Melinda Wuest

Cross Cancer Institute, Edmonton, Alberta, Canada

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Publications (66)183.1 Total impact

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    ABSTRACT: Dysregulation of tropomyosin receptor kinases (TrkA/B/C) expression and signalling is recognized as a hallmark of numerous neurodegenerative diseases including Parkinson's, Huntington's and Alzheimer's disease. TrkA/B/C is known to drive tumorogensis and metastatic potential in a wide range of neurogenic and non-neurogenic human cancers. The development of suitable positron emission tomography (PET) radioligands would allow an in vivo exploration of this versatile potential therapeutic target. Herein, the rational remodeling of the amide moiety of a 6-(2-(3-fluorophenyl)pyrrolidin-1-yl)imidazo[1,2-b]pyridazine-3-amide lead structure to accommodate efficient fluorine-18 labeling led to the identification of a series of fluorinated Trk inhibitors with picomolar IC50. The ensuing representative radiolabeled inhibitors [18F]16 ([18F]-(±)-IPMICF6) and [18F]27 ([18F]-(±)-IPMICF10) constitute novel lead radioligands with about 2- to 3- orders of magnitude increased TrkB/C potencies compared to previous lead tracers and display favorable selectivity profiles and physicochemical parameters for translation into in vivo PET imaging agents.
    No preview · Article · Dec 2015 · Medicinal Chemistry Communication
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    ABSTRACT: Lysyl oxidase (LOX; ExPASy ENZYME entry: EC and members of the LOX-like family, LOXL1-LOXL4, are copper-dependent enzymes that can modify proteins of the extracellular matrix. Expression of LOX is elevated in many human cancers, including breast cancer. LOX expression correlates with the level of tissue hypoxia, and it is known to play a critical role in breast cancer metastasis. The goal of the present study was to target LOX with (1) molecular probe fluorescent labeling to visualize LOX in vitro and (2) a radiolabeled peptide to target LOX in vivo in three different preclinical models of breast cancer. Gene expression of all five members of the LOX family was analyzed at the transcript level via microarray analysis using tissue biopsy samples from 176 patients with breast cancer. An oligopeptide sequence (GGGDPKGGGGG) was selected as a substrate-based, LOX-targeting structure. The peptide was labeled with fluorescein isothiocyanate (FITC) for confocal microscopy experiments with the murine breast cancer cell line EMT-6. In vivo molecular imaging experiments were performed using a C-terminal amidated peptide, GGGDPKGGGGG, labeled with a short-lived positron emitter, fluorine-18 ((18)F), for positron emission tomography (PET) in three different breast cancer models: EMT6, MCF-7 and MDA-MB-231. The PET experiments were carried out in the presence or absence of β-aminopropionitrile (BAPN), an irreversible inhibitor of LOX. Immunostaining experiments using a LOX-specific antibody on EMT-6 cells cultured under hypoxic conditions confirmed the elevation of LOX expression in these cells. An FITC-labeled oligopeptide, FITC-Ava-GGGDPKGGGGG-NH2, was found to be localized in different cellular compartments under these conditions. After injection of [(18)F]fluorobenzoate-GGGDPKGGGGG-NH2, radioactivity uptake was visible in all three breast cancer models in vivo. Tumor uptake was reduced by predosing the animals with 2 mg of BAPN 4 h or 24 h before injection of the radiotracer. The present data support further investigation into the development of LOX-binding radiolabeled peptides as molecular probes for molecular imaging of LOX expression in cancer.
