Mapping MYC binding sites in ONS76 medulloblastoma cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE186834 | GEO | 2022/08/22
REPOSITORIES: GEO
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Project description:Quiescent/slowly circling tumor cells present a clinical challenge due to their ability to evade treatement. Recent studies have demonstrated that quiescent/slow circling tumor cells hijack embryonic growth arrest mechanisms and consequently resist chemotherapy. Significantly, earlier studies established that high levels of SOX2 in both fetal and tumor cells restrict cell proliferation and induce a slowly cycling state. However, the mechanisms through which elevated SOX2 levels inhibit tumor cell proliferation have not been identified. To identify common mechanisms through which SOX2 elevation restricts tumor cell proliferation, we performed RNA-seq using ONS76 medulloblastoma and LNCaP prostate tumor cells engineered to express SOX2 from an inducible promoter. SOX2 elevation in both cell lines significantly downregulated MYC target genes. Consistent with these findings, elevating SOX2 in five cell lines representing three different human cancer types decreases MYC mRNA and protein levels. Importantly, the expression of a dominant-negative MYC variant, omomyc, recapitulated many of the effects of SOX2 on proliferation, cell cycle, and gene expression. As predicted by our Gene Ontology analysis, elevating SOX2 decreases biosynthetic activity, in particular protein translation. We also demonstrate that rescuing MYC activity in the context of elevated SOX2 induces cell death, indicating that the downregulation of MYC is a critical mechanistic step necessary to maintain survival in the slowly cycling state induced by elevated SOX2. Altogether, our findings uncover a novel SOX2: MYC signaling axis and provide novel insights into the molecular mechanisms through which SOX2 elevation induces a slowly cycling proliferative state.
2022-08-03 | GSE190936 | GEO
Project description:MYC genes have both essential roles during normal development and exert oncogenic functions during tumorigenesis. Expression of a dominant-negative allele of MYC, termed OmoMYC, can induce rapid tumor regression in mouse models with little toxicity for normal tissues. How OmoMYC discriminates between physiological and oncogenic functions of MYC is unclear. We have solved the crystal structure of OmoMYC and show that it forms a stable homodimer and as such recognizes DNA in the same manner as the MYC/MAX heterodimer. OmoMYC attenuates both MYC-dependent activation and repression by competing with MYC/MAX for binding to chromatin, effectively lowering MYC/MAX occupancy at its cognate binding sites. OmoMYC causes the largest decreases in promoter occupancy and changes in expression on genes that are invaded by oncogenic MYC levels. A signature of OmoMYC-regulated genes defines subgroups with high MYC levels in multiple tumor entities and identifies novel targets for the eradication of MYC-driven tumors.
2016-10-18 | GSE77328 | GEO
Project description:Deregulation of N-myc is a leading cause of malignant brain tumors in children. To target N-myc-driven medulloblastoma, most research has focused on identifying genomic alterations or on the analysis of the medulloblastoma transcriptome. Here, we have broadly characterized the translatome of medulloblastoma and shown that N-myc unexpectedly drives selective translation of transcripts that promote protein homeostasis. Cancer cells are constantly exposed to proteotoxic stress associated with alterations in protein production or folding. It remains poorly understood how cancers cope with proteotoxic stress to promote their growth. Here, our data unexpectedly revealed that N-myc regulates the expression of specific components (~5%) of the protein folding machinery at the translational level through the major cap binding protein, eukaryotic initiation factor eIF4E. Reducing eIF4E levels in mouse models of medulloblastoma blocked tumorigenesis. Importantly, targeting Hsp70, a protein folding chaperone translationally regulated by N-myc, suppressed tumor growth in mouse and human medulloblastoma xenograft models. These findings reveal a previously hidden molecular program that promotes medulloblastoma formation and identify new therapies that may have impact in the clinic.
