LYL1

Gene Summary

Gene:LYL1; LYL1, basic helix-loop-helix family member
Aliases: bHLHa18
Location:19p13.13
Summary:This gene represents a basic helix-loop-helix transcription factor. The encoded protein may play roles in blood vessel maturation and hematopoeisis. A translocation between this locus and the T cell receptor beta locus (GeneID 6957) on chromosome 7 has been associated with acute lymphoblastic leukemia. [provided by RefSeq, Sep 2010]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:protein lyl-1
Source:NCBIAccessed: 11 March, 2017

Ontology:

What does this gene/protein do?
Show (10)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Gene Expression Profiling
  • T-Cell Leukemia
  • Oncogenes
  • Young Adult
  • Acute Lymphocytic Leukaemia
  • Cell Differentiation
  • Neoplastic Cell Transformation
  • Protein Binding
  • Adult T-Cell Leukemia-Lymphoma
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma
  • Metalloproteins
  • Cancer Gene Expression Regulation
  • DNA-Binding Proteins
  • Gene Rearrangement
  • Helix-Loop-Helix Motifs
  • Signal Transducing Adaptor Proteins
  • Transcription
  • LIM Domain Proteins
  • Neoplasm Proteins
  • Homeodomain Proteins
  • Adolescents
  • Proto-Oncogene Proteins
  • RTPCR
  • Base Sequence
  • Molecular Sequence Data
  • Childhood Cancer
  • Signal Transduction
  • TRB
  • Acute Myeloid Leukaemia
  • Up-Regulation
  • Cell Proliferation
  • Thymocytes
  • Promoter Regions
  • K562 Cells
  • RNA Interference
  • Transcription Factor 3
  • Leukemic Gene Expression Regulation
  • Basic Helix-Loop-Helix Transcription Factors
  • Tumor Suppressor Proteins
  • Transcription Factors
  • Chromosome 19
  • Mice, Transgenic
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (1)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
Acute Lymphocytic Leukaemia (ALL)t(7;19)(q35;p13) in T-cell Acute Lymphoblastic Leukemia

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: LYL1 (cancer-related)

Sotoca AM, Prange KH, Reijnders B, et al.
The oncofusion protein FUS-ERG targets key hematopoietic regulators and modulates the all-trans retinoic acid signaling pathway in t(16;21) acute myeloid leukemia.
Oncogene. 2016; 35(15):1965-76 [PubMed] Free Access to Full Article Related Publications
The ETS transcription factor ERG has been implicated as a major regulator of both normal and aberrant hematopoiesis. In acute myeloid leukemias harboring t(16;21), ERG function is deregulated due to a fusion with FUS/TLS resulting in the expression of a FUS-ERG oncofusion protein. How this oncofusion protein deregulates the normal ERG transcription program is unclear. Here, we show that FUS-ERG acts in the context of a heptad of proteins (ERG, FLI1, GATA2, LYL1, LMO2, RUNX1 and TAL1) central to proper expression of genes involved in maintaining a stem cell hematopoietic phenotype. Moreover, in t(16;21) FUS-ERG co-occupies genomic regions bound by the nuclear receptor heterodimer RXR:RARA inhibiting target gene expression and interfering with hematopoietic differentiation. All-trans retinoic acid treatment of t(16;21) cells as well as FUS-ERG knockdown alleviate the myeloid-differentiation block. Together, the results suggest that FUS-ERG acts as a transcriptional repressor of the retinoic acid signaling pathway.

Dirse V, Bertasiute A, Gineikiene E, et al.
A population-based single nucleotide polymorphism array analysis of genomic aberrations in younger adult acute lymphoblastic leukemia patients.
Genes Chromosomes Cancer. 2015; 54(5):326-33 [PubMed] Related Publications
Adult acute lymphoblastic leukemia (ALL) is characterized by a high frequency of abnormal karyotypes some of which are related to outcome. Single nucleotide polymorphism (SNP) array analysis provides a highly sensitive platform to detect large and small genomic aberrations. SNP array profiling data in adult ALL are limited and further systematic studies of this patient group are needed. We performed a population-based SNP array analysis of genomic aberrations and their influence on survival in 66 Lithuanian 18-65 year old ALL patients diagnosed between 2007 and 2013. Most aberrations were detected in chromosome arm 9p, chromosome arm 6q, chromosome arm 13q, and chromosome 17. The recurrently targeted copy number abnormalities involved several leukemia-related genes-CDKN2A/B, MLL, IKZF1, PAX5, RB1, TP53, and ETV6. We identified several new recurrent aberrations with possible new target genes: SMARCA4 in 19p13.2, RNASEL in 1q25.3, ARHGEF12 in 11q23.3, and LYL1 in 19p13.2. Aberrations in chromosome 13 and the RB1 gene as well as CDKN2A/B gene status were related to the outcome.

Bruserud Ø, Reikvam H, Fredly H, et al.
Expression of the potential therapeutic target CXXC5 in primary acute myeloid leukemia cells - high expression is associated with adverse prognosis as well as altered intracellular signaling and transcriptional regulation.
Oncotarget. 2015; 6(5):2794-811 [PubMed] Free Access to Full Article Related Publications
The CXXC5 gene encodes a transcriptional activator with a zinc-finger domain, and high expression in human acute myeloid leukemia (AML) cells is associated with adverse prognosis. We now characterized the biological context of CXXC5 expression in primary human AML cells. The global gene expression profile of AML cells derived from 48 consecutive patients was analyzed; cells with high and low CXXC5 expression then showed major differences with regard to extracellular communication and intracellular signaling. We observed significant differences in the phosphorylation status of several intracellular signaling mediators (CREB, PDK1, SRC, STAT1, p38, STAT3, rpS6) that are important for PI3K-Akt-mTOR signaling and/or transcriptional regulation. High CXXC5 expression was also associated with high mRNA expression of several stem cell-associated transcriptional regulators, the strongest associations being with WT1, GATA2, RUNX1, LYL1, DNMT3, SPI1, and MYB. Finally, CXXC5 knockdown in human AML cell lines caused significantly increased expression of the potential tumor suppressor gene TSC22 and genes encoding the growth factor receptor KIT, the cytokine Angiopoietin 1 and the selenium-containing glycoprotein Selenoprotein P. Thus, high CXXC5 expression seems to affect several steps in human leukemogenesis, including intracellular events as well as extracellular communication.

