T-cell acute lymphoblastic leukaemia (T-ALL) is a hematological malignancy caused by the accumulation of genomic lesions that affect the development of T-cells. ZEB1, a member of zinc finger-homeodomain family transcription factor, exhibits crucial function in promoting T-cell differentiation and potentially acts as a tumor suppressor in T-ALL. However, the molecular mechanism by which ZEB1 regulates T-ALL leukaemogenesis remains obscure. Here, we showed that oncogenic LIM only 2 (LMO2) could recruit Sap18 and HDAC1 to assemble an epigenetic regulatory complex, thus inducing histone deacetylation in ZEB1 promoter and chromatin remodeling to achieve transcriptional repression. Furthermore, downregulation of ZEB1 by LMO2 complex results in an increased leukaemia stem cell (LSC) phenotype as well as unsensitivity in response to methotrexate (MTX) chemotherapy in T-ALL cells. Importantly, we demonstrated that Trichostatin A (TSA, a HDAC inhibitor) addition significantly attenuates MTX unsensitivity caused by dysfunction of LMO2/ZEB1 signaling. In conclusion, these findings have identified a molecular mechanism underlying LMO2/ZEB1-mediated leukaemogenesis, paving a way for treating T-ALL with a new strategy of epigenetic inhibitors.

T cell acute lymphoblastic leukaemia (T-ALL) cases include subfamilies that overexpress the TAL1/LMO, TLX1/3 and HOXA transcription factor oncogenes. While it has been shown that TAL1/LMO transcription factors induce self-renewal of thymocytes, whether this is true for other transcription factor oncogenes is unknown. To address this, we have studied NUP98-HOXD13-transgenic (NHD13-Tg) mice, which overexpress HOXA transcription factors throughout haematopoiesis and develop both myelodysplastic syndrome (MDS) progressing to acute myeloid leukaemia (AML) as well as T-ALL. We find that thymocytes from preleukaemic NHD13-Tg mice can serially transplant, demonstrating that they have self-renewal capacity. Transcriptome analysis shows that NHD13-Tg thymocytes exhibit a stem cell-like transcriptional programme closely resembling that induced by Lmo2, including Lmo2 itself and its critical cofactor Lyl1. To determine whether Lmo2/Lyl1 are required for NHD13-induced thymocyte self-renewal, NHD13-Tg mice were crossed with Lyl1 knockout mice. This showed that Lyl1 is essential for expression of the stem cell-like gene expression programme in thymocytes and self-renewal. Surprisingly however, NHD13 transgenic mice lacking Lyl1 showed accelerated T-ALL and absence of transformation to AML, associated with a loss of multipotent progenitors in the bone marrow. Thus multiple T cell oncogenes induce thymocyte self-renewal via Lmo2/Lyl1; however, NHD13 can also promote T-ALL via an alternative pathway.

The development of a vascular network is essential to nourish tissues and sustain organ function throughout life. Endothelial cells (ECs) are the building blocks of blood vessels, yet our understanding of EC specification remains incomplete. Zebrafish cloche/npas4l mutants have been used broadly as an avascular model, but little is known about the molecular mechanisms of action of the Npas4l transcription factor. Here, to identify its direct and indirect target genes, we have combined complementary genome-wide approaches, including transcriptome analyses and chromatin immunoprecipitation. The cross-analysis of these datasets indicates that Npas4l functions as a master regulator by directly inducing a group of transcription factor genes that are crucial for hematoendothelial specification, such as etv2, tal1 and lmo2 We also identified new targets of Npas4l and investigated the function of a subset of them using the CRISPR/Cas9 technology. Phenotypic characterization of tspan18b mutants reveals a novel player in developmental angiogenesis, confirming the reliability of the datasets generated. Collectively, these data represent a useful resource for future studies aimed to better understand EC fate determination and vascular development.

Recent studies have showed that transcription elongation factors regulate early development. Foggy/Spt5 is a subunit of DRB sensitivity-inducing factor, which negatively and positively regulates transcription elongation. Here, we report that the positive function of Foggy/Spt5 is required for gata1 expression during zebrafish embryonic hematopoiesis. Antisense morpholino oligonucleotide (MO)-mediated knockdown of foggy/spt5 has led to a reduction in the expression of gata1 and the gata1 target genes alas2 and hbae3 and inhibited proper hemoglobin production. By contrast, expression of hematopoietic stem cell and endothelial markers, including scl, lmo2, gata2, fli-1, and flk-1, and expression of biklf, whose product directs gata1 expression via its direct binding to the gata1 promoter, were unaltered, suggesting that gata1 is a functionally important target gene of Foggy/Spt5. The MO-mediated gata1 repression was relieved by forced expression of wild-type foggy/spt5, but not by a mutant lacking the positive function. Therefore, this study provides evidence that Foggy/Spt5 plays an important role in gata1 gene expression and erythropoiesis through its transcriptional activation domain.

