958 resultados para EXTRACELLULAR MATRIX REMODELING
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ÁBSTRACT : Mammary gland is composed of two main epithelial cell types, myoepithelial and luminal. The mechanisms involved in determination and maintenance of them remain poorly understood. Notch signaling is known to regulate cell fate determination in other tissues like skin and nervous system. It was also shown that it can act as tumor suppressor or oncogene depending on the tissue type. The mouse models overexpressing active Notch receptors indicated that Notch signaling is oncogenic in the mammary gland. This observation was followed by some descriptive and functional studies in human breast cancer and it was reported that Notch signaling activity or expression of its components are increased in some of the breast tumor samples compared to normal tissue. However, the physiological role of the Notch signaling and its downstream mechanisms in mammary gland is poorly defined. p63, a member of p53 family, has been implicated in the cell fate determination of keratinocytes. Knockout mouse models revealed that p63 is required for the formation of the mammary anlagen in embryo and its ΔN isoform is expressed exclusively in the myoepithelial layer of the adult breast. In order to understand its function in normal breast epithelial cells, I activated Notch signaling by expression of Notch1 intracellular domain (NICD) in normal primary human breast epithelial cells (HBECs). In this context, NICD reduced growth of HBECs and led to downmodulation of extracellular matrix-receptor interaction network (ECM) components as well as ΔNp63. Expression of ΔNp63 together with NICD partially rescued Notch induced growth reduction, which was correlated with an increase in ECM components. Moreover, silencing ΔNp63 in myoepithelial HBECs reduced growth similar to Notch activation and it led to downregulation of myoepithelial and upregulation of luminal markers. Complementing this observation, forced expression of ONp63 in luminal HBECs induced myoepithelial phenotype and decreased luminal markers. In vivo, by the analysis of a Notch reporter mouse strain, I showed that Notch is activated during puberty specifically at the sites of ductal morphogenesis, terminal end buds. FAGS analysis revealed that it can be detected in two different populations based on CD24 expression (low (lo) or high (high)): at lower levels in CD24lo, which includes stem/progenitor and myoepithelial cells and higher levels in CD24hi, which contains luminal cells. In parallel with in vitro results, the CD24lo mouse mammary epithelial cells displaying Notch activity have lower levels of p63 expression. Furthermore, deletion of RBPjk, the main mediator of Notch signaling, or the overexpression of ΔNp63 inhibited luminal cell lineage in vivo. Another important point revealed by Notch reporter mouse strain is the simultaneous activation of Notch with estrogen signaling during pubertal development. The expression of FOXA1, the mediator of estrogen receptor (ER) transcriptional activity, is correlated with Notch activation in vivo that it is lower in CD24lo than in CD24hi cells. Moreover, FOXA1 is regulated by NICD in vitro supporting the presence of a link between Notch and ER signaling. Taken together, I report that Notch signaling is involved in luminal cell fate determination and its effects are partially mediated through inhibition of ONp63. Besides, ΔNp63 is required for the maintenance and sufficient for the induction of myoepithelial phenotype in HBECs in vitro and is not compatible with luminal lineage in vivo. Based on these results, I propose a model for epithelial cell hierarchy in mammary gland, whereby there are two different types of luminal progenitors, early and late, displaying different levels of Notch activity. Notch signaling contributes to the determination of luminal cell lineage in these two progenitor steps: In "Early Luminal Progenitor" stage, it inhibits myoepithelial fate by decreasing p63 expression, and in "Late Luminal Progenitor" stage, Notch signaling is involved in induction of luminal lineage by acting on ER-FOXA1 axis. It has to be investigated further whether Notch signaling might behave as an oncogene or tumor suppressor depending on which cell type in the epithelial hierarchy it is modulated and which one is more likely to occur in different human breast cancer types. RÉSUMÉ : La