Abstract 41: DCA bind to EGFR/EGFRvIII/PDK1 and affect the proliferation and growth in TMZ resistant glioblastoma model

Abstract

Abstract Glioblastomas are characterized by amplification of epidermal growth factor receptor (EGFR). Approximately half of the GBM tumors with EGFR over-expression also express a constitutively active ligand independent EGFR variant III (EGFRvIII). This phenotype represents a tumor specific target correlating with a high growth potential. Despite advances in treatment, whether surgery, chemotherapeutics or molecular targeted therapies, very few have shown promise. Temozolomide (TMZ), as standard of care alkylation therapy, demonstrates improved survival when administered with concomitant radiotherapy. Unfortunately, acquired TMZ chemo-resistance is observed in more than 90% of recurrent GBMs. To understand the mechanisms in the context of TMZ resistance, we generated an in vitro TMZ resistant model by continuous exposure of U373 cells constitutively expressing EGFRvIII (U373vIII) to 150uM TMZ for 6 months (U373vIIIR). Dicholoroacetate (DCA) is a known metabolic inhibitor of pyruvate dehydrogenase kinase 1 (PDK1). Its application to cancer has recently been revived in the realm of metabolic oncology, where reversal of the Warburg effect has resulted in decreased tumor growth. Treatment of U373, U373vIII, and U373vIIIR GBM cell lines with DCA was found to induce cytotoxicity and reduced cell survival across all cell lines. Further, micro array studies conducted on U373vIII or U373vIIIR and their subsequent treatment with DCA revealed that PDK1 is the sole target in TMZ resistant tumors expressing EGFRvIII. Additionally, we demonstrated that 1mM DCA induced mitochondrial membrane potential change as evidenced in JC-1 staining and electron microscopic studies confirming mitochondrial apoptosis. Consistent with our previous findings that EGFR interacts with PDK1, our computational analysis revealed that DCA aligns itself to the binding sites of both EGFR and EGFRvIII with strong binding affinity apart from its binding to PDK1. Clinically, expression of EGFRvIII correlated with PDK1 when compared to EGFR in GBM surgical specimens. Collectively, our studies demonstrate that principles of metabolic oncology and DCA are active in GBM treatment despite resistance providing new insight into the development of alternative treatment in TMZ failure. Citation Format: Kiran Kumar Velpula, Kamlesh Sahu, Jack Tuszynski, Maheedhara R. Guda, Swapna Asuthkar, Sarah E. Martin, Justin D. Lathia, Andrew J. Tsung. DCA bind to EGFR/EGFRvIII/PDK1 and affect the proliferation and growth in TMZ resistant glioblastoma model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 41.