Biomedical subjects

Hadassa Degani

Publications and source records attributed to Hadassa Degani.

At least 19 recordsLinked to original sources

PubMed2006

Real-time imaging of lymphogenic metastasis in orthotopic human breast cancer.

Metastatic spread to regional lymph nodes is one of the earliest events of tumor cell dissemination and presents a most significant prognostic factor for predicting survival of cancer patients. Real-time in vivo imaging of the spread of tumor cells through the lymphatic system can enhance our understanding of the metastatic process. Herein, we describe the use of in vivo fluorescence microscopy imaging to monitor the progression of lymph node metastasis as well as the course of spontaneous metastasis through the lymphatic system of orthotopic MDA-MB-231 human breast cancer tumors in severe combined immunodeficient mice. High-resolution noninvasive visualization of metastasizing cancer cells in the inguinal lymph nodes was achieved using cells expressing high levels of red fluorescent protein. Sequential imaging of these lymph nodes revealed the initial invasion of the tumor cells through the lymphatic system into the subcapsular sinuses followed by intrusion into the parenchyma of the nodes. FITC-dextran injected i.d. in the tumor area enabled simultaneous tracking of lymphatic vessels, labeled in green, and disseminated red cancer cells within these vessels. Fast snapshots of spontaneously metastasizing cells in the lymphatic vessels monitored the movement of a few tumor cells and the development of clumps clustered at lymphatic vessel junctions. Quantification of high interstitial fluid pressure (IFP) in the tumors and fast drainage rates of the FITC-dextran into the peritumoral lymphatic vessels suggested an IFP-induced intravasation into the lymphatic system. This work presents unprecedented live fluorescence images that may help to clarify the steps occurring in the course of spontaneous lymphogenic metastasis.

Animals↗

PubMed2006

Vascular perfusion of human lung cancer in a rat orthotopic model using dynamic contrast-enhanced magnetic resonance imaging.

Lung cancer is the leading cause of death among cancers. Early detection and diagnosis present a major goal in the efforts to improve survival rates of lung cancer patients. Changes in angiogenic activity and microvascular perfusion properties in cancers can serve as markers of malignancy. The aim of this study was to employ MRI means to measure the microvascular perfusion parameters of orthotopic nonsmall cell lung cancer, using the experimental rat model. Anatomical and dynamic contrast-enhanced lung images were acquired at high spatial resolution, and registered and analyzed, pixel by pixel and globally, by means of a model-based algorithm. The MRI output yielded color-coded parametric images of the influx and efflux transcapillary transfer constants that indicated rapid microvascular perfusion. The transfer constants were about 1 order of magnitude higher than those found in other tumors or in nonorthotopic lung cancer, with the influx constant median value of 0.42 min(-1) and the efflux constant median value of 1.61 min(-1). The rapid perfusion was in accord with the immunostaining of the capillaries, which suggested the tumor exploitation of the existing alveolar vessels. The results showed that high resolution, dynamic, contrast-enhanced MRI is an effective tool for the quantitative measurement of spatial and temporal changes in lung cancer perfusion and vasculature.

Algorithms↗

PubMed2006

Inhibition of tumor growth and elimination of multiple metastases in human prostate and breast xenografts by systemic inoculation of a host defense-like lytic peptide.

We report on a short host defense-like peptide that targets and arrests the growth of aggressive and hormone-resistant primary human prostate and breast tumors and prevents their experimental and spontaneous metastases, respectively, when systemically inoculated to immunodeficient mice. These effects are correlated with increased necrosis of the tumor cells and a significant decrease in the overall tumor microvessel density, as well as newly formed capillary tubes and prostate-specific antigen secretion (in prostate tumors). Growth inhibition of orthotopic tumors derived from stably transfected highly fluorescent human breast cancer cells and prevention of their naturally occurring metastases were visualized in real time by using noninvasive whole-body optical imaging. The exclusive selectivity of the peptide towards cancer derives from its specific binding to surface phosphatidylserine and the killing of the cancer cells via cytoplasmic membrane depolarization. These data indicate that membrane disruption can provide a therapeutic means of inhibiting tumor growth and preventing metastases of various cancers.

