Iodine-124 labelled annexin-V as a potential radiotracer to study apoptosis using positron emission tomography

Appl Radiat Isot. 2003 Jan;58(1):55-62. doi: 10.1016/s0969-8043(02)00239-7.


Annexin-V is a calcium-dependent protein that binds with high affinity to phosphaditylserine exposed during apoptosis. The aim of this study was to radiolabel annexin-V with iodine-124 for use as a potential probe of apoptosis by positron emission tomography. Annexin-V was radioiodinated directly using the cyclotron-produced positron emitter iodine-124 by the chloramine-T (CAT) method and indirectly by the pre-labelled reagent N-succinimidyl 3-[124I]iodobenzoate ([124I]m-SIB). Some reaction parameters of the CAT method such as reaction time and pH were optimised to give radiochemical yields of 22.3 +/- 2.6%(n = 3, gel-filtration). After incubation with [124I]m-SIB, radiolabelled annexin-V was obtained in 14% and 25% yield by FPLC and gel-filtration, respectively. The radiochemical purities from direct and indirect labelling were 97.7 +/- 1.0%(n = 3) and 96.7 +/- 2.1%(n = 3), respectively. The new radiotracers could be stored for up to four days without significant de-iodination. The biological activity of radiolabelled annexin-V was tested in control and camptothecin-treated (i.e. apoptotic) human leukaemic HL60 cells. A significantly higher (21%) binding in treated cells was observed with [125I]m-SIB-annexin-V. The binding of [125I]m-SIB labelled annexin-V to camptothecin treated cells was blocked (68%) by a 100-fold excess of unlabelled annexin-V.

MeSH terms

  • Annexin A5 / chemistry*
  • Annexin A5 / metabolism
  • Apoptosis / physiology*
  • Benzoates / chemistry
  • Camptothecin / pharmacology
  • Chloramines / chemistry
  • Chromatography, Liquid / methods
  • Drug Stability
  • Electrophoresis, Polyacrylamide Gel
  • HL-60 Cells
  • Humans
  • Hydrogen-Ion Concentration
  • Iodine Radioisotopes* / chemistry
  • Isotope Labeling / methods
  • Radioactive Tracers
  • Radiopharmaceuticals / chemical synthesis
  • Radiopharmaceuticals / chemistry*
  • Radiopharmaceuticals / metabolism
  • Tomography, Emission-Computed
  • Tosyl Compounds / chemistry
  • Trimethyltin Compounds / chemistry
  • Tumor Cells, Cultured / cytology


  • Annexin A5
  • Benzoates
  • Chloramines
  • Iodine Radioisotopes
  • Radioactive Tracers
  • Radiopharmaceuticals
  • Tosyl Compounds
  • Trimethyltin Compounds
  • chloramine-T
  • N-succinimidyl 3-(trimethylstannyl)benzoate
  • Camptothecin