SSTR2-based Reporters for Assessing Gene Transfer into Non-Small Cell Lung Cancer: Evaluation using an Intrathoracic Mouse Model.

Hum Gene Ther. 2010 Jul 23;

Authors: Singh SP, Han L, Ravoori MK, Solis LM, Roth JA, Ji L, Wistuba II, Kundra V

Purpose: The most common cause of cancer-related deaths in North America is lung cancer, of which, 85% is due to non-small cell (NSCLC). Gene therapy is a promising approach, but has been hindered by lack of methods for localizing and quantifying gene expression in vivo. Human somatostatin receptor subtype-2 (SSTR2)-based reporters can be used to follow gene expression in vivo using ligands with greater affinity for this subtype. NSCLC's can express somatostatin receptor subtypes, which may interfere with SSTR2-based reporters. We assessed whether a SSTR2-based reporter can serve as reporter of gene transfer into NSCLC's. Material and Methods: SSTR subtype expression was assessed in NSCLC cell lines A549, H460, and H1299 using RT-PCR. After infection with an adenovirus containing hemagglutinin-A-tagged-SSTR2 (Ad-HA-SSTR2) or control insert, expression was assessed by immunologic techniques and binding to clinically-approved 111In-octreotide. In vivo, after MR imaging, intrathoracic H460 tumors were injected with Ad-HA-SSTR2 or control virus (n=6 mice/group) under ultrasound guidance. Intravenous injection of 111In-octreotide two days later was followed by planar and SPECT imaging. Biodistribution into tumors was assessed in vivo using anatomic MR and functional gamma-camera images and ex vivo using excised organs/tumors. In human lung tumor samples (n=70), SSTR2 expression was assessed using immunohistochemistry. Results: All three NSCLC cell lines expressed different SSTR subtypes, but none expressed SSTR2. Upon Ad-HA-SSTR2 infection, HA-SSTR2 expression was seen in all three cell lines using antibodies targeting the HA domain or 111In-octreotide targeting the receptor domain (P<.05). Intrathoracic tumors infected with Ad-HA-SSTR2 were clearly visible by gamma camera imaging; expression was quantified by both in vivo and ex vivo biodistribution analysis and demonstrated greater uptake in tumors infected with Ad-HA-SSTR2 compared to control virus (P<.05). Immunohistochemistry found that 78% of NSCLC's are negative for and 13% have low levels of SSTR subtype 2 expression. Conclusion: SSTR2-based reporters can serve as reporters of gene transfer into non-small cell lung cancers.

PMID: 20653396 [PubMed - as supplied by publisher]

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In vivo chemistry for pretargeted tumor imaging in live mice.

Angew Chem Int Ed Engl. 2010 Apr 26;49(19):3375-8

Authors: Rossin R, Verkerk PR, van den Bosch SM, Vulders RC, Verel I, Lub J, Robillard MS

PMID: 20391522 [PubMed - indexed for MEDLINE]

PET imaging of fatty acid amide hydrolase in the brain: synthesis and biological evaluation of an (11)C-labelled URB597 analogue.

Nucl Med Biol. 2010 Jul;37(5):665-675

Authors: Wyffels L, Muccioli GG, Kapanda CN, Labar G, De Bruyne S, De Vos F, Lambert DM

INTRODUCTION: Fatty acid amide hydrolase (FAAH) is part of the endocannabinoid system (ECS) and has been linked to the aetiology of several neurological and neuropsychiatric disorders. So far no useful PET or SPECT tracer for in vivo visualisation of FAAH has been reported. We synthesized and evaluated a carbon-11-labeled URB597 analogue, biphenyl-3-yl [(11)C]-4-methoxyphenylcarbamate or [(11)C]-1, as potential FAAH imaging agent. METHODS: The inhibitory activity of 1 was determined in vitro using recombinant FAAH. Radiosynthesis of [(11)C]-1 was performed by methylation using [(11)C]-CH(3)I, followed by HPLC purification. Biological evaluation was done by biodistribution studies in wild-type and FAAH knock-out mice, and by ex vivo and in vivo metabolite analysis. The influence of URB597 pretreatment on the metabolisation profile was assessed. RESULTS: [(11)C]-1 was obtained in good yields and high radiochemical purity. Biodistribution studies revealed high brain uptake in wild-type and FAAH knock-out mice, but no retention of radioactivity could be demonstrated. Metabolite analysis and URB597 pretreatment confirmed the non-FAAH-mediated metabolisation of [(11)C]-1. The inhibition mechanism was determined to be reversible. In addition, the inhibition of URB597 appeared slowly reversible. CONCLUSIONS: Although [(11)C]-1 inhibits FAAH in vitro and displays high brain uptake, the inhibition mechanism seems to deviate from the proposed carbamylation mechanism. Consequently, it does not covalently bind to FAAH and will not be useful for mapping the enzyme in vivo. However, it represents a potential starting point for the development of in vivo FAAH imaging tools.