Adenocarcinoma↗

PubMed2006

Noninvasive magnetic resonance imaging of transport and interstitial fluid pressure in ectopic human lung tumors.

Tumor response to blood borne drugs is critically dependent on the efficiency of vascular delivery and transcapillary transfer. However, increased tumor interstitial fluid pressure (IFP) forms a barrier to transcapillary transfer, leading to resistance to drug delivery. We present here a new, noninvasive method which estimates IFP and its spatial distribution in vivo using contrast-enhanced magnetic resonance imaging (MRI). This method was tested in ectopic human non-small-cell lung cancer which exhibited a high IFP of approximately 28 mm Hg and, for comparison, in orthotopic MCF7 human breast tumors which exhibited a lower IFP of approximately 14 mm Hg, both implanted in nude mice. The MRI protocol consisted of slow infusion of the contrast agent [gadolinium-diethylenetriaminepentaacetic acid (GdDTPA)] into the blood for approximately 2 hours, sequential acquisition of images before and during the infusion, and measurements of T1 relaxation rates before infusion and after blood and tumor GdDTPA concentration reached a steady state. Image analysis yielded parametric images of steady-state tissue GdDTPA concentration with high values of this concentration outside the tumor boundaries, approximately 1 mmol/L, declining in the tumor periphery to approximately 0.5 mmol/L, and then steeply decreasing to low or null values. The distribution of steady-state tissue GdDTPA concentration reflected the distribution of IFP, showing an increase from the rim inward, with a high IFP plateau inside the tumor. The changes outside the borders of the tumors with high IFP were indicative of convective transport through the interstitium. This work presents a noninvasive method for assessing the spatial distribution of tumor IFP and mapping barriers to drug delivery and transport.

Animals↗

PubMed2005

Magnetic resonance imaging reveals functional diversity of the vasculature in benign and malignant breast lesions.

BACKGROUND: Tumor perfusion through the microvascular network can be imaged noninvasively by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The objective of the current study was to quantify the microvascular perfusion parameters in various human breast lesions and to determine whether they varied between benign lesions and malignancy and whether they were altered with increased invasiveness. METHODS: Perfusion parameters in 22 benign fibrocystic changes, 15 ductal carcinomas in situ (DCIS), 30 infiltrating ductal carcinomas (IDC), and 22 fibroadenomas were measured using high-resolution DCE-MRI. Pixel-by-pixel image analysis yielded parametric images of two perfusion indicators: the influx transcapillary transfer constant (k(trans)) and the efflux transcapillary rate constant (k(ep)). Correlations of lesion type and perfusion parameters were calculated using Spearman correlation. Logistic regression analysis evaluated the best predictors of the kinetic parameters that differentiate between IDC and benign lesions. RESULTS: The perfusion parameters exhibited a progressive increase from benign fibrocystic changes to DCIS and IDC, with a significant correlation between lesion type and the parameters' values (range of correlation coefficients, 0.56-0.76; P < 0.0001). In addition, k(trans) increased from low-grade DCIS to high-grade DCIS. Fibroadenomas were characterized uniquely by high k(trans) but low k(ep). Stepwise logistic regression selected k(trans) as the best predictor for distinguishing benign fibrocystic changes from IDC, yielding 93% sensitivity and 96% specificity. CONCLUSIONS: The microvascular perfusion parameters in breast lesions were elevated with invasiveness. Quantification of these parameters using high-resolution DCE-MRI was helpful for differentiating between breast lesions and should improve breast carcinoma diagnosis.

Breast Neoplasms↗

PubMed2005

Direct detection of brain acetylcholine synthesis by magnetic resonance spectroscopy.

