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Transcriptional amplification in tumor cells with elevated c-Myc.

ABSTRACT: Elevated expression of the c-Myc transcription factor occurs frequently in human cancers and is associated with tumor aggression and poor clinical outcome. The effect of high levels of c-Myc on global gene regulation is poorly understood but is widely thought to involve newly activated or repressed "Myc target genes." We report here that in tumor cells expressing high levels of c-Myc the transcription factor accumulates in the promoter regions of active genes and causes transcriptional amplification, producing increased levels of transcripts within the cell's gene expression program. Thus, rather than binding and regulating a new set of genes, c-Myc amplifies the output of the existing gene expression program. These results provide an explanation for the diverse effects of oncogenic c-Myc on gene expression in different tumor cells and suggest that transcriptional amplification reduces rate-limiting constraints for tumor cell growth and proliferation.

SUBMITTER: Lin CY

PROVIDER: S-EPMC3462372 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Transcriptional amplification in tumor cells with elevated c-Myc.

Lin Charles Y CY Lovén Jakob J Rahl Peter B PB Paranal Ronald M RM Burge Christopher B CB Bradner James E JE Lee Tong Ihn TI Young Richard A RA

Cell 20120901 1

Elevated expression of the c-Myc transcription factor occurs frequently in human cancers and is associated with tumor aggression and poor clinical outcome. The effect of high levels of c-Myc on global gene regulation is poorly understood but is widely thought to involve newly activated or repressed "Myc target genes." We report here that in tumor cells expressing high levels of c-Myc the transcription factor accumulates in the promoter regions of active genes and causes transcriptional amplifica ...[more]

PMID: 23021215

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Replication Study: Transcriptional amplification in tumor cells with elevated c-Myc.

Project description:As part of the Reproducibility Project: Cancer Biology, we published a Registered Report (Blum et al., 2015), that described how we intended to replicate selected experiments from the paper 'Transcriptional amplification in tumor cells with elevated c-Myc' (Lin et al., 2012). Here we report the results. We found overexpression of c-Myc increased total levels of RNA in P493-6 Burkitt's lymphoma cells; however, while the effect was in the same direction as the original study (Figure 3E; Lin et al., 2012), statistical significance and the size of the effect varied between the original study and the two different lots of serum tested in this replication. Digital gene expression analysis for a set of genes was also performed on P493-6 cells before and after c-Myc overexpression. Transcripts from genes that were active before c-Myc induction increased in expression following c-Myc overexpression, similar to the original study (Figure 3F; Lin et al., 2012). Transcripts from genes that were silent before c-Myc induction also increased in expression following c-Myc overexpression, while the original study concluded elevated c-Myc had no effect on silent genes (Figure 3F; Lin et al., 2012). Treating the data as paired, we found a statistically significant increase in gene expression for both active and silent genes upon c-Myc induction, with the change in gene expression greater for active genes compared to silent genes. Finally, we report meta-analyses for each result.

| S-EPMC5760205 | biostudies-literature

Transcriptional Amplification in Tumor Cells with Elevated c-Myc

Project description:Excessive expression of c-Myc occurs frequently in human cancers, where high levels are associated with tumor aggression and poor clinical outcome, but the effect of high levels of c-Myc on global gene regulation is poorly understood. We report here that in tumor cells expressing high levels of c-Myc, the transcription factor binds to E-box sequences in the core promoters of most actively transcribed genes and, unexpectedly, the enhancers of these active genes. The predominant effect of increasing c-Myc levels at both proximal and distal promoter elements is to produce higher levels of transcription at existing active genes by promoting RNA polymerase II elongation, as opposed to stimulating transcription of novel target genes. Our results argue that c-Myc overexpression drives increased transcription of growth-promoting genes, and does so by amplifying the levels of transcripts associated with the entire gene expression program of the cancer cell. Thus, excess c-Myc functions to elicit the transcriptional amplification of existing active genes through the invasion of enhancers across the cancer cell genome, thereby reducing the rate-limiting constraints required for continuous tumor growth and proliferation.

2012-04-05 | GSE36354 | GEO

Enhancer Invasion and Transcriptional Amplification in Tumor Cells with Elevated c-Myc

2012-04-04 | E-GEOD-36354 | biostudies-arrayexpress

Super enhancer inhibitors suppress MYC driven transcriptional amplification and tumor progression in osteosarcoma.

