Rat model of metastatic breast cancer monitored by MRI at 3 tesla and bioluminescence imaging with histological correlation.

BACKGROUND: Establishing a large rodent model of brain metastasis that can be monitored using clinically relevant magnetic resonance imaging (MRI) techniques is challenging. Non-invasive imaging of brain metastasis in mice usually requires high field strength MR units and long imaging acquisition times. Using the brain seeking MDA-MB-231BR transfected with luciferase gene, a metastatic breast cancer brain tumor model was investigated in the nude rat. Serial MRI and bioluminescence imaging (BLI) was performed and findings were correlated with histology. Results demonstrated the utility of multimodality imaging in identifying unexpected sights of metastasis and monitoring the progression of disease in the nude rat. METHODS: Brain seeking breast cancer cells MDA-MB-231BR transfected with firefly luciferase (231BRL) were labeled with ferumoxides-protamine sulfate (FEPro) and 1-3 x 106 cells were intracardiac (IC) injected. MRI and BLI were performed up to 4 weeks to monitor the early breast cancer cell infiltration into the brain and formation of metastases. Rats were euthanized at different time points and the imaging findings were correlated with histological analysis to validate the presence of metastases in tissues. RESULTS: Early metastasis of the FEPro labeled 231BRL were demonstrated on T2*-weighted MRI and BLI within 1 week post IC injection of cells. Micro-metastatic tumors were detected in the brain on T2-weighted MRI as early as 2 weeks post-injection in greater than 85% of rats. Unexpected skeletal metastases from the 231BRL cells were demonstrated and validated by multimodal imaging. Brain metastases were clearly visible on T2 weighted MRI by 3-4 weeks post infusion of 231BRL cells, however BLI did not demonstrate photon flux activity originating from the brain in all animals due to scattering of the photons from tumors. CONCLUSION: A model of metastatic breast cancer in the nude rat was successfully developed and evaluated using multimodal imaging including MRI and BLI providing the ability to study the temporal and spatial distribution of metastases in the brain and skeleton.ope

Enhanced stem cell tracking via electrostatically assembled fluorescent SPION-peptide complexes

For cellular MRI there is a need to label cells with superparamagnetic iron oxide nanoparticles (SPION) that have multiple imaging moieties that are nontoxic and have increased NMR relaxation properties to improve the detection and tracking of therapeutic cells. Although increases in the relaxation properties of SPION have been accomplished, detection of tagged cells is limited by either poor cell labeling efficiency or low intracellular iron content. A strategy via a complex formation with transfection agents to overcome these obstacles has been reported. In this paper, we report a complex formation between negatively charged fluorescent monodisperse SPION and positively charged peptides and use the complex formation to improve the MR properties of labeled stem cells. As a result, labeled stem cells exhibited a strong fluorescent signal and enhanced T 2*-weighted MR imaging in vitro and in vivo in a flank tumor modelope

Alternating Acquisition Technique for Quantification of in vitro Hyperpolarized [1-13C] Pyruvate Metabolism

Purpose: To develop a technique for quantifying the 13C-metabolites by performing frequency-selective hyperpolarized 13C magnetic resonance spectroscopy (MRS) in vitro which combines simple spectrally-selective excitation with spectrally interleaved acquisition. Methods: Numerical simulations were performed with varying noise level and Kp values to compare the quantification accuracies of the proposed and the conventional methods. For in vitro experiments, a spectrally-selective excitation scheme was enabled by narrow-band radiofrequency (RF) excitation pulse implemented into a free-induction decay chemical shift imaging (FIDCSI) sequence. Experiments with LDH / NADH enzyme mixture were performed to validate the effectiveness of the proposed acquisition method. Also, a modified two-site exchange model was formulated for metabolism kinetics quantification with the proposed method. Results: From the simulation results, significant increase of the lactate peak signal to noise ratio (PSNR) was observed. Also, the quantified Kp value from the dynamic curves were more accurate in the case of the proposed acquisition method compared to the conventional non-selective excitation scheme. In vitro experiment results were in good agreement with the simulation results, also displaying increased PSNR for lactate. Fitting results using the modified two-site exchange model also showed expected results in agreement with the simulations. Conclusion: A method for accurate quantification of hyperpolarized pyruvate and the downstream product focused on in vitro experiment was described. By using a narrow-band RF excitation pulse with alternating acquisition, different resonances were selectively excited with a different flip angle for increased PSNR while the hyperpolarized magnetization of the substrate can be minimally perturbed with a low flip angle. Baseline signals from neighboring resonances can be effectively suppressed to accurately quantify the metabolism kinetics.ope

Quantitative T2* imaging of metastatic human breast cancer to brain in the nude rat at 3 T.

