title: Rapid Conversion of Mutant IDH1 from Driver to Passenger in a Model of Human Gliomagenesis.
abstract: Missense mutations in the active site of isocitrate dehydrogenase 1 (IDH1) biologically and diagnostically distinguish low-grade gliomas and secondary glioblastomas from primary glioblastomas. IDH1 mutations lead to the formation of the oncometabolite 2-hydroxyglutarate (2-HG) from the reduction of α-ketoglutarate (α-KG), which in turn facilitates tumorigenesis by modifying DNA and histone methylation as well blocking differentiation processes. Although mutant IDH1 expression is thought to drive the gliomagenesis process, the extent to which it remains a viable therapeutic target remains unknown. To address this question, we exposed immortalized (p53/pRb deficient), untransformed human astrocytes to the mutant IDH1 inhibitor AGI-5198 prior to, concomitant with, or at intervals after, introduction of transforming mutant IDH1, then measured effects on 2-HG levels, histone methylation (H3K4me3, H3K9me2, H3K9me3, or H3K27me3), and growth in soft agar. Addition of AGI-5198 prior to, or concomitant with, introduction of mutant IDH1 blocked all mutant IDH1-driven changes, including cellular transformation. Addition at time intervals as short as 4 days following introduction of mutant IDH1 also suppressed 2-HG levels, but had minimal effects on histone methylation, and lost the ability to suppress clonogenicity in a time-dependent manner. Furthermore, in two different models of mutant IDH1-driven gliomagenesis, AGI-5198 exposures that abolished production of 2-HG also failed to decrease histone methylation, adherent cell growth, or anchorage-independent growth in soft agar over a prolonged period. These studies show although mutant IDH1 expression drives gliomagenesis, mutant IDH1 itself rapidly converts from driver to passenger.
  
  
  
  Agents that target mutant IDH may be effective for a narrow time and may require further optimization or additional therapeutics in glioma. Mol Cancer Res; 14(10); 976-83. ©2016 AACR.
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California. Department of Biomedicine, The Kristian Gerhard Jebsen Brain Tumor Research Centre, University of Bergen, Bergen, Norway.
authors.forename: Tor-Christian Aase
authors.initials: TA
authors.lastname: Johannessen
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California.
authors.forename: Joydeep
authors.initials: J
authors.lastname: Mukherjee
authors.affiliation: Department of Radiology, University of California, San Francisco, San Francisco, California.
authors.forename: Pavithra
authors.initials: P
authors.lastname: Viswanath
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ohba
authors.affiliation: Department of Radiology, University of California, San Francisco, San Francisco, California.
authors.forename: Sabrina M
authors.initials: SM
authors.lastname: Ronen
authors.affiliation: Department of Biomedicine, The Kristian Gerhard Jebsen Brain Tumor Research Centre, University of Bergen, Bergen, Norway.
authors.forename: Rolf
authors.initials: R
authors.lastname: Bjerkvig
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California. Russ.pieper@ucsf.edu.
authors.forename: Russell O
authors.initials: RO
authors.lastname: Pieper
mesh_terms: D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D044482:Benzeneacetamides / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D002478:Cells, Cultured; D005910:Glioma / Q000235:genetics*; D005977:Glutarates / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007521:Isocitrate Dehydrogenase / Q000037:antagonists & inhibitors / Q000235:genetics*; D008745:Methylation / Q000187:drug effects; D009154:Mutation / Q000187:drug effects
chemical_list: C581156:AGI-5198; D044482:Benzeneacetamides; D005977:Glutarates; D006657:Histones; D007093:Imidazoles; C019417:alpha-hydroxyglutarate; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human