Unknown,Transcriptomics,Genomics,Proteomics

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Defining key signaling nodes and therapeutic biomarkers in NF1-mutant cancers

ABSTRACT: The NF1 tumor suppressor encodes a RAS GTPase-Activating Protein (RasGAP). Accordingly, deregulated RAS signaling underlies the pathogenesis of NF1-mutant cancers. However, while various RAS effector pathways have been shown to function in these tumors, it is currently unclear which specific proteins within these broad signaling pathways represent optimal therapeutic targets. Here we identify mTORC1 as the key PI3K pathway component in NF1-mutant nervous system malignancies and conversely show that mTORC2 and AKT are dispensable. We also report that combined mTORC1/MEK inhibition is required to promote tumor regression in animal models, but only when the inhibition of both pathways is sustained. Transcriptional profiling studies were also used to establish a predictive signature of effective mTORC1/MEK inhibition in vivo. Within this signature, we unexpectedly found that the glucose transporter gene, GLUT1, was potently suppressed but only when both pathways were effectively inhibited. Moreover, unlike VHL and LKB1 mutant cancers, reduction of 18F-FDG uptake measured by FDG-PET required the effective suppression of both mTORC1 and MEK. Together these studies identify optimal and sub-optimal therapeutic targets in NF1-mutant malignancies and define a non-invasive means of measuring combined mTORC1/MEK inhibition in vivo, which can be readily incorporated into clinical trials. 8 samples, in duplicate, 2X vehicle, 2X Rapamycin, 2X PD-0325901, 2X Rapamycin/PD-0325901

ORGANISM(S): Mus musculus

SUBMITTER: Clare malone

PROVIDER: E-GEOD-57141 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Neurofibromatosis Type 1 (NF1) patients develop benign neurofibromas and malignant peripheral nerve sheath tumors (MPNST). These incurable peripheral nerve tumors result from loss of NF1 tumor suppressor gene function, causing hyperactive Ras signaling. Activated Ras controls numerous downstream effectors, but specific pathways mediating effects of hyperactive Ras in NF1 tumors are unknown. Cross-species transcriptome analyses of mouse and human neurofibromas and MPNSTs identified global negative feedback of genes that regulate Ras-Raf- MEK- extracellular signal-regulated protein kinase (ERK) signaling in both species. Nonetheless, activation of ERK was sustained in mouse and human neurofibromas and MPNST. PD0325901, a highly selective pharmacological inhibitor of MEK, was used to test whether sustained Ras-Raf-MEK-ERK signaling contributes to neurofibroma growth in the Nf1fl/fl;Dhh-cre mouse model or in NF1 patient MPNST cell xenografts. PD0325901 treatment reduced aberrantly proliferating cells in neurofibroma and MPNST, prolonged survival of mice implanted with human MPNST cells, and shrank neurofibromas in >80% of mice tested. PD0325901 also caused effects on tumor vasculature. Our data demonstrate that deregulated Ras/ERK signaling is critical for the growth of NF1 peripheral nerve tumors and provide strong rationale for testing MEK inhibitors in NF1 clinical trials. 83 microarrays: Mouse control (15), Mouse neurofibroma (15), Mouse MPNST (18); Human nerve (3), Human neurofibroma (26), Human MPNST (6) We used the same human tumor samples as in series GSE14038 (dNF, pNF and MPNST). However, instead of referencing gene expression changes to the normal human Schwann cell samples (NHSC) as we did in series GSE14038, we generated three (new) normal nerve samples (samples jan-N1-3) and referenced gene expression changes to those samples. Moreover, the analysis of series GSE14038 evaluated changes in expression between NHSC, benign tumor subtypes (dNF and pNF), and malignant tumors (MPNST), while our present submission evaluated changes between normal nerve, benign tumors (combined dNF and pNF),and malignant tumors (MPNST). The Series supplementary 'merged_data.txt' file contains the data for 9,891 transcripts that were statistically different in at least one of the two species and present in both mouse and human data sets.

Project description:Background: Signaling by receptor tyrosine kinases (RTK) is frequently dysregulated in gliomas. Inter-individual variability in the causes for dysregulated RTK signaling may have hampered the efficacy of targeted therapies. Using gene expression modules around key regulators in the RAS-RAF-MEK-MAPK cascade and in the phosphatidylinositol 3-kinase-AKT pathways, we developed a âRMPAâ clustering scheme to distinguish gliomas with varying extents of RTK signaling. Results: We identified gene modules consistently co-expressed with NF1 (NF1-M), Sprouty (SPRY-M) and PTEN (PTEN-M) in gliomas. Their signatures enabled robust clustering of adult diffuse gliomas of WHO grades II-IV into RMPAhigh and RMPAlow phenotypes in a morphology-independent manner. In five independent data sets from three continents containing more than 1500 adult diffuse gliomas, RMPAhigh gliomas were associated with poor prognosis while RMPAlow gliomas were not. The RMPAhigh and RMPAlow glioma subtypes showed distinct levels of the activities of RAS-RAF-MEK-MAPK cascade and PI3K-AKT pathway and harbored unique sets of genomic alterations in the RTK signaling-related genes. The RMPAhigh gliomas contained large numbers of immature vessel cells and tumor associated macrophages and both cell types expressed high levels of pro-angiogenic RTKs including MET, VEGFR1, KDR, EPHB4 and NRP1. Conclusion: Inter-glioma variability in RTK signaling activities can be defined using the RMPA clustering scheme. The combined signatures of NF1-M, SPRY-M and PTEN-M reflect RTK signaling activity both in the glioma cells and in the glioma microenvironment. Our data show that RTK signaling in the glioma microenvironment may play a pivotal role in glioma progression. Transcriptome data from 22 fresh gliomas (2 astrocytoma II, 1 oligodendrocytoma II, 7 oligoastrocytoma II, 4 anaplastic oligoastrocytoma III and 8 GBM) were obtained using Affymetrix Human Gene 1.0 ST Array. Unsupervised hierarchical clustering of the expression data for the SPRY-M, NF1-M and PTEN-M was performed on these transcriptome data to identify samples with RMPAhigh or RMPAlow signature.

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Defining key signaling nodes and therapeutic biomarkers in NF1-mutant cancers

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