This study uses quantitative T(2)* imaging to track ferumoxides--protamine sulfate (FEPro)-labeled MDA-MB-231BR-Luc (231BRL) human breast cancer cells that metastasize to the nude rat brain. Four cohorts of nude rats were injected intracardially with FEPro-labeled, unlabeled or tumor necrosis factor-related apoptosis-inducing ligand(TRAIL)-treated (to induce apoptosis) 231BRL cells, or saline, in order to develop metastatic breast cancer in the brain. The heads of the rats were imaged serially over 3-4 weeks using gradient multi-echo and turbo spin-echo pulse sequences at 3 T with a solenoid receive-only 4-cm-diameter coil. Quantitative T(2)* maps of the whole brain were obtained by the application of single-exponential fitting to the signal intensity of T(2)* images, and the distribution of T(2)* values in brain voxels was calculated. MRI findings were correlated with Prussian blue staining and immunohistochemical staining for iron in breast cancer and macrophages. Quantitative analysis of T(2)* from brain voxels demonstrated a significant shift to lower values following the intracardiac injection of FEPro-labeled 231BRL cells, relative to animals receiving unlabeled cells, apoptotic cells or saline. Quartile analysis based on the T(2)* distribution obtained from brain voxels demonstrated significant differences (p < 0.0083) in the number of voxels with T(2)* values in the ranges 10-35  ms (Q1), 36-60  ms (Q2) and 61-86  ms (Q3) from 1 day to 3 weeks post-infusion of labeled 231BRL cells, compared with baseline scans. There were no significant differences in the distribution of T(2)* obtained from serial MRI in rats receiving unlabeled or TRAIL-treated cells or saline. Histologic analysis demonstrated isolated Prussian blue-positive breast cancer cells scattered in the brains of rats receiving labeled cells, relative to animals receiving unlabeled or apoptotic cells. Quantitative T(2)* analysis of FEPro-labeled metastasized cancer cells was possible even after the hypointense voxels were no longer visible on T(2)*-weighted images.ope

Self-confirming "AND" logic nanoparticles for fault-free MRI

Achieving high accuracy in the imaging of biological targets is a challenging issue. For MRI, to enhance imaging accuracy, two different imaging modes with specific contrast agents are used; one is a T1 type for a "positive" MRI signal and the other is a T2 type for a "negative" signal. Conventional contrast agents respond only in a single imaging mode and frequently encounter ambiguities in the MR images. Here, we propose a "magnetically decoupled" core-shell design concept to develop a dual mode nanoparticle contrast agent (DMCA). This DMCA not only possesses superior MR contrast effects but also has the unique capability of displaying "AND" logic signals in both the T1 and T2 modes. The latter enables self-confirmation of images and leads to greater diagnostic accuracy. A variety of novel DMCAs are possible, and the use of DMCAs can potentially bring the accuracy of MR imaging of diseases to a higher level.ope

Clinical Feasibility of Synthetic Magnetic Resonance Imaging in the Diagnosis of Internal Derangements of the Knee

Objective: To evaluate the feasibility of synthetic magnetic resonance imaging (MRI) compared to conventional MRI for the diagnosis of internal derangements of the knee at 3T. Materials and Methods: Following Institutional Review Board approval, image sets of conventional and synthetic MRI in 39 patients were included. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images. Subjective image quality was assessed using a four-grade scale. Interobserver agreement and intersequence agreement between conventional and synthetic images for cartilage lesions, tears of the cruciate ligament, and tears of the meniscus were independently assessed using Kappa statistics. In patients who underwent arthroscopy (n = 8), the sensitivity, specificity, and accuracy for evaluated internal structures were calculated using arthroscopic findings as the gold standard. Results: There was no statistically significant difference in image quality (p = 0.90). Interobserver agreement (kappa = 0.649- 0.981) and intersequence agreement (kappa = 0.794-0.938) were nearly perfect for all evaluated structures. The sensitivity, specificity, and accuracy for detecting cartilage lesions (sensitivity, 63.6% vs. 54.6-63.6%; specificity, 91.9% vs. 91.9%; accuracy, 83.3-85.4% vs. 83.3-85.4%) and tears of the cruciate ligament (sensitivity, specificity, accuracy, 100% vs. 100%) and meniscus (sensitivity, 50.0-62.5% vs. 62.5%; specificity, 100% vs. 87.5-100%; accuracy, 83.3-85.4% vs. 83.3-85.4%) were similar between the two MRI methods. Conclusion: Conventional and synthetic MRI showed substantial to almost perfect degree of agreement for the assessment of internal derangement of knee joints. Synthetic MRI may be feasible in the diagnosis of internal derangements of the knee.ope

Cancer -Targeted MR Molecular Imaging

Magnetic resonance (MR) imaging has been widely used in the clinic because of the benefit of high spatial and temporal resolution, and the excellent anatomical tissue contrast. Cancer-targeted MR molecular imaging comprises 3 major components: a relevant molecular target which is specifically highly expressed on the membrane of the cancer cell; a target specific imaging probe which is composed of superparamagnetic iron oxide nanoparticle coreconjugated target specific ligand such as antibody, peptide, and molecules; MR imaging hardware and software which are sensitive to the imaging probe. Among the various molecular targets, HER2/neu receptor antibody, folic acid, and arginine-glycine-aspartic acid (RGD) are well known targeting ligands. The sensitivity of the cancer-targeted MR imaging is affected by the magnetic susceptibility of the T2 contrast agent, resolution of the image, targeting efficiency of the imaging probe, and image acquisition pulse sequence. Recently, successful cancer-targeted MR imaging with T1 contrast agent and cancer-specific molecular MR imaging using innate contrast of the cancer cell by chemical exchange phenomenon without using the imaging probe has been introduced. Cancer-targeted MR molecuar imaging is a robust diagnostic method to detect cancer at the cellular stage of the cancer development and it would help improve early detection rate of the cancer.ope

