DLL4 Research Articles

Abstract 2188: Genetic variation in angiogenesis-related genes is associated with colorectal cancer risk and prognosis

Abstract Introduction Angiogenesis, the generation of new blood vessels, is crucial in tumor growth, progression, and metastasis. The process involves a variety of factors including signaling, adhesion and chemotactic molecules, ECM (extracellular matrix) proteins, proteinases, transcription factors, growth factors and receptors. Variation in genes encoding these factors potentially influence angiogenic processes. We thus evaluated the association between variants in angiogenesis-related genes and risk as well as prognosis of colorectal cancer (CRC). Approach In a candidate pathway approach, we investigated 437 variants in 36 angiogenesis-related genes for association with CRC risk and prognosis in ∼1800 patients and ∼1800 controls of the German DACHS/IMPACT study. Patients were aged 30 years or older and diagnosed between 2003 and 2007. CRC risk was estimated using conditional logistic regression based on the co-dominant inheritance model. In addition, we investigated the association between polymorphisms and overall survival using multivariable Cox regression. Correction for multiple testing was performed using false discovery rates (FDR). Results Risk Several of the investigated variants in ANGTP1, ETS1, FLT4, MMP2, NOTCH4, PDGFRB, TGFB2 were associated with risk of CRC, and one variant in DLL1 (delta-like 1) remained significant after accounting for multiple testing. DLL1 rs9348307 was associated with decreased risk of CRC (ORGC 0.81, 95% CI 0.68-0.96; ORCC 0.62, 95% CI 0.36-1.06, p=0.02). Survival After a median follow up time of 5 years, variants in twelve genes (ANGPT1, EFNB2, ETS1, FLT4, JAG1, KDR, MMP2, MMP9, NRP1, NRP2, PDGFRB, TGFB2) were associated with overall survival in CRC patients. When accounting for multiple testing, variants in EFNB2, JAG1 and MMP2 remained significant. Most of the EFNB2 variants were associated with poorer survival, while one variant in EFNB2 was associated with better survival (rs2391333: HRCT 0.88, 95% CI 0.74-1.05; HRTT 0.60, 95% CI 0.45-0.78, p<0.001). Furthermore, two variants in JAG1 were associated with worse survival in CRC patients (rs3748480: HRTG 1.27, 95% CI 1.05-1.53; HRGG 1.79, 95% CI 1.02-3.13, p=0.02; rs6040062: HRGA 1.26, 95% CI 1.04-1.52; HRAA 1.78, 95% CI 1.02-3.12, p=0.02). Finally, three variants in MMP2 (rs11639960, rs1561219, rs17301608) were associated with poorer survival, while one MMP2 variant was associated with improved survival in CRC patients (rs243847: HRTC 0.87, 95% CI 0.73-1.04, HRCC 0.60, 95% CI 0.46-0.78, p<0.001). Conclusion Variants in angiogenesis-related genes were associated with CRC risk and overall survival in CRC patients. Two of the identified genes (DLL1 and JAG1) are involved in NOTCH signaling, which is crucial to cell differentiation, proliferation, apoptosis and angiogenesis, underlining the importance of this oncogenic pathway in colorectal carcinogenesis. Citation Format: Dominique Scherer, Yesilda Balavarca, Nina Habermann, Katharina Buck, Petra Seibold, Lisanne Kap, Katja Butterbach, Katrin Pfütze, Axel Benner, Michael Hoffmeister, Hermann Brenner, Barbara Burwinkel, Jenny Chang-Claude, Cornelia M. Ulrich. Genetic variation in angiogenesis-related genes is associated with colorectal cancer risk and prognosis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2188. doi:10.1158/1538-7445.AM2014-2188

ADAM10 and ADAM17 have opposite roles during sprouting angiogenesis.

