MicroRNA-regulated non-viral vectors with improved tumor specificity in an orthotopic rat model of hepatocellular carcinoma.

In hepatocellular carcinoma (HCC), tumor specificity of gene therapy is of utmost importance to preserve liver function. MicroRNAs (miRNAs) are powerful negative regulators of gene expression and many are downregulated in human HCC. We identified seven miRNAs that are also downregulated in tumors in a rat hepatoma model (P<0.05) and attempted to improve tumor specificity by constructing a panel of luciferase-expressing vectors containing binding sites for these miRNAs. Attenuation of luciferase expression by the corresponding miRNAs was confirmed across various cell lines and in mouse liver. We then tested our vectors in tumor-bearing rats and identified two miRNAs, miR-26a and miR-122, that significantly decreased expression in liver compared with the control vector (6.40 and 0.26%, respectively; P<0.05). In tumor, miR-122 had a nonsignificant trend towards decreased (∼50%) expression, whereas miR-26 had no significant effect on tumor expression. To our knowledge, this is the first work using differentially expressed miRNAs to de-target transgene expression in an orthotopic hepatoma model and to identify miR-26a, in addition to miR-122, for de-targeting liver. Considering the heterogeneity of miRNA expression in human HCC, this information will be important in guiding development of more personalized vectors for the treatment of this devastating disease.

Potent, tumor-specific gene expression in an orthotopic hepatoma rat model using a Survivin-targeted, amplifiable adenoviral vector.

Ideal cancer gene therapies should have high tumor specificity and efficacy, and allow systemic administration to target metastases. We recently developed a bi-directional, two-step transcriptional amplification (TSTA) system driven by the tumor-specific Survivin promoter (pSurv) to amplify the correlated expression of both the reporter gene firefly luciferase (FL) and therapeutic gene tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Here, we compare the specificity and potency of an adenovirus carrying this system (Ad-pSurv-TSTA-TRAIL-FL) to a nonspecific vector (Ad-pCMV-FL) in an orthotopic hepatocellular carcinoma (HCC) rat model after systemic administration. At 24 h after injection of Ad-pCMV-FL, bioluminescence imaging revealed a trend (P=0.30) towards greater FL expression in liver versus tumor. In striking contrast, Ad-pSurv-TSTA-TRAIL-FL showed increased FL activity within the tumor compared with the liver (P<0.01), a strong trend towards reduced liver expression compared with Ad-pCMV-FL (P=0.07), and importantly, similar FL levels within tumor compared with Ad-pCMV-FL (P=0.32). Hence, this vector shows potent, tumor-specific transgene expression even after extensive liver transduction and may be of significant value in avoiding hepatotoxicity in HCC patients. Future studies will explore the benefits of tumor-specific TRAIL expression in this model, the potential to target metastases and the extension of this vector for the treatment of other Survivin-positive tumors is warranted.

Response of balloon-expandable endoprosthetic metallic stents subjected to over-expansion in vitro.

We attempted to evaluate the in vitro behavior and performance of balloon-expandable endoprosthetic metallic stents subjected to over-expansion (OE). Seventy-two balloon-expandable endoprosthetic stents, representing 22 models from six manufacturers, were overexpanded in vitro. Stents were initially expanded to their maximum manufacturer- recommended diameter and then over-expanded incrementally to their endpoints. Endpoints for OE were either stent disarticulation or an inability to undergo further expansion despite balloon insufflation to maximum burst pressure. Measurements of stent dimensions were recorded at each overexpanded diameter and comparisons were made to manufacturer's specifications. A total of 288 balloon-driven expansions were performed on 72 stents. Sixteen stents were expanded to large diameters (> or = 16 mm), 20 stents underwent OE of 50% or greater. One model tended to disarticulate after OE greater than 50%. There were five models that had a tendency to disarticulate after minimal OE. Five models were resistant to OE (25% or less OE) but did not disarticulate. Nearly all stents showed some degree of foreshortening with OE, while 36 stents underwent foreshortening of 30% or more. Models that are not recommended for OE include Intrastent, Intrastent DoubleStrut, NIR Royale and Omniflex. Good candidates for OE include Intrastent DoubleStrut LD, Palmaz large, Medtronic Extra Support Biliary Plus and Medtronic Flexible Biliary. Palmaz XL remains the only model available for expansion from 20 to 28 mm in diameter. For the remaining stents, OE is possible, however, caution should be used.

MR-trackable intramyocardial injection catheter.