    Preview · Article · Dec 2015 · Breast cancer research: BCR
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    ABSTRACT: A series of novel fluorine-containing cyclooxygenase-2 (COX-2) inhibitors was designed and synthesized based on the previously reported fluorescent COX-2 imaging agent celecoxib-NBD (3; NBD=7-nitrobenzofurazan). In vitro COX-1/COX-2 inhibitory data show that N-(4-fluorobenzyl)-4-(5-p-tolyl-3-trifluoromethylpyrazol-1-yl)benzenesulfonamide (5; IC50 =0.36 μM, SI>277) and N-fluoromethyl-4-(5-p-tolyl-3-trifluoromethylpyrazol-1-yl)benzenesulfonamide (6; IC50 =0.24 μM, SI>416) are potent and selective COX-2 inhibitors. Compound 5 was selected for radiolabeling with the short-lived positron emitter fluorine-18 ((18) F) and evaluated as a positron emission tomography (PET) imaging agent. Radiotracer [(18) F]5 was analyzed in vitro and in vivo using human colorectal cancer model HCA-7. Although radiotracer uptake into COX-2-expressing HCA-7 cells was high, no evidence for COX-2-specific binding was found. Radiotracer uptake into HCA-7 tumors in vivo was low and similar to that of muscle, used as reference tissue. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Aug 2015 · ChemMedChem
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    ABSTRACT: Radiolabeled phosphatidylserine (PS)-binding peptides represent an innovative strategy for molecular imaging of apoptosis with positron emission tomography (PET). The goal of this study was the radiopharmacological evaluation of radiolabeled peptides for their binding to PS on apoptotic cancer cells, involving metabolic stability, cellular uptake, biodistribution, and dynamic PET imaging experiments. Binding of peptides LIKKPF, PGDLSR, FBz-LIKKPF, FBz-PGDLSR, FBAM-CLIKKPF and FBAM-CPGDLSR to PS was analyzed in a newly developed radiometric binding assay using (64)Cu-labeled wild-type annexin-V as radiotracer. Radiolabeling of most potent peptides with fluorine-18 was carried out with thiol-selective prosthetic group [(18)F]FBAM to give [(18)F]FBAM-CLIKKPF and [(18)F]FBAM-CPGDLSR. [(18)F]FBAM-labeled peptides were studied in camptothecin-induced apoptotic human T lymphocyte Jurkat cells, and in a murine EL4 tumor model of apoptosis using dynamic PET imaging and biodistribution. Peptides LIKKPF and PGDLSR inhibited binding of (64)Cu-labeled annexin-V to immobilized PS in the millimolar range (IC50 10-15mM) compared to annexin-V (45nM). Introduction of FBAM prosthetic group slightly increased inhibitory potencies (FBAM-CLIKKPF: IC50=1mM; FBAM-CPGDLSR: IC50=6mM). Radiolabeling succeeded in good radiochemical yields of 50-54% using a chemoselective alkylation reaction of peptides CLIKKPF and CPGDLSR with [(18)F]FBAM. In vivo metabolic stability studies in mice revealed 40-60% of intact peptides at 5min p.i. decreasing to 25% for [(18)F]FBAM-CLIKKPF and less than 5% for [(18)F]FBAM-CPGDLSR at 15min p.i.. Cell binding of [(18)F]FBAM-CLIKKPF in drug-treated Jurkat cells was significantly higher compared to untreated cells, but this was not observed for [(18)F]FBAM-CPGDLSR. Dynamic PET imaging experiments showed that baseline uptake of [(18)F]FBAM-CLIKKPF in EL4 tumors was higher (SUV5min 0.46, SUV60min 0.13) compared to [(18)F]FBAM-CPGDLSR (SUV5min 0.16, SUV60min 0.10). Drug-treated EL4 tumors did not show an increased uptake for both [(18)F]FBAM-labeled peptides. Although both (18)F-labeled peptides [(18)F]FBAM-CLIKKPF and [(18)F]FBAM-CPGDLSR showed higher binding to apoptotic Jurkat cells in vitro, their in vivo uptake profiles were not different in apoptotic EL4 tumors. This may explained by the relatively low potency of both compounds to compete with binding of (64)Cu-labeled annexin-V to PS. Overall the novel competitive radiometric PS-binding assay with (64)Cu-labeled annexin-V represents a versatile and very robust screening platform to analyze potential PS-binding compounds in vitro. Further studies will be necessary to evaluate alternative peptide structures toward their use as PET radiotracers imaging apoptosis in vivo. Development of peptide-based radiotracers for imaging apoptosis in vivo remains a significant challenge. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Jun 2015 · Nuclear Medicine and Biology

  • No preview · Conference Paper · May 2015
