Dataset Information

Overexpression of the proneural transcription factor ASCL1 in chronic lymphocytic leukemia with a t(12;14)(q23.2;q32.3).

ABSTRACT: Background:Translocations of the IGH locus on 14q32.3 are present in about 8% of patients with chronic lymphocytic leukemia (CLL) and contribute to leukemogenesis by deregulating the expression of the IGH-partner genes. Identification of these genes and investigation of the downstream effects of their deregulation can reveal disease-causing mechanisms. Case presentation:We report on the molecular characterization of a novel t(12;14)(q23.2;q32.3) in CLL. As a consequence of the rearrangement ASCL1 was brought into proximity of the IGHJ-C? enhancer and was highly overexpressed in the aberrant B-cells of the patient, as shown by qPCR and immunohistochemistry. ASCL1 encodes for a transcription factor acting as a master regulator of neurogenesis, is overexpressed in neuroendocrine tumors and a promising therapeutic target in small cell lung cancer (SCLC). Its overexpression has also been recently reported in acute adult T-cell leukemia/lymphoma.To examine possible downstream effects of the ASCL1 upregulation in CLL, we compared the gene expression of sorted CD5+ cells of the translocation patient to that of CD19+ B-cells from seven healthy donors and detected 176 significantly deregulated genes (Fold Change ?2, FDR p???0.01). Deregulation of 55 genes in our gene set was concordant with at least two studies comparing gene expression of normal and CLL B-lymphocytes. INSM1, a well-established ASCL1 target in the nervous system and SCLC, was the gene with the strongest upregulation (Fold Change?=?209.4, FDR p?=?1.37E-4).INSM1 encodes for a transcriptional repressor with extranuclear functions, implicated in neuroendocrine differentiation and overexpressed in the majority of neuroendocrine tumors. It was previously shown to be induced in CLL cells but not in normal B-cells upon treatment with IL-4 and to be overexpressed in CLL cells with unmutated versus mutated IGHV genes. Its role in CLL is still unexplored. Conclusion:We identified ASCL1 as a novel IGH-partner gene in CLL. The neural transcription factor was strongly overexpressed in the patient's CLL cells. Microarray gene expression analysis revealed the strong upregulation of INSM1, a prominent ASCL1 target, which was previously shown to be induced in CLL cells upon IL-4 treatment. We propose further investigation of the expression and potential role of INSM1 in CLL.

SUBMITTER: Malli T

PROVIDER: S-EPMC5765657 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Overexpression of the proneural transcription factor ASCL1 in chronic lymphocytic leukemia with a t(12;14)(q23.2;q32.3).

Malli Theodora T Rammer Melanie M Haslinger Sabrina S Burghofer Jonathan J Burgstaller Sonja S Boesmueller Hans-Christian HC Marschon Renate R Kranewitter Wolfgang W Erdel Martin M Deutschbauer Sabine S Webersinke Gerald G

Molecular cytogenetics 20180111

<h4>Background</h4>Translocations of the <i>IGH</i> locus on 14q32.3 are present in about 8% of patients with chronic lymphocytic leukemia (CLL) and contribute to leukemogenesis by deregulating the expression of the <i>IGH</i>-partner genes. Identification of these genes and investigation of the downstream effects of their deregulation can reveal disease-causing mechanisms.<h4>Case presentation</h4>We report on the molecular characterization of a novel t(12;14)(q23.2;q32.3) in CLL. As a conseque ...[more]