PMID: 20610171 [PubMed - as supplied by publisher]

Pre-clinical evaluation of a 3-nitro-1,2,4-triazole analogue of [(18)F]FMISO as hypoxia-selective tracer for PET.

Nucl Med Biol. 2010 Jul;37(5):565-575

Authors: Bejot R, Kersemans V, Kelly C, Carroll L, King RC, Gouverneur V

Hypoxia in solid tumours is associated with the promotion of various metabolic mechanisms and induces resistance to radio- and chemotherapy. Non-invasive positron emission tomography (PET) or single photon emission computed tomography by use of selective biomarkers has emerged as valuable tools for the detection of hypoxic areas within tumours so treatment can be modified accordingly. The aim of this investigation was to evaluate [(18)F]3-NTR, a 3-nitro-1,2,4-triazole analogue (N(1) substituted) of [(18)F]FMISO as a potential hypoxia selective tracer. 3-NTR and its (18)F-radiolabelled isotopic isomer were synthesised and compared with FMISO in vitro and in vivo. Their physicochemical properties were measured, the enzymatic reduction was evaluated, and the reactivity of their metabolites was investigated. Biodistribution and PET scans were performed on CBA mice bearing hypoxic CaNT tumour cells, using (18)F-labelled versions of the tracers. [(18)F]3-NTR uptake within hypoxic cells was lower than [(18)F]FMISO and [(18)F]3-NTR did not exhibit any better selectivity than FMISO as a PET tracer in vivo. Both (18)F-radiolabelled compounds are relatively evenly distributed within the whole body and the radioactive uptake within hypoxic tumours reaches a maximum at 30 min post injection and decreases thereafter. Xanthine oxidase exhibited a nitroreductase activity toward 3-NTR under anaerobic conditions, but reduced metabolites did not bind covalently. It is confirmed that 3-NTR is an electron acceptor. It is postulated that radiolabelled metabolites and fragments of [(18)F]3-NTR are freely diffusing due to their poor binding capacities. Thus [(18)F]3-NTR cannot be used as a hypoxia selective tracer for PET. The investigation provides insights into the importance of the propensity to form covalent adducts for such biomarkers.

PMID: 20610161 [PubMed - as supplied by publisher]

Kit formulation for (99m)Tc-labeling of recombinant anti-HER2 Affibody molecules with a C-terminally engineered cysteine.

Nucl Med Biol. 2010 Jul;37(5):539-546

Authors: Ahlgren S, Andersson K, Tolmachev V

INTRODUCTION: Molecular imaging of human epidermal growth factor receptor type 2 (HER2)-expression in malignant tumors provides potentially important information for patient management. Affibody molecules have shown to be suitable tracers for imaging applications using single photon emission computed tomography or positron emission tomography. Results from an earlier evaluation of the application of site-specific (99m)Tc-labeling of the Affibody molecule, Z(HER2:2395)-C, were favorable. METHODS: As a preparation for clinical application of this tracer, we have developed and evaluated a robust single-vial freeze-dried kit, allowing labeling of the Affibody molecule, Z(HER2:2395)-C, with (99m)Tc. RESULTS: The composition of the kit [containing glucoheptonate, EDTA and tin(II)-chloride], as well as the protein amount and the pertechnetate volume were optimized for a high labeling yield (>90%) and minimal presence of reduced hydrolyzed technetium colloids (<1%). The specificity to HER2 receptors, the binding competence and the stability in phosphate-buffered saline and murine serum were verified in vitro. The shelf-life was also evaluated in vitro, showing no reduction in labeling yield or binding capacity to HER2-expressing cells after over 400 days of storage of the single-vial freeze-dried kit. CONCLUSIONS: Z(HER2:2395)-C labeled with (99m)Tc using the lyophilized kit was stable and resulted in a favorable biodistribution in an in vivo evaluation in normal Naval Medical Research Institute mice.

PMID: 20610158 [PubMed - as supplied by publisher]

Radiolabeled 5-iodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine and its 5'-monophosphate for imaging and therapy of androgen receptor-positive cancers: synthesis and biological evaluation.

