Search tips
Search criteria

Results 1-25 (249)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
more »
author:("Chen, xiaoyan")
1.  18F-FDG and 18F-FLT-PET Imaging for Monitoring Everolimus Effect on Tumor-Growth in Neuroendocrine Tumors: Studies in Human Tumor Xenografts in Mice 
PLoS ONE  2014;9(3):e91387.
The mTOR inhibitor everolimus has shown promising results in some but not all neuroendocrine tumors. Therefore, early assessment of treatment response would be beneficial. In this study, we investigated the in vivo and in vitro treatment effect of everolimus in neuroendocrine tumors and evaluated the performance of 18F-FDG and the proliferation tracer 18F-FLT for treatment response assessment by PET imaging.
The effect of everolimus on the human carcinoid cell line H727 was examined in vitro with the MTT assay and in vivo on H727 xenograft tumors. The mice were scanned at baseline with 18F-FDG or 18F-FLT and then treated with either placebo or everolimus (5 mg/kg daily) for 10 days. PET/CT scans were repeated at day 1,3 and 10.
Everolimus showed significant inhibition of H727 cell proliferation in vitro at concentrations above 1 nM. In vivo tumor volumes measured relative to baseline were significantly lower in the everolimus group compared to the control group at day 3 (126±6% vs. 152±6%; p = 0.016), day 7 (164±7% vs. 226±13%; p<0.001) and at day 10 (194±10% vs. 281±18%; p<0.001). Uptake of 18F-FDG and 18F-FLT showed little differences between control and treatment groups, but individual mean uptake of 18F-FDG at day 3 correlated with tumor growth day 10 (r2 = 0.45; P = 0.034), 18F-FLT mean uptake at day 1 correlated with tumor growth day 7 (r2 = 0.63; P = 0.019) and at day 3 18F-FLT correlated with tumor growth day 7 (r2 = 0.87; P<0.001) and day 10 (r2 = 0.58; P = 0.027).
Everolimus was effective in vitro and in vivo in human xenografts lung carcinoid NETs and especially early 18F-FLT uptake predicted subsequent tumor growth. We suggest that 18F-FLT PET can be used for tailoring therapy for neuroendocrine tumor patients through early identification of responders and non-responders.
PMCID: PMC3953383  PMID: 24626055
2.  Reproducibility of Magnetic Resonance Perfusion Imaging 
PLoS ONE  2014;9(2):e89797.
Dynamic MR biomarkers (T2*-weighted or susceptibility-based and T1-weighted or relaxivity-enhanced) have been applied to assess tumor perfusion and its response to therapies. A significant challenge in the development of reliable biomarkers is a rigorous assessment and optimization of reproducibility. The purpose of this study was to determine the measurement reproducibility of T1-weighted dynamic contrast-enhanced (DCE)-MRI and T2*-weighted dynamic susceptibility contrast (DSC)-MRI with two contrast agents (CA) of different molecular weight (MW): gadopentetate (Gd-DTPA, 0.5 kDa) and Gadomelitol (P792, 6.5 kDa). Each contrast agent was tested with eight mice that had subcutaneous MDA-MB-231 breast xenograft tumors. Each mouse was imaged with a combined DSC-DCE protocol three times within one week to achieve measures of reproducibility. DSC-MRI results were evaluated with a contrast to noise ratio (CNR) efficiency threshold. There was a clear signal drop (>95% probability threshold) in the DSC of normal tissue, while signal changes were minimal or non-existent (<95% probability threshold) in tumors. Mean within-subject coefficient of variation (wCV) of relative blood volume (rBV) in normal tissue was 11.78% for Gd-DTPA and 6.64% for P792. The intra-class correlation coefficient (ICC) of rBV in normal tissue was 0.940 for Gd-DTPA and 0.978 for P792. The inter-subject correlation coefficient was 0.092. Calculated Ktrans from DCE-MRI showed comparable reproducibility (mean wCV, 5.13% for Gd-DTPA, 8.06% for P792). ICC of Ktrans showed high intra-subject reproducibility (ICC = 0.999/0.995) and inter-subject heterogeneity (ICC = 0.774). Histograms of Ktrans distributions for three measurements had high degrees of overlap (sum of difference of the normalized histograms <0.01). These results represent homogeneous intra-subject measurement and heterogeneous inter-subject character of biological population, suggesting that perfusion MRI could be an imaging biomarker to monitor or predict response of disease.
PMCID: PMC3934952  PMID: 24587040
3.  Positron Emission Tomography Imaging of Vascular Endothelial Growth Factor Receptor Expression with 61Cu-Labeled Lysine-Tagged VEGF121 
Molecular pharmaceutics  2012;9(12):3586-3594.
