Gene Expression and Early Radiation Response of Two Distinct Neuroblastoma Cell Lines

INTRODUCTION

Neuroblastoma is one of the most common childhood cancers with one of the lowest survival rates, accounting for 15% of childhood cancer mortality. Approximately half of children treated for high-risk neuroblastoma will relapse following remission, while another 15% of patients do not respond to initial treatment. External beam radiation is infrequently used for treatment of pediatric cancer such as neuroblastoma, typically reserved for palliative care in patients with aggressive metastatic disease who fail to respond to alternative treatments. Understanding effects of radiation on neuroblastoma cells could improve efficacy of this final means of therapy to decrease tumor burden and stabilize the disease.

METHODS

In this study, we found that two microRNAs with opposite functions were expressed in two neuroblastoma cell lines with marked differences in radiosensitivity. Clonogenic assays were used to evaluate the radiation responses for these 2 cell lines, designated SK-N-AS and SK-N-DZ; cells were then irradiated at doses that cause 90% cell killing based on clonogenic assay and their RNA isolated and subjected to microarray analysis. In addition, cells were transfected with pre-miRNA constructs that led to overexpression of microRNAs miR-34a and miR-1228 to determine possible microRNA regulation of radiation response.

RESULTS

Statistically significant differences were detected for expression of several thousand genes when the 2 cell lines were compared with each other. In comparison, radiation exposure resulted in only minor gene expression differences of less than 2-fold at the 1 h postirradiation timepoint in both cell lines. Overexpression of miR-34a and miR-1228 in either cell line did not alter this outcome.

DISCUSSION

While these two neuroblastoma cell lines are phenotypically diverse and gene expression differences between them are extensive, we observed that the regulation of gene expression in both cell lines is in a stable equilibrium at early timepoints after exposure to ionizing radiation.

PERIOD 2 Regulates Low Dose Radioprotection via PER2/pGSK3β/β-Catenin/Per2 Loop

During evolution, humans are acclimatized to the stresses of natural radiation and circadian rhythmicity. Radiosensitivity of mammalian cells varies in the circadian period and adaptive radioprotection can be induced by pre-exposure to low-level radiation (LDR). It is unclear, however, if clock proteins participate in signaling LDR radioprotection. Herein, we demonstrate that radiosensitivity is increased in mice with the deficient Period 2 gene (Per2^def) due to impaired DNA repair and mitochondrial function in progenitor bone marrow hematopoietic stem cells and monocytes. Per2 induction and radioprotection are also identified in LDR-treated Per2^wt mouse cells and in human skin (HK18) and breast (MCF-10A) epithelial cells. LDR-boosted PER2 interacts with pGSK3β(S9) which activates β-catenin and the LEF/TCF mediated gene transcription including Per2 and genes involved in DNA repair and mitochondrial functions. This study demonstrates that PER2 plays an active role in LDR adaptive radioprotection via PER2/pGSK3β/β-catenin/Per2 loop, a potential target for protecting normal cells from radiation injury.

A reliable workflow for improving nanoscale X-ray fluorescence tomographic analysis on nanoparticle-treated HeLa cells

Scanning X-ray fluorescence (XRF) tomography provides powerful characterization capabilities in evaluating elemental distribution and differentiating their inter- and intra-cellular interactions in a three-dimensional (3D) space. Scanning XRF tomography encounters practical challenges from the sample itself, where the range of rotation angles is limited by geometric constraints, involving sample substrates or nearby features either blocking or converging into the field of view. This study aims to develop a reliable and efficient workflow that can (1) expand the experimental window for nanoscale tomographic analysis of local areas of interest within a laterally extended specimen, and (2) bridge 3D analysis at micrometer and nanoscales on the same specimen. We demonstrate the workflow using a specimen of HeLa cells exposed to iron oxide core and titanium dioxide shell (Fe3O4/TiO2) nanocomposites. The workflow utilizes iterative and multiscale XRF data collection with intermediate sample processing by focused ion beam (FIB) sample preparation between measurements at different length scales. Initial assessment combined with precise sample manipulation via FIB allows direct removal of sample regions that are obstacles to both incident X-ray beam and outgoing XRF signals, which considerably improves the subsequent nanoscale tomography analysis. This multiscale analysis workflow has advanced bio-nanotechnology studies by providing deep insights into the interaction between nanocomposites and single cells at a subcellular level as well as statistical assessments from measuring a population of cells.

Examining potential confounding factors in gene expression analysis of human saliva and identifying potential housekeeping genes

Isolation of RNA from whole saliva, a non-invasive and easily accessible biofluid that is an attractive alternative to blood for high-throughput biodosimetry of radiological/nuclear victims might be of clinical significance for prediction and diagnosis of disease. In a previous analysis of 12 human samples we identified two challenges to measuring gene expression from total RNA: (1) the fraction of human RNA in whole saliva was low and (2) the bacterial contamination was overwhelming. To overcome these challenges, we performed selective cDNA synthesis for human RNA species only by employing poly(A)+-tail primers followed by qRT-PCR. In the current study, this approach was independently validated on 91 samples from 61 healthy donors. Additionally, we used the ratio of human to bacterial RNA to adjust the input RNA to include equal amounts of human RNA across all samples before cDNA synthesis, which then ensured comparable analysis using the same base human input material. Furthermore, we examined relative levels of ten known housekeeping genes, and assessed inter- and intra-individual differences in 61 salivary RNA isolates, while considering effects of demographical factors (e.g. sex, age), epidemiological factors comprising social habits (e.g. alcohol, cigarette consumption), oral hygiene (e.g. flossing, mouthwash), previous radiological diagnostic procedures (e.g. number of CT-scans) and saliva collection time (circadian periodic). Total human RNA amounts appeared significantly associated with age only (P ≤ 0.02). None of the chosen housekeeping genes showed significant circadian periodicity and either did not associate or were weakly associated with the 24 confounders examined, with one exception, 60% of genes were altered by mouthwash. ATP6, ACTB and B2M represented genes with the highest mean baseline expression (Ct-values ≤ 30) and were detected in all samples. Combining these housekeeping genes for normalization purposes did not decrease inter-individual variance, but increased the robustness. In summary, our work addresses critical confounders and provides important information for the successful examination of gene expression in human whole saliva.