J Med Chem. 2009 Aug 27;52(16):5124-43

Authors: Kortylewicz ZP, Nearman J, Baranowska-Kortylewicz J

High levels of androgen receptor (AR) are often indicative of recurrent, advanced, or metastatic cancers. These conditions are also characterized by a high proliferative fraction. 5-Radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine 8 and 5-radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridin-5'-yl monophosphate 13 target AR. They are also degraded intracellularly to 5-radioiodo-2'-deoxyuridine 1 and its monophosphate 20, respectively, which can participate in the DNA synthesis. Both drugs were prepared at the no-carrier-added level. Precursors and methods are readily adaptable to radiolabeling with various radiohalides suitable for SPECT and PET imaging, as well as endoradiotherapy. In vitro and in vivo studies confirm the AR-dependent interactions. Both drugs bind to sex hormone binding globulin. This binding significantly improves their stability in serum. Biodistribution and imaging studies show preferential uptake and retention of 8 and 13 in ip xenografts of human ovarian adenocarcinoma cells NIH:OVCAR-3, which overexpress AR. When these drugs are administered at therapeutic dose levels, a significant tumor growth arrest is observed.

PMID: 19653647 [PubMed - indexed for MEDLINE]

In Vitro Analysis and In Vivo Tumor Targeting of a Humanized, Grafted Nanobody in Mice Using Pinhole SPECT/Micro-CT.

J Nucl Med. 2010 Jun 16;

Authors: Vaneycken I, Govaert J, Vincke C, Caveliers V, Lahoutte T, De Baetselier P, Raes G, Bossuyt A, Muyldermans S, Devoogdt N

Nanobodies are a novel type of immunoglobulinlike, antigen-binding protein with beneficial pharmacologic and pharmacokinetic properties that are ideally suited to targeting cellular antigens for molecular imaging or therapeutic purposes. However, because of their camelid, nonhuman origin, the possible immunogenicity of Nanobodies when used in the clinic is a concern. Here we present a new strategy to quickly generate humanized Nanobodies for molecular imaging purposes. METHODS: We genetically grafted the antigen-binding loops of NbCEA5, a Nanobody with specificity for the colon carcinoma marker carcinoembryonic antigen (CEA), onto the framework of a humanized Nanobody scaffold. This scaffold has been previously characterized in our laboratory as a stable Nanobody that can serve as a universal loop acceptor for antigen-binding loops from donor Nanobodies and has been additionally mutated at about 10 crucial surface-exposed sites to resemble the sequence of human variable immunoglobulin domains. The 3 recombinant Nanobodies (NbCEA5, humanized scaffold, and humanized CEA5 graft) were produced in bacteria and purified. Unlabeled and (99m)Tc-labeled Nanobodies were biochemically characterized in vitro and tested as probes for SPECT/CT of xenografted tumors. RESULTS: The success of loop-grafting was confirmed by comparing these Nanobodies for their capacity to recognize soluble CEA protein in enzyme-linked immunosorbent assay and by surface plasmon resonance and to bind to CEA-positive LS174T colon carcinoma cells and CEA-transfected but not untransfected Chinese hamster ovary cells in flow cytometry. Specificity of binding was confirmed by competition studies. All Nanobodies were heat-stable, could be efficiently labeled with (99m)Tc, and recognized both soluble and membrane-bound CEA protein in binding studies. Finally, biodistribution experiments were performed with intravenously injected (99m)Tc-labeled Nanobodies in LS174T tumor-bearing mice using pinhole SPECT/micro-CT. These in vivo experiments revealed specificity of tumor targeting and rapid renal clearance for all Nanobodies, with low signals in all organs besides the kidneys. CONCLUSION: This study shows the potency of antigen-binding loop-grafting to efficiently generate humanized Nanobodies that retain their targeting capacities for noninvasive in vivo imaging of tumors.

PMID: 20554727 [PubMed - as supplied by publisher]

Molecular Imaging of Matrix Metalloproteinase Activation to Predict Murine Aneurysm Expansion In Vivo.

J Nucl Med. 2010 Jun 16;

Authors: Razavian M, Zhang J, Nie L, Tavakoli S, Razavian N, Dobrucki LW, Sinusas AJ, Edwards DS, Azure M, Sadeghi MM

