Synthesis and In Vivo Evaluation of the Biodistribution of a </sup>18 F Labelled Conjugate Gold-Nanoparticle-Peptide with Potential Biomedical Application.

Bioconjug Chem. 2012 Jan 30;

Authors: Guerrero S, Herance R, Rojas S, Mena J, Gispert J, Acosta G, Albericio PD, Kogan MJ

Abstract
Gold nanoparticles (AuNP) have been extensively used in biological applications because of their biocompatibility, size, ease of characterization, and rich history of surface chemistry. These features make these structures readily exploitable to meet the requirements of biomedical applications which include novel diagnostic and therapeutic approaches and for drug delivery. In a previous work we studied the ex vivo distribution of a conjugate C(AuNP)-LPFFD for potential uses in therapy of Alzheimer's disease. In this study we labeled covalently a AuNP-peptide conjugate that contains the sequences CLPFFD and CK with [</sup>18 F]fluorobenzoate to study in vivo the distribution of the AuNP by positron emission tomography (PET). After intravenous administration in mice the highest concentration of the radiolabeled conjugate was found in the bladder and urine and in a lower proportion in intestine, which showed progressive accumulation, compatible with biliary excretion of the conjugate. The conjugate accumulated in liver and spleen. PET imaging allow us to study in a non-invasive and sensitive way the in vivo biodistribution of the AuNPs using a reduced number of animals. Our results are a proof that AuNP can covalently and radioactively be labelled for PET biodistribution studies.

PMID: 22284226 [PubMed - as supplied by publisher]

Multifunctional unimolecular micelles for cancer-targeted drug delivery and positron emission tomography imaging.

Biomaterials. 2012 Jan 24;

Authors: Xiao Y, Hong H, Javadi A, Engle JW, Xu W, Yang Y, Zhang Y, Barnhart TE, Cai W, Gong S

Abstract
A multifunctional unimolecular micelle made of a hyperbranched amphiphilic block copolymer was designed, synthesized, and characterized for cancer-targeted drug delivery and non-invasive positron emission tomography (PET) imaging in tumor-bearing mice. The hyperbranched amphiphilic block copolymer, Boltorn(®) H40-poly(L-glutamate-hydrazone-doxorubicin)-b-poly(ethylene glycol) (i.e., H40-P(LG-Hyd-DOX)-b-PEG), was conjugated with cyclo(Arg-Gly-Asp-D-Phe-Cys) peptides (cRGD, for integrin α(v)β(3) targeting) and macrocyclic chelators (1,4,7-triazacyclononane-N, N', N''-triacetic acid [NOTA], for (64)Cu-labeling and PET imaging) (i.e., H40-P(LG-Hyd-DOX)-b-PEG-OCH(3)/cRGD/NOTA, also referred to as H40-DOX-cRGD). The anti-cancer drug, doxorubicin (DOX) was covalently conjugated onto the hydrophobic segments of the amphiphilic block copolymer arms (i.e., PLG) via a pH-labile hydrazone linkage to enable pH-controlled drug release. The unimolecular micelles exhibited a uniform size distribution and pH-sensitive drug release behavior. cRGD-conjugated unimolecular micelles (i.e., H40-DOX-cRGD) exhibited a much higher cellular uptake in U87MG human glioblastoma cells due to integrin α(v)β(3)-mediated endocytosis than non-targeted unimolecular micelles (i.e., H40-DOX), thereby leading to a significantly higher cytotoxicity. In U87MG tumor-bearing mice, H40-DOX-cRGD-(64)Cu also exhibited a much higher level of tumor accumulation than H40-DOX-(64)Cu, measured by non-invasive PET imaging and confirmed by biodistribution studies and ex vivo fluorescence imaging. We believe that unimolecular micelles formed by hyperbranched amphiphilic block copolymers that synergistically integrate passive and active tumor-targeting abilities with pH-controlled drug release and PET imaging capabilities provide the basis for future cancer theranostics.

PMID: 22281424 [PubMed - as supplied by publisher]

PET imaging with [18F]AV-45 in an APP/PS1-21 murine model of amyloid plaque deposition.

Neurobiol Aging. 2012 Jan 23;

Authors: Poisnel G, Dhilly M, Moustié O, Delamare J, Abbas A, Guilloteau D, Barré L

Abstract
Alzheimer's disease (AD), the most common age-related neurodegenerative disorder, is characterized by the accumulation of β-amyloid peptide. In man, [18F]AV-45 with positron emission tomography (PET) is currently studied and used to track in vivo amyloid accumulation. Here, [18F]-AV45-PET was used to visualize amyloid deposition in a transgenic murine model of amyloidosis (APP/PS1-21). Studies were performed ex vivo by autoradiography and in vivo by microPET. Autoradiograms of the brain sections highlighted an increased uptake of [18F]AV-45 in APP/PS1-21 mice compared with age-matched control mice. From 8 months, an intense labeling was observed in cortex, hippocampus, and striatum. The marked accumulation of radiotracer was found in close association with thioflavin S-positive amyloid plaques. The longitudinal microPET assessment, performed from 3 to 12 months of age, demonstrated an increased [18F]AV-45 uptake in APP/PS1-21 compared with control mice. The elevated tracer uptake was increased in association with age. This study opens the possibility of [18F]AV-45, coupled with microPET, to visualize and quantitatively measure amyloid deposits in the brains of living APP/PS1 mice.

