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The lung is a vital organ that incessantly faces external environmental challenges. Its homeostasis and unimpeded vital function are ensured by the respiratory epithelium working hand in hand with an intricate fine-tuned tissue-resident immune cell network. Lung tissue-resident immune cells span across the innate and adaptive immunity and protect from infectious agents but can also prove to be pathogenic if dysregulated. Here, we review the innate and adaptive immune cell subtypes comprising lung-resident immunity and discuss their ontogeny and role in distinct respiratory diseases. An improved understanding of the role of lung-resident immunity and how its function is dysregulated under pathological conditions can shed light on the pathogenesis of respiratory diseases.

Almost 2 years into the pandemic and with vaccination of children significantly lagging behind adults, long-term pediatric humoral immune responses to SARS-CoV-2 are understudied. The C19.CHILD Hamburg (COVID-19 Child Health Investigation of Latent Disease) Study is a prospective cohort study designed to identify and follow up children and their household contacts infected in the early 2020 first wave of SARS-CoV-2. We screened 6113 children P = 0.047). Most importantly, children showed sustained seroconversion up to 9 months PSO, and serum antibody concentrations persistently surpassed adult levels (ratio serum IgG spike children vs. adults 90 days PSO 1.75, P P = 0.01; 270 days 1.54, P = 0.001). In a low-incidence setting, SARS-CoV-2 infection and humoral immune response present distinct patterns in children including higher antibody levels, and lower seroprevalence in families with pediatric index cases. Children show long-term SARS-CoV-2 antibody responses. These findings are relevant to novel variants with increased disease burden in children, as well as for the planning of age-appropriate vaccination strategies.

SARS-CoV-2 is still a major burden for global health despite effective vaccines. With the reduction of social distancing measures, infection rates are increasing in children, while data on the pediatric immune response to SARS-CoV-2 infection is still lacking. Although the typical disease course in children has been mild, emerging variants may present new challenges in this age group.Peripheral blood mononuclear cells (PBMC) from 51 convalescent children, 24 seronegative siblings from early 2020, and 51 unexposed controls were stimulated with SARS-CoV-2-derived peptide MegaPools from the ancestral and beta variants. Flow cytometric determination of activation-induced markers and secreted cytokines were used to quantify the CD4+ T cell response.The average time after infection was over 80 days. CD4+ T cell responses were detected in 61% of convalescent children and were markedly reduced in preschool children. Cross-reactive T cells for the SARS-CoV-2 beta variant were identified in 45% of cases after infection with an ancestral SARS-CoV-2 variant. The CD4+ T cell response was accompanied most predominantly by IFN-γ and Granzyme B secretion.An antiviral CD4+ T cell response was present in children after ancestral SARS-CoV-2 infection, which was reduced in the youngest age group. We detected significant cross-reactivity of CD4+ T cell responses to the more recently evolved immune-escaping beta variant. Our findings have epidemiologic relevance for children regarding novel viral variants of concern and vaccination efforts.

Hepatocellular carcinoma (HCC) ranks among the five most common cancer entities worldwide and leads to hundred-thousands of deaths every year. Despite some groundbreaking therapeutical revelations during the last years, the overall prognosis remains poor. Although the immune system fights malignant transformations with a robust anti-tumor response, certain immune mediators have also been shown to promote cancer development. For example, interleukin (IL)-22 has been associated with HCC progression and worsened prognosis in multiple studies. However, the underlying mechanisms of the pathological role of IL-22-signaling as well as the role of its natural antagonist IL-22 binding protein (IL-22BP) in HCC remain elusive. Here, we corroborate the pathogenic role of IL-22 in HCC by taking advantage of two mouse models. Moreover, we observed a protective role of IL-22BP during liver carcinogenesis. While IL-22 was mainly produced by CD4+ T cells in HCC, IL-22BP was abundantly expressed by neutrophils during liver carcinogenesis. Hepatocytes could be identified as a major target of this pathological IL-22-signaling. Moreover, abrogation of IL-22 signaling in hepatocytes in IL22ra1flox/flox × AlbCre+ mice reduced STEAP4 expression-a known oncogene-in HCC in vivo. Likewise, STEAP4 expression correlated with IL22 levels in human HCC samples, but not in healthy liver specimens. In conclusion, these data encourage the development of therapeutical approaches that target the IL-22–IL-22BP axis in HCC.