During angiogenesis, endothelial tip cells start sprouting and express delta-like 4 (DLL4) downstream of vascular endothelial growth factor (VEGF). DLL4 subsequently activates Notch in the adjacent stalk cells suppressing sprouting. VEGF also activates A disintegrin and metalloproteases (ADAMs) that induce Notch ectodomain shedding. Although two major ADAMs, i.e. ADAM10 and ADAM17, have been implicated in Notch-signalling activation, their apparent different roles in angiogenesis have not been fully understood yet. The objective of this study was to determine the roles of ADAM10 and ADAM17 activity in angiogenesis. In mouse retinas, ADAM10 or γ-secretase inhibition induced vascular sprouting and density in vivo, whereas attenuation of both ADAM10 and ADAM17 activity produced the opposite phenotype. Retinal blood vessel analysis in ADAM17 hypomorphic mice confirmed the requirement for ADAM17 activity in angiogenesis. However, ADAM17 inhibition did not phenocopy blood vessel increase by Notch blockage. These observations suggest that ADAM17 regulates other fundamental players during angiogenesis besides Notch, which were not affected by ADAM10. By means of an angiogenesis proteome assay, we found that ADAM17 inhibition induced the expression of a naturally occurring inhibitor of angiogenesis Thrombospondin 1 (TSP1), whereas ADAM10 inhibition did not. Accordingly, ADAM17 overexpression downregulated TSP1 expression, and the TSP1 inhibitor LSKL rescued angiogenesis in the tube formation assay downstream of VEGF in the presence of ADAM17 inhibition. Finally, genetic and pharmacological ADAM17 blockade resulted in increased TSP1 expression in mouse retina. Altogether, our results show that ADAM10 and ADAM17 have opposite effects on sprouting angiogenesis that may be unrelated to Notch signalling and involves differentially expressed anti-angiogenic proteins such as TSP1.

High diluted molecules and gene expression.

High diluted molecules and gene expression.

Spondylocostal dysostosis: follow-up of two cases

AIMS: To report two cases of spondylocostal dysostosis, describing their clinical presentation and evolution.
 
 CASES DESCRIPTION: Two non-related cases of spondylocostal dysostosis are reported. The first case consists of an 11 years old boy, and the second case is a girl with four years of age. In both cases, short neck and trunk, scoliosis, rib and sacrococcygeal anomalies were evident at birth. The clinical diagnosis of spondylocostal dysostosis was confirmed by the finding of a mutation in both alleles of the DLL3 gene. Their clinical evolution was satisfactory, with no respiratory complications until this report. 
 
 CONCLUSIONS: The spondylocostal dysostosis are a group of disorders characterized by severe skeletal malformations, with rib anomalies such as broadening, bifurcation and no symmetric fusion. Although it is known to be a rare situation, its exact incidence or prevalence is not well established. An early diagnosis and appropriate management are extremely important for adequate family counseling and follow-up.

Abstract 327: ETS Factors Regulate the VEGF-Dependent, Arterial-Specific Expression of Dll4

Development of the vascular system begins with vasculogenesis, followed by the specification of endothelial cells into arterial and venous fates. Establishing and maintaining these separate fates is critical for the proper functioning of circulatory networks in the embryo as well as the mature adult. In fact, the congenital condition, Arteriovenous Malformation (AVM), arises due to defects during arterial-venous (AV) specification of endothelial cells, resulting in abnormal AV shunts that may burst leading to vascular lesions and stroke. To date, the molecular processes that control early AV specification remain incompletely understood. In the mouse, Delta-like 4 (Dll4) is a critical mediator of AV identity as loss of only one copy of Dll4 produces AV specification defects and embryonic lethality. Although previous studies have shown that Dll4 is the first Notch ligand expressed in the arterial endothelium and that its expression is induced by Vascular endothelial growth factor, the transcriptional pathways that direct its arterial-specific expression are unknown. Here we report the identification of an arterial-specific enhancer of the Dll4 gene. We show through deletion analyses as well as gain-of-function and loss-of-function studies that Vegf signaling activates ETS factors in the arterial endothelium to drive expression of Dll4. Surprisingly, Notch signaling is not required for the initiation of Dll4 expression but rather functions as a maintenance factor in the arterial endothelium. These studies provide novel mechanistic insight into the transcriptional program that mediates arterial specification and may provide insight into the underlying defects that occur during the development of AVMs.

Endothelial Delta-like 4 (DLL4) promotes renal cell carcinoma hematogenous metastasis.