Definition of Ubiquitination Modulator COP1 as a Novel Therapeutic Target in Human Hepatocellular Carcinoma

The development of targeted therapeutics for hepatocellular carcinoma (HCC) remains a major challenge. The ubiquitination modulator COP1 regulates p53 activity by ubiquitination and it is frequently overexpressed in human HCC. In this study, we tested the hypothesis that COP1 blockade by short interfering RNA (siRNA)-mediated inhibition could affect the course of HCC progression. The COP1 isoform COP1-1 was selected as the most effective target for siRNAs in terms of growth inhibition and apoptotic induction in several HCC cell lines. Growth inhibition occurred in HCC cells that retained wild-type p53 or expressed mutant p53 (Y220C or R249S), whereas p53-null Hep3B cells were resistant. Microarray expression analysis revealed that the antiproliferative effects of COP1 blockade were driven by a common subset of molecular alterations including a p53-associated functional network. In an orthotopic mouse xenograft model of HCC, systemic delivery of a modified COP1 siRNA by stable nucleic acid-lipid particles suppressed neoplastic growth in liver without unwanted immune responses. Our findings offer a first proof of principle that COP1 can be a promising target for systemic therapy of HCC.ope

Arsenic Trioxide as a Vascular Disrupting Agent: Synergistic Effect with Irinotecan on Tumor Growth Delay in a CT26 Allograft Model

The mechanism of action of arsenic trioxide (ATO) has been shown to be complex, influencing numerous signal transduction pathways and resulting in a vast range of cellular effects. Among these mechanisms of action, ATO has been shown to cause acute vascular shutdown and massive tumor necrosis in a murine solid tumor model like vascular disrupting agent (VDA). However, relatively little is understood about this VDA-like property and its potential utility in developing clinical regimens. We focused on this VDA-like action of ATO. On the basis of the endothelial cell cytotoxicity assay and tubulin polymerization assay, we observed that higher concentrations and longer treatment with ATO reduced the level of α- and β-tubulin and inhibited the polymerization of tubulin. The antitumor action and quantitative tumor perfusion studies were carried out with locally advanced murine CT26 colon carcinoma grown in female BALB/c mice. A single injection of ATO intraperitoneally displayed central necrosis of the tumor tissue by 24 hours. T1-weighted dynamic contrast-enhanced magnetic resonance image revealed a significant decrease in tumor enhancement in the ATO-treated group. Similar to other VDAs, ATO treatment alone did not delay the progression of tumor growth; however, ATO treatment after injection of other cytotoxic agent (irinotecan) showed significant additive antitumor effect compared to control and irinotecan alone therapy. In summary, our data demonstrated that ATO acts as a VDA by means of microtubule depolymerization. It exhibits significant vascular shutdown activity in CT26 allograft model and enhances antitumor activity when used in combination with another cytotoxic chemotherapeutic agent.ope

Water Fraction Ratio of the Sacroiliac Joint Subchondral Bone Marrow in Patients with Ankylosing Spondylitis Predicts the Degree of Disease Activity

Objectives: Ankylosing spondylitis (AS) is a chronic inflammatory arthritis with characteristic involvement of the spine and sacroiliac joints. MRI may be the only indicator of disease activity or response. This study aimed to use a novel water fraction measurement technique on MRI as a biomarker to predict disease activity in patients with AS. Methods: We enrolled 39 patients (18 men [mean age, 38.6 years; range, 18-59 years] and 21 women [mean age, 39.3 years; range, 23-61 years]) who were clinically diagnosed with AS and underwent MRI, including mDixon sequences. Water fraction values of sacroiliac joint subchondral bone marrow were derived from the mDixon sequences. The Ankylosing Spondylitis Disease Activity Score (ASDAS) was recorded using clinical information and laboratory values from medical records. Multiple linear regression, Firth logistic regression, and intraclass correlation coefficients were used for the statistical analysis. Results: In multiple linear regression, water fraction, subchondral bone marrow edema, subchondral bone erosion, and subchondral bone marrow enhancements were significantly associated with ASDAS with C-reactive protein (ASDAS-CRP). The water fraction parameters showed a good linear correlation with ASDAS-CRP and ASDAS with erythrocyte sedimentation rate (ASDAS-ESR) (beta coefficient = 1.98, p &lt; 0.001 and beta coefficient = 1.60, p = 0.003). Firth logistic regression showed that water fraction was a significant predictor of ASDAS-CRP but not ASDAS-ESR. The intraclass correlation coefficient showed excellent repeatability for the three repeated measures of the water fraction. Conclusion: Water fraction parameter could be a good imaging biomarker of disease activity status. The sacroiliac joint evaluated by mDixon MRI may be a promising biomarker of disease progression in patients with spondyloarthritis.ope