Lung adenocarcinoma (LADC) is the leading cause of cancer death worldwide. Nevertheless, syngeneic mouse models of the disease are sparse, and cell lines suitable for transplantable and immunocompetent mouse models of LADC remain unmet needs. We established multiple mouse LADC cell lines by repeatedly exposing two mouse strains (FVB, Balb/c) to the tobacco carcinogens urethane or diethylnitrosamine and by culturing out the resulting lung tumours for prolonged periods of time. Characterization of the resulting cell lines (n = 7) showed that they were immortal and phenotypically stable in vitro, and oncogenic, metastatic and lethal in vivo. The primary tumours that gave rise to the cell lines, as well as secondary tumours generated by transplantation of the cell lines, displayed typical LADC features, such as glandular architecture and mucin and thyroid transcription factor 1 expression. Moreover, these cells exhibited marked molecular similarity with human smokers’ LADC, including carcinogen-specific Kras point mutations (KrasQ61R in urethane- and KrasQ61H in diethylnitrosamine-triggered cell lines) and Trp53 deletions and displayed stemness features. Interestingly, all cell lines overexpressed proliferin, a murine prolactin orthologue, which functioned as a lung tumour promoter. Furthermore, prolactin was overexpressed and portended poor prognosis in human LADC. In conclusion, we report the first LADC cell lines derived from mice exposed to tobacco carcinogens. These cells closely resemble human LADC and provide a valuable tool for the functional investigation of the pathobiology of the disease.

Machine learning techniques have provided a technological evolution in medicine and especially in the field of medical imaging. The aim of this study is to firstly compare multiple transfer learning architecture models such as MobilleNetVn (n = 1, 2), InceptionVn (n = 1, 2, 3, 4), InceptionResNet, VGG16 and NasNetMobile and provide a final performance estimation, using a variety of metrics, secondly, propose an efficient and accurate classifier for liver cancer trait detection and prediction, and thirdly, develop a mobile application which uses the proposed model to classify liver cancer traits into various categories in real-time. Magnetic Resonance Images (MRI) of mouse liver cancer of different origin were used as input datasets for our experiments. However, the required memory by the deployed Convolutional Neural Network (CNN) models on smart mobile devices or embedded systems for real time applications, is an issue to be addressed. Here, all the baseline pre-trained CNN models on the ImageNet dataset were trained on a dataset of MRI images of mice of different genetic background with genetically- or chemically- induced hepatocellular cancer. We present and compare all main metric values for each model such as accuracy, cross entropy, f-score, confusion matrix for various types of classification. Data analysis verifies that the proposed optimized architecture model for this task of liver cancer trait classification and prediction, the MV1-LCCP, shows a suitable performance in terms of memory utilization and accuracy, suitable to be deployed in the mobile Android application, which is also developed and presented in this paper.

Neonatal passive immunity, derived from transplacental transfer of IgG antibodies from mother to fetus during pregnancy, can mitigate the risk for severe infections in the early postnatal period. Understanding the placenta as the gateway organ in this process, we aimed to evaluate the influence of specific factors modulating the transplacental IgG transfer rate (TPTR) in 141 mother/neonate pairs. We further evaluated the potential health advantage elicited by maternal IgG with regard to respiratory tract infections during infancy and early childhood. Data and biological samples collected within the prospective longitudinal pregnancy cohort study PRINCE (Prenatal Identification of Children's Health) were used for these analyses. We tested IgG antibody levels against seven pathogens (measles, mumps, rubella, tetanus, diphtheria, pertussis and influenza A) by ELISA and detected seropositivity in 72.6-100% of pregnant women and in 76.3-100% of their neonates, respectively. Cord blood IgG levels reached 137-160% of levels detected in maternal blood. Strikingly, assessment of TPTR for all seven antigens highlighted that TPTR strongly depends on individual placental function. Subsequent in-depth analysis of anti-influenza A IgG revealed a link between cord blood levels and uterine perfusion, measured by uterine artery pulsatility index. Moreover, higher cord blood anti-influenza A IgG levels were associated with a significantly reduced risk for respiratory tract infections during the first six months of life, indicating a high degree of cross-reactivity and possible pathogen-agnostic effects of anti-influenza A antibodies. Taken together, our data suggest that early life immunity is modulated by maternal IgG levels and individual placental features such as perfusion. Vaccination of pregnant women, i.e. against influenza, can increase neonatal antibody levels and hereby protect against early life respiratory infections. Consequently, specific guidelines should evolve in order to safeguard neonates born from pregnancies with poorer placental capacity for vertical transfer of protective antibodies.