The Notch ligand Delta-like 4 (DLL4) plays an important role in tumor angiogenesis, which is required for tumor invasion and metastasis. Here we showed that DLL4 was elevated in endothelium and Notch signaling was activated in renal cell carcinoma (RCC). Exogenous DLL4 induced RCC cell migration and invasion by activating intercellular Notch signaling. Importantly, the DLL4/Notch/Hey1/MMP9 cascades connecting the endothelium to the cancer cells in metastasis were identified. Knockdown of Hey1 decreased expression of MMP9 and attenuated tumor invasion. The clinical investigation on 120 cases of RCC specimens indicated that expressions of Hey1 and MMP9 correlated with DLL4 density. Moreover, univariate and multivariate analyses showed that tumor hematogenous metastasis not only was depended on microvessel density but was also associated with tumor size and DLL4 density. During 4-year surveillance, high-level of DLL4 density was associated with a higher probability of developing metastasis and being sensitive to target therapies. Our data suggest that RCC progression is caused in part by activated DLL4/Notch signaling, interaction of endothelium and cells, which can be therapeutically targeted.

Innate lymphoid cells integrate stromal and immunological signals to enhance antibody production by splenic marginal zone B cells.

Innate lymphoid cells (ILCs) regulate stromal, epithelial and immune cells, but their impact on B cells remains unclear. We identified RORγt+ ILCs nearby the marginal zone (MZ), a splenic compartment containing innate-like B cells that respond to circulating T cell-independent (TI) antigens. Spenic ILCs established a bidirectional crosstalk with MAdCAM-1+ marginal reticular cells by providing tumor necrosis factor (TNF) and lymphotoxin, and activated MZ B cells via BAFF, CD40 ligand and the Notch ligand, Delta-like 1. Splenic ILCs further helped MZ B cells and their plasma cell progeny by co-opting neutrophils through the release of GM-CSF. Consequently, ILC depletion impaired both pre- and post-immune TI antibody responses. Thus, ILCs integrate stromal and myeloid signals to orchestrate innate-like antibody production at the interface between the immune and circulatory systems.

O-fucosylation of the Notch Ligand mDLL1 by POFUT1 Is Dispensable for Ligand Function

Fucosylation of Epidermal Growth Factor-like (EGF) repeats by protein O-fucosyltransferase 1 (POFUT1 in vertebrates, OFUT1 in Drosophila) is pivotal for NOTCH function. In Drosophila OFUT1 also acts as chaperone for Notch independent from its enzymatic activity. NOTCH ligands are also substrates for POFUT1, but in Drosophila OFUT1 is not essential for ligand function. In vertebrates the significance of POFUT1 for ligand function and subcellular localization is unclear. Here, we analyze the importance of O-fucosylation and POFUT1 for the mouse NOTCH ligand Delta-like 1 (DLL1). We show by mass spectral glycoproteomic analyses that DLL1 is O-fucosylated at the consensus motif C2XXXX(S/T)C3 (where C2 and C3 are the second and third conserved cysteines within the EGF repeats) found in EGF repeats 3, 4, 7 and 8. A putative site with only three amino acids between the second cysteine and the hydroxy amino acid within EGF repeat 2 is not modified. DLL1 proteins with mutated O-fucosylation sites reach the cell surface and accumulate intracellularly. Likewise, in presomitic mesoderm cells of POFUT1 deficient embryos DLL1 is present on the cell surface, and in mouse embryonic fibroblasts lacking POFUT1 the same relative amount of overexpressed wild type DLL1 reaches the cell surface as in wild type embryonic fibroblasts. DLL1 expressed in POFUT1 mutant cells can activate NOTCH, indicating that POFUT1 is not required for DLL1 function as a Notch ligand.

Characterization of Two Distinct Lymphoproliferative Diseases Caused by Ectopic Expression of the Notch Ligand DLL4 on T Cells

Notch signaling is essential for the development of T cell progenitors through the interaction of NOTCH1 receptor on their surface with the ligand, Delta-like 4 (DLL4), which is expressed by the thymic epithelial cells. Notch signaling is quickly shut down once the cells pass β-selection, and CD4/CD8 double positive (DP) cells are unresponsive to Notch. Over the past two decades a number of papers reported that over-activation of Notch signaling causes T cell acute lymphoblastic leukemia (T-ALL), a cancer that prominently features circulating monoclonal CD4/CD8 double positive T cells in different mouse models. However, the possible outcomes of Notch over-activation at different stages of T cell development are unknown, and the fine timing of Notch signaling that results in T-ALL is poorly understood. Here we report, by using a murine model that ectopically expresses DLL4 on developing T cells, that the T-ALL onset is highly dependent on a sustained Notch activity throughout the DP stage, which induces additional mutations to further boost the signaling. In contrast, a shorter period of Notch activation that terminates at the DP stage causes a polyclonal, non-transmissible lymphoproliferative disorder that is also lethal. These observations resolved the discrepancy of previous papers on DLL4 driven hematological diseases in mice, and show the critical importance of the timing and duration of Notch activity.

