Gene expression profiles of control and EWS-FLI1-transduced neural crest stem cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Elizabeth Lawlor
PROVIDER: E-GEOD-68898 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Ewing sarcoma family of tumors (ESFT) are aggressive bone and soft tissue tumors of unknown cellular origin. Most ESFT express EWS-FLI1, a chimeric protein which functions as a growth-promoting oncogene in ESFT but is toxic to most normal cells. A major difficulty in understanding EWS-FLI1 function has been the lack of an adequate model in which to study EWS-FLI1-induced transformation. Although the cell of origin of ESFT remains elusive, both mesenchymal (MSC) and neural crest (NCSC) have been implicated. We recently developed the tools to generate NCSC from human embryonic stem cells (hNCSC). In the current study we used this model to test the hypothesis that neural crest-derived stem cells are the cells of origin of ESFT and to evaluate the consequences of EWS-FLI1 expression on human neural crest biology. hNCSC transduced with an EWS-FLI1 lentivirus tolerated expression of the oncoprotein. Moreover, EWS-FLI1-transduced hNCSC continued to proliferate and maintain EWS-FLI1 expression in culture for several weeks after transduction. Affymetrix HuEx 1.0 expression profiling of hNCSC cells five days post-transduction with EWS-FLI1 demonstrated the expected induction and repression of well-established EWS-FLI1 targets and also identified numerous other novel EWS-FLI1-regulated genes that are likely to be cell-type and situation specific. In particular, the EWS-FLI1 repressive signature was found to be highly context dependent. Moreover, while control vector transduced cells displayed an MSC-like phenotype, EWS-FLI1-transduced cells maintained a NCSC-like phenotype and genetic profiling revealed reprogramming towards a more pluriopotent, neuroectodermal state. Finally, EWS-FLI1 expressing cells upregulated expression of the polycomb proteins BMI-1 and EZH2. These data implicate neural crest-derived cells in the origin of ESFT and suggest that EWS-FLI1 enables malignant transformation by inducing maintenance of a multipotent, NCSC-state through deregulation of polycomb genes. 3 replicate samples for 4 different stem cell populations were analyzed by HuEx arrays. The 4 sample types were adult human bone marrow-derived mesenchymal stem cells, human embryonic stem cell-derived nueral crest stem cells (hNCSC), control vector-transduced hNCSC-derived mesenchymal stem cells (NC-MSC), and EWS-FLI1-transduced hNCSC-derived mesenchymal stem cells (NC-MSC EF). Control and EWS-FLI1 transduced NC-MSC were isolated 5 days after lentiviral transduction. Transcript level expression data was compared among the different populations to determine differences and similarities between NCSC, BM-MSC and NC-MSC with/without EWS-FLI1 expression. These data were used to identify EWS-FLI1 targets in NC-MSC and to characterize the genetic changes that occur in NCSC as they generate NC-MSC progeny.