The clearance of apoptotic cells by Mφs favors malignant pleural effusion progression in a murine cancer model., Malignant pleural effusion (MPE) results from the capacity of several human cancers to metastasize to the pleural cavity. No effective treatments are currently available, reflecting our insufficient understanding of the basic mechanisms leading to MPE progression. Here, we found that efferocytosis through the receptor tyrosine kinases AXL and MERTK led to the production of interleukin-10 (IL-10) by four distinct pleural cavity macrophage (Mφ) subpopulations characterized by different metabolic states and cell chemotaxis properties. In turn, IL-10 acts on dendritic cells (DCs) inducing the production of tissue inhibitor of metalloproteinases 1 (TIMP1). Genetic ablation of Axl and Mertk in Mφs or IL-10 receptor in DCs or Timp1 substantially reduced MPE progression. Our results delineate an inflammatory cascade—from the clearance of apoptotic cells by Mφs, to production of IL-10, to induction of TIMP1 in DCs—that facilitates MPE progression. This inflammatory cascade offers a series of therapeutic targets for MPE.

Background Prenatal challenges such as maternal stress perception increase the risk and severity of asthma during childhood. However, insights into the trajectories and targets underlying the pathogenesis of prenatally triggered asthma are largely unknown. The developing lung and immune system may constitute such targets. Objective Here we have aimed to identify the differential sex-specific effects of prenatal challenges on lung function, immune response, and asthma severity in mice. Methods We generated bone marrow chimeric (BMC) mice harboring either prenatally stress-exposed lungs or a prenatally stress-exposed immune (hematopoietic) system and induced allergic asthma via ovalbumin. Next-generation sequencing (RNA sequencing) of lungs and assessment of airway epithelial barrier function in ovalbumin-sensitized control and prenatally stressed offspring was also performed. Results Profoundly enhanced airway hyperresponsiveness, inflammation, and fibrosis were exclusively present in female BMC mice with prenatally stress-exposed lungs. These effects were significantly perpetuated if both the lungs and the immune system had been exposed to prenatal stress. A prenatally stress-exposed immune system alone did not suffice to increase the severity of these asthma features. RNA sequencing analysis of lungs from prenatally stressed, non-BMC, ovalbumin-sensitized females unveiled a deregulated expression of genes involved in asthma pathogenesis, tissue remodeling, and tight junction formation. It was also possible to independently confirm a tight junction disruption. In line with this, we identified an altered perinatal and/or postnatal expression of genes involved in lung development along with an impaired alveolarization in female prenatally stressed mice. Conclusion Here we have shown that the fetal origin of asthma is orchestrated by a disrupted airway epithelium and further perpetuated by a predisposed immune system.

Lung cancer and chronic lung diseases impose major disease burdens worldwide and are caused by inhaled noxious agents including tobacco smoke. The cellular origins of environmental-induced lung tumors and of the dysfunctional airway and alveolar epithelial turnover observed with chronic lung diseases are unknown. To address this, we combined mouse models of genetic labeling and ablation of airway (club) and alveolar cells with exposure to environmental noxious and carcinogenic agents. Club cells are shown to survive KRAS mutations and to form lung tumors after tobacco carcinogen exposure. Increasing numbers of club cells are found in the alveoli with aging and after lung injury, but go undetected since they express alveolar proteins. Ablation of club cells prevents chemical lung tumors and causes alveolar destruction in adult mice. Hence club cells are important in alveolar maintenance and carcinogenesis and may be a therapeutic target against premalignancy and chronic lung disease., eLife digest The deadliest form of lung cancer is called lung adenocarcinoma, or LUAD. Tobacco chemicals often cause the disease by damaging the genetic information of lung cells. The damage leads to harmful changes in the DNA sequence which prompt the cells to form tumors. For instance, the most common of these changes takes place in a gene called KRAS. However, it is still unclear exactly which type of lung cells are more likely to develop into a tumor. In the lungs, airway epithelial cells cover the inside of the passages that bring the air inside little sacks called alveoli, which are lined by alveolar cells. Previous studies have used genetic methods to switch on the KRAS mutation in different compartments of the mouse lung. This showed that groups of airway cells, of alveolar cells, and of a class of cells located at the junction between airways and alveoli could all give rise to cancer. However, these experiments did not examine how tobacco chemicals could give rise to tumors in different groups of lung cells. Here, Spella et al. triggered LUAD in adult mice by exposing them to the toxic chemicals found in tobacco smoke, but without making any change to the KRAS gene. These mice also had genetically engineered reporters that could be used to deduce where the resulting tumors came from. DNA sequencing showed that the airway epithelial cells gained KRAS mutations after the chemical treatment. When the airway epithelial cells were experimentally removed before the treatments with tobacco chemicals, these mice did not get LUAD tumors. Spella et al. also observed that the tobacco-induced tumors came from the epithelial cells in the airways, and not from the cells in the alveoli. Moreover, when the lung was damaged, airway cells could move to the alveoli and start adopting the identity of alveolar cells, thereby replenishing this population. Together, these experiments imply that tobacco-induced LUAD starts in the airway epithelial cells. These findings suggest that airway epithelial cells could be targeted to stop lung cancer early on. Further studies should also examine how airway epithelial cells can transition to look more like alveolar cells when the lungs get harmed.

