Doxorubicin and zoledronate treatment in a dog with hemophagocytic histiocytic sarcoma.

A 6-year-old castrated male greyhound dog was referred for hemophagocytic histiocytic sarcoma (HHS) diagnosed following splenectomy. Severe thrombocytopenia, mild hypoalbuminemia, mild hypocholesterolemia, and mild hyperbilirubinemia were present. Abdominal ultrasound findings were concerning for hepatic metastasis. Doxorubicin and zoledronate combination therapy was initiated. The dog improved clinically and its thrombocytopenia, hypoalbuminemia, and hyperbilirubinemia resolved. The dog appeared well for 147 d before tumor progression was noted. The dog was treated with lomustine as a final measure, with no response. The dog survived for 6 mo with chemotherapy. To the authors' knowledge, this is the first report of clinical benefit of chemotherapy for HHS. Key clinical message: Doxorubicin should be considered for treating canine HHS since this variant of the disease is historically refractory to lomustine. Further research regarding efficacy of doxorubicin and zoledronate should be pursued.

Traitement à la doxorubicine et au zolédronate chez un chien atteint de sarcome histiocytaire hémophagocytaire. Un lévrier mâle castré de 6 ans a été vu pour un sarcome histiocytaire hémophagocytaire (HHS) diagnostiqué à la suite d'une splénectomie. Une thrombopénie sévère, une hypoalbuminémie légère, une hypocholestérolémie légère et une hyperbilirubinémie légère étaient présentes. Les résultats de l'échographie abdominale étaient préoccupants quant aux métastases hépatiques. Un traitement associant doxorubicine et zolédronate a été instauré. Le chien s'est amélioré cliniquement et sa thrombocytopénie, son hypoalbuminémie et son hyperbilirubinémie ont disparu. Le chien semblait en bonne santé pendant 147 jours avant de constater une progression tumorale. Le chien a été traité avec de la lomustine comme mesure finale, sans réponse. Le chien a survécu 6 mois grâce à la chimiothérapie. À la connaissance des auteurs, il s'agit du premier rapport faisant état d'un bénéfice clinique de la chimiothérapie pour le HHS.Message clinique clé :La doxorubicine doit être envisagée pour traiter le HHS canin puisque cette variante de la maladie est historiquement réfractaire à la lomustine. Des recherches plus approfondies concernant l'efficacité de la doxorubicine et du zolédronate devraient être poursuivies.(Traduit par Dr Serge Messier).

The Effect of Arginase on Canine T-Lymphocyte Functions and its Modulation by All-Trans Retinoid Acid (ATRA) in Canine Monocyte-Derived Macrophages.

Immunosuppressive myeloid cells in the tumor microenvironment play a major role in suppressing tumor immunity via the production of arginase, IL-10, and others. The objectives of this study were to determine the ability of all-trans retinoic acid (ATRA) to decrease the expression of arginase and other soluble mediators by canine monocyte-derived macrophages (MDMs) and to determine the inhibitory activity of arginase on canine T-lymphocytes. The immunomodulatory ability of ATRA (2 µM) on canine MDMs was evaluated via reverse transcription quantitative PCR (RT-qPCR), flow cytometry, arginase activity assay, and enzyme-linked immunoassay (ELISA). Arginase effects on T-lymphocyte phenotype and proliferation were then evaluated by flow cytometry. ATRA consistently decreased MDM expression of IL6, TGFB1, NOS2, ARG1, and CIITA transcripts, by approximately 2-4-fold, although this did not reach statistical significance for ARG1 or CIITA. Furthermore, arginase activity was decreased in ATRA-treated MDMs while the MDM phenotype remained unchanged. Arginase decreased the expression of granzyme B on CD8+ T-lymphocytes and inhibited CD4+ and CD8+ T-lymphocyte proliferation. These findings suggested that ATRA could inhibit canine MDM production of soluble inflammatory/immunosuppressive mediators. These data also revealed that arginase decreased canine T-lymphocyte proliferation and granzyme B expression. Further studies are needed to determine whether ATRA could reverse the immunosuppressive effects of myeloid cells on canine T-lymphocytes in vivo.

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

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

Canine memory T-cell subsets in health and disease.

A more complete understanding of canine T-lymphocyte immunity is necessary for improving diagnostic and therapeutic approaches to canine diseases, developing cell-based canine immunotherapeutics, and evaluating dogs as large mammal models for comparative immunology research. The aim of this study was to utilize CD45RA (indicating antigen inexperience) and CD62L (indicating lymph node homing capability), to quantify canine memory T-cell subsets in healthy dogs and dogs with various diseases. Peripheral blood mononuclear cells (PBMCs) were prospectively collected from dogs belonging to one of four groups:dermatologic inflammation (n = 9), solid tumors (n = 9), lymphoma (n = 9), and age-/weight-matched healthy control dogs (n = 15). Dogs receiving prednisone or any other immunomodulating medication within two weeks were excluded. Flow cytometry was performed and T-cell subsets were defined as CD4+ or CD8+, and naïve (TN), central memory (CM), effector memory (EM), or terminal effector memory re-expressing CD45RA (TEMRA). T-cell subset proportions were compared between each disease group and their healthy age-/weight-matched controls using a Mann-Whitney test. Significantly increased %CD8+ TN (P = 0.036) and decreased %CD8+ TEMRA (P = 0.045) were detected in dogs with dermatologic inflammation compared to healthy controls. Furthermore, %CD4+ TN positively correlated with Canine Atopic Dermatitis Extent and Severity Index (CADESI) score within the inflammation group (ρ = 0.817, P = 0.011). No significant differences between either cancer group and their healthy controls were detected. Taken together, these data indicate that dermatologic inflammation can alter proportions of peripheral blood T-cell subsets, possibly due to the migration of antigen-specific T-cells into tissues. Furthermore, these findings support the utility of CD45RA and CD62L in characterizing clinical canine immune responses.