Evaluation of expression of death programmed cell ligand (PD-L1) and cytotoxic and regulatory t-cell infiltrate as prognostic factors in mammary tumor of canine female

Author(s)

Ingrid Kester Lima Silva

• Document type: Master's Dissertation
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT)
• Defense date: 2023-11-13

Examining board members

Ricardo de Francisco Strefezzi; Silvia Regina Kleeb; Geórgia Modé Magalhães

• Advisor: Ricardo de Francisco Strefezzi

Abstract

Cancer has been reported as the main cause of death in dogs and, in bitches, mammary tumours are the most common. Therefore, studies to elucidate tumour pathogenesis and aiming to improve the treatment and prevention of cancer are needed. Programmed cell death protein 1 (PD-1) is an immune checkpoint molecule expressed on the surface of T cell membrane. When it binds to programmed cell death ligand 1 (PD-L1), negative signals are propagated to T cells, initiating a suppressive mechanism of utmost importance for controlling the immune response. This mechanism can also be used by tumour cells, which can express the PD-L1 protein on their surfaces and use it as a mechanism to evade the immune response. The expression of PD-L1 in veterinary medicine has already been analysed in several animal species, however, there is little information about its prognostic value in dogs with mammary neoplasms. The objective of the present study was to characterize the expression of PD-L1 and the cytotoxic and regulatory T cell infiltrates in canine mammary tumours and to verify their prognostic values when compared to post-surgical survival. Eighty-seven samples were analysed histologically and by immunohistochemistry. The majority of the tumours were positive for PD-L1 and dogs with negative tumours for this protein had shorter post-surgical survival. The evaluation of cytotoxic and regulatory T cell infiltrates in mammary tumours, carried out on a small number of samples, did not show prognostic value. Our results suggest that lower PD-L1 expression is an indicator of shorter post-surgical survival in dogs with mammary carcinomas and the positivity for this ligand may be an indicator of a better prognosis. (AU)

• FAPESP's process: 20/14891-8 - Evaluation of the expression of the programmed death cellular ligand (pd-l1) and the cytotoxic and regulatory t cell infiltrates as prognostic factors in canine mammary tumors
• Grantee: Ingrid Kester Lima Silva
• Support Opportunities: Scholarships in Brazil - Master