glande mammaire est composée de deux types principaux de cellules: les cellules luminales, qui bordent le lumen et les cellules myoépithéliales, qui se trouvent entre la lame basale et les cellules luminales. Les mécanismes intervenant dans leur différenciation et leur maintenance demeurent encore mal compris. La protéine transmembranaire Notch est connue pour déterminer le destin des cellules dans plusieurs types de tissus comme la peau ou le système nerveux. Selon le type de tissu dans lequel se trouve Notch, il agira soit comme un suppresseur de tumeur soit comme un oncogène. A l'aide de modèles de souris surexprimant les récepteurs actifs de Notch, il a été démontré que la voie de signalisation de Notch est oncogénique au niveau de la glande mammaire. Des études descriptives et fonctionnelles dans le cadre du cancer du sein ont permis de mettre en évidence une augmentation de l'activité de Notch ou de l'expression de ces composants dans certains tissus cancéreux. Toutefois, le rôle physiologique de Notch et des mécanismes qu'il active restent méconnus. P63, une protéine membre de la famille p53, est impliquée dans la différenciation des kératinocytes. Le modèle issu de l'étude des souris p63 knockout a révélé que cette protéine est requise pour la formation des primordia mammaires chez l'embryon et que son isoforme ΔNp63 est exclusivement exprimée dans la couche myoépithéliale de la glande mammaire adulte. Dans le but de comprendre les fonctions physiologiques de Notch, je l'ai activé en exprimant le domaine intracellulaire de Notch 1 (NICD) dans des cellules épithéliales primaires de glande mammaire humaine (HBECs). Le NICD a alors réduit la croissance des HBECs et conduit à la régulation négative non seulement de p63 mais également des composants du réseau d'interaction des récepteurs de la matrice extracellulaire (ECM). En exprimant conjointement ΔNp63 et NICD, il est apparu que la réduction de croissance induite par Notch était partiellement compensée, et qu'il y avait également une augmentation des composants ECM. De plus, lorsque ΔNp63 a été inactivé dans les cellules HBECs myoépithéliales, une réduction de croissance cellulaire identique à celle provoquée par l'activation de Notch a pu être mise en évidence, de même qu'une régulation négative des marqueurs myoépithéliaux ainsi qu'une augmentation des marqueurs luminaux. Afin de compléter ces informations, l'expression de ΔNp63 a été forcée dans les HBECs luminales, ce qui a induit un phénotype myoépithélial et une diminution des marqueurs lumineux. In vivo, par l'analyse de souris ayant un gène rapporteur de l'activité de Notch, j'ai démontré que Notch est activé pendant la puberté au niveau des sites de la morphogenèse canalaire, à savoir les bourgeons terminaux. Les analyses par FACS (Fluorescence-activated cell sorting) basées sur l'expression de l'antigène CD24 ont révélé qu'il peut tre détecté dans deux populations différentes : une population qui l'exprime faiblement, qui regroupe les cellules souches/progéniteurs et les cellules myoépithéliales, et une population qui l'exprime fortement qui est composé des cellules luminales. Parallèlement aux résultats in vitro, j'ai mis en évidence un faible niveau d'expression de p63 dans les cellules épithéliales de la glande mammaire de souris, exprimant faiblement l'antigène CD24 et présentant une activité de Notch. De plus, la délétion de RBPjr~, médiateur principal de la signalisation de Notch, ainsi que la surexpression de ΔNp63 in vivo ont inhibé la lignée des cellules luminales. Un autre point important révélé par les souris rapporteur de l'activité de Notch a été l'activation simultanée de Notch et de la signalisation de l'oestrogène pendant le développement pubertaire. L'expression de FOXA1, médiateur de l'activité transcriptionnelle des récepteurs aux oestrogènes (ER), est en corrélation avec l'activation de Notch in vivo, plus basse dans les cellules avec une faible expression de l'antigène CD24 que dans celles avec une forte expression. De plus, FOXA1 est régulé par NICD in vitro confirmant la présence d'un lien entre Notch et la signalisation des ER. En résumé, la signalisation de Notch est impliquée dans la détermination du destin cellulaire des cellules luminales et ses effets sont partiellement modifiés par l'inhibition de ΔNp63. ΔNp63 est requis pour la maintenance et est suffisant pour l'induction du phénotype myoépithéliale dans les HBECs in vitro