Goodings C, Tripathi R, Cleveland SM, et al.
Enforced expression of E47 has differential effects on Lmo2-induced T-cell leukemias.
Leuk Res. 2015; 39(1):100-9 [PubMed] Free Access to Full Article Related Publications
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.

Smith S, Tripathi R, Goodings C, et al.
LIM domain only-2 (LMO2) induces T-cell leukemia by two distinct pathways.
PLoS One. 2014; 9(1):e85883 [PubMed] Free Access to Full Article Related Publications
The LMO2 oncogene is deregulated in the majority of human T-cell leukemia cases and in most gene therapy-induced T-cell leukemias. We made transgenic mice with enforced expression of Lmo2 in T-cells by the CD2 promoter/enhancer. These transgenic mice developed highly penetrant T-ALL by two distinct patterns of gene expression: one in which there was concordant activation of Lyl1, Hhex, and Mycn or alternatively, with Notch1 target gene activation. Most strikingly, this gene expression clustering was conserved in human Early T-cell Precursor ALL (ETP-ALL), where LMO2, HHEX, LYL1, and MYCN were most highly expressed. We discovered that HHEX is a direct transcriptional target of LMO2 consistent with its concordant gene expression. Furthermore, conditional inactivation of Hhex in CD2-Lmo2 transgenic mice markedly attenuated T-ALL development, demonstrating that Hhex is a crucial mediator of Lmo2's oncogenic function. The CD2-Lmo2 transgenic mice offer mechanistic insight into concordant oncogene expression and provide a model for the highly treatment-resistant ETP-ALL subtype.

McCormack MP, Shields BJ, Jackson JT, et al.
Requirement for Lyl1 in a model of Lmo2-driven early T-cell precursor ALL.
Blood. 2013; 122(12):2093-103 [PubMed] Related Publications
Lmo2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute lymphoblastic leukemia (T-ALL), including early T-cell precursor ALL (ETP-ALL) cases with poor prognosis. Lmo2 must be recruited to DNA by binding to the hematopoietic basic helix-loop-helix factors Scl/Tal1 or Lyl1. However, it is unknown which of these factors can mediate the leukemic activity of Lmo2. To address this, we have generated Lmo2-transgenic mice lacking either Scl or Lyl1 in the thymus. We show that although Scl is dispensable for Lmo2-driven leukemia, Lyl1 is critical for all oncogenic functions of Lmo2, including upregulation of a stem cell-like gene signature, aberrant self-renewal of thymocytes, and subsequent generation of T-cell leukemia. Lyl1 expression is restricted to preleukemic and leukemic stem cell populations in this model, providing a molecular explanation for the stage-specific expression of the Lmo2-induced gene expression program. Moreover, LMO2 and LYL1 are coexpressed in ETP-ALL patient samples, and LYL1 is required for growth of ETP-ALL cell lines. Thus, the LMO2-LYL1 interaction is a promising therapeutic target for inhibiting self-renewing cancer stem cells in T-ALL, including poor-prognosis ETP-ALL cases.

Diffner E, Beck D, Gudgin E, et al.
Activity of a heptad of transcription factors is associated with stem cell programs and clinical outcome in acute myeloid leukemia.
Blood. 2013; 121(12):2289-300 [PubMed] Related Publications
Aberrant transcriptional programs in combination with abnormal proliferative signaling drive leukemic transformation. These programs operate in normal hematopoiesis where they are involved in hematopoietic stem cell (HSC) proliferation and maintenance. Ets Related Gene (ERG) is a component of normal and leukemic stem cell signatures and high ERG expression is a risk factor for poor prognosis in acute myeloid leukemia (AML). However, mechanisms that underlie ERG expression in AML and how its expression relates to leukemic stemness are unknown. We report that ERG expression in AML is associated with activity of the ERG promoters and +85 stem cell enhancer and a heptad of transcription factors that combinatorially regulate genes in HSCs. Gene expression signatures derived from ERG promoter-stem cell enhancer and heptad activity are associated with clinical outcome when ERG expression alone fails. We also show that the heptad signature is associated with AMLs that lack somatic mutations in NPM1 and confers an adverse prognosis when associated with FLT3 mutations. Taken together, these results suggest that transcriptional regulators cooperate to establish or maintain primitive stem cell-like signatures in leukemic cells and that the underlying pattern of somatic mutations contributes to the development of these signatures and modulate their influence on clinical outcome.

