Project description:Point mutations within the TERT promoter are the most common recurrent somatic non-coding mutation identified across different cancer types, including glioblastoma, melanoma, hepatocellular carcinoma and bladder cancer. They are most abundant at C146T and C124T and more rare at A57C, with the latter originally described as a familial case but subsequently shown also to occur somatically. All three mutations create de novo ETS (E-twenty-six specific) binding sites and result in the reactivation of the TERT gene, allowing cancer cells to achieve replicative immortality. Here, we employed a systematic proteomics screen to identify transcription factors preferentially binding to the C146T, C124T and A57C mutations. While we confirmed binding of multiple ETS factors to the mutant C146T and C124T sequences, we identified E4F1 a an A57C-specific binder and ZNF148 as a TERT WT binder that is excluded from the TERT promoter by the C124T allele. Both proteins are activating transcription factors that bind specifically to the A57C and wildtype (at position 124) TERT promoter sequence in corresponding cell lines and upregulate TERT transcription and telomerase activity.
Project description:TERT promoter muatations occur frequently in tumors of various origin. We here accessed the frequency of TERT pomoter mutations in 131 human primary neuroblastomas and 20 human neuroblastoma cell lines. No TERT promoter mutations were found in the 131 primary neuroblastomas. However, in the three cell lines SH-SY5Y, SH-EP and SK-N-SH a TERT promoter mutation was detected. Sanger sequencing indicated a homozygous mutation. To confirm loss of heterozygosity (LOH) we performed Affymetrix CytoScanHD SNP arrays. Indeed LOH could be confirmed.
Project description:TERT promoter muatations occur frequently in tumors of various origin. We here accessed the frequency of TERT pomoter mutations in 131 human primary neuroblastomas and 20 human neuroblastoma cell lines. No TERT promoter mutations were found in the 131 primary neuroblastomas. However, in the three cell lines SH-SY5Y, SH-EP and SK-N-SH a TERT promoter mutation was detected. Sanger sequencing indicated a homozygous mutation. To confirm loss of heterozygosity (LOH) we performed Affymetrix CytoScanHD SNP arrays. Indeed LOH could be confirmed. SNP arry experiments were performed according to the standard protocol for Affymetrix CytoScanHD arrays (Affymetrix, Santa Clara). Briefly, a 250 ng sample of genomic DNA was digested with NspI, ligated to adaptors, amplified by PCR, fragmented and biotin-labeled. The labeled samples were hybridized to Affymetrix CytoscanHD arrays, followed by washing, staining and scanning in the Affymetrix GeneChip Scanner 3000. Analysis was performed using the Affymetrix Chromosome Analysis Suite v2.1.
Project description:Meningiomas are mostly benign brain tumors, with a potential for becoming atypical or malignant. Based on comprehensive genomic, transcriptomic and epigenomic analyses of meningiomas, we compared benign tumors to atypical ones. We show that the vast majority of primary (de novo atypical meningiomas display loss of NF2, which co-occurs either with genomic instability or recurrent mutations in SMARCB1. These tumors harbor increased H3K27me3 repressive signal and a hypermethylated phenotype, mainly occupying the polycomb repressive complex 2 (PRC2 binding sites in human embryonic stem cells (hESCs, thereby phenocopying a more primitive cellular state. Consistent with this observation, and based on differential gene expression analysis as well as correlation of mRNA:miRNA regulatory networks, atypical meningiomas exhibit up-regulation of EZH2, the catalytic subunit of the PRC2 complex, well as the E2F2 and FOXM1 transcriptional networks that promote proliferation through activation of the cell cycle pathways. In addition, based on H3K27ac ChIP-seq analysis, we show atypical tumors to display an activated super-enhancer near the meningeal identity transcription factor ZIC1, leading to its transcriptional upregulation. Importantly, these primary atypical meningiomas do not harbor activating TERT promoter mutations, which have been reported in atypical tumors that progressed from benign ones. Our results establish the genomic landscape of primary atypical meningiomas, differentiating their profile from benign and progressed tumors and establishing novel therapeutic targets.
Project description:Meningiomas are mostly benign brain tumors, with a potential for becoming atypical or malignant. Based on comprehensive genomic, transcriptomic and epigenomic analyses of meningiomas, we compared benign tumors to atypical ones. We show that the vast majority of primary (de novo) atypical meningiomas display loss of NF2, which co-occurs either with genomic instability or recurrent mutations in SMARCB1. These tumors harbor increased H3K27me3 repressive signal and a hypermethylated phenotype, mainly occupying the polycomb repressive complex 2 (PRC2) binding sites in human embryonic stem cells (hESCs), thereby phenocopying a more primitive cellular state. Consistent with this observation, and based on differential gene expression analysis as well as correlation of mRNA:miRNA regulatory networks, atypical meningiomas exhibit up-regulation of EZH2, the catalytic subunit of the PRC2 complex, well as the E2F2 and FOXM1 transcriptional networks that promote proliferation through activation of the cell cycle pathways. In addition, based on H3K27ac ChIP-seq analysis, we show atypical tumors to display an activated super-enhancer near the meningeal identity transcription factor ZIC1, leading to its transcriptional upregulation. Importantly, these primary atypical meningiomas do not harbor activating TERT promoter mutations, which have been reported in atypical tumors that progressed from benign ones. Our results establish the genomic landscape of primary atypical meningiomas, differentiating their profile from benign and progressed tumors and establishing novel therapeutic targets.