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    ABSTRACT: Current translational cancer research is directed to the development of high affinity peptide ligands for targeting neuropeptide receptors overexpressed in different types of cancer. Besides their desired high binding affinity to the receptor, suitability of radiolabelled peptides as targeting vectors for molecular imaging and therapy depends on additional aspects such as high tumour-to-background ratio, favourable clearance pattern from non-target tissue, and sufficient metabolic stability in vivo. This study reports how a switch from the prosthetic group, N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB), to 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) effects the metabolic pathway of an 18F-labelled bombesin derivative, QWAV-Sar-H-FA01010-Tle-NH2. 18F-Labelled bombesin derivatives represent potent peptide ligands for selective targeting of gastrin-releasing peptide (GRP) receptor-expressing prostate cancer. Radiosynthesis of 18F-labelled bombesin analogues [18F]FBz-Ava-BBN2 and [18F]FDG-AOAc-BBN2 was achieved in good radiochemical yields of ~50% at a specific activity exceeding 40 GBq/mol. Both non-radioactive compounds FBz-Ava-BBN2 and FDG-AOAc-BBN2 inhibited binding of [125I]Tyr4-bombesin(1-14) in PC3 cells with IC50 values of 9 and 16 nM, respectively, indicating high inhibitory potency. Influence of each prosthetic group was further investigated in PC3 mouse xenografts using dynamic small animal PET imaging. In comparison to [18F]FBz-Ava-BBN2 total tumour uptake levels were doubled after injection of [18F]FDG-AOAc-BBN2 while renal elimination was increased. Blood clearance and in vivo metabolic stability were similar for both compounds. The switch from [18F]SFB to [18F]FDG as the prosthetic group led to a significant reduction in lipophilicity which resulted in more favourable renal clearance and increased tumour uptake. The presented single step radiolabelling-glycosylation approach represents an innovative strategy for site-directed peptide labelling with the short-lived positron emitter 18F while providing a favourable pharmacokinetic profile of 18F-labelled peptides.
    No preview · Article · Jan 2015 · Bioconjugate Chemistry
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    ABSTRACT: Objective The objective of the study is to demonstrate the feasibility of using [11C]-choline positron-emission tomography (PET)/CT to deliver helical tomotherapy (HT) to the prostate with a simultaneous integrated boost to dominant intraprostatic lesions as a biological target volume for dose escalation. Methods Eleven patients with intermediate-risk prostate cancer were included in this virtual planning study. Pretreatment baseline [11C]-choline PET/CT scans were acquired with a PET/CT scanner dynamically in 2-min frames from injection to 40 min post injection. PET data was reconstructed using the RAMLA 3D algorithm and analyzed to identify dominant intraprostatic lesion(s). Dominant lesions were defined as biological target volume(s) (BTV) including all voxels with a standardized uptake value of 75 % or above relative to the maximum standard uptake value (SUV) within the prostate gland. Three target volumes for optimization included the following: PTV78 (BTV + 5 mm margin), PTV68 (prostate + 5 mm posteriorly and 10 mm in all other dimensions), and PTV50 (prostate gland and proximal seminal vesicles + 7 mm margin posteriorly and 10 mm in all other dimensions). Dose constraints on organs at risk were implemented based on a published data using hypofractionated IMRT with long-term follow-up. Helical tomotherapy plans were generated to deliver hypofractionated radiation therapy to these volumes using simultaneous integrated boost in 25 fractions. Results Eight patients had one identifiable contiguous BTV, and the other three patients had two noncontiguous BTVs. The mean BTV ratio to prostate volume ratio was 6.03 % (minimum 0.80 %, maximum 13.44 %). Target volume and normal tissue constraints were met in seven of the 11 patients enrolled in the study. Targets and structures in the four patients that did not meet constraints were the bladder (3 patients), peritoneal cavity (2 patients), rectum (1 patient), PTV68 (1 patient), and PTV50 (1 patient). Conclusion It is feasible in selected patients to use [11C]-choline PET/CT to deliver hypofractionated dose-escalated helical tomotherapy to dominant intraprostatic lesions with simultaneous integrated boost using clinically established normal tissue constraints.