San-Marina S, Han Y, Liu J, Minden MD
Suspected leukemia oncoproteins CREB1 and LYL1 regulate Op18/STMN1 expression.
Biochim Biophys Acta. 2012 Nov-Dec; 1819(11-12):1164-72 [PubMed] Related Publications
Stathmin (STMN1) is a microtubule destabilizing protein with a key role in cell cycle progression and cell migration that is up-regulated in several cancers and may contribute to the malignant phenotype. However, the factors that regulate its expression are not well understood. Loss as well as gain-of-function p53 mutations up-regulate STMN1 and in acute myelogenous leukemia where p53 is predominantly wild-type, STMN1 is also over-expressed. Here we show regulatory control of STMN1 expression by the leucine zipper transcription factor (TF) CREB1 and the basic helix-loop-helix TF LYL1. By ChIP-chip experiments we demonstrate in vivo the presence of LYL1 and CREB1 in close proximity on the STMN1 promoter and using promoter assays we reveal co-regulation of STMN1 by CREB1 and LYL1. By contrast, TAL1, another suspected oncoprotein in leukemia and close relative of LYL1, exerts no regulatory effect on the STMN1 promoter. NLI, LMO2 and GATA2 are previously described co-activators of Tal1/Lyl1-E47 transcriptional complexes and potentiate Lyl1 activation of the STMN1 promoter while having no effect on TAL1 transactivation. Promoter mutations that abrogate CREB1 proximal binding or mutations of the DNA-binding domain of CREB1 abolish LYL1 transcriptional activation. These results show that CRE and Ebox sites function as coordinated units and support previous evidence of joint CREB1-and LYL1 transcription events activating an aberrant subset of promoters in leukemia. CREB1 or LYL1 shRNA knock-down down-regulate STMN1 expression. Because down-regulation of STMN1 has been shown to have anti-proliferative effects, while CREB1 and LYL1 are suspected oncoproteins, interference with CREB1-LYL1 interactions may complement standard chemotherapy and yield additional beneficial effects.

Nagel S, Ehrentraut S, Tomasch J, et al.
Transcriptional activation of prostate specific homeobox gene NKX3-1 in subsets of T-cell lymphoblastic leukemia (T-ALL).
PLoS One. 2012; 7(7):e40747 [PubMed] Free Access to Full Article Related Publications
Homeobox genes encode transcription factors impacting key developmental processes including embryogenesis, organogenesis, and cell differentiation. Reflecting their tight transcriptional control, homeobox genes are often embedded in large non-coding, cis-regulatory regions, containing tissue specific elements. In T-cell acute lymphoblastic leukemia (T-ALL) homeobox genes are frequently deregulated by chromosomal aberrations, notably translocations adding T-cell specific activatory elements. NKX3-1 is a prostate specific homeobox gene activated in T-ALL patients expressing oncogenic TAL1 or displaying immature T-cell characteristics. After investigating regulation of NKX3-1 in primary cells and cell lines, we report its ectopic expression in T-ALL cells independent of chromosomal rearrangements. Using siRNAs and expression profiling, we exploited NKX3-1 positive T-ALL cell lines as tools to investigate aberrant activatory mechanisms. Our data confirmed NKX3-1 activation by TAL1/GATA3/LMO and identified LYL1 as an alternative activator in immature T-ALL cells devoid of GATA3. Moreover, we showed that NKX3-1 is directly activated by early T-cell homeodomain factor MSX2. These activators were regulated by MLL and/or by IL7-, BMP4- and IGF2-signalling. Finally, we demonstrated homeobox gene SIX6 as a direct leukemic target of NKX3-1 in T-ALL. In conclusion, we identified three major mechanisms of NKX3-1 regulation in T-ALL cell lines which are represented by activators TAL1, LYL1 and MSX2, corresponding to particular T-ALL subtypes described in patients. These results may contribute to the understanding of leukemic transcriptional networks underlying disturbed T-cell differentiation in T-ALL.

Cubedo E, Gentles AJ, Huang C, et al.
Identification of LMO2 transcriptome and interactome in diffuse large B-cell lymphoma.
Blood. 2012; 119(23):5478-91 [PubMed] Free Access to Full Article Related Publications
LMO2 regulates gene expression by facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the germinal center (GC) and is expressed in GC-derived non-Hodgkin lymphomas. LMO2 is one of the most powerful prognostic indicators in diffuse large B-cell (DLBCL) patients. However, its function in GC B cells and DLBCL is currently unknown. In this study, we characterized the LMO2 transcriptome and transcriptional complex in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly, and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners, such as LDB1, E2A, HEB, Lyl1, ETO2, and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, nuclear factor of activated T-cells (NFATc1), and lymphoid enhancer-binding factor1 (LEF1) proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provides a platform for future elucidation of LMO2 function in GC B cells and DLBCL pathogenesis.

Homminga I, Vuerhard MJ, Langerak AW, et al.
Characterization of a pediatric T-cell acute lymphoblastic leukemia patient with simultaneous LYL1 and LMO2 rearrangements.
Haematologica. 2012; 97(2):258-61 [PubMed] Free Access to Full Article Related Publications
Translocation of the LYL1 oncogene are rare in T-cell acute lymphoblastic leukemia, whereas the homologous TAL1 gene is rearranged in approximately 20% of patients. Previous gene-expression studies have identified an immature T-cell acute lymphoblastic leukemia subgroup with high LYL1 expression in the absence of chromosomal aberrations. Molecular characterization of a t(7;19)(q34;p13) in a pediatric T-cell acute lymphoblastic leukemia patient led to the identification of a translocation between the TRB@ and LYL1 loci. Similar to incidental T-cell acute lymphoblastic leukemia cases with synergistic, double translocations affecting TAL1/2 and LMO1/2 oncogenes, this LYL1-translocated patient also had an LMO2 rearrangement pointing to oncogenic cooperation between LYL1 and LMO2. In hierarchical cluster analyses based on gene-expression data, this sample consistently clustered along with cases having TAL1 or LMO2 rearrangements. Therefore, LYL1-rearranged cases are not necessarily associated with immature T-cell development, despite high LYL1 levels, but elicit a TALLMO expression signature.