Sex Steroid Blockade Enhances Thymopoiesis By Modulating Notch Signaling

Thymopoiesis is a complex process dependent on precise signals from the supporting thymic stromal microenvironment that orchestrates the progression of precursor T cells through well-defined maturation stages. It is well documented that the decline in thymic size and function with age is in part correlated with an increase in sex steroids. This age-related decline in function can be detrimental to the recovery of the thymus in patients receiving radio or chemo-therapy with hematopoietic stem cell transplantation (HSCT). Delayed immune reconstitution, especially in the T cell lineage, is associated with an increased risk of opportunistic infections and malignant relapses. Therefore strategies to enhance thymic reconstitution has the potential to decrease the period of T cell lymphopenia and increase overall clinical outcome.In the process of evaluating the effects of sex steroids in the decline of the thymic function, we found a decrease in the expression of the key thymopoietic factors IL-7, CCL25 and Delta-like 4 (DLL4) by thymic stromal cells after testosterone treatment (Figure 1A). We then addressed if these transcriptional changes were the result of a direct regulation by the androgen receptor (AR). Using a computational approach, and subsequently confirmed by ChIP studies, we found that AR directly bound and negatively regulated the promoter of DLL4, a critical gene involved in T cell commitment and differentiation. We and others have previously shown that sex steroid ablation (SSA) can regenerate young and aged immune system by promoting bone marrow and thymic lymphopoiesis and promoting recovery from autologous and allogeneic HSCT. However the mechanisms underlying the sex steroid-mediate thymic involution and its regeneration after SSA are poorly understood. Moreover, one of the main drawbacks to standard clinical methods of sex steroid ablation using luteinizing hormone releasing hormone (LHRH) agonists (LHRH-Ag) is the initial surge in sex steroids they cause. To address this, we employed a novel class of LHRH-antagonists (LHRH-Ant) that rapidly block the secretion of sex steroids without causing their initial surge that can be even more detrimental to thymopoiesis. Mice treated with LHRH-Ant showed a significantly faster increase in thymic cellularity compared with LHRH-Ag treated mice (Figure 1B). Given the negative regulation of DLL4 by the AR, we hypothesized that DLL4 expression would conversely increase after SSA in vivo. Indeed, we found a significant increase in DLL4 expression after SSA and also an increase in genes downstream of DLL4, such as Ptcra, Hes1 and Cd25 (Figure 1C). We next evaluated if treatment with the LHRH-Ant would provide a faster immune recovery after injury to the immune system. We found that mice treated with LHRH-Ant showed a faster thymic regeneration after total body irradiation (TBI) compared to the control irradiated mice (Figure 1D) and enhanced viral clearance (Figure 1E). Finally, we also found that LHRH-Ant enhanced thymic and peripheral reconstitution up to 3 months after allo-HSCT (Figure 1F). [Display omitted] In conclusion, we found that down-regulation of DLL4 may represent one of the mechanisms underlying the effects of sex steroids on thymic function. We demonstrate that SSA with a novel LHRH-Ant increases DLL4 expression and enhances thymic and peripheral T cell recovery and function after immune injury. These findings suggest that the employment of a LHRH-Ant, which is already in clinical use for prostate cancer patients, represents a novel therapeutic strategy to enhance immune recovery and function in immunocompromised patients. Disclosures:No relevant conflicts of interest to declare.

Maintaining the Plexus

Angiogenesis, a tightly regulated process of new blood vessel formation, is initiated when a select set of endothelial cells is stimulated to leave their quiescent state.1 These cells become hypermigratory and form sprouts that guide the direction of vascular network development.2 Formation of this ordered network depends on a regulated differentiation of the endothelial cells in which only specific endothelial cells can become sprouts. The consequence of dysregulation would be a failure to develop a cohesive vascular network. Examples of this can be seen in vascular diseases, such as CADASIL, and in tumor growth.3,4 Article, see p 1206 The vascular network forms when endothelial sprouts develop at the leading edge of the angiogenic front. These leading sprouts are known as the tip cells, characterized by filopodial expansions, which guide growth toward proangiogenic signals. Behind them are the stalk cells that provide a supporting network through proliferation and lumen formation. A critical component of angiogenesis is the maintenance of a proper balance between the number of tip and stalk cells. The endothelial tip–stalk gradient is established when vascular endothelial growth factor (VEGF) is sensed by the endothelium.5 Higher expression levels of VEGFR2/3 are found in tip cells, making them more responsive to VEGF stimulation and triggering the upregulation of the Notch ligand, Delta-like 4 (DLL4). The DLL4 produced by the tip cell signals to Notch …

