Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake.
OBJECTIVE: Annexin A5 is a phosphatidylserine binding protein that binds dying cells in vivo. Annexin A5 is a potential molecular imaging agent to determine efficacy of anti-cancer therapy in patients. Its rapid clearance from circulation limits tumor uptake and, hence, its sensitivity. The aim of t...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2014-01-01
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| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC4011958?pdf=render |
| _version_ | 1811236366813495296 |
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| author | Lisette Ungethüm Martijn Chatrou Dennis Kusters Leon Schurgers Chris P Reutelingsperger |
| author_facet | Lisette Ungethüm Martijn Chatrou Dennis Kusters Leon Schurgers Chris P Reutelingsperger |
| author_sort | Lisette Ungethüm |
| collection | DOAJ |
| description | OBJECTIVE: Annexin A5 is a phosphatidylserine binding protein that binds dying cells in vivo. Annexin A5 is a potential molecular imaging agent to determine efficacy of anti-cancer therapy in patients. Its rapid clearance from circulation limits tumor uptake and, hence, its sensitivity. The aim of this study is to determine if non-invasive imaging of cell death in tumors will benefit from increasing circulation time of annexin A5 by increasing its size. PROCEDURES: Annexin A5 size was increased by complexation of biotinylated annexin A5 with Alexa-Fluor680-labeled streptavidin. The non-binding variant of annexin A5, M1234, was used as negative control. The HT29 colon carcinoma xenograft model in NMRI nude mice was used to measure tumor uptake in vivo. Tumor uptake of fluorescent annexin A5-variants was measured using non-invasive optical imaging. RESULTS: The annexin A5-streptavidin complex (4 ∶ 1, moles:moles, Mw ∼ 200 kDa) binds phosphatidylserine-expressing membranes with a Hill-coefficient of 5.7 ± 0.5 for Ca2+-binding and an EC50 of 0.9 ± 0.1 mM Ca2+ (EC50 is the Ca2+ concentration required for half maximal binding)(annexin A5: Hill-coefficient 3.9 ± 0.2, EC50 1.5 ± 0.2 mM Ca2+). Circulation half-life of annexin A5-streptavidin is ± 21 minutes (circulation half-life of annexin A5 is ± 4 min.). Tumor uptake of annexin A5-streptavidin was higher and persisted longer than annexin A5-uptake but depended less on phosphatidylserine binding. CONCLUSION: Increasing annexin A5 size prolongs circulation times and increases tumor uptake, but decreases contribution of PS-targeting to tumor uptake and abolishes power to report efficacy of therapy. |
| first_indexed | 2024-04-12T12:07:52Z |
| format | Article |
| id | doaj.art-4d40efdb47d64d87920a53357e92b364 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-04-12T12:07:52Z |
| publishDate | 2014-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-4d40efdb47d64d87920a53357e92b3642022-12-22T03:33:39ZengPublic Library of Science (PLoS)PLoS ONE1932-62032014-01-0195e9674910.1371/journal.pone.0096749Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake.Lisette UngethümMartijn ChatrouDennis KustersLeon SchurgersChris P ReutelingspergerOBJECTIVE: Annexin A5 is a phosphatidylserine binding protein that binds dying cells in vivo. Annexin A5 is a potential molecular imaging agent to determine efficacy of anti-cancer therapy in patients. Its rapid clearance from circulation limits tumor uptake and, hence, its sensitivity. The aim of this study is to determine if non-invasive imaging of cell death in tumors will benefit from increasing circulation time of annexin A5 by increasing its size. PROCEDURES: Annexin A5 size was increased by complexation of biotinylated annexin A5 with Alexa-Fluor680-labeled streptavidin. The non-binding variant of annexin A5, M1234, was used as negative control. The HT29 colon carcinoma xenograft model in NMRI nude mice was used to measure tumor uptake in vivo. Tumor uptake of fluorescent annexin A5-variants was measured using non-invasive optical imaging. RESULTS: The annexin A5-streptavidin complex (4 ∶ 1, moles:moles, Mw ∼ 200 kDa) binds phosphatidylserine-expressing membranes with a Hill-coefficient of 5.7 ± 0.5 for Ca2+-binding and an EC50 of 0.9 ± 0.1 mM Ca2+ (EC50 is the Ca2+ concentration required for half maximal binding)(annexin A5: Hill-coefficient 3.9 ± 0.2, EC50 1.5 ± 0.2 mM Ca2+). Circulation half-life of annexin A5-streptavidin is ± 21 minutes (circulation half-life of annexin A5 is ± 4 min.). Tumor uptake of annexin A5-streptavidin was higher and persisted longer than annexin A5-uptake but depended less on phosphatidylserine binding. CONCLUSION: Increasing annexin A5 size prolongs circulation times and increases tumor uptake, but decreases contribution of PS-targeting to tumor uptake and abolishes power to report efficacy of therapy.http://europepmc.org/articles/PMC4011958?pdf=render |
| spellingShingle | Lisette Ungethüm Martijn Chatrou Dennis Kusters Leon Schurgers Chris P Reutelingsperger Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. PLoS ONE |
| title | Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. |
| title_full | Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. |
| title_fullStr | Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. |
| title_full_unstemmed | Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. |
| title_short | Molecular imaging of cell death in tumors. Increasing annexin A5 size reduces contribution of phosphatidylserine-targeting function to tumor uptake. |
| title_sort | molecular imaging of cell death in tumors increasing annexin a5 size reduces contribution of phosphatidylserine targeting function to tumor uptake |
| url | http://europepmc.org/articles/PMC4011958?pdf=render |
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