Background Carcinogen-inflicted human cancers, including lung tumours harbour thousands of mutations per genome, most of which are unknown (Garraway, LA et al, Cell 2013;153:17–37). Aim To develop a faithful mouse model of human tobacco carcinogen-induced lung adenocarcinoma suitable for the identification of novel oncogenic genes and pathways. Methods We repeatedly managed to obtain several murine lung adenocarcinoma cell lines (MLA) by chronically exposing various mouse strains to different tobacco carcinogens. MLA were characterised for cancer stemness and oncogenes, as well as global gene expression. Results To date, 12 MLA cell lines have been derived from Wt and transgenic mice on the FVB, Balb/c, and C57BL/6 strains by means of urethane or diethylnitrosamine exposure. All MLA were immortal, phenotypically stable, and indefinitely passaged in vitro over a period of over 18 months and/or 60 passages. In addition, all cell lines were oncogenic, transplantable, metastatic, and uniformly lethal in vivo. Interestingly, MLA displayed Kras mutations in codon 61, mono- or bi-allelic Trp53 loss, and expression of lung cancer stemness factors Itgb3 and Lgr6, in amazing similarity to human lung cancers. Microarray revealed that all MLA cell lines heavily overexpressed Prl2c2, encoding proliferin, in comparison to the native lungs. Prl2c2 silencing diminished MLA proliferation and stemness, to a degree comparable with Itgb3 interference. Conclusions MLA are faithful models of human lung adenocarcinoma that led to the discovery of Prl2c2 as a candidate lung tumour promoter. Funding European Research Council Starting Independent Investigator Grant #260524. Respire 2 European Respiratory Society Fellowship, European Respiratory Society Short Term Research Fellowship.

Antenatal stress increases the prevalence of diseases in later life, which shows a strong sex-specific effect. However, the underlying mechanisms remain unknown. Maternal glucocorticoids can be elevated by stress and are potential candidates to mediate the effects of stress on the offspring sex-specifically. A comprehensive evaluation of dynamic maternal and placental mechanisms modulating fetal glucocorticoid exposure upon maternal stress was long overdue. Here, we addressed this gap in knowledge by investigating sex-specific responses to midgestational stress in mice. We observed increased levels of maternal corticosterone, the main glucocorticoid in rodents, along with higher corticosteroid-binding globulin levels at midgestation in C57Bl/6 dams exposed to sound stress. This resulted in elevated corticosterone in female fetuses, whereas male offspring were unaffected. We identified that increased placental expression of the glucocorticoid-inactivating enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2; Hsd11b2 gene) and ATP-binding cassette transporters, which mediate glucocorticoid efflux toward maternal circulation, protect male offspring from maternal glucocorticoid surges. We generated mice with an Hsd11b2 placental-specific disruption ( Hsd11b2PKO) and observed moderately elevated corticosterone levels in offspring, along with increased body weight. Subsequently, we assessed downstream glucocorticoid receptors and observed a sex-specific differential modulation of placental Tsc22d3 expression, which encodes the glucocorticoid-induced leucine zipper protein in response to stress. Taken together, our observations highlight the existence of unique and well-orchestrated mechanisms that control glucocorticoid transfer, exposure, and metabolism in the mouse placenta, pinpointing toward the existence of sex-specific fetal glucocorticoid exposure windows during gestation in mice.

