Gating strategy for FACS analysis of HSCs and progenitors.

Gating strategy for FACS analysis of myeloid and lymphoid cell populations.

Enhanced emergency granulopoiesis in IL-1R2-deficient MN/MCA1-bearing mice.

Transcriptional profiling analysis of sarcoma-infiltrating neutrophils.

Interleukin 1 (IL1) plays dual functions in cancer. It promotes cancer-related inflammation and progression but also influences leukocyte functional activation. IL1 receptor 2 (IL1R2) functions as an IL1 decoy receptor, inhibiting IL1 activity. In this study, we investigated the contribution of IL1R2 in tuning IL1-dependent effects in mouse models of cancer, including colorectal cancer, lung cancer, and primary and metastatic transplantable and chemically induced sarcoma. Even though the prominent role of IL1 is protumoral, IL1R2 deficiency was selectively associated with reduced sarcoma growth, whereas it was irrelevant in other preclinical models investigated. IL1R2 deficiency was associated with a massive infiltration of neutrophils in the tumor, neutrophilia, and increased extramedullary emergency granulopoiesis. Neutrophils were crucial for tumor control in IL1R2-deficient mice. Immunophenotypic and transcriptional profiling of sarcoma-infiltrating neutrophils revealed that IL1R2 deficiency was associated with higher expression of activation or maturation markers and gene expression reprogramming, with downregulation of pathways associated with protumoral functions. In patients with sarcoma, the IL1R2 deficiency gene signature correlated with better clinical outcomes. Thus, this study shows that IL1R2 tunes IL1-driven cancer-associated emergency granulopoiesis and neutrophil functional activation to an antitumor mode in sarcomas and reveals the antitumor potential of neutrophils in this tumor.

Neutrophil phenotype in MN/MCA1-bearing mice.

Chemokines and their receptors play a pivotal role in the initiation and regulation of inflammation through the orchestration of leukocyte extravasation and directed migration toward sites of tissue injury. Tight control of chemokine gradients within tissues is essential to ensure that inflammatory responses remain transient and properly resolved. When this regulatory mechanism fails, dysregulated chemokine signaling can contribute to the development of chronic inflammation. Atypical receptors for chemoattractants comprise atypical chemokine receptors (ACKRs) and the chemerin-presenting receptor CCRL2. ACKRs perform specialized functions enabling the fine-tuning of chemokine gradients, primarily through the scavenging, sequestration, or redistribution of chemokines. By regulating their spatial and temporal availability, ACKRs play a key role in limiting excessive leukocyte recruitment and promoting inflammation resolution. The lungs are in a dynamic equilibrium between immune activation and homeostasis. Rapid and tightly regulated immune cell recruitment is essential for effective host defense while preventing tissue damage. In this context, ACKRs expressed by specialized lung endothelial cells are emerging as critical regulators of leukocyte trafficking and inflammatory resolution. Given the paucity of studies in this area, this review summarizes current knowledge of ACKRs and CCRL2 in lung immune surveillance and discusses their potential as therapeutic targets in lung diseases.

Granulocytosis in UPS patients and IL-1R2-deficiency signature in colorectal and lung cancer, and skin cutaneous melanoma.

IL-1R2 expression in healthy and sarcoma-bearing mice.

Tumor growth and leukocyte infiltration in IL-1R2-deficient tumor bearing mice.

Background ACKR2 is an atypical chemokine receptor that plays a significant role in regulating inflammation by binding to inflammatory CC chemokines and facilitating their degradation. Previous findings suggest that the genetic absence of ACKR2 leads to heightened tumor growth in inflammation-driven models. Conversely, mice lacking ACKR2 exhibit protection against lung metastasis in melanoma and breast cancer models. This study aims to explore the specific cell types expressing ACKR2 and their relative contributions to the protection against lung metastasis.Methods ACKR2 expression was studied by the generation of an inducible and conditional knockout (KO) mouse expressing two reporter genes, luciferase and TdTomato visible by In Vivo Imaging System, flow cytometry and immunofluorescence. Gene expression in lung endothelial cells (ECs) was investigated by RNA sequencing analysis. In vivo models of lung metastasis and inflammation were performed in wild-type (WT) and conditional KO mice by intravenous injection of melanoma and colon cancer cell lines; the induction of acute lung injury model was done by intranasal injection of lipopolysaccharide (LPS). Leukocytes infiltrating lung metastasis were studied by fluorescence-activated cell sorting (FACS) analysis. The serum chemokine levels were studied with a multiplex ELISA.Results The analysis of the reporter mouse revealed that ACKR2 is expressed by lymphatic endothelial cells (LECs) in most murine organs. However, uniquely in the lungs, ACKR2 expression is observed in blood endothelial cells (BECs), specifically in capillaries known as aerocytes specialized for regulating leukocyte trafficking. Selective deletion of Ackr2 from ECs (ACKR2ΔCdh5 mice) but not from LECs (ACKR2ΔProx1 mice) resulted in protection in models of melanoma and colorectal cancer lung metastasis. This protection was associated with an increased presence of activated T lymphocytes infiltrating the lungs compared with WT mice. Additionally, in a model of acute lung injury, mice with selective deletion from the endothelial compartment exhibited heightened extravasation of T lymphocytes compared with both ACKR2 KO and WT mice.Conclusions These results indicate that ACKR2 is selectively expressed by lung vascular capillaries (aerocytes) that are devoted to the regulation of leukocyte extravasation. Selective ACKR2 targeting in this compartment, by modulating chemokine availability, promotes T lymphocyte extravasation resulting in reduced lung metastases.