Increased frequency of CD45 negative T cells (T zone cells) in older Golden retriever dogs

Factors correlating with circulating T-zone-like cells of undetermined significance (TZUS) in dogs resident in Italy

T-zone-like cells of undetermined significance (TZUS) share the same phenotypic pattern (CD45-CD5+) with T-zone lymphoma cells and were first described a few years ago in the peripheral blood (PB) of healthy aged American Golden retrievers (GR). History of bladder and eye disease increased the odd of circulating TZUS in the American GR population. Since differences among dogs may exist according to the geographical region of origin, herein we screened 489 PB samples to assess potential factors predisposing to the presence of circulating TZUS in dogs living in Italy. Overall, TZUS were found in 174 (35.6%) samples. Among 83 clinical variables, significant associations emerged with sex, age, diagnosis of neoplasia, history of neoplasia, history of infectious or parasitic disease, history of osteoarticular disease, presence of traumatic lesions or foreign bodies, and lymphocytes count. Only age and history of neoplasia retained significance at multivariate analysis (p=0.019 and p=0.036, respectively). Thus, older age and history of neoplasia are the main factors associated with circulating TZUS in Italian dogs. Future studies should focus on elucidating the biological role of TZUS and determining reproducible criteria for their identification, distinguishing them from infiltrating TZL.

Canine T zone lymphoma is a tumor of mature, previously activated αβ T cells

T cell lymphomas are a diverse group of tumors found in both dogs and humans, originating from various normal T cell types. Identifying the origin of neoplastic lymphocytes can offer valuable insights into the pathogenesis and clinical behavior of these tumors. T zone lymphoma (TZL) in dogs is characterized by the absence of CD45 expression, a strong breed predilection, and its association with adult-onset demodicosis-a condition believed to be linked to immunosuppression. In this study, our aim was to employ transcriptomic and functional data to determine the normal counterpart of TZL. Identifying the normal counterpart may help us understand both how these tumors arise and explain their clinical behavior. Gene expression profiling using NanoString and RNA seq was used to compare the transcriptome between neoplastic T zone cells, normal canine T cells and publicly available gene sets using Gene Set Enrichment Analysis. Mitogen, anti-CD3 stimulation and PMA/ionomycin stimulation were used to assess T cell proliferation in vitro, and intracellular cytokine production was measured by flow cytometry. Gene expression profiling revealed that TZL is most likely derived from an activated or memory alpha-beta T cell but the cells do not fall cleanly into an effector subtype. TZL cells express CD4-specific transcription factors GATA3 and THPOK, even though TZL cells more commonly express CD8, or neither CD4 nor CD8. TZL cells produce high levels of interferon gamma and tumor necrosis factor alpha when stimulated, further supporting the hypothesis that they are derived from an antigen experienced T cell. TZL cells do not proliferate when stimulated through the T cell receptor but will divide when the T cell receptor is bypassed with PMA and ionomycin. The observation that these cells are derived from a mature, previously activated T cell is the first step in understanding the genesis of this unique T cell tumor.

A bitesize introduction to canine hematologic malignancies

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

Genome-wide association analysis of canine T zone lymphoma identifies link to hypothyroidism and a shared association with mast-cell tumors

Background

T zone lymphoma (TZL), a histologic variant of peripheral T cell lymphoma, represents about 12% of all canine lymphomas. Golden Retrievers appear predisposed, representing over 40% of TZL cases. Prior research found that asymptomatic aged Golden Retrievers frequently have populations of T zone-like cells (phenotypically identical to TZL) of undetermined significance (TZUS), potentially representing a pre-clinical state. These findings suggest a genetic risk factor for this disease and caused us to investigate potential genes of interest using a genome-wide association study of privately-owned U.S. Golden Retrievers.

Results

Dogs were categorized as TZL (n = 95), TZUS (n = 142), or control (n = 101) using flow cytometry and genotyped using the Illumina CanineHD BeadChip. Using a mixed linear model adjusting for population stratification, we found association with genome-wide significance in regions on chromosomes 8 and 14. The chromosome 14 peak included four SNPs (Odds Ratio = 1.18–1.19, p = .3 × 10^− 5–5.1 × 10^− 5) near three hyaluronidase genes (SPAM1, HYAL4, and HYALP1). Targeted resequencing of this region using a custom sequence capture array identified missense mutations in all three genes; the variant in SPAM1 was predicted to be damaging. These mutations were also associated with risk for mast cell tumors among Golden Retrievers in an unrelated study. The chromosome 8 peak contained 7 SNPs (Odds Ratio = 1.24–1.42, p = 2.7 × 10^− 7–7.5 × 10^− 5) near genes involved in thyroid hormone regulation (DIO2 and TSHR). A prior study from our laboratory found hypothyroidism is inversely associated with TZL risk. No coding mutations were found with targeted resequencing but identified variants may play a regulatory role for all or some of the genes.

Conclusions

The pathogenesis of canine TZL may be related to hyaluronan breakdown and subsequent production of pro-inflammatory and pro-oncogenic byproducts. The association on chromosome 8 may indicate thyroid hormone is involved in TZL development, consistent with findings from a previous study evaluating epidemiologic risk factors for TZL. Future work is needed to elucidate these mechanisms.