PMID: 22277262 [PubMed - as supplied by publisher]

Mechanism of cell death mediated by a BF2-chelated tetraaryl-azadipyrromethene photodynamic therapeutic: dissection of the apoptotic pathway in vitro and in vivo.

Int J Cancer. 2012 Feb 1;130(3):705-15

Authors: O'Connor AE, Mc Gee MM, Likar Y, Ponomarev V, Callanan JJ, O'shea DF, Byrne AT, Gallagher WM

Abstract
Photodynamic therapy (PDT) is an established treatment modality for cancer. ADPM06 is an emerging non-porphyrin PDT agent which has been specifically designed for therapeutic application. Recently, we have demonstrated that ADPM06-PDT is well tolerated in vivo and elicits impressive complete response rates in various models of cancer when a short drug-light interval is applied. Herein, the mechanism of action of ADPM06-PDT in vitro and in vivo is outlined. Using a drug and light combination that reduces the clonogenicity of MDA-MB-231 cells by >90%, we detected a well-orchestrated apoptotic response accompanied by the activation of various caspases in vitro. The generation of reactive oxygen species (ROS) upon photosensitizer irradiation was found to be the key instigator in the observed apoptotic response, with the endoplasmic reticulum (ER) found to be the intracellular site of initial PDT damage, as determined by induction of a rapid ER stress response post-PDT. PDT-induced apoptosis was also found to be independent of p53 tumor suppressor status. A robust therapeutic response in vivo was demonstrated, with a substantial reduction in tumor proliferation observed, as well as a rapid induction of apoptosis and initiation of ER stress, mirroring numerous aspects of the mechanism of action of ADPM06 in vitro. Finally, using a combination of (18) F-labeled 3'-deoxy-3'-fluorothymidine ((18) F-FLT) nuclear and optical imaging, a considerable decrease in tumor proliferation over 24-hr in two models of human cancer was observed. Taken together, this data clearly establishes ADPM06 as an exciting novel PDT agent with significant potential for further translational development.

PMID: 21413012 [PubMed - indexed for MEDLINE]

Evaluation of the relationship between [(18)F]FDG and P-glycoprotein expression: an experimental study.

Nucl Med Biol. 2012 Jan 18;

Authors: Yu C, Wan W, Zhang B, Deng S, Yen TC, Wu Y

Abstract
INTRODUCTION: P-glycoprotein (P-gp) is a cell-membrane-associated protein that transports a variety of drug substrates. We sought to evaluate the relationship between 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) and P-gp expression using breast carcinoma Bcap37/multidrug resistant (MDR1) and Bcap37 in vitro and in vivo. METHODS: The function of P-gp expressed in Bcap37/MDR1 cells was evaluated using verapamil (VER), a classical inhibitor of P-gp. The accumulation of (99m)Tc-methoxyisobutylisonitrile ([(99m)Tc]MIBI) in vitro was measured. In vivo imaging of severe combined immune deficiency (SCID) mice implanted with Bcap37 and Bcap37/MDR1 cells was performed by scintigraphy and micro-positron emission tomography (PET). RESULTS: The uptake of [(99m)Tc]MIBI was 0.62%±0.05% in the Bcap37/MDR1 cells and 2.02%±0.28% in the Bcap37 cells. VER significantly increased the uptake of [(99m)Tc]MIBI in the Bcap37/MDR1 cells (1.90%±0.09%) but not in the Bcap37 cells (2.15%±0.27%). In vivo, neither the Bcap37 nor Bcap37/MDR1 tumors grown in the SCID mice could be detected by [(99m)Tc]MIBI scintigraphy. Both the Bcap37 and Bcap37/MDR1 tumors were visible by micro-PET. The mean standardized uptake value (SUV) was significantly higher in the Bcap37 tumors (1.00±0.06) than in the Bcap37/MDR1 (0.67±0.11) tumors. VER significantly increased the mean SUV in the Bcap37/MDR1 tumors (1.02±0.16) but not in the Bcap37 tumors (1.09±0.22). CONCLUSIONS: [(18)F]FDG combined with VER may be an effective noninvasive method of determining P-gp expression in tumors.

PMID: 22264856 [PubMed - as supplied by publisher]

Tumor-targeted polydiacetylene micelles for in vivo imaging and drug delivery.

