Project description:Medulloblastoma (MB) is the most common malignant brain tumor. MB is a cerebellar tumor that occurs mostly in children between the ages of 3-7 years but also in adults. Human MBs are classified into four subgroups: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 (G3) and G4, each of which with distinct molecular signatures. SHH MBs with MYCN amplification and TP53 mutations and G3 MBs characterized by C-MYC (MYC) overexpression in ~17% of cases from gene amplification with stem like properties, are the most aggressive and least curable with current therapeutic regimen. Using an orthotopic transplant approach, we found that enforced expression of MYCN in cerebellar granule neural progenitors (CGNPs) from 5-7 days old Trp53-null mice induced SHH MBs after transfer in the cortices or cerebella of naive recipient mice. In contrast, overexpression of MYC induced G3 MBs. Because MYCN and MYC bind to the same E-box DNA sequences, we hypothesized that the difference between MYC and MYCN-induced gene expression and tumor identity might be due to their interaction with different partners in CGNPs. In this study, we investigated the role of the Myc interacting zinc finger protein 1 (MIZ1). We found that MIZ1 binds with higher affinity to MYC than to MYCN and that MIZ1 and MYC co-occupy thousands of promoters in G3 MB. Remarkably, enforced expression of a MYC mutant (MYCV394D) that no longer binds to MIZ1 in Trp53-null CGNPs or expression of wild type MYC in CGNPs that lack functional Miz1 resulted in massive changes of the resulting tumorâ??s transcriptional program. Tumors differed from both SHH and G3 medulloblastoma and had a later time of onset compared to MYC-driven G3 medulloblastoma. Our data demonstrate that interaction of MYC with MIZ1 is required for the development of G3 medulloblastoma. ChIP-Seq experiments for Miz1, c-Myc and NMyc from murine medulloblastoma material. Either sorted tumor cells (Miz1 and c-Myc) or spheres from tumor cells (Miz1 and NMyc) were used. Input-samples were sequenced as controls. RNA-Seq from G3 medulloblastomas after restoration of Atoh1 expression.
Project description:Medulloblastoma (MB) is the most common malignant brain tumor. MB is a cerebellar tumor that occurs mostly in children between the ages of 3-7 years but also in adults. Human MBs are classified into four subgroups: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 (G3) and G4, each of which with distinct molecular signatures. SHH MBs with MYCN amplification and TP53 mutations and G3 MBs characterized by C-MYC (MYC) overexpression in ~17% of cases from gene amplification with stem like properties, are the most aggressive and least curable with current therapeutic regimen. Using an orthotopic transplant approach, we found that enforced expression of MYCN in cerebellar granule neural progenitors (CGNPs) from 5-7 days old Trp53-null mice induced SHH MBs after transfer in the cortices or cerebella of naive recipient mice. In contrast, overexpression of MYC induced G3 MBs. Because MYCN and MYC bind to the same E-box DNA sequences, we hypothesized that the difference between MYC and MYCN-induced gene expression and tumor identity might be due to their interaction with different partners in CGNPs. In this study, we investigated the role of the Myc interacting zinc finger protein 1 (MIZ1). We found that MIZ1 binds with higher affinity to MYC than to MYCN and that MIZ1 and MYC co-occupy thousands of promoters in G3 MB. Remarkably, enforced expression of a MYC mutant (MYCV394D) that no longer binds to MIZ1 in Trp53-null CGNPs or expression of wild type MYC in CGNPs that lack functional Miz1 resulted in massive changes of the resulting tumor’s transcriptional program. Tumors differed from both SHH and G3 medulloblastoma and had a later time of onset compared to MYC-driven G3 medulloblastoma. Our data demonstrate that interaction of MYC with MIZ1 is required for the development of G3 medulloblastoma.