Project description:Osteosarcoma is the most common primary bone sarcoma that mostly occurs in young adults. The causes of osteosarcoma are heterogeneous and still not fully understood. Identification of novel, important oncogenic factors in osteosarcoma and development of better, effective therapeutic approaches are in urgent need for better treatment of osteosarcoma patients. In this study, we uncovered that the oncogene MYC is significantly upregulated in metastastic osteosarcoma samples. In addition, high MYC expression is associated with poor survival of osteosarcoma patients. Analysis of MYC targets in osteosarcoma revealed that most of the osteosarcoma super enhancer genes are bound by MYC. Treatment of osteosarcoma cells with super enhancer inhibitors THZ1 and JQ1 effectively suppresses the proliferation, migration, and invasion of osteosarcoma cells. Mechanistically, THZ1 treatment suppresses a large group of super enhancer containing MYC target genes including CDK6 and TGFB2. These findings revealed that the MYC-driven super enhancer signaling is crucial for the osteosarcoma tumorigenesis and targeting the MYC/super enhancer axis represents as a promising therapeutic strategy for treatment of osteosarcoma patients.

| S-EPMC5884797 | biostudies-literature

USP10 antagonizes c-Myc transcriptional activation through SIRT6 stabilization to suppress tumor formation.

Project description:The reduced protein expression of SIRT6 tumor suppressor is involved in tumorigenesis. The molecular mechanisms underlying SIRT6 protein downregulation in human cancers remain unknown. Using a proteomic approach, we have identified the ubiquitin-specific peptidase USP10, another tumor suppressor, as one of the SIRT6-interacting proteins. USP10 suppresses SIRT6 ubiquitination to protect SIRT6 from proteasomal degradation. USP10 antagonizes the transcriptional activity of the c-Myc oncogene through SIRT6, as well as p53, to inhibit cell-cycle progression, cancer cell growth, and tumor formation. To support this conclusion, we detected significant reductions in both USP10 and SIRT6 protein expression in human colon cancers. Our study discovered crosstalk between two tumor-suppressive genes in regulating cell-cycle progression and proliferation and showed that dysregulated USP10 function promotes tumorigenesis through SIRT6 degradation.

| S-EPMC4007576 | biostudies-literature

The tumor suppressor protein HBP1 is a novel c-myc-binding protein that negatively regulates c-myc transcriptional activity.

Project description:c-Myc is an important transcription factor that regulates cellular proliferation, cell growth, and differentiation. A number of transcriptional co-factors for c-Myc have been described that have binding sites within highly conserved regions of the c-Myc transactivational domain (TAD). Given the importance of the c-Myc TAD, we set out to identify new proteins that interact with this region using a yeast two-hybrid assay. HBP1 was identified in our screen as a protein that interacts with full-length c-Myc but not a c-Myc mutant lacking the TAD. HBP1 is a transcriptional repressor and has been shown to negatively regulate the cell cycle. A correlation between HBP1 under-expression and breast cancer relapse has been described, suggesting that HBP1 may be an important tumor suppressor protein. We have found that HBP1 binds c-Myc in cells, and expression of HBP1 inhibits c-Myc transactivational activity at least partly by preventing c-Myc binding to target gene promoters. c-Myc binds to the C terminus of HBP1, a region lost in some breast tumors, and some HBP1 mutants found in breast cancer weakly interact with and/or no longer negatively regulate c-Myc. This work adds to our understanding of c-Myc regulation and mechanisms of tumor suppression by HBP1.

| S-EPMC2836090 | biostudies-other

MYC-Regulated Mevalonate Metabolism Maintains Brain Tumor-Initiating Cells.