Small. 2011 Oct 4;7(19):2786-92

Authors: Mackiewicz N, Gravel E, Garofalakis A, Ogier J, John J, Dupont DM, Gombert K, Tavitian B, Doris E, Ducongé F

Abstract
In vivo tumor targeting and drug delivery properties of small polymerized polydiacetylene (PDA) micelles (∼10 nm) is investigated in a murine MDA-MB-231 xenograft model of breast cancer. Three micelles with different surface coatings are synthesized and tested for their ability to passively target tumor through the enhanced permeability and retention effect. After injection (24 h), fluorescence diffuse optical tomographic imaging indicates a tumor uptake of nearly 3% of the injected dose for the micelles with a 2 kDa poly(ethylene glycol) (PEG)-coating (PDA-PEG2000). The uptake of PDA micelles in tumors is confirmed by co-localization with [(18) F]-fluorodeoxyglucose (FDG) positron emission tomography. Although FDG has a higher diffusion rate in tumors, 40 ± 19% of the retained micelles is co-registered with the tumor volume visualized by FDG. Finally, PDA-PEG2000 micelles are loaded with the hydrophobic anticancer drug paclitaxel and used in vivo to inhibit tumor growth. These findings demonstrate the potential of PDA-PEG2000 micelles for both in vivo tumor imaging and drug delivery applications.

PMID: 21837631 [PubMed - indexed for MEDLINE]

In vitro and in vivo evaluation of a (64)Cu-labeled NOTA-Bn-SCN-Aoc-bombesin analogue in gastrin-releasing peptide receptor expressing prostate cancer.

Nucl Med Biol. 2012 Jan 18;

Authors: Craft JM, De Silva RA, Lears KA, Andrews R, Liang K, Achilefu S, Rogers BE

Abstract
INTRODUCTION: Bombesin (BN) is an amphibian peptide that binds to the gastrin-releasing peptide receptor (GRPR). It has been demonstrated that BN analogues can be radiolabeled for potential diagnosis and treatment of GRPR-expressing malignancies. Previous studies have conjugated various chelators to the eight C-terminal amino acids of BN [BN(7-14)] for radiolabeling with (64)Cu. Recently, (1,4,7-triazacyclononane-1,4,7-triacetic acid) (NOTA) has been evaluated as the five-coordinate (64)Cu complex, with results indicating GRPR-specific tumor uptake. This study aimed to conjugate S-2-(4-isothiocyanatobenzyl)-NOTA (p-SCN-Bn-NOTA) to BN(7-14) such that it could form a six-coordinate complex with (64)Cu and to evaluate the resulting peptide. METHODS: p-SCN-NOTA was conjugated to 8-aminooctanoic acid (Aoc)-BN(7-14) in solution to yield NOTA-Bn-SCN-Aoc-BN(7-14). The unlabeled peptide was evaluated in a cell binding assay using PC-3 prostate cancer cells and (125)I-Tyr(4)-BN to determine the IC(50) value. The peptide was radiolabeled with (64)Cu and evaluated for internalization into PC-3 cells and for tumor uptake in mice bearing PC-3 xenografts using biodistribution and micro-positron emission tomography imaging studies. RESULTS: The binding assay demonstrated that NOTA-Bn-SCN-Aoc-BN(7-14) bound with high affinity to GRPR with an IC(50) of 1.4 nM. The radiolabeled peptide demonstrated time-dependent internalization into PC-3 cells. In vivo, the peptide demonstrated tumor-specific uptake and imaging that were comparable to those of previously reported (64)Cu-labeled BN analogues. CONCLUSIONS: These studies demonstrate that (64)Cu-NOTA-Bn-SCN-Aoc-BN(7-14) binds to GRPR-expressing cells and that it can be used for imaging of GRPR-expressing prostate cancer.

PMID: 22261146 [PubMed - as supplied by publisher]

In vivo positron emission tomography imaging using the sodium iodide symporter as a reporter gene.

Methods Mol Biol. 2012;797:89-96

Authors: Tran L, Dartial N, Hindorf C, Vassaux G

Abstract
Information regarding the biodistribution and kinetics of spread of oncolytic viruses is crucial for safety considerations in the design of future, more efficient reagents. Although optical imaging can be used to gain this information in rodent models, imaging with radioactive isotopes presents the advantage of being directly applicable to humans, and preclinical imaging data can provide a basis for the design of clinical protocols. In this chapter, we describe the use of the Na/I symporter as a reporter gene, associated with (124)I-NaI as a radiotracer, to monitor the anatomical localization, as well as the propagation, of oncolytic viruses using dedicated, preclinical positron emission tomography scanners.

PMID: 21948471 [PubMed - indexed for MEDLINE]

L(1)-regularized Cerenkov luminescence tomography with a SP(3) method and CT fusion.

