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Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with few available therapeutic options. Two transcriptional cancer cell states have been consistently reported in PDAC, with the basal-like/squamous phenotype displaying a more aggressive biological behavior. Genetic and epigenetic dysregulation of the axon guidance pathway are common in PDAC, yet our understanding of its biological relevance is limited. Here, we investigated the functional role of the axon guidance cue SEMA3A in sustaining the progression of PDAC. We integrated available transcriptomic datasets of human PDAC within situhybridization analyses of patients’ tissues to find that SEMA3A is expressed by stromal cells and selectively enriched in epithelial cells of the basal-like/squamous subtype. We found that both cell-intrinsic and cell extrinsic factors instructing the basal-like/squamous subtype induce expression of SEMA3A in PDAC cells.In vitro, SEMA3A promoted cell migration as well as anoikis resistance. At molecular level, these phenotypes were associated with increased FAK signaling and enrichment of gene programs related to cytoskeleton remodeling. Accordingly, SEMA3A provided mouse PDAC cells with greater metastatic competence. In mouse orthotopic allografts, SEMA3A remodeled the TME by favoring infiltration of tumor-associated macrophages and exclusion of T cells. Mechanistically, SEMA3A functioned as chemoattractant for macrophages and favored their polarization towards an M2-like phenotype. In SEMA3Ahightumors, depletion of macrophages resulted in greater intratumor infiltration by CD8+ T cells and increased sensitivity of these tumors to chemotherapy. Overall, we show that SEMA3A contributes to the malignant phenotype of basal-like PDAC.

Since the beginning of the SARS-CoV-2 pandemic, COVID-19 appeared as a unique disease with unconventional tissue and systemic immune features. Here we show a COVID-19 immune signature associated with severity by integrating single-cell RNA-seq analysis from blood samples and broncho-alveolar lavage fluids with clinical, immunological and functional ex vivo data. This signature is characterized by lung accumulation of naïve lymphoid cells associated with a systemic expansion and activation of myeloid cells. Myeloid-driven immune suppression is a hallmark of COVID-19 evolution, highlighting arginase-1 expression with immune regulatory features of monocytes. Monocyte-dependent and neutrophil-dependent immune suppression loss is associated with fatal clinical outcome in severe patients. Additionally, our analysis shows a lung CXCR6+ effector memory T cell subset is associated with better prognosis in patients with severe COVID-19. In summary, COVID-19-induced myeloid dysregulation and lymphoid impairment establish a condition of ‘immune silence’ in patients with critical COVID-19., Integrated studies of matched tissue sites and cell types in COVID-19 patients are important to define the immune mechanisms of pathology. Here, the authors describe an immune signature in fatal COVID-19 patients harmonizing single-cell RNA sequencing of blood and matched BAL cells with deep clinical, immunological and functional data.

BackgroundPathogenesis of Coronavirus disease 2019 (Covid-19) is poorly understood. Most histologic studies come from post-mortem analysis, with existing data indicating that histologic features of acute respiratory distress syndrome are typically present in fatal cases. However, this observation may be misleading, due to confounding factors in pre-terminal disease, including injury resulting from prolonged mechanical ventilation. Ante-mortem lung biopsy may provide major pathogenetic insights, potentially providing a basis for novel treatment approaches.AimThis comparative, multicenter, prospective, observational study was planned to identify ante-mortem histological profile and immunohistochemical features of lung tissue in patients with Covid-19 in early and late phases of the disease, including markers of inflammatory cells and major pathways involved in the cytokine storm triggering.MethodsEnrolled patients underwent lung biopsy, according to the study protocol approved by local Ethical Committee, either within 15 days of the first symptoms appearing (early phase) or after >15 days (more advanced disease). Key exclusion criteria were excessive or uncorrectable bleeding risk and cardiovascular disease with heart failure. Lung samples were obtained by conventional transbronchial biopsy, trans-bronchial lung cryobiopsy or surgical lung biopsy.Results23 patients were enrolled: 12 patients underwent lung biopsy within 15 days and 11 patients more than 15 days after the onset of symptoms. Early biopsies were characterized by spots of patchy acute lung injury (ALI) with alveolar type II cells hyperplasia and significant vascular abnormalities (disordered angiogenesis with alveolar capillary hyperplasia, luminal enlargement and thickened walls of pulmonary venules, perivascular CD4-T-cell infiltration), with no hyaline membranes. In the later stages, the alveolar architecture appeared disrupted, with areas of organizing ALI, venular congestion and capillary thromboembolic microangiopathy. Striking phenotypic features were demonstrated in hyperplastic pneumocytes and endothelial cells, including the expression of phospho-STAT3 and molecules involved in immunoinhibitory signals (PD-L1 and IDO-1). Alveolar macrophages exhibited macrophage-related markers (CD68, CD11c, CD14) together with unusual markers, such as DC-Lamp/CD208, CD206, CD123/IL3AR.ConclusionA morphologically distinct “Covid pattern” was identified in the earlier stages of the disease, with prominent epithelial and endothelial cell abnormalities, that may be potentially reversible, differing strikingly from findings in classical diffuse alveolar damage. These observations may have major therapeutic implications, justifying studies of early interventions aimed at mitigating inflammatory organ injury.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing pandemic coronavirus disease 2019 (COVID-19). The majority of patients with COVID-19 have a good prognosis, but variable percentages in different countries develop pneumonia associated with lymphocytopenia and severe inflammatory response due to uncontrolled release of cytokines. These immune mediators are transcriptionally regulated by JAK-STAT molecular pathways, which can be disabled by small molecules. Here, we provide evidences on the efficacy of baricitinib, a JAK1/JAK2 inhibitor, in correcting the immune abnormalities observed in patients hospitalized with COVID-19. Indeed, we demonstrate a significant reduction in serum levels of interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)α, a rapid recovery in circulating T and B cell frequencies and an increased antibody production against SARS-CoV-2 spike protein in baricitinib-treated patients. Moreover, treated patients underwent a rapid reduction in oxygen flow need and progressive increase in the P/F. Our work provides the basis on developing effective treatments against COVID-19 pathogenesis using on-target therapy.

The RAF/MEK/ERK (MAP Kinase) pathway is the index oncogenic signaling towards which many compounds have been developed and tested for the treatment of KRAS-driven cancers, including pancreatic ductal adenocarcinoma (PDA). Here, we explored the immunological changes induced by targeted MEK1/2 inhibition (MEKi) using trametinib in preclinical mouse models of PDA. We evaluated the dynamic changes in the immune contexture of mouse PDA upon MEKi using a multidimensional approach (mRNA analyses, flow cytometry, and immunophenotyping). Effect of MEKi on the viability and metabolism of macrophages was investigated in vitro. We showed that transcriptional signatures of MAP Kinase activation are enriched in aggressive human PDA subtype (squamous/basal-like/quasimesenchymal), while short term MEKi treatment in mouse PDA induced subtype switching. Integrative mRNA expression and immunophenotypic analyses showed that MEKi reshapes the immune landscape of PDA by depleting rather than reprogramming macrophages, while augmenting infiltration by neutrophils. Depletion of macrophages is observed early in the course of in vivo treatment and is at least partially due to their higher sensitivity to MEKi. Tumor-associated macrophages were consistently reported to interfere with gemcitabine uptake by PDA cells. Here, our in vivo studies show a superior antitumor activity upon combination of MEKi and gemcitabine using a sequential rather than simultaneous dosing protocol. Our results show that MEK inhibition induces a dramatic remodeling of the tumor microenvironment of mouse PDA through depletion of macrophages, which substantially improves the antitumor activity of gemcitabine.