Rupture and dissection are major causes of morbidity and mortality in arterial aneurysm and occur more frequently in rapidly expanding aneurysms. Current imaging modalities provide little information on aneurysm beyond size. Matrix metalloproteinase (MMP) activation plays a key role in the pathogenesis of aneurysm. We investigated whether imaging MMP activation in aneurysm helps predict its propensity to expansion. METHODS: We used a model of carotid aneurysm in apolipoprotein E-deficient (apoE(-/-)) mice. Radiotracers with specificity for activated MMPs were used to detect and quantify MMP activation by micro-SPECT/CT in vivo. Tracer uptake was confirmed by autoradiography and gamma-well counting, and specificity was demonstrated using an excess of unlabeled precursor and a specific MMP inhibitor. RESULTS: We demonstrated that several MMPs are expressed with distinct temporal patterns in aneurysm. Significant focal uptake was observed in aneurysmal carotid arteries, peaking at 4 wk after aneurysm induction. In a group of animals imaged serially at 2 and 4 wk after aneurysm induction, MMP tracer uptake at 2 wk correlated well with the vessel area assessed by histology at 4 wk. CONCLUSION: Molecular imaging of MMP activation is a useful experimental, and potentially clinical, tool to noninvasively predict the propensity of an aneurysm to expansion in vivo.

PMID: 20554725 [PubMed - as supplied by publisher]

Measurement of porto-systemic shunting in mice by novel three-dimensional micro-single photon emission computed tomography imaging enabling longitudinal follow-up.

Liver Int. 2010 May 23;

Authors: Van Steenkiste C, Staelens S, Deleye S, De Vos F, Vandenberghe S, Geerts A, Van De Wiele C, De Vos M, Van Vlierberghe H, Colle I

Abstract Background and aims: The reference method for diagnosing porto-systemic shunting (PSS) in experimental portal hypertension involves measuring (51)Chrome ((51)Cr)-labelled microspheres. Unfortunately, this technique necessitates the sacrifice of animals. Alternatively, (99m)technetium-macroaggregated albumin ((99m)Tc-MAA) has been used; however, planar scintigraphy imaging techniques are not quantitatively accurate and adequate spatial information is not attained. Here, we describe a reliable, minimally invasive and rapid in vivo imaging technique, using three-dimensional single photon emission computed tomography (3D SPECT) modus, that allows more accurate quantification, serial measurements and spatial discrimination. Methodology: Partial portal vein ligation, common bile duct ligation and sham were induced in male mice. A mixture of (51)Cr microspheres and (99m)Tc-macroaggregated albumin particles was injected into the splenic pulpa. All mice were scanned in vivo with muSPECT (1 mm spatial resolution) and, when mandatory for localisation, a muSPECT-CT was acquired. A relative quantitative analysis was performed based on the 3D reconstructed datasets. Additionally, (51)Cr was measured in the same animals to calculate the correlation coefficient between the (99m)Tc detection and the gold standard (51)Cr. In each measuring modality, the PSS fraction was calculated using the formula: [(lung counts)/(lung counts+liver counts)] x 100. Results: A significant correlation between the (99m)Tc detection and (51)Cr was demonstrated in partial portal vein ligation, common bile duct ligation and sham mice and there was a good agreement between the two modalities. muSPECT scanning delivers high spatial resolution and 3D image reconstructions. Conclusion: We have demonstrated that quantitative high-resolution muSPECT imaging with (99m)Tc-MAA is useful for detecting the extent of PSS in a non-sacrificing set-up. This technology permits serial measurements and high-throughput screening to detect baseline PSS, which is especially important in pharmacological studies.

PMID: 20497314 [PubMed - as supplied by publisher]

Tetraamine-derived bifunctional chelators for technetium-99m labelling: synthesis, bioconjugation and evaluation as targeted SPECT imaging probes for GRP-receptor-positive tumours.

Chemistry. 2010 Feb 15;16(7):2115-24

Authors: Abiraj K, Mansi R, Tamma ML, Forrer F, Cescato R, Reubi JC, Akyel KG, Maecke HR

Owing to its optimal nuclear properties, ready availability, low cost and favourable dosimetry, (99m)Tc continues to be the ideal radioisotope for medical-imaging applications. Bifunctional chelators based on a tetraamine framework exhibit facile complexation with Tc(V)O(2) to form monocationic species with high in vivo stability and significant hydrophilicity, which leads to favourable pharmacokinetics. The synthesis of a series of 1,4,8,11-tetraazaundecane derivatives (01-06) containing different functional groups at the 6-position for the conjugation of biomolecules and subsequent labelling with (99m)Tc is described herein. The chelator 01 was used as a starting material for the facile synthesis of chelators functionalised with OH (02), N(3) (04) and O-succinyl ester (05) groups. A straightforward and easy synthesis of carboxyl-functionalised tetraamine-based chelator 06 was achieved by using inexpensive and commercially available starting materials. Conjugation of 06 to a potent bombesin-antagonist peptide and subsequent labelling with (99m)Tc afforded the radiotracer (99m)Tc-N4-BB-ANT, with radiolabelling yields of >97% at a specific activity of 37 GBq micromol(-1). An IC(50) value of (3.7+/-1.3) nM was obtained, which confirmed the high affinity of the conjugate to the gastrin-releasing-peptide receptor (GRPr). Immunofluorescence and calcium mobilisation assays confirmed the strong antagonist properties of the conjugate. In vivo pharmacokinetic studies of (99m)Tc-N4-BB-ANT showed high and specific uptake in PC3 xenografts and in other GRPr-positive organs. The tumour uptake was (22.5+/-2.6)% injected activity per gram (% IA g(-1)) at 1 h post injection (p.i.). and increased to (29.9+/-4.0)% IA g(-1) at 4 h p.i. The SPECT/computed tomography (CT) images showed high tumour uptake, clear background and negligible radioactivity in the abdomen. The promising preclinical results of (99m)Tc-N4-BB-ANT warrant its potential candidature for clinical translation.

