PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity
Menée in vitro et à l'aide de modèles murins, cette étude met en évidence une association entre le niveau d'expression de PD-1 sur les macrophages spécifiques de la tumeur et l'inhibition du processus de phagocytose et de l'immunité tumorale
Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that is upregulated on activated T cells for the induction of immune tolerance1, 2. Tumour cells frequently overexpress the ligand for PD-1, programmed cell death ligand 1 (PD-L1), facilitating their escape from the immune system3, 4. Monoclonal antibodies that block the interaction between PD-1 and PD-L1, by binding to either the ligand or receptor, have shown notable clinical efficacy in patients with a variety of cancers, including melanoma, colorectal cancer, non-small-cell lung cancer and Hodgkin’s lymphoma5, 6, 7, 8, 9. Although it is well established that PD-1–PD-L1 blockade activates T cells, little is known about the role that this pathway may have in tumour-associated macrophages (TAMs). Here we show that both mouse and human TAMs express PD-1. TAM PD-1 expression increases over time in mouse models of cancer and with increasing disease stage in primary human cancers. TAM PD-1 expression correlates negatively with phagocytic potency against tumour cells, and blockade of PD-1–PD-L1 in vivo increases macrophage phagocytosis, reduces tumour growth and lengthens the survival of mice in mouse models of cancer in a macrophage-dependent fashion. This suggests that PD-1–PD-L1 therapies may also function through a direct effect on macrophages, with substantial implications for the treatment of cancer with these agents.