Deficiency in DNA double-strand break (DSB) repair mechanisms has been widely exploited for the treatment of different malignances, including homologous recombination (HR)-deficient breast and ovarian cancers. Here we demonstrate that diffuse large B cell lymphomas (DLBCLs) expressing LMO2 protein are functionally deficient in HR-mediated DSB repair. Mechanistically, LMO2 inhibits BRCA1 recruitment to DSBs by interacting with 53BP1 during repair. Similar to BRCA1-deficient cells, LMO2-positive DLBCLs and T cell acute lymphoblastic leukemia (T-ALL) cells exhibit a high sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. Furthermore, chemotherapy and PARP inhibitors synergize to inhibit the growth of LMO2-positive tumors. Together, our results reveal that LMO2 expression predicts HR deficiency and the potential therapeutic use of PARP inhibitors in DLBCL and T-ALL.

Lmo (LIM-domain-only)2 transcription factor is involved in hematopoiesis and vascular remodeling. Sphk (sphingosine kinase)1 phosphorylates sphingosine to S1P (sphingosine-1-phosphate). We hypothesized that Lmo2 regulates Sphk1 to promote endothelial cell (EC) migration and vascular development. APPROACH AND RESULTS: Lmo2 and Sphk1 knockdown (KD) were performed in Tg(fli1:EGFP) y1 zebrafish and in human umbilical vein EC. Rescue of phenotypes or overexpression of these factors were achieved using mRNA encoding Lmo2 or Sphk1. EC proliferation in vivo was assessed by BrdU (bromodeoxyuridine) immunostaining and fluorescence-activated cell sorter analysis of dissociated Tg(fli1:EGFP) y1 embryos. Cell migration was assessed by scratch assay in human umbilical vein EC and mouse aortic rings. Lmo2 interactions with Sphk1 promoter were assessed by ChIP-PCR (chromatin immunoprecipitation-polymerase chain reaction). Lmo2 or Sphk1 KD reduced number and length of intersegmental vessels. There was no reduction in the numbers of GFP+ (green fluorescent protein) ECs after Lmo2 KD. However, reduced numbers of BrdU+GFP+ nuclei were observed along the dysmorphic intersegmental vessels, accumulating instead at the sprouting origin of the intersegmental vessels. This anomaly was likely because of impaired EC migration, which was confirmed in migration assays using Lmo2 KD human umbilical vein ECs and mouse aortic rings. Both in vivo and in vitro, Lmo2 KD reduced Sphk1 gene expression, associated with less Lmo2 binding to the Sphk1 promoter as assessed by ChIP-PCR. Sphk1 mRNA rescued the Lmo2 KD phenotype.

Our data showed that Lmo2 is necessary for Sphk1 gene expression in ECs. Lmo2 KD reduced Lmo2-Sphk1 gene interaction, impaired intersegmental vessels formation, and reduced cell migration. We identified for the first time Sphk1 as downstream effector of Lmo2.

Gene expression profiling studies have distinguished diffuse large B-cell lymphomas (DLBCLs) by cell of origin, with distinct pathogenetic mechanisms and prognosis. We attempted to identify DLBCL molecular subtypes in an epidemiologic study of 214 DLBCL patients diagnosed during 1998-2000 with archival tissues to investigate etiology. Immunohistochemical staining for CD10, BCL6, LMO2, MUM1/IRF4, and BCL2 and fluorescence in situ hybridization for t(14;18) were conducted, with ≥93% blinded duplicate agreement. CD10, LMO2, and BCL2 expression was similar to previous reports (32%, 44%, and 44% of DLBCLs, respectively), but BCL6 and MUM1/IRF4 expression was lower than expected (29% and 5%, respectively). We classified 112/214 (52%) cases as germinal center B-cell-like DLBCL (GCB-DLBCL; Hans et al., Blood 2004; CD10+ or CD10-/BCL6+/MUM1-), with no difference in prognosis compared with non-GCB-DLBCL (Cox regression, P=0.48). Comparing other GCB correlates, LMO2 expression and t(14;18) were more common but not exclusive to GCB-DLBCL as defined in our study, whereas BCL2 expression did not differ between DLBCL molecular subtypes. We could not confidently identify patients with GCB-DLBCL using these immunohistochemistry-based markers on archival tissues.

