Project description:Rhabdomyosarcoma (RMS) is one of the most common pediatric soft-tissue cancer. Previously, we discovered a gene fusion, MARS-AVIL formed by chromosomal inversion in RMS. Suspecting that forming a fusion with a housekeeping gene may be one of the mechanisms to dysregulate an oncogene, we investigated AVIL expression and its role in RMS. We first showed that MARS-AVIL translates into an in-frame fusion protein, which is critical for the RMS cell tumorigenesis. Besides forming a gene fusion with the housekeeping gene, MARS, the AVIL locus is often amplified, and its RNA and protein expression is overexpressed in the majority of RMSs. Tumors with AVIL dysregulation exhibit evidence of oncogene addiction: silencing MARS-AVIL in cells harboring the fusion, or silencing AVIL in cells with AVIL overexpression, nearly eradicated the cells in culture, as well as inhibited in vivo xenograft growth in mice. Conversely, gain-of-function manipulations of AVIL led to increased cell growth and migration, enhanced foci formation in mouse fibroblasts, and most importantly transformed mesenchymal stem cells in vitro and in vivo. Mechanistically, AVIL seems to serve as a converging node functioning upstream of two oncogenic pathways, PAX3-FOXO1 and RAS, thus connecting two types of RMS associated with these pathways. Interestingly, AVIL is overexpressed in other sarcoma cells as well, and its expression correlates with clinical outcomes, with higher levels of AVIL expression being associated with worse prognosis. AVIL is a bona fide oncogene in RMS, and RMS cells are addicted to its activity.
Project description:Tumors driven by activation of the transcription factor Myc generally show oncogene addiction. However, the gene-expression programs that depend upon sustained Myc activity in those tumors remain unknown. We have addressed this issue in a model of liver carcinoma driven by a reversible tet-Myc transgene, combining gene expression profiling with the mapping of Myc and RNA Polymerase II on chromatin. Switching off the oncogene in advanced carcinomas revealed that Myc is required for the continuous activation and repression of distinct sets of genes, constituting no more than half of those deregulated during tumor progression, and an even smaller subset of all Myc-bound genes. We further showed that a Myc mutant unable to associate with the co-repressor protein Miz1 is defective in the initiation of liver tumorigenesis. Altogether, our data provide the first detailed analysis of a Myc-dependent transcriptional program in a fully developed carcinoma, revealing that the critical effectors of Myc in tumor maintenance must be included within defined subsets (ca. 1,300 each) of activated and repressed genes.
Project description:Tumors driven by activation of the transcription factor Myc generally show oncogene addiction. However, the gene-expression programs that depend upon sustained Myc activity in those tumors remain unknown. We have addressed this issue in a model of liver carcinoma driven by a reversible tet-Myc transgene, combining gene expression profiling with the mapping of Myc and RNA Polymerase II on chromatin. Switching off the oncogene in advanced carcinomas revealed that Myc is required for the continuous activation and repression of distinct sets of genes, constituting no more than half of those deregulated during tumor progression, and an even smaller subset of all Myc-bound genes. We further showed that a Myc mutant unable to associate with the co-repressor protein Miz1 is defective in the initiation of liver tumorigenesis. Altogether, our data provide the first detailed analysis of a Myc-dependent transcriptional program in a fully developed carcinoma, revealing that the critical effectors of Myc in tumor maintenance must be included within defined subsets (ca. 1,300 each) of activated and repressed genes.
Project description:The suppression of oncogenic levels of MYC is sufficient to induce sustained tumor regression associated with proliferative arrest, differentiation, cellular senescence and/or apoptosis, a phenomenon known as oncogene addiction. However, after prolonged inactivation of MYC in a conditional transgenic mouse model of Em-tTA/tetO-MYC T-acute lymphomablastic lymphoma (T-ALL), some of the tumors recur, recapitulating what is frequently observed in human tumors in response to targeted therapies. Here we report that these recurring lymphomas express high levels of either transgenic or endogenous Myc suggesting that tumors continue to be addicted to oncogenic levels of MYC. Many of the recurring lymphomas (76%) harbored mutations in the tetracycline transactivator (tTA) resulting in expression of the MYC transgene even in the presence of doxycycline. Many of the remaining recurring tumors expressed high levels of endogenous Myc which was in some cases associated with a genomic rearrangement of the endogenous Myc locus or overexpression of Notch1. Gene expression profiling confirmed that the primary and recurring tumors have highly similar transcriptomes. Importantly, shRNA-mediated suppression of the high levels of MYC in recurring tumors elicited both suppression of proliferation and increased apoptosis confirming that these tumors remain oncogene addicted. These results suggest that tumors caused by MYC overexpression remain addicted to high levels of expression of this oncogene. 13 samples, no replicates included
Project description:Oncogene addiction provides important therapeutic opportunities for precision oncology treatment strategies. To date the cellular circuitries associated with driving oncoproteins, which eventually establish the phenotypic manifestation of oncogene addiction remain largely unexplored. We employed a targeted mass spectrometry approach to systematically explore alterations in 116 phosphosites related to oncogene signaling and its intersection with the DDR following inhibition of the addicting oncogene alone or in combination with irradiation in MET-, EGFR-, ALK- or BRAF (V600)-positive cancer models and ex vivo non-small cell lung cancer patient organotypic cultures. We identified an ‘oncogene addiction phosphorylation signature’ (OAPS) consisting of 8 protein phosphorylations (ACLY S455, IF4B S422, IF4G1 S1231, LIMA1 S490, MYCN S62, NCBP1 S22, P3C2A S259 and TERF2 S365) that are significantly suppressed upon targeted oncogene inhibition solely in addicted cell line models and patient tissues. We show that the OAPS is present in patient tissues and the OAPS-derived score strongly correlates with the ex vivo responses to targeted treatments.
