Inactivation of Ezh2 upregulates Gfi1 and drives aggressive Myc-driven Group 3 medulloblastoma
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE84762 | GEO | 2017/03/01
SECONDARY ACCESSION(S): PRJNA331086
REPOSITORIES: GEO
Similar Datasets
Project description:The most aggressive of four medulloblastoma (MB) subgroups are cMyc-driven group 3 (G3) tumors, some of which overexpress EZH2, the histone H3K27 mono-, di-, and trimethylase of polycomb-repressive complex 2. Ezh2 has a context-dependent role in different cancers as an oncogene or tumor suppressor and retards tumor progression in a mouse model of G3 MB. Engineered deletions of Ezh2 in G3 MBs by gene editing nucleases accelerated tumorigenesis, whereas Ezh2 re-expression reversed attendant histone modifications and slowed tumor progression. Candidate oncogenic drivers suppressed by Ezh2 included Gfi1, a proto-oncogene frequently activated in human G3 MBs. Gfi1 disruption antagonized the tumor-promoting effects of Ezh2 loss; conversely, Gfi1 overexpression collaborated with Myc to bypass effects of Trp53 inactivation in driving MB progression in primary cerebellar neuronal progenitors. Although negative regulation of Gfi1 by Ezh2 may restrain MB development, Gfi1 activation can bypass these effects.
| S-EPMC5415387 | biostudies-literature
Project description:The most aggressive of four medulloblastoma (MB) subgroups are cMYC-driven Group 3 (G3) tumors, some of which overexpress EZH2, the histone H3K27 trimethylase of polycomb repressive complex-2. Yet, engineered deletions of Ezh2 in G3 MBs by gene editing nucleases accelerated tumorigenesis, whereas Ezh2 re-expression reversed attendant histone modifications and slowed tumor progression. Candidate oncogenic drivers upregulated following Ezh2 deletion included Gfi1, a proto-oncogene frequently activated in human G3 MBs. Gfi1 disruption antagonized the tumor promoting effects of Ezh2 loss; conversely, Gfi1 overexpression collaborated with Myc to bypass effects of Trp53 inactivation in primary cerebellar neuronal progenitors thereby driving MB progression. Although negative epigenetic regulation of Gfi1 by Ezh2 may restrain MB development, Gfi1 activation can bypass these effects.
2017-03-01 | GSE84761 | GEO
Project description:The most aggressive of four medulloblastoma (MB) subgroups are cMYC-driven Group 3 (G3) tumors, some of which overexpress EZH2, the histone H3K27 trimethylase of polycomb repressive complex-2. Yet, engineered deletions of Ezh2 in G3 MBs by gene editing nucleases accelerated tumorigenesis, whereas Ezh2 re-expression reversed attendant histone modifications and slowed tumor progression. Candidate oncogenic drivers upregulated following Ezh2 deletion included Gfi1, a proto-oncogene frequently activated in human G3 MBs. Gfi1 disruption antagonized the tumor promoting effects of Ezh2 loss; conversely, Gfi1 overexpression collaborated with Myc to bypass effects of Trp53 inactivation in primary cerebellar neuronal progenitors thereby driving MB progression. Although negative epigenetic regulation of Gfi1 by Ezh2 may restrain MB development, Gfi1 activation can bypass these effects.
2017-03-01 | GSE84462 | GEO
Project description:Inactivation of Ezh2 upregulates Gfi1 and drives aggressive Myc-driven Group 3 medulloblastoma
| PRJNA331086 | ENA
Project description:Gfi1 is a zinc-finger transcriptional repressor that plays an important role in hematopoiesis. When aberrantly activated, Gfi1 may function as a weak oncoprotein in the lymphoid system, but collaborates strongly with c-Myc in lymphomagenesis. The mechanism by which Gfi1 collaborates with c-Myc in lymphomagenesis is incompletely understood. We show here that Gfi1 augmented the expression of c-Myc protein in cells transfected with c-Myc expression constructs. The N-terminal SNAG domain and C-terminal ZF domains of Gfi1, but not its transcriptional repression and DNA binding activities, were required for c-Myc upregulation. We further show that Gfi1 overexpression led to reduced polyubiquitination and increased stability of c-Myc protein. Interestingly, the levels of endogenous c-Myc mRNA and protein were augmented upon Gfi1 overexpression, but reduced following Gfi1 knockdown or knockout, which was associated with a decline in the expression of c-Myc-activated target genes. Consistent with its role in the regulation of c-Myc expression, Gfi1 promoted Myc-driven cell cycle progression and proliferation. Together, these data reveal a novel mechanism by which Gfi1 augments the biological function of c-Myc and may have implications for understanding the functional collaboration between Gfi1 and c-Myc in lymphomagenesis.