    No preview · Article · Dec 2014
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    ABSTRACT: Background: Epithelial ovarian cancer (EOC) is characterized by the overexpression of cancer antigen 125 (CA125), a mucinous glycoprotein that serves as a tumor biomarker. Early diagnosis of EOC is plagued by its asymptomatic nature of progression and the limitations of currently used immunoassay techniques that detect CA125 as a shed antigen in serum samples. Presently, there is no technique available for the in vivo evaluation of CA125 expression in malignant tissues. Moreover, there could be an unexplored pathophysiological time window for the detection of CA125 in EOC, during which it is expressed on tumor cells prior to being shed into the bloodstream. A method for the in vivo evaluation of CA125 expression on ovarian neoplasms earlier along disease progression and/or recurrence can potentially contribute to better disease management. To this end, the present work utilizes an anti-CA125 monoclonal antibody (MAb) and a single-chain variable fragment (scFv) labeled with the positron-emitting radionuclide (64)Cu for preclinical molecular imaging of CA125 expression in vivo. Methods: Anti-CA125 MAb and scFv were prepared and functionally characterized for target binding prior to being tested as radiotracers in a preclinical setting. Results: Immunoblotting, immunofluorescence, and flow cytometry revealed specific binding of CA125-targeting vectors to NIH:OVCAR-3 cells and no binding to antigen-negative SKOV3 cells. (64)Cu-labeled anti-CA125 MAb and scFv were obtained in specific activities of 296 and 122 MBq/mg, respectively. Both radioimmunoconjugate vectors demonstrated highly selective binding to NIH:OVCAR-3 cells and virtually no binding to SKOV3 cells. In vivo radiopharmacological evaluation using xenograft mouse models injected with (64)Cu-labeled anti-CA125 MAb provided a standardized uptake value (SUV) of 5.76 (29.70 %ID/g) in OVCAR3 tumors 24 h post-injection (p.i.) versus 1.80 (5.91 %ID/g) in SKOV3 tumors. (64)Cu-labeled anti-CA125 scFv provided an SUV of 0.64 (3.21 %ID/g) in OVCAR3 tumors 24 h p.i. versus 0.25 (1.49 %ID/g) in SKOV3 tumors. Results from small-animal PET imaging were confirmed by ex vivo autoradiography and immunohistochemistry. Conclusions: Radiolabeling of anti-CA125 MAb and scFv with (64)Cu did not compromise their immunoreactivity. Both radioimmunoconjugates presented specific tumor uptake and expected biological clearance profiles. This renders them as potential immuno-PET probes for targeted in vivo molecular imaging of CA125 in EOC.
    Preview · Article · Dec 2014 · EJNMMI Research
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    ABSTRACT: The multitargeting tyrosine kinase inhibitor (TKI) sunitinib is currently the first-line drug therapy for metastasizing renal cell carcinoma (RCC). TKIs have profound effects on tumor angiogenesis, leading to modifications of the tumor microenvironment. The goal of this study was to determine whether these treatment-induced changes can be detected with [(18)F]FAZA. The present study utilized positron emission tomography (PET) to analyze tumor oxygenation status during and after sunitinib therapy in the murine Caki-1 RCC tumor model. Dynamic and static scans were performed, as well as ex vivo biodistributions at 3 h post injection (p.i.). Immunohistochemical analysis of tumor tissue was carried out for the quantification of pimonidazole binding and the hypoxia-associated factors CD-31, Ki-67, and Von Willebrand factor (VWF). In addition, in vitro cellular uptake studies were done to analyze the direct effects of sunitinib on the Caki-1 cells. During therapy with sunitinib (40 mg/kg/day), uptake of [(18)F]FAZA into Caki-1 mice decreased by 46 ± 5% (n = 4; 5 days) at 3 h post injection (p.i.) during the first study and 22 ± 5% (n = 8; 9 days) during the long-term study, indicating a decrease in the tumor's hypoxia level. However, when drug therapy was stopped, this effect was reversed completely, and the tumor [(18)F]FAZA uptake increased to 126 ± 6% (n = 6) of the control tumor uptake, indicative of an even higher level of tumor hypoxia compared to the therapy starting point. Sunitinib had no direct effect on [(18)F]FAZA uptake into Caki-1 cells in vitro. [(18)F]FAZA PET could be used to monitor drug response during sunitinib therapy in RCC and may guide combination therapies based on the tumor's hypoxia status.
