An in vivo molecular imaging probe 18F-Annexin B1 for apoptosis detection by PET/CT: preparation and preliminary evaluation

Abstract

There is an increasing need to develop non-invasive molecular imaging strategies for visualizing and quantifying apoptosis status of diseases (especially for cancer) for diagnosis and monitoring treatment response. Since externalization of phosphatidylserine (PS) is one of the early molecular events during apoptosis, Annexin B1 (AnxB1), a member of Annexins family with high affinity toward the head group of PS, could be a potential positron emission tomography (PET) imaging probe for imaging cell death process after labeled by positron-emitting nuclides, such as (18)F. In the present study, we investigated a novel PET probe, (18)F-labeled Annexin B1 ((18)F-AnxB1), for apoptosis imaging. (18)F-AnxB1 was prepared reliably by conjugating AnxB1 with a (18)F-tag, N-succinimidyl 4-[(18)F]fluorobenzoate ([(18)F]SFB), in a radiolabeling yield of about 20 % within 40 min. The in vitro binding of (18)F-AnxB1 with apoptotic cells induced by anti-Fas antibody showed twofold increase compared to those without treatment, confirmed by flow cytometric analysis with AnxV-FITC/PI staining. Stability tests demonstrated (18)F-AnxB1 was rather stable in vitro and in vivo without degradation. The serial (18)F-AnxB1 PET/CT scans in healthy rats outlined its biodistribution and pharmacokinetics, indicating a rapid renal clearance and predominant accumulation into kidney and bladder at 2 h p.i. (18)F-AnxB1 PET/CT imaging was successfully applied to visualize in vivo apoptosis sites in tumor induced by chemotherapy and in kidney simulated by ischemia-reperfusion injury. The high-contrast images were obtained at 2 h p.i. to delineate apoptotic tumor. Apoptotic region could be still identified by (18)F-AnxB1 PET 4 h p.i., despite the high probe retention in kidneys. In summary, we have developed (18)F-AnxB1 as a PS-specific PET probe for the apoptosis detection and quantification which could have broad applications from disease diagnosis to treatment monitoring, especially in the cases of cancer.

Optimization of Early Response Monitoring and Prediction of Cancer Antiangiogenesis Therapy via Noninvasive PET Molecular Imaging Strategies of Multifactorial Bioparameters

“…Oborski et al subsequently reported the successful use of 18 F-ML-10 PET for the early response assessment of radiotherapy in glioblastoma multiforme patients 32 . In addition to 18 F-ML-10, the radionuclides 99m Tc- and 18 F-labeled Annexins play important roles in apoptosis imaging 33 , 34 . However, these Annexin-based probes have been associated with substantial challenges in monitoring the therapy efficacy, such as AAT, in clinical trials.…”

Molecular PET Imaging of Cyclophosphamide Induced Apoptosis with18F-ML-8

“…Cells at the logarithmic growth phase were harvested and adjusted to a concentration of 10 6 /mL in PBS, pH 7.5. Binding assays were performed as previously described [ 19 , 21 – 23 ].…”

Imaging calreticulin for early detection of immunogenic cell death during anticancer treatment

“…N-succinimidyl 4-fluorobenzoate (SFB) and ethyl 4-(trimethyl-ammonium) benzoate ( 18 F-SFB precursor) were prepared as previously described (13,14), with some modifications. 18 F-CRTpep was synthesized using modifications of previously reported methods (15,16). First, 18 F-SFB was synthesized to an approximately 30%240% (non-decay-corrected) radiochemical yield; the radiochemical purity was more than 98%.…”