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Analysis of global RNA expression established that zebrafish brain tumors resemble GBMs of the mesenchymal subtype.

ABSTRACT: Somatic mutations activating MAPK signaling in disorders of brain overgrowth and in diffuse glioma have recently been reported in pediatric neurology. Here we developed a progressive zebrafish model of glioma based on somatic expression of oncogenes that activate MAPK-AKT signalling (H-RASG12V, K-RASG12D, AKT, EGFRv3, BRAFV600E) in neural progenitor cells. Oncogenic HRAS was the most effective in activating MAPK signaling and caused the development of different types of growth disorders in juvenile fish: from benign dysplasia/heterotopia to invasive tumors of the telencephalon, midbrain and cerebellum. We used this model to clarify the molecular events leading to malignant tumors instead of benign lesions. Specific signatures distinguish benign heterotopia from tumors and establish that tumors require persistent activation of MAPK/ERK. Moreover, analysis of global RNA expression showed that brain tumors expressed a gene signature similar to the mesenchymal glioblastoma subtype

ORGANISM(S): Danio rerio

PROVIDER: GSE74754 | GEO | 2017/03/08

SECONDARY ACCESSION(S): PRJNA301408

REPOSITORIES: GEO

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Project description:The mitogen-activated protein kinase (MAPK) pathway is one of the most altered pathways in cancer. It is involved in the control of cell proliferation, invasion, metabolism, and resistance to therapy. A number of aggressive malignancies, including melanoma, colon cancer and glioma, are driven by an activating missense mutation (V600E) in one component of the pathway, BRAF. BRAF V600E mutated cancers may respond initially to MEK inhibition, but may develop resistance mediated by increased reliance on mTOR signaling. We have previously demonstrated that the combination of the MEK inhibitor trametinib with the dual mTORC1/2 inhibitor TAK228 improved survival and decreased vascularization in a BRAFV600E mutant glioma model. To elucidate the mechanism of action of, and the changes in response to, MEK and mTOR inhibition, we performed comprehensive unbiased proteomic and phosphoproteomic characterization of BRAFV600E mutant glioma xenografts after short-course treatment with trametinib and TAK228, alone and in combination. We identified distinct response signatures for each monotherapy and combination therapy and validated that combination treatment inhibited activation of the MAPK and mTOR pathways, increased apoptotic signaling and suppressed angiogenesis signaling. Furthermore, we found that trametinib and TAK228 combination treatment broadly suppressed the activity of the cyclin-dependent kinases and increased the levels of proteins (and their activating phosphorylations) involved in glycolysis, the TCA cycle, nucleotide biosynthesis and DNA replication. We also demonstrated activation of both receptor tyrosine kinase and histone deacetylase proteins. This study reports a detailed (phospho)proteomic analysis of the response of BRAFV600E mutant glioma to combined MEK and mTOR pathway inhibition and identifies a number of targetable upregulated proteins and pathways, providing new avenues for the development of additional rational combination therapies for aggressive BRAF-driven tumors.

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Analysis of global RNA expression established that zebrafish brain tumors resemble GBMs of the mesenchymal subtype.

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