adverse events and preliminary efficacy data. RNA sequencing of PBMCs from dogs receiving allogeneic NK transfer showed patient-unique gene signatures with NK gene expression trends in response to treatment.

CONCLUSIONS

Overall, the use of unmanipulated PBMCs appears safe and potentially effective for canine NK immunotherapy with equivalent to superior results to CD5 depletion in NK expansion, activation, and cytotoxicity. Our preclinical and clinical data support further evaluation of this technique as a novel platform for optimizing NK immunotherapy in dogs.

Clinical, pathologic and molecular findings in 2 Rottweiler littermates with appendicular osteosarcoma

Appendicular osteosarcoma was diagnosed and treated in a pair of littermate Rottweiler dogs, resulting in distinctly different clinical outcomes despite similar therapy within the context of a prospective, randomized clinical trial (NCI-COTC021/022). Histopathology, immunohistochemistry, mRNA sequencing, and targeted DNA hotspot sequencing techniques were applied to both dogs' tumors to define factors that could underpin their differential response to treatment. We describe the comparison of their clinical, histologic and molecular features, as well as those from a companion cohort of Rottweiler dogs, providing new insight into potential prognostic biomarkers for canine osteosarcoma.

An evaluation of the combination effect of zoledronate and chemotherapeutic agents in canine osteosarcoma cells

Introduction

Osteosarcoma (OSA) is an aggressive form of bone cancer in both dogs and humans. The treatment options for metastatic (stage III) OSA are currently limited and the prognosis is poor. Zoledronate, a second generation amino-bisphosphonate, is commonly used for palliation of cancer induced bone pain. Zoledronate has also demonstrated anti-cancer properties and possibly enhances the cytotoxicity of doxorubicin in a canine histiocytosis cell line and human prostatic cancer cell line. The goal of this study was to evaluate the combination effect of zoledronate and various chemotherapeutic drugs in canine OSA cells.

Methods

Canine OSA cell line (D17), cells from two canine primary OSAs, and MDCK, a canine kidney cell line, were used to evaluate the therapeutic potential of these drugs. Carboplatin, doxorubicin, vinorelbine, toceranib, and isophosphoramide mustard (active metabolite of ifosfamide) were used as chemotherapeutic agents. First, cells were treated with either zoledronate or chemotherapy drug alone for 72 hours. Cell viability was assessed using CellTiter Glo and IC5, IC10, IC20, and IC50 were calculated. Second, cells were treated with a combination of zoledronate and each chemotherapeutic agent at their IC5, IC10, IC20, and IC50 concentrations. After 72 hours, cell viability was assessed by CellTiter Glo.

Results and discussion

Zoledronate, carboplatin, doxorubicin, vinorelbine, and isophosphoramide mustard showed concentration dependent decrease in cell viability. Toceranib showed decreased cell viability only at higher concentrations. When zoledronate was used in combination with chemotherapy drugs, while it showed potential synergistic effects with toceranib, potential antagonistic effects with vinorelbine and isophosphoramide mustard were observed. However, the results differed by cell line and thus, further evaluation is warranted to understand the exact mechanism of action.

Host-derived growth factors drive ERK phosphorylation and MCL1 expression to promote osteosarcoma cell survival during metastatic lung colonization

PURPOSE

For patients with osteosarcoma, disease-related mortality most often results from lung metastasis-a phenomenon shared with many solid tumors. While established metastatic lesions behave aggressively, very few of the tumor cells that reach the lung will survive. By identifying mechanisms that facilitate survival of disseminated tumor cells, we can develop therapeutic strategies that prevent and treat metastasis.

METHODS

We analyzed single cell RNA-sequencing (scRNAseq) data from murine metastasis-bearing lungs to interrogate changes in both host and tumor cells during colonization. We used these data to elucidate pathways that become activated in cells that survive dissemination and identify candidate host-derived signals that drive activation. We validated these findings through live cell reporter systems, immunocytochemistry, and fluorescent immunohistochemistry. We then validated the functional relevance of key candidates using pharmacologic inhibition in models of metastatic osteosarcoma.

RESULTS

Expression patterns suggest that the MAPK pathway is significantly elevated in early and established metastases. MAPK activity correlates with expression of anti-apoptotic genes, especially MCL1. Niche cells produce growth factors that increase ERK phosphorylation and MCL1 expression in tumor cells. Both early and established metastases are vulnerable to MCL1 inhibition, but not MEK inhibition in vivo. Combining MCL1 inhibition with chemotherapy both prevented colonization and eliminated established metastases in murine models of osteosarcoma.

CONCLUSION

Niche-derived growth factors drive MAPK activity and MCL1 expression in osteosarcoma, promoting metastatic colonization. Although later metastases produce less MCL1, they remain dependent on it. MCL1 is a promising target for clinical trials in both human and canine patients.

Palladium (II) compounds containing oximes as promising antitumor agents for the treatment of osteosarcoma: An in vitro and in vivo comparative study with cisplatin

Drug resistance, evasion of cell death and metastasis are factors that contribute to the low cure rate and disease-free survival in osteosarcomas (OS). In this study, we demonstrated that a new class of oxime-containing organometallic complexes called Pd-BPO (O3) and Pd-BMO (O4) are more cytotoxic than cisplatin (CDDP) for SaOS-2 and U2OS cells using the MTT assay. Annexin-FITC/7-AAD staining demonstrated a greater potential for palladium-oxime complexes to induce death in SaOS-2 cells than CDDP, an event confirmed using the pan-caspase inhibitor Z-VAD-FMK. Compared to CDDP, only palladium-oxime complexes eradicated the clonogenicity of SaOS-2 cells after 7 days of treatment. The involvement of the lysosome-mitochondria axis in the cell death-inducing properties of the complexes was also evaluated. Using LysoTracker Red to label the acidic organelles of SaOS-2 cells treated with the O3 and O4 complexes, a decrease in the fluorescence intensity of this probe was observed in relation to CDDP and the control. Lysosomal membrane permeabilization (LMP) was also induced by the O3 and O4 complexes in an assay using acridine orange (A/O). The greater efficiency of the complexes in depolarizing the mitochondrial membrane compared to SaOS-2 cells treated with CDDP was also observed using TMRE (tetramethyl rhodamine, ethyl ester). For in vivo studies, C. elegans was used and demonstrated that both complexes reduce body bends and pharyngeal pumping after 24 h of treatment to the same extent as CDDP. We conclude that both palladium-oxime complexes are more effective than CDDP in inducing tumor cell death. The toxicity of these complexes to C. elegans was like that induced by CDDP. These results encourage preclinical studies aimed at developing more effective drugs for the treatment of osteosarcoma (OS). Furthermore, we propose palladium-oxime complexes as a new class of antineoplastic agents.

Patterns of metastatic progression and association with clinical outcomes in canine osteosarcoma: A necropsy study of 83 dogs

Osteosarcoma is a highly metastatic primary bone tumour that occurs spontaneously in both pet dogs and humans. Patterns of metastasis to organs beyond the most common site (lung) are poorly characterised and it is unknown whether specific associations between patterns of metastatic progression and patient features exist. This retrospective study characterised the necropsy findings of 83 dogs receiving standardised therapy and clinical monitoring in a prospective clinical trial setting to document patterns of metastasis and correlate outcomes with these patterns and other patient and tumour-specific factors. A total of 20 different sites of metastasis were documented, with lung as the most common site, followed by bone, kidney, liver, and heart. Two distinct clusters of dogs were identified based on patterns of metastasis. There was no significant association between site of enrollment, trial arm, sex, serum alkaline phosphatase (ALP) activity, or tumour location and clinical outcomes. A second cancer type was identified at necropsy in 10 dogs (10/83; 12%). These data showcase the extensive nature of osteosarcoma metastasis beyond the lung and provide a benchmark for clinical monitoring of the disease. Further, this study provides insight into transcriptional features of primary tumours that may relate to a propensity for osteosarcoma metastasis to specific organs and tissues.

