Project description:All three transforming members of the Myc family play a significant role in the development of both SCLC and NSCLC. NSCLC constitutes 80% of all lung cancer, and cMyc expression is most often deregulated, compared with N-Myc and L-Myc, in this disease. Thus, although we are interested in understanding the regulation and function of the entire Myc family in all lung cancers, we focused our research on cMyc deregulation in NSCLC. To identify target genes whose regulatory regions are bound in response to deregulated cMyc in NSCLC, we analyzed mouse xenograft tumours established in immune-compromised mice from monolayer cell lines derived from primary adenocarcinoma NSCLCs. These xenografts were chosen for further study because they show a genetic profile similar to their respective primary tumour (MGH8, RVH6849, A549, MGH24). High c-myc expression positively correlates with the ability of NSCLC cell lines to form xenografts, suggesting that Myc contributes towards the ability of the cells to grow in vivo. We conducted Myc-specific ChIP-chip and the corresponding normal IgG control using the Agilent genome-wide oligonucleotide promoter arrays on 3 biological replicates, of each of the four xenograft tumours. Following pre-processing using variance-stabilizing normalization and statistical analysis using general linear models we identified a list of 2,207 genes significantly enriched for c-Myc binding.
Project description:The functions of key oncogenic transcription factors independent of context have not been fully delineated despite our richer understanding of the genetic alterations in human cancers. The MYC oncogene, which produces the Myc transcription factor, is frequently altered in human cancer and is a major regulatory hub for many cancers. In this regard, we sought to unravel the primordial signature of Myc function by using high-throughput genomic approaches to identify the cell-type independent core Myc target gene signature. Using a model of human B lymphoma cells bearing inducible MYC, we identified a stringent set of direct Myc target genes via chromatin immunoprecipitation (ChIP), global nuclear run-on assay, and changes in mRNA levels. We also identified direct Myc targets in human embryonic stem cells (ESCs). We further document that a Myc core signature (MCS) set of target genes is shared in mouse and human ESCs as well as in four other human cancer cell types. Remarkably, the expression of the MCS correlates with MYC expression in a cell-type independent manner across 8,129 microarray samples, which include 312 cell and tissue types. Furthermore, the expression of the MCS is elevated in vivo in Em-Myc transgenic murine lymphoma cells as compared with premalignant or normal B lymphocytes. Expression of the MCS in human B cell lymphomas, acute leukemia, lung cancers or Ewing sarcomas has the highest correlation with MYC expression. Annotation of this gene signature reveals Myc's primordial function in RNA processing, ribosome biogenesis and biomass accumulation as its key roles in cancer and stem cells. This SuperSeries is composed of the SubSeries listed below.
Project description:Combining the results of a large scale proteomic analysis of human transcription factor interaction network with knowledge databases, we identified FOXR2 as one of the top-ranked candidate proto-oncogenes. Here, we show that FOXR2 forms a stable complex with MYC and MAX and subsequently regulates cell proliferation by promoting MYC’s transcriptional activities. We demonstrated that FOXR2 is highly expressed in several breast, lung, and liver cancer cell lines and related patient tumor samples, while reduction of FOXR2 expression in a xenograft model inhibits tumor growth. These results indicate that FOXR2 acts with MYC to promote cancer cell proliferation, which is a potential tumor-specific target for therapeutic intervention against MYC-driven cancers.
Project description:Chavez2009 - a core regulatory network of OCT4 in human embryonic stem cells
A core OCT4-regulated network has been identified as a test case, to analyase stem cell characteristics and cellular differentiation.
This model is described in the article:
In silico identification of a core regulatory network of OCT4 in human embryonic stem cells using an integrated approach.
Chavez L, Bais AS, Vingron M, Lehrach H, Adjaye J, Herwig R
BMC Genomics, 2009, 10:314
Abstract:
BACKGROUND: The transcription factor OCT4 is highly expressed in pluripotent embryonic stem cells which are derived from the inner cell mass of mammalian blastocysts. Pluripotency and self renewal are controlled by a transcription regulatory network governed by the transcription factors OCT4, SOX2 and NANOG. Recent studies on reprogramming somatic cells to induced pluripotent stem cells highlight OCT4 as a key regulator of pluripotency.
RESULTS: We have carried out an integrated analysis of high-throughput data (ChIP-on-chip and RNAi experiments along with promoter sequence analysis of putative target genes) and identified a core OCT4 regulatory network in human embryonic stem cells consisting of 33 target genes. Enrichment analysis with these target genes revealed that this integrative analysis increases the functional information content by factors of 1.3 - 4.7 compared to the individual studies. In order to identify potential regulatory co-factors of OCT4, we performed a de novo motif analysis. In addition to known validated OCT4 motifs we obtained binding sites similar to motifs recognized by further regulators of pluripotency and development; e.g. the heterodimer of the transcription factors C-MYC and MAX, a prerequisite for C-MYC transcriptional activity that leads to cell growth and proliferation.
CONCLUSION: Our analysis shows how heterogeneous functional information can be integrated in order to reconstruct gene regulatory networks. As a test case we identified a core OCT4-regulated network that is important for the analysis of stem cell characteristics and cellular differentiation. Functional information is largely enriched using different experimental results. The de novo motif discovery identified well-known regulators closely connected to the OCT4 network as well as potential new regulators of pluripotency and differentiation. These results provide the basis for further targeted functional studies.
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Project description:Gene expression was measured on the Affymetrix platform in primary xenografts, xenograft-derived cell lines, secondary xenografts, normal lung, and primary tumors obtained from chemotherapy naive Small Cell Lung Cancer (SCLC). The SCLC primary xenografts were serially propagated in vivo in immunodeficient mice. Cell lines were derived from each xenograft and grown for 6 months using conventional tissue culture conditions. Secondary xenografts were obtained from cell cultures by re-implantation in immunodeficient mice. Such SCLC laboratory models were analyzed along with conventional SCLC cell lines and the derivative secondary xenografts, with normal lung and primary tumors, to assess irreversible gene expression changes induced by culturing conditions. Experiment Overall Design: SCLC primary xenografts were compared to the corresponding xenograft-derived cell lines, and to the secondary xenografts established from the cell lines using the Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. Gene expression from SCLC primary tumors was measured using the Affymetrix GeneChip Human Genome U133A 2.0 Array. 3 datasets: GSM380476-GSM380512, GSM380513-GSM380516, and GSM380517-GSM380520
Project description:Efforts to therapeutically target EZH2 have generally focused on inhibition of its methyltransferase activity, although it remains less clear whether this is the central mechanism whereby EZH2 promotes cancer. We demonstrate that EZH2 directly interacts with both MYC family oncoproteins, MYC and MYCN, and promotes their stabilization in a methyltransferase-independent manner. By competing against the SCFFBW7 ubiquitin ligase to bind MYC and MYCN, EZH2 counteracted FBW7-mediated MYC(N) polyubiquitination and proteasomal degradation. Depletion, but not enzymatic inhibition, of EZH2 induced robust MYC(N) degradation and inhibited tumor cell growth in MYC(N) driven neuroblastoma and small cell lung cancer. These findings unveil the MYC family proteins as global EZH2 oncogenic effectors and EZH2 pharmacologic degraders as potential MYC(N) targeted cancer therapeutics, pointing out that MYC(N) driven cancers may develop inherent resistance to the canonical EZH2 enzymatic inhibitors currently in clinical development.