et ne peut donc pas se trouver dans les cellules luminales in vivo. Basé sur ces résultats, je propose un modèle de hiérarchisation des cellules épithéliales de la glande mammaire, dans lequel sont présents deux types de progéniteurs des cellules luminales exprimant des niveaux différents d'activité de Notch, les progéniteurs lumineux précoces et tardifs. La signalisation de Notch contribue à la différenciation de la lignée cellulaire luminale au niveau de ces deux progéniteurs : dans la forme précoce, il inhibe la différenciation des cellules myoépithéliales en réduisant l'expression de p63 et dans la forme tardive, Notch est impliqué dans l'induction de la lignée luminale en agissant sur l'axe ER-FOXA1. Il serait nécessaire d'investiguer plus loin si le fait que Notch agisse comme oncogène ou suppresseur de tumeur dépend du stade de différenciation de la cellule dans laquelle il est modulé et laquelle de ces deux fonctions il est le plus probable de rencontrer dans les différents types de cancer du sein.
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ABSTRACT: BACKGROUND: After liver injury, the repair process comprises activation and proliferation of hepatic stellate cells (HSCs), which produce extracellular matrix (ECM) proteins. Peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) is highly expressed in these cells, but its function in liver repair remains incompletely understood. This study investigated whether activation of PPARβ/δ with the ligand GW501516 influenced the fibrotic response to injury from chronic carbon tetrachloride (CCl4) treatment in mice. Wild type and PPARβ/δ-null mice were treated with CCl4 alone or CCl4 co-administered with GW501516. To unveil mechanisms underlying the PPARβ/δ-dependent effects, we analyzed the proliferative response of human LX-2 HSCs to GW501516 in the presence or absence of PPARβ/δ. RESULTS: We found that GW501516 treatment enhanced the fibrotic response. Compared to the other experimental groups, CCl4/GW501516-treated wild type mice exhibited increased expression of various profibrotic and pro-inflammatory genes, such as those involved in extracellular matrix deposition and macrophage recruitment. Importantly, compared to healthy liver, hepatic fibrotic tissues from alcoholic patients showed increased expression of several PPAR target genes, including phosphoinositide-dependent kinase-1, transforming growth factor beta-1, and monocyte chemoattractant protein-1. GW501516 stimulated HSC proliferation that caused enhanced fibrotic and inflammatory responses, by increasing the phosphorylation of p38 and c-Jun N-terminal kinases through the phosphoinositide-3 kinase/protein kinase-C alpha/beta mixed lineage kinase-3 pathway. CONCLUSIONS: This study clarified the mechanism underlying GW501516-dependent promotion of hepatic repair by stimulating proliferation of HSCs via the p38 and JNK MAPK pathways.
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PURPOSE: Recently, the authors identified a gene, BIGH3, in which different mutations cause a group of hereditary corneal dystrophies: lattice type I and IIIA (CDLI and CDLIIIA), granular Groenouw type I (CDGGI), Avellino (CDA), and Reis-Bücklers' (CDRB). All these disorders are characterized by the progressive accumulation of corneal deposits with different structural organization. Experiments were conducted to determine the role of kerato-epithelin (KE), the product of BIGH3, in the pathogenesis of the diseases. METHODS: KE-15 and KE-2, two rabbit antisera raised against peptides from the 69-364 and 426 - 682 amino acid regions of KE respectively, were used for immunohistology of the corneas obtained after keratoplasty in six CDLI patients, three CDGGI patients, and one CDA patient. RESULTS: The nonamyloid deposits observed in CDGGI stained intensively with KE-15 and KE-2, whereas the amyloid deposits in all analyzed CDLI corneas reacted to KE-2 but not to KE-15. In the CDA cornea, where amyloid and nonamyloid inclusions were present, positive staining with both antisera was observed. CONCLUSIONS: Pathologic amyloid and nonamyloid deposits observed in CDLI, CDGGI-, and CDA-affected corneas are caused by KE accumulation. Different staining patterns of amyloid and nonamyloid deposits observed with antibodies against the amino and carboxyl termini of KE suggest that two mechanisms of KE misfolding are implicated in the pathogenesis of 5q31-linked corneal dystrophies.
