title: Caspase activation and apoptosis induction by adalimumab: demonstration in vitro and in vivo in a chimeric mouse model.
abstract: BACKGROUND
  Adalimumab is a fully human monoclonal antibody to tumor necrosis factor (TNF), which was recently introduced as a therapy for Crohn's disease and rheumatoid arthritis. Besides neutralization, induction of apoptosis of monocytes/macrophages and T cells is thought to be an important mechanism of action of the anti-tumor necrosis factor monoclonal antibody infliximab, at least in Crohn's disease therapy.
  
  
  OBJECTIVE
  To study caspase activation and the induction of apoptosis by adalimumab and the effect of a caspase inhibitor in vivo.
  
  
  METHODS
  For in vitro studies, THP-1 cells (human monocytic cell line) were incubated with adalimumab, infliximab, or human immunoglobulin G, and annexin V + propidium iodide, Apo2.7, and 7-amino actinomycin-D were used to study apoptosis on the cell membrane, mitochodrial, and DNA level, respectively. Active caspase-3 was detected by intracellular staining. For in vivo studies, a chimeric human-mouse model was used, in which THP-1 cells were injected intraperitoneally in SCID-Beige mice followed by treatment with adalimumab, infliximab, or human immunoglobulin G. Effects of a pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyketone on apoptosis induction were evaluated.
  
  
  RESULTS
  In vitro analysis revealed that apoptosis could be induced in THP-1 cells by both adalimumab and infliximab. Activation of caspase-3 after incubation with adalimumab was demonstrated by intracellular staining. In addition, in the chimeric mouse model, a higher percentage of residual THP-1 cells were apoptotic, and lower cell numbers were recovered in the adalimumab- or infliximab-treated mouse. Apoptosis induction by adalimumab could be abrogated through in vivo pretreatment of mice with the pan-caspase inhibitor.
  
  
  CONCLUSIONS
  Adalimumab, besides neutralizing tumor necrosis factor, also induces apoptosis of transmembrane tumor necrosis factor-positive THP-1 cells by activating intracellular caspases. This activity is likely to be important for the clinical effect of this biodrug.
authors.affiliation: Laboratory of Experimental Immunology, Catholic University, Leuven, Belgium.
authors.forename: Chong
authors.initials: C
authors.lastname: Shen
authors.forename: Gert
authors.initials: G
authors.lastname: Van Assche
authors.forename: Paul
authors.initials: P
authors.lastname: Rutgeerts
authors.forename: Jan L
authors.initials: JL
authors.lastname: Ceuppens
mesh_terms: D000068879:Adalimumab; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002678:Chimera; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors; D005260:Female; D006801:Humans; D051379:Mice; D008815:Mice, Inbred Strains; D016513:Mice, SCID; D009000:Monocytes / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004792:Enzyme Precursors; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D000068879:Adalimumab