Jacqueline Corbeil

mTOR and HIF-1α-mediated tumor metabolism in an LKB1 mouse model of Peutz-Jeghers syndrome

Peutz-Jeghers syndrome (PJS) is a familial cancer disorder due to inherited loss of function mutations in the LKB1/ STK11 serine/threonine kinase. PJS patients develop gastrointestinal hamartomas with 100% penetrance often in the second decade of life, and demonstrate an increased predisposition toward the development of a number of additional malignancies. Among mitogenic signaling pathways, the mammalian-target of rapamycin complex 1 (mTORC1) pathway is hyperactivated in tissues and tumors derived from LKB1-deficient mice. Consistent with a central role for mTORC1 in these tumors, rapamycin as a single agent results in a dramatic suppression of preexisting GI polyps in LKB1+/− mice. However, the key targets of mTORC1 in LKB1-deficient tumors remain unknown. We demonstrate here that these polyps, and LKB1- and AMPK-deficient mouse embryonic fibroblasts, show dramatic up-regulation of the HIF-1α transcription factor and its downstream transcriptional targets in an rapamycin-suppressible manner. The HIF-1α targets hexokinase II and Glut1 are up-regulated in these polyps, and using FDG-PET, we demonstrate that LKB1+/− mice show increased glucose utilization in focal regions of their GI tract corresponding to these gastrointestinal hamartomas. Importantly, we demonstrate that polyps from human Peutz-Jeghers patients similarly exhibit up-regulated mTORC1 signaling, HIF-1α, and GLUT1 levels. Furthermore, like HIF-1α and its target genes, the FDG-PET signal in the GI tract of these mice is abolished by rapamycin treatment. These findings suggest a number of therapeutic modalities for the treatment and detection of hamartomas in PJS patients, and potential for the screening and treatment of the 30% of sporadic human lung cancers bearing LKB1 mutations.

Time Course and Role of Morphine Dose and Concentration in Intrathecal Granuloma Formation in Dogs A Combined Magnetic Resonance Imaging and Histopathology Investigation

Background:Intrathecal morphine infusion leads to intrathecal granulomas. In dogs, the authors examined time course of granuloma formation and the role of concentration in granuloma development. Methods:Dogs were prepared with lumbar intrathecal catheters and vest-mounted pumps. To define the time course of granuloma formation, serial magnetic resonance imaging was performed in animals receiving 10 or 31 days of morphine infusion (12.5 mg/ml at 40 &mgr;l/h). At these times, morphine was removed from the infusate, and further magnetic resonance images were acquired over 14–35 additional days. To assess dose versus concentration, dogs received 28-day infusions of vehicle, 12 mg morphine/day as 12.5 mg/ml at 40 &mgr;l/h, or 1.5 mg/ml at 334 &mgr;l/h (12 mg/day) for 28 days. Additional dogs received 3 mg/day as 12.5 mg/ml at 10 &mgr;l/h. Results:Serial magnetic resonance images in dogs receiving morphine (12.5 mg/ml at 40 &mgr;l/h) revealed pericatheter-enhancing tissues as early as 3 days with a prominent signal by 10 days. Removal of morphine reduced the mass volume within 7 days. At a fixed infusion rate, the incidence of granuloma formation with the continuous intrathecal infusion of morphine ranged from 0 in vehicle-treated dogs to 100% in dogs treated with 12.5 mg/ml at 40 &mgr;l/h (12 mg/day). Infusion of 12 mg/day at 1.5 mg/ml (334 &mgr;l/h) resulted in granuloma in one of four animals. The authors found that infusion of morphine in different concentrations at a fixed rate resulted in a dose-dependent increase in concentration, with the granuloma-producing, dose-yielding lumbar cerebrospinal fluid morphine concentrations around 40 &mgr;g/ml. Conclusions:Serial magnetic resonance imaging showed a rapid formation and regression of the masses initiated by intrathecal morphine infusion. These masses are dependent on local concentration.