Overexpression of vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) indicates poor prognosis for cancer patients in a variety of clinical studies. Our goal is to develop a tracer for positron emission tomography (PET) imaging of VEGFR expression using recombinant human VEGF121 with three lysine residues fused to the N-terminus (denoted as K3-VEGF121), which can facilitate radiolabeling without affecting its VEGFR binding affinity. K3-VEGF121 was conjugated with 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and labeled with 61Cu (t1/2: 3.3 h; 62% β+). The IC50 value of NOTA-K3-VEGF121 for VEGFR-2 was comparable to K3-VEGF121 (1.50 and 0.65 nM, respectively) based on cell binding assay. 61Cu labeling was achieved with good yield (55 ± 10 %) and specific activity (4.2 GBq/mg). Serial PET imaging showed that the 4T1 tumor uptake of 61Cu-NOTA-K3-VEGF121 was 3.4 ± 0.5, 4.9 ± 1.0, 5.2 ± 1.0, and 4.8 ± 0.8 %ID/g (n = 4) at 0.5, 2, 4, and 8 h post-injection respectively, which was consistent with biodistribution data measured by gamma counting. Blocking experiments and ex vivo histology confirmed VEGFR specificity of 61Cu-NOTA-K3-VEGF121. Extrapolated human dosimetry calculation showed that liver was the organ with the highest radiation dose. The use of 61Cu as the radiolabel is desirable for small proteins like K3-VEGF121, which has much higher β+ branching ratio than the commonly used 64Cu (62% vs. 17%) thereby offering stronger signal intensity and lower tracer dose for PET imaging.
PMCID: PMC3619014  PMID: 23137334
Vascular endothelial growth factor (VEGF); VEGF receptor (VEGFR); 61Cu; Positron emission tomography (PET); Tumor angiogenesis; Molecular imaging
4.  Myocardial Defect Detection Using PET-CT: Phantom Studies 
PLoS ONE  2014;9(2):e88200.
It is expected that both noise and activity distribution can have impact on the detectability of a myocardial defect in a cardiac PET study. In this work, we performed phantom studies to investigate the detectability of a defect in the myocardium for different noise levels and activity distributions. We evaluated the performance of three reconstruction schemes: Filtered Back-Projection (FBP), Ordinary Poisson Ordered Subset Expectation Maximization (OP–OSEM), and Point Spread Function corrected OSEM (PSF–OSEM). We used the Channelized Hotelling Observer (CHO) for the task of myocardial defect detection. We found that the detectability of a myocardial defect is almost entirely dependent on the noise level and the contrast between the defect and its surroundings.
PMCID: PMC3914931  PMID: 24505429
5.  Use of Positron Emission Tomography for Real-Time Imaging of Biodistribution of Green Tea Catechin 
PLoS ONE  2014;9(2):e85520.
The aim of this study was to achieve real-time imaging of the in vivo behavior of a green tea polyphenol, catechin, by positron emission tomography (PET). Positron-labeled 4″ -[11C]methyl-epigallocatechin gallate ([11C]Me-EGCG) was orally administered to rats, and its biodistribution was imaged for 60 min by using a small animal PET system. As the result, images of [11C]Me-EGCG passing through the stomach into the small intestines were observed; and a portion of it was quantitatively detected in the liver. On the other hand, intravenous injection of [11C]Me-EGCG resulted in a temporal accumulation of the labeled catechin in the liver, after which almost all of it was transferred to the small intestines within 60 min. In the present study, we succeeded in obtaining real-time imaging of the absorption and biodistribution of [11C]Me-EGCG with a PET system.
PMCID: PMC3911897  PMID: 24498262
6.  Mesenchymal stem cell-based cell engineering with multifunctional mesoporous silica nanoparticles for tumor delivery 
Biomaterials  2012;34(7):1772-1780.
Stem cell engineering, the manipulation and control of cells, harnesses tremendous potential for diagnosis and therapy of disease; however, it is still challenging to impart multifunctionalization onto stem cells to achieve both. Here we describe a mesenchymal stem cell (MSC)-based multifunctional platform to target orthotopic glioblastoma by integrating the tumor targeted delivery of mesenchymal stem cells and the multimodal imaging advantage of mesoporous silica nanoparticles (MSNs). Rapid cellular uptake, long retention time and stability of particles exemplify the potential that the combination of MSNs and MSCs has as a stem cell-based multifunctional platform. Using such a platform, we verified tumor-targeted delivery of MSCs by in vivo multimodal imaging in an orthotopic U87MG glioblastoma model, displaying higher tumor uptake than particles without MSCs. As a proof-of-concept, this MSC platform opens a new vision for multifunctional applications of cell products by combining the superiority of stem cells and nanoparticles for actively targeted delivery.
PMCID: PMC3538138  PMID: 23228423
Mesenchymal stem cells (MSCs); mesoporous silica nanoparticles (MSNs); cell engineering; multimodal imaging; targeted delivery
7.  Effects of Reusing Baseline Volumes of Interest by Applying (Non-)Rigid Image Registration on Positron Emission Tomography Response Assessments 
PLoS ONE  2014;9(1):e87167.
Reusing baseline volumes of interest (VOI) by applying non-rigid and to some extent (local) rigid image registration showed good test-retest variability similar to delineating VOI on both scans individually. The aim of the present study was to compare response assessments and classifications based on various types of image registration with those based on (semi)-automatic tumour delineation.
Baseline (n = 13), early (n = 12) and late (n = 9) response (after one and three cycles of treatment, respectively) whole body [18F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (PET/CT) scans were acquired in subjects with advanced gastrointestinal malignancies. Lesions were identified for early and late response scans. VOI were drawn independently on all scans using an adaptive 50% threshold method (A50). In addition, various types of (non-)rigid image registration were applied to PET and/or CT images, after which baseline VOI were projected onto response scans. Response was classified using PET Response Criteria in Solid Tumors for maximum standardized uptake value (SUVmax), average SUV (SUVmean), peak SUV (SUVpeak), metabolically active tumour volume (MATV), total lesion glycolysis (TLG) and the area under a cumulative SUV-volume histogram curve (AUC).