Increased expression of osteopontin (secreted phosphoprotein 1, SPP1) is associated with aggressive human lung adenocarcinoma (LADC), but its function remains unknown. Our aim was to determine the role of SPP1 in smoking-induced LADC. We combined mouse models of tobacco carcinogen-induced LADC, of deficiency of endogenous Spp1 alleles, and of adoptive pulmonary macrophage reconstitution to map the expression of SPP1 and its receptors and determine its impact during carcinogenesis. Co-expression of Spp1 and mutant KrasG12C in benign cells was employed to investigate SPP1/KRAS interactions in oncogenesis. Finally, intratracheal adenovirus encoding Cre recombinase was delivered to LSL.KRASG12D mice lacking endogenous or overexpressing transgenic Spp1 alleles. SPP1 was overexpressed in experimental and human LADC and portended poor survival. In response to two different smoke carcinogens, Spp1-deficient mice developed fewer and smaller LADC with decreased cellular survival and angiogenesis. Both lung epithelial- and macrophage-secreted SPP1 drove tumor-associated inflammation, while epithelial SPP1 promoted early tumorigenesis by fostering the survival of KRAS-mutated cells. Finally, loss and overexpression of Spp1 was, respectively, protective and deleterious for mice harboring KRASG12D-driven LADC. Our data support that SPP1 is functionally involved in early stages of airway epithelial carcinogenesis driven by smoking and mutant KRAS and may present an important therapeutic target.

Lung adenocarcinoma (LUAD) and chronic lung diseases caused by smoking and environmental noxious agents are the deadliest diseases worldwide, sharing a partially charted pathobiology of dysfunctional alveolar repair. Here we sought to identify the respiratory epithelial dynamics and molecular signatures participating in adult lung maintenance and chemical carcinogenesis. We employed novel mouse models of respiratory epithelial marking and ablation, a battery of pulmonary toxins and carcinogens, experimental protocols of carcinogen-induced LUAD, tobacco carcinogen-induced LUAD cell lines, and human transcriptomic data and identified a prominent involvement of airway molecular programs in alveolar maintenance and carcinogen-induced LUAD. The airway-specific transcriptomic signature was redistributed to the alveoli after toxic and carcinogenic insults and resulted in marked contributions of airway-labeled cells to injury-recovered alveoli and LUAD. Airway cells maintained Kras mutations and therefore possibly contributed to lung cancer initiation, while LUAD were spatially linked to neighboring airways. Transcriptomic profiling of carcinogen-induced murine and human LUAD revealed enrichment in airway signatures, while ablation of airway cells distorted alveolar structure and function and protected mice from LUAD development. Collectively, these results indicate that airway cells and/or transcriptomic signatures are essential for alveolar maintenance and LUAD development.

Background & Aims Unregulated activity of interleukin (IL) 22 promotes intestinal tumorigenesis in mice. IL22 binds the antagonist IL22 subunit alpha 2 (IL22RA2, also called IL22BP). We studied whether alterations in IL22BP contribute to colorectal carcinogenesis in humans and mice. Methods We obtained tumor and nontumor tissues from patients with colorectal cancer (CRC) and measured levels of cytokines by quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. We measured levels of Il22bp messenger RNA in colon tissues from wild-type, Tnf–/–, Lta–/–, and Ltb–/– mice. Mice were given azoxymethane and dextran sodium sulfate to induce colitis and associated cancer or intracecal injections of MC38 tumor cells. Some mice were given inhibitors of lymphotoxin beta receptor (LTBR). Intestine tissues were analyzed by single-cell sequencing to identify cell sources of lymphotoxin. We performed immunohistochemistry analysis of colon tissue microarrays from patients with CRC (1475 tissue cores, contained tumor and nontumor tissues) and correlated levels of IL22BP with patient survival times. Results Levels of IL22BP were decreased in human colorectal tumors, compared with nontumor tissues, and correlated with levels of lymphotoxin. LTBR signaling was required for expression of IL22BP in colon tissues of mice. Wild-type mice given LTBR inhibitors had an increased tumor burden in both models, but LTBR inhibitors did not increase tumor growth in Il22bp–/– mice. Lymphotoxin directly induced expression of IL22BP in cultured human monocyte–derived dendritic cells via activation of nuclear factor κB. Reduced levels of IL22BP in colorectal tumor tissues were associated with shorter survival times of patients with CRC. Conclusions Lymphotoxin signaling regulates expression of IL22BP in colon; levels of IL22BP are reduced in human colorectal tumors, associated with shorter survival times. LTBR signaling regulates expression of IL22BP in colon tumors in mice and cultured human dendritic cells. Patients with colorectal tumors that express low levels of IL22BP might benefit from treatment with an IL22 antagonist.

