Investigating the Interaction of Upregulated Signaling Effectors in GBM Open Access

Allen, Jerry William (Spring 2019)

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Glioblastoma Multiforme (GBM) is the most common primary malignant brain tumor in adults worldwide and arises in glial cells and glial progenitors with a median over-all survival of those diagnosed being 15 months despite treatment. Despite extensive research on common genetic lesions that occur in GBM, such as overactivity of the RTK and PI3K signaling pathways, current therapies designed to target these known mechanisms are ineffective at treating the disease. Using a novel Drosophila GBM model, previous work in our laboratory identified Right Open Reading Frame 2 (dRIOK2) as an essential component of tumor cell maintenance and survival in RTK-PI3K-driven GBM. dRIOK2 is a highly conserved atypical serine-threonine kinase involved in ribosomal maturation with a known human ortholog, RIOK2. To understand downstream targets of RIOK2, we analyzed proteomic data from immunoprecipitation experiments of kinase-active and kinase-dead RIOK2 in a cultured-human GBM cell line and uncovered that kinase-active RIOK2 interacts with the RNA-binding protein IMP3, whose functions include the trafficking and translation of oncogenic mRNA such as MYC, IGF2, and CyclinD1. These data suggest a potential mechanism of the RIOK2-dependence observed in the Drosophila GBM model and validated in cultured human GBM cells. To investigate this potential relationship between RIOK2 and IMP3, we initially screened publicly-available expression data from the Cancer Genome Atlas (TCGA) and other databases by glioma grade and IDH1-mutant status. Preliminary data suggested RIOK2 and IMP3 were overexpressed in GBM, which we sought to validate using immunohistochemistry on tumor tissue microarrays to probe for co-overexpression of each protein in the same tissue samples. As a next step in our investigations of RIOK2 and IMP3, we will look to recapitulate the RIOK2-dependence findings from the Drosophila and human-cultured-cells GBM models in an inducible murine GBM model.

Table of Contents


Glioblastoma Multiforme Epidemiology & Etiology 1

Background & Preliminary Data       3

Hypothesis & Approach        5


The Cancer Genome Atlas (TCGA) & Assorted Database Analysis of Co-Expression           8

Immunohistochemistry and processing of Tumor microarray          9

qPCR for Validating in vitro Viral shRNA Knockdown       10

RESULTS      12

Database Analysis     12

qPCR of shRNA Infected mNSCs     15

IHC of Tumor Micoarray (TMA)      17


TABLE OF FIGURES           25

REFERENCES          26

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