Iodine-124 labelled annexin-V as a potential radiotracer to study apoptosis using positron emission tomography.
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.
Glaser
Matthias
M
Imaging Research Solutions Ltd, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK. m.glaser@csc.mrc.ac.uk
Collingridge
David R
DR
Aboagye
Eric O
EO
Bouchier-Hayes
Lisa
L
Hutchinson
O Clyde
OC
Martin
Seamus J
SJ
Price
Pat
P
Brady
Frank
F
Luthra
Sajinder K
SK
D017304:Annexin A5 / Q000737:chemistry* / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D001565:Benzoates / Q000737:chemistry; D002166:Camptothecin / Q000494:pharmacology; D002700:Chloramines / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D018922:HL-60 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes / Q000737:chemistry; D007553:Isotope Labeling / Q000379:methods; D011849:Radioactive Tracers; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D014055:Tomography, Emission-Computed; D014105:Tosyl Compounds / Q000737:chemistry; D014298:Trimethyltin Compounds / Q000737:chemistry; D014407:Tumor Cells, Cultured / Q000166:cytology
D017304:Annexin A5; D001565:Benzoates; D002700:Chloramines; D007457:Iodine Radioisotopes; D011849:Radioactive Tracers; D019275:Radiopharmaceuticals; D014105:Tosyl Compounds; D014298:Trimethyltin Compounds; C016300:chloramine-T; C061345:N-succinimidyl 3-(trimethylstannyl)benzoate; D002166:Camptothecin