Thoms JA, Birger Y, Foster S, et al.
ERG promotes T-acute lymphoblastic leukemia and is transcriptionally regulated in leukemic cells by a stem cell enhancer.
Blood. 2011; 117(26):7079-89 [PubMed] Related Publications
The Ets-related gene (ERG) is an Ets-transcription factor required for normal blood stem cell development. ERG expression is down-regulated during early T-lymphopoiesis but maintained in T-acute lymphoblastic leukemia (T-ALL), where it is recognized as an independent risk factor for adverse outcome. However, it is unclear whether ERG is directly involved in the pathogenesis of T-ALL and how its expression is regulated. Here we demonstrate that transgenic expression of ERG causes T-ALL in mice and that its knockdown reduces the proliferation of human MOLT4 T-ALL cells. We further demonstrate that ERG expression in primary human T-ALL cells is mediated by the binding of other T-cell oncogenes SCL/TAL1, LMO2, and LYL1 in concert with ERG, FLI1, and GATA3 to the ERG +85 enhancer. This enhancer is not active in normal T cells but in transgenic mice targets expression to fetal liver c-kit(+) cells, adult bone marrow stem/progenitors and early CD4(-)CD8(-) double-negative thymic progenitors. Taken together, these data illustrate that ERG promotes T-ALL and that failure to extinguish activity of stem cell enhancers associated with regulatory transcription factors such as ERG can contribute to the development of leukemia.

Nagel S, Venturini L, Meyer C, et al.
Transcriptional deregulation of oncogenic myocyte enhancer factor 2C in T-cell acute lymphoblastic leukemia.
Leuk Lymphoma. 2011; 52(2):290-7 [PubMed] Related Publications
Myocyte enhancer factor 2C (MEF2C) encodes a transcription factor which is ectopically expressed in T-cell acute lymphoblastic leukemia (T-ALL) cell lines, deregulated directly by ectopically expressed homeodomain protein NKX2-5 or by loss of promoter regions via del(5)(q14). Here, we analyzed the MEF2C 5'-region, thus identifying potential regulatory binding sites for GFI1B, basic helix-loop-helix proteins, STAT5, and HOXA9/HOXA10. Chromatin immunoprecipitation and overexpression analyses demonstrated direct activation by GFI1B and LYL1 and inhibition by STAT5. HOXA9/HOXA10 activated expression of NMYC which in turn mediated MEF2C repression, indicating an indirect mode of regulation via NMYC interactor (NMI) and STAT5. Lacking comma: Chromosomal deletion of the STAT5 binding site in LOUCY cells reduced protein levels of STAT5 in some MEF2C-positve T-ALL cell lines, and the presence of inhibitory IL7-JAK-STAT5 signaling highlighted the repressive impact of this factor in MEF2C regulation. Taken together, our results indicate that the expression of MEF2C in T-ALL cells is principally deregulated via activating leukemic transcription factors GFI1B or NKX2-5 and by escaping inhibitory developmental STAT5 signaling.

Pirot N, Deleuze V, El-Hajj R, et al.
LYL1 activity is required for the maturation of newly formed blood vessels in adulthood.
Blood. 2010; 115(25):5270-9 [PubMed] Related Publications
The 2 related basic helix loop helix genes, LYL1 and TAL-1 are active in hematopoietic and endothelial lineages. While Tal-1 is essential for both hematopoietic and vascular development, the role of Lyl1 appears to be distinct as deficient mice are viable and display modest hematopoietic defects. Here, we reveal a role for Lyl1 as a major regulator of adult neovascularization. Tumors implanted into Lyl1-deficient mice showed higher proliferation and angiogenesis, as evidenced by enlarged lumens, reduced pericyte coverage and increased permeability, compared with wild type littermates. Of note, Lyl1-deficient tumor vessels exhibited an up-regulation of Tal-1, the VE-Cadherin target gene, as well as Angiopoietin-2, 3 major actors in angiogenesis. Hematopoietic reconstitution experiments demonstrated that this sustained tumor angiogenesis was of endothelial origin. Moreover, the angiogenic phenotype observed in the absence of Lyl1 function was not tumor-restricted as microvessels forming in Matrigel or originating from aortic explants were also more numerous and larger than their wild-type counterparts. Finally, LYL1 depletion in human endothelial cells revealed that LYL1 controls the expression of molecules involved in the stabilization of vascular structures. Together, our data show a role for LYL1 in the postnatal maturation of newly formed blood vessels.

Nagel S, Venturini L, Meyer C, et al.
Multiple mechanisms induce ectopic expression of LYL1 in subsets of T-ALL cell lines.
Leuk Res. 2010; 34(4):521-8 [PubMed] Related Publications
Basic helix-loop-helix (bHLH) transcription factors are essential for lymphocytic differentiation. Here, we have analyzed the complete bHLH family in T-cell acute lymphoblastic leukemia cell lines by expression profiling. Differential expression was detected for BHLHB2, HES1, HES4, HEY1, ID1, ID2, ID3, LYL1 and TAL1, highlighting dysregulation of family members with inhibitory activity. Subsequently we focused on the mechanisms responsible for aberrant expression of LYL1 in comparison to TAL1. Quantitative genomic PCR indicated microdeletions upstream of both, TAL1 and LYL1, targeting STIL/SIL and TRMT1, respectively. Additionally, one LYL1-expressing cell line exhibited amplification of TRMT1. While deletion of STIL correlated with expression of the STIL-TAL1 fusion transcript, no TRMT-LYL1 fusion transcripts were detected in parallel with genomic rearrangements thereof. Sequence analysis of the LYL1 promoter region revealed potential binding sites for transcription factors HOXA10, LMO2 and NKX2-5. Overexpression analysis, reporter gene assays and chromatin immuno-precipitation confirmed their activating impact on LYL1 expression. In conclusion, we identified multiple mechanisms which activate LYL1 in leukemic cells, including structural genomic alterations, namely microdeletion or amplification, together with the involvement of prominent oncogenic transcription factors.