Periventricular heterotopia in 6q terminal deletion syndrome: role of the C6orf70 gene

Periventricular nodular heterotopia is caused by defective neuronal migration that results in heterotopic neuronal nodules lining the lateral ventricles. Mutations in filamin A (FLNA) or ADP-ribosylation factor guanine nucleotide-exchange factor 2 (ARFGEF2) cause periventricular nodular heterotopia, but most patients with this malformation do not have a known aetiology. Using comparative genomic hybridization, we identified 12 patients with developmental brain abnormalities, variably combining periventricular nodular heterotopia, corpus callosum dysgenesis, colpocephaly, cerebellar hypoplasia and polymicrogyria, harbouring a common 1.2 Mb minimal critical deletion in 6q27. These anatomic features were mainly associated with epilepsy, ataxia and cognitive impairment. Using whole exome sequencing in 14 patients with isolated periventricular nodular heterotopia but no copy number variants, we identified one patient with periventricular nodular heterotopia, developmental delay and epilepsy and a de novo missense mutation in the chromosome 6 open reading frame 70 (C6orf70) gene, mapping in the minimal critical deleted region. Using immunohistochemistry and western blots, we demonstrated that in human cell lines, C6orf70 shows primarily a cytoplasmic vesicular puncta-like distribution and that the mutation affects its stability and subcellular distribution. We also performed in utero silencing of C6orf70 and of Phf10 and Dll1, the two additional genes mapping in the 6q27 minimal critical deleted region that are expressed in human and rodent brain. Silencing of C6orf70 in the developing rat neocortex produced periventricular nodular heterotopia that was rescued by concomitant expression of wild-type human C6orf70 protein. Silencing of the contiguous Phf10 or Dll1 genes only produced slightly delayed migration but not periventricular nodular heterotopia. The complex brain phenotype observed in the 6q terminal deletion syndrome likely results from the combined haploinsufficiency of contiguous genes mapping to a small 1.2 Mb region. Our data suggest that, of the genes within this minimal critical region, C6orf70 plays a major role in the control of neuronal migration and its haploinsufficiency or mutation causes periventricular nodular heterotopia.

DL4‐mediated Notch signaling is required for the development of fetal αβ and γδ T cells

T-cell development depends upon interactions between thymocytes and thymic epithelial cells (TECs). The engagement of delta-like 4 (DL4) on TECs by Notch1 expressed by blood-borne BM-derived precursors is essential for T-cell commitment in the adult thymus. In contrast to the adult, the earliest T-cell progenitors in the embryo originate in the fetal liver and migrate to the nonvascularized fetal thymus via chemokine signals. Within the fetal thymus, some T-cell precursors undergo programmed TCRγ and TCRδ rearrangement and selection, giving rise to unique γδ T cells. Despite these fundamental differences between fetal and adult T-cell lymphopoiesis, we show here that DL4-mediated Notch signaling is essential for the development of both αβ and γδ T-cell lineages in the embryo. Deletion of the DL4 gene in fetal TECs results in an early block in αβ T-cell development and a dramatic reduction of all γδ T-cell subsets in the fetal thymus. In contrast to the adult, no dramatic deviation of T-cell precursors to alternative fates was observed in the fetal thymus in the absence of Notch signaling. Taken together, our data reveal a common requirement for DL4-mediated Notch signaling in fetal and adult thymopoiesis.

TCFA15, a trimethyl cyclohexenonic long-chain fatty alcohol, affects neural stem fate and differentiation by modulating Notch1 activity

We have investigated the effects of tCFA15, a non-peptidic compound, on the differentiation of neural stem cell-derived neurospheres, and have found that tCFA15 promotes their differentiation into neurons and reduces their differentiation into astrocytes, in a dose-dependent manner. This response is reminiscent of that resulting from the loss-of-function of Notch signaling after inactivation of the Delta-like 1 (Dll1) gene. Further analysis of the expression of genes from the Notch pathway by reverse transcriptase-PCR revealed that tCFA15 treatment results in a consistent decrease in the level of Notch1 mRNA. We have confirmed this result in other cell lines and propose that it reflects a general effect of the tCFA15 molecule. We discuss the implications of this finding with respect to regulation of Notch activity in neural stem cells, and the possible use of tCFA15 as a therapeutic tool for various pathologies that result from impairment of Notch signaling.