    Full-text · Article · Dec 2014 · EJNMMI Research
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    ABSTRACT: Introduction 18 F-labeled amino acids are important PET radiotracers for molecular imaging of cancer. This study describes synthesis and radiopharmacological evaluation of 2-amino-5-(4-[18 F]fluorophenyl)pent-4-ynoic acid ([18 F]FPhPA) as a novel amino acid radiotracer for oncologic imaging. Methods 18 F]FPhPA was prepared using Pd-mediated Sonogashira cross-coupling reaction between 4-[18 F]fluoroiodobenzene ([18 F]FIB) and propargylglycine. The radiopharmacological profile of [18 F]FPhPA was evaluated in comparison with O-(2-[18 F]fluoroethyl)-L-tyrosine ([18 F]FET) using the murine breast cancer cell line EMT6 involving cellular uptake studies, radiotracer uptake competitive inhibition experiments and small animal PET imaging. Results 18 F]FPhPA was prepared in 42 ± 10% decay-corrected radiochemical yield with high radiochemical purity > 95% after semi-preparative HPLC purification. Cellular uptake of L-[18 F]FPhPA reached a maximum of 58 ± 14 % radioactivity/mg protein at 90 min. Lower uptake was observed for racemic and D-[18 F]FPhPA Radiotracer uptake inhibition studies by synthetic and naturally occurring amino acids suggested that Na+-dependent system ASC, especially ASCT2, and Na+-independent system L are important amino acid transporters for [18 F]FPhPA uptake into EMT6 cells. Small animal PET studies demonstrated similar high tumor uptake of [18 F]FPhPA in EMT6 tumor-bearing mice compared to [18 F]FET reaching a maximum standardized uptake value (SUV) of 1.35 after 60 min p.i.. Muscle uptake of [18 F]FPhPA was higher (SUV30min = 0.65) compared to [18 F]FET (SUV30min = 0.40), whereas [18 F]FPhPA showed a more rapid uptake and clearance from the brain compared to [18 F]FET. Conclusion L-[18 F]FPhPA is the first 18 F-labeled amino acid prepared through Pd-mediated cross-coupling reaction. Advances in Knowledge and Implications for patient Care L-[18 F]FPhPA displayed promising properties as a novel amino acid radiotracer for molecular imaging of system ASC and system L amino acid transporters in cancer.
    No preview · Article · Sep 2014 · Nuclear Medicine and Biology

  • No preview · Conference Paper · Aug 2014

  • No preview · Article · Aug 2014 · Nuclear Medicine and Biology
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    ABSTRACT: The radiosynthesis and radiopharmacological evaluation including small animal PET imaging of a novel 64Cu-labelled cryptand molecule ([64Cu]CryptTM) possessing a tris-pyridyl/tris-amido set of donor atoms is described.