O'Neil J, Look AT
Mechanisms of transcription factor deregulation in lymphoid cell transformation.
Oncogene. 2007; 26(47):6838-49 [PubMed] Related Publications
The most frequent targets of genetic alterations in human lymphoid leukemias are transcription factor genes with essential functions in blood cell development. TAL1, LYL1, HOX11 and other transcription factors essential for normal hematopoiesis are often misexpressed in the thymus in T-cell acute lymphoblastic leukemia (T-ALL), leading to differentiation arrest and cell transformation. Recent advances in the ability to assess DNA copy number have led to the discovery that the MYB transcription factor oncogene is tandemly duplicated in T-ALL. The NOTCH1 gene, which is essential for key embryonic cell-fate decisions in multicellular organisms, was found to be activated by mutation in a large percentage of T-ALL patients. The gene encoding the FBW7 protein ubiquitin ligase, which regulates the turnover of the intracellular form of NOTCH (ICN), is also mutated in T-ALL, resulting in stabilization of the ICN and activation of the NOTCH signaling pathway. In mature B-lineage ALL and Burkitt lymphoma, the MYC transcription factor oncogene is overexpressed due to translocation into the IG locus. PAX5, a transcription factor essential for B-lineage commitment, is inactivated in 32% of cases of B-progenitor ALL. Translocations resulting in oncogenic fusion transcription factors also occur frequently in this form of ALL. The most frequent transcription factor chimeric fusion, TEL-AML1, is an initiating event in B-progenitor ALL that acts by repressing transcription. Therefore, deregulated transcription and its consequent effects on key developmental pathways play a major role in the molecular pathogenesis of lymphoid malignancy. Once the full complement of cooperating mutations in transformed B- and T-progenitor cells is known, and the deregulated downstream pathways have been elucidated, it will be possible to identify vulnerable components and to target them with small-molecule inhibitors.

Zhong Y, Jiang L, Hiai H, et al.
Overexpression of a transcription factor LYL1 induces T- and B-cell lymphoma in mice.
Oncogene. 2007; 26(48):6937-47 [PubMed] Related Publications
LYL1, a member of the class II basic helix-loop-helix transcription factors, is aberrantly expressed in a fraction of human T-cell acute lymphoblastic leukemia. Here, we generated transgenic mice ubiquitously overexpressing LYL1 using a construct expressing full-length cDNA driven by a human elongation factor 1alpha promoter. Four independent lines exhibiting high LYL1 expression were established. Of these transgenic mice, 96% displayed loss of hair with a short kinked tail. Furthermore, 30% of them developed malignant lymphoma, with an average latent period of 352 days. In these mice, histological examination revealed tumor cell infiltration in multiple organs and immunohistochemical analysis showed that the infiltrated tumor cells were either CD3 or CD45R/B220-positive; fluorescence-activated cell sorter analysis indicated that each tumor consisted either of mainly CD4, CD8 double-positive T cells or mature B cells; the clonality of LYL1-induced lymphoma was confirmed by T-cell receptor rearrangement and immunoglobulin heavy-chain gene rearrangement analyses. Mammalian two-hybrid analysis and luciferase assay suggested that excess LYL1 blocked the dimerization of E2A and thus inhibited the regulatory activity of E2A on the CD4 promoter. Reverse transcription-polymerase chain reaction results showed that the expression of certain E2A/HEB target genes was downregulated. Taken together, our results provide direct evidence that aberrant expression of LYL1 plays a role in lymphomagenesis.

Han X, Bueso-Ramos CE
Precursor T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma and acute biphenotypic leukemias.
Am J Clin Pathol. 2007; 127(4):528-44 [PubMed] Related Publications
Session 4 of the 2005 Society of Hematopathology/European Association for Haematopathology Workshop focused on case presentations of precursor T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma (pre-T ALL/LBL) and acute biphenotypic leukemia. Pre-T ALL represents approximately 15% of childhood and 25% of adult ALL cases. Pre-T LBL comprises 85% to 90% of LBL and frequently manifests as a mediastinal mass. Gene expression studies have shown distinct subtypes of LYL1+, HOX11+, TAL1+, and MLL+ pre-T ALL/LBL. HOX11 overexpression may correlate with a good prognosis in adult pre-T ALL. ABL gene amplification and NOTCH1 gene mutations in subsets of pre-T ALL/LBL suggest patients may benefit from therapy with tyrosine kinase and gamma-secretase inhibitors, respectively. Acute biphenotypic leukemias are characterized by a single population of blasts that express myeloid, T- or B-lineage antigens in various combinations and account for fewer than 4% of all acute leukemias. The blasts have a high incidence of chromosome abnormalities. An accurate diagnosis of pre-T ALL/LBL and acute biphenotypic leukemia requires a multiparametric approach, including examination of morphologic features, immunophenotype, clinical characteristics, and cytogenetic and molecular findings.