Validation of ultrasound contrast destruction imaging for flow quantification

Abstract Our purpose was to validate in vitro a kinetic flow model based on microbubble signal decay curve. Using a 3.5 MHz transducer and phase-inversion (1.8 MHz central transmit frequency), a renal dialysis cartridge oriented vertically was imaged in the transverse plane as 1:1000 dilution of AF0150 was infused at 50, 100, 200, 300 and 400 mL/min. Ten gray-scale images were acquired at each infusion rate using 2.5, 5 and 10 frames/s at 100%, 40%, 15% or 1% of maximum transmit power. Video-intensity measured on each 10 images was fit to a kinetic model using Sigma Plot that yielded microbubble concentration, velocity and destruction per frame. These were correlated with the experimental conditions. At 100% power, video-intensity on the first frame (microbubble concentration at equilibrium) was similar for all flow and frame rates. The model fit the experimental data for all flows at 10 frames/s and for flows lower than 400 and 100 mL/min at 5 frames/s and 2.5 frames/s, respectively. The calculated flow was similar to the experimental flow rates, regardless of technique (r 2 = 0.98). Microbubble fraction destroyed per frame was similar for all flow and frame rates and increased linearly with transmit power (r 2 > 0.98). These results suggest that using appropriate power and frame rate for a given flow rate, estimates of fractional blood volume, flow and destruction fraction can be calculated from the decay curve using 10 frames that can be acquired in 1 to 4 s. (E-mail: rmattrey@ucsd.edu)

Assessment of cortical bone with clinical and ultrashort echo time sequences

We describe the use of ultrashort echo time (UTE) sequences and fast spin echo sequences to assess cortical bone using a clinical 3T scanner. Regular two‐ and three‐dimensional UTE sequences were used to image both bound and free water in cortical bone. Adiabatic inversion recovery prepared UTE sequences were used to image water bound to the organic matrix. Two‐dimensional fast spin echo sequences were used to image free water. Regular UTE sequences were used together with bicomponent analysis to measure T*2s and relative fractions of bound and free water components in cortical bone. Inversion recovery prepared UTE sequences were used to measure the T*2 of bound water. Saturation recovery UTE sequences were used to measure the T1 of bone water. Eight cadaveric human cortical bone samples and a lower leg specimen were studied. Preliminary results show two distinct components in UTE detected signal decay, a single component in inversion recovery prepared UTE detected signal decay, and a single component in saturation recovery UTE detected signal recovery. Regular UTE sequences appear to depict both bound and free water in cortical bone. Inversion recovery prepared UTE sequences appear to depict water bound to the organic matrix. Two‐dimensional fast spin echo sequences appear to depict bone structure corresponding to free water in large pores. Magn Reson Med 70:697–704, 2013.

Angiogenesis model for ultrasound contrast research

RATIONALE AND OBJECTIVES To optimize an angiogenesis model for imaging research that is stable and can be imaged several times over the angiogenic time course. MATERIALS AND METHODS Mice and rats received two injections of 0.4 mL of extract of basement membrane matrix (Matrigel; Becton Dickinson Labware, Bedford, MA) in the subcutaneous spaces on either side of the spine. One of the two Matrigel plugs in each animal had either 0.1 microg/mL of basic fibroblast growth factor (bFGF) (11 mice), 1.0 microg/mL of bFGF (12 mice, 5 rats), or 1.0 microg/mL of bFGF and 60 U/mL of heparin (11 mice). Three to 12 days after implantation, animals were imaged before and after the administration of up to four injections of 0.1 mL AF0150. Phase inversion imaging was used on a Siemens Elegra (Siemens ultrasound, Issaquah, WA) equipped with a 13 MHz VFX transducer. Three observers subjectively assessed the pattern of enhancement using a four-point scale. The Matrigel plugs were then removed and two observers graded the angiogenic response on a four-point scale. Ten Matrigel plugs, five with 1.0 microg/mL bFGF and five without, were evaluated histologically following immunohistochemical staining with anti-CD31. RESULTS The angiogenic response was greater in Matrigel plugs with 1.0 than with 0.1 microg/mL of bFGF. Heparin did not increase the angiogenic response. Vessels were predominantly at the periphery of the plugs with variable central penetration. Plugs appeared anechoic and homogeneous on ultrasound. Contrast enhancement within the plug occurred in 44% of mice with an angiogenic response at or after day 6 and the enhancement increased with the angiogenic response. In the others, peripheral enhancement could not be distinguished from the enhancement of surrounding tissues that were also hyperemic. The thicker rat skin interfered with plug assessment. CONCLUSION A stable angiogenesis model without the complexity of tumors is described. This model offers the opportunity to image the development and/or inhibition of angiogenesis. Neovasculature in Matrigel was detectable using ultrasound contrast. Quantitative studies correlating the degree of enhancement to microvascular density will be determined in subsequent studies.

