title: In vitro selectivity, in vivo biodistribution and tumour uptake of annexin V radiolabelled with a positron emitting radioisotope.
abstract: The availability of a noninvasive method to detect and quantify apoptosis in tumours will enable tumour response to several cancer therapies to be assessed. We have synthesised two radiotracers, annexin V and the N-succinimidyl-3-iodobenzoic acid (SIB) derivative of annexin V, labelled with radio-iodine ((124)I and (125)I) and provided proof of the concept by assessing specific binding and biodistribution of these probes to apoptotic cells and tumours. We have also assessed the tumour uptake of [(124)I]annexin V in a mouse model of apoptosis. RIF-1 cells induced to undergo apoptosis in vitro showed a drug concentration-dependent increased binding of [(125)I]annexin V and [(125)I]SIB-annexin V. In the same model system, there was an increase in terminal deoxynucleotidyl transferase-mediated nick end labelling (TUNEL)-positive cells and a decrease in clonogenic survival. Radiotracer binding was completely inhibited by preincubation with unlabelled annexin V. In RIF-1 tumour-bearing mice, rapid distribution of [(125)I]SIB-annexin V-derived radioactivity to kidneys was observed and the radiotracer accumulated in urine. The binding of [(125)I]SIB-annexin V to RIF-1 tumours increased by 2.3-fold at 48 h after a single intraperitoneal injection of 5-fluorouracil (165 mg kg(-1) body weight), compared to a 4.4-fold increase in TUNEL-positive cells measured by immunostaining. Positron emission tomography images with both radiotracers demonstrated intense localisation in the kidneys and bladder. Unlike [(124)I]SIB-annexin V, [(124)I]annexin V also showed localisation in the thyroid region presumably due to deiodination of the radiolabel. [(124)I]SIB-annexin V is an attractive candidate for in vivo imaging of apoptosis by PET.
authors.affiliation: Department of Cancer Medicine, Imperial College of Science Technology and Medicine, MRC Cyclotron Building, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK.
authors.forename: D R
authors.initials: DR
authors.lastname: Collingridge
authors.forename: M
authors.initials: M
authors.lastname: Glaser
authors.forename: S
authors.initials: S
authors.lastname: Osman
authors.forename: H
authors.initials: H
authors.lastname: Barthel
authors.forename: O C
authors.initials: OC
authors.lastname: Hutchinson
authors.forename: S K
authors.initials: SK
authors.lastname: Luthra
authors.forename: F
authors.initials: F
authors.lastname: Brady
authors.forename: L
authors.initials: L
authors.lastname: Bouchier-Hayes
authors.forename: S J
authors.initials: SJ
authors.lastname: Martin
authors.forename: P
authors.initials: P
authors.lastname: Workman
authors.forename: P
authors.initials: P
authors.lastname: Price
authors.forename: E O
authors.initials: EO
authors.lastname: Aboagye
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000493:pharmacokinetics*; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use; D017209:Apoptosis; D003839:Deoxyadenosines / Q000493:pharmacokinetics; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D005354:Fibrosarcoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D005434:Flow Cytometry; D005472:Fluorouracil / Q000627:therapeutic use; D006801:Humans; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods; D051379:Mice; D008809:Mice, Inbred C3H; D011485:Protein Binding; D012513:Sarcoma, Experimental / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D013872:Thionucleosides / Q000493:pharmacokinetics; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed; D014407:Tumor Cells, Cultured
chemical_list: D017304:Annexin A5; D000964:Antimetabolites, Antineoplastic; D003839:Deoxyadenosines; D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D013872:Thionucleosides; C013919:5'-deoxy-5'-S-isobutylthioadenosine; D005472:Fluorouracil