Project description:Our study proposes a precise mechanistic classification of clinical neuroblastoma phenotypes that is based on telomere maintenance mechanisms and RAS or p53 pathway mutations. A crucial factor in telomere maintenance is overexpression of TERT. We therefore determined a TERT expression threshold to identify MYCN-WT TERT-WT tumors whose TERT mRNA levels are comparable to those of tumors bearing MYCN or TERT alterations.
Project description:Our study proposes a precise mechanistic classification of clinical neuroblastoma phenotypes that is based on telomere maintenance mechanisms and RAS or p53 pathway mutations. A crucial factor in telomere maintenance is overexpression of TERT. We therefore determined a TERT expression threshold to identify MYCNWT TERTWT tumors whose TERT mRNA levels are comparable to those of tumors bearing MYCN or TERT alterations.
Project description:Meningiomas are mostly benign brain tumors, with a potential for becoming atypical or malignant. Based on comprehensive genomic, transcriptomic and epigenomic analyses of meningiomas, we compared benign tumors to atypical ones. We show that the vast majority of primary (de novo) atypical meningiomas display loss of NF2, which co-occurs either with genomic instability or recurrent mutations in SMARCB1. These tumors harbor increased H3K27me3 repressive signal and a hypermethylated phenotype, mainly occupying the polycomb repressive complex 2 (PRC2) binding sites in human embryonic stem cells (hESCs), thereby phenocopying a more primitive cellular state. Consistent with this observation, and based on differential gene expression analysis as well as correlation of mRNA:miRNA regulatory networks, atypical meningiomas exhibit up-regulation of EZH2, the catalytic subunit of the PRC2 complex, well as the E2F2 and FOXM1 transcriptional networks that promote proliferation through activation of the cell cycle pathways. In addition, based on H3K27ac ChIP-seq analysis, we show atypical tumors to display an activated super-enhancer near the meningeal identity transcription factor ZIC1, leading to its transcriptional upregulation. Importantly, these primary atypical meningiomas do not harbor activating TERT promoter mutations, which have been reported in atypical tumors that progressed from benign ones. Our results establish the genomic landscape of primary atypical meningiomas, differentiating their profile from benign and progressed tumors and establishing novel therapeutic targets.
Project description:Blocking telomerase is recognized as a key anti-cancer mechanism. Unlike in stem cells, levels of telomerase catalytic subunit TERT are limiting in reconstituting telomerase activity in somatic cells. However in some cancers, Tert is transcriptionally reactivated by mutations in its promoter. Given that Tert in stem cells is driven by WT Tert promoter, if we can selectively target Tert reactivation through mutant Tert promoters we can block telomerase activity specifically in cancer cells without toxicity in stem cells. Here we report the epigenetic regulation of Tert promoter comparing WT and mutant promoters. We showed that GABPA homodimerization through long-range interaction stabilizes Gabpa to drive Tert expression. Furthermore, BRD4 specifically activates the C250T mutant promoter via dual mechanism involving GABPA, thereby setting the stage for future therapeutics.
Project description:Mutations in the promoter of the telomerase reverse transcriptase (TERT) gene are the paradigm of a cross-cancer alteration in a non-coding region. TERT promoter mutations (TPMs) are biomarkers of poor prognosis in cancer, including thyroid tumors. TPMs enhance TERT transcription, which is otherwise silenced in adult tissues, thus reactivating a bona fide oncoprotein. To study TERT deregulation and its downstream consequences, we generated a Tert mutant promoter mouse model via CRISPR/Cas9 engineering of the murine equivalent locus (Tert-123C>T) and crossed it with thyroid-specific BrafV600E-mutant mice. We also employed an alternative model of Tert overexpression (K5-Tert). Whereas all BrafV600E animals developed well-differentiated papillary thyroid tumors, 29% and 36% of BrafV600E+Tert-123C>T and BrafV600E+K5-Tert mice progressed to poorly differentiated cancers at week 20, respectively. Tert-upregulated tumors showed increased mitosis and necrosis in areas of solid growth, and older animals displayed anaplastic-like features, i.e., spindle cells and macrophage infiltration. Murine Tert promoter mutation increased Tert transcription in vitro and in vivo, but temporal and intra-tumoral heterogeneity was observed. RNA-sequencing of thyroid tumor cells showed that processes other than the canonical Tert-mediated telomere maintenance role operate in these specimens. Pathway analysis showed that MAPK and PI3K/AKT signaling, as well as processes not previously associated with this tumor etiology, involving cytokine and chemokine signaling, were overactivated. These models constitute useful pre-clinical tools to understand the cell-autonomous and microenvironment-related consequences of Tert-mediated progression in advanced thyroid cancers and other aggressive tumors carrying TPMs. Implications: Telomerase-driven cancer progression activates pathways that can be dissected and perhaps therapeutically exploited.