Conf Proc IEEE Eng Med Biol Soc. 2011 Aug;2011:6158-61

Authors: Zhong J, Tian J, Yang X, Qin C

Abstract
Imaging modality of radionuclides has been enriched by an optical approach, Cerenkov luminescence tomography (CLT). Referred to the traditional radionuclide imaging, such as positron emission tomography (PET) or single photon emission computed tomography (SPECT), any incremental improvement of CLT imaging is consistent with the application to information needs. In this contribution, the paper presents an l(1)-regularized imaging method for CLT problem. After utilizing the Vavilov-Cerenkov effect via third-order simplified spherical harmonics (SP(3)) approximation, we establish the large-scale linear equations in the CLT framework. The derived linear problem is seriously ill-posed, and transformed into an l(1)-regularized least squares program. The inverse solution to these equations is the three-dimensional radioisotope recovery data by an interior-point method. In the physical phantom and the in vivo mouse experiment, results demonstrate that the proposed technique produces better imaging quality and improves the reconstruction efficacy, compared with those from diffusion approximation with the Tikhonov regularization.

PMID: 22255745 [PubMed - in process]

Synthesis and Evaluation of (18)F-Labeled Styryltriazole and Resveratrol Derivatives for β-Amyloid Plaque Imaging.

J Med Chem. 2012 Jan 11;

Authors: Lee I, Choe YS, Choi JY, Lee KH, Kim BT

Abstract
In the present study, a styryltriazole and four resveratrol derivatives were synthesized as candidates for β-amyloid (Aβ) plaque imaging. On the basis of their binding affinities to Aβ(1-42) aggregates, the styryltriazole (1, K(i) = 12.8 nM) and one resveratrol derivative (5, K(i) = 0.49 nM) were labeled with (18)F. In normal mice, tissue distribution of [(18)F]5 showed good initial brain uptake (3.26% ID/g at 2 min) but slow wash-out from brains (2-to-60 min uptake ratio: 2.9). Furthermore, it underwent in vivo metabolic defluorination (1.88% ID/g at 2 min and 9.73% ID/g at 60 min). In contrast, [(18)F]1 displayed high initial brain uptake (5.38% ID/g at 2 min) with rapid wash-out from brains (0.52% ID/g at 60 min; 2-to-60 min uptake ratio: 10.3). These results indicate that [(18)F]1 has in vivo kinetics comparable to PET radiopharmaceuticals currently under commercial development, demonstrating that [(18)F]1 is a desirable PET radioligand for Aβ plaque imaging.

PMID: 22236086 [PubMed - as supplied by publisher]

Optical Imaging with HER2-targeted Affibody Molecules can monitor Hsp90 treatment response in a breast cancer xenograft mouse model.

Clin Cancer Res. 2012 Jan 10;

Authors: Van de Ven SM, Elias SG, Chan CT, Miao Z, Cheng Z, De A, Gambhir SS

Abstract
PURPOSE: To determine if optical imaging can be used for in vivo therapy response monitoring as an alternative to radionuclide techniques. We evaluated the known Her2 response to 17-DMAG treatment, a Hsp90 inhibitor.Experimental design: After in vitro 17-DMAG treatment response evaluation of MCF7 parental cells and two HER2 transfected clones (Clone A medium, B high Her2 expression), we established human breast cancer xenografts in nude mice for in vivo evaluation. Mice received 120 mg/kg of 17-DMAG in 4 doses at 12h intervals i.p. (n=14), or PBS as carrier control (n=9). Optical images were obtained pre-treatment (day 0) and post-treatment (day 3, 6, and 9), always 5h post-injection of 500 pmol of anti-Her2 Affibody-AlexaFluor680 via tail vein (with pre-injection background subtraction). Day 3 and 9 in vivo optical imaging signal was correlated with ex vivo Her2 levels by western blot.RESULTS: Her2 expression decreased with 17-DMAG dose in vitro. In vivo optical imaging signal was reduced by 22.5% in Clone B (p=0.003) and 9% in MCF7 parental tumors (p=0.23) at 3 days after 17-DMAG treatment; optical imaging signal recovered in both tumor types at day 6-9. In the carrier group no signal reduction was observed. Pearson correlation of in vivo optical imaging signal with ex vivo Her2 levels ranged from 0.73 to 0.89.CONCLUSION: Optical imaging with an affibody can be used to non-invasively monitor changes in Her2 expression in vivo as a response to treatment with an Hsp90 inhibitor, with results similar to response measurements in PET imaging studies.

PMID: 22235098 [PubMed - as supplied by publisher]

Evaluation of deuterated 18F- and 11C-labeled choline analogs for cancer detection by positron emission tomography.

