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APOBEC Signature Mutation Forms an Oncogenic Enhancer Upstream of LMO1 in T-ALL

ABSTRACT: Oncogenic driver mutations are those that provide a proliferative or survival advantage to neoplastic cells resulting in clonal selection. Although most cancer causing mutations have been detected in the protein-coding regions of the cancer genome, driver mutations have recently also been discovered within noncoding genomic sequences. Thus, a current challenge is to gain precise understanding of how these unique genomic elements function in cancer pathogenesis, while clarifying mechanisms of gene regulation and identifying new targets for therapeutic intervention. Here we report a C-to-T single nucleotide transition that occurs as a somatic mutation in noncoding sequences 4 kb upstream of the transcriptional start site of the LMO1 oncogene in primary samples from patients with T-cell acute lymphoblastic leukaemia. This single nucleotide alteration conforms to an APOBEC-like cytidine deaminase mutational signature, and generates a new binding site for the MYB transcription factor, leading to the formation of an aberrant transcriptional enhancer complex that drives high levels of expression of the LMO1 oncogene. Since APOBEC-signature mutations are common in a broad spectrum of human cancers, we suggest that noncoding nucleotide transitions such as the one described here may activate potent oncogenic enhancers not only in T-lymphoid cells but in other cell lineages as well.

ORGANISM(S): Homo sapiens

PROVIDER: GSE94391 | GEO | 2017/03/08

SECONDARY ACCESSION(S): PRJNA369547

REPOSITORIES: GEO

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SCL and LMO1 reprogram thymocytes into self-renewing cells.

Project description:The SCL and LMO1 oncogenic transcription factors reprogram thymocytes into self-renewing pre-leukemic stem cells (pre-LSCs). Here we report that SCL directly interacts with LMO1 to activate the transcription of a self-renewal program coordinated by LYL1. Gene expression profiles of thymocytes from SCL-LMO1 transgenic and age-matched non transgenic Cd3Îµ-/- mice were compared to identify candidate genes that confer self-renewal capability to pre-leukemic thymocytes.

2015-11-05 | E-GEOD-74659 | biostudies-arrayexpress

LMO1 Synergizes with MYCN to Promotes Neuroblastoma Initiation and Metastasis

Project description:High levels of LMO1 expression synergizes with MYCN to accelerate neuroblastomagenesis, enhance disease penetrance and promote widespread metastasis in zebrafish. Transcriptomic analysis of human neuroblasotma cells with programed expression of LMO1 vs vector control or neuroblastoma cells with differential endogenous LMO1 expression revealed that gene signitures affecting tumor cell-extracellular matrix interaction are significantly associated with high levels of LMO1 expression. Our findings provide compelling evidence for a major pathogenic role of LMO1 in MYCN-driven neuroblastoma.

2017-07-31 | GSE90087 | GEO

ASCL1 is directly activated by the LMO1 and MYCN oncogenes and is a master regulator of the differentiation program in neuroblastoma

Project description:Neuroblastoma is an embryonal tumor of the peripheral sympathetic nervous system. Elevated expression of the transcription factor LMO1 and the polymorphisms within this gene are associated with the susceptibility to develop neuroblastoma. LMO1 has been implicated as an oncogene in T-cell acute lymphoblastic leukemia; however, the transcriptional targets regulated by this protein in neuroblastoma cells are unknown. Here, we identify the genes and molecular pathways controlled by LMO1 in neuroblastoma cells. ChIP-seq analysis revealed that LMO1-bound regions are frequently co-occupied by GATA3 and MYCN proteins and are associated with active histone marks in neuroblastoma cells. RNA-seq analysis demonstrated that LMO1 regulates gene expression in a tumor type-specific manner. One high-confidence target gene directly regulated by LMO1 and MYCN is ASCL1, which is more highly expressed in adrenergic subtype of neuroblastoma cells as compared to normal neuronal cells. High levels of ASCL1 expression are associated with inferior overall survival in primary human neuroblastoma cases. ChIP-seq analysis identified a regulatory element controlling ASCL1 expression that is bound by LMO1, MYCN and the members of the core regulatory circuitry in neuroblastoma cells. Furthermore, ASCL1 is required for neuroblastoma cell growth and regulates genes responsible for repression of neuronal cell differentiation. Taken together, our results implicate ASCL1 as a critical downstream target of LMO1 in the molecular pathogenesis of neuroblastoma.

2019-11-09 | GSE120074 | GEO

Genetic predisposition to neuroblastoma mediated by a single nucleotide polymorphism within a LMO1 oncogene super-enhancer element

Project description:A previous genome-wide association study identified common polymorphisms at the LMO1 gene locus that are highly associated with neuroblastoma susceptibility in children and oncogenic addiction to LMO1 in the tumor cells1. Here we sought to discover the causal DNA variant at this locus and the mechanism by which it leads to neuroblastoma tumorigenesis. We first imputed all possible genotypes across the LMO1 locus and then mapped highly associated single nucleotide polymorphism (SNPs) to areas of chromatin accessibility, evolutionary conservation, and transcription factor binding sites. SNP rs2168101 G>T was the most highly associated variant (combined P=7.47x10-29, Odds Ratio 0.65, 95% CI: 0.60-0.70) and resided in a super-enhancer defined by extensive acetylation of histone H3 lysine 27 within the first intron of LMO1. The ancestral G allele that is associated with tumor formation resides in a conserved GATA transcription factor binding motif. We show that the newly evolved protective TATA allele is associated with decreased total LMO1 expression (P=0.028) in neuroblastoma primary tumors and ablates GATA3 binding (P=0.007). We demonstrate monoallelic LMO1 expression from the G-containing strand in tumors heterozygous for this SNP as demonstrated both by RNA sequencing (P<0.0001) and reporter assays (P=0.002). These findings show that a recently evolved polymorphism within a super-enhancer element in the first intron of LMO1 influences neuroblastoma susceptibility through differential GATA transcription factor binding and direct modulation of LMO1 expression in cis, and this leads to an oncogenic dependency in tumor cells.