Non-rigid PET-based registration and non-rigid CT-based registration followed by non-rigid PET-based registration (CTPET) did not show differences in response classifications compared to A50 for SUVmax and SUVpeak,, however, differences were observed for MATV, SUVmean, TLG and AUC. For the latter, these registrations demonstrated a poorer performance for small lung lesions (<2.8 ml), whereas A50 showed a poorer performance when another area with high uptake was close to the target lesion. All methods were affected by lesions with very heterogeneous tracer uptake.
Non-rigid PET- and CTPET-based image registrations may be used to classify response based on SUVmax and SUVpeak. For other quantitative measures future studies should assess which method is valid for response evaluations by correlating with survival data.
PMCID: PMC3904976  PMID: 24489860
8.  Multimodality Imaging of Breast Cancer Experimental Lung Metastasis with Bioluminescence and a Monoclonal Antibody Dual-Labeled with 89Zr and IRDye 800CW 
Molecular pharmaceutics  2012;9(8):2339-2349.
Metastatic breast cancer is incurable. The goal of this study was to develop a positron emission tomography (PET)/near-infrared fluorescent (NIRF) probe for imaging of CD105 expression in breast cancer experimental lung metastasis. TRC105, a chimeric anti-CD105 antibody, was dual-labeled with a NIRF dye (IRDye 800CW) and 89Zr to yield 89Zr-Df-TRC105-800CW. Luciferase-transfected 4T1 murine breast cancer cells were injected intravenously into female mice to establish the tumor model. Bioluminescence imaging (BLI) was carried out to non-invasively monitor the lung tumor burden. PET imaging revealed that 4T1 lung tumor uptake of 89Zr-Df-TRC105-800CW was 8.7±1.4, 10.9±0.5, and 9.7±1.1 %ID/g at 4, 24, and 48 h post-injection (n = 4), with excellent tumor contrast. Biodistribution studies, blocking, control studies with 89Zr-Df-cetuximab-800CW, ex vivo BLI/PET/NIRF imaging, and histology all confirmed CD105 specificity of the tracer. Broad clinical potential of TRC105-based agents was shown in many tumor types, which also enabled early detection of small metastasis and intraoperative guidance for tumor removal.
PMCID: PMC3500677  PMID: 22784250
Breast cancer; lung metastasis; positron emission tomography (PET); near-infrared fluorescence (NIRF); tumor angiogenesis; CD105 (endoglin); 89Zr
A new series of organic-high ionic strength aqueous two-phase solvents systems was designed for separation of highly polar compounds by spiral high-speed counter-current chromatography. A total of 21 solvent systems composed of 1-butanol-ethanol-saturated ammonium sulfate-water at various volume ratios are arranged according to an increasing order of polarity. Selection of the two-phase solvent system for a single compound or a multiple sample mixture can be achieved by two steps of partition coefficient measurements using a graphic method. The capability of the method is demonstrated by optimization of partition coefficient for seven highly polar samples including tartrazine (K=0.77), tryptophan (K=1.00), methyl green (K= 0.93), tyrosine (0.81), metanephrine (K=0.89), tyramine (K=0.98), and normetanephrine (K=0.96). Three sulfonic acid components in D&C Green No. 8 were successfully separated by HSCCC using the graphic selection of the two-phase solvent system.
PMCID: PMC3586324  PMID: 23467197
Spiral high-speed counter-current chromatography; Organic-high ionic strength aqueous solvent system series; Graphic optimization of partition coefficient; Sulfonic acids; Catecholamines; Zwitter ions
10.  Visualization of Protease Activity In Vivo Using an Activatable Photo-Acoustic Imaging Probe Based on CuS Nanoparticles 
Theranostics  2014;4(2):134-141.
Herein, we for the first time report a novel activatable photoacoustic (PA) imaging nano-probe for in vivo detection of cancer-related matrix metalloproteinases (MMPs). A black hole quencher 3 (BHQ3) which absorbs red light is conjugated to near-infrared (NIR)-absorbing copper sulfide (CuS) nanoparticles via a MMP-cleavable peptide linker. The obtained CuS-peptide-BHQ3 (CPQ) nano-probe exhibits two distinctive absorption peaks at 630 nm and 930 nm. Inside the tumor microenviorment where MMPs present, the MMP-sensitive peptide would be cleaved, releasing BHQ3 from the CuS nanoparticles, the former of which as a small molecule is then rapidly cleared out from the tumor, whereas the latter of which as large nanoparticles would retain inside the tumor for a much longer period of time. As the result, the PA signal at 680 nm which is contributed by BHQ3 would be quickly diminished while that at 930 nm would be largely retained. The PA signal ratio of 680 nm / 930 nm could thus serve as an in vivo indicator of MMPs activity inside the tumor. Our work presents a novel strategy of in vivo sensing of MMPs based on PA imaging, which should offer remarkably improved detection depth compared with traditional optical imaging techniques.
PMCID: PMC3900798  PMID: 24465271
Peptide; Photoacoustic imaging; Enzyme cleavage; Copper sulfide; MMPs detection.
11.  Photosensitizer Loaded Nano-Graphene for Multimodality Imaging Guided Tumor Photodynamic Therapy 
Theranostics  2014;4(3):229-239.