Composite lymphoma of concurrent T zone lymphoma and large cell B cell lymphoma in a dog

Background

Evolution of indolent to aggressive lymphoma has been described in dogs but is difficult to distinguish from the de novo development of a second, clonally distinct lymphoma. Differentiation of these scenarios can be aided by next generation sequencing (NGS)-based assessment of clonality of lymphocyte antigen receptor genes.

Case presentation

An 8-year-old male intact Mastiff presented with generalized lymphadenomegaly was diagnosed with nodal T zone lymphoma (TZL) based on cytology, histopathology, immunohistochemistry and flow cytometry. Thirteen months later, the dog re-presented with progressive lymphadenomegaly, and based on cytology and flow cytometry, a large B cell lymphoma (LBCL) was diagnosed. Sequencing-based clonality testing confirmed the de novo development of a LBCL and the persistence of a TZL.

Conclusions

The occurrence of two distinct lymphoid neoplasms should be considered if patient features and tumor cytomorphology or immunophenotype differ among sequential samples. Sequencing-based clonality testing may provide conclusive evidence of two concurrent and distinct clonal lymphocyte populations, termed most appropriately “composite lymphoma”.

Associations of environment, health history, T-zone lymphoma, and T-zone-like cells of undetermined significance: A case-control study of aged Golden Retrievers

BACKGROUND

T-zone lymphoma (TZL), an indolent disease in older dogs, comprises approximately 12% of lymphomas in dogs. TZL cells exhibit an activated phenotype, indicating the disease may be antigen-driven. Prior research found that asymptomatic aged Golden Retrievers (GLDRs) commonly have populations of T-zone-like cells (phenotypically identical to TZL) of undetermined significance (TZUS).

OBJECTIVE

To evaluate associations of inflammatory conditions, TZL and TZUS, using a case-control study of GLDRs.

ANIMALS

TZL cases (n = 140), flow cytometrically diagnosed, were identified through Colorado State University's Clinical Immunology Laboratory. Non-TZL dogs, recruited through either a database of owners interested in research participation or the submitting clinics of TZL cases, were subsequently flow cytometrically classified as TZUS (n = 221) or control (n = 147).

METHODS

Health history, signalment, environmental, and lifestyle factors were obtained from owner-completed questionnaires. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using multivariable logistic regression, obtaining separate estimates for TZL and TZUS (versus controls).

RESULTS

Hypothyroidism (OR, 0.3; 95% CI, 0.1-0.7), omega-3 supplementation (OR, 0.3; 95% CI, 0.1-0.6), and mange (OR, 5.5; 95% CI, 1.4-21.1) were significantly associated with TZL. Gastrointestinal disease (OR, 2.4; 95% CI, 0.98-5.8) had nonsignificantly increased TZL odds. Two shared associations for TZL and TZUS were identified: bladder infection or calculi (TZL OR, 3.5; 95% CI, 0.96-12.7; TZUS OR, 5.1; 95% CI, 1.9-13.7) and eye disease (TZL OR, 2.3; 95% CI, 0.97-5.2; TZUS OR, 1.9; 95% CI, 0.99-3.8).

CONCLUSIONS AND CLINICAL IMPORTANCE

These findings may elucidate pathways involved in TZUS risk and progression from TZUS to TZL. Further investigation into the protective association of omega-3 supplements is warranted.

A case of canine high-grade T-cell lymphoma immunophenotypically consistent with T-zone lymphoma

A 9-year-old spayed female Curly Coated Retriever was referred for evaluation of generalized peripheral lymphadenomegaly. The dog was clinically healthy on presentation with no anomalies detected on complete blood count, serum biochemistry, urinalysis, or three-view thoracic radiographs. Fine-needle aspiration (FNA) and cytology of the peripheral lymph nodes were consistent with lymphoma with an intermediate-sized lymphoid population. Flow cytometry of peripheral lymph nodes was consistent with a homogeneous population of CD4⁺ T cells that had lost expression of the pan-leukocyte antigen CD45. Variable expression of CD21, CD25, and class II major histocompatibility complex (MHC) were also noted. This was considered consistent with T-zone lymphoma (TZL), although the T cells were noted to be larger than usual based on flow cytometry. Due to the suspected indolent nature of this patient's disease and clinical progression, a careful monitoring approach was initially discussed with the owner. However, additional diagnostic testing was performed to confirm the diagnosis. Bone marrow cytology did not show any significant anomalies. The largest lymph node (left mandibular) was extirpated and submitted for histopathology. Based on the lymph node architecture, cellular features, and high mitotic activity, an unexpected diagnosis of peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) was made. The dog was started on CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy. This case illustrates the limitations of using flow cytometry as the sole means of diagnosing TZL and highlights the importance of using complementary tests when subtyping canine lymphoma, which is significant when considering a patient's treatment plan and prognosis.

Metastatic thymoma in the liver of a dog

A 12-y-old neutered male Portuguese Water dog was presented because of a 1-y history of persistent hyporexia, diarrhea, and recurrent pyelonephritis. Abdominal ultrasound revealed hepatic nodules and diffuse splenomegaly, and radiographs revealed a mediastinal mass. Fine-needle aspirates of the liver, spleen, and mediastinal mass were suspicious for lymphoma. Flow cytometry identified small T cells that co-expressed CD4 and CD8 at all sites, most suspicious for thymoma, but lymphoma could not be ruled out. PCR for antigen receptor rearrangements analysis identified polyclonal amplification of the T-cell receptor genes, more consistent with thymoma than lymphoma. Histopathology of the liver and thymic mass confirmed thymoma with hepatic metastasis.