A review of the development of histotripsy for extremity tumor ablation with a canine comparative oncology model to inform human treatments

Cancer is a devasting disease resulting in millions of deaths worldwide in both humans and companion animals, including dogs. Treatment of cancer is complex and challenging and therefore often multifaceted, as in the case of osteosarcoma (OS) and soft tissue sarcoma (STS). OS predominantly involves the appendicular skeleton and STS commonly develops in the extremities, resulting in treatment challenges due to the need to balance wide-margin resections to achieve local oncological control against the functional outcomes for the patient. To achieve wide tumor resection, invasive limb salvage surgery is often required, and the patient is at risk for numerous complications which can ultimately lead to impaired limb function and mobility. The advent of tumor ablation techniques offers the exciting potential of developing noninvasive or minimally invasive treatment options for extremity tumors. One promising innovative tumor ablation technique with strong potential to serve as a noninvasive limb salvage treatment for extremity tumor patients is histotripsy. Histotripsy is a novel, noninvasive, non-thermal, and non-ionizing focused ultrasound technique which uses controlled acoustic cavitation to mechanically disintegrate tissue with high precision. In this review, we present the ongoing development of histotripsy as a non-surgical alternative for extremity tumors and highlight the value of spontaneously occurring OS and STS in the pet dog as a comparative oncology research model to advance this field of histotripsy research.

Single-Nuclei Multiome (ATAC + Gene Expression) Sequencing of a Primary Canine Osteosarcoma Elucidates Intra-Tumoral Heterogeneity and Characterizes the Tumor Microenvironment

Osteosarcoma (OSA) is a highly aggressive bone tumor primarily affecting pediatric or adolescent humans and large-breed dogs. Canine OSA shares striking similarities with its human counterpart, making it an invaluable translational model for uncovering the disease's complexities and developing novel therapeutic strategies. Tumor heterogeneity, a hallmark of OSA, poses significant challenges to effective treatment due to the evolution of diverse cell populations that influence tumor growth, metastasis, and resistance to therapies. In this study, we apply single-nuclei multiome sequencing, encompassing ATAC (Assay for Transposase-Accessible Chromatin) and GEX (Gene Expression, or RNA) sequencing, to a treatment-naïve primary canine osteosarcoma. This comprehensive approach reveals the complexity of the tumor microenvironment by simultaneously capturing the transcriptomic and epigenomic profiles within the same nucleus. Furthermore, these results are analyzed in conjunction with bulk RNA sequencing and differential analysis of the same tumor and patient-matched normal bone. By delving into the intricacies of OSA at this unprecedented level of detail, we aim to unravel the underlying mechanisms driving intra-tumoral heterogeneity, opening new avenues for therapeutic interventions in both human and canine patients. This study pioneers an approach that is broadly applicable, while demonstrating significant heterogeneity in the context of a single individual's tumor.

Immune-mediated hematological disease in dogs is associated with alterations of the fecal microbiota: a pilot study

BACKGROUND

The dog is the most popular companion animal and is a valuable large animal model for several human diseases. Canine immune-mediated hematological diseases, including immune-mediated hemolytic anemia (IMHA) and immune thrombocytopenia (ITP), share many features in common with autoimmune hematological diseases of humans. The gut microbiome has been linked to systemic illness, but few studies have evaluated its association with immune-mediated hematological disease. To address this knowledge gap, 16S rRNA gene sequencing was used to profile the fecal microbiota of dogs with spontaneous IMHA and ITP at presentation and following successful treatment. In total, 21 affected and 13 healthy control dogs were included in the study.

RESULTS

IMHA/ITP is associated with remodeling of fecal microbiota, marked by decreased relative abundance of the spirochete Treponema spp., increased relative abundance of the pathobionts Clostridium septicum and Escherichia coli, and increased overall microbial diversity. Logistic regression analysis demonstrated that Treponema spp. were associated with decreased risk of IMHA/ITP (odds ratio [OR] 0.24-0.34), while Ruminococcaceae UCG-009 and Christensenellaceae R-7 group were associated with increased risk of disease (OR = 6.84 [95% CI 2-32.74] and 8.36 [95% CI 1.85-71.88] respectively).

CONCLUSIONS

This study demonstrates an association of immune-mediated hematological diseases in dogs with fecal dysbiosis, and points to specific bacterial genera as biomarkers of disease. Microbes identified as positive or negative risk factors for IMHA/ITP represent an area for future research as potential targets for new diagnostic assays and/or therapeutic applications.

Blocking tri-methylguanosine synthase 1 (TGS1) stops anchorage-independent growth of canine sarcomas

Tri methylguanosine synthase 1 (TGS1) is the enzyme that hyper methylates the hallmark 7-methyl-guanosine cap (m7G-cap) appended to the transcription start site of RNAs. The m7G-cap and the eIF4E-cap binding protein guide canonical cap-dependent translation of mRNAs, whereas hyper methylated cap, m2,2,7G-cap (TMG) lacks adequate eIF4E affinity and licenses entry into a different translation initiation pathway. The potential role for TGS1 and TMG-capped mRNA in neoplastic growth is unknown. Canine sarcoma has high translational value to the human disease. Cumulative downregulation of protein synthesis in osteosarcoma OSCA-40 was achieved cooperatively by siTGS1 and Torin-1. Torin-1 inhibited the proliferation of three canine sarcoma explants in a reversible manner that was eliminated by siRNA-downregulation of TGS1. TGS1 failure prevented the anchorage-independent growth of osteo- and hemangio-sarcomas and curtailed sarcoma recovery from mTOR inhibition. RNA immunoprecipitation studies identified TMG-capped mRNAs encoding TGS1, DHX9 and JUND. TMG-tgs1 transcripts were downregulated by leptomycin B and TGS1 failure was compensated by eIF4E mRNP-dependent tgs1 mRNA translation affected by mTOR. The evidence documents TMG-capped mRNAs are hallmarks of the investigated neoplasms and synergy between TGS1 specialized translation and canonical translation is involved in sarcoma recovery from mTOR inhibition. Therapeutic targeting of TGS1 activity in cancer is ripe for future exploration.

Use of cutting-edge RNA-sequencing technology to identify biomarkers and potential therapeutic targets in canine and feline cancers and other diseases

With the growing interest in companion animals and the rapidly expanding animal healthcare and pharmaceuticals market worldwide. With the advancements in RNA-sequencing (RNA-seq) technology, it has become a valuable tool for understanding biological processes in companion animals and has multiple applications in animal healthcare. Historically, veterinary diagnoses and treatments relied solely on clinical symptoms and drugs used in human diseases. However, RNA-seq has emerged as an effective technology for studying companion animals, providing insights into their genetic information. The sequencing technology has revealed that not only messenger RNAs (mRNAs) but also non-coding RNAs (ncRNAs) such as long ncRNAs and microRNAs can serve as biomarkers. Based on the examination of RNA-seq applications in veterinary medicine, particularly in dogs and cats, this review concludes that RNA-seq has significant potential as a diagnostic and research tool. It has enabled the identification of potential biomarkers for cancer and other diseases in companion animals. Further research and development are required to maximize the utilization of RNA-seq for improved disease diagnosis and therapeutic targeting in companion animals.

Transcriptional profiling of canine osteosarcoma identifies prognostic gene expression signatures with translational value for humans

Canine osteosarcoma is increasingly recognized as an informative model for human osteosarcoma. Here we show in one of the largest clinically annotated canine osteosarcoma transcriptional datasets that two previously reported, as well as de novo gene signatures devised through single sample Gene Set Enrichment Analysis (ssGSEA), have prognostic utility in both human and canine patients. Shared molecular pathway alterations are seen in immune cell signaling and activation including TH1 and TH2 signaling, interferon signaling, and inflammatory responses. Virtual cell sorting to estimate immune cell populations within canine and human tumors showed similar trends, predominantly for macrophages and CD8+ T cells. Immunohistochemical staining verified the increased presence of immune cells in tumors exhibiting immune gene enrichment. Collectively these findings further validate naturally occurring osteosarcoma of the pet dog as a translationally relevant patient model for humans and improve our understanding of the immunologic and genomic landscape of the disease in both species.