Diffuse large B-cell lymphoma (DLBCL) can be separated for prognostic purposes using gene expression profiling (GEP) into 2 subgroups: germinal center B-cell (GCB) and activated B-cell phenotypes. However, GEP is impractical for routine clinical use, and immunophenotyping is an imperfect surrogate. Therefore, we studied the relationship between expression of the purported germinal center marker LMO2 and the presence of IGH-BCL2 fusions, BCL6 translocations, and LMO2 translocations. In addition, we investigated the usefulness of LMO2 expression as a marker of GCB subtype in DLBCL. Immunohistochemical and fluorescence in situ hybridization studies were successfully performed on 101 cases of de novo DLBCL that had been incorporated into a tissue microarray. There was a statistically significant association between IGH-BCL2 fusion and LMO2 protein expression (P = .02) but not between BCL6 translocations and LMO2 expression. LMO2 translocations were not identified. Although uncommon, all cases that had both IGH-BCL2 fusion and BCL6 translocations expressed LMO2. The findings suggest LMO2 as a potential marker for the GCB phenotype.

Angiogenesis, the formation of new blood vessels out of pre-existing capillaries, occurs in a variety of pathophysiological conditions, and is regulated by a balance of angiogenic activators and inhibitors. To identify novel angiogenic factors, we developed a gene screening method by combining the prediction analysis of transcription factor (TF) binding site and the chromosomal localization analysis. First, we analyzed the promoter sequences from known angiogenesis-related factors using the MATINSPECTOR program in TRANSFAC database. Interestingly, we found that the binding site of LMO2 complex is highly conserved in the promoter regions of these factors. Second, we analyzed chromosome loci based on the hypothesis that angiogenesis-related factors might be co-localized in a specific chromosomal band. We found that angiogenesis-related factors are localized in specific 14 chromosomal bands including 5q31 and 19q13 using AngioDB and LocusLink database mining. From these two approaches, we identified 32 novel candidates that have the LMO2 complex binding site in their promoter and are located on one of 14 chromosomal bands. Among them, human recombinant troponin T and spectrin markedly inhibited the neovascularization in vivo and in vitro. Collectively, we suggest that the combination of the prediction analysis of TF binding site and the chromosomal localization analysis might be a useful strategy for gene screening of angiogenesis.

OBJECTIVE

To examine the immunoarchitectural patterns of the germinal center (GC)-associated markers CD10, BCL6, and LMO2 and their utility in the differential diagnosis of marginal zone lymphoma (MZL) vs follicular lymphoma (FL).

METHODS

Forty-two cases of MZL involving lymph nodes and 88 cases of FL were examined.

RESULTS

Interfollicular staining for GC markers was uncommon in MZL but common in FL, including BCL2-positive and BCL2-negative cases. Two atypical patterns of intrafollicular GC staining were identified that were more common in MZL than in FL.

CONCLUSIONS

Staining for LMO2 in addition to CD10 and BCL6 facilitates the detection of a GC phenotype in FL. Lymph nodes involved by MZL frequently show characteristic alterations of GC immunoarchitecture. Recognizing these altered patterns assists in the distinction between MZL and FL.

Understanding the regulatory mechanism that controls the alteration of global gene expression patterns continues to be a challenging task in computational biology. We previously developed an ant algorithm, a biologically-inspired computational technique for microarray data, and predicted putative transcription-factor binding motifs (TFBMs) through mimicking interactive behaviors of natural ants. Here we extended the algorithm into a set of web-based software, Ant Modeler, and applied it to investigate the transcriptional mechanism underlying bone formation. Mechanical loading and administration of bone morphogenic proteins (BMPs) are two known treatments to strengthen bone. We addressed a question: Is there any TFBM that stimulates both "anabolic responses of mechanical loading" and "BMP-mediated osteogenic signaling"? Although there is no significant overlap among genes in the two responses, a comparative model-based analysis suggests that the two independent osteogenic processes employ common TFBMs, such as a stress responsive element and a motif for peroxisome proliferator-activated receptor (PPAR). The post-modeling in vitro analysis using mouse osteoblast cells supported involvements of the predicted TFBMs such as PPAR, Ikaros 3, and LMO2 in response to mechanical loading. Taken together, the results would be useful to derive a set of testable hypotheses and examine the role of specific regulators in complex transcriptional control of bone formation.