Malignant pleural effusion (MPE) is the lethal consequence of various human cancers metastatic to the pleural cavity. However, the mechanisms responsible for the development of MPE are still obscure. Here we show that mutant KRAS is important for MPE induction in mice. Pleural disseminated, mutant KRAS bearing tumour cells upregulate and systemically release chemokine ligand 2 (CCL2) into the bloodstream to mobilize myeloid cells from the host bone marrow to the pleural space via the spleen. These cells promote MPE formation, as indicated by splenectomy and splenocyte restoration experiments. In addition, KRAS mutations are frequently detected in human MPE and cell lines isolated thereof, but are often lost during automated analyses, as indicated by manual versus automated examination of Sanger sequencing traces. Finally, the novel KRAS inhibitor deltarasin and a monoclonal antibody directed against CCL2 are equally effective against an experimental mouse model of MPE, a result that holds promise for future efficient therapies against the human condition., Malignant pleural effusion (MPE) is a lethal condition associated with various cancers. Here, the authors show that cancer cells with KRAS mutations promote MPE by recruiting myeloid cells via CCL2 signalling and that pharmaceutical targeting of KRAS results in reduced MPE incidence and volume in mouse models.

The lungs are frequently affected by cancer metastasis. Although NRAS mutations have been associated with metastatic potential, their exact role in lung homing is incompletely understood. We cross‐examined the genotype of various tumor cells with their ability for automatic pulmonary dissemination, modulated NRAS expression using RNA interference and NRAS overexpression, identified NRAS signaling partners by microarray, and validated them using Cxcr1‐ and Cxcr2‐deficient mice. Mouse models of spontaneous lung metastasis revealed that mutant or overexpressed NRAS promotes lung colonization by regulating interleukin‐8‐related chemokine expression, thereby initiating interactions between tumor cells, the pulmonary vasculature, and myeloid cells. Our results support a model where NRAS‐mutant, chemokine‐expressing circulating tumor cells target the CXCR1‐expressing lung vasculature and recruit CXCR2‐expressing myeloid cells to initiate metastasis. We further describe a clinically relevant approach to prevent NRAS‐driven pulmonary metastasis by inhibiting chemokine signaling. In conclusion, NRAS promotes the colonization of the lungs by various tumor types in mouse models. IL‐8‐related chemokines, NRAS signaling partners in this process, may constitute an important therapeutic target against pulmonary involvement by cancers of other organs.

Allergic asthma is an increasing health problem worldwide. Interestingly, prenatal challenges such as stress have been associated with an increased risk for asthma during childhood. The underlying pathogenesis of how prenatal stress increases the risk for asthma still remains unclear. Potential targets could be that the fetal immune ontogeny or fetal lung development are compromised by prenatal challenges. Here, we aimed to identify whether prenatal stress challenge affects fetal lung development in mice. C57BL/6 pregnant mice were challenged with sound stress and fetal lung development was assessed histologically. Whilst prenatal stress challenge did not profoundly affect lung development in male fetuses, it resulted in less extensive terminal sacs, surrounded by thicker mesenchymal tissue in female fetuses. Thus, prenatal stress disrupted fetal lung development sex-specifically. Interestingly, upon prenatal stress challenge, the airway hyperresponsiveness and eosinophilic inflammation- two hallmarks of asthma - were significantly increased in adult female offspring, whilst regulatory CD4+ T cells were reduced. These findings strongly underpin the sex-specific association between s challenged fetal development and a sex-specific altered severity of asthma in adult offspring. Our model now allows to identify maternal markers through which the risk for asthma and possible other diseases is vertically transferred before birth in response to challenges. Such identification then opens avenues for primary disease prevention.

Background: The cell of origin of lung adenocarcinoma remains elusive. Aims: We repetitively exposed mouse models of lung epithelial fate to the tobacco carcinogen urethane, in order to identify lung adenocarcinoma initiating cells. Methods: Scgb1a1.Cre,Sftpc.Cre and Lyz2.Cre mice expressing Cre recombinase in different lung lineages were crossed to mT/mG Cre -reporter mice expressing GFP in Cre -recombined cells and tdTomato in all others. These lung cell fate reporters (all C57BL/6 ) were examined for GFP-labelling and CCSP, SFTPC and LYZ2 expression before and 6 months after 10 weekly urethane doses (1 g/Kg; n≥10 mice/group). Results: Before carcinogen treatment, Scgb1a1.Cre ; mT/mG mice displayed complete and exclusive GFP labelling of airway, but not alveolar epithelium; Lyz2.Cre ; mT/mG mice of alveolar macrophages and ∼50% of alveolar type II cells; whereas Sftpc.Cre ; mt/mG mice of subsets of both bronchial and alveolar epithelia. Six months after urethane, adenomas and adenocarcinomas were evident. As expected, all cells of all tumors of Sftpc.Cre ; mt/mG mice and all cells of ∼50% of Lyz2.Cre ; mT/mG tumors were GFP+. Interestingly, a significant cell proportion of all tumors of Scgb1a1.Cre ; mT/mG mice were GFP+, indicating a bronchial origin of these cells. Phenotyping of GFP+ adenocarcinoma cells of Scgb1a1.Cre ; mT/mG mice revealed that these bronchial-derived tumor progenitors radiated away from the airways into the distal lung parenchyma upon carcinogen insult, shifting from CCSP+SFTPC-LYZ2- to CCSP-SFTPC+LYZ2-. Conclusions: The above findings challenge our current views of lung tumor cell clonality and origin. Funding: European Research Council Starting Independent Investigator Grant #260524 and State Scholarship Foundation Scholarship.

