Clinical utility of FDG uptake within reticuloendothelial system on F-18 FDG PET/CT for prediction of tumor recurrence in breast cancer.

BACKGROUND: The aim of this study was to investigate the metabolism of the spleen, bone marrow (BM), and liver from preoperative F-18 FDG PET/CT scans for the prediction of recurrence in breast cancer. METHODS: We retrospectively included 153 patients diagnosed with invasive ductal carcinoma (IDC) of the breast who underwent preoperative F-18 FDG PET/CT scan and a curative operation. The mean standardized uptake value (SUVmean) of the spleen, liver, and BM and maximum SUV (SUVmax) of primary tumors were measured. The relationships between spleen, BM, and liver metabolism and clinicopathologic parameters were evaluated, and possible prognostic parameters predicting recurrence were assessed using disease-free survival (DFS). RESULTS: Spleen SUVmean was significantly correlated with primary tumor SUVmax, pathologic T (pT) stage, and histologic grade of primary tumor. BM SUVmean also showed a positive correlation with primary tumor SUVmax. Spleen SUVmean were significantly associated with recurrence from binary logistic regression analysis (P = 0.004). Spleen, BM, liver, and primary tumor SUVs were all significant prognostic factors for DFS in univariate Cox regression analysis (all P<0.024). Among all PET parameters analyzed, spleen SUVmean ≥ 2.21 (P = 0.032) was in the multivariable analysis the powerful poor prognostic factor predicting DFS that was independent of other clinicopathological features like T stage (pT >2; P = 0.009) and estrogen receptor (ER) status (ER negativity; P = 0.001). CONCLUSION: Splenic metabolism together with pT stage and ER status was an independent prognostic factor for predicting recurrence in breast cancer. Metabolic activity of reticuloendothelial system such as spleen, liver or BM on preoperative F-18 FDG PET/CT can be a meritorious imaging factor for discriminating patients with IDC that require adjunctive therapy to prevent recurrence.

An in-vivo pilot study into the effects of FDG-mNP in cancer in mice.

PURPOSE: Previously, fluorodeoxy glucose conjugated magnetite nanoparticles (FDG-mNPs) injected into cancer cells in conjunction with the application of magnetic hyperthermia have shown promise in new FDG-mNPs applications. The aim of this study was to determine potential toxic or unwanted effects involving both tumour cells and normal tissue in other organs when FDG-mNPs are administered intravenously or intratumourally in mice. MATERIALS AND METHODS: FDG-mNPs were synthesized. A group of six prostate-tumour bearing mice were injected with 23.42 mg/ml FDG-mNPs (intravenous injection, n = 3; intratumoural injection into the prostate tumour, n = 3). Mice were euthanized and histological sampling of tissue was conducted for the prostate tumour, as well as for lungs, lymph nodes, liver, kidneys, spleen, and brain, at 1 hour (n = 2) and 7 days (n = 4) post-injection. A second group of two normal (non-cancerous) mice received the same injection intravenously into the tail vein and were euthanised at 3 and 6 months post-injection, respectively, to investigate if FDG-mNPs remained in organs at those time points. RESULTS: In prostate-tumour bearing mice, FDG-mNPs concentrated in the prostate tumour, while relatively small amounts were found in the organs of other tissues, particularly the spleen and the liver; FDG-mNP concentrations decreased over time in all tissues. In normal mice, no detrimental effects were found in either mouse at 3 or 6 months. CONCLUSION: Intravenous or intratumoural FDG-mNPs can be safely administered for effective cancer cell destruction. Further research on the clinical utility of FDG-mNPs will be conducted by applying hyperthermia in conjunction with FDG-mNPs in mice.

Hypoxia is important in F­18 FDG accumulation in thecoma­fibroma tumors on F­18 FDG PET/CT scans.

