title: EZH2 promotes E2F-driven SCLC tumorigenesis through modulation of apoptosis and cell-cycle regulation.
abstract: BACKGROUND
  Although enhancer of zeste homolog 2 (EZH2) has been associated with both non-small cell and small-cell lung cancers (SCLCs), current observations suggest different mechanisms of EZH2 activation and overexpression in these lung cancer types. Globally, SCLC kills 200,000 people yearly. New clinical approaches for SCLC treatment are required to improve the poor survival rate. Given the therapeutic potential of EZH2 as a target, we sought to delineate the downstream consequences of EZH2 disruption to identify the cellular mechanisms by which EZH2 promotes tumorigenesis in SCLC.
  
  
  METHODS
  We generated cells with stable expression of short hairpin RNA targeting EZH2 and corresponding controls (pLKO.1) and determined the consequences of EZH2 knockdown on the cell cycle and apoptosis by means of propidium iodide staining and fluorescence-activated cell sorting, Western blot, quantitative reverse transcriptase-polymerase chain reaction as well as cell viability assessment using methylthiazol tetrazolium assays.
  
  
  RESULTS
  We discovered that EZH2 inhibition (1) increased apoptotic activity by up-regulating the proapoptotic factors Puma and Bad, (2) decreased the fraction of cells in S or G2/M phases, and (3) elevated p21 protein levels, implicating EZH2 in cell death and cell-cycle control in SCLC.
  
  
  CONCLUSIONS
  Our findings present evidence for the role of EZH2 in the regulation of cell cycle and apoptosis, providing a biological mechanism to explain the tumorigenicity of EZH2 in SCLC. Our work points to the great potential of EZH2 as a therapeutic target in SCLC.
authors.affiliation: Integrative Oncology, British Columbia Cancer Research Centre, Vancouver, British Columbia, Canada. rhubaux@bccrc.ca
authors.forename: Roland
authors.initials: R
authors.lastname: Hubaux
authors.forename: Kelsie L
authors.initials: KL
authors.lastname: Thu
authors.forename: Bradley P
authors.initials: BP
authors.lastname: Coe
authors.forename: Calum
authors.initials: C
authors.lastname: MacAulay
authors.forename: Stephen
authors.initials: S
authors.lastname: Lam
authors.forename: Wan L
authors.initials: WL
authors.lastname: Lam
mesh_terms: D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology; D050684:E2F Transcription Factors / Q000502:physiology*; D000071221:Enhancer of Zeste Homolog 2 Protein; D006801:Humans; D008175:Lung Neoplasms / Q000209:etiology* / Q000473:pathology; D063151:Polycomb Repressive Complex 2 / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D055752:Small Cell Lung Carcinoma / Q000209:etiology* / Q000473:pathology
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050684:E2F Transcription Factors; D034741:RNA, Small Interfering; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2