Direct imaging and quantification of carotid plaque calcification

Carotid plaque calcification normally appears as a signal void with clinical MR sequences. Here, we describe the use of an adiabatic inversion recovery prepared two‐dimensional ultrashort echo time sequence to image and characterize carotid plaque calcification using a clinical 3‐T scanner. T1, T  2* , and free water content were measured for seven carotid samples, and the results were compared with micro‐CT imaging. Conventional gradient echo and fast spin echo images were also acquired for comparison. Correlations between T1, T  2* , free water concentration, and mineral density were performed. There was a close correspondence between inversion recovery prepared two‐dimensional ultrashort echo time morphologic and micro‐CT appearances. Carotid plaque calcification varied significantly from sample to sample, with T1s ranging from 94 ± 19 to 328 ± 21 msec, T  2* s ranging from 0.31 ± 0.12 to 2.15 ± 0.25 msec, and free water concentration ranging from 5.7 ± 2.3% to 16.8 ± 3.4%. There was a significant positive correlation between T1 (R = 0.709; P < 0.074), T  2* (R = 0.816; P < 0.025), and free water concentration, a negative correlation between T1 (R = 0.773; P < 0.042), T  2* (R = 0.948; P < 0.001) and CT measured mineral density, and a negative correlation between free water concentration (R = 0.936; P < 0.002) and mineral density. Magn Reson Med, 2010.

Assessment of in vivo systemic toxicity and biodistribution of iron-doped silica nanoshells

Silica nanoparticles are an emerging class of biomaterials which may be used as diagnostic and therapeutic tools for biomedical applications. In particular, hollow silica nanoshells are attractive due to their hollow core. Approximately 70% of a 500 nm nanoshell is hollow, therefore more particles can be administered on a mg/kg basis compared to solid nanoparticles. Additionally, their nanoporous shell permits influx/efflux of gases and small molecules. Since the size, shape, and composition of a nanoparticle can dramatically alter its toxicity and biodistribution, the toxicology of these nanomaterials was assessed. A single dose toxicity study was performed in vivo to assess the toxicity of 500 nm iron-doped silica nanoshells at clinically relevant doses of 10-20 mg/kg. This study showed that only a trace amount of silica was detected in the body 10 weeks post-administration. The hematology, biochemistry and pathological results show that the nanoshells exhibit no acute or chronic toxicity in mice.

Abstract P5-01-08: Single dose acute toxicity and long-term biodistribution of perfluoropentane loaded iron doped silica nanoshells

Background: Our lab has been focusing on developing a better method of localizing non-palpable breast cancers without wire or seed localization. Perfluoropentane (PFP) loaded Fe-SiO2 nanoshells have been developed as a color Doppler ultrasound contrast imaging agent which can act as small volume (100 ul) injectable stationary guide-marker for breast tumor resection. Preliminary experiments have demonstrated that the nanoshells can provide robust contrast for periods extending past 10 days in vivo in Py8119 epithelial breast tumor bearing mice with no adverse affect to the mice. Short-term biodistribution over 72 hours of nanoshells using In111 labeled nanoshells demonstrated with gamma scintigraphy that intravenously dosed particles primarily accumulate in the liver but some radioactive signal can be seen in the bladder. The long imaging lifetime of these nanoshells necessitates the need to study long-term toxicity and biodistribution. Materials and Methods: Fe-SiO2 nanoshells and Pure SiO2 nanoshells where synthesized via sol-gel method on polystyrene templates and then calcined to yield 500 nm hollow rigid nanoshells which were then filled with vaporized perfluoropentane. 100 ul of nanoshells at 4 mg/ml of the Fe-SiO2 nanoshells and at a dose of 2 mg/ml of pure SiO2 nanoshells were injected IV into healthy 8-week old Swiss white mice. The difference in mass dose was due to make the particle count between the two doses equivalent. Blood was collected weekly for serum chemistry and hematology. After 10 weeks mice were sacrificed, HE San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-01-08.

Head sinuses, melon, and jaws of bottlenose dolphins, Tursiopstruncatus, observed with computed tomography structural and single photon emission computed tomography functional imaging

The head sinuses, melon, and lower jaws of dolphins have been studied extensively with various methods including radiography, chemical analysis, and imaging of dead specimens. Here we report the first structural and functional imaging of live dolphins. Two animals were imaged, one male and one female. Computed tomography (CT) revealed extensive air cavities posterior and medial to the ear as well as between the ear and sound‐producing nasal structures. Single photon emission computed tomography (SPECT) employing 50 mCi of the intravenously injected ligand technetium [Tc‐99m] biscisate (Neurolite) revealed extensive and uptake in the core of the melon as well as near the pan bone area of the lower jaw. Count density on SPECT images was four times greater in melon as in the surrounding tissue and blubber layer suggesting that the melon is an active rather than a passive tissue. Since the dolphin temporal bone is not attached to the skull except by fibrous suspensions, the air cavities medial and posterior t...