    Full-text · Article · May 2014 · Medicinal Chemistry Communication
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    ABSTRACT: 6-Deoxy-6-[(18)F]fluoro-D-fructose (6-[(18)F]FDF) is a promising PET radiotracer for imaging GLUT5 in breast cancer. The present work describes GMP synthesis of 6-[(18)F]FDF in an automated synthesis unit (ASU) and dosimetry calculations to determine radiation doses in humans. GMP synthesis and dosimetry calculations are important prerequisites for first-in-human clinical studies of 6-[(18)F]FDF. The radiochemical synthesis of 6-[(18)F]FDF was optimized and adapted to an automated synthesis process using a Tracerlab FXFN ASU (GE Healthcare). Starting from 30 GBq of cyclotron-produced n.c.a. [(18)F]fluoride, 2.9 ± 0.1 GBq of 6-[(18)F]FDF could be prepared within 50 min including HPLC purification resulting in an overall decay-corrected radiochemical yield of 14 ± 3% (n = 11). Radiochemical purity exceeded 95%, and the specific activity was greater than 5.1 GBq/μmol. Sprague-Dawley rats were used for biodistribution experiments, and dynamic and static small animal PET experiments. Biodistribution studies served as basis for allometric extrapolation to the standard man anatomic model and normal organ-absorbed dose calculations using OLINDA/EXM software. The calculated human effective dose for 6-[(18)F]FDF was 0.0089 mSv/MBq. Highest organ doses with a dose equivalent of 0.0315 mSv/MBq in a humans were found in bone. Injection of 370 MBq (10 mCi) of 6-[(18)F]FDF results in an effective whole body radiation dose of 3.3 mSv in humans, a value comparable to that of other (18)F-labeled PET radiopharmaceuticals. The optimized automated synthesis under GMP conditions, the good radiochemical yield and the favorable human radiation dosimetry estimates support application of 6-[(18)F]FDF in clinical trials for molecular imaging of GLUT5 in breast cancer patients.
    No preview · Article · May 2014 · American Journal of Nuclear Medicine and Molecular Imaging
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    ABSTRACT: Cyclooxygenase (COX) is the key enzyme within the complex conversion of arachidonic acid into prostaglandins (PGs). Inhibitors of this enzyme represent a particularly promising class of compounds for chemoprevention and cancer therapy. The experimental data on the involvement of COX isoform COX-2 in tumour development and progression, as well as the observed overexpression of COX-2 in a variety of human cancers provide the rationale for targeting COX-2 for molecular imaging and therapy of cancer. A series of trifluoromethyl-substituted pyrimidines was prepared as a novel class of selective COX-2 inhibitors, based on the lead structure . All compounds were tested in cyclooxygenase (COX) assays in vitro to determine COX-1 and COX-2 inhibitory potency and selectivity. Molecular docking studies using the catalytic site of COX-1 and COX-2, respectively, provided complementary theoretical support for the obtained experimental biological structure-activity relationship data of three highly potent and selective fluorobenzyl-containing COX-2 inhibitors. Selected fluorobenzyl-substituted pyrimidine derivatives were further developed as (18)F-labelled radiotracers ([18F]1a, [18F]2a, [18F]3a). Radiotracers [18F]1a and [18F]2a were radiolabelled using 4-[18F]fluorobenzylamine ([18F]FBA) as a building block. Radiotracer [18F]3a was radiofluorinated directly using a nucleophilic aromatic substitution reaction with no-carrier-added (n.c.a.) [18F]fluoride on an iodylaryl compound as a labelling precursor.
    Full-text · Article · Oct 2013 · Organic & Biomolecular Chemistry
  • Ole Tietz · Alison Marshall · Melinda Wuest · Monica Wang · Frank Wuest
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    ABSTRACT: Cyclooxygenase (COX) enzyme is responsible for the formation of important biological mediators including prostaglandins, prostacyclin and thromboxane to trigger many physiological and patho-physiological responses. COXs exist in two distinct isoforms, a constitutively expressed form (COX-1) and an inducible form (COX-2). COX-2 is involved in the body's response to inflammation and pain. Moreover, it has also been shown that COX-2 is overexpressed in many human cancers, and that COX-2 is involved in various neurodegenerative diseases such as Parkinson's and Alzheimer's disease. COX-2 inhibitors are among the most widely used therapeutics for the treatment of chronic and acute pain and inflammation. Non-invasive monitoring of COX-2 functional expression by means of nuclear molecular imaging techniques like positron emission tomography (PET) and single photon emission computed tomography (SPECT) might provide unique opportunities to obtain data on COX-2 expression levels during disease manifestation and progression to study potential roles of COX-2 under various pathological conditions. The present review summarizes recent research efforts directed to the design and synthesis of radiotracers as molecular probes with special emphasis on COX-2 imaging.
