In vivo tracking of plasmid DNA/mRNA: A novel labelling precursor for 89Zr positron emission tomography.

Herein, we developed a novel labelling precursor Fe-DFO-5 for plasmid DNA (pDNA) utilizing 89Zr as a radioisotope for PET imaging. 89Zr-labelled pDNA showed comparable gene expression to non-labelled pDNA. The biodistribution of 89Zr-labelled pDNA after local or systemic administration in mice was evaluated. Furthermore, this labelling method was also applied to mRNA.

Stability of lenalidomide suspension after preparation by a simple suspension method for enteral tube administration.

PURPOSE: A simple suspension method has been developed for tube administration, in which tablets (and capsules) are disintegrated in hot water (55℃) without grinding (or opening) them. In the present study, we evaluated the feasibility of this simple suspension method for the preparation of lenalidomide (Celgene, Summit, New Jersey and USA) suspension by testing the stability of this drug at 55℃ and its adsorbability on the tube. METHODS: We examined, by high-performance liquid chromatography, the time-dependent changes in the concentration of lenalidomide in suspensions of the drug prepared by the simple suspension method. The high-performance liquid chromatography analyses of lenalidomide were performed on Prominence LC-20AB/SPD-20 A (Shimadzu, Kyoto, Japan) with a ZORBAX SB-C18 RR analytical column (Agilent Technologies, Santa Clara, California, USA; particle size: 2.1 × 100 mm, 3.5 µm) at a flow rate of 0.4 mL/min. A solvent system consisting of 10 mM ammonium acetate (pH 7.0)/acetonitrile was used as the eluent and the eluate was detected by UV at 254 nm. RESULTS: Lenalidomide was confirmed to remain stable in hot water at 55℃ for 24 h in the prepared suspension by the simple suspension method, and more than 99% of the drug could be recovered from the suspension. In addition, 94.5-98.0% of the drug amount could pass through a percutaneous endoscopic gastrostomy tube. Lenalidomide was scarcely adsorbed on to the percutaneous endoscopic gastrostomy tube made of polyurethane or polyvinyl chloride. CONCLUSION: Lenalidomide was found to be stable even in hot water and was not adsorbed on to the percutaneous endoscopic gastrostomy tube.

Synthesis and evaluation of a novel (99m)Tc-labeled bioreductive probe for tumor hypoxia imaging.

Tumor hypoxia is closely associated with the malignant progression and/or the high metastatic ability of tumors and often induces resistance to chemo- and/or radiotherapy. Thus, the detection and evaluation of hypoxia is important for the optimization of cancer therapy. We designed a novel (99m)Tc-labeled probe for tumor hypoxia imaging that utilizes bioreductive reactions in hypoxic cells. This probe, which contains a 4-nitrobenzyl ester group, is reduced in hypoxic cells to produce a corresponding carboxylate anion that cannot penetrate cell membranes because of its hydrophilicity and negative charge; therefore, it is expected to be trapped inside hypoxic cells. Based on this unique strategy, we synthesized the Technetium-99m ((99m)Tc)-labeled probe (99m)Tc-SD32. The uptake of (99m)Tc-SD32 in tumor cells was investigated under normoxic and hypoxic conditions. (99m)Tc-SD32 showed sufficient accumulation and good retention in hypoxic cells. In addition, we demonstrated that (99m)Tc-SD32 was subjected to bioreduction in hypoxic cells and was trapped as the corresponding carboxylate anion. These results indicated that (99m)Tc-SD32 would be a promising agent for in vivo hypoxia imaging.

Synthesis and evaluation of cyclic RGD-boron cluster conjugates to develop tumor-selective boron carriers for boron neutron capture therapy.

Boron-containing agents play a key role in successful boron neutron capture therapy (BNCT). Icosahedral boron cluster-Arg-Gly-Asp (RGD) peptide conjugates were designed, synthesized, and evaluated for the biodistribution to develop tumor-selective boron carriers. Integrin αvß3 is an attractive target for anti-tumor drug delivery because of its specific expression in proliferating endothelial and tumor cells of various origins. We, therefore, selected a c(RGDfK) moiety recognizing αvß3 as an active tumor-targeting device to conjugate with icosahedral boron-10 clusters, disodium mercaptododecaborate (BSH) or o-carborane as a thermal neutron-sensitizing unit. Preparation of o-carborane derivatives involved microwave irradiation, and resulted in high yields in a short time. An in vitro cell adhesion assay on αvß3-positive U87MG and SCCVII cells demonstrated the high binding affinity of conjugates to integrin αvß3 (IC(50)=0.19-2.66 µM). Biodistribution experiments using SCCVII-bearing mice indicated that GPU-201 showed comparable tumor uptake and a significantly longer retention in tumors compared with BSH. These results suggest that GPU-201 is a promising candidate for use in BNCT.

Biodistribution studies for cell therapy products: Current status and issues.

