PD-1, PD-L1, and PD-L2 Gene Expression and Tumor Infiltrating Lymphocytes in Canine Melanoma

Abstract

Melanoma in humans and dogs is considered highly immunogenic; however, the function of tumor-infiltrating lymphocytes (TILs) is often suppressed in the tumor microenvironment. In humans, current immunotherapies target checkpoint molecules (such as PD-L1, expressed by tumor cells), inhibiting their suppressive effect over TILs. The role of PD-L2, an alternative PD-1 ligand also overexpressed in malignant tumors and in patients with anti-PD-L1 resistance, remains poorly understood. In the current study, we evaluated the expression of checkpoint molecule mRNAs in canine melanoma and TILs. Analysis of checkpoint molecule gene expression was performed by RT-qPCR (real-time quantitative polymerase chain reaction) using total RNA isolated from formalin-fixed and paraffin-embedded melanomas ( n = 22) and melanocytomas ( n = 9) from the Virginia Tech Animal Laboratory Services archives. Analysis of checkpoint molecule expression revealed significantly higher levels of PDCD1 ( PD-1) and CD274 ( PD-L1) mRNAs and an upward trend in PDCD1LG2 ( PD-L2) mRNA in melanomas relative to melanocytomas. Immunohistochemistry revealed markedly increased numbers of CD3+ T cells in the highest PD-1-expressing subgroup of melanomas compared to the lowest PD-1 expressors, whereas densities of IBA1+ cells (macrophages) were similar in both groups. CD79a+ cell numbers were low for both groups. As in human melanoma, overexpression of the PD-1/PD-L1/PD-L2 axis is a common feature of canine melanoma. High expression of PD-1 and PD-L1 correlates with increased numbers of CD3+ cells. Additionally, the high level of IBA1+ cells in melanomas with low PD-1 expression and low CD3+ cells levels suggest that the expression of checkpoint molecules is modulated by interactions between T cells and cancer cells rather than histiocytes.

Efficacy, Safety, and Impact on Patient Survival of PDL1/PD-1 Inhibitors versus FOLFIRINOX Regimens for Advanced Pancreatic Cancer

“…In the comparison group, the most common hematological index was neutropenia much lower than the original regimen, which lies in the active monitoring of patients' hematological indexes before and after chemotherapy and timely whitening treatment, including carrying diethylstilbestrol tablets at discharge to maintain granulocyte levels not only to prevent the risk of infection and other risks but also to prevent patients from delaying chemotherapy due to low granulocyte levels [ 22 ]. No thrombocytopenia was observed, while anemia was slightly higher than in the original regimen [ 23 ]. Nonhematological indicators lie in the prophylactic use of antiemetic drugs during chemotherapy, including azathioprine and gastrofacial, and the absence of diarrhea and peripheral neuropathy, possibly associated with lower doses of oxaliplatin and irinotecan [ 24 – 27 ].…”

A Comparative View on Molecular Alterations and Potential Therapeutic Strategies for Canine Oral Melanoma

“…This wealth of information now paves the way for the development of targeted therapies with improved clinical response and fewer side effects. Potential antimetastasis therapeutics are already in development in human medicine [146], and canine patients may solve the problems surrounding the translational gap by providing a relevant spontaneous disease model [120]. To this end, collaborative work between the science, medical, and veterinary communities will surely strengthen our collective success.…”

“…On one hand, CD4+ T helper cells can enhance the function of antigen presenting cells (APCs) and stimulate recruitment of cytotoxic CD8+ lymphocytes (CTLs) to eliminate tumour cells. Yet, on the other hand, regulatory CD4+/CD25+/FOXP3+ Treg cells promote immune tolerance by suppressing the function and cytokine release from other lymphocytes, and CD20+ B cells may have detrimental effects by influencing an M2 macrophage phenotype and promoting differentiation of Tregs [108,[119][120][121]. Thus, while human and canine melanomas are considered to be highly immunogenic tumours, there is a balancing act between the different subtypes of TILs and various mechanisms by which the tumour microenvironment becomes immunosuppressive.…”

“…This is a physiological mechanism of peripheral tolerance, and a regulatory feedback loop following T cell activation [16]. Ninety to 100% of COMs express PD-L1 [126][127][128], possibly in response to IFNγ [126] and modulated by interaction with CD3+ T cells [120], with membrane expression maintained by CMTM6 (CKLF-like MARVEL transmembrane domain protein 6) [129]. Tumour cell expression of PD-L1 is a negative prognostic indicator in human oncology, with similar findings established for PD-L1 expression in canine malignant mammary gland tumours [130].…”

Companion Animal Model in Translational Oncology; Feline Oral Squamous Cell Carcinoma and Canine Oral Melanoma

“…Numerous studies in pets have assessed the relationship between cancer and the immune system; increased numbers of immunosuppressive regulatory T-cells (T-reg) have been found in various cancer types in dogs [ 28 , 29 , 30 ]. Markers of potential response to immunotherapy such as programmed cell death 1 (PD-1) and its ligand, programmed cell death ligand 1 (PD-L1), have also been found to be overexpressed in cancer cells and cancer infiltrating lymphocytes in oral melanoma, lymphoma, osteosarcoma, and urothelial carcinoma in dogs [ 31 , 32 , 33 , 34 , 35 ]. The first cancer immunotherapy vaccine has been successfully used in dogs with locally controlled oral melanoma and is now conditionally licensed in the USA [ 36 , 37 ].…”