2010-06-23 | E-GEOD-21511 | biostudies-arrayexpress
Project description:The synthesis and processing of mRNA, from transcription to translation initiation, often requires splicing of intragenic material. The final mRNA composition varies based upon proteins that modulate splice site selection. EWS-FLI1 is an Ewing sarcoma (ES) oncogene with an interactome that we demonstrate to have multiple partners in spliceosomal complexes. We evaluate EWS-FLI1 upon post-transcriptional gene regulation using both exon array and RNA-seq. Genes that potentially regulate oncogenesis including CLK1, CASP3, PPFIBP1, and TERT validate as alternatively spliced by EWS-FLI1. EWS-FLI1 also alters splicing by directly binding to known splicing factors including DDX5, hnRNPK, and PRPF6. Reduction of EWS-FLI1 produces an isoform of g-TERT that has increased telomerase activity compared to WT TERT. The small molecule YK-4-279 is an inhibitor of EWS-FLI1 oncogenic function that disrupts specific protein interactions including DDX5 and RNA helicase A (RHA) that alters RNA splicing ratios. As such, YK-4-279 validates the splicing mechanism of EWS-FLI1 showing alternatively spliced gene patterns that significantly overlap with EWS-FLI1 reduction and WT human mesenchymal stem cells. Exon array analysis of 75 ES patient samples show similar isoform expression patterns to cell line models expressing EWS-FLI1, supporting the clinical relevance of our findings. These experiments establish systemic alternative splicing as an oncogenic process modulated by EWS-FLI1. EWS-FLI1 modulation of mRNA splicing may provide insight into the contribution of splicing towards oncogenesis, and reciprocally, EWS-FLI1 interactions with splicing proteins may inform the splicing code. Alternative splicing of RNA allows a limited number of coding regions in the human genome to produce proteins with diverse functionality. Alternative splicing has also been implicated as an oncogenic process. Identifying aspects of cancer cells that differentiate them from non-cancer cells remains an ongoing challenge and our research suggests that alternatively spliced mRNA and subsequent protein isoforms will provide new anti-cancer targets. We determined that the key oncogene of Ewing sarcoma (ES), EWS-FLI1, regulates alternative splicing in multiple cell line models. These experiments establish oncogenic aspects of splicing which are specific to cancer cells and thereby illuminate potentially oncogenic splicing shifts as well as provide a useful stratification mechanism for ES patients. We analyzed three models of EWS-FLI1 using Affymetrix GeneChip Human Exon 1.0 ST microarray: (i) Ewing's sarcoma TC32 wild-type cells expressing EWS-FLI1, and TC32 cells where EWS-FLI1 was reduced with a lentiviral shRNA; (ii) A673i, which has a doxycycline-inducible shRNA to reduce EWS-FLI1 expression, and wild-type EWS-FLI1 to screen for alternative splicing as measured by exon-specific expression changes; and (iii) human mesenchymal stem cells (hMSC), a putative cell of origin of Ewing's sarcoma, exogenously expressing EWS-FLI1, and hMSC wild-type cells without EWS-FLI1. Three biological replicates were included for each condition. The Bioconductor package "oligo" in the R programming language was used for normalization and background correction. Analysis was carried out using only core probesets, as defined by the manufacturer.
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The latter group were children with a TST = 10 mm or a positive QFT-GIT result who presented all of: persistent fever >38M-BM-0C objectively recorded daily for at least two weeks, persistent cough for more than three weeks, weight loss (>5% reduction in weight compared with the highest weight recorded in last three months) or failure to thrive (documented crossing of percentile lines in the preceding three months), persistent lethargy or decrease in playfulness/activity reported by the parent and absence of clinical response on broad-spectrum antibiotics. Standard antero-posterior and lateral chest radiographs (CXRs) were taken from all children. Two independent experts, blinded to all clinical information, evaluated the CXRs and documented their findings on a standard report form. Where the two objective experts disagreed, a third expert was consulted and final consensus was achieved. A diagnosis of TB was only made when the CXR was consistent with TB9 and the child showed a positive clinical response to anti-TB treatment. Children were followed up clinically, radiologically and, in case of a negative TST at inclusion, by means of TST at six and 12 months after inclusion. LTBI was defined as a TST = 10mm and a positive QFT-GIT with a negative culture result on inclusion in the absence of radiological and clinical evidence of TB disease on inclusion as well as on t=6 and t=12 months. HC were children with a TST = 0 mm at inclusion and at t=6 and t=12 months. The HC had a negative QFT-GIT and a negative culture result at inclusion without radiological or clinical evidence of TB disease on inclusion nor on t=6 and t=12 months. TB patients were sampled before initiation of anti-TB treatment. Of three of the nine TB patients, a follow-up sample was taken when the patient was in anti-TB treatment for five months. All children were HIV-negative. 27 samples in total where analyzed, active TB infection (TB, n=9), Latent TB infection (LTBI, n=9) and healthy controls (HC, n=9) . Gene expression values were log2-transformed and differentially expressed genes were identified based on log2 fold changes (M-values). P values were calculated with a Bayes-regularized one-way ANOVA. Random Forest recursive feature elimination was used to find a signature geneset capable of discrimination active TB from latent TB and from non-infected individuals.
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