Project description:Medulloblastomas (MBs) are cerebellar tumors that can be classified into molecularly distinct subgroups that differ in pathology and prognosis. The mechanisms that underlie subgroup specification are largely unknown. While human SHH MBs express MYCN, Group3 (G3) MBs are associated with c-MYC (MYC) overexpression and often show metastasis that confers a poor prognosis. Although MYC proteins are thought to be functionally exchangeable, ectopic expression of Myc or N-myc in Trp53-/-;Cdkn2c-/- cerebellar granule neuron progenitors (GNPs) induces G3 and SHH MBs, respectively, demonstrating that each Myc protein has distinct biological properties. We now show that Myc and N-myc differ in their affinity to Miz1 and that Myc, but not N-myc, effectively recruits Miz1 to its target sites on chromatin. The interaction of Myc with Miz1 is required for the genesis of G3 MB. Myc suppresses ciliogenesis and “reprograms” the transcriptome of SHH-dependent GNPs to stem-like cells by repressing genes highly expressed in SHH MB via Miz1. Consistently, target genes of Myc/Miz1 are repressed in human G3 MBs but not in other MB subgroups. Collectively, the data show that the interaction of Myc with Miz1 is a defining hallmark of G3 MB development.
Project description:Medulloblastomas (MBs) are cerebellar tumors that can be classified into molecularly distinct subgroups that differ in pathology and prognosis. The mechanisms that underlie subgroup specification are largely unknown. While human SHH MBs express MYCN, Group3 (G3) MBs are associated with c-MYC (MYC) overexpression and often show metastasis that confers a poor prognosis. Although MYC proteins are thought to be functionally exchangeable, ectopic expression of Myc or N-myc in Trp53-/-;Cdkn2c-/- cerebellar granule neuron progenitors (GNPs) induces G3 and SHH MBs, respectively, demonstrating that each Myc protein has distinct biological properties. We now show that Myc and N-myc differ in their affinity to Miz1 and that Myc, but not N-myc, effectively recruits Miz1 to its target sites on chromatin. The interaction of Myc with Miz1 is required for the genesis of G3 MB. Myc suppresses ciliogenesis and âreprogramsâ the transcriptome of SHH-dependent GNPs to stem-like cells by repressing genes highly expressed in SHH MB via Miz1. Consistently, target genes of Myc/Miz1 are repressed in human G3 MBs but not in other MB subgroups. Collectively, the data show that the interaction of Myc with Miz1 is a defining hallmark of G3 MB development. In this study, we show that Myc and N-myc differ in their affinity for Miz1, and Myc/Miz1 interaction is required for Group3 medulloblastoma (MB). The gene expression profiles of these tumors were compared to our previously published Group3 MB model as well as SHH model of MB (Kawachi et al., 2012, Cancer Cell). Cerebellar granule neuron progenitors (GNPs) [dka220-222] from postnatal (P) 6 Math1-GFP;Trp53-/-;Cdkn2c-/-. For SHH medulloblastomas, [dka204-206] and [blm015-017 or dka050-dka051], spontaneous medulloblastomas from Cdkn2c-/-;Trp53Fl/Fl;Nestin-Cre (Kawachi et al., 2012, Cancer Cell) and Ptch1+/-;Cdkn2c-/- (Uziel et al., 2005, Genes Dev) were used, respectively. Myc- [dka201-203] and MycV394D (termed MycVD thereafter)- [bvo017-bvo023] tumors were from Trp53-/-;Cdkn2c-/- cerebella of P6-P7 pups. Myc/ÎPOZ tumors [bvo002-bvo006] were obtained from Trp5Fl/Fl;Miz1ÎPOZ/POZ;Nestin-Cre cerebella of P6-P7 pups.