    No preview · Article · Sep 2013 · Current Medicinal Chemistry
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    ABSTRACT: Introduction: Bombesin (BBN) and BBN analogues have attracted much attention as high-affinity ligands for selective targeting of the gastrin-releasing peptide (GRP) receptor. GRP receptors are overexpressed in a variety of human cancers including prostate cancer. Radiolabeled BBN derivatives are promising diagnostic probes for molecular imaging of GRP receptor-expressing prostate cancer. This study describes the synthesis and radiopharmacological evaluation of various metabolically stabilized fluorobenzoylated bombesin analogues (BBN-1, BBN-2, BBN-3). Methods: Three fluorobenzoylated BBN analogues containing an aminovaleric (BBN-1, BBN-2), or an aminooctanoic acid linker (BBN-3) were tested in a competitive binding assay against (125)I-[Tyr(4)]-BBN for their binding potency to the GRP receptor. Intracellular calcium release in human prostate cancer cells (PC3) was measured to determine agonistic or antagonistic profiles of fluorobenzoylated BBN derivatives. Bombesin derivative BBN-2 displayed the highest inhibitory potency toward GRP receptor (IC50 = 8.7 ± 2.2 nM) and was subsequently selected for radiolabeling with fluorine-18 ((18)F) through acylation with N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). The radiopharmacological profile of (18)F-labeled bombesin [(18)F]BBN-2 was evaluated in PC3 tumor-bearing NMRI nude mice involving metabolic stability studies, biodistribution experiments and dynamic small-animal PET studies. Results: All fluorobenzoylated BBN derivatives displayed high inhibitory potency toward the GRP receptor (IC50=8.7-16.7 nM), and all compounds exhibited antagonistic profiles as determined in an intracellular calcium release assay. The (18)F-labeled BBN analogue [(18)F]BBN-2 was obtained in 30% decay-corrected radiochemical yield with high radiochemical purity >95% after semi-preparative HPLC purification. [(18)F]BBN-2 showed high metabolic stability in vivo with 65% of the radiolabeled peptide remaining intact after 60 min p.i. in mouse plasma. Biodistribution experiments and dynamic small-animal PET studies demonstrated high tumor uptake of [(18)F]BBN-2 in PC3 xenografts (2.75 ± 1.82 %ID/g after 5 min and 2.45 ± 1.25 %ID/g after 60 min p.i.). Specificity of radiotracer uptake in PC3 tumors was confirmed by blocking experiments. Conclusion: The present study demonstrates that (18)F-labeled BBN analogue [(18)F]BBN-2 is a suitable PET radiotracer with favorable metabolic stability in vivo for molecular imaging of GRP receptor-positive prostate cancer.
    Full-text · Article · Aug 2013 · Nuclear Medicine and Biology
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    ABSTRACT: The radiometal (64)Cu is now widely used in the development of diagnostic imaging agents for positron emission tomography (PET). The present study has led to the development and evaluation of a novel chelating agent for (64)Cu: the new monothiourea tripodal ligand 1-benzoyl-3-{6-[(bis-pyridin-2-ylmethyl-amino)-methyl]-pyridin-2-yl}-thiourea (MTUBo). X-ray crystallographic analysis has shown this ligand forms a mononuclear complex with copper(ii) and co-ordinates via a trigonal bipyramidal N4S array of donor atoms. Promisingly, cell uptake studies revealed that (64)Cu-MTUBo selectively accumulates in EMT-6 cells incubated under hypoxic conditions which may result from its relatively high Cu(II/I) redox potential. Small-animal PET imaging and ex vivo biodistribution studies in EMT-6 tumor bearing BALB/c mice revealed significant tumor uptake after 1 h p.i., yielding tumor-to-muscle (T/M) and tumor-to-blood (T/B) ratios of 8.1 and 1.1, respectively. However, injection of (64)Cu-acetate resulted in similar uptake indicating that the observed uptake was most likely non-specific. Despite showing high in vitro stability, it is likely that in vivo the complex undergoes transchelation to proteins within the blood in a relatively short timeframe. For comparison, the hypoxia imaging agent (64)Cu-ATSM was also evaluated in the same murine tumor model and showed about 60% higher tumor uptake than (64)Cu-MTUBo.