Background: The reasons why the lungs are preferential metastatic targets for some human cancers are unknown. Aims: To unravel the mechanism of tumor pneumotropism. Methods: Several mouse and human tumor cell lines were genotyped for key oncogenes and tumor suppressors. Their potential for spontaneous lung metastasis was assessed by subcutaneous inoculation into receptive host mice. Mutant oncogenes were silenced via shRNA or introduced using relevant expression vectors. Chemokine signaling was studied using microarray, qPCR, ELISA and immunobloting and was abrogated using chemokine receptor-deficient mice. Results: Spontaneous lung metastasis co-segregated with the presence of NRAS mutations detected in 3 of 11 cell lines studied. The expected frequency of NRAS mutations based on COSMIC (http://cancer.sanger.ac.uk/cosmic/) was tightly correlated (P=0.0000054, R 2 =0.652) with lung metastasis at necropsy in 3827 patients with various cancers (Disibio, G. et al. Arch Pathol Lab Med 2008;132:931–9). Mutant NRAS was required and sufficient for lung colonization since mutant NRAS silencing and overexpression inhibited and installed tumor pneumotropism, respectively. NRAS mutations functioned to up-regulate Cxcl5/Ppbp and CXCL6/7/8 expression by mouse and human tumor cells, respectively, directly targeting circulating tumor cells to the CXCR1+ lung vasculature. Lung-homed tumor cells secondarily recruited CXCR2+ myeloid cells to the lungs. Chemokine signaling was essential for NRAS -dictated lung metastasis, since Cxcr1 and Cxcr2 deficient mice were immune to lung colonization. Conclusions: Mutant NRAS drives lung metastasis via CXCR1/2-mediated signaling events. Funding: European Research Council Starting Independent Investigator Grant #260524.

Background: The immune cells that facilitate malignant pleural effusion (MPE), an immune-mediated end-stage cancer manifestation (Stathopoulos, G.T. et al. Am J Respir Crit Care Med 2012;186:487-92), have not been identified. Aims: We found mast cells (MC) in MPE and investigated their functions. Methods: Human and experimental MPE were assessed for MC content.MPE was induced by intrapleurally injected Lewis lung (LLC) and MC38 colon adenocarcinoma cells in Wt and two separate strains of MC-deficient ( cKitWsh, Cpa3.Cre ) mice. Bone marrow-derived MC were used for MC cell fate and restoration studies. Tumor cells and tumor-exposed MC were subjected to transcriptional profiling. Results: We discovered and characterized MC in human and murine MPE. Cell fate models conveyed that MC were attracted to MPE by tumor-derived CCL2 to be locally degranulated by osteopontin. Both cKitWsh and Cpa3 . Cre mice were protected from MPE induced by both LLC and MC38 cells (mean±SD MPE volume of C57BL/6, cKitWsh and Cpa3 . Cre mice induced by LLC cells: 573±242, 108±130, and 277±284µL; and by MC38 cells: 864±310, 278±323, and 464±203 µL; n = 7-23/group; P Conclusions: Adenocarcinomas instate circuitry with MC to induce MPE once metastatic in the pleural space. Acknowledgements: Supported by ERC-2010-StG-#260524 anda Hellenic Thoracic Society 2012 Research Award.

