Evaluation of a 99mTc-labeled AnnexinA5 variant for non-invasive SPECT imaging of cell death in liver, spleen and prostate.
OBJECTIVE
We investigate radio-labeling and pharmacokinetics of a new AnnexinA5 variant (HYNIC-cys-AnxA5) and then assess its utility for the non-invasive detection of cell death in liver, spleen and prostate.


METHODS
AnnexinA5 binds to phosphatidylserine expressed on the surface of apoptotic and necrotic cells. Contrary to other AnnexinA5 variants, the new cys-AnxA5 allows for site-specific conjugation of a hydrazinonicotinamide-maleimide moiety and subsequent radio-labeling with (99m)Tc at a position not involved in the AnxA5-phosphatidylserine interaction. Distribution of (99m)Tc-HYNIC-cys-AnxA5 was studied in rats, both invasively and via SPECT/CT. Cycloheximide was used to induce cell death in liver and spleen, whereas apoptosis in the prostate was induced by castration.


RESULTS
HYNIC-cys-AnxA5 was efficiently and reproducibly labeled with (99m)Tc. Blood clearance of radioactivity after iv-injection was adequately described by a two-compartment model, the renal cortex representing the main site of accumulation. Cycloheximide treatment resulted in increased accumulation of intravenous-injected (99m)Tc-HYNIC-cys-AnxA5 in liver and spleen over controls, which correlated well with TUNEL staining for cell death in corresponding tissue sections. However, the increase in TUNEL-positive prostate epithelial cells observed following castration was not paralleled by greater (99m)Tc-HYNIC-cys-AnxA5 accumulation.


CONCLUSIONS
(99m)Tc-HYNIC-cys-AnxA5 appears a suitable tracer for assessment of cell death in liver and spleen, but not prostate.
Schering-Plough Research Institute, Oss, The Netherlands. rick.greupink@spcorp.com
Rick
R
Greupink
Charles F
CF
Sio
Antwan
A
Ederveen
Joke
J
Orsel
D000818:Animals; D017304:Annexin A5 / Q000737:chemistry / Q000493:pharmacokinetics; D016923:Cell Death; D003545:Cysteine / Q000737:chemistry; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D011467:Prostate / Q000000981:diagnostic imaging* / Q000473:pathology; D011877:Radionuclide Imaging; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000000981:diagnostic imaging* / Q000473:pathology
D017304:Annexin A5; D015609:Organotechnetium Compounds; D003545:Cysteine