PMID: 20066690 [PubMed - indexed for MEDLINE]

C-kit-targeted imaging of gastrointestinal stromal tumor using radiolabeled anti-c-kit monoclonal antibody in a mouse tumor model.

Nucl Med Biol. 2010 Feb;37(2):179-87

Authors: Sogawa C, Tsuji AB, Sudo H, Sugyo A, Yoshida C, Odaka K, Uehara T, Arano Y, Koizumi M, Saga T

INTRODUCTION: Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor arising from the gastrointestinal tract and highly expresses mutated c-kit. We aimed to develop a specific and sensitive method for detecting GISTs using radiolabeled anti-c-kit monoclonal antibody. METHODS: A mutated c-kit-expressing cell clone was established by transfecting an expressing vector of mutated c-kit gene into HEK293 human embryonic kidney cells. The tumors were developed by inoculating c-kit-expressing cells into nude mice. (125)I- and (111)In-labeled anti-c-kit antibodies (12A8 and 41A11) were evaluated in vitro by cell binding, competitive inhibition and cellular internalization assays, and in vivo by biodistribution and imaging studies in tumor-bearing mice. RESULTS: Both (125)I- and (111)In-labeled antibodies showed specific binding with c-kit-expressing cells with high affinity (dissociation constants = 2.2-7.1x10(9) M(-1)). Internalization assay showed that (125)I-labeled antibodies were rapidly internalized and dehalogenated, with the release of (125)I from the cells, resulting in reduction of cell-associated radioactivity with time. In contrast, (111)In-labeled antibody was internalized but did not result in the reduced radioactivity associated with tumor cells. Reflecting this phenomenon, the in vivo tumor uptake of (125)I-labeled antibody was low on Day 1, further decreasing with time, while tumor uptake of (111)In-labeled antibody was high on Day 1, further increasing with time. The xenografted tumor was clearly visualized by scintigraphy after injection of (111)In-labeled antibody. CONCLUSION: The anti-c-kit monoclonal antibody labeled with a metal radionuclide would be promising for c-kit-targeted imaging of GISTs.

PMID: 20152717 [PubMed - indexed for MEDLINE]

Filled and glycosylated carbon nanotubes for in vivo radioemitter localization and imaging.

Nat Mater. 2010 May 16;

Authors: Hong SY, Tobias G, Al-Jamal KT, Ballesteros B, Ali-Boucetta H, Lozano-Perez S, Nellist PD, Sim RB, Finucane C, Mather SJ, Green ML, Kostarelos K, Davis BG

Functionalization of nanomaterials for precise biomedical function is an emerging trend in nanotechnology. Carbon nanotubes are attractive as multifunctional carrier systems because payload can be encapsulated in internal space whilst outer surfaces can be chemically modified. Yet, despite potential as drug delivery systems and radiotracers, such filled-and-functionalized carbon nanotubes have not been previously investigated in vivo. Here we report covalent functionalization of radionuclide-filled single-walled carbon nanotubes and their use as radioprobes. Metal halides, including Na(125)I, were sealed inside single-walled carbon nanotubes to create high-density radioemitting crystals and then surfaces of these filled-sealed nanotubes were covalently modified with biantennary carbohydrates, improving dispersibility and biocompatibility. Intravenous administration of Na(125)I-filled glyco-single-walled carbon nanotubes in mice was tracked in vivo using single-photon emission computed tomography. Specific tissue accumulation (here lung) coupled with high in vivo stability prevented leakage of radionuclide to high-affinity organs (thyroid/stomach) or excretion, and resulted in ultrasensitive imaging and delivery of unprecedented radiodose density. Nanoencapsulation of iodide within single-walled carbon nanotubes enabled its biodistribution to be completely redirected from tissue with innate affinity (thyroid) to lung. Surface functionalization of (125)I-filled single-walled carbon nanotubes offers versatility towards modulation of biodistribution of these radioemitting crystals in a manner determined by the capsule that delivers them. We envisage that organ-specific therapeutics and diagnostics can be developed on the basis of the nanocapsule model described here.