The cholinergic system is an important modulatory neurotransmitter system in the brain. Changes in acetylcholine concentration have been previously determined directly in animal models and human brain biopsy specimens, and indirectly, by the effects of drugs, in living humans. Here, we developed a method for direct determination of acetylcholine synthesis in living brain tissue. The method is based on administration of choline, enriched with carbon-13 (stable isotope) in the two methylene positions, and detection of labeled acetylcholine and all other metabolic fates of choline, by carbon-13 magnetic resonance spectroscopy. We tested this method in rat brain slices and found it to be specific for acetylcholine synthesis in both the cortex and hippocampus. This method is potentially useful as a research tool for exploring the cholinergic system role in cognitive processes and memory storage as well as in diseases in which the malfunction of the cholinergic system has been implicated.

Acetylcholine↗

PubMed2005

Sodium magnetic resonance imaging of diuresis: spatial and kinetic response.

Renal function is highly correlated with the sodium concentration gradient along the corticomedullary axis. The application of 3D high-resolution sodium magnetic resonance imaging (MRI) provided a means to quantify in vivo the spatial and temporal changes in renal tissue sodium concentration under normal and diuretic conditions. A detailed, pixel-by-pixel analysis of the intact rat kidney sodium MR images yielded a quantitative measure of the corticomedullary sodium gradient before and at early and later times after the administration of two distinct diuretic agents, furosemide and mannitol. Furosemide, a loop diuretic, induced a fivefold reduction in the cortical-outer medullary sodium gradient, whereas mannitol, an osmotic diuretic, did not affect this gradient. Both diuretics induced a 50% decrease in the sodium concentration of the inner medulla; however, mannitol exerted its effect twice as fast as furosemide with a 2.5-min exponential decay constant. These specific changes were attributed to the different mechanism of action and site of activity of each diuretic agent. Thus, high-resolution (23)Na MRI offers a unique, noninvasive tool for functional imaging of the kidney physiology.

Analysis of Variance↗

PubMed2004

High-resolution magnetic resonance imaging of disparities in the transcapillary transfer rates in orthotopically inoculated invasive breast tumors.

In vivo mapping of the transcapillary fluxes in tumors can help predict the efficacy of delivery of blood-borne anticancer drugs. These fluxes are primarily affected by the vascular permeability and the pressure gradients across the blood vessels' walls. We describe herein high-resolution dynamic contrast-enhanced magnetic resonance imaging of the influx and outflux transcapillary transfer rates in vivo in invasive MDA-MB-231 tumors orthotopically inoculated in severe combined immunodeficient mice. The tumors were noted for rapid growth, impaired drainage of fluid, and subsequent formation of cysts. Consequently, the time evolution of the contrast enhancement, induced by i.v. injection of Gadolinium diethylene-triamine-penta-acetate, exhibited two distinct patterns: transcapillary transfer in the cellular regions and simple diffusion in the cyst fluid. Both processes were analyzed at pixel resolution applying to each a physiological model and a corresponding algorithm. In the cellular region, the influx and outflux transcapillary transfer rates decreased during tumor growth; however, an increased disparity between the transfer constants was observed, with the outflux rate exceeding the influx rate. This quantitative spatial and temporal mapping of this disparity can provide a means to assess the physiological barriers to tracer delivery. It is hypothesized that both the increased disparity in transcapillary transfer rates and impaired fluid drainage in these tumors could arise from the development of interstitial hypertension.

Animals↗

PubMed2004

Ultrafast 2D NMR spectroscopy using sinusoidal gradients: principles and ex vivo brain investigations.

A new methodology capable of delivering complete 2D NMR spectra within a single scan was recently introduced. The resulting potential gain in time resolution could open new opportunities for in vivo spectroscopy, provided that the technical demands of the methodology are satisfied by the corresponding hardware. Foremost among these demands are the relatively short switching times expected from the applied gradient-echo trains. These rapid transitions may be particularly difficult to accomplish on imaging systems. As a step toward solving this problem, we assessed the possibility of replacing the square-wave gradient train currently used during the course of the acquisition by a shaped sinusoidal gradient. Examples of the implementation of this protocol are given, and successful ultrafast acquisitions of 2D NMR spectra with suitable spectral widths on a microimaging probe (for both phantom solutions and ex vivo mouse brains) are demonstrated.