2022-10-18 | GSE215298 | GEO
Project description:Medulloblastoma (MB) is the most common malignant brain tumor in children. Patients whose tumors exhibit overexpression or amplification of the MYC oncogene (c-MYC) usually have an extremely poor prognosis, but there are no animal models of this subtype of the disease. Here we show that cerebellar stem cells expressing Myc and mutant Trp53 (p53) generate aggressive tumors following orthotopic transplantation. These tumors consist of large, pleiomorphic cells and resemble human MYC-driven MB at a molecular level. Notably, antagonists of PI3K/mTOR signaling, but not Hedgehog signaling, inhibit growth of tumor cells. These findings suggest that cerebellar stem cells can give rise to MYC-driven MB, and identify a novel model that can be used to test therapies for this devastating disease. To gain insight into the pathways that control growth of MYC-driven MB, we compared gene expression profiles of murine Myc/DNp53 (MP) tumor cells to those of freshly isolated cerebellar stem cells (Prom1+Lin- cells) and of tumors from Ptch1 mutant mice (a model for Sonic Hedgehog-associated MB). RNA was isolated from stem cells and tumor cells using the RNAqueous kit (Ambion). RNA was labeled and hybridized to Affymetrix Mouse Genome 430 2.0 arrays. 19 mouse cell samples (stem cells and tumor cells) were analyzed. There are four groups of samples, three with five biological replicates and the last with four (one outlier was removed). To gain insight into the mechanisms of transformation into tumors, we compared the gene expression profiles of MP tumor cells derived from stem cells (Myc/DNp53-infected Prom1+Lin- cells, designated MP-pl) or progenitors (Myc/DNp53-infected Prom1+ cells, designated MP-p) to gene expression profiles of uninfected stem cells (designated NSC) and profiles from a distinct model of medulloblastoma, the patched mutant mouse (designated ptch1).
2011-12-05 | E-GEOD-34126 | biostudies-arrayexpress
Project description:MYC deregulation is common in human cancer and has a role in sustaining the aggressive cancer stem cell populations. MYC mediates a broad transcriptional response controlling normal biological programs but its activity is not clearly understood. We address MYC function in cancer stem cells through the inducible expression of Omomyc – a MYC derived polypeptide interfering with MYC activity – taking as model the most lethal brain tumor, glioblastoma. Omomyc bridles the key cancer stem-like cell features and affects tumor microenvironment, inhibiting angiogenesis. This occurs because Omomyc interferes with proper Myc localization and binds to DNA, with a preference for sites previously occupied by MYC. This is accompanied by (leads to) selective repression of master transcription factors for glioblastoma stem-like cell identity like POU3F2, SOX2, and OLIG2, upregulation of effectors of tumor suppression and differentiation such as PTEN, ID4, MIAT, and modulation of the expression of microRNAs that target molecules implicated in glioblastoma growth and invasion like EGFR and ZEB1. Data support a novel view of MYC as a network stabilizer that strengthens the regulatory nodes of the gene expression programs controlling cell phenotype and highlight Omomyc as model molecule for targeting cancer stem cells.
2016-11-16 | GSE86511 | GEO
Project description:Group 3 medulloblastoma is one of the most aggressive types of childhood brain tumors. Roughly 30% of cases carry genetic alterations in MYC, SMARCA4, or both genes combined. While overexpression of MYC has previously been shown to drive medulloblastoma formation in mice, the functional significance of SMARCA4 mutations and their suitability as a therapeutic target remain largely unclear. To address this issue, we combined overexpression of MYC with a loss of SMARCA4 in granule cell precursors. Both alterations did not increase proliferation of granule cell precursors in vitro. However, combined MYC overexpression and SMARCA4 loss successfully induced tumor formation in vivo after orthotopic transplantation in recipient mice. Resulting tumors displayed anaplastic histology and exclusively consisted of SMARCA4 negative cells although a mixture of recombined and non-recombined cells was injected. These observations provide first evidence for a tumor-promoting role of a SMARCA4 deficiency in the development of medulloblastoma. In comparing the transcriptome of tumors to the cells of origin and an established Sonic Hedgehog medulloblastoma model, we gathered first hints on deregulated gene expression that could be specifically involved in SMARCA4/MYC driven tumorigenesis. Finally, an integration of RNA sequencing and DNA methylation data of murine tumors with human samples revealed a high resemblance to human Group 3 medulloblastoma on the molecular level. Altogether, the development of SMARCA4-deficient medulloblastomas in mice paves the way to deciphering the role of frequently occurring SMARCA4 alterations in Group 3 medulloblastoma with the perspective to explore targeted therapeutic options.