PMID: 20473287 [PubMed - as supplied by publisher]

Nanobodies as tools for in vivo imaging of specific immune cell types.

J Nucl Med. 2010 May;51(5):782-9

Authors: De Groeve K, Deschacht N, De Koninck C, Caveliers V, Lahoutte T, Devoogdt N, Muyldermans S, De Baetselier P, Raes G

Nanobodies are single-domain antigen-binding fragments derived from heavy-chain antibodies that are devoid of light chains and occur naturally in Camelidae. We have shown before that their small size and high affinity and specificity for their target antigen make Nanobodies ideal probes for in vivo tumor imaging. In the present study, we have evaluated the use of Nanobodies as a generic method for imaging the in vivo biodistribution of specific immune cell types, using myeloid cells as an example. METHODS: The cellular specificity of Nanobodies raised against murine bone marrow-derived dendritic cells was verified using flow cytometry on a range of myeloid and nonmyeloid cell types. The Nanobodies were then labeled with (99m)Tc and their biodistribution was analyzed using SPECT. The biodistribution was also assessed by measuring radioactivity in various organs and tissues. To verify whether the observed biodistribution was due to specific targeting through the antigen-binding loops, rather than retention in organs because of effects of the framework regions, we genetically grafted the antigen-binding loops of the Nanobodies onto the framework region of a Nanobody scaffold that by itself showed low background retention in the periphery. The cellular specificity and biodistribution of these grafted Nanobodies were determined as before. RESULTS: Nb-DC2.1, which recognizes a wide range of myeloid cells, targets most strongly to the liver, spleen, and lungs. Nb-DC1.8, which recognizes immature bone marrow-derived dendritic cells in vitro, gives a much smaller signal in the liver and spleen than does Nb-DC2.1 but mainly targets to the lungs and gives a pronounced signal in the skin. Grafting of the antigen-binding loops of Nb-DC1.8 or Nb-DC2.1 to the scaffold of Nb-BCII10 alters the observed biodistribution of the Nanobodies to resemble that of the Nanobody from which the antigen-binding loops have been derived. CONCLUSION: The observed in vivo biodistribution of the Nanobodies reflects the main in vivo locations of the cells recognized by the Nanobodies and is determined by the antigen-binding loops of the Nanobodies. Thus, Nanobodies represent elegant targeting probes for imaging the in vivo biodistribution of specific immune cell types.

PMID: 20395332 [PubMed - indexed for MEDLINE]

Synthesis, biodistribution, and microsingle photon emission computed tomography (SPECT) imaging study of technetium-99m labeled PEGylated dendrimer poly(amidoamine) (PAMAM)-folic acid conjugates.

J Med Chem. 2010 Apr 22;53(8):3262-72

Authors: Zhang Y, Sun Y, Xu X, Zhang X, Zhu H, Huang L, Qi Y, Shen YM

Three conjugates based on dendrimer PAMAM generation five were synthesized and radiolabeled successfully. To investigate their tumor targeting, the in vitro and in vivo stability, cell uptake, in vivo biodistribution, and micro-SPECT imaging were evaluated, respectively. The conjugate of (99m)Tc labeled PEGylated dendrimer PAMAM folic acid conjugate ((99m)Tc-G5-Ac-pegFA-DTPA) shows much higher uptake in KB cancer cells and accumulated more in the tumor area than that of the other two conjugates. The uptake in KB cells depends on the incubation time. The results of in vivo biodistribution agree with the data obtained from micro-SPECT imaging. These studies show that PEGylation of PAMAM dendrimer folic acid conjugate improves the tumor targeting. Folate-conjugated dendrimer maybe developed to be potential radiopharmaceuticals and targeted drug delivery systems.

PMID: 20350006 [PubMed - indexed for MEDLINE]

Site-specific labeling of 'second generation' annexin V with 99mTc(CO)3 for improved imaging of apoptosis in vivo.

Bioorg Med Chem. 2010 Feb;18(3):1356-63

Authors: De Saint-Hubert M, Mottaghy FM, Vunckx K, Nuyts J, Fonge H, Prinsen K, Stroobants S, Mortelmans L, Deckers N, Hofstra L, Reutelingsperger CP, Verbruggen A, Rattat D

In this study 'second generation' AnxV was specifically labeled with (99m)Tc in three different ways outside the binding region of the protein to obtain an improved target-to-background activity ratio. The compounds were tested in vitro and in vivo in normal mice and in a model of hepatic apoptosis (anti-Fas mAb). The apoptosis binding was most prominent for the HIS-tagged 'second generation' AnxV labeled with (99m)Tc(CO)(3) in comparison to (99m)Tc-HYNIC-cys-AnxV and (99m)Tc(CO)(3)-DTPA-cys-AnxV.