Animals↗

PubMed2004

Water diffusion in the different microenvironments of breast cancer.

The parameters that characterize the intricate water diffusion in tumors may serve to reveal their distinct pathology. Specifically, the application of diffusion magnetic resonance imaging (MRI) can aid in characterizing breast cancer, as well as monitoring response to therapy. We present here a non-invasive, quantitative MRI investigation, at high spatial resolution, of water diffusion in hormonal dependent MCF7 breast tumors implanted orthotopically in immunodeficient mice. Distinctive MRI protocols were designed in this study, utilizing a broad range of diffusion times and diffusion gradient strengths. Application of these protocols allowed water diffusion in the tissue extracellular and intracellular compartments to be distinguished, and the effect of restricted diffusion and water exchange on the water diffusion in these compartments to be evaluated. Pixel-by-pixel analysis yielded parametric maps of the estimated volume fraction and apparent diffusion coefficient of each compartment. The diffusion of the water in the extracellular microenvironment was approximately two fold slower than that of free water, and in the intracellular compartment was about one order of magnitude slower than that of free water and demonstrated restriction of water diffusion at long diffusion times. Mapping of the water fraction in each compartment was further employed to monitor changes during tumor progression and to assess tumor response to hormonal manipulation with a new antiestrogenic drug, tamoxifen methiodide (TMI). It was found that, in parallel to the growth arrest by this drug, the volume fraction of the slowly diffusing water increased, suggesting a TMI-induced cell swelling. This study can serve as a basis for extending diffusion breast MRI in the clinical setting.

Animals↗

PubMed2004

Functional sodium magnetic resonance imaging of the intact rat kidney.

BACKGROUND: Renal fluid homeostasis depends to a large extent on the sodium concentration gradient along the corticomedullary axis. The spatial distribution and extent of this gradient were previously determined by invasive methods, which yielded a range of results. We demonstrate here the capacity of sodium magnetic resonance imaging (MRI) to quantify non-invasively renal sodium distribution in the intact kidney. METHODS: Sodium MRI was applied to study normal, diuretic, and obstructed rat kidneys in vivo. The images were recorded at 4.7 Tesla using a 3-dimensional gradient echo sequence, with high spatial and temporal resolution. The tissue sodium concentration (TSC) was obtained by taking into account the measured nuclear relaxation rates and MRI visibility relative to a reference saline solution. RESULTS: The corticomedullary sodium gradient increased linearly from the cortex to the inner medulla by approximately 31 mmol/L/mm, from a TSC of approximately 60 mmol/L to approximately 360 mmol/L. Furosemide induced a 50% reduction in the inner-medulla sodium and a 25% increase in the cortical sodium. The kinetics of these changes was related to the specific site and mechanism of the loop diuretic. Distinct profiles of the sodium gradient were observed in acute obstructed kidneys, as well as spontaneously obstructed kidneys. The changes in the sodium gradient correlated with the extent of damage and the residual function of the kidneys. CONCLUSION: Quantitative assessment of the renal corticomedullary sodium gradient by high resolution sodium MRI may help verify new aspects of the kidney concentrating mechanism and serve as a non-invasive diagnostic method of renal function.

Acute Disease↗

PubMed2003

Glycolysis and glucose transporter 1 as markers of response to hormonal therapy in breast cancer.