There is growing interest in delivering cellular agents to infarcted myocardium to prevent postinfarction left ventricular remodeling. MRI can be effectively used to differentiate infarcted from healthy myocardium. MR-guided delivery of cellular agents/therapeutics is appealing because the therapeutics can be precisely targeted to the desired location within the infarct. In this study, a steerable intramyocardial injection catheter that can be actively tracked under MRI was developed and tested. The components of the catheter were arranged to form a loopless RF antenna receiver coil that enabled active tracking. Feasibility studies were performed in canine and porcine myocardial infarction models. Myocardial delayed-enhancement (MDE) imaging identified the infarcted myocardium, and real-time MRI was used to guide left ventricular catheterization from a carotid artery approach. The distal 35 cm of the catheter was seen under MRI with a bright signal at the distal tip of the catheter. The catheter was steered into position, the distal tip was apposed against the infarct, the needle was advanced, and a bolus of MR contrast agent and tissue marker dye was injected intramyocardially, as confirmed by imaging and postmortem histology. A pilot study involving intramyocardial delivery of magnetically labeled stem cells demonstrated the utility of the active injection catheter system.

Lymphoscintigraphy in the diagnosis of lymphatic leak after surgical repair of femoral artery injury.

PURPOSE: Technetium-99m-labeled sulfur colloid lymphoscintigraphy is useful to evaluate lower extremity lymphatic circulation in cases of possible lymphedema and to reveal abnormal lymphatic collections. Groin lymphatic fistulas and lymphoceles are known complications of peripheral vascular surgical procedures. The authors describe a patient with ascites that developed into right lower extremity swelling after surgical repair of a femoral artery injury. Even after surgical ligation of multiple lymphatic channels, the patient continued to have lymphorrhea. It was unclear whether this was attributable to a persistent lymphatic leak or an ascitic leak from a postsurgical defect resulting in an abnormal connection with the peritoneal cavity. METHODS: Lymphoscintigraphy of the lower extremities was performed using Tc-99m sulfur colloid. Images were obtained at several intervals after injection of the radiotracer. Images were also acquired after the wound packing was removed. RESULTS: The images revealed an accumulation of radiotracer in the right groin, confirming the lower extremity lymphatic origin of the collection. CONCLUSIONS: Lymphoscintigraphy is useful to evaluate the origin of serous collections in the groin, a region in which lymphatic complications of vascular surgery are not uncommon.

GPIIb-IIIa receptor inhibitors: what the interventional radiologist needs to know.

The glycoprotein IIb-IIIa (GPIIb-IIIa) receptor inhibitors have established themselves as first line therapy in the treatment of acute coronary syndromes (ACS) and percutaneous coronary intervention (PCI). The benefit of these agents rests in their ability to attenuate the deleterious effects of platelet activation, both at the site of an inflamed vessel wall (due to a ruptured plaque or PCI) and in the microcirculation as a result of embolization. Based on these results, interventional radiologists are beginning to explore the potential of using GPIIb-IIIa inhibitors during interventions in the peripheral circulation. This paper reviews the molecular biology of the GPIIb-IIIa receptor, the pharmacology of the GPIIb-IIIa receptor inhibitors, the current coronary and peripheral vascular literature as it pertains to the GPIIb-IIIa receptor inhibitors, and potential future applications of the GPIIb-IIIa receptor inhibitors in the peripheral circulation.

Three-dimensional helical CT angiography in renal transplant recipients: a new problem-solving tool.

OBJECTIVE: Our objective was to describe the use of three-dimensional helical CT angiography for the evaluation of renal transplant recipients presenting with hypertension, graft dysfunction, or both after transplantation by evaluating the native and transplanted renal arteries in a single examination. CONCLUSION: Early results indicate that three-dimensional helical CT angiography of renal transplant recipients presenting with hypertension, graft dysfunction, or both after transplantation yields valuable information that can be used to guide further therapy.

Utilization of computed tomography in patients hospitalized with community-acquired pneumonia.

The objective of the study was to assess the frequency of the use of chest computed tomography in 385 adults hospitalized with community-acquired pneumonia and determine whether the computed tomography examinations yielded additional diagnostic information. Also, if additional information was obtained, the study determined whether it changed the patient's treatment plan.

Thrombosis of the deep femoral vein: a potential pitfall of color flow duplex Doppler ultrasonography.

This case illustrates a potential pitfall of color flow duplex Doppler ultrasonography with compression in the evaluation of suspected deep venous thrombosis (DVT). Because of its low cost, accuracy, and noninvasiveness, ultrasonography is the appropriate first choice in the evaluation of suspected DVT, but there does exist the possibility of a false-negative examination. Magnetic resonance venography (MRV) should be reserved for cases in which there is a high clinical suspicion for DVT, as well as either morbid obesity that would limit the evaluation of deep pelvic and deep femoral veins or conflicting results of other imaging studies. All cases of suspected thrombosis, including those not adequately evaluated by ultrasonography, can be accurately assessed by MRV, which is not as invasive as standard venography.