Dog breeds and conformations predisposed to osteosarcoma in the UK: a VetCompass study

BACKGROUND

Osteosarcoma is a malignant bone neoplasia that has high welfare consequences for affected dogs. Awareness of breed and canine conformational risk factors for osteosarcoma can assist with earlier diagnosis and improved clinical management. Study of osteosarcoma in dogs also offers translational value for humans. Anonymised clinical data within VetCompass on dogs under primary veterinary care in the UK were searched for osteosarcoma cases. Descriptive statistics reported overall and breed-specific prevalence. Risk factor analysis used multivariable logistic regression modelling.

RESULTS

From 905,552 study dogs, 331 osteosarcoma cases were confirmed yielding a one-year period prevalence of 0.037% (95% CI: 0.033-0.041). Breeds with the highest annual prevalence were the Scottish Deerhound (3.28%, 95% CI 0.90-8.18), Leonberger (1.48%, 95% CI 0.41- 3.75), Great Dane (0.87%, 95% CI 0.43- 1.55) and Rottweiler (0.84%, 95% CI 0.64-1.07). The median age at diagnosis was 9.64 years (IQR: 7.97-11.41). Following multivariable modelling, 11 breeds showed increased odds of osteosarcoma compared with crossbred dogs. Breeds with the highest odds included Scottish Deerhound (OR 118.40, 95% CI 41.12-340.95), Leonberger (OR 55.79, 95% CI 19.68-158.15), Great Dane (OR 34.24, 95% CI 17.81-65.83) and Rottweiler (OR 26.67, 95% CI 18.57-38.29). Compared with breeds with mesocephalic skull conformation, breeds with dolichocephalic skull conformation (OR 2.72, 95% CI 2.06-3.58) had increased odds while breeds with brachycephalic skull conformation showed reduced odds (OR 0.50, 95% CI 0.32-0.80). Chondrodystrophic breeds had 0.10 times the odds (95% CI 0.06-0.15) compared with non-chondrodystrophic breeds. Increasing adult bodyweight was associated with increasing odds of osteosarcoma.

CONCLUSIONS

The current study cements the concept that breed, bodyweight and longer leg or longer skull length are all strong risk factors for osteosarcoma in dogs. With this awareness, veterinarians can update their clinical suspicion and judgement, breeders can select towards lower-risk animals, and researchers can robustly define more useful study populations for fundamental and translational bioscience.

Epigenetic Changes Associated with Osteosarcoma: A Comprehensive Review

Osteosarcoma is the most common malignant primary bone tumor in children and adolescents. While clinical outcomes have improved, the 5-year survival rate is only around 60% if discovered early and can require debilitating treatments, such as amputations. A better understanding of the disease could lead to better clinical outcomes for patients with osteosarcoma. One promising avenue of osteosarcoma research is in the field of epigenetics. This research investigates changes in genetic expression that occur above the genome rather than in the genetic code itself. The epigenetics of osteosarcoma is an active area of research that is still not fully understood. In a narrative review, we examine recent advances in the epigenetics of osteosarcoma by reporting biomarkers of DNA methylation, histone modifications, and non-coding RNA associated with disease progression. We also show how cancer tumor epigenetic profiles are being used to predict and improve patient outcomes. The papers in this review cover a large range of epigenetic target genes and pathways that modulate many aspects of osteosarcoma, including but not limited to metastases and chemotherapy resistance. Ultimately, this review will shed light on the recent advances in the epigenetics of osteosarcoma and illustrate the clinical benefits of this field of research.

Gold Nanoparticles Inhibit Extravasation of Canine Osteosarcoma Cells in the Ex Ovo Chicken Embryo Chorioallantoic Membrane Model

Canine osteosarcoma (OS) is an aggressive bone tumor with high metastatic potential and poor prognosis, mainly due to metastatic disease. Nanomedicine-based agents can be used to improve both primary and metastatic tumor treatment. Recently, gold nanoparticles were shown to inhibit different stages of the metastatic cascade in various human cancers. Here, we assessed the potential inhibitory effect of the glutathione-stabilized gold nanoparticles (Au-GSH NPs) on canine OS cells extravasation, utilizing the ex ovo chick embryo chorioallantoic membrane (CAM) model. The calculation of cells extravasation rates was performed using wide-field fluorescent microscopy. Transmission electron microscopy and Microwave Plasma Atomic Emission Spectroscopy revealed Au-GSH NPs absorption by OS cells. We demonstrated that Au-GSH NPs are non-toxic and significantly inhibit canine OS cells extravasation rates, regardless of their aggressiveness phenotype. The results indicate that Au-GSH NPs can act as a possible anti metastatic agent for OS treatment. Furthermore, the implemented CAM model may be used as a valuable preclinical platform in veterinary medicine, such as testing anti-metastatic agents.

Isolation and Characterization of Novel Canine Osteosarcoma Cell Lines from Chemotherapy-Naïve Patients

The present study aimed to establish novel canine osteosarcoma cell lines (COS3600, COS3600B, COS4074) and characterize the recently described COS4288 cells. The established D-17 cell line served as a reference. Analyzed cell lines differed notably in their biological characteristics. Calculated doubling times were between 22 h for COS3600B and 426 h for COS4074 cells. COS3600B and COS4288 cells produced visible colonies after anchorage-independent growth in soft agar. COS4288 cells were identified as cells with the highest migratory capacity. All cells displayed the ability to invade through an artificial basement membrane matrix. Immunohistochemical analyses revealed the mesenchymal origin of all COS cell lines as well as positive staining for the osteosarcoma-relevant proteins alkaline phosphatase and karyopherin α2. Expression of p53 was confirmed in all tested cell lines. Gene expression analyses of selected genes linked to cellular immune checkpoints (CD270, CD274, CD276), kinase activity (MET, ERBB2), and metastatic potential (MMP-2, MMP-9) as well as selected long non-coding RNA (MALAT1) and microRNAs (miR-9, miR-34a, miR-93) are provided. All tested cell lines were able to grow as multicellular spheroids. In all spheroids except COS4288, calcium deposition was detected by von Kossa staining. We believe that these new cell lines serve as useful biological models for future studies.

Using cultured canine cardiac slices to model the autophagic flux with doxorubicin

Chemotherapy-induced impairment of autophagy is implicated in cardiac toxicity induced by anti-cancer drugs. Imperfect translation from rodent models and lack of in vitro models of toxicity has limited investigation of autophagic flux dysregulation, preventing design of novel cardioprotective strategies based on autophagy control. Development of an adult heart tissue culture technique from a translational model will improve investigation of cardiac toxicity. We aimed to optimize a canine cardiac slice culture system for exploration of cancer therapy impact on intact cardiac tissue, creating a translatable model that maintains autophagy in culture and is amenable to autophagy modulation. Canine cardiac tissue slices (350 μm) were generated from left ventricular free wall collected from euthanized client-owned dogs (n = 7) free of cardiovascular disease at the Foster Hospital for Small Animals at Tufts University. Cell viability and apoptosis were quantified with MTT assay and TUNEL staining. Cardiac slices were challenged with doxorubicin and an autophagy activator (rapamycin) or inhibitor (chloroquine). Autophagic flux components (LC3, p62) were quantified by western blot. Cardiac slices retained high cell viability for >7 days in culture and basal levels of autophagic markers remained unchanged. Doxorubicin treatment resulted in perturbation of the autophagic flux and cell death, while rapamycin co-treatment restored normal autophagic flux and maintained cell survival. We developed an adult canine cardiac slice culture system appropriate for studying the effects of autophagic flux that may be applicable to drug toxicity evaluations.

