title: Cytotoxicity of activated natural killer cells against pediatric solid tumors.
abstract: OBJECTIVE
  To develop new therapies for children with solid tumors, we tested the cytotoxicity of natural killer (NK) cells expanded by coculture with K562-mb15-41BBL cells. We sought to identify the most sensitive tumor subtypes, clarify the molecular interactions regulating cytotoxicity, and determine NK antitumor potential in vivo.
  
  
  METHODS
  We tested in vitro cytotoxicity of expanded NK cells against cell lines representative of Ewing sarcoma (EWS; n = 5), rhabdomyosarcoma (n = 4), neuroblastoma (n = 3), and osteosarcoma (n = 3), and correlated the results with expression of inhibitory and activating NK receptor ligands. We also compared expanded and primary NK cells, determined the effects of activating receptor ligation and of chemotherapeutic drugs, and assessed the therapeutic effect of NK cell infusions in xenografts.
  
  
  RESULTS
  In 45 experiments, EWS and rhabdomyosarcoma cell lines were remarkably sensitive to expanded NK cells, with median cytotoxicities at 1:1 effector/target ratio of 87.2% and 79.1%, respectively. Cytotoxicity was not related to levels of expression of NK receptor ligands, nor was it affected by pretreatment of target cells with daunorubicin or vincristine, but was markedly inhibited by preincubation of NK cells with a combination of antibodies against the NK-activating receptors NKGD2 and DNAM-1. Expanded NK cells were considerably more cytotoxic than unstimulated NK cells, and eradicated EWS cells engrafted in nonobese diabetic/severe combined immunodeficient Il2rgnull mice.
  
  
  CONCLUSIONS
  Among pediatric solid tumors, EWS and rhabdomyosarcoma are exquisitely sensitive to expanded NK cells. The NK expansion method described here has been adapted to large-scale conditions and supports a phase I clinical study including patients with these malignancies.
authors.affiliation: Department of Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
authors.forename: Duck
authors.initials: D
authors.lastname: Cho
authors.forename: David R
authors.initials: DR
authors.lastname: Shook
authors.forename: Noriko
authors.initials: N
authors.lastname: Shimasaki
authors.forename: Yu-Hsiang
authors.initials: YH
authors.lastname: Chang
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fujisaki
authors.forename: Dario
authors.initials: D
authors.lastname: Campana
mesh_terms: D000293:Adolescent; D000818:Animals; D045744:Cell Line, Tumor; D002648:Child; D003602:Cytotoxicity, Immunologic; D006801:Humans; D016219:Immunotherapy, Adoptive / Q000379:methods*; D007694:Killer Cells, Natural / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009369:Neoplasms / Q000276:immunology / Q000628:therapy*; D009447:Neuroblastoma / Q000628:therapy; D012516:Osteosarcoma / Q000628:therapy; D012208:Rhabdomyosarcoma / Q000276:immunology / Q000628:therapy; D012512:Sarcoma, Ewing / Q000276:immunology / Q000628:therapy; D023041:Xenograft Model Antitumor Assays