Pike-Overzet K, de Ridder D, Weerkamp F, et al.
Ectopic retroviral expression of LMO2, but not IL2Rgamma, blocks human T-cell development from CD34+ cells: implications for leukemogenesis in gene therapy.
Leukemia. 2007; 21(4):754-63 [PubMed] Related Publications
The occurrence of leukemia in a gene therapy trial for SCID-X1 has highlighted insertional mutagenesis as an adverse effect. Although retroviral integration near the T-cell acute lymphoblastic leukemia (T-ALL) oncogene LIM-only protein 2 (LMO2) appears to be a common event, it is unclear why LMO2 was preferentially targeted. We show that of classical T-ALL oncogenes, LMO2 is most highly transcribed in CD34+ progenitor cells. Upon stimulation with growth factors typically used in gene therapy protocols transcription of LMO2, LYL1, TAL1 and TAN1 is most prominent. Therefore, these oncogenes may be susceptible to viral integration. The interleukin-2 receptor gamma chain (IL2Rgamma), which is mutated in SCID-X1, has been proposed as a cooperating oncogene to LMO2. However, we found that overexpressing IL2Rgamma had no effect on T-cell development. In contrast, retroviral overexpression of LMO2 in CD34+ cells caused severe abnormalities in T-cell development, but B-cell and myeloid development remained unaffected. Our data help explain why LMO2 was preferentially targeted over many of the other known T-ALL oncogenes. Furthermore, during T-cell development retrovirus-mediated expression of IL2Rgamma may not be directly oncogenic. Instead, restoration of normal IL7-receptor signaling may allow progression of T-cell development to stages where ectopic LMO2 expression causes aberrant thymocyte growth.

Heerema NA, Bernheim A, Lim MS, et al.
State of the Art and Future Needs in Cytogenetic/Molecular Genetics/Arrays in childhood lymphoma: summary report of workshop at the First International Symposium on childhood and adolescent non-Hodgkin lymphoma, April 9, 2003, New York City, NY.
Pediatr Blood Cancer. 2005; 45(5):616-22 [PubMed] Related Publications
BACKGROUND: A significant number of studies describe the cytogenetics and molecular genetics of adult non-Hodgkin lymphoma (NHL); however, similar knowledge is lacking regarding pediatric NHL.
METHODS: A workshop to discuss the "State of the Art and Future Needs in Cytogenetic/Molecular Genetics/Arrays" in pediatric NHL was held in conjunction with the First International Symposium on Childhood and Adolescent Non-Hodgkin Lymphoma on April 9, 2003 in New York City.
RESULTS: Cytogenetic characteristics of pediatric NHL include 14q11.2 rearrangements in T-cell lymphoblastic leukemia/lymphomas (LBL), ALK rearrangements in anaplastic large cell lymphomas (ALCL), and CMYC translocations in both Burkitt and Burkitt-like lymphomas (BL/BLL). Pediatric diffuse large B-cell lymphoma (DLBCL) is cytogenetically different from DLBCL in adults, suggesting a different disease in children. Microarray studies demonstrate three types of T-cell leukemia, the leukemic counterpart of LBL, that block T-cell differentiation at different stages of T-cell development, corresponding to LYL, TAL1, and HOX-expressing leukemias. ALCL cell lines have a unique expression profile compared to normal T-cells. Germinal centers of BL have CMYC expression signatures, indicating that CMYC expression is ectopic and does not reflect the physiology of the normal cell counterpart.
CONCLUSIONS: Additional cytogenetic, molecular and microarray investigations of NHL in children are vital to better understand these diseases, their etiology, and differences from adult NHL. A greater understanding of pediatric NHL will lead to disease-specific and patient-individualized therapies of these diseases.

Meng YS, Khoury H, Dick JE, Minden MD
Oncogenic potential of the transcription factor LYL1 in acute myeloblastic leukemia.
Leukemia. 2005; 19(11):1941-7 [PubMed] Related Publications
The LYL1 gene encodes a basic helix-loop-helix transcription factor involved in T-cell acute lymphoblastic leukemia. Using real-time quantitative RT-PCR assay, we found that the expression of LYL1 was at higher levels in the majority cases of acute myeloblastic leukemia (AML) or myelodysplastic syndrome when compared to normal bone marrow. Our study also showed that LYL1 was highly expressed in most AML cell lines and in CD34+ AML cells. To determine whether LYL1 had an affect on the phenotype and behavior of myeloid cells, we introduced full-length LYL1 cDNA into K562 cells using electroporation and U937 cells with retroviral infection. Both of the derivative cell lines with overexpression of LYL1 had an increased growth rate and clonogenecity. Forced expression of LYL1 in K562 cells enhanced spontaneous and hemin-induced erythroid differentiation but blocked spontaneous as well as PMA-induced megakaryocytic differentiation. Overexpression of LYL1 in U937 cells blocked all-trans retinoic acid-induced monocytic differentiation. The LYL1-transfected U937 cells were also more resistant to the cytotoxic drug cytarabine. These results demonstrate that LYL1 may play a role in early hematopoiesis and may be a potential oncogenic factor in AML.