Lmo2 is a LIM-only protein involved in hematopoiesis and the development of T-cell acute lymphoblastic leukaemia. Here we report backbone and side chain NMR assignments for an engineered intramolecular complex of the C-terminal LIM domain from Lmo2 tethered to the LIM interaction domain (LID) from LIM domain binding protein 1 (Ldb1).

LIM domain only-2 (LMO2) overexpression in T cells induces leukemia but the molecular mechanism remains to be elucidated. In hematopoietic stem and progenitor cells, Lmo2 is part of a protein complex comprised of class II basic helix loop helix proteins, Tal1and Lyl1. The latter transcription factors heterodimerize with E2A proteins like E47 and Heb to bind E boxes. LMO2 and TAL1 or LYL1 cooperate to induce T-ALL in mouse models, and are concordantly expressed in human T-ALL. Furthermore, LMO2 cooperates with the loss of E2A suggesting that LMO2 functions by creating a deficiency of E2A. In this study, we tested this hypothesis in Lmo2-induced T-ALL cell lines. We transduced these lines with an E47/estrogen receptor fusion construct that could be forced to homodimerize with 4-hydroxytamoxifen. We discovered that forced homodimerization induced growth arrest in 2 of the 4 lines tested. The lines sensitive to E47 homodimerization accumulated in G1 and had reduced S phase entry. We analyzed the transcriptome of a resistant and a sensitive line to discern the E47 targets responsible for the cellular effects. Our results suggest that E47 has diverse effects in T-ALL but that functional deficiency of E47 is not a universal feature of Lmo2-induced T-ALL.

OBJECTIVE

T-cell acute lymphoblastic leukemia (T-ALL) is associated with recurrent chromosomal aberrations andabnormal ectopic gene expression during T-cell development. In order to gain insight into the pathogenesis of T-ALLthis study aimed to measure the level of expression of 7 T-cell oncogenes (LMO2, LYL1, TAL1, TLX1, TLX3, BMI1, andCALM-AF10) in pediatric T-ALL patients Material and Methods: LMO2, LYL1, TLX1, TLX3, BMI1, TAL1, and CALM-AF10 expression was measured usingquantitative real-time PCR in 43 pediatric T-ALL patients.

RESULTS

A high level of expression of LMO2, LYL1, TAL1, and BMI1 genes was observed in a large group of T-ALL.Several gene expression signatures indicative of leukemic arrest at specific stages of normal thymocyte development(LYL1 and LMO2) were highly expressed during the cortical and mature stages of T-cell development. Furthermore,upregulated TAL1 and BMI1 expression was observed in all phenotypic subgroups. In all, 6 of the patients had TLX1and TLX3 proto-oncogene expression, which does not occur in normal cells, and none of the patients had CALM-AF10fusion gene transcription. Expression of LYL1 alone and LMO2-LYL1 co-expression were associated with mediastinalinvolvement; however, high-level oncogene expression was not predictive of outcome in the present pediatric T-ALLpatient group, but there was a trend towards a poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 protooncogeneexpression.

CONCLUSIONS

Poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 proto-oncogene expression indicate the needfor extensive study on oncogenic rearrangement and immunophenotypic markers in T-ALL, and their relationship totreatment outcome.

BACKGROUND

None declared.

The VIDAS Listeria monocytogenes II (LMO2) method, which is an automated enzyme-linked fluorescent immunoassay (ELFA), was used for rapidly, specifically and sensitively detecting L. monocytogenes in food samples. All 31 L. monocytogenes strains examined gave positive results. The other bacterial species except Salmonella showed completely negative results, but it was suspected that Salmonella spp. had given a false-positive reaction to the assay. As the detectable limit of the assay was 10⁶ cfu/ml in a food suspension, food samples were required to be enriched in order to increase the number of the bacteria to the detectable limit. However, the ELFA was reconfirmed to be applied satisfactorily as a rapid and precise method for the detection of L. monocytogenes in various food samples, even if the culture had to be enriched for 12 h prior to the assay.