| S-EPMC7554040 | biostudies-literature
Project description:EZH2 is overexpressed in poor-prognostic chronic lymphocytic leukaemia (CLL) cases, acting as an oncogene; however, thus far, the EZH2 target genes in CLL have not been disclosed. In this study, using ChIP-sequencing, we identified EZH2 and H3K27me3 target genes in two prognostic subgroups of CLL with distinct prognosis and outcome, i.e., cases with unmutated (U-CLL, n = 6) or mutated IGHV genes (M-CLL, n = 6). While the majority of oncogenic pathways were equally enriched for EZH2 target genes in both prognostic subgroups, PI3K pathway genes were differentially bound by EZH2 in U-CLL versus M-CLL. The occupancy of EZH2 for selected PI3K pathway target genes was validated in additional CLL samples (n = 16) and CLL cell lines using siRNA-mediated EZH2 downregulation and ChIP assays. Intriguingly, we found that EZH2 directly binds to the IGF1R promoter along with MYC and upregulates IGF1R expression in U-CLL, leading to downstream PI3K activation. By investigating an independent CLL cohort (n = 96), a positive correlation was observed between EZH2 and IGF1R expression with higher levels in U-CLL compared to M-CLL. Accordingly, siRNA-mediated downregulation of either EZH2, MYC or IGF1R and treatment with EZH2 and MYC pharmacological inhibitors in the HG3 CLL cell line induced a significant reduction in PI3K pathway activation. In conclusion, we characterize for the first time EZH2 target genes in CLL revealing a hitherto unknown implication of EZH2 in modulating the PI3K pathway in a non-canonical, PRC2-independent way, with potential therapeutic implications considering that PI3K inhibitors are effective therapeutic agents for CLL.
| S-EPMC6773411 | biostudies-literature
Project description:BACKGROUND:MYC amplification or overexpression is common in Group 3 medulloblastoma and is associated with the worst prognosis. Recently, protein arginine methyl transferase (PRMT) 5 expression has been closely associated with aberrant MYC function in various cancers, including brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in medulloblastoma have not been explored. Here, we report the role of PRMT5 as a novel regulator of MYC and implicate PRMT5 as a potential therapeutic target in MYC-driven medulloblastoma. METHODS:Expression and association between PRMT5 and MYC in primary medulloblastoma tumors were investigated using publicly available databases. Expression levels of PRMT5 protein were also examined using medulloblastoma cell lines and primary tumors by western blotting and immunohistochemistry, respectively. Using MYC-driven medulloblastoma cells, we examined the physical interaction between PRMT5 and MYC by co-immunoprecipitation and co-localization experiments. To determine the functional role of PRMT5 in MYC-driven medulloblastoma, PRMT5 was knocked-down in MYC-amplified cells using siRNA and the consequences of knockdown on cell growth and MYC expression/stability were investigated. In vitro therapeutic potential of PRMT5 in medulloblastoma was also evaluated using a small molecule inhibitor, EPZ015666. RESULTS:We observed overexpression of PRMT5 in MYC-driven primary medulloblastoma tumors and cell lines compared to non-MYC medulloblastoma tumors and adjacent normal tissues. We also found that high expression of PRMT5 is inversely correlated with patient survival. Knockdown of PRMT5 using siRNA in MYC-driven medulloblastoma cells significantly decreased cell growth and MYC expression. Mechanistically, we found that PRMT5 physically associated with MYC by direct protein-protein interaction. In addition, a cycloheximide chase experiment showed that PRMT5 post-translationally regulated MYC stability. In the context of therapeutics, we observed dose-dependent efficacy of PRMT5 inhibitor EPZ015666 in suppressing cell growth and inducing apoptosis in MYC-driven medulloblastoma cells. Further, the expression levels of PRMT5 and MYC protein were downregulated upon EPZ015666 treatment. We also observed a superior efficacy of this inhibitor against MYC-amplified medulloblastoma cells compared to non-MYC-amplified medulloblastoma cells, indicating specificity. CONCLUSION:Our results reveal the regulation of MYC oncoprotein by PRMT5 and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven medulloblastoma.