Asnafi V, Beldjord K, Libura M, et al.
Age-related phenotypic and oncogenic differences in T-cell acute lymphoblastic leukemias may reflect thymic atrophy.
Blood. 2004; 104(13):4173-80 [PubMed] Related Publications
Postnatal thymic involution occurs progressively throughout the first 3 decades of life. It predominantly affects T-cell receptor (TCR) alphabeta-lineage precursors, with a consequent proportional increase in multipotent thymic precursors. We show that T-acute lymphoblastic leukemias (T-ALLs) demonstrate a similar shift with age from predominantly TCR expressing to an immature (IM0/delta/gamma) stage of maturation arrest. Half demonstrate HOX11, HOX11L2, SIL-TAL1, or CALM-AF10 deregulation, with each being associated with a specific, age-independent stage of maturation arrest. HOX11 and SIL-TAL represent alphabeta-lineage oncogenes, whereas HOX11L2 expression identifies an intermediate alphabeta/gammadelta-lineage stage of maturation arrest. In keeping with preferential alphabeta-lineage involution, the incidence of SIL-TAL1 and HOX11L2 deregulation decreased with age. In contrast, HOX11 deregulation became more frequent, suggesting longer latency. TAL1/LMO1 deregulation is more frequent in alphabeta-lineage T-ALL, when it is predominantly due to SIL-TAL1 rearrangements in children but to currently unknown mechanisms in adolescents and adults. LMO2 was more frequently coexpressed with LYL1, predominantly in IM0/delta/gamma adult cases, than with TAL1. These age-related changes in phenotype and oncogenic pathways probably reflect progressive changes in the thymic population at risk of malignant transformation.

Ferrando AA, Neuberg DS, Dodge RK, et al.
Prognostic importance of TLX1 (HOX11) oncogene expression in adults with T-cell acute lymphoblastic leukaemia.
Lancet. 2004; 363(9408):535-6 [PubMed] Related Publications
The activation of oncogenic transcription factors defines distinct molecular subsets of T-cell acute lymphoblastic leukaemia and has prognostic relevance in children. We investigated the prognostic effect of the expression levels of eight oncogenic transcription factors--TLX1 (HOX11), TLX3 (HOX11L2), TAL1, TAL2, LYL1, OLIG2 (BHLHB1), LMO1, and LMO2--in 52 adults with T-cell acute lymphoblastic leukaemia. The leukaemia-specific survival rate for the 16 TLX1-positive patients was 88% (90% CI 73-100%), compared with 56% (42-70%) for all other cases (p=0.019). Only the TLX1 oncogene expression subgroup showed difference in leukaemia-specific survival. Our results suggest that overexpression of TLX1 confers a good outlook for adults with T-cell acute lymphoblastic leukaemia. Furthermore, our findings lead to questions about whether stem-cell transplantation in first remission is necessary for effective treatment of patients in the low-risk subgroup of patients with TLX1 oncogene expression.

Ferrando AA, Herblot S, Palomero T, et al.
Biallelic transcriptional activation of oncogenic transcription factors in T-cell acute lymphoblastic leukemia.
Blood. 2004; 103(5):1909-11 [PubMed] Related Publications
Aberrant expression of transcription factor oncogenes such as HOX11, HOX11L2, TAL1/SCL, LYL1, LMO1, and LMO2 can be detected in lymphoblasts from up to 80% of patients with acute T-cell lymphoblastic leukemia (T-ALL). Transcriptional activation of these oncogenes in leukemic cells typically results from chromosomal rearrangements that place them next to highly active cis-acting transcriptional regulatory elements. However, biallelic activation of TAL1 in some T-ALL cases has been previously proposed. We have used allele-specific mRNA analysis to show that trans-acting mechanisms leading to biallelic overexpression of TAL1 are involved in 10 (42%) of 24 TAL1+ informative T-ALL cases, 2 (17%) of 12 HOX11+ informative cases, and 7 (64%) of 11 LMO2+ informative cases. We propose that aberrant expression of oncogenic transcription factors in a significant fraction of T-ALLs may result from loss of the upstream transcriptional mechanisms that normally down-regulate the expression of these oncogenes during T-cell development.

Ferrando AA, Look AT
Gene expression profiling in T-cell acute lymphoblastic leukemia.
Semin Hematol. 2003; 40(4):274-80 [PubMed] Related Publications
T-cell acute lymphoblastic leukemia (T-ALL) presents a difficult medical problem. T-ALL's clinical features and the biological properties of the leukemia cells are not predictive of prognosis, and thus have not been useful for risk-specific adjustments in therapeutic intensity. Microarray gene expression analyses of T-cell leukemic lymphoblasts have not only improved our understanding of the biological heterogeneity of this disease but have revealed clinically relevant molecular subtypes. Five different multistep molecular pathways have been identified that lead to T-ALL, involving activation of different T-ALL oncogenes: (1) HOX11, (2) HOX11L2, (3) TAL1 plus LMO1/2, (4) LYL1 plus LMO2, and (5) MLL-ENL. Gene expression studies indicate activation of a subset of these genes-HOX11, TAL1, LYL1, LMO1, and LMO2-in a much larger fraction of T-ALL cases than those harboring activating chromosomal translocations. In many such cases, the abnormal expression of one or more of these oncogenes is biallelic, implicating upstream regulatory mechanisms. Among these molecular subtypes, overexpression of the HOX11 orphan homeobox gene occurs in approximately 5% to 10% of childhood and 30% of adult T-ALL cases. Patients with HOX11-positive lymphoblasts have an excellent prognosis when treated with modern combination chemotherapy, while cases at high risk of early failure are included largely in the TAL1- and LYL1-positive groups. Supervised learning approaches applied to microarray data have identified a group of genes whose expression is able to distinguish high-risk cases. Further analyses of gene expression signatures of T-ALL lymphoblasts are especially needed for patients treated on modern combination chemotherapy trials to clearly distinguish the 10% to 15% of patients who fail induction or relapse in the first year of treatment. These high-risk patients would be ideal candidates for more intensive therapies in first remission, such as myeloablative regimens with stem cell rescue. Based on the rapid pace of research in T-ALL, made possible in large part through microarray technology, deep analysis of molecular pathways should lead to new and much more specific targeted therapies.