Paramagnetic Mn8Fe4-co-Polystyrene Nanobeads as a Potential T1-T2 Multimodal Magnetic Resonance Imaging Contrast Agent with In Vivo Studies

In developing a cluster-nanocarrier design, as a magnetic resonance imaging contrast agent, we have investigated the enhanced relaxivity of a manganese and iron-oxo cluster grafted within a porous polystyrene nanobead with increased relaxivity due to a higher surface area. The synthesis of the cluster-nanocarrier for the cluster Mn8Fe4O12(O2CC6H4CH═CH2)16(H2O)4, cross-linked with polystyrene (the nanocarrier), under miniemulsion conditions is described. By including a branched hydrophobe, iso-octane, the resulting nanobeads are porous and ∼70 nm in diameter. The increased surface area of the nanobeads compared to nonporous nanobeads leads to an enhancement in relaxivity; r1 increases from 3.8 to 5.2 ± 0.1 mM-1 s-1, and r2 increases from 11.9 to 50.1 ± 4.8 mM-1 s-1, at 9.4 teslas, strengthening the potential for T1 and T2 imaging. Several metrics were used to assess stability, and the porosity produced no reduction in metal stability. Synchrotron X-ray fluorescence microscopy was used to demonstrate that the nanobeads remain intact in vivo. In depth, physicochemical characteristics were determined, including extensive pharmacokinetics, in vivo imaging, and systemic biodistribution analysis.

A combinatorial approach of a polypharmacological adjuvant 2-deoxy-D-glucose with low dose radiation therapy to quell the cytokine storm in COVID-19 management

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pandemic disease and is the major cause of deaths worldwide. The clinical complexities (inflammation, cytokine storm, and multi-organ dysfunction) associated with COVID-19 poses constraints to effective management of critically ill COVID-19 patients. Low dose radiation therapy (LDRT) has been evaluated as a potential therapeutic modality for COVID-19 pneumonia. However, due to heterogeneity in disease manifestation and inter-individual variations, effective planning for LDRT is limited for this large-scale event. 2-deoxy-D-glucose (2-DG) has emerged as a polypharmacological agent for COVID-19 treatment due to its effects on the glycolytic pathway, anti-inflammatory action, and interaction with viral proteins. We suggest that 2-DG will be a potential adjuvant to enhance the efficacy of LDRT in the treatment of COVID-19 pneumonia. Withal, azido analog of 2-DG, 2-azido-2-DG can produce rapid catastrophic oxidative stress and quell the cytokine storm in critically ill COVID-19 patients.

Dual blockade of CD47 and HER2 eliminates radioresistant breast cancer cells

Although the efficacy of cancer radiotherapy (RT) can be enhanced by targeted immunotherapy, the immunosuppressive factors induced by radiation on tumor cells remain to be identified. Here, we report that CD47-mediated anti-phagocytosis is concurrently upregulated with HER2 in radioresistant breast cancer (BC) cells and RT-treated mouse syngeneic BC. Co-expression of both receptors is more frequently detected in recurrent BC patients with poor prognosis. CD47 is upregulated preferentially in HER2-expressing cells, and blocking CD47 or HER2 reduces both receptors with diminished clonogenicity and augmented phagocytosis. CRISPR-mediated CD47 and HER2 dual knockouts not only inhibit clonogenicity but also enhance macrophage-mediated attack. Dual antibody of both receptors synergizes with RT in control of syngeneic mouse breast tumor. These results provide the evidence that aggressive behavior of radioresistant BC is caused by CD47-mediated anti-phagocytosis conjugated with HER2-prompted proliferation. Dual blockade of CD47 and HER2 is suggested to eliminate resistant cancer cells in BC radiotherapy.

The Transition from Metal-Based to Metal-Free Contrast Agents for T1 Magnetic Resonance Imaging Enhancement

Magnetic resonance imaging (MRI) has received significant attention as the noninvasive diagnostic technique for complex diseases. Image-guided therapeutic strategy for diseases such as cancer has also been at the front line of biomedical research, thanks to the innovative MRI, enhanced by the prior delivery of contrast agents (CAs) into patients' bodies through injection. These CAs have contributed a great deal to the clinical utility of MRI but have been based on metal-containing compounds such as gadolinium, manganese, and iron oxide. Some of these CAs have led to cytotoxicities such as the incurable Nephrogenic Systemic Fibrosis (NSF), resulting in their removal from the market. On the other hand, CAs based on organic nitroxide radicals, by virtue of their structural composition, are metal free and without the aforementioned drawbacks. They also have improved biocompatibility, ease of functionalization, and long blood circulation times, and have been proven to offer tissue contrast enhancement with longitudinal relaxivities comparable with those for the metal-containing CAs. Thus, this Review highlights the recent progress in metal-based CAs and their shortcomings. In addition, the remarkable goals achieved by the organic nitroxide radical CAs in the enhancement of MR images have also been discussed extensively. The focal point of this Review is to emphasize or demonstrate the crucial need for transition into the use of organic nitroxide radicals-metal-free CAs-as against the metal-containing CAs, with the aim of achieving safer application of MRI for early disease diagnosis and image-guided therapy.

Radiation databases and archives - examples and comparisons

Studies of ionizing radiation effects through the archiving of data began with standardizing medical treatments in the early 1900s shortly after the discovery of X-rays. Once the breadth of the delayed effects of ionizing radiation was recognized, the need for long-term follow up became apparent. There are now many human archives of data from nuclear disasters and accidents, occupational exposures, and medical procedures. Planned animal irradiation experiments began around the time of the Cold War and included a variety of doses, fractions, dose rates, and types of ionizing radiation. The goal of most of these studies was to supplement information coming from human data through carefully planned experimental conditions and immediate and uninterrupted data collection. This review aims to highlight major archives and databases that have shaped the field of radiation biology and provide a broad range of the types of datasets currently available. By preserving all of these data and tissue sets, radiation biologists can combine databases and conduct large-scale analyses of detailed existing data and perform new assays with cutting edge scientific approaches.