Endogenous Extracellular Matrix Regulates the Response of Osteosarcoma 3D Spheroids to Doxorubicin

The extracellular matrix (ECM) modulates cell behavior, shape, and viability as well as mechanical properties. In recent years, ECM disregulation and aberrant remodeling has gained considerable attention in cancer targeting and prevention since it may stimulate tumorigenesis and metastasis. Here, we developed an in vitro model that aims at mimicking the in vivo tumor microenvironment by recapitulating the interactions between osteosarcoma (OS) cells and ECM with respect to cancer progression. We long-term cultured 3D OS spheroids made of metastatic or non-metastatic OS cells mixed with mesenchymal stromal cells (MSCs); confirmed the deposition of ECM proteins such as Type I collagen, Type III collagen, and fibronectin by the stromal component at the interface between tumor cells and MSCs; and found that ECM secretion is inhibited by a neutralizing anti-IL-6 antibody, suggesting a new role of this cytokine in OS ECM deposition. Most importantly, we showed that the cytotoxic effect of doxorubicin is reduced by the presence of Type I collagen. We thus conclude that ECM protein deposition is crucial for modelling and studying drug response. Our results also suggest that targeting ECM proteins might improve the outcome of a subset of chemoresistant tumors.

Cataracts Across the Tree of Life: A Roadmap for Prevention and Biomedical Innovation

PURPOSE

Spontaneous cataracts have been identified in the lenses of animals across a phylogenetically wide range of species. This can be a source of insights and innovation for human health professionals, but many persons may lack awareness of it. By providing a phylogenetic survey and analysis of species with cataract vulnerability, this paper demonstrates how a broad comparative perspective can provide critical information about environmental hazards to human visual health and can spark potential innovations in the prevention and treatment of cataracts in humans.

DESIGN

Perspectives.

METHODS

Review and synthesis of selected literature with interpretation and perspective.

RESULTS

We found 273 recorded cases of spontaneously occurring cataracts in 113 species of birds, 83 species of mammals, 30 species of actinopterygii fish, 10 species of amphibians, 6 species of reptiles, and 1 species of cephalopod.

CONCLUSION

A phylogenetically wide range of species, including many living in and around human environments, are vulnerable to cataracts. These animals may serve as sentinels for human visual health. Variation in cataract vulnerability across species may also facilitate the identification of resistance-conferring physiologies, leading to accelerated innovation in the prevention and treatment of cataracts in humans.

Characterizing the Ablative Effects of Histotripsy for Osteosarcoma: In Vivo Study in Dogs

Osteosarcoma (OS) is a malignant bone tumor treated by limb amputation or limb salvage surgeries and chemotherapy. Histotripsy is a non-thermal, non-invasive focused ultrasound therapy using controlled acoustic cavitation to mechanically disintegrate tissue. Recent ex vivo and in vivo pilot studies have demonstrated the ability of histotripsy for ablating OS but were limited in scope. This study expands on these initial findings to more fully characterize the effects of histotripsy for bone tumors, particularly in tumors with different compositions. A prototype 500 kHz histotripsy system was used to treat ten dogs with suspected OS at an intermediate treatment dose of 1000 pulses per location. One day after histotripsy, treated tumors were resected via limb amputation, and radiologic and histopathologic analyses were conducted to determine the effects of histotripsy for each patient. The results of this study demonstrated that histotripsy ablation is safe and feasible in canine patients with spontaneous OS, while offering new insights into the characteristics of the achieved ablation zone. More extensive tissue destruction was observed after histotripsy compared to that in previous reports, and radiographic changes in tumor size and contrast uptake following histotripsy were reported for the first time. Overall, this study significantly expands our understanding of histotripsy bone tumor ablation and informs future studies for this application.

Nanocarriers in Veterinary Medicine: A Challenge for Improving Osteosarcoma Conventional Treatments

In recent years, several nanocarrier-based drug delivery systems, such as polymeric nanoparticles, solid lipid nanoparticles, metallic nanoparticles, liposomes, and others, have been explored to target and treat a wide variety of diseases. Their employment has brought many benefits, not only to human medicine but also to veterinary medicine, albeit at a slower rate. Soon, the use of nanocarriers could revolutionize the animal health sector, and many veterinary therapies will be more effective as a result. The purpose of this review is to offer an overview of the main applications of nanocarriers in the veterinary field, from supplements for animal health and reproduction to nanovaccines and nanotherapies. Among the major pathologies that can affect animals, special attention is given to canine osteosarcoma (OSA): a comparison with human OSA is provided and the main treatment options are reviewed emphasizing the benefits that nanocarriers could bring in the treatment of this widespread disease.

Improving Osteosarcoma Treatment: Comparative Oncology in Action

Osteosarcoma (OSA) is the most common pediatric malignant bone tumor. Although surgery together with neoadjuvant/adjuvant chemotherapy has improved survival for localized OSA, most patients develop recurrent/metastatic disease with a dismally poor outcome. Therapeutic options have not improved for these OSA patients in recent decades. As OSA is a rare and "orphan" tumor, with no distinct targetable driver antigens, the development of new efficient therapies is still an unmet and challenging clinical need. Appropriate animal models are therefore critical for advancement in the field. Despite the undoubted relevance of pre-clinical mouse models in cancer research, they present some intrinsic limitations that may be responsible for the low translational success of novel therapies from the pre-clinical setting to the clinic. From this context emerges the concept of comparative oncology, which has spurred the study of pet dogs as a uniquely valuable model of spontaneous OSA that develops in an immune-competent system with high biological and clinical similarities to corresponding human tumors, including in its metastatic behavior and resistance to conventional therapies. For these reasons, the translational power of studies conducted on OSA-bearing dogs has seen increasing recognition. The most recent and relevant veterinary investigations of novel combinatorial approaches, with a focus on immune-based strategies, that can most likely benefit both canine and human OSA patients have been summarized in this commentary.

Canine osteosarcoma in comparative oncology: Molecular mechanisms through to treatment discovery

Cancer is a leading cause of non-communicable morbidity and mortality throughout the world, similarly, in dogs, the most frequent cause of mortality is tumors. Some types of cancer, including osteosarcoma (OSA), occur at much higher rates in dogs than people. Dogs therefore not only require treatment themselves but can also act as an effective parallel patient population for the human disease equivalent. It should be noted that although there are many similarities between canine and human OSA, there are also key differences and it is important to research and highlight these features. Despite progress using chorioallantoic membrane models, 2D and 3D in vitro models, and rodent OSA models, many more insights into the molecular and cellular mechanisms, drug development, and treatment are being discovered in a variety of canine OSA patient populations.

Osteosarcoma

Osteosarcoma is the most common primary malignant tumour of the bone. Osteosarcoma incidence is bimodal, peaking at 18 and 60 years of age, and is slightly more common in males. The key pathophysiological mechanism involves several possible genetic drivers of disease linked to bone formation, causing malignant progression and metastasis. While there have been significant improvements in the outcome of patients with localized disease, with event-free survival outcomes exceeding 60%, in patients with metastatic disease, event-free survival outcomes remain poor at less than 30%. The suspicion of osteosarcoma based on radiographs still requires pathological evaluation of a bone biopsy specimen for definitive diagnosis and CT imaging of the chest should be performed to identify lung nodules. So far, population-based screening and surveillance strategies have not been implemented due to the rarity of osteosarcoma and the lack of reliable markers. Current screening focuses only on groups at high risk such as patients with genetic cancer predisposition syndromes. Management of osteosarcoma requires a multidisciplinary team of paediatric and medical oncologists, orthopaedic and general surgeons, pathologists, radiologists and specialist nurses. Survivors of osteosarcoma require specialized medical follow-up, as curative treatment consisting of chemotherapy and surgery has long-term adverse effects, which also affect the quality of life of patients. The development of osteosarcoma model systems and related research as well as the evaluation of new treatment approaches are ongoing to improve disease outcomes, especially for patients with metastases.

