SciCombinator

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Journal: The Journal of pathology

28

Fibroblasts and myofibroblasts are the key effector cells executing physiologic tissue repair leading to regeneration on one hand, and pathological fibrogenesis leading to chronic fibrosing conditions on the other. Recent studies identify the multifunctional transcription factor Early Growth Response-1(Egr-1) as an important mediator of fibroblast activation triggered by diverse stimuli. Egr-1 has potent stimulatory effects on fibrotic gene expression, and aberrant Egr-1 expression or function is associated with animal models of fibrosis and human fibrotic disorders including emphysema, pulmonary fibrosis, pulmonary hypertension and systemic sclerosis. Pharmacological suppression or genetic targeting of Egr-1 blocks fibrotic responses in vitro and ameliorates experimental fibrosis in the skin and lung. In contrast, Egr-1 appear to acts as a negative regulator of hepatic fibrosis in mouse models, suggesting a context-dependent role in fibrosis. The Egr-1-binding protein Nab2 is an endogenous inhibitor of Egr-1-mediated signaling, and abrogates the stimulation of fibrotic responses induced by transforming growth factor-ß (TGF-ß). Moreover, mice deficient in Nab2 show excessive collagen accumulation in the skin. These observations highlight a previously unsuspected fundamental physiologic function for the Egr-1/Nab2 signaling axis in regulating fibrogenesis, and suggest that Egr-1 may be a potential novel therapeutic target in human diseases complicated by fibrosis. This review summarizes recent advances in understanding the regulation and complex functional role of Egr-1 and its related proteins and inhibitors in pathological fibrosis. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Concepts: DNA, Gene, Gene expression, Cancer, Transcription, Fibrosis, Idiopathic pulmonary fibrosis, Scleroderma

24

As the age of the population increases in many nations, age-related degenerative diseases pose significant socioeconomic challenges. One of the key degenerative diseases that compromise quality of life is age-related macular degeneration (AMD). AMD is a multi-faceted condition that affects the central retina, which ultimately leads to blindness in millions of people worldwide. The pathophysiology and risk factors for AMD are complex, and the symptoms manifest in multiple related but distinct forms. The ability to develop effective treatments for AMD will depend on a thorough understanding of the underlying pathophysiology, risk factors, and driver molecular pathways, as well as the ability to develop useful animal models. This review provides an overview of the aforementioned aspects in AMD. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Concepts: Retina, John Wiley & Sons, Macular degeneration, United Kingdom of Great Britain and Ireland, Great Britain, Kingdom of Great Britain, Ireland, Accessible publishing

19

Numerous studies have explored the altered transcriptional landscape associated with skin diseases to understand the nature of these disorders. However, data interpretation represents a significant challenge due to a lack of good maker sets for many of the specialised cell types that make up this tissue, whose composition may fundamentally alter during disease. Here we have sought to derive expression signatures that define the various cell types and structures that make up human skin, and demonstrate how they can be used to aid the interpretation of transcriptomic data derived from this organ. Two large normal skin transcriptomics datasets were identified, one RNA-seq (n = 578), the other microarray (n = 165), quality controlled and subjected separately to network-based analyses to identify clusters of robustly co-expressed genes. The biological significance of these clusters was then assigned using a combination of bioinformatics analyses, literature and expert review. After cross comparison between analyses, 20 gene signatures were defined. These include expression signatures for hair follicles, glands (sebaceous, sweat, apocrine), keratinocytes, melanocytes, endothelia, muscle, adipocytes, immune cells, and a number of pathway systems. Collectively we have named this resource SkinSig. SkinSig was then used in the analysis of transcriptomic datasets for 18 skin conditions, providing in-context interpretation of these data. For instance, conventional analysis has shown there to be a decrease in keratinisation and fatty metabolism with age; we more accurately define these changes to be due to loss of hair follicles and sebaceous glands. SkinSig also highlighted the over-/under-representation of various cell types in skin diseases, reflecting an influx in immune cells in inflammatory disorders and a relative reduction in other cell types. Overall, our analyses demonstrate the value of this new resource in defining the functional profile of skin cell types and appendages, and in improving the interpretation of disease data.

Concepts: DNA, Protein, Gene, Gene expression, Cell, Skin, Hair follicle, Sebaceous gland

6

The common preference of cancers for lactic acid-generating metabolic energy pathways has led to proposals that their reprogrammed metabolism confers growth advantages such as decreased susceptibility to hypoxic stress. Recent observations, however, suggest it generates a novel way for cancer survival. There is increasing evidence that cancers can escape immune destruction by suppressing the anticancer immune response through maintaining a relatively low pH in their micro-environment. Tumours achieve this by regulating lactic acid secretion via modification of glucose/glutamine metabolisms. We propose that the maintenance by cancers of a relatively low pH in their micro-environment, via regulation of their lactic acid secretion through selective modification of their energy metabolism, is another major mechanism by which cancers can suppress the anticancer immune response. Cancer-generated lactic acid could thus be viewed as a critical, immunosuppressive metabolite in the tumour micro-environment. This paradigm shift views cancer-generated lactic acid as a critical, regulatory immunosuppressive metabolite rather than a “waste product” and can have major impact on therapeutic strategy development.