Reflections on Basic Science Studies Involving Low Doses of Ionizing Radiation

Investigation of health effects of low doses of radiation as a field of study has been riddled with difficulties since its inception. In this document we will use 100 mGy as the cutoff upper limit for low-dose radiation, borrowing this definition from the U.S. Department of Energy, although other agencies and researchers sometimes include up to five-fold higher doses under the same title. Difficulties in this area of research are most often ascribed to the fact that effects of low doses of radiation are subtle and difficult to distinguish from the plethora of other low-grade stresses. Thus, for example, most epidemiological studies include hundreds of thousands of samples and generate risk estimates that are statistically meaningful only when they are considered on a scale of hundreds or thousands of people. A logical approach to remedy the situation for low-dose research was to conduct well-controlled animal studies with hundreds of animals; nevertheless, even after many such studies were completed, our understanding of the biological basis for risk from low-dose radiation exposure is still not conclusive. In this paper we argue that the problem lies in the fact that our approach to animal studies is not comprehensive but conceptually binary. While some researchers apply epidemiological models to animal data, others look into molecular and cellular biology only. Very few studies are conducted to bridge this gap and consider how a realistic model of DNA damage could be integrated into a realistic model of radiation carcinogenesis.

The influence of changing dose rate patterns from inhaled beta-gamma emitting radionuclide on lung cancer

Purpose:

Dose and dose rate are both appropriate for estimating risk from internally deposited radioactive materials. We investigated the role of dose rate on lung cancer induction in Beagle dogs following a single inhalation of strontium-90 (⁹⁰Sr), cerium-144 (¹⁴⁴Ce), yttrium-91 (⁹¹Y), or yttrium-90 (⁹⁰Y). As retention of the radionuclide is dependent on biological clearance and physical half-life a representative quantity to describe this complex changing dose rate is needed.

Materials and methods:

Data were obtained from Beagle dog experiments from the Inhalation Toxicology Research Institute. The authors selected the dose rate at the effective half-life of each radionuclide (DR_ef).

Results:

Dogs exposed to DRef (1–100 Gy/day) died within the first year after exposure from acute lung disease. Dogs exposed at lower DRef (0.1–10 Gy/day) died of lung cancer. As DR_ef decreased further (<0.1 Gy/day ⁹⁰Sr, <0.5 Gy/day ¹⁴⁴Ce, <0.9 Gy/day ⁹¹Y, <8 Gy/day ⁹⁰Y), survival and lung cancer frequency were not significantly different from control dogs.

Conclusion:

Radiation exposures resulting from inhalation of beta-gamma emitting radionuclides that decay at different rates based on their effective half-life, leading to different rates of decrease in dose rate and cumulative dose, is less effective in causing cancer than acute low linear energy transfer exposures of the lung.

Structural and elemental changes in glioblastoma cells in situ: complementary imaging with high resolution visible light- and X-ray microscopy

The glioblastoma (GBM) is characterized by a short median survival and an almost 100% tumor related mortality. GBM cells exhibit highly invasive behavior whose mechanisms are not yet fully understood. The present study explores application of X-ray and visible light microscopy to display the elemental and structural images of cells from 3 patient derived GMB samples and an established GMB cell line. Slight differences in elemental concentrations, in actin cytoskeleton organization and cell morphology were noted between all cells types by X-ray fluorescence and full field soft X-ray microscopy, as well as the Structured Illumination Super-resolution Microscope (SIM). Different sample preparation approaches were used to match each imaging technique. While preparation for SIM included cell fixation and staining, intact frozen hydrated cells were used for the trace element imaging by hard X-ray fluorescence and exploration of the structural features by soft X-ray absorption tomography. Each technique documented differences between samples with regard to morphology and elemental composition and underscored the importance of use of multiple patient derived samples for detailed GBM study.

Abstract LB-184: Core circadian clock component, PERIOD2, regulates adaptive radioprotection via PER2-β-Catenin controlled mitochondrial bioenergetics

Circadian clocks are intimately involved in the homeostatic maintenance of metabolic and physiological processes that may have increasingly important roles to enhance bone marrow transplantation success in cancer patients; to protect normal tissue surrounding tumors from the harmful effects of radio/chemotherapy; and to enhance the quality of diet and sleep for astronauts during space exploration. Herein, we report that expression of PERIOD2 (PER2; a core circadian clock component and “the inherent driver” of radioprotection) is required for adaptive protection against environmental radiation stress. PER2 expression is induced by exposure to low dose radiation (LDR; 10cGy) and siRNA blockade of PER2 ablates LDR-induced adaptive radioprotection. In addition, melatonin (N-acetyl-5-methoxytryptamine), a natural anti-oxidant and hypothalamic circadian synchronizer, stimulates PER2 expression and confers mice radioprotection through weight maintenance and increased survival. LDR-induced PER2 transcription is regulated by NF-κB and β-catenin and is released from phospho-glycogen synthase kinase-3ß (p-GSK3ß) in the WNT/β-catenin pathway. Unbound β-catenin interacts with the TCF/LEF domain on the Per2 promoter to promote feed-forward PER2-pGSK3β complex formation. Mitochondrial bioenergetics measured by oxygen consumption and ATP generation was attenuated in bone marrow isolated from PER2 mutant (Per2m/m) mice. Furthermore, RNA-seq profiling of bone marrow-derive progenitor hematopoietic stem cells (BM-pHSCs; Lin-/Sca1+/cKit+; LSK) cells isolated form LDR-treated wild-type (WT) versus Per2m/m mice showed a cluster of genes involved in mitochondrial bioenergetics and DNA repair capacity. These results demonstrate that a core circadian regulator plays an indispensable role in defending mammalian cells against environmental genotoxic stress through the PER2/β-catenin pathway, a potential therapeutic target to enhance cell survival under radiation.

Citation Format: Aris Alexandrou, Ming Fan, Shuaib Juma, Julian Perks, Andrew Vaughan, Clifford Tepper, Loning Fu, Gayle Woloschak, David Grdina. Core circadian clock component, PERIOD2, regulates adaptive radioprotection via PER2-β-Catenin controlled mitochondrial bioenergetics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-184.

