Project description:Transcriptional cancer subtypes which correlate with traits such as tumor growth, drug sensitivity or the chances of relapse and metastasis, have been described for several malignancies. The core regulatory circuits (CRCs) defining these subtypes are established by chromatin super enhancers (SEs) driving key transcription factors (TFs) specific for the particular cell state. In neuroblastoma (NB), one of the most frequent solid pediatric cancer entities, two major SE-directed molecular subtypes have been described: A more lineage-committed adrenergic (ADRN) and a mesenchymal (MES) subtype. Here, we found that a small isoxazole molecule (ISX), a frequently used pro-neural drug, reprogrammed SE activity and switched NB cells from an ADRN subtype towards a growth-retarded MES-like state. The MES-like state shared strong transcriptional overlap with ganglioneuroma (GN), a benign and highly differentiated tumor of the neural crest. Mechanistically, ISX suppressed chromatin binding of N-MYC, a CRC-amplifying transcription factor, resulting in loss of key ADRN subtype-enriched components such as N-MYC itself, PHOX2B and ALK, while concomitently, MES subtype markers were induced. Globally, ISX treatment installed a chromatin accessibility landscape typically associated with low risk NB. In summary, we provide evidence that CRCs and cancer subtype reprogramming might be amenable to future therapeutic targeting.
Project description:Alterations in distal regulatory elements that control gene expression underlie many diseases, including cancer. Epigenomic analyses of normal and diseased cells have produced correlative predictions for connections between dysregulated enhancers and target genes involved in pathogenesis. However, with few exceptions, these predicted cis-regulatory circuits remain untested. Here, we dissect cis-regulatory circuits that lead to overexpression of NEK6, a mitosis-associated kinase, in human B cell lymphoma. We find that only a minor subset of predicted enhancers is required for NEK6 expression. Indeed, an annotated super-enhancer is dispensable for NEK6 overexpression and for maintaining the architecture of a B cell-specific regulatory hub. A CTCF cluster serves as a chromatin and architectural boundary to block communication of the NEK6 regulatory hub with neighboring genes. Our findings emphasize that validation of predicted cis-regulatory circuits and super-enhancers is needed to prioritize transcriptional control elements as therapeutic targets.
Project description:Alterations in distal regulatory elements that control gene expression underlie many diseases, including cancer. Epigenomic analyses of normal and diseased cells have produced correlative predictions for connections between dysregulated enhancers and target genes involved in pathogenesis. However, with few exceptions, these predicted cis-regulatory circuits remain untested. Here, we dissect cis-regulatory circuits that lead to overexpression of NEK6, a mitosis-associated kinase, in human B cell lymphoma. We find that only a minor subset of predicted enhancers is required for NEK6 expression. Indeed, an annotated super-enhancer is dispensable for NEK6 overexpression and for maintaining the architecture of a B cell-specific regulatory hub. A CTCF cluster serves as a chromatin and architectural boundary to block communication of the NEK6 regulatory hub with neighboring genes. Our findings emphasize that validation of predicted cis-regulatory circuits and super-enhancers is needed to prioritize transcriptional control elements as therapeutic targets.
Project description:Clusters of enhancers called super-enhancers are associated with gene activation. Broad trimethyl histone H3 lysine 4 (H3K4me3) often defines actively transcribed tumor suppressor genes. However, how these epigenetic signatures are regulated for tumor suppression is poorly understood. Here, we show that brain-specific knockout of the H3K4 methyltransferase MLL4 (aka KMT2D) in mice spontaneously induces cerebellar tumors in brain while indirectly increasing expression of oncogenic programs, such as Ras activators and Notch pathway components. Mll4 loss caused widespread impairment of super-enhancers and broad H3K4me3. Notably, Mll4 loss reduced super-enhancer and broad H3K4me3 signals in tumor suppressor genes co-marked by both signatures, including Dnmt3a and Bcl6. MLL4 upregulates DNMT3A-mediated DNA methylation to downregulate expression of Ras activators and increases Bcl6 expression to suppress the Notch pathway. These findings suggest an unanticipated epigenetic tumor-suppressive mechanism in which MLL4 is required for establishing super-enhancers and broad H3K4me3 for anti-tumor programs in normal cells.