Translocations resulting in ectopic expression of the TLX1 homeobox gene (previously known as HOX11) are recurrent events in human T-cell acute lymphoblastic leukemia (T-ALL). Transduction of primary murine hematopoietic stem/progenitor cells with retroviral vectors expressing TLX1 readily yields immortalized hematopoietic progenitor cell lines. Understanding the processes involved in TLX1-mediated cellular immortalization should yield insights into the growth and differentiation pathways altered by TLX1 during the development of T-ALL. In recent clinical gene therapy trials, hematopoietic clonal dominance or T-ALL-like diseases have occurred as a direct consequence of insertional activation of the EVI1, PRDM16 or LMO2 proto-oncogenes by the retroviral vectors used to deliver the therapeutic genes. Additionally, the generation of murine hematopoietic progenitor cell lines due to retroviral integrations into Evi1 or Prdm16 has also been recently reported. Here, we determined by linker-mediated nested polymerase chain reaction the integration sites in eight TLX1-immortalized hematopoietic cell lines. Notably, no common integration site was observed among the cell lines. Moreover, no insertions into the Evi1 or Prdm16 genes were identified although insertion near Lmo2 was observed in one instance. However, neither Lmo2 nor any of the other genes examined surrounding the integration sites showed differential vector-influenced expression compared to the cell lines lacking such insertions. While we cannot exclude the possibility that insertional side effects transiently provided a selective growth/survival advantage to the hematopoietic progenitor populations, our results unequivocally rule out insertions into Evi1 and Prdm16 as being integral to the TLX1-initiated immortalization process.

OBJECTIVE

Notch expression is not yet determined in hepatoblastoma. In this study the effect of chemotherapeutics (cisplatin, doxorubicin, cytosin arabinoside); differentiating agent (13 cis-retinoic acid) and apoptotic agents (5-aza-2'-deoxycytidine, arsenic trioxide) on notch expression in hepatoblastoma were evaluated.

METHODS

After HepG2 cell line was cultured and the agents and their combinations were applied for 24 hour in pre-optimized 50% lethal doses, RNA isolation and cDNA converting, expression of 84 custom array genes of notch signaling pathway (SABiosciences, PAT059F-24) was determined by Real Time PCR. The methylation status of 6 genes that showed more than 5 fold changes compared with control group were explored by Methylation qPCR Assay. High expressed genes are HDAC1, NFKB1, CHUK, CDKN1A, and CBL. Low expressed genes are DLL1, CD44, FZD2, GLI1, IL17B, LMO2, NOTCH1, LOR, PAX5, PT-CRA, SH2D1A, and WISP1. The genes searched for methylation (DLL1, HEY1, DTX1, HDAC1, NOTCH2 and JAG1) were not found to be related with methylation.

RESULTS

The high expressed genes are related with cell proliferation. The main signaling genes that are closed to notch in signaling pathway are low expressed in hepatoblastoma. The agents do not show prominent effect of gene expression in many genes and methylation is not the reason of expression changes. The use of retinoic acid in the control of minimal residual disease of hepatoblastoma should be discussed. 5 aza "cytidin" the demethylating agent is not advised in treatment according to our results.

CONCLUSIONS

Cisplatin as main chemotherapeutic agent treatment is shown to change gene expression levels in notch signalling pathway in hepatoblastoma.

Recent advances in single-cell transcriptomics techniques have opened the door to the study of gene regulatory networks (GRNs) at the single-cell level. Here, we studied the GRNs controlling the emergence of hematopoietic stem and progenitor cells from mouse embryonic endothelium using a combination of single-cell transcriptome assays. We found that a heptad of transcription factors (Runx1, Gata2, Tal1, Fli1, Lyl1, Erg and Lmo2) is specifically co-expressed in an intermediate population expressing both endothelial and hematopoietic markers. Within the heptad, we identified two sets of factors of opposing functions: one (Erg/Fli1) promoting the endothelial cell fate, the other (Runx1/Gata2) promoting the hematopoietic fate. Surprisingly, our data suggest that even though Fli1 initially supports the endothelial cell fate, it acquires a pro-hematopoietic role when co-expressed with Runx1. This work demonstrates the power of single-cell RNA-sequencing for characterizing complex transcription factor dynamics.