Clin Cancer Res. 2012 Jan 10;

Authors: Witney TH, Alam IS, Turton DR, Smith G, Carroll L, Brickute D, Twyman FJ, Nguyen QD, Tomasi G, Awais RO, Aboagye EO

Abstract
PURPOSE: (11)C-Choline positron emission tomography (PET) has been exploited to detect the aberrant choline metabolism in tumors. Radiolabeled choline uptake within the imaging time is primarily a function of transport, phosphorylation and oxidation. Rapid choline oxidation, however, complicates interpretation of PET data. In this study we investigated the biological basis of the oxidation of deuterated choline analogues and assessed their specificity in human tumor xenografts. EXPERIMENTAL DESIGN: (11)C-Choline, (11)C-methyl-[1,2-(2)H(4)]-choline ((11)C-D4-choline) and (18)F-D4-choline were synthesized to permit comparison. Biodistribution, metabolism, small-animal PET studies, and kinetic analysis of tracer uptake were performed in human colon HCT116 xenograft-bearing mice. RESULTS: Oxidation of choline analogs to betaine was highest with (11)C-choline, with reduced oxidation observed with (11)C-D4-choline and substantially reduced with (18)F-D4-choline; suggesting that both fluorination and deuteration were important for tracer metabolism. While all tracers were converted intracellularly to labeled phosphocholine (specific signal), the higher rate constants for intracellular retention (K(i) and k(3)) of (11)C-choline and (11)C-D4-choline, compared to (18)F-D4-choline were explained by the rapid conversion of the non-fluorinated tracers to betaine within HCT116 tumors. Imaging studies showed that the uptake of (18)F-D4-choline in three tumors with similar radiotracer delivery (K(1)) and choline kinase α expression - HCT116, A375 and PC3-M - were the same, suggesting that (18)F-D4-choline has utility for cancer detection irrespective of histological type. CONCLUSIONS: We have demonstrated here that both deuteration and fluorination combine to provide protection against choline oxidation in vivo. (18)F-D4-choline showed the highest selectivity for phosphorylation and warrants clinical evaluation.

PMID: 22235095 [PubMed - as supplied by publisher]

Matrix metalloproteinase-9 is a diagnostic marker of heterotopic ossification in a murine model.

Tissue Eng Part A. 2011 Oct;17(19-20):2487-96

Authors: Rodenberg E, Azhdarinia A, Lazard ZW, Hall M, Kwon SK, Wilganowski N, Salisbury EA, Merched-Sauvage M, Olmsted-Davis EA, Sevick-Muraca EM, Davis AR

Abstract
Heterotopic ossification (HO) is a serious disorder that occurs when there is aberrant bone morphogenic protein (BMP) signaling in soft tissues. Currently, there are no methods to detect HO before mineralization occurs. Yet once mineralization occurs, there are no effective treatments, short of surgery, to reverse HO. Herein, we used in vivo molecular imaging and confirmatory ex vivo tissue analyses of an established murine animal model of BMP-induced HO to show that matrix metalloproteinase-9 (MMP-9) can be detected as an early-stage biomarker before mineralization. Ex vivo analyses show that active MMP-9 protein is significantly elevated within tissues undergoing HO as early as 48 h after BMP induction, with its expression co-localizing to nerves and vessels. In vivo molecular imaging with a dual-labeled near-infrared fluorescence and micro-positron emission tomography (μPET) agent specific to MMP-2/-9 expression paralleled the ex vivo observations and reflected the site of HO formation as detected from microcomputed tomography 7 days later. The results suggest that the MMP-9 is a biomarker of the early extracellular matrix (ECM) re-organization and could be used as an in vivo diagnostic with confirmatory ex vivo tissue analysis for detecting HO or conversely for monitoring the success of tissue-engineered bone implants that employ ECM biology for engraftment.

PMID: 21599541 [PubMed - indexed for MEDLINE]

Positron Emission Tomography and Near-Infrared Fluorescence Imaging of Vascular Endothelial Growth Factor with Dual-Labeled Bevacizumab.

Am J Nucl Med Mol Imaging. 2012 Jan 1;2(1):1-13

Authors: Zhang Y, Hong H, Engle JW, Yang Y, Barnhart TE, Cai W

Abstract
The pivotal role of vascular endothelial growth factor (VEGF) in cancer is underscored by the approval of bevacizumab (Bev, a humanized anti-VEGF monoclonal antibody) for first line treatment of cancer patients. The aim of this study was to develop a dual-labeled Bev for both positron emission tomography (PET) and near-infrared fluorescence (NIRF) imaging of VEGF. Bev was conjugated to a NIRF dye (i.e. 800CW) and 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) before (64)Cu-labeling. Flow cytometry analysis of U87MG human glioblastoma cells revealed no difference in VEGF binding affinity/specificity between Bev and NOTA-Bev-800CW. (64)Cu-labeling of NOTA-Bev-800CW was achieved with high yield. Serial PET imaging of U87MG tumor-bearing female nude mice revealed that tumor uptake of (64)Cu-NOTA-Bev-800CW was 4.6 ± 0.7, 16.3 ± 1.6, 18.1 ± 1.4 and 20.7 ± 3.7 %ID/g at 4, 24, 48 and 72 h post-injection respectively (n = 4), corroborated by in vivo/ex vivo NIRF imaging and biodistribution studies. Tumor uptake as measured by ex vivo NIRF imaging had a good linear correlation with the %ID/g values obtained from PET (R(2) = 0.93). Blocking experiments and histology both confirmed the VEGF specificity of (64)Cu-NOTA-Bev-800CW. The persistent, prominent, and VEGF-specific uptake of (64)Cu-NOTA-Bev-800CW in the tumor, observed by both PET and NIRF imaging, warrants further investigation and future clinical translation of such Bev-based imaging agents.