Information on the biodistribution (BD) of cell therapy products (CTPs) is essential for prediction and assessment of their efficacy and toxicity profiles in non-clinical and clinical studies. To conduct BD studies, it is necessary to understand regulatory requirements, implementation status, and analytical methods. This review aimed at surveying international and Japanese trends concerning the BD study for CTPs and the following subjects were investigated, which were considered particularly important: 1) comparison of guidelines to understand the regulatory status of BD studies in a global setting; 2) case studies of the BD study using databases to understand its current status in cell therapy; 3) case studies on quantitative polymerase chain reaction (qPCR) used primarily in non-clinical BD studies for CTPs; and 4) survey of imaging methods used for non-clinical and clinical BD studies. The results in this review will be a useful resource for implementing BD studies.

Recovery correction technique for NMR spectroscopy of perchloric acid extracts using DL-valine-2,3-d2: validation and application to 5-fluorouracil-induced brain damage.

PURPOSE: We explored a recovery correction technique that can correct metabolite loss during perchloric acid (PCA) extraction and minimize inter-assay variance in quantitative (1)H nuclear magnetic resonance (NMR) spectroscopy of the brain and evaluated its efficacy in 5-fluorouracil (5-FU)- and saline-administered rats. METHODS: We measured the recovery of creatine and dl-valine-2,3-d2 from PCA extract containing both compounds (0.5 to 8 mM). We intravenously administered either 5-FU for 4 days (total, 100 mg/kg body weight) or saline into 2 groups of 11 rats each. We subsequently performed PCA extraction of the whole brain on Day 9, externally adding 7 µmol of dl-valine-2,3-d2. We estimated metabolite concentrations using an NMR spectrometer with recovery correction, correcting metabolite concentrations based on the recovery factor of dl-valine-2,3-d2. For each metabolite concentration, we calculated the coefficient of variation (CEV) and compared differences between the 2 groups using unpaired t-test. RESULTS: Equivalent recoveries of dl-valine-2,3-d2 (89.4 ± 3.9%) and creatine (89.7 ± 3.9%) in the PCA extract of the mixed solution indicated the suitability of dl-valine-2,3-d2 as an internal reference. In the rat study, recovery of dl-valine-2,3-d2 was 90.6 ± 9.2%. Nine major metabolite concentrations adjusted by recovery of dl-valine-2,3-d2 in saline-administered rats were comparable to data in the literature. CEVs of these metabolites were reduced from 10 to 17% before to 7 to 16% after correction. The significance of differences in alanine and taurine between the 5-FU- and saline-administered groups was determined only after recovery correction (0.75 ± 0.12 versus 0.86 ± 0.07 for alanine; 5.17 ± 0.59 versus 5.66 ± 0.42 for taurine [µmol/g brain tissue]; P < 0.05). CONCLUSION: A new recovery correction technique corrected metabolite loss during PCA extraction, minimized inter-assay variance in quantitative (1)H NMR spectroscopy of brain tissue, and effectively detected inter-group differences in concentrations of brain metabolites between 5-FU- and saline-administered rats.

In vivo SPECT imaging with 111In-DOTA-c(RGDfK) to detect early pancreatic cancer in a hamster pancreatic carcinogenesis model.

UNLABELLED: Early detection of pancreatic cancer is key to overcoming its poor prognosis. α(v)ß(3)-integrin is often overexpressed in pancreatic tumor cells, whereas it is scarcely expressed in normal pancreatic cells. In this study, we investigated the usefulness of SPECT imaging with (111)In-1,4,7,10-tetraazacylododecane-N,N',N″,N'''-tetraacetic acid-cyclo-(Arg-Gly-Asp-d-Phe-Lys) [(111)In-DOTA-c(RGDfK)], an imaging probe of α(v)ß(3)-integrin, for the early detection of pancreatic cancer in a hamster pancreatic carcinogenesis model. METHODS: Hamsters were subcutaneously injected with the pancreatic duct carcinogen N-nitrosobis(2-oxopropyl)amine to induce pancreatic cancer. N-nitrosobis(2-oxopropyl)amine-treated hamsters underwent in vivo SPECT with (111)In-DOTA-c(RGDfK). After imaging, the tumor-to-normal pancreatic tissue radioactivity ratios in excised pancreatic samples were measured with autoradiography (ARG) and compared with the immunopathologic findings for α(v)ß(3)-integrin. In a mouse model in which inflammation was induced with turpentine, the uptake of (111)In-DOTA-c(RGDfK) in inflammatory regions was evaluated with ARG and compared with that of (18)F-FDG. RESULTS: (111)In-DOTA-c(RGDfK) was clearly visualized in pancreatic cancer lesions as small as 3 mm in diameter. ARG analysis revealed high tumor-to-normal pancreatic tissue radioactivity ratios (4.6 ± 1.0 [mean ± SD] in adenocarcinoma and 3.3 ± 1.4 in atypical hyperplasia). The uptake of (111)In-DOTA-c(RGDfK) strongly correlated with α(v)ß(3)-integrin expression. In the inflammatory model, inflammation-to-muscle ratios for (18)F-FDG and (111)In-DOTA-c(RGDfK) were 8.37 ± 4.37 and 1.98 ± 0.60, respectively. These results imply that (111)In-DOTA-c(RGDfK) has a lower rate of false-positive tumor detection than (18)F-FDG. CONCLUSION: Our findings suggest that SPECT with (111)In-DOTA-c(RGDfK) has great potential for the early and accurate detection of pancreatic cancer.