Several studies have noted benign thecoma­fibroma tumors with positive F­18 fluorodeoxyglucose (FDG) accumulation mimicking malignant ovarian tumors following F­18 FDG positron emission tomography (PET). The present study analyzed four cases with false­positive F­18 FDG PET/computed tomography (CT) diagnoses of thecoma­fibroma tumors as malignant tumors due to F­18 FDG accumulation, compared with eight cases of FDG­positive ovarian cancers and two cases of FDG­negative fibromas. Hypoxia inducible factor (HIF)­1α expression was examined in the six thecoma­fibroma tumors using reverse transcription­polymerase chain reaction (RT­PCR). The four F­18 FDG­positive cases exhibited higher cellularity, maximum standard uptake and signal intensity on T2­weighted imaging, and gadolinium (Gd) enhancement using magnetic resonance imaging than the two FDG-negative fibroma cases. In the F­18 FDG­positive thecoma­fibroma group, Ki­67 expression was low and LAT1 expression was not identified, ruling out the diagnosis and potential for malignancy. However, considerable glucose transporter 1, HIF­1α, and vascular endothelial growth factor expression was observed. HIF­1α expression was elevated in all four false­positive cases by RT­PCR. From these results, it was hypothesized that hypoxia due to elevated cellularity may stimulate HIF­1α expression and be associated with F­18 FDG accumulation in F­18­positive thecoma­fibroma tumors.

[18F]FDG Uptake in the Aortic Wall Smooth Muscle of Atherosclerotic Plaques in the Simian Atherosclerosis Model.

Atherosclerosis is a self-sustaining inflammatory fibroproliferative disease that progresses in discrete stages and involves a number of cell types and effector molecules. Recently, [18F]fluoro-2-deoxy-D-glucose- ([18F]FDG-) positron emission tomography (PET) has been suggested as a tool to evaluate atherosclerotic plaques by detecting accumulated macrophages associated with inflammation progress. However, at the cellular level, it remains unknown whether only macrophages exhibit high uptake of [18F]FDG. To identify the cellular origin of [18F]FDG uptake in atherosclerotic plaques, we developed a simian atherosclerosis model and performed PET and ex vivo macro- and micro-autoradiography (ARG). Increased [18F]FDG uptake in the aortic wall was observed in high-cholesterol diet-treated monkeys and WHHL rabbits. Macro-ARG of [18F]FDG in aortic sections showed that [18F]FDG was accumulated in the media and intima in the simian model as similar to that in WHHL rabbits. Combined analysis of micro-ARG with immunohistochemistry in the simian atherosclerosis model revealed that most cellular [18F]FDG uptake observed in the media was derived not only from the infiltrated macrophages in atherosclerotic plaques but also from the smooth muscle cells (SMCs) of the aortic wall in atherosclerotic lesions.

Establishment and characterization of a novel orthotopic mouse model for human uterine sarcoma with different metastatic potentials.

Uterine sarcomas are rare and aggressive gynecologic tumors with a poor prognosis because of recurrence and metastasis. However, the mechanisms of uterine sarcoma metastasis are largely unknown. To investigate this mechanism, we developed a novel uterine sarcoma tissue-derived orthotopic and metastatic model in KSN nude mice using a green fluorescent protein stably expressed uterine sarcoma cell line, MES-SA. Histological analysis showed that all orthotopic primary tumors were undifferentiated sarcoma. Primary tumors were characterized by high (18)F-fluorodeoxyglucose uptake with a positive correlation to the number of pulmonary metastases. In addition, we generated uterine sarcoma cell sublines with high or low metastatic potentials by serial in vivo selection. Microarray analysis between orthotopic tumors with high and low metastatic potentials revealed differential expression of genes related to cell proliferation and migration (TNNT1, COL1A2, and ZIC1). Our model would be useful to compensate for the limited clinical cases of uterine sarcoma and to investigate the molecular mechanisms of metastatic uterine sarcoma.

A real-time follow-up of photodynamic therapy during PET imaging.

PURPOSE: To monitor a real-time follow-up of tumor response to photodynamic therapy (PDT) by dynamic 2-deoxy-2-[(18)F]fluoro-d-glucose ((18)FDG) and positron emission tomography (PET) using two photosensitizing drugs in vivo, and to assess their mechanisms of action. METHODS: Two types of photosensitizers with different action mechanisms were used in rats implanted with two tumors: AlPcS4 mainly affecting the tumor vascular system, and ZnPcS2 largely inducing direct cell kill. Twenty-four hours after administration of either photosensitizer, one tumor served as control while the other was treated with red light during 30min within the 2h PET imaging by infusion of (18)FDG. The usual two-tissue compartment kinetic model was modified to take into account the perturbation of the treatment during imaging. RESULTS: The illumination of the tumors during PET imaging provoked a net decrease of (18)FDG uptake in tumors treated with AlPcS4 and a near total absence of (18)FDG uptake in tumors treated with ZnPcS2. After the end of illumination, the tumors regained (18)FDG uptake with a more pronounced uptake in the tumors treated with ZnPcS2. The rate constant values of the new (18)FDG kinetic model reflected the response of the tumors to the treatment in both photosensitizers. CONCLUSIONS: Dynamic PET imaging can be used to quantitatively assess in vivo and in real-time the response of tumors to treatments. It is demonstrated that the 30min of treatment was not sufficient to reduce the activity of the tumors. The technique could be extended to directly monitor the effects of drugs in vivo.