Peritumoral cuffing by T-cell tumor-infiltrating lymphocytes distinguishes HPV-related oropharyngeal squamous cell carcinoma from oral cavity squamous cell carcinoma

BACKGROUND

It is unclear why human papillomavirus (HPV)-related head and neck squamous cell carcinoma (HNSCC) has improved clinical behavior compared to HPV-negative HNSCC. We sought to better characterize the immune microenvironment of tongue cancers by examining the CD3 and CD8 TIL pattern in HPV-positive and HPV-negative tumors.

METHODS

Histologic sections from 40 oral tongue and oropharyngeal cases were analyzed (n=21 HPV DNA-positive, n=19 HPV DNA-negative). CD3 and CD8 T-cell immunostaining were performed on whole-slide sections to quantify tumor-infiltrating lymphocyte (TIL) density and assess its morphology.

RESULTS

A subset of cases (HPV-positive) displayed a unique TIL pattern consisting of circumferential peritumoral population T cells, which was absent in the HPV-negative cases. The presence of peritumoral cuffing was strongly predictive of improved recurrence-free survival compared to cases that lacked this morphologic pattern of immune infiltrate. Four HPV-positive cases lacked the pattern, including two cases with disease recurrence.

CONCLUSIONS

For the first time, we show an architectural pattern of immune infiltrate in HNSCC is seen exclusively in HPV-positive patients with improved recurrence-free survival and suggests an organized host immunological response contributes to disease control.

Preserving elemental content in adherent mammalian cells for analysis by synchrotron-based x-ray fluorescence microscopy

Trace metals play important roles in biological function, and x-ray fluorescence microscopy (XFM) provides a way to quantitatively image their distribution within cells. The faithfulness of these measurements is dependent on proper sample preparation. Using mouse embryonic fibroblast NIH/3T3 cells as an example, we compare various approaches to the preparation of adherent mammalian cells for XFM imaging under ambient temperature. Direct side-by-side comparison shows that plunge-freezing-based cryoimmobilization provides more faithful preservation than conventional chemical fixation for most biologically important elements including P, S, Cl, K, Fe, Cu, Zn and possibly Ca in adherent mammalian cells. Although cells rinsed with fresh media had a great deal of extracellular background signal for Cl and Ca, this approach maintained cells at the best possible physiological status before rapid freezing and it does not interfere with XFM analysis of other elements. If chemical fixation has to be chosen, the combination of 3% paraformaldehyde and 1.5 % glutaraldehyde preserves S, Fe, Cu and Zn better than either fixative alone. When chemically fixed cells were subjected to a variety of dehydration processes, air drying was proved to be more suitable than other drying methods such as graded ethanol dehydration and freeze drying. This first detailed comparison for x-ray fluorescence microscopy shows how detailed quantitative conclusions can be affected by the choice of cell preparation method.

CDK1 Enhances Mitochondrial Bioenergetics for Radiation-Induced DNA Repair

Nuclear DNA repair capacity is a critical determinant of cell fate under genotoxic stress conditions. DNA repair is a well-defined energy-consuming process. However, it is unclear how DNA repair is fueled and whether mitochondrial energy production contributes to nuclear DNA repair. Here, we report a dynamic enhancement of oxygen consumption and mitochondrial ATP generation in irradiated normal cells, paralleled with increased mitochondrial relocation of the cell-cycle kinase CDK1 and nuclear DNA repair. The basal and radiation-induced mitochondrial ATP generation is reduced significantly in cells harboring CDK1 phosphorylation-deficient mutant complex I subunits. Similarly, mitochondrial ATP generation and nuclear DNA repair are also compromised severely in cells harboring mitochondrially targeted, kinase-deficient CDK1. These results demonstrate a mechanism governing the communication between mitochondria and the nucleus by which CDK1 boosts mitochondrial bioenergetics to meet the increased cellular fuel demand for DNA repair and cell survival under genotoxic stress conditions.

Hyperthermia and radiation therapy for locally advanced or recurrent breast cancer

INTRODUCTION

This study aims to report the outcome and toxicity of combined hyperthermia (HT) and radiation therapy (RT) in treatment of locally advanced or loco-regionally recurrent breast cancer.

PATIENTS AND METHODS

Patients treated with HT and RT from January 1991 to December 2007 were reviewed. RT doses for previously irradiated patients were > 40 Gy and for RT naïve patients > 60 Gy, at 1.8-2 Gy/day. HT was planned for 2 sessions/week, immediately after RT, for a minimum of 20 min and for > 4 sessions. Superficial or interstitial applicators were used with temperature measured by superficial or interstitial thermistors based on target thickness. HT treatment was assessed by thermal equivalent dose (TED), > 42.5 °C and > 43 °C. Endpoints included treatment response, lack of local progression (local control), and survival.

RESULTS

127 patients received HT and RT to 167 sites. These included the intact breast (24.4%), chest wall/skin (67.7%), and breast/chest wall and nodes (7.9%). At a median follow-up of 13 months (mean 30 ± 38), improved overall survival was significantly associated with increasing RT dose (p < 0.0001), median TED 42.5 °C ≥ 200 min (p = 0.003), and local control (p = 0.0002). Local control at last follow-up was seen in 55.1% of patients. Complete response was significantly associated with median TED 42.5 °C ≥ 200 min (p = 0.002) and median TED 43 °C ≥ 100 min (p = 0.03).

CONCLUSION

HT and RT are effective for locally advanced or recurrent breast cancer in patients that have been historically difficult to treat by RT alone. Over 50% of patients achieved control of locoregional disease. Overall survival was improved with local control.