Project description:The development of malignant melanoma is a highly complex process which is still poorly understood despite extensive research. A majority of human melanomas are found to express a handful of oncogenic proteins, such as mutant RAS and BRAF. However, these oncogenes are also found in nevi, and it is now a well-accepted fact that their expression alone leads to senescence. This renders the understanding of senescence escape mechanisms an important criterion to understand tumor development. Here, we describe the ability of the transcription factor MYC to drive the evasion of reactive oxygen stress-induced melanocyte senescence, caused by activated receptor tyrosine kinase signaling. Conversely, MIZ1, the growth suppressing interaction partner of MYC, is involved in mediating melanocyte senescence. Both, MYC overexpression and Miz1 knockdown led to a strong reduction of endogenous reactive oxygen species (ROS), DNA damage and senescence. We identified the cystathionase (CTH) gene product as mediator of the ROS-related MYC and MIZ1 effects. Blocking CTH enzymatic activity in MYC-overexpressing and Miz1 knockdown cells increased intracellular stress and senescence. Importantly, pharmacological inhibition of cystathionase in human melanoma cells also reconstituted senescence in many cell lines, and CTH knockdown reduced tumorigenic effects such as proliferation, H2O2 resistance and soft agar growth. Thus, we identified cystathionase as new MYC target gene with an important function in MYC-mediated senescence evasion. total samples analysed are 4
Project description:Deregulated expression of MYC is a driver of colorectal carcinogenesis, necessitating novel strategies to inhibit MYC function. The ubiquitin ligase HUWE1 (HECTH9, ARFBP1, MULE) associates with both MYC and the MYC-associated protein MIZ1. We show here that HUWE1 is required for growth of colorectal cancer cells in culture and in orthotopic xenograft models. Using high throughput screening, we identify small molecule inhibitors of HUWE1, which inhibit MYC-dependent transactivation in colorectal cancer cells, but not in stem and normal colon epithelial cells. Inhibition of HUWE1 stabilizes MIZ1. MIZ1 globally accumulates on MYC target genes and contributes to repression of MYC-activated target genes upon HUWE1 inhibition. Our data show that transcriptional activation by MYC in colon cancer cells requires the continuous degradation of MIZ1 and identify a novel principle that allows for inhibition of MYC function in tumor cells. MIZ1 and MYC ChIPseq experiments in HUWE1 inhibitor-treated Ls174T cells as well as RNAseq experiments in HUWE1- or MIZ1-depleted Ls174T cells after HUWE1 inhibitor treatment. Sequencing was performed on an Illumina Genome Analyzer IIx.
Project description:Oncogenic levels of Myc expression sensitize cells to multiple apoptotic stimuli and this protects long-lived organisms from cancer development. How cells discriminate physiological from supra-physiological levels of Myc is largely unknown. Here we show that induction of apoptosis by Myc in breast epithelial cells requires association of Myc with Miz1. Gene expression and ChIP-sequencing experiments show that oncogenic levels of Myc, but not of MycV394D, a point mutant that does not bind Miz1, recruit Miz1 to core promoters and enable binding of Myc/Miz1 complexes to low-affinity target sites, correlating with repression of a specific set of target genes. Repressed genes encode proteins involved in cell adhesion, migration and wound healing; their promoters are enriched for binding sites of the serum response (SRF) factor. Restoring SRF activity attenuates Myc-induced apoptosis in response to glutamine starvation, exposure to Trail and to DNA damage. We propose that supra-physiological levels of Myc engage Miz1 in repressive DNA binding complexes and suppress transcriptional progress. MIZ1, MYC-ER and MYC-ERVD ChIP-Seq with 10E2 and HC20 anti-ERalpha antibodies in MCF10A cells, performed on an Illumina IIx Genome Analyzer. Input sample is accessioned as GSM1423726.
Project description:Deregulated expression of MYC is a driver of colorectal carcinogenesis, necessitating novel strategies to inhibit MYC function. The ubiquitin ligase HUWE1 (HECTH9, ARFBP1, MULE) associates with both MYC and the MYC-associated protein MIZ1. We show here that HUWE1 is required for growth of colorectal cancer cells in culture and in orthotopic xenograft models. Using high throughput screening, we identify small molecule inhibitors of HUWE1, which inhibit MYC-dependent transactivation in colorectal cancer cells, but not in stem and normal colon epithelial cells. Inhibition of HUWE1 stabilizes MIZ1. MIZ1 globally accumulates on MYC target genes and contributes to repression of MYC-activated target genes upon HUWE1 inhibition. Our data show that transcriptional activation by MYC in colon cancer cells requires the continuous degradation of MIZ1 and identify a novel principle that allows for inhibition of MYC function in tumor cells.