Graphene, a 2-dimensional carbon nanomaterial, has attracted wide attention in biomedical applications, owing to its intrinsic physical and chemical properties. In this work, a photosensitizer molecule, 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-alpha (HPPH or Photochlor®), is loaded onto polyethylene glycol (PEG)-functionalized graphene oxide (GO) via supramolecular π-π stacking. The obtained GO-PEG-HPPH complex shows high HPPH loading efficiency. The in vivo distribution and delivery were tracked by fluorescence imaging as well as positron emission tomography (PET) after radiolabeling of HPPH with 64Cu. Compared with free HPPH, GO-PEG-HPPH offers dramatically improved photodynamic cancer cell killing efficacy due to the increased tumor delivery of HPPH. Our study identifies a role for graphene as a carrier of PDT agents to improve PDT efficacy and increase long-term survival following treatment.
PMCID: PMC3915087  PMID: 24505232
Graphene oxide; HPPH; photodynamic therapy; positron emission tomography; optical imaging.
12.  Highly Efficient Hierarchical Micelles Integrating Photothermal Therapy and Singlet Oxygen-Synergized Chemotherapy for Cancer Eradication 
Theranostics  2014;4(4):399-411.
It is highly desirable to develop theranostic nanoparticles for achieving cancer imaging with enhanced contrast and simultaneously multimodal synergistic therapy. Herein, we report a theranostic micelle system hierarchically assembling cyanine dye (indocyanine green) and chemotherapeutic compound (doxorubicin) (I/D-Micelles) as a novel theranostic platform with high drug loading, good stability and enhanced cellular uptake via clathrin-mediated endocytosis. I/D-Micelles exhibit the multiple functionalities including near-infrared fluorescence (NIRF), hyperthermia and intracellular singlet oxygen from indocyanine green, and simultaneous cytotoxicity from doxorubicin. Upon photoirradiation, I/D-Micelles can induce NIRF imaging, acute photothermal therapy via hyperthermia and simultaneous synergistic chemotherapy via singlet oxygen-triggered disruption of lysosomal membranes, eventually leading to enhanced NIRF imaging and superior tumor eradication without any re-growth. Our results suggest that the hierarchical micelles can act as a superior theranostic platform for cancer imaging and multimodal synergistic therapy.
PMCID: PMC3936292  PMID: 24578723
Hierarchical micelles; Photothermal therapy; Singlet oxygen; Synergistic therapy; Cancer eradication
13.  Longitudinal PET Imaging of Muscular Inflammation Using 18F-DPA-714 and 18F-Alfatide II and Differentiation with Tumors 
Theranostics  2014;4(5):546-555.
Aim: 18F-DPA-714 is a PET tracer that recognizes macrophage translocator protein (TSPO), and 18F-Alfatide II (18F-AlF-NOTA-E[PEG4-c(RGDfk)]2) is specific for integrin αvβ3. This study aims to apply these two tracers for longitudinal PET imaging of muscular inflammation, and evaluate the value of 18F-DPA-714 in differentiating inflammation from tumor.
Methods: RAW264.7 mouse macrophage cells were used for cell uptake analysis of 18F-DPA-714. A mouse hind limb muscular inflammation model was established by intramuscular injection of turpentine oil. For the inflammation model, PET imaging was performed at different days using 18F-DPA-714 and 18F-Alfatide II. The specificity of the imaging probes was tested by co- or pre-injection of PK11195 or unlabeled RGD (Arg-Gly-Asp) peptide. PET imaging using 18F-DPA-714 was performed in A549, HT29, U87MG, INS-1, and 4T1 xenograft models. Immunofluorescence staining was performed to evaluate infiltrated macrophages and angiogenesis in inflammation and/or tumors.
Results: Uptake of 18F-DPA-714 in RAW264.7 cells was 45.5% at 1 h after incubation, and could be blocked by PK11195. PET imaging showed increased 18F-DPA-714 and 18F-Alfatide II uptake at inflammatory muscles. Peak uptake of 18F-DPA-714 was seen on day 6 (4.02 ± 0.64 %ID/g), and peak uptake of 18F-Alfatide II was shown on day 12 (1.87 ± 0.35 %ID/g) at 1 h p.i.. Tracer uptakes could be inhibited by PK11195 for 18F-DPA-714 or cold RGD for 18F-Alfatide II. Moreover, macrophage depletion with liposomal clodronate also reduced the local accumulation of both tracers. A549, HT29, U87MG, INS-1, and 4T1 tumor uptakes of 18F-DPA-714 (0.46 ± 0.28, 0.91 ± 0.08, 1.69 ± 0.67, 1.13 ± 0.33, 1.22 ± 0.55 %ID/g at 1 h p.i., respectively) were significantly lower than inflammation uptake (All P < 0.05).
Conclusion: PET imaging using 18F-DPA-714 as a TSPO targeting tracer could evaluate the dynamics of macrophage activation and infiltration in different stages of inflammatory diseases. The concomitant longitudinal PET imaging with both 18F-DPA-714 and 18F-Alfatide II matched the causal relationship between macrophage infiltration and angiogenesis. Moreover, we found 18F-DPA-714 uptake in several types of tumors is significantly lower than that in inflammatory muscles, suggesting 18F-DPA-714 PET has the potential for better differentiation of tumor and non-tumor inflammation.