CDK4-mediated MnSOD activation and mitochondrial homeostasis in radioadaptive protection

Mammalian cells are able to sense environmental oxidative and genotoxic conditions such as the environmental low-dose ionizing radiation (LDIR) present naturally on the earth's surface. The stressed cells then can induce a so-called radioadaptive response with an enhanced cellular homeostasis and repair capacity against subsequent similar genotoxic conditions such as a high dose radiation. Manganese superoxide dismutase (MnSOD), a primary mitochondrial antioxidant in mammals, has long been known to play a crucial role in radioadaptive protection by detoxifying O2(•-) generated by mitochondrial oxidative phosphorylation. In contrast to the well-studied mechanisms of SOD2 gene regulation, the mechanisms underlying posttranslational regulation of MnSOD for radioprotection remain to be defined. Herein, we demonstrate that cyclin D1/cyclin-dependent kinase 4 (CDK4) serves as the messenger to deliver the stress signal to mitochondria to boost mitochondrial homeostasis in human skin keratinocytes under LDIR-adaptive radioprotection. Cyclin D1/CDK4 relocates to mitochondria at the same time as MnSOD enzymatic activation peaks without significant changes in total MnSOD protein level. The mitochondrial-localized CDK4 directly phosphorylates MnSOD at serine-106 (S106), causing enhanced MnSOD enzymatic activity and mitochondrial respiration. Expression of mitochondria-targeted dominant negative CDK4 or the MnSOD-S106 mutant reverses LDIR-induced mitochondrial enhancement and adaptive protection. The CDK4-mediated MnSOD activation and mitochondrial metabolism boost are also detected in skin tissues of mice receiving in vivo whole-body LDIR. These results demonstrate a unique CDK4-mediated mitochondrial communication that allows cells to sense environmental genotoxic stress and boost mitochondrial homeostasis by enhancing phosphorylation and activation of MnSOD.

Abstract 4913: Development of Fe3O4@TiO2 core-shell nanocomposites as radiosensitizers

Purpose: To test in vivo, in a rabbit VX2 liver cancer model, a nanocomposite made with Fe3O4 core and TiO2 shell as a possible radiosensitization agent.

Methods: This study was approved by the institutional ACUC. Rabbits were implanted in liver with pairs of VX2 tumors distantly enough to allow irradiation of only one of the two tumors. The tumors were allowed to grow until clearly detectable by magnetic resonance imaging, followed by Computed Tomography (CT) simulation to identify and contour the tumors. Each rabbit was anesthetized, and immobilized in supine position. Isocenter was placed during the CT simulation and the rabbit was tattooed. After the CT, each rabbit was injected with nanoparticles and put under observation until recovery. The core-shell nanoparticles were surface covered with glucose (glut-NPs) and delivered intravenously to 6 rabbits. A radiation oncologist contoured the target volumes. The gross target volume included a hepatic tumor in one lobe; 1 - 3 mm expansion was done to create the clinical target volume and another 1-2 mm expansion to create the planning target volume (PTV). The control hepatic tumor was contoured and the treatment plan objective was to deliver more than 95% of the prescribed dose to the PTV while sparing the control tumor. A certified radiation physicist created the treatment plan. Dose Volume Histograms were created and the radiation oncologist approved the plan. Irradiation usually utilized 2 - 3 beams, delivering 2 Gy as a single fraction using Linear Accelerator. All 6 rabbits treated with nanoparticles the day before (14-18h previously) and 3 radiation-only (not glut-NPs treated) animals were irradiated so that only one of the tumors received radiation. The animals were terminated 3 days after irradiation and the tumors were harvested. Several view-fields with at 3-10 x 103 cells were automatically scored using the NanoZoomer and percentage of Ki67 positive cells, as a marker of proliferation was determined in each tumor. TUNEL assay was done as well.

Results: In each rabbit the larger tumor of the pair was irradiated. In no-NP treated animals that led to the fact that irradiated tumors at 3 days after irradiation generally still had greater number of proliferating cells than the non-irradiated tumor sections. Conversely, in glut-NPs treated rabbits, irradiation led to a decrease of Ki-67 positive cells compared to the paired non-irradiated glut-NPs treated tumors. Three-day time-point was better suited for evaluation of tumor proliferation changes. TUNEL analysis showed higher apoptotic cell numbers in glut-NPs treated tumors (p=0.049). Combination of radiation with glut-NP treatment showed only a mild trend for increased apoptosis compared to non-irradiated glut-NPs treated tumors, this trend was not statistically significant (p=0.53).

Conclusion: These data suggest that the glut-NPs show a considerable promise for radiosensitization.

Note: This abstract was not presented at the meeting.

Citation Format: Tamer Refaat, Derek West, kathleen R. Harris, Vamsi Parini, William Liu, Beau Wanzer, Lydia Finney, Andrew C. Larson, Jonathan Bautista, Vythialinga Sathiaseelan, Bharat Mittal, Tatjana Paunesku, Gayle Woloschak. Development of Fe3O4@TiO2 core-shell nanocomposites as radiosensitizers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4913. doi:10.1158/1538-7445.AM2014-4913

The Bionanoprobe: hard X-ray fluorescence nanoprobe with cryogenic capabilities

Hard X-ray fluorescence microscopy is one of the most sensitive techniques for performing trace elemental analysis of biological samples such as whole cells and tissues. Conventional sample preparation methods usually involve dehydration, which removes cellular water and may consequently cause structural collapse, or invasive processes such as embedding. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the `natural state', as well as to reduce structural radiation damage, the Bionanoprobe (BNP) has been developed, a hard X-ray fluorescence nanoprobe with cryogenic sample environment and cryo transfer capabilities, dedicated to studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at sector 21 of the Advanced Photon Source. It provides a spatial resolution of 30 nm for two-dimensional fluorescence imaging. In this first demonstration the instrument design and motion control principles are described, the instrument performance is quantified, and the first results obtained with the BNP on frozen-hydrated whole cells are reported.

Nanoparticles for cancer imaging: The good, the bad, and the promise

Recent advances in molecular imaging and nanotechnology are providing new opportunities for biomedical imaging with great promise for the development of novel imaging agents. The unique optical, magnetic, and chemical properties of materials at the scale of nanometers allow the creation of imaging probes with better contrast enhancement, increased sensitivity, controlled biodistribution, better spatial and temporal information, multi-functionality and multi-modal imaging across MRI, PET, SPECT, and ultrasound. These features could ultimately translate to clinical advantages such as earlier detection, real time assessment of disease progression and personalized medicine. However, several years of investigation into the application of these materials to cancer research has revealed challenges that have delayed the successful application of these agents to the field of biomedical imaging. Understanding these challenges is critical to take full advantage of the benefits offered by nano-sized imaging agents. Therefore, this article presents the lessons learned and challenges encountered by a group of leading researchers in this field, and suggests ways forward to develop nanoparticle probes for cancer imaging. Published by Elsevier Ltd.