Thrombopoietin (TPO) is the principal regulator of thrombopoiesis and promotes the proliferation, differentiation and maturation of megakaryocytic progenitor cells in mammals. In this study we report on the molecular and functional characterization of goldfish TPO. Quantitative expression analysis of goldfish tpo revealed the highest mRNA levels in heart, followed by spleen, liver, brain, intestine and kidney tissues. Significant decrease of tpo and c-mpl expressions in goldfish primary kidney macrophage (PKM) cultures, as progenitor to macrophage development progressed, indicates that TPO is not involved in monopoiesis. Recombinant goldfish TPO (rgTPO) alone did not induce significant proliferation of progenitor cells, but TPO in cooperation with recombinant goldfish kit ligand A (rgKITLA) supported proliferation of progenitor cells in a dose-dependent manner. In response to rgTPO or a combination of rgTPO and rgKITLA, the mRNA levels of thrombopoietic markers cd41 and c-mpl as well as thrombo/erythropoietic transcription factors gata1 and lmo2 in sorted progenitor cells were up-regulated, while the mRNA levels of granulopoietic markers (cebpα and gcsfr) and the lymphoid transcription factor gata3 were down-regulated. Furthermore, rgTPO and rgKITLA synergistically stimulated thrombocytic colony-formation. Our results demonstrate that goldfish TPO has similar functions to mammalian TPO as a regulator of thrombopoiesis, and suggests a highly conserved molecular mechanism of thrombocyte development throughout evolution of vertebrates.

BACKGROUND

The aberrant activation of Ras signaling is associated with human diseases including hematological malignancies and vascular disorders. So far the pathological roles of activated Ras signaling in hematopoiesis and vasculogenesis are largely unknown.

METHODS

A conditional Cre/loxP transgenic strategy was used to mediate the specific expression of a constitutively active form of human N-Ras in zebrafish endothelial and hematopoietic cells driven by the zebrafish lmo2 promoter. The expression of hematopoietic and endothelial marker genes was analyzed both via whole mount in situ hybridization (WISH) assay and real-time quantitative PCR (qPCR). The embryonic vascular morphogenesis was characterized both by living imaging and immunofluorescence on the sections with a confocal microscopy, and the number of endothelial cells in the embryos was quantified by flow cytometry. The functional analyses of the blood circulation were carried out by fluorescence microangiography assay and morpholino injection.

RESULTS

In the activated N-Ras transgenic embryos, the primitive hematopoiesis appeared normal, however, the definitive hematopoiesis of these embryos was completely absent. Further analysis of endothelial cell markers confirmed that transcription of arterial marker ephrinB2 was significantly decreased and expression of venous marker flt4 excessively increased, indicating the activated N-Ras signaling promotes the venous development at the expense of arteriogenesis during zebrafish embryogenesis. The activated N-Ras-expressing embryos showed atrophic axial arteries and expansive axial veins, leading to no definitive hematopoietic stem cell formation, the blood circulation failure and subsequently embryonic lethality.

CONCLUSIONS

Our studies revealed for the first time that activated N-Ras signaling during the endothelial differentiation in vertebrates can disrupt the balance of arterial-venous specification, thus providing new insights into the pathogenesis of the congenital human vascular disease and tumorigenic angiogenesis.

BACKGROUND

GATA-2 is a transcription factor required for hematopoietic stem cell survival as well as for neuronal development in vertebrates. It has been shown that specific expression of GATA-2 in blood progenitor cells requires distal cis-acting regulatory elements. Identification and characterization of these elements should help elucidating transcription regulatory mechanisms of GATA-2 expression in hematopoietic lineage.

RESULTS

By pair-wise alignments of the zebrafish genomic sequences flanking GATA-2 to orthologous regions of fugu, mouse, rat and human genomes, we identified three highly conserved non-coding sequences in the genomic region flanking GATA-2, two upstream of GATA-2 and another downstream. Using both transposon and bacterial artificial chromosome mediated germline transgenic zebrafish analyses, one of the sequences was established as necessary and sufficient to direct hematopoietic GFP expression in a manner that recapitulates that of GATA-2. In addition, we demonstrated that this element has enhancer activity in mammalian myeloid leukemia cell lines, thus validating its functional conservation among vertebrate species. Further analysis of potential transcription factor binding sites suggested that integrity of the putative HOXA3 and LMO2 sites is required for regulating GATA-2/GFP hematopoietic expression.