PMID: 29344090

Similar Datasets

Project description:Neuroblastoma is believed to arise from sympathetic neuroblast precursors that fail to engage the neuronal differentiation programme, but instead become locked in a pro-proliferative developmental state. Achaete-scute homolog 1 (ASCL1) is a proneural master regulator of transcription which modulates both proliferation and differentiation of sympathetic neuroblast precursor cells during development, while its expression has been implicated in the maintenance of an oncogenic programme in MYCN-amplified neuroblastoma. However, the role of ASCL1 expression in neuroblastoma is not clear, especially as its levels vary considerably in different neuroblastoma cell lines. Here, we have investigated the role of ASCL1 in maintaining proliferation and controlling differentiation in both MYCN amplified and Anaplastic Lymphoma Kinase (ALK)-driven neuroblastoma cells. Using CRISPR deletion, we generated neuroblastoma cell lines lacking ASCL1 expression, and these grew more slowly than parental cells, indicating that ASCL1 contributes to rapid proliferation of MYCN amplified and non-amplified neuroblastoma cells. Genome-wide analysis after ASCL1 deletion revealed reduced expression of genes associated with neuronal differentiation, while chromatin accessibility at regulatory regions associated with differentiation genes was also attenuated by ASCL1 knock-out. In neuroblastoma, ASCL1 has been described as part of a core regulatory circuit of developmental regulators whose high expression is maintained by mutual cross-activation of a network of super enhancers and is further augmented by the activity of MYC/MYCN. Surprisingly, ASCL1 deletion had little effect on the transcription of CRC gene transcripts in these neuroblastoma cell lines, but the ability of MYC/MYCN and CRC component proteins, PHOX2B and GATA3, to bind to chromatin was compromised. Taken together, our results demonstrate several roles for endogenous ASCL1 in neuroblastoma cells: maintaining a highly proliferative phenotype, regulating DNA binding of the core regulatory circuit genes to chromatin, while also controlling accessibility and transcription of differentiation targets. Thus, we propose a model where ASCL1, a key developmental regulator of sympathetic neurogenesis, plays a pivotal role in maintaining proliferation while simultaneously priming cells for differentiation in neuroblastoma.

Project description:BackgroundChronic lymphocytic leukemia (CLL) is the most frequent, and still incurable, form of leukemia in the Western World. It is widely accepted that cancer results from an evolutionary process shaped by the acquisition of driver mutations which confer selective growth advantage to cells that harbor them. Clear examples are missense mutations in classic RAS genes (KRAS, HRAS and NRAS) that underlie the development of approximately 13% of human cancers. Although autonomous B cell antigen receptor (BCR) signaling is involved and mutations in many tumor suppressor genes and oncogenes have been identified, an oncogenic driver gene has not still been identified for CLL.MethodsConditional knock-in mice were generated to overexpress wild type RRAS2 and prove its driver role. RT-qPCR analysis of a human CLL sample cohort was carried out to measure RRAS2 transcriptional expression. Sanger DNA sequencing was used to identify a SNP in the 3'UTR region of RRAS2 in human CLL samples. RNAseq of murine CLL was carried out to identify activated pathways, molecular mechanisms and to pinpoint somatic mutations accompanying RRAS2 overexpression. Flow cytometry was used for phenotypic characterization and shRNA techniques to knockdown RRAS2 expression in human CLL.ResultsRRAS2 mRNA is found overexpressed in its wild type form in 82% of the human CLL samples analyzed (n = 178, mean and median = 5-fold) as well as in the explored metadata. A single nucleotide polymorphism (rs8570) in the 3'UTR of the RRAS2 mRNA has been identified in CLL patients, linking higher expression of RRAS2 with more aggressive disease. Deliberate overexpression of wild type RRAS2 in mice, but not an oncogenic Q72L mutation in the coding sequence, provokes the development of CLL. Overexpression of wild type RRAS2 in mice is accompanied by a strong convergent selection of somatic mutations in genes that have been identified in human CLL. R-RAS2 protein is physically bound to the BCR and mediates BCR signals in CLL.ConclusionsThe results indicate that overexpression of wild type RRAS2 is behind the development of CLL.

Dataset Information

Overexpression of the proneural transcription factor ASCL1 in chronic lymphocytic leukemia with a t(12;14)(q23.2;q32.3).

Publications

Overexpression of the proneural transcription factor ASCL1 in chronic lymphocytic leukemia with a t(12;14)(q23.2;q32.3).

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets