Checkpoint molecule expression by B and T cell lymphomas in dogs.

Area of Science:

• Immunology
• Veterinary Oncology
• Cancer Biology

Background:

• Immunotherapies targeting programmed cell death 1 (PD-1) are effective in human non-Hodgkin lymphoma.
• Limited information exists on PD-1 and its ligand PD-L1 expression in canine lymphoma.

Purpose of the Study:

• To analyze PD-1 and PD-L1 expression in canine lymphoma.
• To compare expression levels between lymphoma types and healthy controls.
• To assess the impact of chemotherapy resistance on PD-1 and PD-L1 expression in vitro.

Main Methods:

• Flow cytometry was used to analyze PD-1 and PD-L1 expression.
• Samples included fine-needle aspirates from dogs with B cell lymphoma (BCL), T cell lymphoma (TCL), relapsed lymphoma, and healthy controls.
• In vitro studies assessed chemotherapy-resistant cell lines.

Main Results:

• Malignant B cells showed increased PD-L1 expression compared to normal B cells.
• TCL tumor cells and normal T cells had low PD-1 and PD-L1 expression.
• Tumor-infiltrating lymphocytes in both BCL and TCL exhibited higher PD-1 and PD-L1 expression than lymphocytes from healthy dogs.
• In vitro, chemotherapy-resistant BCL and TCL cell lines displayed increased PD-1 and PD-L1 expression.

Conclusions:

• Canine lymphomas demonstrate upregulated expression of checkpoint molecules PD-1 and PD-L1.
• The precise role of this upregulation in canine lymphoma biology requires further investigation.