title: Enhancer of zeste homologue 2 plays an important role in neuroblastoma cell survival independent of its histone methyltransferase activity.
abstract: Neuroblastoma is predominantly characterised by chromosomal rearrangements. Next to V-Myc Avian Myelocytomatosis Viral Oncogene Neuroblastoma Derived Homolog (MYCN) amplification, chromosome 7 and 17q gains are frequently observed. We identified a neuroblastoma patient with a regional 7q36 gain, encompassing the enhancer of zeste homologue 2 (EZH2) gene. EZH2 is the histone methyltransferase of lysine 27 of histone H3 (H3K27me3) that forms the catalytic subunit of the polycomb repressive complex 2. H3K27me3 is commonly associated with the silencing of genes involved in cellular processes such as cell cycle regulation, cellular differentiation and cancer. High EZH2 expression correlated with poor prognosis and overall survival independent of MYCN amplification status. Unexpectedly, treatment of 3 EZH2-high expressing neuroblastoma cell lines (IMR32, CHP134 and NMB), with EZH2-specific inhibitors (GSK126 and EPZ6438) resulted in only a slight G1 arrest, despite maximum histone methyltransferase activity inhibition. Furthermore, colony formation in cell lines treated with the inhibitors was reduced only at concentrations much higher than necessary for complete inhibition of EZH2 histone methyltransferase activity. Knockdown of the complete protein with three independent shRNAs resulted in a strong apoptotic response and decreased cyclin D1 levels. This apoptotic response could be rescued by overexpressing EZH2ΔSET, a truncated form of wild-type EZH2 lacking the SET transactivation domain necessary for histone methyltransferase activity. Our findings suggest that high EZH2 expression, at least in neuroblastoma, has a survival function independent of its methyltransferase activity. This important finding highlights the need for studies on EZH2 beyond its methyltransferase function and the requirement for compounds that will target EZH2 as a complete protein.
authors.affiliation: Department of Translational Medicine, Prinses Máxima Center for Pediatric Oncology, Utrecht, The Netherlands.
authors.forename: Laurel T
authors.initials: LT
authors.lastname: Bate-Eya
authors.affiliation: Department of Pediatric Oncology, Emma Kinderziekenhuis, Amsterdam, The Netherlands.
authors.forename: Hinco J
authors.initials: HJ
authors.lastname: Gierman
authors.affiliation: Department of Translational Medicine, Prinses Máxima Center for Pediatric Oncology, Utrecht, The Netherlands.
authors.forename: Marli E
authors.initials: ME
authors.lastname: Ebus
authors.affiliation: Department of Oncogenomics Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Koster
authors.affiliation: Department of Pediatric Oncology, Emma Kinderziekenhuis, Amsterdam, The Netherlands.
authors.forename: Huib N
authors.initials: HN
authors.lastname: Caron
authors.affiliation: Department of Oncogenomics Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Rogier
authors.initials: R
authors.lastname: Versteeg
authors.affiliation: Department of Translational Medicine, Prinses Máxima Center for Pediatric Oncology, Utrecht, The Netherlands.
authors.forename: M Emmy M
authors.initials: MEM
authors.lastname: Dolman
authors.affiliation: Department of Translational Medicine, Prinses Máxima Center for Pediatric Oncology, Utrecht, The Netherlands. Electronic address: j.j.molenaar@prinsesmaximacentrum.nl.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Molenaar
mesh_terms: D001549:Benzamides / Q000494:pharmacology; D001713:Biphenyl Compounds; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D002869:Chromosome Aberrations; D002897:Chromosomes, Human, Pair 7; D015536:Down-Regulation / Q000187:drug effects; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000378:metabolism / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D015321:Gene Rearrangement; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors* / Q000502:physiology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D009025:Morpholines; D009447:Neuroblastoma / Q000201:enzymology* / Q000503:physiopathology; D011379:Prognosis; D011728:Pyridones / Q000494:pharmacology
chemical_list: D001549:Benzamides; D001713:Biphenyl Compounds; D004791:Enzyme Inhibitors; C577920:GSK-2816126; D007211:Indoles; D009025:Morpholines; D011728:Pyridones; D000076983:Histone Methyltransferases; D000071221:Enhancer of Zeste Homolog 2 Protein; D011495:Histone-Lysine N-Methyltransferase; C000593333:tazemetostat
keywords: Apoptosis; EPZ6438; EZH2; GSK126; Histone methyltransferase; Neuroblastoma