Inhibiting P2Y12 in Macrophages Induces Endoplasmic Reticulum Stress and Promotes an Anti-Tumoral Phenotype

Abstract

The P2Y12 receptor is an adenosine diphosphate responsive G protein-coupled receptor expressed on the surface of platelets and is the pharmacologic target of several anti-thrombotic agents. In this study, we use liver samples from mice with cirrhosis and hepatocellular carcinoma to show that P2Y12 is expressed by macrophages in the liver. Using in vitro methods, we show that inhibition of P2Y12 with ticagrelor enhances tumor cell phagocytosis by macrophages and induces an anti-tumoral phenotype. Treatment with ticagrelor also increases the expression of several actors of the endoplasmic reticulum (ER) stress pathways, suggesting activation of the unfolded protein response (UPR). Inhibiting the UPR with tauroursodeoxycholic acid (Tudca) diminishes the pro-phagocytotic effect of ticagrelor, thereby indicating that P2Y12 mediates macrophage function through activation of ER stress pathways. This could be relevant in the pathogenesis of chronic liver disease and cancer, as macrophages are considered key players in these inflammation-driven pathologies.

Exploring the Role of Endoplasmic Reticulum Stress in Hepatocellular Carcinoma through mining of the Human Protein Atlas

“…Furthermore, we reported that the expression of IRE1α signaling pathway components was upregulated in fibrotic HCC patient tissue compared to non-fibrous HCC tissue, while this increased expression significantly correlated with poor survival in patients with liver cancer [5]. Moreover, we recently reported that ER-stress occurrence in macrophages was correlated with an anti-tumoral macrophage phenotype and the increased macrophage clearance of HCC cells [62]. These findings emphasized the contribution of ER-stress and UPR activation in stromal tissue to HCC progression, as well as the therapeutic potential of targeting stromal cells undergoing ER-stress in liver cancer.…”

Extracellular ATP Mediates Cancer Cell Migration and Invasion Through Increased Expression of Cyclooxygenase 2

“…The two splice variants of P2X7 receptors also show differential modulation in response to chemotherapy as seen in acute myeloid leukemia ( Pegoraro et al, 2020 ). It has to also be noted that the physiological role of P2 receptors depends on the cell type they are expressed on—inhibiting P2Y12 receptors with ticagrelor in pancreatic ductal adenocarcinoma cells decreases their proliferative capacity through the Akt pathway ( Elaskalani et al, 2020 ), inhibition of the same receptors on macrophages enhances their tumor cell phagocytic properties involving ER stress pathway ( Pavlovic et al, 2020 ) and inhibits the formation of inflammasome ( Huang et al, 2020 ), whose role in cancer progression continues to be sought ( Hamarsheh and Zeiser, 2020 ). Therefore, targeting specific P2 receptors remains a challenge making therapeutic approach personalized depending on the nucleotide composition of the microenvironment and/or receptor expression.…”

“…In addition to a non-regulated release of ATP from dying/damaged cells, active release of ATP also occurs through exocytic granules, microvesicles and various transporters and channels located on the tumor cells ( Vultaggio-Poma et al, 2020 ). The role such huge amounts of extracellular ATP (eATP) may play in the tumor microenvironment has been debated with both pro- and anti-tumourogenic outcomes ( Jiang et al, 2015 ; Avanzato et al, 2016 ; Pavlovic et al, 2020 ). This outcome largely depends on the type of receptor eATP acts on, of which there are ion-channel associated P2X receptors, G protein-coupled P2Y receptors, and adenosine-specific adenosine receptors ( Fiebich et al, 2014 ).…”

Control of Macrophage Inflammation by P2Y Purinergic Receptors

“…P2Y 12 receptor mRNA and protein expression has been detected in human monocytes and macrophages as well as in the human monocytic cell line THP1 [ 107 , 108 ]. In animal models, the P2Y 12 receptor is expressed by hepatic macrophages, both from healthy, cirrhotic and cancerous liver [ 109 ]. P2Y 12 receptor mRNA could be detected on human macrophages generated from monocytes with M-CSF/dexamethasone/IL-4 (MDI).…”

“…In macrophage polarization ( Figure 1 ), P2Y 12 receptor expression is increased in alternatively activated M2 macrophages [ 114 ]. Pharmacological inhibition of P2Y 12 receptor was found to evoke an endoplasmic reticulum (ER) stress response that appears to block M2 markers such as arginase-1, indicative of a shift towards M1 [ 109 ]. Similar to the P2Y 2 receptor on macrophages, which senses ATP and UTP released from apoptotic cells [ 55 ], the P2Y 12 receptor has been reported to direct migration of TAM towards ADP-releasing melanoma cells in necrotic tumor areas [ 110 ].…”