High resolution SPECT imaging for visualization of intratumoral heterogeneity using a SPECT/CT scanner dedicated for small animal imaging.

OBJECTIVES: Tumor interiors are never homogeneous and in vivo visualization of intratumoral heterogeneity would be an innovation that contributes to improved cancer therapy. But, conventional nuclear medicine tests have failed to visualize heterogeneity in vivo because of limited spatial resolution. Recently developed single photon emission computed tomographic (SPECT) scanners dedicated for small animal imaging are of interest due to their excellent spatial resolution of <1 mm, but few studies have focused on the evaluation of intratumoral heterogeneity. We investigated the optimal conditions related to high resolution imaging of heterogeneous tumor interiors using a small animal SPECT scanner. METHODS: The conditions related to SPECT/CT visualization of heterogeneous tumor interiors were investigated using phantoms with (111)In and simulations of actual small animal imaging. The optimal conditions obtained were validated by in vivo imaging of sarcoma 180-bearing mice. RESULTS: Larger number of counts must be obtained within limited acquisition time to visualize tumor heterogeneity in vivo in animal imaging, compared to cases that simply detect tumors. At an acquisition time of 30 min, better image quality was obtained with pinhole apertures diameter of 1.4 mm than of 1.0 mm. The obtained best spatial resolution was 1.3 mm, it was acceptable for our purpose, though a little worse than the best possible performance of the scanner (1.0 mm). Additionally, the reconstruction parameters, such as noise suppression, voxel size, and iteration/subset number, needed to be optimized under the limited conditions and were different from those found under the ideal condition. The minimal radioactivity concentration for visualization of heterogeneous tumor interiors was estimated to be as high as 0.2-0.5 MBq/mL. Liposomes containing (111)In met this requirement and were administered to tumor-bearing mice. SPECT imaging successfully showed heterogeneous (111)In distribution within the tumors in vivo with good spatial resolution. A threshold of 0.2 MBq/g for clear visualization of tumor heterogeneity was validated. Autoradiograms obtained ex vivo of excised tumors confirmed that the in vivo SPECT images accurately depicted the heterogeneous intratumoral accumulation of liposomes. CONCLUSION: Intratumoral heterogeneity was successfully visualized under the optimized conditions using a SPECT/CT scanner.

Evaluating the Usefulness of a Novel 10B-Carrier Conjugated With Cyclic RGD Peptide in Boron Neutron Capture Therapy.

BACKGROUND: To evaluate the usefulness of a novel 10B-carrier conjugated with an integrin-binding cyclic RGD peptide (GPU-201) in boron neutron capture therapy (BNCT). METHODS: GPU-201 was synthesized from integrin-binding Arg-Gly-Asp (RGD) consensus sequence of matrix proteins and a 10B cluster 1, 2-dicarba-closo-dodecaborane-10B. Mercaptododecaborate-10B (BSH) dissolved in physiological saline and BSH and GPU-201 dissolved with cyclodextrin (CD) as a solubilizing and dispersing agent were intraperitoneally administered to SCC VII tumor-bearing mice. Then, the 10B concentrations in the tumors and normal tissues were measured by γ-ray spectrometry. Meanwhile, tumor-bearing mice were continuously given 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating (P) cells in the tumors, then treated with GPU-201, BSH-CD, or BSH. Immediately after reactor neutron beam or γ-ray irradiation, during which intratumor 10B concentrations were kept at levels similar to each other, cells from some tumors were isolated and incubated with a cytokinesis blocker. The responses of the Q and total (= P + Q) cell populations were assessed based on the frequency of micronuclei using immunofluorescence staining for BrdU. RESULTS: The 10B from BSH was washed away rapidly in all these tissues and the retention of 10B from BSH-CD and GPU-201 was similar except in blood where the 10B concentration from GPU-201 was higher for longer. GPU-201 showed a significantly stronger radio-sensitizing effect under neutron beam irradiation on both total and Q cell populations than any other 10B-carrier. CONCLUSION: A novel 10B-carrier conjugated with an integrin-binding RGD peptide (GPU-201) that sensitized tumor cells more markedly than conventional 10B-carriers may be a promising candidate for use in BNCT. However, its toxicity needs to be tested further.