PMCID: PMC3966057  PMID: 24672585
18F-DPA-714; 18F-Alfatide II; positron emission tomography; inflammation; tumor; TSPO
14.  Ultrasound-Triggered Phase Transition Sensitive Magnetic Fluorescent Nanodroplets as a Multimodal Imaging Contrast Agent in Rat and Mouse Model 
PLoS ONE  2013;8(12):e85003.
Ultrasound-triggered phase transition sensitive nanodroplets with multimodal imaging functionality were prepared via premix Shirasu porous glass (SPG) membrane emulsification method. The nanodroplets with fluorescence dye DiR and SPIO nanoparticles (DiR-SPIO-NDs) had a polymer shell and a liquid perfluoropentane (PFP) core. The as-formed DiR-SPIO-NDs have a uniform size of 385±5.0 nm with PDI of 0.169±0.011. The TEM and microscopy imaging showed that the DiR-SPIO-NDs existed as core-shell spheres, and DiR and SPIO nanoparticles dispersed in the shell or core. The MTT and hemolysis studies demonstrated that the nanodroplets were biocompatible and safe. Moreover, the proposed nanodroplets exhibited significant ultrasound-triggered phase transition property under clinical diagnostic ultrasound irradiation due to the vaporization of PFP inside. Meanwhile, the high stability and R2 relaxivity of the DiR-SPIO-NDs suggested its applicability in MRI. The in vivo T2-weighted images of MRI and fluorescence images both showed that the image contrast in liver and spleen of rats and mice model were enhanced after the intravenous injection of DiR-SPIO-NDs. Furthermore, the ultrasound imaging (US) in mice tumor as well as MRI and fluorescence imaging in liver of rats and mice showed that the DiR-SPIO-NDs had long-lasting contrast ability in vivo. These in vitro and in vivo findings suggested that DiR-SPIO-NDs could potentially be a great MRI/US/fluorescence multimodal imaging contrast agent in the diagnosis of liver tissue diseases.
PMCID: PMC3877337  PMID: 24391983
15.  Imaging of an Inflammatory Injury in the Newborn Rat Brain with Photoacoustic Tomography 
PLoS ONE  2013;8(12):e83045.
The precise assessment of cerebral saturation changes during an inflammatory injury in the developing brain, such as seen in periventricular leukomalacia, is not well defined. This study investigated the impact of inflammation on locoregional cerebral oxygen saturation in a newborn rodent model using photoacoustic imaging.
1 mg/kg of lipopolysaccharide(LPS) diluted in saline or saline alone was injected under ultrasound guidance directly in the corpus callosum of P3 rat pups. Coronal photoacoustic images were carried out 24 h after LPS exposure. Locoregional oxygen saturation (SO2) and resting state connectivity were assessed in the cortex and the corpus callosum. Microvasculature was then evaluated on cryosection slices by lectin histochemistry.
Significant reduction of SO2 was found in the corpus callosum; reduced SO2 was also found in the cortex ipsilateral to the injection site. Seed-based functional connectivity analysis showed that bilateral connectivity was not affected by LPS exposure. Changes in locoregional oxygen saturation were accompanied by a significant reduction in the average length of microvessels in the left cortex but no differences were observed in the corpus callosum.
Inflammation in the developing brain induces marked reduction of locoregional oxygen saturation, predominantly in the white matter not explained by microvascular degeneration. The ability to examine regional saturation offers a new way to monitor injury and understand physiological disturbance non-invasively.
PMCID: PMC3873292  PMID: 24386140
16.  A Highly Robust, Recyclable Displacement Assay for Mercuric Ions in Aqueous Solutions and Living Cells 
ACS nano  2012;6(12):10999-11008.
We designed a recyclable Hg2+ probe based on Rhodamine B isothiocyanate (RBITC) - poly (ethylene glycol) (PEG)-co-modified gold nanoparticles (AuNPs) with excellent robustness, selectivity and sensitivity. Based on a rational design, only Hg2+ can displace RBITC from the AuNP surfaces, resulting in a remarkable enhancement of RBITC fluorescence initially quenched by AuNPs. To maintain stability and monodispersity of AuNPs in real samples, thiol-terminated PEG was employed to bind with the remaining active sites of AuNPs. Besides, this displacement assay can be regenerated by resupplying free RBITC into the AuNPs solutions that were already used for detecting Hg2+. Importantly, the detection limit of this assay for Hg2+ (2.3 nM) was lower than the maximum limits guided by the United States Environmental Protection Agency as well as that permitted by the World Health Organization. The efficiency of this probe was demonstrated in monitoring Hg2+ in complex samples such as river water and living cells.
PMCID: PMC3528810  PMID: 23121626
gold nanoparticles; sensitivity; selectivity; recyclable detection; Rhodamine B isothiocyanate
17.  Diffusion MRI and Novel Texture Analysis in Osteosarcoma Xenotransplants Predicts Response to Anti-Checkpoint Therapy 
PLoS ONE  2013;8(12):e82875.