Estrogen plays a key role in the development and progression of breast cancer; hence, antiestrogens, such as tamoxifen, have a marked impact on the treatment and outcome of breast cancer patients. Estrogen-induced growth requires continuous replenishment of energy, predominantly generated by glycolysis. Previous work from this laboratory demonstrated estrogen induction and tamoxifen inhibition of glycolysis in MCF7 human breast cancer cells in vitro (Furman et al., J Steroid Biochem Mol Biol 1992;43:189-95). We present here studies of estrogen vs. tamoxifen regulation of glycolysis in orthotopic MCF7 human breast cancer xenografts in vivo. In addition we investigated mediation of this metabolic regulation through glucose transporter 1, in the same cells, in vitro, as well as in 2 other hormone-responsive human breast cancer cells. Tumor response and glycolysis were monitored noninvasively by means of magnetic resonance imaging and 13C spectroscopy, respectively. During estrogen-stimulated tumor growth (from approximately 0.5 to approximately 1.3 cm3 in 10 days), the rate of glucose metabolism through glycolysis in vivo was high at 40 +/- 4 micromole/g/min. However, treatment for 10 days with tamoxifen induced growth arrest and a concomitant decrease of 2-fold in the rate of glycolysis. In congruence, glucose transporter 1 expression was stimulated by estrogen, reaching after 72 hr a 2- to 3-fold higher level of expression relative to that in tamoxifen-treated cells. Thus, estrogen-induced changes in glycolysis appeared to be mediated via its regulation of glucose transporter 1 expression. The in vivo monitoring of glycolysis may serve as a tool to expose hormonal regulation of glucose transporter 1 expression in breast cancer tumors, as well as to assess response to hormonal therapy.

Animals↗

PubMed2003

Magnetic resonance imaging of tumor vasculature.

Angiogenic activity and formation of a vascular network facilitate tumor perfusion and play a critical role in tumor growth and metastasis. Tumor vasculature may be visualized by means of parametric imaging of specific morphological and physiological characteristics that collectively describe its properties. In this review, we describe advanced magnetic resonance imaging (MRI) techniques that have been developed in order to image and quantify the distribution of tumor vasculature throughout the tumor and characterize its function. These techniques have been used to monitor changes in the magnetic resonance signal intensity of tissue water hydrogens generated by intrinsic effects, as well as by exogenous contrast agents administered into the blood circulation. We further describe specific applications of magnetic resonance imaging using a contrast agent, gadolinium diethylene triamine penta-acetic acid (GdDTPA), which has long been approved for clinical use. Examples include studies of the vascular properties of breast cancer tumors and metastases in animal models, as well as of breast cancer vasculature in patients. We also discuss the use of MRI to improve breast cancer diagnosis in humans by quantifying the permeability of the tumor vasculature. By maximizing the spatial resolution of the images in both animal and human studies, the capacity of magnetic resonance imaging to enhance our understanding of the processes regulating tumor angiogenesis, and improve the diagnosis of cancer, could be clearly demonstrated.

Animals↗

PubMed2002

Choline in the aging brain.

Proton magnetic resonance spectroscopy has been increasingly utilized in brain research to monitor non-invasively metabolites such as N-acetyl aspartate (NAA), creatine (Cr) and choline (Cho). We present here studies of the effect of aging on the ratios of these metabolites measured in the rat brain in vivo and on choline transport and lipid synthesis in rat brain slices, in vitro. The in vivo studies indicated that the ratios of Cho/NAA and Cho/Cr increased in the aged hippocampus, whereas the ratio of Cr/NAA was similar in the aged and adult hippocampus. These three ratios remained similar in the cortex of adult and aged rats. The in vitro studies revealed that in the aged cortex and the aged hippocampus the activity of the low-affinity choline uptake increased, possibly compensating for a decrease in the high-affinity uptake activity and the rate of choline diffusion. The incorporation of choline into phospholipids exhibited high and low affinity kinetics which were not modified by aging.

Aging↗

PubMed2002

Hormonal regulation of VEGF in orthotopic MCF7 human breast cancer.

Vascular endothelial growth factor (VEGF) mRNA and protein levels were higher in MCF7 breast cancer cells and orthotopic tumors after treatment with tamoxifen, as compared with treatment with estrogen. Accordingly, tumor vascular permeability, evaluated in vivo from contrast-enhanced magnetic resonance imaging, was elevated during treatment with tamoxifen. The results indicate that estrogen regulates angiogenesis in MCF7 tumors by maintaining VEGF at levels sufficient for the generation of functional microcapillaries and consequently facilitates tumor growth. During tamoxifen treatment, estrogen regulation is removed, and VEGF increases to levels that enhance markedly vascular permeability and reduce their perfusion function, leading to inhibition of tumor progression.