The study of in vivo acute effect of two different delivery modalities of iron oxide core with titanium dioxide shell nanoparticles in rabbits liver tumor

e22204

Background: To compare intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core with titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits and detect the NPs distribution and effect of NPs presence on the target tumor and other rabbit’s organs. Methods: After obtaining the IACUC approval, liver tumors were obtained by implantation of tumor tissue obtained from a hind limb VX2 tumor of donor rabbits. NPs were delivered either IV or IC. After rabbit termination, 2 hours post NPs injection, tumor, liver, kidney, lung and spleen were harvested, split in half and a part of it was frozen while the remainder was formalin fixed and paraffin embedded. To assess the NPs distribution in 2D we stained 5um thick paraffin tissue sections using Dopamine-Biotin-DHS histochemical (HC) staining followed by Nanozoomer microscopy analysis. H and E staining, TUNEL assay and Ki67 immunohistochemistry were also done. X-ray Fluorescence Microscopy (XFM) was used to quantify the NPs. Frozen tissue was used for bulk NPs concentration analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results: This study included ten rabbits; 3 rabbits had IV NPs injections, 3 had IC NPs injection, 2 control and 2 donors. ICP-MS analysis showed statistically significant higher NPs concentration in tumors of IC arm vs. IV arm (p= 0.0356), while there was higher concentration of NPs in liver (p=0.00077) and spleen (p = 0.01356) of IV vs. IC arms but no difference in kidneys or lungs. These findings were consistent with results from HC and XFM analyses. HC 2D analysis of NPs distribution showed that the RES have taken up the NPs non-specifically. There were no statistically significant differences between the treatment groups regarding the Ki67 proliferation or the TUNEL apoptosis indices or when control rabbits were compared to NPs treated rabbits. Conclusions: Both IV and IC NPs injection are feasible modalities for delivering NPs to tumors with acceptable acute systemic effects and comparable tumor effect. IV delivery increased sequestration of the NPs by RES and their accumulation in spleen and liver.

Superparamagnetic nanoparticles targeting cancer cells invading the extracellular matrix

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Background: Metastatic cancer cells secrete matrix metalloproteinases (MMP), which allow cancer cells to burrow their way to the nearby vasculature. Therefore, MMPs are potential targets for anticancer treatment. Nanoparticles (NPs) can be crafted to adhere to the ECM and subsequently be released in response to advance of invasive cells. The objective of the study is to elucidate the interaction of cancer cells in a three-dimensional culture, with functionalized SPIONS targeted to the extracellular matrix around them. Methods: SPIONS, 15-20 nm in size were functionalized using different coatings: ficoll 400, sucrose, lysine-arginine, dextran50,000. Cellular uptake studies using cervical adenocarcinoma HeLa cell lines were performed to determine the optimum formulation taken up by the cells, using electron microscopy and Prussian blue staining for optical microscopy. Two types of extracellular matrices were used: Rat-tail Collagen type I and ECM gel from Engelbreth-Holm-Swarm murine sarcoma with NPs embedded in them. To assess the capability of cells to invade the matrix, cells were grown on the surface of the matrices for 1 week To evaluate the ability to grow, expand and migrate inside the matrix, cells were embedded within the matrix and left for 14 days. Comparison was made in the presence or absence of SPIONS. Results: Sucrose-coated SPIONS were taken up the best by HeLa cell lines as evaluated by MRI. MMP-1 Secretion allowed HeLa cell invasion of collagen type-1 matrix unidirectionally. Cells could adhere, proliferate, differentiate and migrate in the absence of SPIONS. Cells positive for MMP-9 invaded ECM gel from Engelbreth-Hol-Swarm murine sarcoma matrix also only in the absence of SPIONS. Cells that were found engulfing SPIONS showed morphological features of apoptosis as nuclear pyknosis and karryorhexis. Conclusions: Targeting NPs to the ECM surrounding cancer cells that have developed a metastatic potential represents an attractive platform for cancer therapeutics. The findings show a great promise for development of new theranostic agents, that can be directed to the tumor environment using external magnetic fields, with subsequent suppression of invasion and even destroying malignant cells.

Manganese superoxide dismutase interacts with a large scale of cellular and mitochondrial proteins in low-dose radiation-induced adaptive radioprotection

The cellular adaptive response to certain low-level genotoxic stresses, including exposure to low-dose ionizing radiation (LDIR), shows promise as a tool to enhance radioprotection in normal cells but not in tumor cells. Manganese superoxide dismutase (MnSOD), a fundamental mitochondrial antioxidant in mammalian cells, plays a key role in the LDIR-induced adaptive response. In this study, we aimed to elucidate the signaling network associated with MnSOD-induced radiation protection. A MnSOD-interacting protein profile was established in LDIR-treated human skin cells. Human skin keratinocytes (HK18) were irradiated with a single dose of LDIR (10 cGy X-ray) and the cell lysates were immunoprecipitated using α-MnSOD and applied to two different gel-based proteomic experiments followed by mass spectrometry for protein identification. Analysis of the profiles of MnSOD-interacting partners before and after LDIR detected various patterns of MnSOD protein-protein interactions in response to LDIR. Interestingly, many of the MnSOD-interacting proteins are known to have functions related to mitochondrial regulation of cell metabolism, apoptosis, and DNA repair. These results provide evidence indicating that in addition to the enzymatic action of detoxifying superoxide, the antioxidant MnSOD may function as a signaling regulator in stress-induced adaptive protection through cell survival pathways.

