Robert J.J. O'Donoghue

Myeloperoxidase Deficiency Attenuates Lipopolysaccharide-Induced Acute Lung Inflammation and Subsequent Cytokine and Chemokine Production

Lung neutrophilia is common to a variety of lung diseases. The production of reactive oxygen and nitrogen species during neutrophil oxidative burst has been associated with protein and DNA damage. Myeloperoxidase (MPO) is an enzyme stored in the azurophilic granula of neutrophils. It is important in host defense because it generates the reactive oxidant hypochlorous acid and has been described to play a role in the activation of neutrophils during extravasation. We hypothesized that MPO contributes directly to the development of acute lung neutrophilia via stimulation of neutrophil extravasation and indirectly to the subsequent production of cytokines and chemokines in the lung. To test this hypothesis, wild-type (WT) and Mpo−/− mice were given a single LPS instillation, after which the development of neutrophil-dominated lung inflammation, oxidative stress, and cytokine and chemokine levels were examined. Mpo−/− mice demonstrated a decreased lung neutrophilia that peaked earlier than neutrophilia in WT mice, which can be explained by decreased neutrophil chemoattractant levels in LPS-exposed Mpo−/− compared with WT mice. However, oxidative stress levels were not different in LPS-exposed WT and Mpo−/− mice. Furthermore, in vivo findings were confirmed by in vitro studies, using isolated neutrophils. These results indicate that MPO promotes the development of lung neutrophilia and indirectly influences subsequent chemokine and cytokine production by other cell types in the lung.

Genetic partitioning of interleukin-6 signalling in mice dissociates Stat3 from Smad3-mediated lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease that is unresponsive to current therapies and characterized by excessive collagen deposition and subsequent fibrosis. While inflammatory cytokines, including interleukin (IL)‐6, are elevated in IPF, the molecular mechanisms that underlie this disease are incompletely understood, although the development of fibrosis is believed to depend on canonical transforming growth factor (TGF)‐β signalling. We examined bleomycin‐induced inflammation and fibrosis in mice carrying a mutation in the shared IL‐6 family receptor gp130. Using genetic complementation, we directly correlate the extent of IL‐6‐mediated, excessive Stat3 activity with inflammatory infiltrates in the lung and the severity of fibrosis in corresponding gp130757F mice. The extent of fibrosis was attenuated in B lymphocyte‐deficient gp130757F;µMT−/− compound mutant mice, but fibrosis still occurred in their Smad3−/− counterparts consistent with the capacity of excessive Stat3 activity to induce collagen 1α1 gene transcription independently of canonical TGF‐β/Smad3 signalling. These findings are of therapeutic relevance, since we confirmed abundant STAT3 activation in fibrotic lungs from IPF patients and showed that genetic reduction of Stat3 protected mice from bleomycin‐induced lung fibrosis.

TGF-β signaling in stromal cells acts upstream of FGF-10 to regulate epithelial stem cell growth in the adult lung

Tissue resident mesenchymal stromal cells (MSCs) contribute to tissue regeneration through various mechanisms, including the secretion of trophic factors that act directly on epithelial stem cells to promote epithelialization. However, MSCs in tissues constitute a heterogeneous population of stromal cells and different subtypes may have different functions. In this study we show that CD166(neg) and CD166(pos) lung stromal cells have different proliferative and differentiative potential. CD166(neg) lung stromal cells exhibit high proliferative potential with the capacity to differentiate along the lipofibroblastic and myofibroblastic lineages, whereas CD166(pos) lung stromal cells have limited proliferative potential and are committed to the myofibroblastic lineage. Moreover, we show that CD166(pos) lung stromal cells do not share the same epithelial-supportive capacity as their CD166(neg) counterparts, which support the growth of lung epithelial stem cell (EpiSPC) colonies in vitro. In addition, ex vivo expansion of lung stromal cells also resulted in the loss of epithelial-supportive capacity, which could be reinstated by inhibition of the TGF-β signaling pathway. We show that epithelial-supportive capacity correlated with the level of FGF-10 expression and the reactivation of several lung development-associated genes. In summary, these studies suggest that TGF-β signaling in stromal cells acts upstream of FGF-10 to regulate epithelial stem cell growth in the adult lung.

