Evaluation of circulating PD-1 and PD-L1 as diagnostic biomarkers in dogs with tumors

Immunohistochemical Expression of Programmed Death-Ligand 1 and Cytotoxic T-Lymphocyte Antigen-4 in Canine Cutaneous Mast Cell Tumours

Mast cell tumours (MCTs) are the most frequent cutaneous neoplasia of the dog, and they have very variable biological behaviour and survival times. Surgery is still the best treatment, and despite the several adjuvant therapies described, many cases are very aggressive and resistant to these treatments making it urgent to find new therapeutic targets. Nowadays, immunotherapy targeting immune checkpoints has been described as a complementary treatment for several human cancers, but it is still very scarcely studied in veterinary medicine. Therefore, this study aimed to investigate the expression of the checkpoint proteins programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) to evaluate their potential as therapeutic targets for MCT. Through immunohistochemical study, it was analysed the expression of PD-L1 and CTLA-4 in 74 MCT cases from the archive of the Veterinary Pathology Laboratory of the University of Porto (LabPatVet). Tumour size, histological grade, ki-67 proliferation index, mitotic count and presence of metastatic disease were also assessed. Most of the cases expressed both immune checkpoints in neoplastic cells. There was a statistically significant inverse association between the expression of CTLA-4 and MCT grade (p < 0,001) and mitotic count (p < 0.001). PD-L1 was significantly and negatively related to HG (p = 0.004), and tumour size (р = 0.014). Tumour size, histological grade and mitotic count were positively associated with metastatic disease. Additionally, it was observed that the expression of PD-L1 and CTLA-4 was interrelated (p < 0.001). This study demonstrated that MCT cells express both PD-L1 and CTLA-4 and that their expression was associated with MCT prognostic factors.

CAUSES OF MORBIDITY AND MORTALITY IN STELLER SEA LIONS (EUMETOPIAS JUBATUS) UNDER PROFESSIONAL CARE IN NORTH AMERICAN AQUARIUMS FROM 1979 TO 2021

To date, published comprehensive pathology investigations documented in Steller sea lions (SSL; Eumetopias jubatus) are from free-ranging populations, whereas health data from those under professional care in aquariums are currently lacking. A retrospective review of gross and histopathologic reports of SSL under human care in North American aquariums from 1979 to 2021 (n = 20) was performed. Associations between age, sex, or birth origin (born in aquariums versus the wild) with cause of death (COD) and comorbidities were explored. Age was significantly associated with development of endocrine organ pathology (P = 0.011). A relationship between age and both cardiovascular and ocular disease was suggested by the data, but did not reach significance (P = 0.058). Ocular disease was significantly associated with being born in aquariums (P = 0.022). The most common COD was neoplasia (n = 10), which was significantly associated with aged animals (P = 0.038). Less frequent COD included sepsis (confirmed, n = 2; suspected, n = 3), cardiomyopathy (n = 1), clostridial enteritis (n = 1), Sarcocystis spp. (n = 1), complication secondary to sedation (n = 1), and unknown (n = 1). This is the first report documenting the high prevalence of neoplasia in SSL, with tumors found incidentally in three individuals, frequent metastasis (10/13, 77%), and many cases of multiple primary malignancies (6/13, 46%). These data expand upon the current understanding of disease in SSL, highlight this species' predisposition to neoplasia with increasing longevity, and underscore the need for heightened screening in aged animals, which may ultimately serve to elevate the care of SSL under professional care in aquariums.

Exploring the dynamics of Programmed Death-Ligand 1 in canine lymphoma: unraveling mRNA amount, surface membrane expression and plasmatic levels

Introduction

Programmed Death-Ligand 1 is a well-known immune checkpoint molecule. Recent studies evaluated its expression in different canine cancer types through different laboratory techniques. The present study aims to evaluate the surface membrane protein expression (mPD-L1) by means of flow cytometry (FC) in different canine lymphoma immunophenotypes. Furthermore, in a subset of cases, mRNA and plasmatic soluble protein (sPD-L1) have been assessed in the same patient, and correlations among results from the three analyses investigated.

Methods

Samples obtained for diagnostic purpose from untreated dogs with a confirmed lymphoma immunophenotype were included: surface protein was assessed via FC and quantified with median fluorescence index ratio (MFI ratio), gene expression was evaluated by real time quantitative polymerase chain reaction (RT-qPCR) and plasmatic concentration of soluble protein (sPD-L1) measured with ELISA. Statistical analyses were performed to investigate any difference among FC immunophenotypes, updated Kiel cytological classes, and in the presence of blood infiltration.

Results

Considering FC, most B-cell lymphomas (BCL) were positive, with higher MFI ratios than other subtypes (81%, median MFI ratio among positive samples = 1.50, IQR 1.21-2.03, range 1.01-3.47). Aggressive T-cell lymphomas had a lower percentage of positive samples (56%) and showed low expression (median MFI ratio in positive samples = 1.14, IQR 1.07-1.32, range 1.02-2.19), while T-zone lymphomas (TZL) were frequently positive (80%) but with low expression (median MFI ratio in positive samples = 1.19, IQR 1.03-1.46, range 1.02-6.03). Cellular transcript and sPD-L1 were detected in all samples, without differences among immunophenotypes. No correlation between results from different techniques was detected, but sPD-L1 resulted significantly increased in FC-negative lymphomas (p = 0.023).