    Full-text · Article · Jul 2013 · Dalton Transactions
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    ABSTRACT: To elucidate the impact of the mucosa on detrusor muscle function by investigating force of contraction under various stimulatory conditions and during subsequent relaxation using catecholamines. Detrusor tissue was obtained from patients who had undergone cystectomy for bladder cancer and strips of intact or mucosa-denuded muscle were set up for force measurement. Preparations were precontracted with KCl, carbachol or electric-field stimulation (EFS). Precontracted strips were relaxed using increasing concentrations of catecholamines in the absence and presence of the subtype-selective β-adrenoceptor (AR) blockers CGP 20712A (β1-ARs), ICI 118,551 (β2-ARs), and L-748,337 (β3-ARs). Force development in response to KCl (40 mM), carbachol (1 μM) or EFS was larger in the absence of mucosa than in intact muscle strips. The force of contraction of mucosa-denuded strips with detached urothelium incubated in the same chamber was as low as in intact strips. Noradrenaline relaxed precontracted detrusor strips to a significantly larger extent and at lower concentrations in denuded than in intact strips. CGP 20712A did not affect noradrenaline-induced relaxation of denuded and intact strips, and ICI 118,551 did not influence noradrenaline-induced relaxation in denuded strips, but abolished the difference between denuded and intact strips. The antagonism of the relaxant effects of noradrenaline by L-748,337 was slightly smaller in intact than denuded strips. The mucosa of human detrusor strips impairs force development when stimulated with KCl, carbachol or EFS. The mucosa also blunts the relaxing effects of catecholamines. The latter effect does not involve the activation of β1-ARs but only of β2-ARs, whereas β3-ARs mediate the relaxation of human detrusor.
    No preview · Article · Jun 2013 · BJU International
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    ABSTRACT: The copper-free click chemistry reaction between norbornene and tetrazine species is known to proceed in a rapid, reliable and selective manner under mild conditions. Due to these attractive properties, this reaction has recently been explored as a generally applicable method of bioconjugation. Here, we report a convenient synthetic procedure towards a novel (18)F-labelled norbornene derivative () and have evaluated its ability to undergo strain-promoted copper-free click chemistry reactions with two model tetrazine species: an asymmetric dipyridyl tetrazine derivative (Tz) and a tetrazine thiourea-coupled stabilised bombesin peptide (TT-BBN). In both cases, was found to undergo rapid and high-yielding click chemistry reactions. Furthermore, as reactions of this type could also potentially be used in vivo to facilitate the development of a novel pretargeting approach for tumour imaging and therapy, we have also assessed the radiopharmacological profile (bioavailability, biodistribution, blood clearance and metabolic stability) of in normal BALB/c mice. This radiolabelled compound exhibits both high bioavailability and metabolic stability with approximately 90% remaining intact up to 30 min following administration.
    Full-text · Article · May 2013 · Organic & Biomolecular Chemistry

Publication Stats

500 Citations
183.10 Total Impact Points


  • 2012-2015
    • Cross Cancer Institute
      • Department of Medical Oncology
      Edmonton, Alberta, Canada
  • 2010-2015
    • University of Alberta
      • Department of Oncology
      Edmonton, Alberta, Canada
  • 1998-2013
    • Technische Universität Dresden
      • • Institute of Pharmacology and Toxicology
      • • Anorganische Chemie
      Dresden, Saxony, Germany
  • 2005-2006
    • Institut für Pharmakologie und Toxikologie der Bundeswehr
      München, Bavaria, Germany
  • 2002
    • University of Leipzig
      • Institute of Pharmacy
      Leipzig, Saxony, Germany