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Mapping the transcription start points of the eap, emp, and vwb promoters revealed a conserved octanucleotide sequence (COS). Deleting this sequence abolished the expression of eap, emp, and vwb. However, electrophoretic mobility shift assays gave no evidence that this sequence was a binding site for SarA or SaeR, known regulators of eap and emp.
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The precise localization of extracellular matrix and cell wall components is of critical importance for multicellular organisms. Lignin is a major cell wall modification that often forms intricate subcellular patterns that are central to cellular function. Yet the mechanisms of lignin polymerization and the subcellular precision of its formation remain enigmatic. Here, we show that the Casparian strip, a lignin-based, paracellular diffusion barrier in plants, forms as a precise, median ring by the concerted action of a specific, localized NADPH oxidase, brought into proximity of localized peroxidases through the action of Casparian strip domain proteins (CASPs). Our findings in Arabidopsis provide a simple mechanistic model of how plant cells regulate lignin formation with subcellular precision. We speculate that scaffolding of NADPH oxidases to the downstream targets of the reactive oxygen species (ROS) that they produce might be a widespread mechanism to ensure specificity and subcellular precision of ROS action within the extracellular matrix.
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Radioiodinated murine monoclonal antibodies (Mabs) 81C6, Me 1-14, C12, D12, and E9, made against or reactive with human gliomas but not normal brain, and Mab UJ13A, a pan-neuroectodermal Mab reactive with normal human glial and neural cells, were evaluated in paired label studies in the D-54 MG subcutaneous human glioma xenograft model system in nude mice. Following intravenous injection in the tail vein of mice bearing 200-400 mm3 tumors, specific localization of Mabs to tumor over time (6 h-9 days) was evaluated by tissue counting; each Mab demonstrated a unique localization profile. The comparison of localization indices (LI), determined as a ratio of tissue level of Mab to control immunoglobulin with simultaneous correction for blood levels of each, showed Mabs 81C6 and Me 1-14 to steadily accumulate in glioma xenografts, maintaining LI from 5-20 at 7-9 days after Mab injection. Mab UJ13A peaked at day 1, maintaining this level through day 2, and declining thereafter. Mabs D12 and C12 peaked at days 3 and 4, respectively, and E9 maintained an LI of greater than 3 from days 3-9. Percent injected dose localized/g of tumor varied from a peak high of 16% (81C6) to a low of 5% (Me 1-14 and UJ13A). Immunoperoxidase histochemistry, performed with each Mab on a battery of primary human brain neoplasms, revealed that Mabs 81C6 and E9, which demonstrated the highest levels of percent injected dose localized/g of tumor over time, reacted with antigens expressed in the extracellular matrix. This finding suggests that extracellular matrix localization of antigen represents a biologically significant factor affecting localization and/or binding in the xenograft model used. The demonstration of significant localization, varied kinetics and patterns of localization of this localizing Mab panel warrants their continued investigation as potential imaging and therapeutic agents for human trials.