PMID: 22229128 [PubMed - as supplied by publisher]

Synthesis and preliminary evaluation of [(18)F]-labeled 2-oxoquinoline derivatives for PET imaging of cannabinoid CB(2) receptor.

Nucl Med Biol. 2012 Jan 4;

Authors: Turkman N, Shavrin A, Paolillo V, Yeh HH, Flores L, Soghomonian S, Rabinovich B, Volgin A, Gelovani J, Alauddin M

Abstract
INTRODUCTION: The cannabinoid receptor type 2 (CB(2)) is an important target for development of drugs and imaging agents for diseases, such as neuroinflammation, neurodegeneration and cancer. Recently, we reported synthesis and results of in vitro receptor binding of a focused library of fluorinated 2-oxoquinoline derivatives as CB(2) receptor ligands. Some of the compounds demonstrated to be good CB(2)-specific ligands with Ki values in the nanomolar to subnanomolar concentrations; therefore, we pursued the development of their (18)F-labeled analogues that should be useful for positron emission tomography (PET) imaging of CB(2) receptor expression. Here, we report the radiosynthesis of two (18)F-labeled 2-oxoquinoline derivatives and the preliminary in vitro and ex vivo evaluation of one compound as a CB(2)-specific radioligand. METHODS: 4-[(18)F]fluorobenzyl amine [(18)F]-3 was prepared by radiofluorination of 4-cyano-N,N,N-trimethylanilinium triflate salt followed by reduction with LiAlH(4) and then coupled with acid chlorides 11 and 12 to afford [(18)F]-13 and [(18)F]-14. In vitro CB(2) receptor binding assay was performed using U87 cells transduced with CB(2) and CB(1) receptor. Ex vivo autoradiography was performed with [(18)F]-14 on spleen and on CB(2)- and CB(1)-expressing and wild-type U87 subcutaneous tumors grown in mice. RESULTS: The radiochemical yields of [(18)F]-13 and [(18)F]-14 were 10%-15.0% with an average of 12% (n=10); radiochemical purity was >99% with specific activity 1200 mCi/μmol. The dissociation constant Kd for [(18)F]-14 was 3.4 nM. Ex vivo autoradiography showed accumulation of [(18)F]-14 in the CB(2)-expressing tumor. CONCLUSION: Two new [(18)F]-labeled CB(2) ligands have been synthesized. Compound [(18)F]-14 appears to be a potential PET imaging agent for the assessment of CB(2) receptor expression; however, poor solubility restrain its use in vivo.

PMID: 22226022 [PubMed - as supplied by publisher]

(64)Cu-NO2A-RGD-Glu-6-Ahx-BBN(7-14)NH(2): a heterodimeric targeting vector for positron emission tomography imaging of prostate cancer.

Nucl Med Biol. 2012 Jan 4;

Authors: Jackson AB, Nanda PK, Rold TL, Sieckman GL, Szczodroski AF, Hoffman TJ, Chen X, Smith CJ

Abstract
INTRODUCTION: The present study describes the design and development of a new heterodimeric RGD-bombesin (BBN) agonist peptide ligand for dual receptor targeting of the form (64)Cu-NO2A-RGD-Glu-6-Ahx-BBN(7-14)NH(2) in which Cu-64=a positron emitting radiometal; NO2A=1,4,7-triazacyclononane-1,4-diacetic acid; Glu=glutamic acid; 6-Ahx=6-aminohexanoic acid; RGD=the amino acid sequence [Arg-Gly-Asp], a nonregulatory peptide that has been used extensively to target α(v)β(3) receptors up-regulated on tumor cells and neovasculature; and BBN(7-14)NH(2)=Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH(2), an agonist analogue of bombesin peptide for specific targeting of the gastrin-releasing peptide receptor (GRPr). METHODS: RGD-Glu-6-Ahx-BBN(7-14)NH(2) was manually coupled with NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid), and the resulting conjugate was labeled with (64)Cu to yield (64)Cu-NO2A-RGD-Glu-6-Ahx-BBN(7-14)NH(2). Purification was achieved via reversed-phase high-performance liquid chromatography and characterization confirmed by electrospray ionization-mass spectrometry. RESULTS: Competitive displacement binding assays displayed single-digit nanomolar IC(50) values showing very high binding affinities toward the GRPr for the new heterodimeric peptide analogues. In vivo biodistribution studies showed high uptake and retention of tumor-associated radioactivity in PC-3 tumor-bearing rodent models with little accumulation and retention in nontarget tissues. The radiolabeled conjugate also exhibited rapid urinary excretion and high tumor-to-background ratios. Micro-positron emission tomography (microPET) molecular imaging investigations produced high-quality, high-contrast images in PC-3 tumor-bearing mice 15 h postinjection. CONCLUSIONS: Based on microPET imaging experiments that show high-quality, high-contrast images with virtually no residual gastrointestinal radioactivity, this new heterodimeric RGD-BBN conjugate can be considered as a promising PET tracer candidate for the diagnosis of GRPr-positive tumors in human patients.