Mapping phosphorylation rate of fluoro-deoxy-glucose in rat brain by (19)F chemical shift imaging.

(19)F magnetic resonance spectroscopy (MRS) studies of 2-fluoro-2-deoxy-d-glucose (FDG) and 2-fluoro-2-deoxy-d-glucose-6-phosphate (FDG-6P) can be used for directly assessing total glucose metabolism in vivo. To date, (19)F MRS measurements of FDG phosphorylation in the brain have either been achieved ex vivo from extracted tissue or in vivo by unusually long acquisition times. Electrophysiological and functional magnetic resonance imaging (fMRI) measurements indicate that FDG doses up to 500 mg/kg can be tolerated with minimal side effects on cerebral physiology and evoked fMRI-BOLD responses to forepaw stimulation. In halothane-anesthetized rats, we report localized in vivo detection and separation of FDG and FDG-6P MRS signals with (19)F 2D chemical shift imaging (CSI) at 11.7 T. A metabolic model based on reversible transport between plasma and brain tissue, which included a non-saturable plasma to tissue component, was used to calculate spatial distribution of FDG and FDG-6P concentrations in rat brain. In addition, spatial distribution of rate constants and metabolic fluxes of FDG to FDG-6P conversion were estimated. Mapping the rate of FDG to FDG-6P conversion by (19)F CSI provides an MR methodology that could impact other in vivo applications such as characterization of tumor pathophysiology.

Quantitative assessment of cerebral glucose metabolic rates after blood-brain barrier disruption induced by focused ultrasound using FDG-MicroPET.

The goal of this study was to evaluate the pharmacokinetics of (18)F-2-fluoro-2-deoxy-d-glucose ((18)F-FDG) and the expression of glucose transporter 1 (GLUT1) protein after blood-brain barrier (BBB) disruption of normal rat brains by focused ultrasound (FUS). After delivery of an intravenous bolus of ~37 MBq (1 mCi) (18)F-FDG, dynamic positron emission tomography scans were performed on rats with normal brains and those whose BBBs had been disrupted by FUS. Arterial blood sampling was collected throughout the scanning procedure. A 2-tissue compartmental model was used to estimate (18)F-FDG kinetic parameters in brain tissues. The rate constants Ki, K1, and k3 were assumed to characterize the uptake, transport, and hexokinase activity, respectively, of (18)F-FDG. The uptake of (18)F-FDG in brains significantly decreased immediately after the blood-brain barrier was disrupted. At the same time, the derived values of Ki, K1, and k3 for the sonicated brains were significantly lower than those for the control brains. In agreement with the reduction in glucose, Western blot analyses confirmed that focused ultrasound exposure significantly reduced the expression of GLUT1 protein in the brains. Furthermore, the effect of focused ultrasound on glucose uptake was transient and reversible 24h after sonication. Our results indicate that focused ultrasound may inhibit GLUT1 expression to decrease the glucose uptake in brain tissue during the period of BBB disruption.

Unsupervised analysis of small animal dynamic Cerenkov luminescence imaging.

Clustering analysis (CA) and principal component analysis (PCA) were applied to dynamic Cerenkov luminescence images (dCLI). In order to investigate the performances of the proposed approaches, two distinct dynamic data sets obtained by injecting mice with (32)P-ATP and (18)F-FDG were acquired using the IVIS 200 optical imager. The k-means clustering algorithm has been applied to dCLI and was implemented using interactive data language 8.1. We show that cluster analysis allows us to obtain good agreement between the clustered and the corresponding emission regions like the bladder, the liver, and the tumor. We also show a good correspondence between the time activity curves of the different regions obtained by using CA and manual region of interest analysis on dCLIT and PCA images. We conclude that CA provides an automatic unsupervised method for the analysis of preclinical dynamic Cerenkov luminescence image data.