The safety and efficiency of photodynamic therapy for the treatment of osteosarcoma: A systematic review of in vitro experiment and animal model reports

BACKGROUND

Osteosarcoma (OS) is an aggressive malignant bone tumour with high mortality. A poor prognosis is noted in patients with distal metastases or multidrug resistance. As an emerging antitumor strategy, photodynamic therapy (PDT) mediated by visible and near infrared light has attracted intensive attention given its target selectivity, remote controllability, minimal or non-invasive features. However, PDT also has obvious limitations. Specifically, due to the limited penetration of light, it is mainly used in the clinical treatment of superficial malignant tumours, such as musculoskeletal sarcomas and melanoma, but it has not been applied to the clinical treatment of deep malignant bone tumours except for a very small number of experiments on deep canine OS models.

MATERIALS AND METHODS

We searched for studies that focused on the effectiveness and safety of PDT for OS based on in vitro experiments and animal models in the last decade. A systematic search was conducted using electronic databases, including PubMed, ClinicalTrials.gov, and the Cochrane Library.

INCLUSION CRITERIA

(1) original research articles about PDT for OS; (2) articles in English; (3) in vitro or animal model research; and (4) detailed information, including cell name, fluence, irradiation wavelength, time of incubation with PS, duration between PS treatment and irradiation, and duration between irradiation and viability assays.

EXCLUSION CRITERIA

(1) study was a review/systemic review article, patent, letter, or conference abstract/paper; (2) articles were not published in English; (3) studies containing overlapping or insufficient data.

RESULTS

We identified 201 publications, and 44 articles met the inclusion criteria and were included in the synthesis. Unfortunately, there are no relevant clinical reports of the use of PDT in the treatment of human OS. In these studies, 8 studies only employed in vivo experiments to evaluate the efficiency of PDT in an OS animal model, 19 studies exclusively performed in vitro viability assays of cells treated with PDT under different conditions, and 17 studies included in vitro cell experiments and in vivo animal OS models to evaluate the effect of PDT on OS in vivo and in vitro. All studies have shown that PDT is cytotoxic to OS cells or can inhibit the growth of OS in heterologous or homologous animal OS models but exhibits minimal cytotoxicity at a certain range of dosages.

CONCLUSION

Based on this systematic review, PDT can eradicate OS cells in cell culture and there is some evidence for efficacy in animal models. However, the ability for PDT to control human OS is unclear, the animal and human reports do not show evidence of human OS control, they just do show feasibility. The major issues concerning the potential for treatment of osteosarcoma with PDT are that adequate light should be transmitted to tumor loci and if the disease is caught before metastasis and irradiation of tumor sites is feasible, curative potential is there. Otherwise, PDT may be mainly palliative. To determine whether PDT can safely and efficiently be used in the clinical treatment of OS, many preclinical orthotopic animal OS models and OS models of multiple systemic metastases must be performed and interstitial PDT or intraoperative PDT may be a good and potential candidate for human OS treatment. If these problems can be well solved, PDT may be a potentially effective strategy for the treatment of OS patients.

Anti-GD2 antibody for radiopharmaceutical imaging of osteosarcoma

PURPOSE

Osteosarcoma (OS) is the most frequently diagnosed bone cancer in children with little improvement in overall survival in the past decades. The high surface expression of disialoganglioside GD2 on OS tumors and restricted expression in normal tissues makes it an ideal target for anti-OS radiopharmaceuticals. Since human and canine OS share many biological and molecular features, spontaneously occurring OS in canines has been an ideal model for testing new imaging and treatment modalities for human translation. In this study, we evaluated a humanized anti-GD2 antibody, hu3F8, as a potential delivery vector for targeted radiopharmaceutical imaging of human and canine OS.

METHODS

The cross-reactivity of hu3F8 with human and canine OS cells and tumors was examined by immunohistochemistry and flow cytometry. The hu3F8 was radiolabeled with indium-111, and the biodistribution of [¹¹¹In]In-hu3F8 was assessed in tumor xenograft-bearing mice. The targeting ability of [¹¹¹In]In-hu3F8 to metastatic OS was tested in spontaneous OS canines.

RESULTS

The hu3F8 cross reacts with human and canine OS cells and canine OS tumors with high binding affinity. Biodistribution studies revealed selective uptake of [¹¹¹In]In-hu3F8 in tumor tissue. SPECT/CT imaging of spontaneous OS canines demonstrated avid uptake of [¹¹¹In]In-hu3F8 in all metastatic lesions. Immunohistochemistry confirmed the extensive binding of radiolabeled hu3F8 within both osseous and soft lesions.

CONCLUSION

This study demonstrates the feasibility of targeting GD2 on OS cells and spontaneous OS canine tumors using hu3F8-based radiopharmaceutical imaging. Its ability to deliver an imaging payload in a targeted manner supports the utility of hu3F8 for precision imaging of OS and potential future use in radiopharmaceutical therapy.

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.

Canine Idiopathic Arteriopathy, Appendicular Bone Infarcts, and Neoplastic Transformation of Bone Infarcts in 108 Dogs (Canis lupus familiaris)

Osteosarcoma (OSA) is the most common primary bone tumor in both dogs and humans. The dog is an important research model for OSA, yet dogs have much higher prevalence of bone tumors than do humans, a disparity that has yet to be explained. Neoplastic transformation of cells within or adjacent to bone infarcts into primary bone tumors has been described in humans but only sparsely characterized in the veterinary literature. In this study, 653 cases of canine bone infarcts were received through a referral veterinary osteopathology service over a 14-y period. We identified an idiopathic disorder affecting the nutrient artery, termed canine idiopathic arteriopathy (CIA), which to our knowledge has no direct counterpart in human medicine. This disorder was documented alongside ischemic necrosis of the medullary cavity in 114 bone infarcts in 108 dogs. We hypothesize that CIA precipitated an ischemic environment, resulting in development of a bone infarct down- stream of the abnormal artery. In 52% (59 of 114) of cases, bone infarcts demonstrated evidence of repair (termed reparative bone infarcts [RBI]), while in 48% (55 of 114) of infarcts, a bone tumor was also present, including pleomorphic sarcoma, OSA, fibrosarcoma, and chondrosarcoma. In some cases, a spectrum of tumors was present. We hypothesize that the ischemic infarct environment provoked bone marrow mesenchymal stem cells (MSCs) to attempt repair of the stroma, and in approximately half of cases, MSCs underwent neoplastic transformation (BINT) to produce tumors. The most common sites of bone infarcts were the distal femur, distal radius, proximal humerus, and distal tibia, coinciding with common sites of canine OSA. The authors propose that CIA leading to bone infarcts and infarct-derived tumors, in combination with possible underdiagnosis of canine bone infarcts and misdiagnosis of some RBI as neoplasia, may contribute to the higher reported proportion of bone tumors in dogs compared with humans.

Proteasome Inhibitors and Their Potential Applicability in Osteosarcoma Treatment

Simple Summary

Bone cancer has seen minimal benefits in therapeutic options in the past 30 years. Proteasome inhibitors present a new avenue of research for the treatment of bone cancer. Proteasome inhibitors impair the function of the proteasome, a structure within the cell that removes unwanted and misfolded proteins. Bone cancer cells heavily rely on the proteasome to properly function and survive. Impairing the proteasome function can have detrimental consequences and lead to cell death. This review provides a thorough summary of the in vitro, in vivo, and clinical research that has explored proteasome inhibitors for the treatment of bone cancer.

Abstract

Osteosarcoma (OS) is the most common type of bone cancer, with ~30% of patients developing secondary/metastatic tumors. The molecular complexity of tumor metastasis and the lack of effective therapies for OS has cultivated interest in exploiting the proteasome as a molecular target for anti-cancer therapy. As our understanding towards the behavior of malignant cells expands, it is evident that cancerous cells display a greater reliance on the proteasome to maintain homeostasis and sustain efficient biological activities. This led to the development and approval of first- and second-generation proteasome inhibitors (PIs), which have improved outcomes for patients with multiple myeloma and mantle cell lymphoma. Researchers have since postulated the therapeutic potential of PIs for the treatment of OS. As such, this review aims to summarize the biological effects and latest findings from clinical trials investigating PI-based treatments for OS. Integrating PIs into current treatment regimens may better outcomes for patients diagnosed with OS.