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Despite advances in surgery, radio- and chemotherapy, therapeutic approaches for patients with head and neck squamous carcinoma (HNSCC) need to be improved. Immunotherapies eliciting tumor specific immune responses might constitute novel treatment options. We therefore investigated the expression and immunogenicity of two tumor-associated antigens (TAA) the receptor for hyaluronic acid mediated motility (RHAMM) and carboanhydrase IX (G250/CAIX) in HNSCC patients. Twenty-two HNSCC samples were examined for the expression of RHAMM and G250 by Western blotting and immunohistochemistry, 14/22 samples were tested for HLA-A2 expression by flow cytometry. For 8/22 samples single tumor-cell suspensions were generated, and mixed lymphocyte peptide cultures (MLPC) were performed to evaluate the frequencies of cytotoxic T cells specifically recognizing RHAMM and G250 using Tetramer staining/multi-color flow cytometry and enzyme linked immunosorbent spot (ELISPOT) assays. RHAMM and G250 were expressed in 73 and 80% of the HNSCC samples at the protein level. A co-expression of both TAAs could be detected in 60% of the patients. In 4/8 HLA-A2+ patients, 0.06-0.13% of CD8+ effector T cells recognized Tetramers for RHAMM or G250 and secreted IFNgamma and granzyme B in ELISPOT assays. RHAMM and G250 are expressed at high frequency and high protein level in HNSCCs and are recognized by cytotoxic CD8+ effector T cells. Therefore both TAAs constitute interesting targets for T cell based immunotherapies for HNSCC.
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Objective-Inflammation and proteolysis crucially contribute to myocardial ischemia and reperfusion injury. The extracellular matrix metalloproteinase inducer EMMPRIN (CD147) and its ligand cyclophilin A (CyPA) may be involved in both processes. The aim of the study was to characterize the role of the CD147 and CyPA interplay in myocardial ischemia/reperfusion (I/R) injury.Methods and Results-Immunohistochemistry showed enhanced expression of CD147 and CyPA in myocardial sections from human autopsies of patients who had died from acute myocardial infarction and from mice at 24 hours after I/R. At 24 hours and 7 days after I/R, the infarct size was reduced in CD147(+/-) mice vs CD147(+/+) mice (C57Bl/6), in mice (C57Bl/6) treated with monoclonal antibody anti-CD147 vs control monoclonal antibody, and in CyPA(-/-) mice vs CyPA(+/+) mice (129S6/SvEv), all of which are associated with reduced monocyte and neutrophil recruitment at 24 hours and with a preserved systolic function at 7 days. The combination of CyPA(-/-) mice with anti-CD147 treatment did not yield further protection compared with either inhibition strategy alone. In vitro, treatment with CyPA induced monocyte chemotaxis in a CD147-and phosphatidylinositol 3-kinase-dependent manner and induced monocyte rolling and adhesion to endothelium (human umbilical vein endothelial cells) under flow in a CD147-dependent manner.Conclusion-CD147 and its ligand CyPA are inflammatory mediators after myocardial ischemia and reperfusion and represent potential targets to prevent myocardial I/R injury.
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Ten years ago, the first cellular receptor for the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) and the highly pathogenic Lassa virus (LASV) was identified as alpha-dystroglycan (alpha-DG), a versatile receptor for proteins of the extracellular matrix (ECM). Biochemical analysis of the interaction of alpha-DG with arenaviruses and ECM proteins revealed a strikingly similar mechanism of receptor recognition that critically depends on specific sugar modification on alpha-DG involving a novel class of putative glycosyltransferase, the LARGE proteins. Interestingly, recent genome-wide detection and characterization of positive selection in human populations revealed evidence for positive selection of a locus within the LARGE gene in populations from Western Africa, where LASV is endemic. While most enveloped viruses that enter the host cell in a pH-dependent manner use clathrin-mediated endocytosis, recent studies revealed that the Old World arenaviruses LCMV and LASV enter the host cell predominantly via a novel and unusual endocytotic pathway independent of clathrin, caveolin, dynamin, and actin. Upon internalization, the virus is rapidly delivered to endosomes via an unusual route of vesicular trafficking that is largely independent of the small GTPases Rab5 and Rab7. Since infection of cells with LCMV and LASV depends on DG, this unusual endocytotic pathway could be related to normal cellular trafficking of the DG complex. Alternatively, engagement of arenavirus particles may target DG for an endocytotic pathway not normally used in uninfected cells thereby inducing an entry route specifically tailored to the pathogen's needs.