Discussion

PD-L1 molecule is involved in canine lymphoma pathogenesis, with differences among immunophenotypes detected by FC. Specifically, BCL have the highest expression and aggressive T-cell lymphomas the lowest, whereas TZL need further investigations.

PDL1 immunohistochemistry in canine neoplasms: Validation of commercial antibodies, standardization of evaluation, and scoring systems

Immuno-oncology research has brought to light the paradoxical role of immune cells in the induction and elimination of cancer. Programmed cell death protein 1 (PD1), expressed by tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PDL1), expressed by tumor cells, are immune checkpoint proteins that regulate the antitumor adaptive immune response. This study aimed to validate commercially available PDL1 antibodies in canine tissue and then, applying standardized methods and scoring systems used in human pathology, evaluate PDL1 immunopositivity in different types of canine tumors. To demonstrate cross-reactivity, a monoclonal antibody (22C3) and polyclonal antibody (cod. A1645) were tested by western blot. Cross-reactivity in canine tissue cell extracts was observed for both antibodies; however, the polyclonal antibody (cod. A1645) demonstrated higher signal specificity. Canine tumor histotypes were selected based on the human counterparts known to express PDL1. Immunohistochemistry was performed on 168 tumors with the polyclonal anti-PDL1 antibody. Only membranous labeling was considered positive. PDL1 labeling was detected both in neoplastic and infiltrating immune cells. The following tumors were immunopositive: melanomas (17 of 17; 100%), renal cell carcinomas (4 of 17; 24%), squamous cell carcinomas (3 of 17; 18%), lymphomas (2 of 14; 14%), urothelial carcinomas (2 of 18; 11%), pulmonary carcinomas (2 of 20; 10%), and mammary carcinomas (1 of 31; 3%). Gastric (0 of 10; 0%) and intestinal carcinomas (0 of 24; 0%) were negative. The findings of this study suggest that PDL1 is expressed in some canine tumors, with high prevalence in melanomas.

The Novel Diagnostic Techniques and Biomarkers of Canine Mammary Tumors

Canine mammary tumors (CMTs) are considered a serious clinical problem in older bitches. Due to the high malignancy rate and poor prognosis, an early diagnosis is essential. This article is a summary of novel diagnostic techniques as well as the main biomarkers of CMTs. So far, CMTs are detected only when changes in mammary glands are clinically visible and surgical removal of the mass is the only recommended treatment. Proper diagnostics of CMT is especially important as they represent a very diverse group of tumors and therefore different treatment approaches may be required. Recently, new diagnostic options appeared, like a new cytological grading system of CMTs or B-mode ultrasound, the Doppler technique, contrast-enhanced ultrasound, and real-time elastography, which may be useful in pre-surgical evaluation. However, in order to detect malignancies before macroscopic changes are visible, evaluation of serum and tissue biomarkers should be considered. Among them, we distinguish markers of the cell cycle, proliferation, apoptosis, metastatic potential and prognosis, hormone receptors, inflammatory and more recent: metabolomic, gene expression, miRNA, and transcriptome sequencing markers. The use of a couple of the above-mentioned markers together seems to be the most useful for the early diagnosis of neoplastic diseases as well as to evaluate response to treatment, presence of tumor progression, or further prognosis. Molecular aspects of tumors seem to be crucial for proper understanding of tumorigenesis and the application of individual treatment options.

The Implication of Serum Autoantibodies in Prognosis of Canine Mammary Tumors

Canine mammary tumor (CMT) is the most prevalent neoplasm in female dogs. Tumor recurrence and metastasis occur in malignant CMT (MMT) dogs after surgery. Identification of serum prognostic biomarkers holds the potential to facilitate prediction of disease outcomes. We have identified CMT-associated autoantibodies against thymidylate synthetase (TYMS), insulin-like growth factor-binding protein 5 (IGFBP5), hyaluronan and proteoglycan link protein 1 (HAPLN1), and anterior gradient 2 (AGR2), i.e., TYMS-AAb, IGFBP5-AAb, HAPLN1-AAb, and AGR2-AAb, respectively, by conducting serological enzyme-linked immunosorbent assays (ELISA). Herein we assessed serum AAb levels in 11 MMT dogs before and after surgery, demonstrating that IGFBP5-AAb and HAPLN1-AAb significantly decrease at 3- and 12-months post-surgery (p < 0.05). We evaluated the correlation between the presurgical AAb level and overall survival (OS) of 90 CMT dogs after surgery. Kaplan-Meier survival analysis reveals that IGFBP5-AAbHIgh and TYMS-AAbHigh are significantly correlated with worse OS (p = 0.017 and p = 0.029, respectively), while AGR2-AAbLow is correlated with somewhat poorer OS (p = 0.086). Areas under a time-dependent receiver operating characteristic curve (AUC) of IGFBP5-AAb and TYMS-AAb in predicting OS of MMT dogs are 0.611 and 0.616, respectively. Notably, MMT dogs presenting TYMS-AAbHigh/IGFBP5-AAbHigh/AGR2-AAbLow have worst OS (p = 0.0004). This study reveals an association between the serum AAb level and CMT prognosis.