Concepts: Immune system, Carbon dioxide, Cancer, Oncology, Metabolism, Adenosine triphosphate, Biochemistry, Lactic acid

5

Anti-angiogenic therapies have shown limited efficacy in the clinical management of metastatic disease, including lung metastases. Moreover, the mechanisms via which tumours resist anti-angiogenic therapies are poorly understood. Importantly, rather than utilising angiogenesis, some metastases may instead incorporate pre-existing vessels from surrounding tissue (vessel co-option). Since anti-angiogenic therapies were designed to target only new blood vessel growth, vessel co-option has been proposed as a mechanism that could drive resistance to anti-angiogenic therapy. However, vessel co-option has not been extensively studied in lung metastases, and its potential to mediate resistance to anti-angiogenic therapy in lung metastases is not established. Here we examine the mechanism of tumour vascularisation in 164 human lung metastasis specimens (composed of breast, colorectal and renal cancer lung metastasis cases). We identify four distinct histopathological growth patterns (HGPs) of lung metastasis (alveolar, interstitial, perivascular cuffing and pushing) that each vascularise via a different mechanism. In the alveolar HGP, cancer cells invade the alveolar air spaces, which facilitates the co-option of alveolar capillaries. In the interstitial HGP, cancer cells invade into the alveolar walls to co-opt alveolar capillaries. In the perivascular cuffing HGP, cancer cells grow by co-opting larger vessels of the lung. Only in the pushing HGP did the tumours vascularise by angiogenesis. Importantly, vessel co-option occurred with high frequency, being present in over 80% of the cases examined. Moreover, we provide evidence that vessel co-option mediates resistance to the anti-angiogenic drug sunitinib in preclinical lung metastasis models. Assuming that our interpretation of the data is correct, we conclude that vessel co-option in lung metastases occurs through at least three distinct mechanisms, that vessel co-option occurs frequently in lung metastases and that vessel co-option could mediate resistance to anti-angiogenic therapy in lung metastases. Novel therapies designed to target both angiogenesis and vessel co-option are therefore warranted.

Concepts: Cancer, Breast cancer, Metastasis, Oncology, Lung cancer, Angiogenesis, Prostate cancer, Testicular cancer

4

N-WASP (WASL) is a widely expressed cytoskeletal signalling and scaffold protein also implicated in regulation of Wnt signalling and homeostatic maintenance of skin epithelial architecture. N-WASP mediates invasion of cancer cells in vitro and its depletion reduces invasion and metastatic dissemination of breast cancer. Given this role in cancer invasion and universal expression in the gastrointestinal tract, we explored a role for N-WASP in the initiation and progression of colorectal cancer. While deletion of N-wasp is not detectably harmful in the murine intestinal tract, numbers of Paneth cells increased, indicating potential changes in the stem cell niche and migration up the crypt-villus axis was enhanced. Loss of N-wasp promoted adenoma formation in an adenomatous polyposis coli (Apc) deletion model of intestinal tumourigenesis. Thus, we establish a tumour suppressive role of N-WASP in early intestinal carcinogenesis despite its later pro-invasive role in other cancers. Our study highlights that while the actin cytoskeletal machinery promotes invasion of cancer cells, it also maintains normal epithelial tissue function and thus may have tumour suppressive roles in pre-neoplastic tissues.

Concepts: Protein, Gene expression, Cancer, Breast cancer, Metastasis, Oncology, Colorectal cancer, Familial adenomatous polyposis

3

Corpus-dominant lymphocytic gastritis (LyG) is characterized by a CD8(+) T-cell infiltration of the stomach epithelium due to a so far uncharacterized mechanism. While Helicobacter pylori is typically undetectable in LyG, patients respond to H. pylori antibiotic eradication therapy, suggesting a non-H. pylori microbial trigger for the disease. Comparative microbiota analysis of specimens from LyG, H. pylori gastritis and healthy controls precluded involvement of H. pylori in LyG but identified Propionibacterium acnes as a possible disease trigger. In addition, the natural killer group 2 member D (NKG2D) system and the proinflammatory cytokine IL15 are significantly upregulated in the gastric mucosa of LyG patients, and gastric epithelial cells respond to microbe-derived stimuli, including live P. acnes and the microbial products short-chain fatty acids, with induction of NKG2D ligands. In contrast, H. pylori infection does not activate or even repress NKG2D ligands. Together, our findings identify P. acnes as a possible causative agent for LyG, which is dependent on the NKG2D system and IL15 activation.

