Project description:<p>Pediatric low-grade gliomas (PLGGs) are the most common pediatric brain-tumor, with more than ten histologic subtypes recognized by the World Health Organization. We performed a genomic analysis of 230 PLGGs of which 73 had whole genome/RNA sequencing performed and show that MYB-QKI fusions define the seizure associated tumor, Angiocentric Glioma (AG). MYB-QKI fusions present in AGs contribute to tumorigenesis through three mechanisms: MYB activation by truncation, enhancer translocation driving aberrant MYB-QKI expression, and hemizygous loss of QKI, a tumor suppressor gene. Such interplay between three oncogenic mechanisms has diagnostic and therapeutic implications in AGs, and illustrates the functional complexity associated with rearrangements in cancer. </p>
Project description:Translocation events are frequent in cancer and may create chimeric fusions or ‘regulatory rearrangements’ that drive oncogene overexpression. Here we identify super-enhancer translocations that drive overexpression of the oncogenic transcription factor MYB as a recurrent theme in adenoid cystic carcinoma (ACC). Whole-genome sequencing data and chromatin maps reveal distinct chromosomal rearrangements that juxtapose super-enhancers to the MYB locus. Chromosome conformation capture confirms that the translocated enhancers interact with the MYB promoter. Remarkably, MYB protein binds to the translocated enhancers, creating a positive feedback loop that sustains its expression. MYB also binds enhancers that drive different regulatory programs in alternate cell lineages in ACC, cooperating with TP63 in myoepithelial cells and a Notch program in luminal epithelial cells. Bromodomain inhibitors slow tumor growth in ACC primagraft models in vivo. Thus, our study identifies super-enhancer translocations that drive MYB expression and provides insight into downstream MYB functions in the alternate ACC lineages.
Project description:Translocation events are frequent in cancer and may create chimeric fusions or regulatory rearrangements that drive oncogene overexpression. Although regulatory rearrangements are increasingly recognized in hematopoietic and even solid tumors, the underlying mechanisms remain obscure. Here we identify super-enhancer translocations that drive overexpression of the oncogenic transcription factor MYB as a unifying theme in adenoid cystic carcinoma (ACC). Whole genome sequencing data and chromatin state maps for 13 primary tumors and xenografts reveal distinct chromosomal rearrangements that juxtapose super-enhancer clusters to the MYB locus. Chromosome conformation capture confirms that the translocated enhancers physically interact with the MYB promoter. Remarkably, the MYB product itself binds to the translocated enhancers, thus creating a positive feedback loop that sustains its own expression. MYB also binds a large number of active enhancers that drive opposing regulatory programs in alternate cell lineages in ACC. MYB cooperates with the transcription factor TP63 in the myoepithelial component of the tumors, but promotes a Notch program in the luminal epithelial component. Bromodomain inhibitors, which disrupt enhancer function, slow tumor growth in ACC primagraft models in vivo, but are ineffective against high grade tumors that harbor activating mutations in the Notch pathway. Thus, our study identifies super-enhancer translocations as a unifying feature of ACC, and provides insight into the mechanism by which sustained MYB overexpression drives alternate cell fates in this disease.
Processed ChIP-seq data is available on GEO under accession number GSE76465.
Project description:We studied the effect of small interfering RNA (siRNA)-mediated QKI depletion on global gene expression in human oligodendroglioma cells and astrocyte glioma cells
Project description:To identify factors involved in tumorigenicity of glioma-initiating cells (GICs), we compared gene expression in GIC-like cells with and without sox11 expression. We established sox11-expressing mouse glioma-initiating cell (GIC)-like cell line (NSCL61s), NSCL61s-sox11, which lost tumorigenicity when transplanted in vivo. We think that genes, which are differently expressed between NSCL61s and NSCL61s-sox11, would be new targets for glioma therapy.
Project description:The long noncoding RNA (lncRNA) Nuclear Enriched Abundant Transcript 1 (NEAT1) is a lncRNA involved in a variety of human cancers and diseases. The human NEAT1 gene produces two distinct isoforms, NEAT1 Long and NEAT1 Short, through alternative 3’ end formation. NEAT1 Long is an essential factor for nuclear paraspeckle formation, while the role of NEAT1 Short is poorly understood. Previous studies have often failed to distinctly detect the two NEAT1 isoforms and reported controversial NEAT1 dysregulation. Moreover, the molecular mechanisms which underlie the dysregulation of NEAT1 isoforms and their functional importance in tumorigenesis remain poorly characterized. We investigated whether usage of the proximal polyadenylation site (PAS) within the NEAT1 transcript is regulated to govern the biogenesis of NEAT1 isoforms in human glioma cells. We found differential dysregulation of NEAT1 isoforms in patient-derived human glioblastoma multiforme (GBM) stem cells. We further show deletion of the NEAT1 PAS reduced NEAT1 Short and increased NEAT1 Long. We identified the RNA binding protein QKI, a risk factor for glioma, facilitates the utilization of the NEAT1 PAS. We present evidence indicating the imbalance of NEAT1 isoforms correlates with transcriptomic pathway changes. We propose QKI-5 regulates NEAT1 isoform biogenesis through modulating the NEAT1 PAS in human glioma cells.
Project description:Members of the miR-200 family are critical gatekeepers of the epithelial state, restraining expression of pro-mesenchymal genes that drive epithelial-mesenchymal transition (EMT) and contribute to metastatic cancer progression. Here, we show that miR-200c and another epithelial-enriched miRNA, miR-375, exert widespread control of alternative splicing in cancer cells. This is achieved by their strong suppression of the RNA binding protein Quaking (QKI), which is required to mediate the splicing changes regulated by these miRNAs. During EMT, QKI-5 directly binds to and regulates hundreds of alternative splicing events and exerts pleiotropic effects, such as increasing cell migration and invasion and restraining tumour growth, without appreciably affecting mRNA levels. QKI-5 is both necessary and sufficient to direct EMT alternative splicing changes, and this splicing signature is broadly conserved across many epithelial-derived cancer types. Importantly, several actin cytoskeleton-associated genes are directly targeted both by QKI and miR-200c, revealing coordinated control of alternative splicing and mRNA abundance during EMT. These findings demonstrate the existence of a miR-200/miR-375/QKI axis that impacts cancer-associated epithelial cell plasticity through widespread control of alternative splicing. The purpose of the CLIP experiment was to determine direct targets of QKI.
Project description:• IGF2BP1 promotes leukemia stem cell phenotype by regulating HOXB4, MYB and ALDH1A1.• Inhibition of IGF2BP1 reduces leukemia tumorigenicity, and enhances leukemia cell death and differentiation.