Anticancer activity of an Artemisia annua L. hydroalcoholic extract on canine osteosarcoma cell lines

Since ancient times, Artemisia annua (A. annua) has been used as a medicinal plant in Traditional Chinese Medicine. In addition, recent studies have investigated the cytotoxic effects of A. annua extracts towards cancer cells. The leading aim of the present research is to evaluate the cytotoxic effects of an hydroalcoholic extract of A. annua on two canine osteosarcoma (OSA) cell lines, OSCA-8 and OSCA-40, focusing on the possible involvement of ferroptosis. The quantitative determination of artemisinin concentration in the extract, culture medium and OSA cells was carried out through the use of an instrumental analytical method based on liquid chromatography coupled with spectrophotometric detection and tandem mass spectrometry (LC-DAD-MS/MS). OSCA-8 and OSCA-40 were exposed to different dilutions of the extract for the EC₅₀ calculation then the uptake of artemisinin by the cells, the effects on the cell cycle, the intracellular iron level, the cellular morphology and the lipid oxidation state were evaluated. A concentration of artemisinin of 63.8 ± 3.4 μg/mL was detected in the extract. A dose-dependent cytotoxic effect was evidenced. In OSCA-40 alterations of the cell cycle and a significantly higher intracellular iron content were observed. In both cell lines the treatment with the extract was associated with lipid peroxidation and with the appearance of a "ballooning" phenotype suggesting the activation of ferroptosis. In conclusion the A. annua idroalcoholic extract utilized in this study showed anticancer activity on canine OSA cell lines that could be useful in treating drug resistant canine OSAs.

The Italian Network of Laboratories for Veterinary Oncology (NILOV) 2.0: Improving Knowledge on Canine Tumours

Simple Summary

Advances in cancer research are crucial, and pet oncology can improve the knowledge in several ways. Dogs are not only models of specific naturally occurring tumours but can also be sentinels of environmental exposures to carcinogenic substances, as they share the same environment with their owners. The purpose of this work was to describe the data collected by The Italian Network of Laboratories for Veterinary Oncology in the first 9 years of activity (2013–2021) and to evaluate their potential epidemiological significance. Frequencies of tumour sites in dogs were described, analysed and compared, considering several risk factors (breed, sex, period and region of residence). These observations allowed us to highlight differences not only in the site of occurrence of some tumours but also to formulate hypotheses on the potential role of some risk factors, e.g., neutering/spaying or geographical location. In our opinion, the results of this study confirm the importance of initiating and consolidating animal cancer registration initiatives that would facilitate the possibility of conducting multicentric collaborative studies to deepen the knowledge of the epidemiology of tumours in dogs and, from a comparative perspective, in humans.

Abstract

Advances in tumour research are crucial, and comparative oncology can improve the knowledge in several ways. Dogs are not only models of specific naturally occurring tumours but can also be sentinels of environmental exposures to carcinogens, as they share the same environment with their owners. The purpose of this work was to describe the data collected by The Italian Network of Laboratories for Veterinary Oncology in the first 9 years of activity (2013–2021) and to evaluate their potential epidemiological significance. Frequencies of tumour topographies and main morphologies in dogs were described, analysed and compared, calculating age-adjusted proportional morbidity ratios and considering several risk factors (breed, sex, period and region of residence). These observations allowed us to highlight differences not only in morphology and topography of some tumours but also to formulate hypotheses on the potential role of some risk factors, e.g., neutering/spaying or geographical location. In our opinion, the results of this case series confirm the importance of initiating and consolidating animal cancer registration initiatives that would facilitate the possibility of conducting multicentric collaborative studies to deepen the knowledge of the epidemiology of tumours in dogs from a comparative perspective.

Lipid droplets and perilipins in canine osteosarcoma. Investigations on tumor tissue, 2D and 3D cell culture models

Lipid droplets were identified as important players in biological processes of various tumor types. With emphasis on lipid droplet-coating proteins (perilipins, PLINs), this study intended to shed light on the presence and formation of lipid droplets in canine osteosarcoma. For this purpose, canine osteosarcoma tissue samples (n = 11) were analyzed via immunohistochemistry and electron microscopy for lipid droplets and lipid droplet-coating proteins (PLINs). Additionally, we used the canine osteosarcoma cell lines D-17 and COS4288 in 2D monolayer and 3D spheroid (cultivated for 7, 14, and 21 days) in vitro models, and further analyzed the samples by means of histochemistry, immunofluorescence, molecular biological techniques (RT-qPCR, Western Blot) and electron microscopical imaging. Lipid droplets, PLIN2, and PLIN3 were detected in osteosarcoma tissue samples as well as in 2D and 3D cultivated D-17 and COS4288 cells. In spheroids, specific distribution patterns of lipid droplets and perilipins were identified, taking into consideration cell line specific zonal apportionment. Upon external lipid supplementation (oleic acid), a rise of lipid droplet amount accompanied with an increase of PLIN2 expression was observed. Detailed electron microscopical analyzes revealed that lipid droplet sizes in tumor tissue were comparable to that of 3D spheroid models. Moreover, the biggest lipid droplets were found in the central zone of the spheroids at all sampling time-points, reaching their maximum size at 21 days. Thus, the 3D spheroids can be considered as a relevant in vitro model for further studies focusing on lipid droplets biology and function in osteosarcoma.

Doxorubicin-Loaded Lipid Nanoparticles Coated with Calcium Phosphate as a Potential Tool in Human and Canine Osteosarcoma Therapy

Osteosarcoma (OSA) is the most frequently diagnosed primary malignant bone tumor in humans and dogs. In both species, standard chemotherapy can be limited by multidrug resistance of neoplastic cells, which prevents intracellular accumulation of cytotoxic drugs, resulting in chemotherapy failure. In this study, a lipophilic ester of doxorubicin (C12DOXO) was loaded into nanoparticles (NPs) using the “cold microemulsion dilution” method. The resulting NPs were then coated with calcium phosphate (CaP) in two different ways to have calcium or phosphate ions externally exposed on the surface. These systems were characterized by determining mean diameter, zeta potential, and drug entrapment efficiency; afterward, they were tested on human and canine OSA cells to study the role that the coating might play in increasing both drug uptake into tumor cells and cytotoxicity. Mean diameter of the developed NPs was in the 200–300 nm range, zeta potential depended on the coating type, and C12DOXO entrapment efficiency was in the 60–75% range. Results of studies on human and canine OSA cells were very similar and showed an increase in drug uptake and cytotoxicity for CaP-coated NPs, especially when calcium ions were externally exposed. Therefore, applications in both human and veterinary medicine can be planned in the near future.

Expression of the hedgehog signaling pathway and the effect of inhibition at the level of Smoothened in canine osteosarcoma cell lines

Osteosarcoma (OSA) is the most common malignant bone cancer in dogs. Canine and human OSA share several features, including tumor environments, response to traditional treatment, and several molecular pathways. Hedgehog (Hh) signaling is known to contribute to tumorigenesis and progression of various cancers, including human OSA. This study aimed to identify the role of the Hh signaling pathway in canine OSA cell lines, including Abrams, D17, and Moresco, focusing on the signal transducer Smoothened (SMO). mRNA and protein levels of Hh pathway components, including SHH, IHH, SMO, and PTCH1, were aberrant in all examined OSA cell lines compared with canine osteoblast cells. The SMO inhibitor cyclopamine significantly decreased cell viability and colony-forming ability in the canine OSA cell lines in a dose-dependent manner. Moresco cells, which expressed the highest level of SMO protein, were the most sensitive to the anticancer effect of cyclopamine among the three canine OSA cell lines tested. Hh downstream target gene and protein expression in canine OSA cell lines were downregulated after cyclopamine treatment. In addition, cyclopamine significantly increased apoptotic cell death in Abrams and Moresco cells. The findings that Hh/SMO is activated in canine OSA cell lines and cyclopamine suppresses OSA cell survival via inhibition of SMO suggest that the Hh/SMO signaling pathway might be a novel therapeutic target for canine OSA. This article is protected by copyright. All rights reserved.