Project description:The suppression of oncogenic levels of MYC is sufficient to induce sustained tumor regression associated with proliferative arrest, differentiation, cellular senescence and/or apoptosis, a phenomenon known as oncogene addiction. However, after prolonged inactivation of MYC in a conditional transgenic mouse model of Em-tTA/tetO-MYC T-acute lymphomablastic lymphoma (T-ALL), some of the tumors recur, recapitulating what is frequently observed in human tumors in response to targeted therapies. Here we report that these recurring lymphomas express high levels of either transgenic or endogenous Myc suggesting that tumors continue to be addicted to oncogenic levels of MYC. Many of the recurring lymphomas (76%) harbored mutations in the tetracycline transactivator (tTA) resulting in expression of the MYC transgene even in the presence of doxycycline. Many of the remaining recurring tumors expressed high levels of endogenous Myc which was in some cases associated with a genomic rearrangement of the endogenous Myc locus or overexpression of Notch1. Gene expression profiling confirmed that the primary and recurring tumors have highly similar transcriptomes. Importantly, shRNA-mediated suppression of the high levels of MYC in recurring tumors elicited both suppression of proliferation and increased apoptosis confirming that these tumors remain oncogene addicted. These results suggest that tumors caused by MYC overexpression remain addicted to high levels of expression of this oncogene.
Project description:Gain-of-function IDH mutations define major clinical and prognostic classes of gliomas. Mutant IDH protein produces a novel onco-metabolite, 2-hydroxyglutarate (2-HG), that interferes with iron-dependent hydroxylase enzymes, including the TET family of 5'-methylcytosine hydroxylases. TET enzymes are critical for the dynamic regulation of DNA methylation. IDH mutant gliomas thus manifest a CpG island methylator phenotype (G-CIMP), though the functional significance of this altered epigenetic state remains unclear. Here we show that IDH1 mutant gliomas exhibit hyper-methylation at CTCF binding sites, leading to reduced binding of this methylation-sensitive insulator protein. Loss of CTCF binding is associated with a loss of insulation between topological domains and aberrant gene activation. We specifically demonstrate that loss of CTCF at a domain boundary permits a constitutive enhancer to aberrantly interact with the receptor tyrosine kinase gene PDGFRA, a prominent glioma oncogene. Treatment of IDH mutant gliomaspheres with demethylating agent partially restores insulator function and reduces PDGFRA expression. Conversely, CRISPR-mediated disruption of the CTCF binding sequence in IDH wildtype gliomaspheres induces PDGFRA expression and increases proliferation. Our study suggests that IDH mutations promote gliomagenesis by disrupting chromosomal topology and allowing aberrant regulatory interactions that induce oncogene expression. CTCF occupancy characterization and histone H3K27 acetylation profiling in IDH1 mutant and wild-type glioma patient specimens and culture models. ChIP-seq raw data is to be made available through dbGaP (controlled access) due to patient privacy concerns.
Project description:Rhabdomyosarcomas (RSCs) are skeletal muscle neoplasms found in humans and domestic mammals. The A/J inbred strain developed a high frequency of RSC by 20 months of age while BALB/cJ and BALB/cByJ also develop RSC but less frequently. These neoplasms affected skeletal muscle surrounding either the axial or proximal appendicular skeleton and were characterized by pleomorphic cells with abundant eosinophilic cytoplasm, multiple nuclei, and cross striations that invaded locally. The diagnosis was confirmed by detection of alpha-sarcomeric actin and myogenin in the neoplastic cells using immunocytochemistry. The A/J strain, but not the related BALB/c substrains, is also characterised by a progressive muscular dystrophy homologous to limb-girdle muscular dystrophy type 2B. The association between the development of RSC in similar muscle groups to those most severely affected by the progressive muscular dystrophy suggested that these neoplasms developed from abnormal regeneration of the skeletal muscle exacerbated by the dysferlin mutation. Transcriptome analyses revealed marked downregulation of genes in muscular development and function signaling networks. Non-synonymous coding SNPs were found in Myl1, Abra, Sgca, Ttn, and Kcnj12 suggesting these may be important in the pathogenesis of RSC. These studies suggest that A strains of mice can be useful models for dissecting the molecular genetic basis for development, progression, and ultimately for testing novel anticancer therapeutic agents dealing with rhabdomyosarcoma. Total RNA obtained from skeletal muscle samples from neoplastic and non-neoplastic tissues. Four rhabdomyosarcomas (~450 day old male A/J mice) and 8 nonneoplastic skeletal muscle samples (425-550 day old male A/J mice) were used