Past and future work on radiobiology mega-studies: a case study at Argonne National Laboratory

Between 1952 and 1992, more than 200 large radiobiology studies were conducted in research institutes throughout Europe, North America, and Japan to determine the effects of external irradiation and internal emitters on the lifespan and tissue toxicity development in animals. At Argonne National Laboratory, 22 external beam studies were conducted on nearly 700 beagle dogs and 50,000 mice between 1969 and 1992. These studies helped to characterize the effects of neutron and gamma irradiation on lifespan, tumorigenesis, and mutagenesis across a range of doses and dosing patterns. The records and tissues collected at Argonne during that time period have been carefully preserved and redisseminated. Using these archived data, ongoing statistical work has been done and continues to characterize quality of radiation, dose, dose rate, tissue, and gender-specific differences in the radiation responses of exposed animals. The ongoing application of newly-developed molecular biology techniques to the archived tissues has revealed gene-specific mutation rates following exposure to ionizing irradiation. The original and ongoing work with this tissue archive is presented here as a case study of a more general trend in the radiobiology megastudies. These experiments helped form the modern understanding of radiation responses in animals and continue to inform development of new radiation models. Recent archival efforts have facilitated open access to the data and materials produced by these studies, and so a unique opportunity exists to expand this continued research.

Interrogation of EGFR Targeted Uptake of TiO2 Nanoconjugates by X-ray Fluorescence Microscopy

We are developing TiO₂ nanoconjugates that can be used as therapeutic and diagnostic agents. Nanoscale TiO₂ can be surface conjugated with various molecules and has the unique ability to induce the production of reactive oxygen species after radiation activation. One way to improve the potential clinical usefulness of TiO₂ nanoparticles is to control their delivery to malignant cells by targeting them to cancer cell specific antigens. Epidermal Growth Factor Receptor is one potential target that is enriched in epithelial cancers and is rapidly internalized after ligand binding. Hence, we have synthesized TiO₂ nanoparticles and functionalized them with a short EGFR binding peptide to create EGFR-targeted NCs. X-ray Fluorescence Microscopy was used to image nanoconjugates within EGFR positive HeLa cells. Further labeling of fixed cells with antibodies against EGFR and Protein A nanogold showed that TiO₂ nanoconjugates can colocalize with receptors at the cell's plasma membrane. Interestingly, with increased incubation times, EGFR targeted nanoconjugates could also be found colocalized with EGFR within the cell nucleus. This suggests that EGFR-targeted nanoconjugates can bind the receptor at the cell membrane, which leads to the internalization of NC-receptor complexes and the subsequent transport of nanoconjugates into the nucleus.

SOD2-mediated effects induced by WR1065 and low-dose ionizing radiation on micronucleus formation in RKO human colon carcinoma cells

RKO36 cells exposed to either WR1065 or 10 cGy X rays show elevated SOD2 gene expression and SOD2 enzymatic activity. Cells challenged at this time with 2 Gy exhibit enhanced radiation resistance. This phenomenon has been identified as a delayed radioprotective effect or an adaptive response when induced by thiols or low-dose radiation, respectively. In this study we investigated the relative effectiveness of both WR1065 and low-dose radiation in reducing the incidence of radiation-induced micronucleus formation in binucleated RKO36 human colon carcinoma cells. The role of SOD2 in this process was assessed by measuring changes in enzymatic activity as a function of the inducing agent used, the level of protection afforded, and the inhibitory effects of short interfering RNA (SOD2 siRNA). Both WR1065 and 10 cGy X rays effectively induced a greater than threefold elevation in SOD2 activity 24 h after exposure. Cells irradiated at this time with 2 Gy exhibited a significant resistance to micronucleus formation (P < 0.05; Student's two-tailed t test). This protective effect was significantly inhibited in cells transfected with SOD2 siRNA. SOD2 played an important role in the adaptive/delayed radioprotective response by inhibiting the initiation of a superoxide anion-induced ROS cascade leading to enhanced mitochondrial and nuclear damages.

Peptide-mediated cancer targeting of nanoconjugates

Targeted use of nanoparticles in vitro, in cells, and in vivo requires nanoparticle surface functionalization. Moieties that can be used for such a purpose include small molecules as well as polymers made of different biological and organic materials. Short amino acid polymers, peptides, can often rival target binding avidity of much larger molecules. At the same time, peptides are smaller than most nanoparticles and thus allow for multiple nanoparticle modifications and creation of pluripotent nanoparticles. Most nanoparticles provide multiple binding sites for different cargo and targeting peptides which can be used for the development of novel approaches for cancer targeting, diagnostics, and therapy. In this review, we will focus on peptides which have been used for the preparation of different nanoparticles designed for cancer research.

Endocytosis of titanium dioxide nanoparticles in prostate cancer PC-3M cells

Nanotechnology has introduced many exciting new tools for the treatment of human diseases. One of the obstacles in its application to that end is the lack of a fundamental understanding of the interaction that occurs between nanoparticles and living cells. This report describes the quantitative analysis of the kinetics and endocytic pathways involved in the uptake of anatase titanium dioxide (TiO(2)) nanoparticles into prostate cancer PC-3M cells. The experiments were performed with TiO(2) nanoconjugates: 6-nm nanoparticles with surface-conjugated fluorescent Alizarin Red S. Results obtained by flow cytometry, fluorescence microscopy, and inductively coupled plasma-mass spectrometry confirmed a complex nanoparticle-cell interaction involving a variety of endocytic mechanisms. The results demonstrated that a temperature, concentration, and time-dependent internalization of the TiO(2) nanoparticles and nanoconjugates occurred via clathrin-mediated endocytosis, caveolin-mediated endocytosis, and macropinocytosis.

FROM THE CLINICAL EDITOR

The interaction and uptake of TiO(2) nanoparticles (6-nm) with prostate PC-3M cells was investigated and found to undergo temperature, time, and concentration dependent intracellular transport that was mediated through clathrin pits, caveolae, and macropinocytosis. These results suggest that nanoparticles may widely permeate through tissues and enter almost any active cell through a variety of biological mechanisms, posing both interesting opportunity and possible challenges for systemic use.

Tissue and data archives from irradiation experiments conducted at Argonne National Laboratory over a period of four decades

Irradiation experiments conducted on dogs and mice at Argonne National Laboratory, IL between 1952 and 1992 led to creation of archives of paraffin-embedded tissues accompanied by extensive datasets with gross pathology and histopathology information. Over the past 40 years, these data were investigated computationally, using different statistical approaches. Embedded tissues are used to this day as a source of genomic and mitochondrial DNA for quantitative PCR amplification. Data and paraffin block sections are available upon request-interested researchers should visit the Websites http://janus.northwestern.edu/dog_tissues/introduction.php for dog and http://janus.northwestern.edu/janus2/index.php for mouse archive.