PMID: 20053567 [PubMed - indexed for MEDLINE]

In vivo evaluation of [123I]-4-(2-(bis(4-fluorophenyl)methoxy)ethyl)-1-(4-iodobenzyl)piperidine, an iodinated SPECT tracer for imaging the P-gp transporter.

Nucl Med Biol. 2010 May;37(4):469-77

Authors: De Bruyne S, Wyffels L, Boos TL, Staelens S, Deleye S, Rice KC, De Vos F

INTRODUCTION: P-glycoprotein (P-gp) is an energy-dependent transporter that contributes to the efflux of a wide range of xenobiotics at the blood-brain barrier playing a role in drug-resistance or therapy failure. In this study, we evaluated [(123)I]-4-(2-(bis(4-fluorophenyl)methoxy)ethyl)-1-(4-iodobenzyl)piperidine ([(123)I]-FMIP) as a novel single photon emission computed tomography (SPECT) tracer for imaging P-gp at the brain in vivo. METHODS: The tissue distribution and brain uptake as well as the metabolic profile of [(123)I]-FMIP in wild-type and mdr1a (-/-) mice after pretreatment with physiological saline or cyclosporin A (CsA) (50 mg/kg) was investigated. The influence of increasing doses CsA on brain uptake of [(123)I]-FMIP was explored. microSPECT images of mice brain after injection of 11.1 MBq [(123)I]-FMIP were obtained for different treatment strategies thereby using the Milabs U-SPECT-II. RESULTS: Modulation of P-gp with CsA (50 mg/kg) as well as mdr1a gene depletion resulted in significant increase in cerebral uptake of [(123)I]-FMIP with only minor effect on blood activity. [(123)I]-FMIP is relative stable in vivo with >80% intact [(123)I]-FMIP in brain at 60 min p.i. in the different treatment regiments. A dose-dependent sigmoidal increase in brain uptake of [(123)I]-FMIP with increasing doses of CsA was observed. In vivo region of interest-based SPECT measurements correlated well with the observations of the biodistribution studies. CONCLUSIONS: These findings indicate that [(123)I]-FMIP can be applied to assess the efficacy of newly developed P-gp modulators. It is also suggested that [(123)I]-FMIP is a promising SPECT tracer for imaging P-gp at the blood-brain barrier.

PMID: 20447559 [PubMed - in process]

In vitro and in vivo evaluations of a radioiodinated thymidine phosphorylase inhibitor as a tumor diagnostic agent for angiogenic enzyme imaging.

Nucl Med Biol. 2010 May;37(4):427-32

Authors: Akizawa H, Zhao S, Takahashi M, Nishijima K, Kuge Y, Tamaki N, Seki K, Ohkura K

INTRODUCTION: The expression of thymidine phosphorylase (TP) is closely associated with angiogenesis, tumor invasiveness and activation of antitumor agents. We evaluated radioiodinated 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil ([(125)I]IIMU) having high TP-inhibitory potency as the new radiotracer for SPECT targeting of TP expression in tumors. METHODS: The characteristics of the radioiodinated TP inhibitor IIMU were determined by evaluating the uptake by tumor cells in vitro and by biodistribution studies in vivo. The distribution of the radiotracer and the extent of TP-specific uptake by tumors were evaluated by a counting method in tumor-bearing mice. RESULTS: The in vitro uptake of radiolabeled IIMU by A431 cells along with high TP expressions was attributed to the binding of the radiotracer to its target enzyme, i.e., TP. In vivo distribution of the radiotracer in A431 tumor-bearing mice revealed tumor/blood and tumor/muscle activity uptake ratios of 36 and 106, respectively, at 3 h after the radiotracer injection. On using low TP-expressing tumors and TP blocking studies as controls, minor TP-specific accumulation of the radiotracer was detected in these studies. CONCLUSION: According to the binding of radioiodinated IIMU to the angiogenic enzyme TP, it can be concluded that radioiodinated IIMU might be suitable as a SPECT tracer for tumor imaging.

PMID: 20447553 [PubMed - in process]

Molecular Imaging of Atherosclerotic Plaques Targeted to Oxidized LDL Receptor LOX-1 Using SPECT/CT and Magnetic Resonance.