Project description:Metabolic dysregulation drives tumor initiation in a subset of glioblastomas harboring isocitrate dehydrogenase (IDH) mutations, but metabolic alterations in glioblastomas with wild-type IDH are poorly understood. MYC promotes metabolic reprogramming in cancer, but targeting MYC has proven notoriously challenging. Here, we link metabolic dysregulation in patient-derived brain tumor-initiating cells (BTIC) to a nexus between MYC and mevalonate signaling, which can be inhibited by statin or 6-fluoromevalonate treatment. BTICs preferentially express mevalonate pathway enzymes, which we find regulated by novel MYC-binding sites, validating an additional transcriptional activation role of MYC in cancer metabolism. Targeting mevalonate activity attenuated RAS-ERK-dependent BTIC growth and self-renewal. In turn, mevalonate created a positive feed-forward loop to activate MYC signaling via induction of miR-33b. Collectively, our results argue that MYC mediates its oncogenic effects in part by altering mevalonate metabolism in glioma cells, suggesting a therapeutic strategy in this setting. Cancer Res; 77(18); 4947-60. ©2017 AACR.

| S-EPMC5600855 | biostudies-literature

Artemis and p53 cooperate to suppress oncogenic N-myc amplification in progenitor B cells.

Project description:The nonhomologous DNA end-joining (NHEJ) pathway contains six known components, including Artemis, a nuclease mutated in a subset of human severe combined immunodeficient patients. Mice doubly deficient for the five previously analyzed NHEJ factors and p53 inevitably develop progenitor B lymphomas harboring der(12)t(12;15) translocations and immunoglobin heavy chain (IgH)/c-myc coamplification mediated by a breakage-fusion-bridge mechanism. In this report, we show that Artemis/p53-deficient mice also succumb reproducibly to progenitor B cell tumors, demonstrating that Artemis is a tumor suppressor in mice. However, the majority of Artemis/p53-deficient tumors lacked der(12)t(12;15) translocations and c-myc amplification and instead coamplified IgH and N-myc through an intra- or interchromosome 12 breakage-fusion-bridge mechanism. We discuss this finding in the context of potential implications for mechanisms that may target IgH locus translocations to particular oncogenes.

| S-EPMC356964 | biostudies-literature

A global transcriptional regulatory role for c-Myc in Burkitt's lymphoma cells.

Project description:Overexpression of c-Myc is one of the most common alterations in human cancers, yet it is not clear how this transcription factor acts to promote malignant transformation. To understand the molecular targets of c-Myc function, we have used an unbiased genome-wide location-analysis approach to examine the genomic binding sites of c-Myc in Burkitt's lymphoma cells. We find that c-Myc together with its heterodimeric partner, Max, occupy >15% of gene promoters tested in these cancer cells. The DNA binding of c-Myc and Max correlates extensively with gene expression throughout the genome, a hallmark attribute of general transcription factors. The c-Myc/Max heterodimer complexes also colocalize with transcription factor IID in these cells, further supporting a general role for overexpressed c-Myc in global gene regulation. In addition, transcription of a majority of c-Myc target genes exhibits changes correlated with levels of c-myc mRNA in a diverse set of tissues and cell lines, supporting the conclusion that c-Myc regulates them. Taken together, these results suggest a general role for overexpressed c-Myc in global transcriptional regulation in some cancer cells and point toward molecular mechanisms for c-Myc function in malignant transformation.

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Myc-mediated transcriptional regulation of the mitochondrial chaperone TRAP1 controls primary and metastatic tumor growth.

Project description:The role of mitochondria in cancer continues to be debated, and whether exploitation of mitochondrial functions is a general hallmark of malignancy or a tumor- or context-specific response is still unknown. Using a variety of cancer cell lines and several technical approaches, including siRNA-mediated gene silencing, ChIP assays, global metabolomics and focused metabolite analyses, bioenergetics, and cell viability assays, we show that two oncogenic Myc proteins, c-Myc and N-Myc, transcriptionally control the expression of the mitochondrial chaperone TNFR-associated protein-1 (TRAP1) in cancer. In turn, this Myc-mediated regulation preserved the folding and function of mitochondrial oxidative phosphorylation (OXPHOS) complex II and IV subunits, dampened reactive oxygen species production, and enabled oxidative bioenergetics in tumor cells. Of note, we found that genetic or pharmacological targeting of this pathway shuts off tumor cell motility and invasion, kills Myc-expressing cells in a TRAP1-dependent manner, and suppresses primary and metastatic tumor growth in vivo We conclude that exploitation of mitochondrial functions is a general trait of tumorigenesis and that this reliance of cancer cells on mitochondrial OXPHOS pathways could offer an actionable therapeutic target in the clinic.

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