Expression and Prognostic Significance of PD-L۱ in Common Canine Cancers: A Retrospective Analysis

Background: Programmed death ligand-۱ (PD-L۱) is an immune checkpoint molecule that facilitates tumor immune evasion. Its expression is increasingly recognized in canine cancers, but the prevalence and prognostic implications across tumor types remain unclear. Methods: This narrative review followed PRISMA guidelines for literature synthesis. Peer-reviewed studies published between ۲۰۱۶ and ۲۰۲۵ were retrieved from PubMed, CAB Abstracts, and Web of Science. Eligible studies quantitatively assessed PD-L۱ expression in common canine tumors using validated immunohistochemistry or RNA-based assays and reported prognostic outcomes. Results: PD-L۱ expression was detected in ۳–۱۰۰% of cases, varying by tumor type and assay. High PD-L۱ levels correlated with aggressive clinicopathologic features and reduced survival in diffuse large B-cell lymphoma, mammary carcinoma, and high-grade mast cell tumors. In contrast, nearly universal expression in oral melanoma limited prognostic discrimination. Methodological heterogeneity, including antibody clone variability, scoring systems, and cut-off thresholds, hindered cross-study comparison. Conclusion: PD-L۱ is commonly expressed and frequently portends an adverse prognosis in canine malignancies. Standardization of assay methodology and prospective multicenter validation are critical for establishing PD-L۱ as a robust prognostic and therapeutic biomarker in veterinary oncology.

کلیدواژه ها:

Canine cancer ، PD-L۱ ، Immunohistochemistry ، Prognosis ، Tumor microenvironment