Concepts: Bacteria, Epithelium, Stomach, Helicobacter pylori, Peptic ulcer, Helicobacter, Urease, Gastritis

3

Stromal targeting for pancreatic ductal adenocarcinoma (PDAC) is rapidly becoming an attractive option, due to lack of efficacy of standard chemotherapy and increased knowledge about PDAC stroma. We postulated that the addition of stromal therapy may enhance the anti-tumour efficacy of chemotherapy. Gemcitabine and all-trans retinoic acid (ATRA) were combined in a clinically applicable regimen, to target cancer cells and pancreatic stellate cells (PSC) respectively, in 3D organotypic culture models and genetically engineered mice (LSL-Kras(G12D) (/+) ;LSL-Trp53(R172H) (/+) ;Pdx-1-Cre: KPC mice) representing the spectrum of PDAC. In two distinct sets of organotypic models as well as KPC mice, we demonstrate a reduction in cancer cell proliferation and invasion together with enhanced cancer cell apoptosis when ATRA is combined with gemcitabine, compared to vehicle or either agent alone. Simultaneously, PSC activity (as measured by deposition of extra-cellular matrix proteins such as collagen and fibronectin), and PSC invasive ability were both diminished in response to combination therapy. These effects were mediated through a range of signalling cascades (Wnt, hedgehog, retinoid and FGF) in cancer as well as stellate cells, affecting epithelial cellular functions such as epithelial-mesenchymal transition, cellular polarity and lumen formation. At the tissue level, this resulted in enhanced tumour necrosis, increased vascularity, and diminished hypoxia. Consequently, there was an overall reduction in tumour size. The enhanced effect of stromal co-targeting (ATRA) alongside chemotherapy (gemcitabine) appears to be mediated by dampening multiple signalling cascades in the tumour-stroma cross-talk, rather than ablating stroma or targeting a single pathway.

Concepts: Immune system, Cancer, Oncology, Lung cancer, Cell division, Apoptosis, Cell cycle, Pancreatic cancer

3

The recognition that colorectal cancer (CRC) is a heterogeneous disease in terms of clinical behaviour and response to therapy translates into an urgent need for robust molecular disease subclassifiers that can explain this heterogeneity beyond current parameters (MSI, KRAS, BRAF). Attempts to fill this gap are emerging. The Cancer Genome Atlas (TGCA) reported two main CRC groups, based on the incidence and spectrum of mutated genes, and another paper reported an EMT expression signature defined subgroup. We performed a prior free analysis of CRC heterogeneity on 1113 CRC gene expression profiles and confronted our findings to established molecular determinants and clinical, histopathological and survival data. Unsupervised clustering based on gene modules allowed us to distinguish at least five different gene expression CRC subtypes, which we call surface crypt-like, lower crypt-like, CIMP-H-like, mesenchymal and mixed. A gene set enrichment analysis combined with literature search of gene module members identified distinct biological motifs in different subtypes. The subtypes, which were not derived based on outcome, nonetheless showed differences in prognosis. Known gene copy number variations and mutations in key cancer-associated genes differed between subtypes, but the subtypes provided molecular information beyond that contained in these variables. Morphological features significantly differed between subtypes. The objective existence of the subtypes and their clinical and molecular characteristics were validated in an independent set of 720 CRC expression profiles. Our subtypes provide a novel perspective on the heterogeneity of CRC. The proposed subtypes should be further explored retrospectively on existing clinical trial datasets and, when sufficiently robust, be prospectively assessed for clinical relevance in terms of prognosis and treatment response predictive capacity. Original microarray data were uploaded to the ArrayExpress database (http://www.ebi.ac.uk/arrayexpress/) under Accession Nos E-MTAB-990 and E-MTAB-1026. © 2013 Swiss Institute of Bioinformatics. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Concepts: DNA, Gene, Genetics, Gene expression, Cancer, Molecular biology, Copy number variation, DNA microarray

2

Proliferative diabetic retinopathy (PDR) is a major diabetic microvascular complication characterized by pathological angiogenesis. Several retinopathy animal models have been developed to study the disease mechanisms and putative targets. However, knowledge on the human proliferative disease remains incomplete, relying on steady-state results from thin histological neovascular tissue sections and vitreous samples. New translational models are thus required to comprehensively understand the disease pathophysiology and develop improved therapeutic interventions. We describe here a clinically relevant model, whereby the native multicellular PDR landscape and neo(fibro)vascular processes can be analyzed ex vivo and related to clinical data. As characterized by 3D whole-mount immunofluorescence and electron microscopy, heterogeneity in patient-derived PDR neovascular tissues included discontinuous capillaries coupled with aberrantly differentiated, lymphatic-like, and tortuous endothelia. Spatially-confined apoptosis and proliferation co-existed with inflammatory cell infiltration and unique vascular islet formation. Ex vivo-cultured explants sustained multicellularity, islet patterning and capillary or fibrotic outgrowth in response to vitreoretinal factors. Strikingly, PDR neovascular tissues, whose matched vitreous enhanced lymphatic endothelial cell sprouting, contained lymphatic-like capillaries in vivo and developed Prox1+capillaries and sprouts with lymphatic endothelial ultrastructures ex vivo. Among elaborate vitreal components, VEGFC was one factor found at lymphatic endothelium activating concentrations. These results indicate that the ischemia- and inflammation-induced human PDR microenvironment supports pathological neolymphvascularization, bringing a new concept to the PDR mechanisms and targeting options.

Concepts: Inflammation, Medicine, Blood vessel, Capillary, Cellular differentiation, Endothelium, Cardiovascular system, Diabetic retinopathy