title: Enhanced apoptosis and tumor regression induced by a direct agonist antibody to tumor necrosis factor-related apoptosis-inducing ligand receptor 2.
abstract: OBJECTIVE
  Substantial evidence indicates that supraoligomerization of the death receptors for Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is necessary for efficient activation of the apoptotic pathway. Bivalent IgG antibodies can induce the efficient apoptosis by mimicking the natural ligands but only after these antibodies are further oligomerized by cross-linking. In this study, we generated a novel agonist antibody to TRAIL receptor 2 (TRAIL-R2) capable of inducing apoptosis without cross-linking and elucidated its mode of action and efficacy.
  
  
  METHODS
  A fully human antibody to TRAIL-R2, KMTR2, was generated from KM Mouse immunized with TRAIL-R2 ectodomain. Apoptosis-inducing activities of unfractionated or purified monomeric IgG of KMTR2 was evaluated in the presence or absence of cross-linkers, secondary antibodies or Fc receptor-expressing effector cells, against human colorectal adenocarcinoma Colo205. Oligomerization of TRAIL-R2 was analyzed by size exclusion chromatography and confocal microscopy, and in vivo efficacy was examined in Colo205 xenograft model.
  
  
  RESULTS
  KMTR2 specifically recognized TRAIL-R2 and induced apoptosis with or without cross-linking. Size exclusion chromatography showed that the apoptosis activity coeluted with monomeric IgG and was effective independent of secondary antibody or Fc receptor-expressing effector cells. The antibody formed supracomplexes with soluble recombinant and membrane-anchored TRAIL-R2 and enhanced clustering of TRAIL-R2 on cell surface without cross-linking. KMTR2 was dramatically efficacious in reducing established human tumor.
  
  
  CONCLUSIONS
  Our findings indicate that novel agonist antibody KMTR2 can direct antibody-dependent oligomerization of TRAIL-R2 and initiates efficient apoptotic signaling and tumor regression independent of host effector function. Thus, the direct agonist would be a lead candidate for cancer therapeutics.
authors.affiliation: Pharmaceutical Research Laboratories, Kirin Brewery Co., Ltd., Gunma, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Motoki
authors.forename: Eiji
authors.initials: E
authors.lastname: Mori
authors.forename: Atsushi
authors.initials: A
authors.lastname: Matsumoto
authors.forename: Mayumi
authors.initials: M
authors.lastname: Thomas
authors.forename: Takafumi
authors.initials: T
authors.lastname: Tomura
authors.forename: Robin
authors.initials: R
authors.lastname: Humphreys
authors.forename: Vivian
authors.initials: V
authors.lastname: Albert
authors.forename: Mari
authors.initials: M
authors.lastname: Muto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Masami
authors.initials: M
authors.lastname: Aoki
authors.forename: Taro
authors.initials: T
authors.lastname: Tamada
authors.forename: Ryota
authors.initials: R
authors.lastname: Kuroki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yoshida
authors.forename: Isao
authors.initials: I
authors.lastname: Ishida
authors.forename: Carl F
authors.initials: CF
authors.lastname: Ware
authors.forename: Shiro
authors.initials: S
authors.lastname: Kataoka
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000918:Antibody Specificity; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000737:chemistry / Q000276:immunology*; D012074:Remission Induction; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
chemical_list: D000911:Antibodies, Monoclonal; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C505639:TNFRSF10B protein, human; C505640:Tnfrsf10b protein, mouse