B-cell responses are emerging as critical regulators of cancer progression. In this study, we investigated the role of B lymphocytes in the microenvironment of human pancreatic ductal adenocarcinoma (PDAC), in a retrospective consecutive series of 104 PDAC patients and in PDAC preclinical models. Immunohistochemical analysis revealed that B cells occupy two histologically distinct compartments in human PDAC, either scatteringly infiltrating (CD20-TILs), or organized in tertiary lymphoid tissue (CD20-TLT). Only when retained within TLT, high density of B cells predicted longer survival (median survival 16.9 mo CD20-TLT vs. 10.7 mo CD20-TLT; = 0.0085). Presence of B cells within TLT associated to a germinal center (GC) immune signature, correlated with CD8-TIL infiltration, and empowered their favorable prognostic value. Immunotherapeutic vaccination of spontaneously developing PDAC (Kras-Pdx1-Cre) mice with α-enolase (ENO1) induced formation of TLT with active GCs and correlated with increased recruitment of T lymphocytes, suggesting induction of TLT as a strategy to favor mobilization of immune cells in PDAC. In contrast, in an implanted tumor model devoid of TLT, depletion of B cells with an anti-CD20 antibody reinstated an antitumor immune response. Our results highlight B cells as an essential element of the microenvironment of PDAC and identify their spatial organization as a key regulator of their antitumor function. A mindfully evaluation of B cells in human PDAC could represent a powerful prognostic tool to identify patients with distinct clinical behaviors and responses to immunotherapeutic strategies.

Interleukin-1 receptor 8 (IL-1R8, also known as single immunoglobulin IL-1R-related receptor, SIGIRR, or TIR8) is a member of the IL-1 receptor (ILR) family with distinct structural and functional characteristics, acting as a negative regulator of ILR and Toll-like receptor (TLR) downstream signaling pathways and inflammation1. NK cells are innate lymphoid cells which mediate resistance against pathogens and contribute to the activation and orientation of adaptive immune responses2–4. NK cells mediate resistance against hematopoietic neoplasms but are generally considered to play a minor role in solid tumor carcinogenesis5–7. Here we report that IL-1R8 serves as a checkpoint for NK cell maturation and effector function. Its genetic blockade unleashes NK-cell mediated resistance to hepatic carcinogenesis, hematogenous liver and lung metastasis and cytomegalovirus infection.

Innate immunity includes a cellular and a humoral arm. PTX3 is a fluid-phase pattern recognition molecule conserved in evolution which acts as a key component of humoral innate immunity in infections of fungal, bacterial, and viral origin. PTX3 binds conserved microbial structures and self-components under conditions of inflammation and activates effector functions (complement, phagocytosis). Moreover, it has a complex regulatory role in inflammation, such as ischemia/reperfusion injury and cancer-related inflammation, as well as in extracellular matrix organization and remodeling, with profound implications in physiology and pathology. Finally, PTX3 acts as an extrinsic oncosuppressor gene by taming tumor-promoting inflammation in murine and selected human tumors. Thus evidence suggests that PTX3 is a key homeostatic component at the crossroad of innate immunity, inflammation, tissue repair, and cancer. Dissecting the complexity of PTX3 pathophysiology and human genetics paves the way to diagnostic and therapeutic exploitation.

Summary Neutrophils are a component of the tumor microenvironment and have been predominantly associated with cancer progression. Using a genetic approach complemented by adoptive transfer, we found that neutrophils are essential for resistance against primary 3-methylcholantrene-induced carcinogenesis. Neutrophils were essential for the activation of an interferon-γ-dependent pathway of immune resistance, associated with polarization of a subset of CD4 − CD8 − unconventional αβ T cells (UTC αβ ). Bulk and single-cell RNA sequencing (scRNA-seq) analyses unveiled the innate-like features and diversity of UTC αβ associated with neutrophil-dependent anti-sarcoma immunity. In selected human tumors, including undifferentiated pleomorphic sarcoma, CSF3R expression, a neutrophil signature and neutrophil infiltration were associated with a type 1 immune response and better clinical outcome. Thus, neutrophils driving UTC αβ polarization and type 1 immunity are essential for resistance against murine sarcomas and selected human tumors.

Pentraxins are a superfamily of fluid phase pattern recognition molecules conserved in evolution and characterized by a cyclic multimeric structure. C-reactive protein (CRP) and serum amyloid P component (SAP) constitute the short pentraxin arm of the superfamily. CRP and SAP are produced in the liver in response to IL-6 and are acute phase reactants in humans and mice respectively. In addition SAP has been shown to affect tissue remodelling and fibrosis by stabilizing all types of amyloid fibrils and by regulating monocyte to fibrocyte differentiation. Pentraxin 3 (PTX3) is the prototype of the long pentraxin arm. Gene targeted mice and genetic and epigenetic studies in humans suggest that PTX3 plays essential non-redundant roles in innate immunity and inflammation as well as in tissue remodelling. Recent studies have revealed the role of PTX3 as extrinsic oncosuppressor, able to tune cancer-related inflammation. In addition, at acidic pH PTX3 can interact with provisional matrix components promoting inflammatory matrix remodelling. Thus acidification during tissue repair sets PTX3 in a tissue remodelling and repair mode, suggesting that matrix and microbial recognition are common, ancestral features of the humoral arm of innate immunity.

The innate immune system comprises a cellular and a humoral arm. Humoral pattern recognition molecules include complement components, collectins, ficolins, and pentraxins. These molecules are involved in innate immune responses by recognizing microbial moieties and damaged tissues, activating complement, exerting opsonic activity and facilitating phagocytosis, and regulating inflammation. The long pentraxin PTX3 is a prototypic humoral pattern recognition molecule that, in addition to providing defense against infectious agents, plays several functions in tissue repair and regulation of cancer-related inflammation. Characterization of the PTX3 molecular structure and biochemical properties, and insights into its interactome and multiple roles in tissue damage and remodeling support the view that microbial and matrix recognition are evolutionarily conserved functions of humoral innate immunity molecules.

Besides the nervous system, L1 is expressed in many human cancers, including ovarian and endometrial carcinoma, pancreatic ductal adenocarcinoma (PDAC), melanoma and glioblastoma. L1 expression confers motile and invasive properties to tumor cells, supporting cancer growth, metastasis, and chemoresistance and often acting as a marker of poor prognosis (8). L1 has also been detected in the hematopoietic system, in particular in immune cells of myelomonocytic and lymphoid origin (9), and we have previously reported L1-dependent transmigration of dendritic cells across the endothelium (10).An intriguing aspect of L1 biology is its expression in the vascular system: while no or very little L1 is detectable in the vasculature of most normal tissues, its level is markedly increased in the vasing the mechanisms of pathological angiogenesis and to identifying novel cancer vessel-specific markers.L1 (also known as L1CAM or CD171) is a transmembrane glycoprotein belonging to the immunoglobulin superfamily and is composed of an extracellular portion, containing 6 Ig-like domains and 5 fibronectin type III repeats, followed by a transmembrane region, and a highly conserved cytoplasmic tail (5). L1 was discovered and characterized as a cell-adhesion molecule in the nervous system (6), where it is involved in neurite outgrowth and fasciculation as well as cell adhesion and migration. In addition to homophilic binding, L1 can establish cis-or trans-interactions with different binding partners, such as integrins, CD24, neurocan, neuropilin-1, and other members of the neural cell adhesion family (7).

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