title: In vitro experimental (211)At-anti-CD33 antibody therapy of leukaemia cells overcomes cellular resistance seen in vivo against gemtuzumab ozogamicin.
abstract: OBJECTIVE
  Monoclonal anti-CD33 antibodies conjugated with toxic calicheamicin derivative (gemtuzumab ozogamicin, GO) are a novel therapy option for acute myeloid leukaemia (AML). Key prognostic factors for patients with AML are high CD33 expression on the leukaemic cells and the ability to overcome mechanisms of resistance to cytotoxic chemotherapies, including drug efflux or other mechanisms decreasing apoptosis. Alpha particle-emitting radionuclides overwhelm such anti-apoptotic mechanisms by producing numerous DNA double-stranded breaks (DSBs) accompanied by decreased DNA repair.
  
  
  METHODS
  We labelled anti-CD33 antibodies with the alpha-emitter (211)At and compared survival of leukaemic HL-60 and K-562 cells treated with the (211)At-labelled antibodies, GO or unlabelled antibodies as controls. We also measured caspase-3/7 activity, DNA fragmentation and necrosis in HL-60 cells after treatment with the different antibodies or with free (211)At.
  
  
  RESULTS
  The mean labelling ratio of (211)At-labelled antibodies was 1:1,090 +/- 364 (range: 1:738-1:1,722) in comparison to 2-3:1 for GO. Tumour cell binding of (211)At-anti-CD33 was high in the presence of abundant CD33 expression and could be specifically blocked by unlabelled anti-CD33. (211)At-anti-CD33 decreased survival significantly more than did GO at comparable dilution (1:1,000). No significant differences in induction of apoptosis or necrosis or DNA DSB or in decreased survival were observed after (211)At-anti-CD33 (1:1,090) versus GO (1:1) treatment.
  
  
  CONCLUSIONS
  Our results suggest that (211)At is a promising, highly cytotoxic radioimmunotherapy in CD33-positive leukaemia and kills tumour cells more efficiently than does calicheamicin-conjugated antibody. Labelling techniques leading to higher chemical yield and specific activities must be developed to increase (211)At-anti-CD33 therapeutic effects.
authors.affiliation: Department of Nuclear Medicine, Hanover University School of Medicine, Carl-Neuberg-Str. 1, 30625, Hanover, Germany. Petrich.Thorsten@mh-hannover.de
authors.forename: Thorsten
authors.initials: T
authors.lastname: Petrich
authors.forename: Zekiye
authors.initials: Z
authors.lastname: Korkmaz
authors.forename: Doris
authors.initials: D
authors.lastname: Krull
authors.forename: Cornelia
authors.initials: C
authors.lastname: Frömke
authors.forename: Geerd J
authors.initials: GJ
authors.lastname: Meyer
authors.forename: Wolfram H
authors.initials: WH
authors.lastname: Knapp
mesh_terms: D000512:Alpha Particles; D000617:Aminoglycosides / Q000494:pharmacology* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D015703:Antigens, CD / Q000276:immunology* / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000276:immunology* / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001246:Astatine / Q000737:chemistry / Q000627:therapeutic use*; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D000079982:Gemtuzumab; D015972:Gene Expression Regulation, Neoplastic; D018922:HL-60 Cells; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D020014:K562 Cells; D007938:Leukemia / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D009336:Necrosis / Q000188:drug therapy; D063268:Sialic Acid Binding Ig-like Lectin 3; D013997:Time Factors
chemical_list: D000617:Aminoglycosides; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D018796:Immunoconjugates; D063268:Sialic Acid Binding Ig-like Lectin 3; D000079982:Gemtuzumab; D020169:Caspases; D001246:Astatine