Tbx1 regulates brain vascularization

The transcription factor TBX1 is the major gene involved in 22q11.2 deletion syndrome (22q11.2DS). Using mouse models of these diseases, we have previously shown that TBX1 activates VEGFR3 in endothelial cells (EC), and that this interaction is critical for the development of the lymphatic vasculature. In this study, we show that TBX1 regulates brain angiogenesis. Using loss-of-function genetics and molecular approaches, we show that TBX1 regulates the VEGFR3 and DLL4 genes in brain ECs. In mice, loss of TBX1 causes global brain vascular defects, comprising brain vessel hyperplasia, enhanced angiogenic sprouting and vessel network disorganization. This phenotype is recapitulated in EC-specific Tbx1 conditional mutants and in an EC-only 3-dimensional cell culture system (matrigel), indicating that the brain vascular phenotype is cell autonomous. Furthermore, EC-specific conditional Tbx1 mutants have poorly perfused brain vessels and brain hypoxia, indicating that the expanded vascular network is functionally impaired. In EC-matrigel cultures, a Notch1 agonist is able to partially rescue microtubule hyperbranching induced by TBX1 knockdown. Thus, we have identified a novel transcriptional regulator of angiogenesis that exerts its effect in brain by negatively regulating angiogenesis through the DLL4/Notch1-VEGFR3 regulatory axis. Given the similarity of the phenotypic consequences of TBX1 mutation in humans and mice, this unexpected role of TBX1 in murine brain vascularization should stimulate clinicians to search for brain microvascular anomalies in 22q11.2DS patients and to evaluate whether some of the anatomical and functional brain anomalies in patients may have a microvascular origin.

Up-regulation of DLL1 may promote the chemotherapeutic sensitivity in small cell lung cancer

背景与目的DLL1（Delta-Like1）与Notch受体结合激活Notch信号通路，从而决定细胞的分化，并调控多种组织的生长发育。已有研究报道DLL1与肿瘤的生长、分化密切相关。前期基因芯片发现DLL1与小细胞肺癌的耐药性相关，本研究旨在进一步探讨DLL1在小细胞肺癌多药耐药中的作用。方法首先通过QRT-PCR和Western blot从基因和蛋白水平检测化疗敏感细胞株H69及多药耐药细胞株H69AR中DLL1的差异表达；转染DLL1-pIRES2-EGFP表达质粒上调H69AR细胞中的DLL1的表达，构建稳定转染的过表达细胞株H69AR-eGFP-DLL1，通过CCK8检测细胞对各种化疗药物（ADM, DDP, VP-16）的敏感性变化，流式细胞仪检测细胞周期及凋亡的变化。结果DLL1在化疗敏感细胞H69中的表达明显高于H69AR，过表达H69AR中DLL1的表达能够增加细胞对化疗药物的敏感性，促进细胞的凋亡，细胞周期发生G0/G1期及S期阻滞，上调DLL1增加其下游基因HES1、HEY1的表达。结论在小细胞肺癌中上调DLL1的表达可能增加细胞对化疗药物的敏感性，DLL1通过肿瘤细胞间的相互作用激活HES1、HEY1等下游基因，影响小细胞肺癌的多药耐药。

FRI0005 Signal transducer and activator of transcription 3 regulates synovial inflammation through notch/hif1a pathways

BackgroundAngiogenesis is one of the primary events in the pathogenesis of inflammatory arthritis. Notch/HIF signalling interactions regulate angiogenesis and endothelial cell (EC) fate in Rheumatoid Arthritis (RA), however the precise...