Comparative analysis of genome-wide DNA methylation identifies patterns that associate with conserved transcriptional programs in osteosarcoma

Osteosarcoma is an aggressive tumor of the bone that primarily affects young adults and adolescents. Osteosarcoma is characterized by genomic chaos and heterogeneity. While inactivation of tumor protein p53 (TP53) is nearly universal other high frequency mutations or structural variations have not been identified. Despite this genomic heterogeneity, key conserved transcriptional programs associated with survival have been identified across human, canine and induced murine osteosarcoma. The epigenomic landscape, including DNA methylation, plays a key role in establishing transcriptional programs in all cell types. The role of epigenetic dysregulation has been studied in a variety of cancers but has yet to be explored at scale in osteosarcoma. Here we examined genome-wide DNA methylation patterns in 24 human and 44 canine osteosarcoma samples identifying groups of highly correlated DNA methylation marks in human and canine osteosarcoma samples. We also link specific DNA methylation patterns to key transcriptional programs in both human and canine osteosarcoma. Building on previous work, we built a DNA methylation-based measure for the presence and abundance of various immune cell types in osteosarcoma. Finally, we determined that the underlying state of the tumor, and not changes in cell composition, were the main driver of differences in DNA methylation across the human and canine samples. SIGNIFICANCE: Genome wide comparison of DNA methylation patterns in osteosarcoma across two species lays the ground work for the exploration of DNA methylation programs that help establish conserved transcriptional programs in the context of varied mutational landscapes.

Canine and murine models of osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor in children. Despite efforts to develop and implement new therapies, patient outcomes have not measurably improved since the 1980s. Metastasis continues to be the main source of patient mortality, with 30% of cases developing metastatic disease within 5 years of diagnosis. Research models are critical in the advancement of cancer research and include a variety of species. For example, xenograft and patient-derived xenograft (PDX) mouse models provide opportunities to study human tumor cells in vivo while transgenic models have offered significant insight into the molecular mechanisms underlying OS development. A growing recognition of naturally occurring cancers in companion species has led to new insights into how veterinary patients can contribute to studies of cancer biology and drug development. The study of canine cases, including the use of diagnostic tissue archives and clinical trials, offers a potential mechanism to further canine and human cancer research. Advancement in the field of OS research requires continued development and appropriate use of animal models. In this review, animal models of OS are described with a focus on the mouse and tumor-bearing pet dog as parallel and complementary models of human OS.

Proteomic Assessment of Extracellular Vesicles from Canine Tissue Explants as a Pipeline to Identify Molecular Targets in Osteosarcoma: PSMD14/Rpn11 as a Proof of Principle

Osteosarcoma (OS) is a highly malignant bone tumour that has seen little improvement in treatment modalities in the past 30 years. Understanding what molecules contribute to OS biology could aid in the discovery of novel therapies. Extracellular vesicles (EVs) serve as a mode of cell-to-cell communication and have the potential to uncover novel protein signatures. In our research, we developed a novel pipeline to isolate, characterize, and profile EVs from normal bone and osteosarcoma tissue explants from canine OS patients. Proteomic analysis of vesicle preparations revealed a protein signature related to protein metabolism. One molecule of interest, PSMD14/Rpn11, was explored further given its prognostic potential in human and canine OS, and its targetability with the drug capzimin. In vitro experiments demonstrated that capzimin induces apoptosis and reduces clonogenic survival, proliferation, and migration in two metastatic canine OS cell lines. Capzimin also reduces the viability of metastatic human OS cells cultured under 3D conditions that mimic the growth of OS cells at secondary sites. This unique pipeline can improve our understanding of OS biology and identify new prognostic markers and molecular targets for both canine and human OS patients.

Increased risk of cancer in dogs and humans: a consequence of recent extension of lifespan beyond evolutionarily-determined limitations?

Cancer is among the most common causes of death for dogs (and cats) and humans in the developed world, even though it is uncommon in wildlife and other domestic animals. We provide a rationale for this observation based on recent advances in our understanding of the evolutionary basis of cancer. Over the course of evolutionary time, species have acquired and fine-tuned adaptive cancer protective mechanisms that are intrinsically related to their energy demands, reproductive strategies, and expected lifespan. These cancer protective mechanisms are general across species and/or specific to each species and their niche, and they do not seem to be limited in diversity. The evolutionarily acquired cancer-free longevity that defines a species' life history can explain why the relative cancer risk, rate, and incidence are largely similar across most species in the animal kingdom despite differences in body size and life expectancy. The molecular, cellular, and metabolic events that promote malignant transformation and cancerous growth can overcome these adaptive, species-specific protective mechanisms in a small proportion of individuals, while independently, some individuals in the population might achieve exceptional longevity. In dogs and humans, recent dramatic alterations in healthcare and social structures have allowed increasing numbers of individuals in both species to far exceed their species-adapted longevities (by 2-4 times) without allowing the time necessary for compensatory natural selection. In other words, the cancer protective mechanisms that restrain risk at comparable levels to other species for their adapted lifespan are incapable of providing cancer protection over this recent, drastic and widespread increase in longevity.

ALDH1A1 Gene Expression and Cellular Copper Levels between Low and Highly Metastatic Osteosarcoma Provide a Case for Novel Repurposing with Disulfiram and Copper

Aldehyde dehydrogenase 1A1 (ALDH) is a cancer stem cell marker highly expressed in metastatic cells. Disulfiram (Dis) is an FDA-approved antialcoholism drug that inhibits ALDH and has been studied as a candidate for drug repurposing in multiple neoplasia. Dis cytotoxicity in cancer cells has been shown to be copper-dependent, in part due to Dis's ability to function as a bivalent metal ion chelator of copper (Cu). The objectives of this research were to test ALDH expression levels and Cu concentrations in sarcoma patient tumors and human osteosarcoma (OS) cell lines with differing metastatic phenotypes. We also sought to evaluate Dis + Cu combination therapy in human OS cells. Intracellular Cu was inversely proportional to the metastatic phenotype in human OS cell lines (SaOS2 > LM2 > LM7). Nonmetastatic human sarcoma tumors demonstrated increased Cu concentrations compared with metastatic tumors. qPCR demonstrated that ALDH expression was significantly increased in highly metastatic LM2 and LM7 human OS cell lines compared with low metastatic SaOS2. Tumor cells from sarcoma patients with metastatic disease displayed significantly increased ALDH expression compared with tumor cells from patients without metastatic disease. Serum Cu concentration in canine OS versus normal canine patients demonstrated similar trends. Dis demonstrated selective cytotoxicity compared with human multipotential stromal cells (MSCs): Dis-treated OS cells demonstrated increased apoptosis, whereas MSCs did not. CuCl₂ combined with Dis and low-dose doxorubicin resulted in a superior cytotoxic effect in both SaOS2 and LM7 cell lines. In summary, ALDH gene expression and Cu levels are altered between low and highly metastatic human OS cells, canine samples, and patient tumors. Our findings support the feasibility of a repurposed drug strategy for Dis and Cu in combination with low-dose anthracycline to specifically target metastatic OS cells.