2023-09-26 | GSE235924 | GEO
Project description:Group 3 medulloblastoma is one of the most aggressive types of childhood brain tumors. Roughly 30% of cases carry genetic alterations in MYC, SMARCA4, or both genes combined. While overexpression of MYC has previously been shown to drive medulloblastoma formation in mice, the functional significance of SMARCA4 mutations and their suitability as a therapeutic target remain largely unclear. To address this issue, we combined overexpression of MYC with a loss of SMARCA4 in granule cell precursors. Both alterations did not increase proliferation of granule cell precursors in vitro. However, combined MYC overexpression and SMARCA4 loss successfully induced tumor formation in vivo after orthotopic transplantation in recipient mice. Resulting tumors displayed anaplastic histology and exclusively consisted of SMARCA4 negative cells although a mixture of recombined and non-recombined cells was injected. These observations provide first evidence for a tumor-promoting role of a SMARCA4 deficiency in the development of medulloblastoma. In comparing the transcriptome of tumors to the cells of origin and an established Sonic Hedgehog medulloblastoma model, we gathered first hints on deregulated gene expression that could be specifically involved in SMARCA4/MYC driven tumorigenesis. Finally, an integration of RNA sequencing and DNA methylation data of murine tumors with human samples revealed a high resemblance to human Group 3 medulloblastoma on the molecular level. Altogether, the development of SMARCA4-deficient medulloblastomas in mice paves the way to deciphering the role of frequently occurring SMARCA4 alterations in Group 3 medulloblastoma with the perspective to explore targeted therapeutic options.
2023-09-26 | GSE235625 | GEO
Project description:MYC is a driver oncogene in many cancers. Inhibition of MYC promises high therapeutic potential, but specific MYC inhibitors remain unavailable for clinical use. Previous studies suggest that MYC amplified Medulloblastoma cells are vulnerable to HDAC inhibition. Using co-immunoprecipitation, mass spectrometry and ChIP-sequencing we show that HDAC2 is a cofactor of MYC in MYC amplified primary medulloblastoma and cell lines. The MYC-HDAC2 complex is bound to genes defining the MYC-dependent transcriptional profile. Class I HDAC inhibition leads to stabilization and reduced DNA binding of MYC protein inducing a down-regulation of MYC activated genes (MAGs) and up-regulation of MYC repressed genes (MRGs). MAGs and MRGs are characterized by opposing biological functions and distinct E-box distribution. We conclude that MYC and HDAC2 (class I) are localized in a complex in MYC amplified medulloblastoma and drive a MYC-specific transcriptional program, which is reversed by the class I HDAC inhibitor entinostat. Thus, the development of HDAC inhibitors for treatment of MYC amplified medulloblastoma should include HDAC2 in its profile in order to directly target MYC´s trans-activating and trans-repressing function.
2020-09-01 | GSE143384 | GEO
Project description:MYC is a driver oncogene in many cancers. Inhibition of MYC promises high therapeutic potential, but specific MYC inhibitors remain unavailable for clinical use. Previous studies suggest that MYC amplified Medulloblastoma cells are vulnerable to HDAC inhibition. Using co-immunoprecipitation, mass spectrometry and ChIP-sequencing we show that HDAC2 is a cofactor of MYC in MYC amplified primary medulloblastoma and cell lines. The MYC-HDAC2 complex is bound to genes defining the MYC-dependent transcriptional profile. Class I HDAC inhibition leads to stabilization and reduced DNA binding of MYC protein inducing a down-regulation of MYC activated genes (MAGs) and up-regulation of MYC repressed genes (MRGs). MAGs and MRGs are characterized by opposing biological functions and distinct E-box distribution. We conclude that MYC and HDAC2 (class I) are localized in a complex in MYC amplified medulloblastoma and drive a MYC-specific transcriptional program, which is reversed by the class I HDAC inhibitor entinostat. Thus, the development of HDAC inhibitors for treatment of MYC amplified medulloblastoma should include HDAC2 in its profile in order to directly target MYC´s trans-activating and trans-repressing function.
2020-09-01 | GSE143379 | GEO
Project description:MYC is a driver oncogene in many cancers. Inhibition of MYC promises high therapeutic potential, but specific MYC inhibitors remain unavailable for clinical use. Previous studies suggest that MYC amplified Medulloblastoma cells are vulnerable to HDAC inhibition. Using co-immunoprecipitation, mass spectrometry and ChIP-sequencing we show that HDAC2 is a cofactor of MYC in MYC amplified primary medulloblastoma and cell lines. The MYC-HDAC2 complex is bound to genes defining the MYC-dependent transcriptional profile. Class I HDAC inhibition leads to stabilization and reduced DNA binding of MYC protein inducing a down-regulation of MYC activated genes (MAGs) and up-regulation of MYC repressed genes (MRGs). MAGs and MRGs are characterized by opposing biological functions and distinct E-box distribution. We conclude that MYC and HDAC2 (class I) are localized in a complex in MYC amplified medulloblastoma and drive a MYC-specific transcriptional program, which is reversed by the class I HDAC inhibitor entinostat. Thus, the development of HDAC inhibitors for treatment of MYC amplified medulloblastoma should include HDAC2 in its profile in order to directly target MYC´s trans-activating and trans-repressing function.
2020-09-01 | GSE143376 | GEO