Genomic loss of the putative tumor suppressor gene E2A promotes cutaneous T-cell lymphoma in human
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE21731 | GEO | 2011/07/07
SECONDARY ACCESSION(S): PRJNA127347
REPOSITORIES: GEO
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Project description:The transcription factor E2A is essential for lymphocyte development. In this study, we describe a recurrent E2A gene deletion in at least 70% of patients with Sézary syndrome (SS), a subtype of T cell lymphoma. Loss of E2A results in enhanced proliferation and cell cycle progression via derepression of the protooncogene MYC and the cell cycle regulator CDK6. Furthermore, by examining the gene expression profile of SS cells after restoration of E2A expression, we identify several E2A-regulated genes that interfere with oncogenic signaling pathways, including the Ras pathway. Several of these genes are down-regulated or lost in primary SS tumor cells. These data demonstrate a tumor suppressor function of E2A in human lymphoid cells and could help to develop new treatment strategies for human lymphomas with altered E2A activity.
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Project description:Increasing evidences support a potential role for the Signal Transducer and Activator of Transcription-3 (STAT3) as a tumor driver in cutaneous T-cell lymphoma (CTCL). However, the mechanisms leading to STAT3 pathway activation in CTCL and how STAT3 activation contributes to lymphomagenesis remains primarily not enough explored. Recently, we found that miR-124, a known STAT3 regulator in cancer, is robustly silenced in Mycosis Fungoides (MF) tumor-stage and CTCL cell lines and we have herein studied whether deregulation of miR-124 contributes to activate STAT3 pathway in CTCL. Material and Methods: DNA methylation status of miR-124 and its expression levels in response to the DNA-demethylating agent azacitidine were evaluated in CTCL cell lines by pyrosequencing analysis. CTCL cell lines were transient transfected with a lentiviral vector encoding miR-124 and transfected cells were analyzed for phosphorylated STAT3 (P-STAT3) levels. The impact on STAT3 signaling was evaluated using expression microarray on CTCL cell lines in both conditions, miR-124 absent (malignant condition) versus miR-124 expressed (lentiviral transduction). Results: A significant promoter methylation and silencing of miR-124 in MF tumor samples and CTCL cell lines was detected. DNA methylation levels of miR-124 in CTCL cell lines were restored (and subsequently miR-124 were overexpressed) after DNA demethylation. Ectopic lentiviral expression of miR-124 downregulated STAT3 in the different CTCL cell lines. Genes differentially expressed regarding miR-124 regulation in CTCL cell lines indicated impact on known cell survival and function pathways and, particularly, intervention on miR-124 expression modulated different STAT3 pathway components. Conclusions: Our study deciphers a novel epigenetic mechanisms regulating STAT3 pathway in CTCL. This might contribute to a better understanding the molecular basis in CTCL development. Deregulation of STAT3 seems to have a major impact on cell survival in CTCL cell lines indicating the potential interest of targeting STAT3 with specific therapies.
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Project description:Gene-associated with retinoid-interferon induced mortality-19 (GRIM-19), a STAT3-inhibitory protein, was isolated as a growth-suppressive gene product using a genome-wide expression knockdown screen. We and others have shown a loss of expression and occurrence of mutations in the GRIM-19 gene in a variety of primary human cancers, indicating its potential role as tumor suppressor. To help investigate its role in tumor development in vivo, we generated a genetically modified mouse in which Grim-19 can be conditionally inactivated. Deletion of Grim-19 in the skin significantly increased the susceptibility of mice to chemical carcinogenesis, resulting in development of squamous cell carcinomas. These tumors had high Stat3 activity and an increased expression of Stat3-responsive genes. Loss of Grim-19 also caused mitochondrial electron transport dysfunction resulting from failure to assemble electron transport chain complexes and altered the expression of several cellular genes involved in glycolysis. Surprisingly, the deletion of a single copy of the Grim-19 gene was sufficient to promote carcinogenesis and formation of invasive squamous cell carcinomas. These observations highlight the critical role of GRIM-19 as a tumor suppressor.
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Project description:Increasing evidence supports a potential role for STAT3 as a tumor driver in cutaneous T-cell lymphomas (CTCL). The mechanisms leading to STAT3 activation are not fully understood; however, we recently found that miR-124, a known STAT3 regulator, is robustly silenced in MF tumor-stage and CTCL cells. We studied here whether deregulation of miR-124 contributes to STAT3 pathway activation in CTCL. We measured the effect of ectopic mir-124 expression in active phosphorylated STAT3 (p-STAT3) levels and evaluated the transcriptional impact of miR-124-dependent STAT3 pathway regulation by expression microarray analysis. We found that ectopic expression of miR-124 results in massive downregulation of activated STAT3 in different CTCL lines, which resulted in a significant alteration of genetic signatures related with gene transcription and proliferation such as MYC and E2F. Our study highlights the importance of the miR-124/STAT3 axis in CTCL and demonstrates that the STAT3 pathway is regulated through epigenetic mechanisms in these cells. Since deregulated STAT3 signaling has a major impact on CTCL initiation and progression, a better understanding of the molecular basis of the miR-124/STAT3 axis may provide useful information for future personalized therapies.