Ballerini P, Blaise A, Busson-Le Coniat M, et al.
HOX11L2 expression defines a clinical subtype of pediatric T-ALL associated with poor prognosis.
Blood. 2002; 100(3):991-7 [PubMed] Related Publications
The most frequent oncogenic activation events characterized in childhood T acute lymphoblastic leukemia (T-ALL) result in the transcriptional activation of genes coding for transcription factors. The main genes are TAL1/SCL, a member of the basic region helix-loop-helix gene family, and HOX11L2, a member of the homeobox-containing protein family. To gain insight into the pathogenesis of this type of hematologic malignancy, we analyzed 28 T-ALL samples. SIL-TAL1/SCL fusion was detected in 6 patients; expression of HOX11L2 was observed in 6 patients and of HOX11 in 3 patients. With one exception, these activations did not occur simultaneously in the same patients, and they allowed the subclassification of 50% of the patients. SIL-TAL1 fusion was detected in association with HOX11 expression in one patient and with a t(8;14) (q24;q11) in another. High expression of LYL1, LMO2, or TAL1 was observed mainly in samples negative for HOX11L2 expression. HOX11L1 and HOX11 expression were observed in one instance each, in the absence of detectable chromosomal abnormality of their respective loci, on chromosomes 2 and 10, respectively. HOX11L2 expression was associated with a chromosome 5q abnormality, the location of the HOX11L2 locus in each case tested. Finally, our data show that HOX11L2 expression was a suitable marker for minimal residual disease follow-up and was significantly associated with relapse (P =.02).

Ferrando AA, Neuberg DS, Staunton J, et al.
Gene expression signatures define novel oncogenic pathways in T cell acute lymphoblastic leukemia.
Cancer Cell. 2002; 1(1):75-87 [PubMed] Related Publications
Human T cell leukemias can arise from oncogenes activated by specific chromosomal translocations involving the T cell receptor genes. Here we show that five different T cell oncogenes (HOX11, TAL1, LYL1, LMO1, and LMO2) are often aberrantly expressed in the absence of chromosomal abnormalities. Using oligonucleotide microarrays, we identified several gene expression signatures that were indicative of leukemic arrest at specific stages of normal thymocyte development: LYL1+ signature (pro-T), HOX11+ (early cortical thymocyte), and TAL1+ (late cortical thymocyte). Hierarchical clustering analysis of gene expression signatures grouped samples according to their shared oncogenic pathways and identified HOX11L2 activation as a novel event in T cell leukemogenesis. These findings have clinical importance, since HOX11 activation is significantly associated with a favorable prognosis, while expression of TAL1, LYL1, or, surprisingly, HOX11L2 confers a much worse response to treatment. Our results illustrate the power of gene expression profiles to elucidate transformation pathways relevant to human leukemia.

Brückner R, Jentsch-Ullrich K, Franke A, et al.
A novel translocation (17;19)(p13;p13) in a patient with acute myelomonocytic leukemia.
Cancer Genet Cytogenet. 2000; 119(1):77-9 [PubMed] Related Publications
We report on a patient with acute myeloid leukemia (AML M4) and a so far unrecorded translocation (17;19). The leukemia transformed from a myeloproliferative disorder (MPD) and showed a progressive fatal course. Following transformation, all leukemic cells showed an apparently balanced translocation (17;19)(p13;p13). The breakpoint regions harbor genes such as TP53 (17p13) and E2A, ENL, or LYL1 (19p13), which could be relevant in leukemogenesis. We suspect that the translocation (17;19)(p13;p13) may be a prognostic factor for transformation from chronic MPD to acute leukemia.

Ferrier R, Nougarede R, Doucet S, et al.
Physical interaction of the bHLH LYL1 protein and NF-kappaB1 p105.
Oncogene. 1999; 18(4):995-1005 [PubMed] Related Publications
The LYL1 gene was first identified upon the molecular characterization of the t(7;9)(q35;p13) translocation associated with some human T-cell acute leukemias (T-ALLs). In adult tissues, LYL1 expression is restricted to hematopoietic cells with the notable exclusion of the T cell lineage. LYL1 encodes a basic helix-loop-helix (bHLH) protein highly related to TAL-1, whose activation is also associated with a high proportion of human T-ALLs. A yeast two-hybrid system was used to identify proteins that specifically interact with LYL1 and might mediate its activities. We found that p105, the precursor of NF-kappaB1 p50, was the major LYL1-interacting protein in this system. The association between LYL1 and p105 was confirmed both in vitro and in vivo in mammalian cells. Biochemical studies indicated that the interaction was mediated by the bHLH motif of LYL1 and the ankyrin-like motifs of p105. Ectopic expression of LYL1 in a human T cell line caused a significant decrease in NF-kappaB-dependent transcription, associated with a reduced level of NF-kappaB1 proteins.

Gu ZX, Womack JE, Kirkpatrick BW
Synteny mapping of four genes from the short arm of human chromosome 19 to bovine chromosome 7.
Cytogenet Cell Genet. 1997; 79(3-4):225-7 [PubMed] Related Publications
Four genes on the short arm of human chromosome 19 (HSA 19p) were assigned to bovine chromosome 7 (BTA 7) using a bovine x rodent somatic hybrid cell panel. These four genes were cartilage oligomeric matrix protein (COMP), lymphoblastic leukemia derived sequence 1 (LYL1), lysosomal alpha-mannosidase (MANB), and RAS oncogene family member RAB3A. Bovine sequence tagged sites were developed for the four genes and used for screening a bovine x rodent somatic cell panel. All four genes were mapped to bovine synteny group U22 (BTA 7) with a correlation coefficient of 0.901-1.000. This study confirms that the centromeric region of BTA 7 is conserved with HSA 19p.

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