Combinations of targeted drugs have been employed to treat sarcomas, however, response rates have not improved notably, therefore emphasizing the need for novel treatments. In addition, imaging approaches to assess therapeutic response is lacking, as currently measurable indices, such as volume and/or diameter, do not accurately correlate with changes in tumor biology. In this study, quantitative and profound analyses of magnetic resonance imaging (MRI) were developed to evaluate these as imaging biomarkers for MK1775 and Gem in an osteosarcoma xenotransplant model at early time-points following treatment. Notably, we showed that Gem and Gem+MK1775 groups had significantly inhibited tumor growth by day 4, which was presaged by elevations in mean ADC by 24 hours post treatment. Significant differences were also observed at later time points for the Gem+MK1775 combination and MK1775 therapy. ADC distribution and entropy (randomness of ADC values) were also elevated by 24 hours following therapy. Immunohistochemistry demonstrated that these treatment-related increases in ADC correlated with apoptosis and observed cell condensations (dense- and exploded bodies). These findings underline the role of ADC as a quantitative imaging biomarker for therapy-induced response and show promising clinical relevance in the sarcoma patient population.
PMCID: PMC3865096  PMID: 24358232
18.  Comparison of 18F-labeled CXCR4 antagonist peptides for PET imaging of CXCR4 expression 
CXCR4 is overexpressed on tumor cells from many types of human cancers. A high level of CXCR4 expression often correlates with poor prognosis, chemotherapy resistance, and metastasis. The development of CXCR4-specific radiotracers for positron emission tomography (PET) imaging will allow in vivo evaluation of receptor expression level for diagnosis or therapeutic evaluation.
Two new 18F-labeled radiotracers based on an Ac-TC14012 peptide, [18F]FP-Ac-TC14012 and [18F]FB-Ac-TC14012, were synthesized and characterized. The affinities of the 2-fluoropropionate (FP)-conjugated or 4-fluorobenzoate (FB)-conjugated peptides to CXCR4-transfected Chinese hamster ovarian (CHO) cells were evaluated in a competitive binding assay with [125I]CXCL12 radioligand. The cell uptake and retention of [18F]FP-labeled and [18F]FB-labeled peptides were measured. The tumor targetability and pharmacokinetics of these two tracers were also evaluated by microPET imaging and biodistribution studies.
The labeled peptides retained high binding affinity to CXCR4 and showed much higher uptake in CXCR4-positive CHO cells than in CXCR4-negative cells in vitro. The smaller and more hydrophilic [18F]FP prosthetic group resulted in higher affinity and lower nonspecific cell uptake compared to the [18F]FB-labeled peptide. Both radiotracers showed much higher accumulation in CXCR4-positive than CXCR4-negative tumor xenografts in mice and allowed clear visualization of CXCR4 expression by PET. Among the two, [18F]FP-Ac-TC14012 showed higher tumor uptake and better tumor-to-background contrast. Unlike their N-terminal 4-F-benzoate analogs, these two tracers had minimal blood retention, likely due to reduced red blood cell binding. Metabolic organs, such as the liver and kidney, also showed high uptake. When blocked with low-dose cold peptide (10 μg), the tumor uptake was significantly increased, most likely due to the increased concentration in blood circulation, as evidenced by decreased liver uptake.
These results demonstrate that the [18F]FP-labeled Ac-TC14012 peptide with high tumor uptake, low nonspecific binding, and good tumor-to-background contrast promises [18F]FP-Ac-TC14012 as a PET tracer for in vivo PET imaging of CXCR4 expression.
PMCID: PMC3863618  PMID: 23636490
CXCR4; PET imaging; CXCR4 antagonist peptides; 18F-labeling
19.  Longitudinal PET Imaging of Doxorubicin Induced Cell Death with 18F-Annexin V 
This study aims to apply longitudinal positron emission tomography (PET) imaging with 18F-Annexin V to visualize and evaluate cell death induced by doxorubicin in a human head and neck squamous cell cancer UM-SCC-22B tumor xenograft model.
In vitro toxicity of doxorubicin to UM-SCC-22B cells was determined by a colorimetric assay. Recombinant human Annexin V protein was expressed and purified. The protein was labeled with fluorescein isothiocyanate (FITC) for fluorescence staining and 18F for PET imaging. Established UM-SCC-22B tumors in nude mice were treated with two doses of doxorubicin (10 mg/kg each dose) with 1 day interval. Longitudinal 18F-Annexin V PET was performed at 6 h, 24 h, 3 days, and 7 days after the treatment started. Following PET imaging, direct tissue biodistribution study was performed to confirm the accuracy of PET quantification.
Two doses of doxorubicin effectively inhibited the growth of UM-SCC-22B tumors by inducing cell death including apoptosis. The cell death was clearly visualized by 18F-Annexin V PET. The peak tumor uptake, which was observed at day 3 after treatment started, was significantly higher than that in the untreated tumors (1.56 ± 0.23 vs. 0.89 ± 0.31 %ID/g, p < 0.05). Moreover, the tumor uptake could be blocked by co-injection of excess amount of unlabeled Annexin V protein. At day 7 after treatment, the tumor uptake of 18F-Annexin had returned to baseline level.
18F-Annexin V PET imaging is sensitive enough to allow visualization of doxorubicin induced cell death in UM-SCC-22B xenograft model. The longitudinal imaging with 18F-Annexin will be helpful to monitor early response to chemotherapeutic anti-cancer drugs.