Histotripsy Ablation in Preclinical Animal Models of Cancer and Spontaneous Tumors in Veterinary Patients: A Review

New therapeutic strategies are direly needed in the fight against cancer. Over the last decade, several tumor ablation strategies have emerged as stand-alone or combination therapies. Histotripsy is the first completely noninvasive, nonthermal, and nonionizing tumor ablation method. Histotripsy can produce consistent and rapid ablations, even near critical structures. Additional benefits include real-time image guidance, high precision, and the ability to treat tumors of any predetermined size and shape. Unfortunately, the lack of clinically and physiologically relevant preclinical cancer models is often a significant limitation with all focal tumor ablation strategies. The majority of studies testing histotripsy for cancer treatment have focused on small animal models, which have been critical in moving this field forward and will continue to be essential for providing mechanistic insight. While these small animal models have notable translational value, there are significant limitations in terms of scale and anatomical relevance. To address these limitations, a diverse range of large animal models and spontaneous tumor studies in veterinary patients have emerged to complement existing rodent models. These models and veterinary patients are excellent at providing realistic avenues for developing and testing histotripsy devices and techniques designed for future use in human patients. Here, we provide a review of animal models used in preclinical histotripsy studies and compare histotripsy ablation in these models using a series of original case reports across a broad spectrum of preclinical animal models and spontaneous tumors in veterinary patients.

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.

Histotripsy Ablation of Bone Tumors: Feasibility Study in Excised Canine Osteosarcoma Tumors

Osteosarcoma (OS) is a primary bone tumor affecting both dogs and humans. Histotripsy is a non-thermal, non-invasive focused ultrasound method using controlled acoustic cavitation to mechanically disintegrate tissue. In this study, we investigated the feasibility of treating primary OS tumors with histotripsy using a 500-kHz transducer on excised canine OS samples harvested after surgery at the Veterinary Teaching Hospital at Virginia Tech. Samples were embedded in gelatin tissue phantoms and treated with the 500-kHz histotripsy system using one- or two-cycle pulses at a pulse repetition frequency of 250 Hz and a dosage of 4000 pulses/point. Separate experiments also assessed histotripsy effects on normal canine bone and nerve using the same pulsing parameters. After treatment, histopathological evaluation of the samples was completed. To determine the feasibility of treating OS through intact skin/soft tissue, additional histotripsy experiments assessed OS with overlying tissues. Generation of bubble clouds was achieved at the focus in all tumor samples at peak negative pressures of 26.2 ± 4.5 MPa. Histopathology revealed effective cell ablation in treated areas for OS tumors, with no evidence of cell death or tissue damage in normal tissues. Treatment through tissue/skin resulted in generation of well-confined bubble clouds and ablation zones inside OS tumors. Results illustrate the feasibility of treating OS tumors with histotripsy.

Development of an exosomal gene signature to detect residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning

Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal messenger RNAs (mRNAs). The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by real-time quantitative reverse transcription PCR (qRT-PCR), while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups ("healthy", "osteosarcoma", "other bone tumor", or "non-neoplastic disease"). Pre-treatment samples from osteosarcoma cases were used as the training set, and a validation set from post-treatment samples was used for testing, classifying as "osteosarcoma detected" or "osteosarcoma-NOT detected". Dogs in a validation set whose post-treatment samples were classified as "osteosarcoma-NOT detected" had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof of concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.

Use of Stingless Bee Propolis and Geopropolis against Cancer-A Literature Review of Preclinical Studies

Cancer is one of the major maladies affecting humankind and remains one of the leading causes of death worldwide. The investigation of the biological activities of stingless bee products, especially propolis and geopropolis, has revealed promising therapeutic properties, especially in the research on new antineoplastic agents. This literature review of preclinical trials, involving biological assays of antitumor activity and identification of the chemical composition of propolis and geopropolis of stingless bee species, describes the cytotoxicity in tumor lineages (breast, lung, ovarian, liver, mouth, pharynx, larynx, colon, stomach, colorectal, cervix, kidney, prostate, melanoma, human glioblastoma, canine osteosarcoma, erythroleukemia, human chronic myelocytic leukemia, and human promyelocytic leukemia) of propolis and geopropolis of 33 species of stingless bees. The chemical composition of propolis and geopropolis was identified, indicating that these belong to the chemical classes of phenolic acids, flavonoids, coumarins, benzophenones, anthraquinones, alkaloids, terpenes, steroids, saponins, fatty acids, and carbohydrates and are possibly responsible for the cytotoxicity in tumor cells. Apoptosis was one of the main mechanisms of cytotoxicity of extracts and substances isolated from stingless bee products. Although the results found are encouraging, other preclinical studies and clinical trials are essential for the discovery of new anticancer agents.

Evaluation of the Chemotherapy Drug Response Using Organotypic Cultures of Osteosarcoma Tumours from Mice Models and Canine Patients

Simple Summary

Osteosarcoma is a bone cancer with 75% of cases occurring in people younger than 25 years old. 35–45% of patients demonstrate resistance to chemotherapeutics and critically, survival rates for osteosarcoma is only 10–30% for patients with metastases. Therefore, reliable and patient-specific drug testing modalities are needed. Organotypic slice culture consists of sections of tumours, which survive and preserve the tumours mechanical and cellular properties, thereby enabling personalised testing of drugs. This study aimed to characterise organotypic slice cultures of osteosarcoma bone tumours derived from mice and dogs and to use these models for testing of anti-tumoural drugs. This study reports the various cell constituents of the model and the maintenance of osteosarcoma organotypic cultures over several weeks. A significantly decreased sensitivity to chemotherapy in 3D organotypic culture relative to 2D monolayer was found, highlighting the need to test anti-cancer drugs in a more personalized and biomimetic manner.

Abstract

Improvements in the clinical outcome of osteosarcoma have plateaued in recent decades with poor translation between preclinical testing and clinical efficacy. Organotypic cultures retain key features of patient tumours, such as a myriad of cell types organized within an extracellular matrix, thereby presenting a more realistic and personalised screening of chemotherapeutic agents ex vivo. To test this concept for the first time in osteosarcoma, murine and canine osteosarcoma organotypic models were maintained for up to 21 days and in-depth analysis identified proportions of immune and stromal cells present at levels comparable to that reported in vivo in the literature. Cytotoxicity testing of a range of chemotherapeutic drugs (mafosfamide, cisplatin, methotrexate, etoposide, and doxorubicin) on murine organotypic culture ex vivo found limited response to treatment, with immune and stromal cells demonstrating enhanced survival over the global tumour cell population. Furthermore, significantly decreased sensitivity to a range of chemotherapeutics in 3D organotypic culture relative to 2D monolayer was observed, with subsequent investigation confirming reduced sensitivity in 3D than in 2D, even at equivalent levels of drug uptake. Finally, as proof of concept for the application of this model to personalised drug screening, chemotherapy testing with doxorubicin was performed on biopsies obtained from canine osteosarcoma patients. Together, this study highlights the importance of recapitulating the 3D tumour multicellular microenvironment to better predict drug response and provides evidence for the utility and possibilities of organotypic culture for enhanced preclinical selection and evaluation of chemotherapeutics targeting osteosarcoma.

Assessing a Novel 3D Assay System for Drug Screening against OS Metastasis

Osteosarcoma (OS) is an aggressive mesenchymal cell tumor that carries a poor long-term prognosis. Despite definitive surgery for the primary tumor and adjuvant chemotherapy, pulmonary metastasis is common and is the primary cause of morbidity. To improve outcomes for patients, we have developed and optimized a phenotypic screen for drugs that may target OS disseminated tumor cells (DTCs) and inhibit their metastatic outbreak rather than merely screening for cytotoxic activity against proliferating cells, as is commonly conducted in conventional drug discovery approaches. We report on the validation of a previously described 3D reconstituted basement membrane extract (3D BME) model system for tumor dormancy and metastatic outgrowth adapted to clonal pairs of high and low metastatic OS cells. A post-hoc validation of the assay was possible by comparing the activity of a drug in our assay with early evidence of activity in human OS clinical trials (regorafenib and saracatinib). In this validation, we found concordance between our assay and human clinical trial experience We then explored an approved veterinary small molecule inhibitor of Janus kinase-1 (oclacitinib) as a potential drug candidate to take advantage of the high prevalence of OS in pet dogs and its translational value to humans. Despite the biological rationale, we found no evidence to support the use of oclacitinib as an antimetastatic agent in OS. The findings support our 3D BME assay as a highly efficient method to examine drugs for activity in targeting OS DTCs.