2015-10-18 | GSE65664 | GEO

SCL and LMO1 reprogram thymocytes into self-renewing cells.

2015-11-05 | GSE74659 | GEO

SYNCRIP is the Molecular Brake of APOBEC-driven Mutagenesis, Tumor Heterogeneity and Therapy Resistance

Project description:Intratumoral genetic heterogeneity and mutational burden have been suggested to be the fuel and the source of resistance for many molecularly targeted therapies throughout a multitude of cancers. Emerging evidence indicates that tumor cells could hijack the powerful mutagenesis machinery mediated by the DNA deaminase APOBEC family proteins to intensify mutagenesis, promote intratumoral heterogeneity, and foster therapy resistance through a cell-autonomous mechanism. However, this mechanism has yet to be characterized. Utilizing prostate cancer (PCa) as a relevant model, we have identified the Synaptotagmin Binding Cytoplasmic RNA Interacting Protein (SYNCRIP) as a molecular brake for APOBEC-driven mutagenesis, intratumoral heterogeneity, and resistance to Androgen Receptor (AR) targeted therapies. Through a multi-disciplinary approach integrating bulk and single cell RNA-Seq (scRNA-Seq), whole-genome exome-sequencing (WES), and CRISPR library screening, we identified eight mutated resistance driver genes and revealed unparalleled details of how these heterogeneously aberrant subclones fuel the evolution of AR therapy resistance. For the first time, these findings exposed a cell-autonomous mechanism activating APOBEC-driven mutagenesis, consequently fueling mutational burden, genetic heterogeneity, and therapy resistance, and suggested that APOBEC proteins could be the potential therapeutic targets for preventing or overcoming resistance in PCa.

2023-07-20 | GSE202321 | GEO

Gene expression profile of human neuroblastoma cell line SHSY-5Y after LMO1 knockdown

Project description:To dissect molecular pathways regulated by LMO1 in neuroblastoma, we performed microarray gene expression profiling in a neuroblastoma cells (SHSY-5Y) after LMO1 knockdown.

2019-11-10 | GSE130747 | GEO

Apobec-Mediated Retroviral Hypermutation In Vivo is Dependent on Mouse Strain

Project description:Retroviruses cause lifelong infections resulting from their ability to thwart innate immunity. The Apobec family of cytidine deaminases are part of the innate immune response that recognizes and mutates foreign nucleic acids, including those from multiple viruses. Multiple retroviral antagonists of Apobecs have been identified, including mouse mammary tumor virus (MMTV)-encoded Rem protein. Previous experiments have shown that Rem-null MMTV or closely related TBLV proviruses from BALB/c tumors accumulate G-to-A and C-to-T mutations typical of Apobecs compared to wild-type proviruses expressing Rem. The difference in mutations between Rem-expressing and non-expressing MMTV strains largely disappeared in mice lacking the Apobec family member, activation-induced cytidine deaminase (AID). These results suggested that Rem is an AID antagonist. In this study, we attempted to study AID-mediated mutations of TBLV proviruses lacking Rem expression obtained from tumors in C57BL/6 (B6) wild-type and AID-knockout backgrounds. Surprisingly, no differences in G-to-A mutations were observed in TBLV proviruses regardless of Rem expression, yet such mutations were significantly reduced in proviruses obtained from mA3/AID-double knockout mice relative to those from wild-type B6 or AID-knockout mice. Many cellular mRNAs involving the innate immune response, but not Apobecs, were elevated in the absence relative to the presence of Rem expression on the B6 AID-knockout background. These results revealed that Apobec-mediated mutagenesis is dependent on mouse strain and suggested a second means of Rem-dependent immune evasion.

2024-04-16 | GSE263741 | GEO

Genome-wide identification and functional analysis of Apobec-1 mediated C-to-U RNA editing in mouse small intestine and liver

Project description:The genome-wide identification, tissue-specificity and functional implications of Apobec-1 mediated C-to-U RNA editing remains incomplete. Deep sequencing, data filtering and validation from wild-type and Apobec-1 deficient mice revealed 56 novel editing sites in 54 intestinal mRNAs and 22 novel sites in 17 liver mRNAs (74-81% true-positive), all within 3' untranslated regions. Eleven of 17 liver RNAs shared editing sites with intestinal RNAs, while 6 sites were unique to liver. Changes in RNA editing led to corresponding changes in intestinal mRNA and protein levels in 11 genes. We found distinctive polysome profiles for several editing targets and demonstrated nuclear but not cytoplasmic editing of novel exonic sites in intestinal (but not hepatic) apoB RNA. RNA editing was validated using cell-free extracts from wild-type but not Apobec-1 deficient mice. These studies define selective, tissue-specific targets of Apobec-1 dependent RNA editing and show the functional consequences of editing are both transcript- and tissue-specific. Examination of C-to-U RNA editing in mouse liver and intestine

2014-05-23 | E-GEOD-57910 | biostudies-arrayexpress

Apobec-Mediated Retroviral Hypermutation In Vivo is Dependent on Mouse Strain [RNA-seq]

2024-04-15 | GSE263655 | GEO

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