title: Acquisition of a single EZH2 D1 domain mutation confers acquired resistance to EZH2-targeted inhibitors.
abstract: Although targeted therapies have revolutionized cancer treatment, overcoming acquired resistance remains a major clinical challenge. EZH2 inhibitors (EZH2i), EPZ-6438 and GSK126, are currently in the early stages of clinical evaluation and the first encouraging signs of efficacy have recently emerged in the clinic. To anticipate mechanisms of resistance to EZH2i, we used a forward genetic platform combining a mutagenesis screen with next generation sequencing technology and identified a hotspot of secondary mutations in the EZH2 D1 domain (Y111 and I109). Y111D mutation within the WT or A677G EZH2 allele conferred robust resistance to both EPZ-6438 and GSK126, but it only drove a partial resistance within the Y641F allele. EZH2 mutants required histone methyltransferase (HMT) catalytic activity and the polycomb repressive complex 2 (PRC2) components, SUZ12 and EED, to drive drug resistance. Furthermore, D1 domain mutations not only blocked the ability of EZH2i to bind to WT and A677G mutant, but also abrogated drug binding to the Y641F mutant. These data provide the first cellular validation of the mechanistic model underpinning the oncogenic function of WT and mutant EZH2. Importantly, our findings suggest that acquired-resistance to EZH2i may arise in WT and mutant EZH2 patients through a single mutation that remains targetable by second generation EZH2i.
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Baker
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Sujata
authors.initials: S
authors.lastname: Nerle
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Pritchard
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Boyang
authors.initials: B
authors.lastname: Zhao
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Rivera
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Garner
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA 02139, USA.
authors.forename: Francois
authors.initials: F
authors.lastname: Gonzalvez
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001549:Benzamides / Q000378:metabolism / Q000494:pharmacology*; D001713:Biphenyl Compounds; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D000071221:Enhancer of Zeste Homolog 2 Protein; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000378:metabolism / Q000494:pharmacology*; D058990:Molecular Targeted Therapy; D009025:Morpholines; D009154:Mutation; D009363:Neoplasm Proteins; D009369:Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D063151:Polycomb Repressive Complex 2 / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011728:Pyridones / Q000378:metabolism / Q000494:pharmacology*; D034622:RNA Interference; D013997:Time Factors; D014157:Transcription Factors; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D001713:Biphenyl Compounds; C491488:EED protein, human; D004791:Enzyme Inhibitors; C577920:GSK-2816126; D007211:Indoles; D009025:Morpholines; D009363:Neoplasm Proteins; D011728:Pyridones; C430461:SUZ12 protein, human; D014157:Transcription Factors; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; C000593333:tazemetostat
keywords: EZH2; cancer; drug resistance; epigenetics; mutation