PMCID: PMC3387344  PMID: 22392643
18F-Annexin V; doxorubicin; apoptosis; PET; chemotherapy
20.  Quantitative Analysis and Parametric Imaging of 18F-Labeled Monomeric and Dimeric RGD Peptides Using Compartment Model 
Non-invasive PET imaging with radiolabeled RGD peptides for αvβ3 integrin targeting has become an important tool for tumor diagnosis and treatment monitoring in both pre-clinical and clinical studies. To better understand the molecular process and tracer pharmacokinetics, we introduced kinetic modeling in the investigation of 18F-labeled RGD peptide monomer 18F-FP-c(RGDyK) (denoted as 18F-FPRGD) and dimer 18F-FP-PEG3-E[c(RGDyK)]2 (denoted as 18F-FPPRGD2).
MDA-MB-435 tumor-bearing mice underwent 60 min dynamic PET scans following the injection of either 18F-FPRGD or 18F-FPPRGD2. Blocking studies with pre-injection of a blocking mass dose were performed for both monomeric and dimeric RGD groups. 18F-FPRAD (RAD) was used as a negative control. Kinetic parameters (K1, k2, k3, k4) of a three-compartment model were fitted to the dynamic data to allow quantitative comparisons between the monomeric and dimeric RGD peptides.
Dimeric RGD peptide tracer showed significantly higher binding potential (BpND = k3/k4, 5.87 ± 0.31) than that of the monomeric analog (2.75 ± 0.48, p = 0.0022, n = 4/group). The BpND values showed a significantly greater ratio (dimer/monomer ~2.1) than the difference in %ID/g uptake measured from static images (dimer/monomer ~1.5, p = 0.0045). Significant decrease in BpND was found in the blocked groups compared with the unblocked ones (dimer p = 0.00024, monomer p = 0.005, n = 4/group). Similarly, the RAD control group showed the lowest BpND value among all the test groups, as the RAD peptide does not bind to integrin αvβ3. Volume of distribution (VT = K1/k2(1+k3/k4)) could be separated into non-specific (VND = K1/k2) and specific (VS = K1k3/(k2k4)) components. Specific distribution volume (VS) was the dominant component of VT in the unblocked groups and decreased in the blocked groups. Unblocked RGD dimer also showed higher VS than that of the monomer (dimer VS = 2.38 ± 0.15, monomer VS = 0.90 ± 0.17, p = 0.0013, n = 4/group), well correlated with BpND calculations. Little difference in VND was found among all groups. Moreover, parametric maps allowed quantitative analysis at voxel level and provided higher tumor-to-background contrast for BpND maps than the static images. Tumor heterogeneity in kinetic parameters was found in parametric images, which couldn’t be clearly identified in static intensity images.
The pharmacokinetics of both monomeric and dimeric RGD peptide tracers was compared, and the RGD dimers showed significantly higher binding affinity than the monomeric analogs. Kinetic parameters were demonstrated to be valuable for separating specific and non-specific binding and may allow more sensitive and detailed quantification than simple standard uptake value (SUV) analysis.
PMCID: PMC3401513  PMID: 22437879
Positron Emission Tomography; kinetic modeling; quantitative analysis; RGD peptide; Integrin
21.  Detection of Synchronous Cancers by Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography during Primary Staging Workup for Esophageal Squamous Cell Carcinoma in Taiwan 
PLoS ONE  2013;8(11):e82812.
The aim of this retrospective study was to investigate the ability of fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the detection of synchronous cancers during staging workup for esophageal squamous cell carcinoma.
Materials and Methods
We performed a retrospective chart review of 426 Taiwanese patients with esophageal cancer who received FDG-PET/CT during their primary staging workup between December 2006 and December 2011. We defined synchronous cancers as those occurring within 6 months of the FDG-PET/CT scan. All of the synchronous lesions were confirmed by histology or imaging follow-up. The study patients were followed for at least 18 months or were censored on the date of last follow-up.
Fifty patients were excluded from analysis because of the presence of distant metastases. Of the remaining 376 patients, 359 were diagnosed with squamous cell carcinoma (SCC). We identified 17 patients with synchronous cancers, and all of them had a diagnosis of SCC. Synchronous head and neck cancers were the most frequent (n=13, 76.4%), followed by gastrointestinal cancers (colon cancer, n=2; hepatocellular carcinoma, n=1), and renal cell carcinoma (n=1). FDG-PET/CT successfully detected 15 synchronous cancers (12 head and neck cancers, 2 colon cancers, and 1 renal cell carcinoma). In contrast, conventional workup detected only 9 synchronous cancers (7 head and neck cancers, 1 hepatocellular carcinoma and 1 renal cell carcinoma). The sensitivity of FDG-PET/CT and conventional workup in detecting synchronous cancers were 88.2% and 52.9% respectively.
The most frequent synchronous lesions in patients with esophageal SCC were head and neck cancers in Taiwan. Our data indicate that FDG-PET/CT is superior to conventional workup in the detection of synchronous tumors during primary staging for esophageal squamous cell carcinoma.
PMCID: PMC3843733  PMID: 24312435
22.  A Ketogenic Diet Increases Brown Adipose Tissue Mitochondrial Proteins and UCP1 Levels in Mice 
IUBMB life  2012;65(1):10.1002/iub.1102.
