Mechanisms and Antitumor Activity of a Binary EGFR/DNA-Targeting Strategy Overcomes Resistance of Glioblastoma Stem Cells to Temozolomide

• Published in: Clinical cancer research 2019-12, Vol.25 (24), p.7594-7608
• Main Authors: Sharifi, Zeinab, Abdulkarim, Bassam, Meehan, Brian, Rak, Janusz, Daniel, Paul, Schmitt, Julie, Lauzon, Nidia, Eppert, Kolja, Duncan, Heather M, Petrecca, Kevin, Guiot, Marie-Christine, Jean-Claude, Bertrand, Sabri, Siham
• Format: Article
• Language: English
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-19-0955

Glioblastoma (GBM) is a fatal primary malignant brain tumor. GBM stem cells (GSC) contribute to resistance to the DNA-damaging chemotherapy, temozolomide. The epidermal growth factor receptor (EGFR) displays genomic alterations enabling DNA repair mechanisms in half of GBMs. We aimed to investigate EGFR/DNA combi-targeting in GBM. ZR2002 is a "combi-molecule" designed to inflict DNA damage through its chlorethyl moiety and induce irreversible EGFR tyrosine kinase inhibition. We assessed its efficacy in temozolomide-resistant patient-derived GSCs, mesenchymal temozolomide-sensitive and resistant -derived GSC sublines, and U87/EGFR isogenic cell lines stably expressing EGFR/wild-type or variant III (EGFRvIII). We evaluated its antitumor activity in mice harboring orthotopic EGFRvIII or mesenchymal TMZ-resistant GSC tumors. ZR2002 induced submicromolar antiproliferative effects and inhibited neurosphere formation of all GSCs with marginal effects on normal human astrocytes. ZR2002 inhibited EGF-induced autophosphorylation of EGFR, downstream Erk1/2 phosphorylation, increased DNA strand breaks, and induced activation of wild-type p53; the latter was required for its cytotoxicity through p53-dependent mechanism. ZR2002 induced similar effects on U87/EGFR cell lines and its oral administration significantly increased survival in an orthotopic EGFRvIII mouse model. ZR2002 improved survival of mice harboring intracranial mesenchymal temozolomide-resistant GSC line, decreased EGFR, Erk1/2, and AKT phosphorylation and was detected in tumor brain tissue by MALDI imaging mass spectrometry. These findings provide the molecular basis of binary EGFR/DNA targeting and uncover the oral bioavailability, blood-brain barrier permeability, and antitumor activity of ZR2002 supporting potential evaluation of this first-in-class drug in recurrent GBM.