| S-EPMC6836472 | biostudies-literature
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.
| S-EPMC3285431 | biostudies-literature
Project description:A subset of group 3 medulloblastoma frequently harbors amplification or overexpression of MYC lacking additional focal aberrations, yet it remains unclear whether MYC overexpression alone can induce tumorigenesis and which cells give rise to these tumors. Here, we showed that astrocyte progenitors in the early postnatal cerebellum were susceptible to transformation by MYC. The resulting tumors specifically resembled human group 3 medulloblastoma based on histology and gene-expression profiling. Gene-expression analysis of MYC-driven medulloblastoma cells revealed altered glucose metabolic pathways with marked overexpression of lactate dehydrogenase A (LDHA). LDHA abundance correlated positively with MYC expression and was associated with poor prognosis in human group 3 medulloblastoma. Inhibition of LDHA significantly reduced growth of both mouse and human MYC-driven tumors but had little effect on normal cerebellar cells or SHH-associated medulloblastoma. By generating a new mouse model, we demonstrated for the first time that astrocyte progenitors can be transformed by MYC and serve as the cells of origin for group 3 medulloblastoma. Moreover, we identified LDHA as a novel, specific therapeutic target for this devastating disease. SIGNIFICANCE: Insights from a new model identified LDHA as a novel target for group 3 medulloblastoma, paving the way for the development of effective therapies against this disease.
| S-EPMC6467710 | biostudies-literature
Project description:BackgroundMedulloblastoma (MB) patients with MYC oncogene amplification or overexpression exhibit extremely poor clinical outcomes and respond poorly to current therapies. Epigenetic deregulation is very common in MYC-driven MB. The bromodomain extra-terminal (BET) proteins and histone deacetylases (HDACs) are epigenetic regulators of MYC transcription and its associated tumorigenic programs. This study aimed to investigate the therapeutic potential of inhibiting the BET proteins and HDACs together in MB.MethodsUsing clinically relevant BET inhibitors (JQ1 or OTX015) and a pan-HDAC inhibitor (panobinostat), we evaluated the effects of combined inhibition on cell growth/survival in MYC-amplified MB cell lines and xenografts and examined underlying molecular mechanism(s).ResultsCo-treatment of JQ1 or OTX015 with panobinostat synergistically suppressed growth/survival of MYC-amplified MB cells by inducing G2 cell cycle arrest and apoptosis. Mechanistic investigation using RNA-seq revealed that co-treatment of JQ1 with panobinostat synergistically modulated global gene expression including MYC/HDAC targets. SYK and MSI1 oncogenes were among the top 50 genes synergistically downregulated by JQ1 and panobinostat. RT-PCR and western blot analyses confirmed that JQ1 and panobinostat synergistically inhibited the mRNA and protein expression of MSI1/SYK along with MYC expression. Reduced SYK/MSI expression after BET (specifically, BRD4) gene-knockdown further confirmed the epigenetic regulation of SYK and MSI1 genes. In addition, the combination of OTX015 and panobinostat significantly inhibited tumor growth in MYC-amplified MB xenografted mice by downregulating expression of MYC, compared to single-agent therapy.ConclusionsTogether, our findings demonstrated that dual-inhibition of BET and HDAC proteins of the epigenetic pathway can be a novel therapeutic approach against MYC-driven MB.
| S-EPMC9650837 | biostudies-literature