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Tenascins are extracellular matrix proteins present during the development of organisms as well as in pathological conditions. Tenascin-W, the fourth and last member of the tenascin family remains the least well-characterized one. Our study aimed to evaluate the potential significance of tenascin-W as cancer biomarker by monitoring its presence in the serum of colorectal and breast cancer patients and its expression in colorectal tumor tissues. To measure serum tenascin-W levels, a sensitive sandwich-ELISA was established. Mean tenascin-W concentration in sera of patients with nonmetastatic colorectal cancer at time of diagnosis was highly increased compared to that of healthy volunteers. A similar tendency was observed for tenascin-C in the same patient cohort. However, the increase was much more striking for tenascin-W. We also detected elevated tenascin-W levels in sera of breast cancer patients. Furthermore, we could show a prominent expression of tenascin-W in extracts from colorectal tumor tissues by immunoblot analysis, whereas tenascin-W was not detectable in the corresponding normal colon mucosa. To confirm the western blot results, we performed immunohistochemistry of frozen sections of the same patients as well as of an additional, independently chosen collection of colorectal cancer tissues. In all cases, similarly to tenascin-C, tenascin-W was detected in the tumor stroma. Our results reveal a clear association between elevated levels of tenascin-W and the presence of cancer. These results warrant further studies to evaluate the potential value of serum and tissue tenascin-W levels as diagnostic, prognostic or monitoring biomarker in colorectal, breast and possibly other solid cancers.
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The dopamine antagonist [3H]-domperidone-[3H]-DOM-bound to a single class of high-affinity (Kd = 1.24 +/- 0.14 nM) and saturable receptors on dispersed bovine anterior pituitary (AP) cells. The binding of [3H]-DOM was stereoselective and reversible with agonists and antagonists. Dopamine competitions for [3H]-DOM binding modeled best for a single site consistent with an interaction with a homogeneous population of receptors. The mean number of specific binding sites labeled by [3H]-DOM was 53,000 per cell in dispersed AP cells consisting of 42% lactotrophs. Dispersed bovine AP cells attached to extracellular matrix within 3 h, and prolactin secretion from these cells was effectively inhibited by dopamine. Several observations suggested that [3H]-DOM-labeled receptors on dispersed bovine AP cells were restricted to the outer plasma membrane and not internalized. These included (1) the rapid and complete dissociation of specific [3H]-DOM binding; (2) the ability of treatment with acid or proteolytic enzymes to entirely remove specifically bound [3H]-DOM, and (3) the lack of effect of metabolic inhibitors on specific [3H]-DOM binding.
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The genetic dissection of the phenotypes associated with Williams-Beuren Syndrome (WBS) is advancing thanks to the study of individuals carrying typical or atypical structural rearrangements, as well as in vitro and animal studies. However, little is known about the global dysregulations caused by the WBS deletion. We profiled the transcriptomes of skin fibroblasts from WBS patients and compared them to matched controls. We identified 868 differentially expressed genes that were significantly enriched in extracellular matrix genes, major histocompatibility complex (MHC) genes, as well as genes in which the products localize to the postsynaptic membrane. We then used public expression datasets from human fibroblasts to establish transcription modules, sets of genes coexpressed in this cell type. We identified those sets in which the average gene expression was altered in WBS samples. Dysregulated modules are often interconnected and share multiple common genes, suggesting that intricate regulatory networks connected by a few central genes are disturbed in WBS. This modular approach increases the power to identify pathways dysregulated in WBS patients, thus providing a testable set of additional candidates for genes and their interactions that modulate the WBS phenotypes.