PMID: 22226021 [PubMed - as supplied by publisher]

Syndecan-1 antigen, a promising new target for triple-negative breast cancer immuno-PET and radioimmunotherapy. A preclinical study on MDA-MB-468 xenograft tumors.

EJNMMI Res. 2011;1(1):20

Authors: Rousseau C, Ruellan AL, Bernardeau K, Kraeber-Bodéré F, Gouard S, Loussouarn D, Saï-Maurel C, Faivre-Chauvet A, Wijdenes J, Barbet J, Gaschet J, Chérel M, Davodeau F

Abstract
UNLABELLED: ABSTRACT:
BACKGROUND: Overexpression of syndecan-1 (CD138) in breast carcinoma correlates with a poor prognosis and an aggressive phenotype. The objective of this study was to evaluate the potential of targeting CD138 by immuno-PET imaging and radioimmunotherapy (RIT) using the antihuman syndecan-1 B-B4 mAb radiolabeled with either 124I or 131I in nude mice engrafted with the triple-negative MDA-MB-468 breast cancer cell line.
METHOD: The immunoreactivity of 125I-B-B4 (80%) was determined, and the affinity of 125I-B-B4 and the expression of CD138 on MDA-MB-468 was measured in vitro by Scatchard analysis. CD138 expression on established tumors was confirmed by immunohistochemistry. A biodistribution study was performed in mice with subcutaneous MDA-MB-468 and 125I-B-B4 at 4, 24, 48, 72, and 96 h after injection and compared with an isotype-matched control. Tumor uptake of B-B4 was evaluated in vivo by immuno-PET imaging using the 124I-B-B4 mAb. The maximum tolerated dose (MTD) was determined from mice treated with 131I-B-B4 and the RIT efficacy evaluated.
RESULTS: 125I-B-B4 affinity was in the nanomolar range (Kd = 4.39 ± 1.10 nM). CD138 expression on MDA-MB-468 cells was quite low (Bmax = 1.19 × 104 ± 9.27 × 102 epitopes/cell) but all expressed CD138 in vivo as determined by immunohistochemistry. The tumor uptake of 125I-B-B4 peaked at 14% injected dose (ID) per gram at 24 h and was higher than that of the isotype-matched control mAb (5% ID per gram at 24 h). Immuno-PET performed with 124I-B-B4 on tumor-bearing mice confirmed the specificity of B-B4 uptake and its retention within the tumor. The MTD was reached at 22.2 MBq. All mice treated with RIT (n = 8) as a single treatment at the MTD experienced a partial (n = 3) or complete (n = 5) response, with three of them remaining tumor-free 95 days after treatment.
CONCLUSION: These results demonstrate that RIT with 131I-B-B4 could be considered for the treatment of metastatic triple-negative breast cancer that cannot benefit from hormone therapy or anti-Her2/neu immunotherapy. Immuno-PET for visualizing CD138-expressing tumors with 124I-B-B4 reinforces the interest of this mAb for diagnosis and quantitative imaging.

PMID: 22214534 [PubMed - in process]

Uptake of 68gallium in atherosclerotic plaques in LDLR-/-ApoB100/100 mice.

EJNMMI Res. 2011;1(1):14

Authors: Silvola JM, Laitinen I, Sipilä HJ, Laine VJ, Leppänen P, Ylä-Herttuala S, Knuuti J, Roivainen A