Influence of Delta-Like 1 on chemotherapeutic sensitivity of small cell lung cancer

Our study investigated the role of Delta-Like 1 (DLL1) in multi-drug resistance of small cell lung cancer. Differentially expressed genes were detected in resistant small cell lung cancer H69AR cells and sensitive small cell lung cancer H69 cells by microarray. DLL1 expression in H69 cells and H69AR cells was further confirmed by RT-PCR and Western blot assay. eGFP-RNA was employed to up-regulate DDL1 expressing in H69AR cells (H69AR-eGFP-DLL1) by transfection. These cells were treated with different chemothera-peutics (ADM, DDP, and VP-16). Cell viability was detected. Cell cycle and apoptosis rate were determined. The DLL1 expression was significantly decreased in H69AR cells when compared with H69 cells. Over-expression of DLL1 increased the sensitivity of H69AR cells to chemotherapy, which was characterized by increase in apoptosis and arrest in G0/G1 phase. Our results demonstrate that up-regulation of DLL1 expression in small cell lung cancer cells may increase their sensitivity to chemotherapeutic agents.

Single-cell gene expression profiling reveals functional heterogeneity of undifferentiated human epidermal cells

Human epidermal stem cells express high levels of β1 integrins, delta-like 1 (DLL1) and the EGFR antagonist LRIG1. However, there is cell-to-cell variation in the relative abundance of DLL1 and LRIG1 mRNA transcripts. Single-cell global gene expression profiling showed that undifferentiated cells fell into two clusters delineated by expression of DLL1 and its binding partner syntenin. The DLL1+ cluster had elevated expression of genes associated with endocytosis, integrin-mediated adhesion and receptor tyrosine kinase signalling. Differentially expressed genes were not independently regulated, as overexpression of DLL1 alone or together with LRIG1 led to the upregulation of other genes in the DLL1+ cluster. Overexpression of DLL1 and LRIG1 resulted in enhanced extracellular matrix adhesion and increased caveolin-dependent EGFR endocytosis. Further characterisation of CD46, one of the genes upregulated in the DLL1+ cluster, revealed it to be a novel cell surface marker of human epidermal stem cells. Cells with high endogenous levels of CD46 expressed high levels of β1 integrin and DLL1 and were highly adhesive and clonogenic. Knockdown of CD46 decreased proliferative potential and β1 integrin-mediated adhesion. Thus, the previously unknown heterogeneity revealed by our studies results in differences in the interaction of undifferentiated basal keratinocytes with their environment.

MicroRNA-34a is a tumor suppressor in choriocarcinoma via regulation of Delta-like1

BackgroundChoriocarcinoma is a gestational trophoblastic tumor which causes high mortality if left untreated. MicroRNAs (miRNAs) are small non protein-coding RNAs which inhibit target gene expression. The role of miRNAs in choriocarcinoma, however, is not well understood. In this study, we examined the effect of miR-34a in choriocarcinoma.MethodsMiR-34a was either inhibited or ectopically expressed transiently in two choriocarcinoma cell lines (BeWo and JEG-3) respectively. Its actions on cell invasion, proliferation and colony formation at low cell density were examined. The miR-34a putative target Notch ligand Delta-like 1 (DLL1) was identified by adoption of different approaches including: in-silico analysis, functional luciferase assay and western blotting. Real-time quantitative polymerase chain reaction was used to quantify changes in the expression of matrix proteinase in the treated cells. To nullify the effect of miR-34a ectopic expression, we activated Notch signaling through force-expression of the Notch intracellular domain in the miR-34a force-expressed cells. In addition, we studied the importance of DLL1 in BeWo cell invasion through ligand stimulation and antibody inhibition. Furthermore, the induction in tumor formation of miR-34a-inhibited BeWo cells in SCID mice was investigated.ResultsTransient miR-34a force-expression significantly suppressed cell proliferation and invasion in BeWo and JEG-3 cells. In silicon miRNA target prediction, luciferase functional assays and Western blotting analysis demonstrated that miR-34a regulated DLL1 expression in both cell lines. Although force-expression of miR-34a suppressed the expression of DLL1 and NOTCH1, the extent of suppression was higher in DLL1 than NOTCH1 in both cell lines. MiR-34a-mediated DLL1 suppression led to reduced matrix metallopeptidase 9 and urokinase-type plasminogen activator expression. The effect of miR-34a on cell invasion was partially nullified by Notch signaling activation. DLL1 ligand stimulated while anti-DLL1 antibody treatment suppressed cell invasion. Mice inoculated with BeWo cells transfected with miR-34a inhibitor had significantly larger xenografts and stronger DLL1 expression than those with cells transfected with the control inhibitor.ConclusionsMiR-34a reduced cell proliferation and invasiveness, at least, partially through its inhibitory effect on DLL1.