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A new type of high avidity binding molecule, termed "peptabody" was created by harnessing the effect of multivalent interaction. A short peptide ligand was fused via a semi-rigid hinge region with the coiled-coil assembly domain of the cartilage oligomeric matrix protein, resulting in a pentameric multivalent binding molecule. In the first peptabody (Pab-S) described here, a peptide (S) specific for the mouse B-cell lymphoma BCL1 surface Ig idiotype, was selected from a phage display library. A fusion gene was constructed encoding peptide S, followed by the 24 aa hinge region from camel IgG and a modified 55 aa cartilage oligomeric matrix protein pentamerization domain. The Pab-S fusion protein was expressed in Escherichia coli in a soluble form at high levels and purified in a single step by metal-affinity chromatography. Pab-S specifically bound the BCL1 surface idiotype with an avidity of about 1 nM, which corresponds to a 2 x 10(5)-fold increase compared with the affinity of the synthetic peptide S itself. Biochemical characterization showed that Pab-S is a stable homopentamer of about 85 kDa, with interchain disulfide bonds. Pab-S can be dissociated under denaturing and reducing conditions and reassociated as a pentamer with full-binding activity. This intrinsic feature provides an easy way to combine Pab molecules with two different peptide specificities, thus producing heteropentamers with bispecific and/or chelating properties.
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BACKGROUND: Engraftment of primary pancreas ductal adenocarcinomas (PDAC) in mice to generate patient-derived xenograft (PDX) models is a promising platform for biological and therapeutic studies in this disease. However, these models are still incompletely characterized. Here, we measured the impact of the murine tumor environment on the gene expression of the engrafted human tumoral cells. METHODS: We have analyzed gene expression profiles from 35 new PDX models and compared them with previously published microarray data of 18 PDX models, 53 primary tumors and 41 cell lines from PDAC. The results obtained in the PDAC system were further compared with public available microarray data from 42 PDX models, 108 primary tumors and 32 cell lines from hepatocellular carcinoma (HCC). We developed a robust analysis protocol to explore the gene expression space. In addition, we completed the analysis with a functional characterization of PDX models, including if changes were caused by murine environment or by serial passing. RESULTS: Our results showed that PDX models derived from PDAC, or HCC, were clearly different to the cell lines derived from the same cancer tissues. Indeed, PDAC- and HCC-derived cell lines are indistinguishable from each other based on their gene expression profiles. In contrast, the transcriptomes of PDAC and HCC PDX models can be separated into two different groups that share some partial similarity with their corresponding original primary tumors. Our results point to the lack of human stromal involvement in PDXs as a major factor contributing to their differences from the original primary tumors. The main functional differences between pancreatic PDX models and human PDAC are the lower expression of genes involved in pathways related to extracellular matrix and hemostasis and the up- regulation of cell cycle genes. Importantly, most of these differences are detected in the first passages after the tumor engraftment. CONCLUSIONS: Our results suggest that PDX models of PDAC and HCC retain, to some extent, a gene expression memory of the original primary tumors, while this pattern is not detected in conventional cancer cell lines. Expression changes in PDXs are mainly related to pathways reflecting the lack of human infiltrating cells and the adaptation to a new environment. We also provide evidence of the stability of gene expression patterns over subsequent passages, indicating early phases of the adaptation process.
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It is currently unclear whether tissue changes surrounding multifocal epithelial tumors are a cause or consequence of cancer. Here, we provide evidence that loss of mesenchymal Notch/CSL signaling causes tissue alterations, including stromal atrophy and inflammation, which precede and are potent triggers for epithelial tumors. Mice carrying a mesenchymal-specific deletion of CSL/RBP-Jκ, a key Notch effector, exhibit spontaneous multifocal keratinocyte tumors that develop after dermal atrophy and inflammation. CSL-deficient dermal fibroblasts promote increased tumor cell proliferation through upregulation of c-Jun and c-Fos expression and consequently higher levels of diffusible growth factors, inflammatory cytokines, and matrix-remodeling enzymes. In human skin samples, stromal fields adjacent to multifocal premalignant actinic keratosis lesions exhibit decreased Notch/CSL signaling and associated molecular changes. Importantly, these changes in gene expression are also induced by UVA, a known environmental cause of cutaneous field cancerization and skin cancer.