Project description:Multiple Myeloma (MM) is the second most prevalent blood cancer (10%) after non-Hodgkin's lymphoma and represents approximately 1% of all cancers and 2% of all cancer deaths. MM is a complex disease characterized by numerous genetic alterations and recent mRNA profiling studies have attempted to subclassify the disease to build pathogenetic and prognostic models Correct classification of cancer patients into subtypes is a prerequisite for acute diagnosis and effective treatment. Here we use high accuracy, quantitative proteomics to segregate cancer subtypes directly at the level of expressed proteins. Multiple myeloma is a heterogeneous disease in its initial clinical features as well as its outcome. We investigated two subtypes of Multiple Myeloma: multiple myeloma associated with t(4;14) chromosomal translocation as well as t(4;14)-negative MM subtype. The t(4;14) translocation, found in 15% of multiple myeloma cases, indicates a poor prognosis. Super-SILAC mix was combined of cell lysates from 8 diverse cell lines labelled with heavy amino acids (Lys8 and Arg10). The Super-SILAC library is mixed with samples (lysates), and quantitative mass spectrometric analysis is performed using a setup consisting of LC and on a linear ion trap Orbitrap mass spectrometer with high mass accuracy at the MS and MS/MS levels. This way we have analysed 20 patient samples from present MM. Shotgun proteomic analysis yielded a proteome of more than 5300 quantified proteins overall (3000 on an average per individual sample). High accuracy of quantification allowed robust separation of subtypes by hierarchical clustering on the protein level.
Project description:Chromatin regulators have become highly attractive targets for cancer therapy, yet many of these regulators are expressed in a broad range of healthy cells and contribute generally to gene expression. An important conundrum has thus emerged: how can inhibition of a general regulator of gene expression produce selective effects at specific oncogenes? Here we investigate how inhibition of the transcriptional coactivator BRD4 (Bromodomain containing 4) leads to selective inhibition of disease-critical oncogenes in a highly malignant blood cancer, multiple myeloma (MM). We found that BRD4 generally occupies the promoter elements of active genes together with the Mediator coactivator, but remarkably high levels of these two coactivator proteins were associated with a small set of exceptionally large enhancers. These super-enhancers are associated with genes that feature prominently in MM biology, including the MYC oncogene. Treatment of MM tumor cells with the BET-bromodomain inhibitor JQ1 led to preferential loss of BRD4 at super-enhancers and consequent transcription elongation defects that preferentially impact genes with super-enhancers, including the c-MYC oncogene. Super-enhancers were found at key oncogenic drivers in many other tumor cells. Thus, super-enhancers can regulate oncogenic drivers in tumor cells, which in some cells can be preferentially disrupted by BRD4 inhibition, which in turn contributes to the selective transcriptional effects observed at these oncogenes. These observations have implications for the discovery of novel cancer therapeutics directed at components of super-enhancers in diverse tumor types. ChIP-Seq for chromatin regulators and RNA Polymerase II in multiple myeloma, glioblastoma multiforme, and small cell lung cancer
Project description:Chromatin regulators have become highly attractive targets for cancer therapy, yet many of these regulators are expressed in a broad range of healthy cells and contribute generally to gene expression. An important conundrum has thus emerged: how can inhibition of a general regulator of gene expression produce selective effects at specific oncogenes? Here we investigate how inhibition of the transcriptional coactivator BRD4 (Bromodomain containing 4) leads to selective inhibition of disease-critical oncogenes in a highly malignant blood cancer, multiple myeloma (MM). We found that BRD4 generally occupies the promoter elements of active genes together with the Mediator coactivator, but remarkably high levels of these two coactivator proteins were associated with a small set of exceptionally large enhancers. These super-enhancers are associated with genes that feature prominently in MM biology, including the MYC oncogene. Treatment of MM tumor cells with the BET-bromodomain inhibitor JQ1 led to preferential loss of BRD4 at super-enhancers and consequent transcription elongation defects that preferentially impact genes with super-enhancers, including the c-MYC oncogene. Super-enhancers were found at key oncogenic drivers in many other tumor cells. Thus, super-enhancers can regulate oncogenic drivers in tumor cells, which in some cells can be preferentially disrupted by BRD4 inhibition, which in turn contributes to the selective transcriptional effects observed at these oncogenes. These observations have implications for the discovery of novel cancer therapeutics directed at components of super-enhancers in diverse tumor types. Gene expression profiling in multiple myeloma cells after BET-Bromodomain inhibition with JQ1