Glioblastoma (GBM) is the most common malignant primary brain tumor. Receptor tyrosine kinase (RTK) pathways are frequently mutated in GBM, including alterations in the RTK Epidermal Growth Factor Receptor (EGFR). Moreover, EGFR variant III (EGFRvIII) is the most common activating mutation in GBM. Given its frequency, specificity, and role in promoting gliomagenesis, EGFR dysfunction is a prime target for drug treatment. However, multiple resistance mechanisms, such as co-occurrence of EGFRvIII and deletion of the tumor suppressor PTEN, prevent effective treatment via activation of alternate kinase pathways. To observe the differential kinase activation involved in EGFRvIII- and PTEN loss- driven gliomagenesis and identify potential kinase targets for dual therapy, we examined immortalized murine astrocytes derived from non-germline genetically engineered mouse models expressing four core genotypes: wild-type EGFR + wild-type Pten (C), wild-type EGFR + Pten deletion (CP), EGFRvIII + wild-type Pten (CEv3), and EGFRvIII + Pten deletion (CEv3P). We used RNA sequencing and multiplexed inhibitor bead affinity chromatography and mass spectrometry (MIB-MS) to determine the baseline transcriptomes and kinomes of each genotype. We determined that cell lines exhibited genotype-dependent baseline RNA expression and kinase activity as a result of EGFRvIII and/or Pten deletion relative to C astrocytes and across genotypes. We observed several differentially-activated kinases that represent potential targets for dual treatment with EGFR TKI. We are currently examining changes in the kinome profile of each cell line after both acute and chronic treatment with tyrosine kinase inhibitors (TKI). These results will help define the kinase networks involved in tumor development and resistance and may aid in the identification of potential personalized combination therapy with EGFR TKI for GBM patients.Bachelor of Scienc