Scrib heterozygosity predisposes to lung cancer and cooperates with KRas hyperactivation to accelerate lung cancer progression in vivo.

Lung cancer is the leading cause of cancer deaths worldwide with non small-cell lung cancer (NSCLC) accounting for 80% of all lung cancers. Although activating mutations in genes of the RAS-MAPK pathway occur in up to 30% of all NSCLC, the cooperating genetic lesions that are required for lung cancer initiation and progression remain poorly understood. Here we identify a role for the cell polarity regulator Scribble (Scrib) in NSCLC. A survey of genomic databases reveals deregulation of SCRIB in human lung cancer and we show that Scrib+/− mutant mice develop lung cancer by 540 days with a penetrance of 43%. To model NSCLC development in vivo, we used the extensively characterized LSL-KRasG12D murine model of NSCLC. We show that loss of Scrib and activated oncogenic KRas cooperate in vivo, resulting in more aggressive lung tumors, likely due to a synergistic elevation in RAS–MAPK signaling. Finally, we provide data consistent with immune infiltration having an important role in the acceleration of tumorigenesis in KRasG12D lung tumors following Scrib loss.

STAT3: a central mediator of pulmonary fibrosis?

Pulmonary fibrosis is a devastating, relentlessly progressive, and lethal disease. There is a significant unmet need for effective treatment since currently no FDA-approved therapies exist. Current thinking suggests that idiopathic pulmonary fibrosis (IPF) is initiated by pathways similar to normal wound healing, but relentless fibrosis occurs secondary to absent or defective inhibitory mechanisms that normally terminate wound healing. The heterogeneous pathological presentation of fibrosis suggests that the anatomic location and origin of fibroblasts and other cells might be critical for their phenotype and function and will impact on strategies to prevent or treat fibrotic lung diseases. This review summarizes our current understanding of the pathobiology of IPF, with a specific focus on the role of STAT3 in regulating cellular responses that may contribute to or inhibit pro-fibrotic processes. An improved understanding of the complex cell-type specific roles that this transcription factor plays in normal lung and in fibrosis is required to determine its suitability as an effective therapeutic target.

Inhibition of Hematopoietic Cell Kinase Activity Suppresses Myeloid Cell-Mediated Colon Cancer Progression

Aberrant activation of the SRC family kinase hematopoietic cell kinase (HCK) triggers hematological malignancies as a tumor cell-intrinsic oncogene. Here we find that high HCK levels correlate with reduced survival of colorectal cancer patients. Likewise, increased Hck activity in mice promotes the growth of endogenous colonic malignancies and of human colorectal cancer cell xenografts. Furthermore, tumor-associated macrophages of the corresponding tumors show a pronounced alternatively activated endotype, which occurs independently of mature lymphocytes or of Stat6-dependent Th2 cytokine signaling. Accordingly, pharmacological inhibition or genetic reduction of Hck activity suppresses alternative activation of tumor-associated macrophages and the growth of colon cancer xenografts. Thus, Hck may serve as a promising therapeutic target for solid malignancies.

Mouse models for gastric cancer: Matching models to biological questions

Gastric cancer is the third leading cause of cancer‐related mortality worldwide. This is in part due to the asymptomatic nature of the disease, which often results in late‐stage diagnosis, at which point there are limited treatment options. Even when treated successfully, gastric cancer patients have a high risk of tumor recurrence and acquired drug resistance. It is vital to gain a better understanding of the molecular mechanisms underlying gastric cancer pathogenesis to facilitate the design of new‐targeted therapies that may improve patient survival. A number of chemically and genetically engineered mouse models of gastric cancer have provided significant insight into the contribution of genetic and environmental factors to disease onset and progression. This review outlines the strengths and limitations of current mouse models of gastric cancer and their relevance to the pre‐clinical development of new therapeutics.