Circ Cardiovasc Imaging. 2010 May 4;

Authors: Li D, Patel A, Klibanov AL, Kramer CM, Ruiz M, Kang BY, Mehta JL, Beller GA, Glover DK, Meyer CH

BACKGROUND: -The oxidized-LDL receptor LOX-1 plays a crucial role in atherosclerosis. We sought to detect and assess atherosclerotic plaque in vivo using SPECT/CT and magnetic resonance imaging (MRI) using a molecular probe targeted at LOX-1. Methods & Results-Apo E(-/-) mice on Western diet and LDLR(-/-) and LDLR(-/-)/LOX-1(-/-) mice on atherogenic diet were used. Imaging probes consisted of liposomes decorated with anti-LOX-1 antibodies (LOX-1) or nonspecific IgG (nIgG), (111)In or gadolinium (Gd), and DiI fluorescence markers. In vivo imaging was performed 24 hrs after intravenous injection (150 mul) of LOX-1 (or nIgG) probes labeled with either (111)In (600 muCi) or Gd (0.075 mmol/kg) followed by aortic excision for phosphor imaging and Sudan IV staining or fluorescence imaging and H&E staining. The LOX-1 probe was also co-localized with specific cell types, apoptosis, and MMP9 expression using frozen aortic sections. SPECT/CT imaging of the LOX-1 probe showed aortic arch hotspots in Apo E(-/-) mice (n=8), confirmed by phosphor imaging. MRI showed significant Gd enhancement in atherosclerotic plaques in LDLR(-/-) mice with the LOX-1 (n=7), but not nIgG, probe (n=5). No signal enhancement was observed in LDLR(-/-)/LOX-1(-/-) mice injected with LOX-1 probe (n=5). These results were confirmed by ex-vivo fluorescence imaging. The LOX-1 probe bound preferentially to the plaque shoulder, a region with vulnerable plaque features including extensive LOX-1 expression, macrophage accumulation, apoptosis and MMP9 expression. CONCLUSIONS: -LOX-1 can be used as a target for molecular imaging of atherosclerotic plaque in vivo. Furthermore, LOX-1 imaging signal is associated with markers of rupture-prone atherosclerotic plaque.

PMID: 20442371 [PubMed - as supplied by publisher]

Therapeutic efficacy and microSPECT/CT imaging of 188Re-DXR-liposome in a C26 murine colon carcinoma solid tumor model.

Nucl Med Biol. 2010 Jan;37(1):95-104

Authors: Chang YJ, Chang CH, Yu CY, Chang TJ, Chen LC, Chen MH, Lee TW, Ting G

Nanocarriers can selectively target cancer sites and carry payloads, thereby improving diagnostic and therapeutic effectiveness and reducing toxicity. The objective of this study was to investigate the therapeutic efficacy of a new co-delivery radiochemotherapeutics of (188)Re-N,N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA)-labeled pegylated liposomal doxorubicin (DXR) ((188)Re-DXR-liposome) in a C26 murine colon carcinoma solid tumor model. To evaluate the targeting and localization of (188)Re-DXR-liposome in C26 murine tumor-bearing mice, biodistribution, microSPECT/CT imaging and pharmacokinetic studies were performed. The antitumor effect of (188)Re-DXR-liposome was assessed by tumor growth inhibition, survival ratio and histopathological hematoxylin-eosin staining. The tumor target and localization of the nanoliposome delivery radiochemotherapeutics of (188)Re-DXR-liposome were demonstrated in the biodistribution, pharmacokinetics and in vivo nuclear imaging studies. In the study on therapeutic efficacy, the tumor-bearing mice treated with bimodality radiochemotherapeutics of (188)Re-DXR-liposome showed better mean tumor growth inhibition rate (MGI) and longer median survival time (MGI=0.048; 74 days) than those treated with radiotherapeutics of (188)Re-liposome (MGI=0.134; 60 days) and chemotherapeutics of Lipo-Dox (MGI=0.413; 38 days). The synergistic tumor regression effect was observed with the combination index (CI) exceeding 1 (CI=1.145) for co-delivery radiochemotherapeutics of (188)Re-DXR-liposome. Two (25%) of the mice treated with radiochemotherapeutics were completely cured after 120 days. The therapeutic efficacy of radiotherapeutics of (188)Re-liposome and the synergistic effect of the combination radiochemotherapeutics of (188)Re-DXR-liposome have been demonstrated in a C26 murine solid tumor animal model, which pointed to the potential benefit and promise of the co-delivery of nanoliposome radiochemotherapeutics for adjuvant cancer treatment on oncology applications.

PMID: 20122674 [PubMed - indexed for MEDLINE]