We evaluated the effects of feeding a ketogenic diet (KD) for a month on general physiology with emphasis on brown adipose tissue (BAT) in mice. KD did not reduce the caloric intake, or weight or lipid content of BAT. Relative epididymal fat pads were 40% greater in the mice fed the KD (P = 0.06) while leptin was lower (P < 0.05). Blood glucose levels were 30% lower while D-β-hydroxybutyrate levels were about 3.5-fold higher in the KD group. Plasma insulin and leptin levels in the KD group were about half of that of the mice fed NIH-31 pellets (chow group). Median mitochondrial size in the inter-scapular BAT (IBAT) of the KD group was about 60% greater, whereas the median lipid droplet size was about half of that in the chow group. Mitochondrial oxidative phosphorylation proteins were increased (1.5–3-fold) and the uncoupling protein 1 levels were increased by threefold in mice fed the KD. The levels of PPARγ, PGC-1α, and Sirt1 in KD group were 1.5–3-fold while level of Sirt3 was about half of that in the chow-fed group. IBAT cyclic AMP levels were 60% higher in the KD group and cAMP response element binding protein was 2.5-fold higher, suggesting increased sympathetic system activity. These results demonstrate that a KD can also increase BAT mitochondrial size and protein levels.
PMCID: PMC3821007  PMID: 23233333
adipose tissue; mitochondrial size; sympathetic activity; energy expenditure; obesity; blood ketones
23.  Ferritin Nanocages To Encapsulate and Deliver Photosensitizers for Efficient Photodynamic Therapy against Cancer 
ACS nano  2013;7(8):10.1021/nn402199g.
Photodynamic therapy is an emerging treatment modality that is under intensive preclinical and clinical investigations for many types of disease including cancer. Despite the promise, there is a lack of a reliable drug delivery vehicle that can transport photosensitizers (PSs) to tumors in a site-specific manner. Previous efforts have been focused on polymer- or liposome-based nanocarriers, which are usually associated with a suboptimal PS loading rate and a large particle size. We report herein that a RGD4C-modified ferritin (RFRT), a protein-based nanoparticle, can serve as a safe and efficient PS vehicle. Zinc hexadecafluorophthalocyanine (ZnF16Pc), a potent PS with a high 1O2 quantum yield but poor water solubility, can be encapsulated into RFRTs with a loading rate as high as ~60 wt % (i.e., 1.5 mg of ZnF16Pc can be loaded on 1 mg of RFRTs), which far exceeds those reported previously. Despite the high loading, the ZnF16Pc-loaded RFRTs (P-RFRTs) show an overall particle size of 18.6 ± 2.6 nm, which is significantly smaller than other PS–nanocarrier conjugates. When tested on U87MG subcutaneous tumor models, P-RFRTs showed a high tumor accumulation rate (tumor-to-normal tissue ratio of 26.82 ±4.07 at 24 h), a good tumor inhibition rate (83.64% on day 12), as well as minimal toxicity to the skin and other major organs. This technology can be extended to deliver other metal-containing PSs and holds great clinical translation potential.
PMCID: PMC3819164  PMID: 23829542
photodynamic therapy; photosensitizer; targeted delivery; ferritin; nanoparticle
24.  Synthesis of 2-Acyloxycyclohexylsulfonamides and Evaluation on Their Fungicidal Activity 
Eighteen N-substituted phenyl-2-acyloxycyclohexylsulfonamides (III) were designed and synthesized by the reaction of N-substituted phenyl-2-hydroxyl-cycloalkylsulfonamides (I, R1) with acyl chloride (II, R2) in dichloromethane under the catalysis of TMEDA and molecular sieve. High fungicidal active compound N-(2,4,5-trichlorophenyl)-2-(2-ethoxyacetoxy) cyclohexylsulfonamide (III-18) was screened out. Mycelia growth assay against the Botrytis cinerea exhibited that EC50 and EC80 of compound III-18 were 4.17 and 17.15 μg mL−1 respectively, which was better than the commercial fungicide procymidone (EC50 = 4.46 μg mL−1 and EC80 = 35.02 μg mL−1). For in vivo activity against B. cinerea in living leaf of cucumber, the control effect of compound III-18 was better than the fungicide cyprodinil. In addition, this new compound had broader fungicidal spectra than chlorothalonil.
PMCID: PMC3856078  PMID: 24240812
2-acyloxycycloalkylsulfonamides; Botrytis cinerea; anti-fungal spectra; structure-activity relationship
25.  Real-time monitoring of caspase cascade activation in living cells 
We introduce a simple, versatile and robust one-step technique that enables real-time imaging of multiple intracellular caspase activities in living cells without the need for complicated synthetic protocols. Conventional fluorogenic probes or recently reported activatable probes have been designed to target various proteases but are limited to extracellular molecules. Only a few have been applied to image intracellular proteases in living cells because most of these probes have limited cell-permeability. Our platform does not need complicated synthetic processes; instead it involves a straightforward peptide synthesis and a simple mixing step with a commercial transfection agent. The transfection agent efficiently delivered the highly quenched fluorogenic probes, comprised of distinctive pairs of dyes and quenchers, to the initiator caspase-8 and the effector caspase-3 in MDA-MB-435 cells, allowing dual-imaging of the activities of both caspases during the apoptotic process induced by TNF-related apoptosis induced ligand (TRAIL). With the combination of multiple fluorogenic probes, this simple platform can be applied to multiplexed imaging of selected intracellular proteases to study apoptotic processes in pathologies or for cell-based high throughput screening systems for drug discovery.
PMCID: PMC3462246  PMID: 22664474
caspase; activatable probe; fluorescence imaging; peptide; transfection agent

Results 1-25 (249)