IL-1ß+ macrophages fuel pathogenic inflammation in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with high resistance to therapies1. Inflammatory and immunomodulatory signals co-exist in the pancreatic tumour microenvironment, leading to dysregulated repair and cytotoxic responses. Tumour-associated macrophages (TAMs) have key roles in PDAC2, but their diversity has prevented therapeutic exploitation. Here we combined single-cell and spatial genomics with functional experiments to unravel macrophage functions in pancreatic cancer. We uncovered an inflammatory loop between tumour cells and interleukin-1ß (IL-1ß)-expressing TAMs, a subset of macrophages elicited by a local synergy between prostaglandin E2 (PGE2) and tumour necrosis factor (TNF). Physical proximity with IL-1ß+ TAMs was associated with inflammatory reprogramming and acquisition of pathogenic properties by a subset of PDAC cells. This occurrence was an early event in pancreatic tumorigenesis and led to persistent transcriptional changes associated with disease progression and poor outcomes for patients. Blocking PGE2 or IL-1ß activity elicited TAM reprogramming and antagonized tumour cell-intrinsic and -extrinsic inflammation, leading to PDAC control in vivo. Targeting the PGE2-IL-1ß axis may enable preventive or therapeutic strategies for reprogramming of immune dynamics in pancreatic cancer.

Cellular and transcriptional dynamics of human neutrophils at steady state and upon stress.

Traditionally viewed as poorly plastic, neutrophils are now recognized as functionally diverse; however, the extent and determinants of neutrophil heterogeneity in humans remain unclear. We performed a comprehensive immunophenotypic and transcriptome analysis, at a bulk and single-cell level, of neutrophils from healthy donors and patients undergoing stress myelopoiesis upon exposure to growth factors, transplantation of hematopoietic stem cells (HSC-T), development of pancreatic cancer and viral infection. We uncover an extreme diversity of human neutrophils in vivo, reflecting the rates of cell mobilization, differentiation and exposure to environmental signals. Integrated control of developmental and inducible transcriptional programs linked flexible granulopoietic outputs with elicitation of stimulus-specific functional responses. In this context, we detected an acute interferon (IFN) response in the blood of patients receiving HSC-T that was mirrored by marked upregulation of IFN-stimulated genes in neutrophils but not in monocytes. Systematic characterization of human neutrophil plasticity may uncover clinically relevant biomarkers and support the development of diagnostic and therapeutic tools.

A PGE2-MEF2A axis enables context-dependent control of inflammatory gene expression.

Tight control of inflammatory gene expression by antagonistic environmental cues is key to ensure immune protection while preventing tissue damage. Prostaglandin E2 (PGE2) modulates macrophage activation during homeostasis and disease, but the underlying mechanisms remain incompletely characterized. Here we dissected the genomic properties of lipopolysaccharide (LPS)-induced genes whose expression is antagonized by PGE2. The latter molecule targeted a set of inflammatory gene enhancers that, already in unstimulated macrophages, displayed poorly permissive chromatin organization and were marked by the transcription factor myocyte enhancer factor 2A (MEF2A). Deletion of MEF2A phenocopied PGE2 treatment and abolished type I interferon (IFN I) induction upon exposure to innate immune stimuli. Mechanistically, PGE2 interfered with LPS-mediated activation of ERK5, a known transcriptional partner of MEF2. This study highlights principles of plasticity and adaptation in cells exposed to a complex environment and uncovers a transcriptional circuit for IFN I induction with relevance for infectious diseases or cancer.