Antineoplastic Agents, Hormonal↗

PubMed2002

Metabolic markers of breast cancer: enhanced choline metabolism and reduced choline-ether-phospholipid synthesis.

Specific genetic alterations during malignant transformation may induce the synthesis and breakdown of choline phospholipids, mediating transduction of mitogenic signals. The high level of water-soluble choline metabolites in cancerous breast tumors, relative to benign lesions and normal breast tissue, has been used as a diagnostic marker of malignancy. To unravel the biochemical pathways underlying this phenomenon, we used tracer kinetics and 13C and 31P magnetic resonance spectroscopy to compare choline transport, routing, and metabolism to phospholipids in primary cultures of human mammary epithelial cells and in MCF7 human breast cancer cells. The rate of choline transport under physiological choline concentrations was 2-fold higher in the cancer cells. The phosphorylation of choline to phosphocholine and oxidation of choline to betaine yielded 10-fold higher levels of these metabolites in the cancer cells. However, additional incorporation of choline to phosphatidylcholine was similar in both cell types. Thus, enhanced choline transport and augmented synthesis of phosphocholine and betaine are dominant pathways responsible for the elevated presence of choline metabolites in cancerous breast tumors. Uniquely, reduced levels and synthesis of a choline-ether-phospholipid may also serve as a metabolic marker of breast cancer.

Betaine↗

PubMed2002

Parametric imaging of tumor perfusion using flow- and permeability-limited tracers.

PURPOSE: To quantitatively evaluate the spatial distribution of flow- and permeability-limited perfusion in MCF7 human breast cancer tumors orthotopically implanted in CD1-NU mice. MATERIALS AND METHODS: Flow-limited perfusion was derived from (2)H-MRI recorded before and after infusion of deuterated water. Permeability-limited perfusion was evaluated from GdDTPA-enhanced (1)H-MRI. RESULTS: The dominant processes in tumor perfusion, namely blood flow and capillary permeability, were mapped in orthotopically implanted MCF7 human breast cancer tumors. The dynamic data were processed according to physiological models, yielding parametric maps of intravascular volume fraction, water perfusion rate, GdDTPA permeability rate constant, and extracellular volume fraction accessible to GdDTPA. The maps exhibited the heterogeneous distribution of each perfusion parameter. Most of the tumor tissue (> or =95%) was perfused with HDO, while GdDTPA was perfused in only about 50% of it. In most loci the perfusion rate was limited by capillary permeability to GdDTPA. CONCLUSION: The results demonstrated the instructive value of tracers with different properties used in conjunction to achieve a deeper understanding of tumor perfusion capacity. This study offers tools for the accurate, noninvasive evaluation of drug delivery efficacy.

Animals↗

PubMed2002

Parametric imaging of tumor perfusion with deuterium magnetic resonance imaging.

Imaging of the vasculature and its functioning over the entire lesion may significantly aid in cancer diagnosis, assessment of prognosis, and therapeutic evaluation. In the current study we present a dynamic three-dimensional deuterium magnetic resonance imaging method that determines the intravascular volume fraction and water perfusion rate at a resolution of 2 mm(2)/pixel. The method was tested and utilized to characterize the vasculature of orthotopic MCF7 human breast cancer tumors in CD1-NU athymic mice. A new algorithm based on Patlak's kinetic model was developed to analyze the dynamic images acquired during and after termination of infusion with deuterated water. The resulting parametric maps spanned a wide range from 0.4 to 35.2% for the intravascular volume fraction and from 4 x 10(-6) to 3.9 x 10(-3) min(-1) for the perfusion rate and exhibited high intratumoral and intertumoral heterogeneity at both parameters. The intravascular volume fraction did not correlate with the corresponding perfusion rate, demonstrating the irregular outgrowth of tumor neovascularization. Averaging the data or analyzing at spatially degraded resolution completely masked the presence of both "hot spots" and hypoxic loci, highlighting the critical importance of high spatial resolution. The method is applicable to other types of tumors and animal models and may be extended to humans.

Algorithms↗