Background: EGFR/KRAS axis mutations are frequent in human malignantpleuraleffusions (MPE). Aims: To investigate the relationship between perturbations in the EGFR-KRAS axis and malignant pleural effusion development. Methods: Several mouse and human cancer cell lines were characterized for EGFR/KRAS status and for their MPE competence in appropriate hosts. EGFR/KRAS signalling was modulated in various cell lines via standard molecular techniques. MPE-associated inflammation was monitored by bioluminescence imaging, immunophenotyped by flow cytometry, and modulated by splenectomy and adoptive bone marrow transfer. EGFR/KRAS axis was targeted using gefitinib, deltarasin, and anti-CCL2 antibodies. Results: A causative relationship between Δ Kras and MPEwas established by showing that mouse and human cancer cell lines bearing Δ Kras are MPE competent and that activated Kras is capable of conferring MPE competency to human and mouse cells. Furthermore, Kras dependent downstream paracrine signaling to bone marrow activated a distinct GR1+/CD11B+ myeloid cell population, which is maturing in the spleen and is consequently recruited to the pleural cavity in a cancer-elaborated CCL2-dependent way. Splenectomy partially protects hosts from MPE. The pharmacological manipulation of Δ EGFR/ Δ KRAS axis with Gefitinib (targeting Δ EGFR ) or Deltarasin (targeting Δ KRAS ) and the antibody-mediated neutralization of CCL2 completely annihilate MPE formation and the recruitment of CD11b+/GR1+ cells to the pleura. Conclusions: Our work provides insights to MPE pathobiology and a multitude of strategies to target a currently untreatable terminal human condition. Funding: European Research Council Starting Independent Investigator Grant #260524.

Background: The cellular source(s) for alveolar type II (ATII) renewal after lung injury remain(s) elusive. Both CCSP+ bronchial (Kumar, P.A. et al. Cell 2011;147:525-38) and LYZ2+ alveolar (Desai, T.J. et al. Nature 2014;507:190-4) progenitor cells were recently implicated in this process. Aim: To pin the lung stem cells that repopulate the alveoli after ATII cell death. Methods: Scgb1a1.Cre and Lyz2.Cre mice expressing Cre recombinase in different lung lineages were crossed to mT/mG Cre -reporter mice expressing GFP in Cre -recombined cells and tdTomato in all others. These lung cell fate reporters were treated with bleomycin or naphthalene for induction of ATII or bronchial epithelial cell death, respectively. Lungs were serially examined for GFP+ cells and CCSP/SFTPC expression before and after injury. Results: Scgb1a1.Cre;mT/mG offspring displayed complete and exclusive GFP labelling of airway, but not alveolar epithelium, while Lyz2.Cre;mT/mG youngsters exhibited GFP marking of ∼50% of ATII, but not of airway epithelial cells, providing two complementary models of airway versus alveolar cellfate. Aging Scgb1a1.Cre;mT/mG mice manifested spontaneous dispersion of GFP+ bronchial progenitors away from the airways into the distal alveoli, to subsequently express SFTPC and to replace naturally dying ATII cells, a process intensified by bleomycin-induced ATII death. Using both complementary lineage models, we also determined that airway, but not alveolar progenitors, repopulated the bronchi after naphthalene-triggered injury. Conclusions: Bronchial progenitors migrate into the alveoli and attain the ATII phenotype upon lung injury. Funding: European Research Council Starting Independent Investigator Grant #260524.

Background: Carcinogen-inflicted human cancers, including lung tumors harbor thousands of mutations per genome, most of which are unknown (Garraway, L.A. et al, Cell 2013;153:17-37). Aim: To develop a faithful mouse model of human tobacco carcinogen-induced lung adenocarcinoma suitable for the identification of novel oncogenic genes and pathways. Methods: We repeatedly managed to obtain several murine lung adenocarcinoma cell lines (MLA) by chronically exposing various mouse strains to different tobacco carcinogens. MLA were characterized for cancer stemness and oncogenes, as well as global gene expression. Results: To date, 12 MLA cell lines have been derived from Wt and transgenic mice on the FVB , Balb/c , and C57BL/6 strains by means of urethane or diethylnitrosamine exposure. All MLA were immortal, phenotypically stable, and indefinitely passaged in vitro over a period of over 18 months and/or 60 passages. In addition, all cell lines were oncogenic, transplantable, metastatic, and uniformly lethal in vivo . Interestingly, MLA displayed Kras mutations in codon 61, mono- or bi-allelic Trp53 loss, and expression of lung cancer stemness factors Itgb3 and Lgr6 , in amazing similarity to human lung cancers. Microarray revealed that all MLA cell lines heavily overexpressed Prl2c2 , encoding proliferin, in comparison to the native lungs. Prl2c2 silencing diminished MLA proliferation and stemness, to a degree comparable with Itgb3 interference. Conclusions: MLA are faithful models of human lung adenocarcinoma that led to the discovery of Prl2c2 as a candidate lung tumor promoter. Funding: European Research Council Starting Independent Investigator Grant #260524.