TY - JOUR
T1 - Radiolabeled isatin binding to caspase-3 activation induced by anti-Fas antibody
AU - Chen, Delphine L.
AU - Zhou, Dong
AU - Chu, Wenhua
AU - Herrbrich, Phillip
AU - Engle, Jacquelyn T.
AU - Griffin, Elizabeth
AU - Jones, Lynne A.
AU - Rothfuss, Justin M.
AU - Geraci, Marco
AU - Hotchkiss, Richard S.
AU - Mach, Robert H.
N1 - Funding Information:
The authors would like to thank Nicole Fettig, Margaret Morris, Amanda Roth, Ann Stroncek and Lori Strong in the Washington University MicroPET Facility for assistance with imaging and biodistribution studies and Richard Laforest for assistance in reconstructing the microPET images. These studies were funded by NIH HL13851 and EB006702 and the Damon Runyon Cancer Research Foundation through a Clinical Investigator Award to Dr. Chen.
PY - 2012/1
Y1 - 2012/1
N2 - Introduction: Noninvasive imaging methods that can distinguish apoptosis from necrosis may be useful in furthering our understanding of diseases characterized by apoptotic dysregulation as well as aiding drug development targeting apoptotic pathways. We evaluated the ability of radiolabeled isatins to quantify caspase-3 activity induced by the activation of the extrinsic apoptotic pathway by the anti-Fas antibody in mice. Methods: The behavior of three different radiolabeled isatins ([ 18F]WC-II-89, [ 18F]WC-IV-3 and [ 11C]WC-98) was characterized in mice with and without anti-Fas antibody treatment by microPET imaging and biodistribution studies. The activity of [ 18F]WC-II-89 was also compared with [ 99mTc]mebrofenin. The effect of pan-caspase inhibition with quinolyl-valyl-O-methylaspartyl-[2,6-difluorophenoxy]-methyl ketone (Q-VD-OPh) on [ 18F]WC-II-89 uptake was studied. Caspase-3 activity was confirmed by a fluorometric enzyme assay. Results: All three tracers behaved similarly in microPET and biodistribution studies. Increased retention of all tracers was observed in the livers of treated animals and several other organs, all of which demonstrated increased caspase-3 enzyme activity; however, impaired hepatobiliary excretion made attribution of these findings to caspase-3 activity difficult. The isatin [ 18F]WC-II-89 was retained at statistically significantly higher levels in the organs after anti-Fas antibody treatment while [ 99mTc]mebrofenin activity cleared, suggesting specific binding to activated caspase-3, but the magnitude of increased binding was still relatively low. Caspase inhibition with Q-VD-OPh partially blocked [ 18F]WC-II-89 retention but completely blocked caspase-3 enzyme activity in the liver. Conclusions: The radiolabeled isatins appear to bind specifically to caspase-3 in vivo, but their sensitivity is limited. Further optimization is required for these tracers to be useful for clinical applications.
AB - Introduction: Noninvasive imaging methods that can distinguish apoptosis from necrosis may be useful in furthering our understanding of diseases characterized by apoptotic dysregulation as well as aiding drug development targeting apoptotic pathways. We evaluated the ability of radiolabeled isatins to quantify caspase-3 activity induced by the activation of the extrinsic apoptotic pathway by the anti-Fas antibody in mice. Methods: The behavior of three different radiolabeled isatins ([ 18F]WC-II-89, [ 18F]WC-IV-3 and [ 11C]WC-98) was characterized in mice with and without anti-Fas antibody treatment by microPET imaging and biodistribution studies. The activity of [ 18F]WC-II-89 was also compared with [ 99mTc]mebrofenin. The effect of pan-caspase inhibition with quinolyl-valyl-O-methylaspartyl-[2,6-difluorophenoxy]-methyl ketone (Q-VD-OPh) on [ 18F]WC-II-89 uptake was studied. Caspase-3 activity was confirmed by a fluorometric enzyme assay. Results: All three tracers behaved similarly in microPET and biodistribution studies. Increased retention of all tracers was observed in the livers of treated animals and several other organs, all of which demonstrated increased caspase-3 enzyme activity; however, impaired hepatobiliary excretion made attribution of these findings to caspase-3 activity difficult. The isatin [ 18F]WC-II-89 was retained at statistically significantly higher levels in the organs after anti-Fas antibody treatment while [ 99mTc]mebrofenin activity cleared, suggesting specific binding to activated caspase-3, but the magnitude of increased binding was still relatively low. Caspase inhibition with Q-VD-OPh partially blocked [ 18F]WC-II-89 retention but completely blocked caspase-3 enzyme activity in the liver. Conclusions: The radiolabeled isatins appear to bind specifically to caspase-3 in vivo, but their sensitivity is limited. Further optimization is required for these tracers to be useful for clinical applications.
UR - http://www.scopus.com/inward/record.url?scp=84855337777&partnerID=8YFLogxK
U2 - 10.1016/j.nucmedbio.2011.08.001
DO - 10.1016/j.nucmedbio.2011.08.001
M3 - Article
C2 - 22033021
AN - SCOPUS:84855337777
SN - 0969-8051
VL - 39
SP - 137
EP - 144
JO - Nuclear Medicine and Biology
JF - Nuclear Medicine and Biology
IS - 1
ER -