title: The narrow-spectrum HDAC inhibitor entinostat enhances NKG2D expression without NK cell toxicity, leading to enhanced recognition of cancer cells.
abstract: OBJECTIVE
  Natural killer (NK) cell cytotoxicity correlates with the ligation of activating receptors (e.g., NKG2D) by their ligands (e.g., MHC class I-related chains [MIC] A and B) on target cells. Histone deacetylase inhibitors (HDACi) at high concentrations inhibit tumor growth and can increase NKG2D ligand expression on tumor targets, but are widely regarded as toxic to NK cells.
  
  
  METHODS
  We investigated the mechanism of entinostat, a benzamide-derivative narrow-spectrum HDACi, in augmenting the cytotoxicity of NK cells against human colon carcinoma and sarcoma by assessing gene and protein expression, histone acetylation, and cytotoxicity in in vitro and murine models.
  
  
  RESULTS
  We observed that entinostat dose- and time-dependent increase in MIC expression in tumor targets and NKG2D in primary human NK cells, both correlating with increased acetylated histone 3 (AcH3) binding to associated promoters. Entinostat pretreatment of colon carcinoma and sarcoma cells, NK cells, or both led to enhanced overall cytotoxicity in vitro, which was reversed by NKG2D blockade, and inhibited growth of tumor xenografts. Lastly, we showed decreased expression of MICA and ULBP2 transcription in primary human osteosarcoma.
  
  
  CONCLUSIONS
  Entinostat enhances NK cell killing of cancer cells through upregulation of both NKG2D and its ligands, suggesting an attractive approach for augmenting NK cell immunotherapy of solid tumors such as colon carcinoma and sarcomas.
authors.affiliation: Shanghai University of Traditional Chinese Medicine School of Basic Medical Sciences, Shanghai, China, jusco105@hotmail.com.
authors.forename: Shiguo
authors.initials: S
authors.lastname: Zhu
authors.forename: Cecele J
authors.initials: CJ
authors.lastname: Denman
authors.forename: Zehra S
authors.initials: ZS
authors.lastname: Cobanoglu
authors.forename: Simin
authors.initials: S
authors.lastname: Kiany
authors.forename: Ching C
authors.initials: CC
authors.lastname: Lau
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Gottschalk
authors.forename: Dennis P M
authors.initials: DP
authors.lastname: Hughes
authors.forename: Eugenie S
authors.initials: ES
authors.lastname: Kleinerman
authors.forename: Dean A
authors.initials: DA
authors.lastname: Lee
mesh_terms: D000107:Acetylation; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000633:toxicity; D001549:Benzamides / Q000494:pharmacology* / Q000633:toxicity; D001665:Binding Sites; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology* / Q000633:toxicity; D006657:Histones / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D016688:Mice, Inbred NOD; D008822:Mice, Transgenic; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000276:immunology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011725:Pyridines / Q000494:pharmacology* / Q000633:toxicity; D012509:Sarcoma / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D014158:Transcription, Genetic; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D036341:Intercellular Signaling Peptides and Proteins; C527085:KLRK1 protein, human; D008024:Ligands; C099187:MHC class I-related chain A; C098080:MICB antigen; D055655:NK Cell Lectin-Like Receptor Subfamily K; D011725:Pyridines; C423230:ULBP2 protein, human; C118739:entinostat