Fast-scanning high-flux microprobe for biological X-ray fluorescence microscopy and microXAS

There is a growing interest in the biomedical community in obtaining information concerning the distribution and local chemical environment of metals in tissues and cells. Recently, biological X-ray fluorescence microscopy (XFM) has emerged as the tool of choice to address these questions. A fast-scanning high-flux X-ray microprobe, built around a recently commissioned pair of 200 mm-long Rh-coated silicon Kirkpatrick-Baez mirrors, has been constructed at BioCAT beamline 18ID at the Advanced Photon Source. The new optical system delivers a flux of 1.3 x 10(12) photons s(-1) into a minimum focal spot size of approximately 3-5 microm FWHM. A set of Si drift detectors and bent Laue crystal analyzers may be used in combination with standard ionization chambers for X-ray fluorescence measurements. BioCAT's scanning software allows fast continuous scans to be performed while acquiring and storing full multichannel analyzer spectra per pixel on-the-fly with minimal overhead time (<20 ms per pixel). Together, the high-flux X-ray microbeam and the rapid-scanning capabilities of the BioCAT beamline allow the collection of XFM and micro X-ray absorption spectroscopy (microXAS) measurements from as many as 48 tissue sections per day. This paper reports the commissioning results of the new instrument with representative XFM and microXAS results from tissue samples.

Intraprocedural diffusion-weighted PROPELLER MRI to guide percutaneous biopsy needle placement within rabbit VX2 liver tumors

PURPOSE

To test the hypothesis that diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors.

MATERIALS AND METHODS

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DW-PROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW-PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW-PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology.

RESULTS

DW-PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region-of-interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments.

CONCLUSION

DW-PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW-PROPELLER method may offer an important complementary tool for functional guidance during MR-guided percutaneous procedures.

Labeling TiO2 nanoparticles with dyes for optical fluorescence microscopy and determination of TiO2-DNA nanoconjugate stability

Visualization of nanoparticles without intrinsic optical fluorescence properties is a significant problem when performing intracellular studies. Such is the case with titanium dioxide (TiO2) nanoparticles. These nanoparticles, when electronically linked to single-stranded DNA oligonucleotides, have been proposed to be used both as gene knockout devices and as possible tumor imaging agents. By interacting with complementary target sequences in living cells, these photoinducible TiO2-DNA nanoconjugates have the potential to cleave intracellular genomic DNA in a sequence specific and inducible manner. The nanoconjugates also become detectable by magnetic resonance imaging with the addition of gadolinium Gd(III) contrast agents. Herein two approaches for labeling TiO2 nanoparticles and TiO2-DNA nanoconjugates with optically fluorescent agents are described. This permits direct quantification of fluorescently labeled TiO2 nanoparticle uptake in a large population of living cells (>10(4) cells). X-ray fluorescence microscopy (XFM) is combined with fluorescent microscopy to determine the relative intracellular stability of the nanoconjugates and used to quantify intracellular nanoparticles. Imaging the DNA component of the TiO2-DNA nanoconjugate by fluorescent confocal microscopy within the same cell shows an overlap with the titanium signal as mapped by XFM. This strongly implies the intracellular integrity of the TiO2-DNA nanoconjugates in malignant cells.

Superparamagnetic iron oxide nanoparticle-labeled cells as an effective vehicle for tracking the GFP gene marker using magnetic resonance imaging

BACKGROUND

Detection of a gene using magnetic resonance imaging (MRI) is hindered by the magnetic resonance (MR) targeting gene technique. Therefore it may be advantageous to image gene-expressing cells labeled with superparamagnetic iron oxide (SPIO) nanoparticles by MRI.

METHODS

The GFP-R3230Ac (GFP) cell line was incubated for 24 h using SPIO nanoparticles at a concentration of 20 microg Fe/mL. Cell samples were prepared for iron content analysis and cell function evaluation. The labeled cells were imaged using fluorescent microscopy and MRI.

RESULTS

SPIO was used to label GFP cells effectively, with no effects on cell function and GFP expression. Iron-loaded GFP cells were successfully imaged with both fluorescent microscopy and T2*-weighted MRI. Prussian blue staining showed intracellular iron accumulation in the cells. All cells were labeled (100% labeling efficiency). The average iron content per cell was 4.75+/-0.11 pg Fe/cell (P<0.05 versus control).

DISCUSSION

This study demonstrates that the GFP expression of cells is not altered by the SPIO labeling process. SPIO-labeled GFP cells can be visualized by MRI; therefore, GFP, a gene marker, was tracked indirectly with the SPIO-loaded cells using MRI. The technique holds promise for monitoring the temporal and spatial migration of cells with a gene marker and enhancing the understanding of cell- and gene-based therapeutic strategies.

Four-dimensional transcatheter intraarterial perfusion (TRIP)-MRI for monitoring liver tumor embolization in VX2 rabbits

Transcatheter intraarterial perfusion (TRIP)-MRI is an intraprocedural technique to iteratively monitor liver tumor perfusion changes during transcatheter arterial embolization (TAE) and chemoembolization (TACE). However, previous TRIP-MRI approaches using two-dimensional (2D) T(1)-weighted saturation-recovery gradient-recalled echo (GRE) sequences provided only limited spatial coverage and limited capacity for accurate perfusion quantification. In this preclinical study, a quantitative 4D TRIP-MRI technique (serial iterative 3D volumetric perfusion imaging) with rigorous radiofrequency (RF) B(1) field calibration and dynamic tissue longitudinal relaxation rate R(1) measurement is presented for monitoring intraprocedural liver tumor perfusion during TAE. 4D TRIP-MRI and TAE were performed in five rabbits with eight VX2 liver tumors (N = 8). After B(1) calibrated baseline and dynamic R(1) quantification, subsequent tissue contrast agent concentration time curves were derived. A single-input flow-limited pharmacokinetic model and peak gradient method were applied for perfusion analysis. The perfusion Frho reduced significantly from pre-TAE 0.477 (95% confidence interval [CI]: 0.384-0.570) to post-TAE 0.131 (95% CI: 0.080-0.183 ml/min/ml, P < 0.001).