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Project description:Putative tumor suppressor ALDH1L1, the product of natural fusion of three unrelated genes, regulates folate metabolism by catalyzing NADP+-dependent conversion of 10-formyltetrahydrofolate to tetrahydrofolate and CO2. Cryo-EM structures of tetrameric rat ALDH1L1 revealed the architecture and functional domain interactions of this complex enzyme. Highly mobile N-terminal domains, which remove formyl from 10-formyltetrahydrofolate, undergo multiple transient inter-domain interactions. The C-terminal aldehyde dehydrogenase domains, which convert formyl to CO2, form unusually large interfaces with the intermediate domains, homologs of acyl/peptidyl carrier proteins (A/PCPs), which transfer the formyl group between the catalytic domains. The 4'-phosphopantetheine arm of the intermediate domain is fully extended and reaches deep into the catalytic pocket of the C-terminal domain. Remarkably, the tetrameric state of ALDH1L1 is indispensable for catalysis because the intermediate domain transfers formyl between the catalytic domains of different protomers. These findings emphasize the versatility of A/PCPs in complex, highly dynamic enzymatic systems.
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Project description:Secreted frizzled related protein 3 (SFRP3) contains a cysteine-rich domain (CRD) that shares homology with Frizzled CRD and regulates WNT signaling. Independent studies showed epigenetic silencing of SFRP3 in melanoma and hepatocellular carcinoma. Moreover, a tumor suppressive function of SFRP3 was shown in androgen-independent prostate and gastric cancer cells. The current study is the first to investigate SFRP3 expression and its potential clinical impact on non-small cell lung carcinoma (NSCLC). WNT signaling components present on NSCLC subtypes were preliminary elucidated by expression data of The Cancer Genome Atlas (TCGA). We identified a distinct expression signature of relevant WNT signaling components that differ between adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC). Of interest, canonical WNT signaling is predominant in LUAD samples and non-canonical WNT signaling is predominant in LUSC. In line, high SFRP3 expression resulted in beneficial clinical outcome for LUAD but not for LUSC patients. Furthermore, SFRP3 mRNA expression was significantly decreased in NSCLC tissue compared to normal lung samples. TCGA data verified the reduction of SFRP3 in LUAD and LUSC patients. Moreover, DNA hypermethylation of SFRP3 was evaluated in the TCGA methylation dataset resulting in epigenetic inactivation of SFRP3 expression in LUAD, but not in LUSC, and was validated by pyrosequencing of our NSCLC tissue cohort and in vitro demethylation experiments. Immunohistochemistry confirmed SFRP3 protein downregulation in primary NSCLC and indicated abundant expression in normal lung tissue. Two adenocarcinoma gain-of-function models were used to analyze the functional impact of SFRP3 on cell proliferation and regulation of CyclinD1 expression in vitro. Our results indicate that SFRP3 acts as a novel putative tumor suppressor gene in adenocarcinoma of the lung possibly regulating canonical WNT signaling.
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Project description:Cutaneous T cell lymphoma (CTCL) is a non-Hodgkin lymphoma of skin-homing T lymphocytes. We performed exome and whole-genome DNA sequencing and RNA sequencing on purified CTCL and matched normal cells. The results implicate mutations in 17 genes in CTCL pathogenesis, including genes involved in T cell activation and apoptosis, NF-κB signaling, chromatin remodeling and DNA damage response. CTCL is distinctive in that somatic copy number variants (SCNVs) comprise 92% of all driver mutations (mean of 11.8 pathogenic SCNVs versus 1.0 somatic single-nucleotide variant per CTCL). These findings have implications for new therapeutics.
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Project description:There is a growing appreciation of the role that epigenetic alterations can play in oncogenesis. However, given the large number of genetic anomalies present in most cancers, it has been difficult to evaluate the extent to which epigenetic changes contribute to cancer. SNF5 (INI1/SMARCB1/BAF47) is a tumor suppressor that regulates the epigenome as a core member of the SWI/SNF chromatin remodeling complex. While the SWI/SNF complex displays potent tumor suppressor activity, it is unknown whether this activity is exerted genetically via maintenance of genome integrity or epigenetically via transcriptional regulation. Here we show that Snf5-deficient primary cells do not show altered sensitivity to DNA damaging agents, defects in gamma-H2AX induction, or an abrogated DNA damage checkpoint. Further, the aggressive malignancies that arise following SNF5 loss are diploid and genomically stable. Remarkably, we demonstrate that most human SNF5-deficient cancers lack genomic amplifications/deletions and, aside from SNF5 loss, are indistinguishable from normal cells on single-nucleotide polymorphism arrays. Finally, we show that epigenetically based changes in transcription that occur following SNF5 loss correlate with the tumor phenotype. Collectively, our results provide novel insight into the mechanisms of oncogenesis by demonstrating that disruption of a chromatin remodeling complex can largely, if not completely, substitute for genomic instability in the genesis of aggressive cancer.
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