Abstract
UNLABELLED: ABSTRACT:
BACKGROUND: Atherosclerosis is a chronic inflammatory disease of artery wall characterized by infiltration of monocytes into subendothelial space and their differentiation into macrophages. Since rupture-prone plaques commonly contain high amounts of activated macrophages, imaging of the macrophage content may provide a useful tool for the evaluation of plaque vulnerability. The purpose of this study was to explore the uptake of 68gallium (68Ga) in atherosclerotic plaques in mice.
METHODS: Uptake of ionic 68Ga was investigated in atherosclerotic LDLR-/-ApoB100/100 and C57BL/6N control mice at 3 h after injection. The ex vivo biodistribution of the 68Ga was assessed and autoradiography of aortic cryosections was defined. In vivo imaging of 68Ga was performed using a small animal positron emission tomography PET/CT scanner.
RESULTS: Our results revealed that the uptake of 68Ga-radioactivity was higher in atherosclerotic plaques than in healthy vessel wall (ratio 1.8 ± 0.2, p = 0.0002) and adventitia (ratio 1.3 ± 0.2, p = 0.0011). The autoradiography signal co-localized with macrophages prominently as demonstrated by Mac-3 staining. In both mice strains, the highest level of radioactivity was found in the blood.
CONCLUSIONS: We observed a moderate but significantly elevated 68Ga-radioactivity uptake in the aortic plaques of atherosclerotic mice, especially at the sites rich in macrophages. While the uptake of 68Ga was promising in this animal model, the slow blood clearance may limit the usability of 68Ga as a PET tracer for clinical imaging of atherosclerotic plaques.

PMID: 22214258 [PubMed - in process]

Nicotinic acetylcholine receptors in rat forebrain that bind (18) F-nifene: Relating PET imaging, autoradiography and behavior.

Synapse. 2011 Dec 28;

Authors: Bieszczad KM, Kant R, Constantinescu CC, Pandey SK, Kawai HD, Metherate R, Weinberger NM, Mukherjee J

Abstract
Nicotinic acetylcholine receptors (nAChRs) in the brain are important for cognitive function; however, their specific role in relevant brain regions remains unclear. In this study we used the novel compound (18) F-nifene to examine the distribution of nAChRs in the rat forebrain, and for individual animals related the results to behavioral performance on an auditory-cognitive task. We first show negligible binding of (18) F-nifene in mice lacking the β2 nAChR subunit, consistent with previous findings that (18) F-nifene binds to α4β2* nAChRs. We then examined the distribution of (18) F-nifene in rat using three methods: in vivo PET, ex vivo PET and autoradiography. Generally, (18) F-nifene labeled forebrain regions known to contain nAChRs, and the three methods produced similar relative binding among regions. Importantly, (18) F-nifene also labeled some white matter (myelinated axon) tracts, most prominently in the temporal subcortical region that contains the auditory thalamocortical pathway. Finally, we related (18) F-nifene binding in several forebrain regions to each animal's performance on an auditory-cued, active avoidance task. The strongest correlations with performance after 14 days training were found for (18) F-nifene binding in the temporal subcortical white matter, subiculum and medial frontal cortex (correlation coefficients, r > 0.8); there was no correlation with binding in the auditory thalamus or auditory cortex. These findings suggest that individual performance is linked to nicotinic functions in specific brain regions, and further support a role for nAChRs in sensory-cognitive function. Synapse, 2011. © 2011 Wiley-Liss, Inc.

PMID: 22213342 [PubMed - as supplied by publisher]

PET Imaging of Integrin Positive Tumors Using F Labeled Knottin Peptides.

Theranostics. 2011;1:403-12

Authors: Liu S, Liu H, Ren G, Kimura RH, Cochran JR, Cheng Z

Abstract
Purpose: Cystine knot (knottin) peptides, engineered to bind with high affinity to integrin receptors, have shown promise as molecular imaging agents in living subjects. The aim of the current study was to evaluate tumor uptake and in vivo biodistribution of (18)F-labeled knottins in a U87MG glioblastoma model.Procedures: Engineered knottin mutants 2.5D and 2.5F were synthesized using solid phase peptide synthesis and were folded in vitro, followed by radiolabeling with 4-nitrophenyl 2-(18)F-fluoropropionate ((18)F-NFP). The resulting probes, (18)F-FP-2.5D and (18)F-FP-2.5F, were evaluated in nude mice bearing U87MG tumor xenografts using microPET and biodistribution studies.Results: MicroPET imaging studies with (18)F-FP-2.5D and (18)F-FP-2.5F demonstrated high tumor uptake in U87MG xenograft mouse models. The probes exhibited rapid clearance from the blood and kidneys, thus leading to excellent tumor-to-normal tissue contrast. Specificity studies confirmed that (18)F-FP-2.5D and (18)F-FP-2.5F had reduced tumor uptake when co-injected with a large excess of the peptidomimetic c(RGDyK) as a blocking agent.Conclusions: (18)F-FP-2.5D and (18)F-FP-2.5F showed reduced gallbladder uptake compared with previously published (18)F-FB-2.5D. (18)F-FP-2.5D and (18)F-FP-2.5F enabled integrin-specific PET imaging of U87MG tumors with good imaging contrasts. (18)F-FP-2.5D demonstrated more desirable pharmacokinetics compared to (18)F-FP-2.5F, and thus has greater potential for clinical translation.

PMID: 22211146 [PubMed - in process]