CONCLUSIONS

Regulation of GATA-2 expression in hematopoietic cells is likely conserved among vertebrate animals. The integrated approach described here, drawing on embryological, transgenesis and computational methods, should be generally applicable to analyze tissue-specific gene regulation involving distal DNA cis-acting elements.

OBJECTIVE

Littoral cell angioma (LCA) is a rare primary splenic tumour that is frequently associated with internal malignancies. Immunohistochemistry can demonstrate a distinct hybrid endothelial-histiocytic phenotype of littoral cells, and is a helpful adjunct for making the correct diagnosis. The aims of this study were to present a series of 25 LCAs, with an emphasis on the frequent association of the neoplasm with visceral malignancies, and to provide a detailed immunohistochemical analysis by employing new markers.

RESULTS

All 25 cases with available tissue blocks were immunohistochemically stained for endothelial and histiocytic markers. Clinical and follow-up data were retrieved from the respective institutions. The tumours were obtained from 16 males and nine females, whose age ranged from 32 to 86 years (mean 56.2 years). Clinical information was available for 24 of 25 patients, and follow-up for 11 of 25 patients (range 2-19 years; mean 11.6 years). Immunohistochemically, all cases were positive for LYVE-1, factor VIII, FLI-1, vascular endothelial growth factor receptor (VEGFR)-2, VEGFR-3, claudin-5, ERG, LMO2, CD31, CD163, lysozyme, and CD4, but negative for D2-40, CD8, and factor XIIIa. Fifteen of 25 cases were associated with various malignancies, including epithelial, mesenchymal and haematological tumours.

CONCLUSIONS

The cohort of 25 patients is the largest series of LCAs published to date. By using antibodies against recently introduced endothelial markers, we have expanded the immunoprofile of LCA. We have further highlighted the clinical significance of LCA, as more than half of the patients in this study also harboured a coexisting visceral malignancy. Therefore, we conclude that the finding of splenic LCA mandates a thorough clinical evaluation for a concomitant malignancy.

BACKGROUND

Angiogenesis occurs commonly in various physiological and pathological processes. Improving blood supply through promoting angiogenesis is a novel approach for treating ischemic diseases. Angiotensin II type 1 receptor blockers (ARBs) dominate the management of hypertension, but evidence of their role in angiogenesis is contradictory. Here we explored the angiogenic effects of ARBs through characterizing gene expression of the human umbilical vein endothelial cell line EA.hy926 exposed to irbesartan.

METHODS

The human umbilical vein endothelial cell line EA.hy926 was grown for 72 hours after treatment with different concentrations of irbesartan. The cell proliferative capacity was assessed by CCK8 assay at 24, 48 and 72 hours. Gene expression levels in EA.hy926 cells responding to irbesartan were measured under optimal proliferation conditions by microarray analysis using Affymetrix U133 plus 2.0. The differential expression of genes involved in angiogenesis was identified through cluster analysis of the resulting microarray data. Quantitative RT-PCR and Western blotting analyses were used to validate differential gene expression related to the angiogenesis process.

RESULTS

In the 10(-4), 10(-5), 10(-6) mol/L treatment groups, cell proliferation studies revealed significantly increased proliferation in EA.hy926 cells after 24 hours of irbesartan treatment. However, after 48 and 72 hours of treatment with different concentrations of irbesartan, there was no significant difference in cell proliferation observed in any treatment group. We selected the group stimulated with irbersartan at a concentration of 10(-6) mol/L for microarray experiments. Statistical analysis of the microarray data resulted in the identification of 56 gene transcripts whose expression patterns were significantly correlated, negatively or positively, with irbesartan treatment. Cluster analysis showed that these genes were involved in angiogenesis, extracellular stimulus, binding reactions and skeletal system morphogenesis. Of these 56 genes we identified seven genes (VEGF, KDR, PTGS2, PLXND1, ROBO4, LMO2, and COL5A1) involved in the angiogenesis process. qRT-PCR analysis of these genes confirmed the microarray results. Protein expression of three VEGF pathway genes (VEGF, KDR, and PTGS2) was further confirmed by Western blotting.

CONCLUSIONS

Our study showed that irbesartan may induce angiogenic effects in vascular endothelial cells. It suggested that the mechanism of angiogenic effects of ARBs might be attributed to the signaling cascade from angiotensin receptors in the VEGF pathway. It also provided evidence indicating that ARBs could be used as a novel therapeutic approach to treat chronic ischemic heart disease as well as anti-hypertensive agents.