SLC37A1 and SLC37A2 are phosphate-linked, glucose-6-phosphate antiporters.

Blood glucose homeostasis between meals depends upon production of glucose within the endoplasmic reticulum (ER) of the liver and kidney by hydrolysis of glucose-6-phosphate (G6P) into glucose and phosphate (P(i)). This reaction depends on coupling the G6P transporter (G6PT) with glucose-6-phosphatase-α (G6Pase-α). Only one G6PT, also known as SLC37A4, has been characterized, and it acts as a P(i)-linked G6P antiporter. The other three SLC37 family members, predicted to be sugar-phosphate:P(i) exchangers, have not been characterized functionally. Using reconstituted proteoliposomes, we examine the antiporter activity of the other SLC37 members along with their ability to couple with G6Pase-α. G6PT- and mock-proteoliposomes are used as positive and negative controls, respectively. We show that SLC37A1 and SLC37A2 are ER-associated, P(i)-linked antiporters, that can transport G6P. Unlike G6PT, neither is sensitive to chlorogenic acid, a competitive inhibitor of physiological ER G6P transport, and neither couples to G6Pase-α. We conclude that three of the four SLC37 family members are functional sugar-phosphate antiporters. However, only G6PT/SLC37A4 matches the characteristics of the physiological ER G6P transporter, suggesting the other SLC37 proteins have roles independent of blood glucose homeostasis.

Deciphering the role of glucosamine-6-phosphate in the riboswitch action of glmS ribozyme.

The GlmS ribozyme is believed to exploit a general acid-base catalytic mechanism in the presence of glucosamine-6-phosphate (GlcN6P) to accelerate self-cleavage by approximately six orders of magnitude. The general acid and general base are not known, and the role of the GlcN6P cofactor is even less well understood. The amine group of GlcN6P has the ability to either accept or donate a proton and could therefore potentially act as an acid or a base. In order to decipher the role of GlcN6P in the self-cleavage of glmS, we have determined the preferred protonation state of the amine group in the wild-type and an inactive G40A mutant using molecular dynamics simulations and free energy calculations. Here we show that, upon binding of GlcN6P to wild-type glmS, the pK(a) of the amine moiety is altered by the active site environment, decreasing by about 2.2 from a solution pK(a) of about 8.2. On the other hand, we show that the pK(a) of the amine group slightly increases to about 8.4 upon binding to the G40A inactive mutant of glmS. These results suggest that GlcN6P acts as a general acid in the self-cleavage of glmS. Upon binding to glmS, GlcN6P can easily release a proton to the 5'-oxygen of G1 during self-cleavage of the backbone phosphodiester bond. However, in the G40A inactive mutant of glmS, the results suggest that the ability of GlcN6P to easily release its proton is diminished, in addition to the possible lack of G40 as an effective base.

Effects of vitamin E supplementation on plasma membrane permeabilization and fluidization induced by chlorpromazine in the rat brain.

Neurotransmitter receptors play a key role in most research on antipsychotic drugs, but little is known about the effects of these drugs on the plasma membrane in the central nervous system. Therefore, we investigated whether chlorpromazine (CPZ), a typical phenothiazine antipsychotic drug, affects the plasma membrane integrity in the rat brain, and if so, whether these membrane alterations can be prevented by dietary supplementation with vitamin E, which has been shown to be an antioxidant and also a membrane-stabilizer. Leakage of [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG)-6-phosphate from rat striatal slices and decrease in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy were used as indexes for plasma membrane permeabilization and fluidization, respectively. CPZ induced leakage of [(18)F]FDG-6-phosphate from striatal slices, and the leakage was delayed in the vitamin E-supplemented group compared to that in the normal diet group. The decrease in plasma membrane anisotropy induced by CPZ was significantly attenuated by vitamin E supplementation. Chronic treatment with alpha-phenyl-N-tert-butyl nitrone, a free radical scavenger, had no effect on CPZ-induced plasma membrane permeabilization, and the treatment with CPZ did not induce lipid peroxidation. CPZ can reduce plasma membrane integrity in the brain, and this reduction can be prevented by vitamin E via its membrane-stabilizing properties, not via its antioxidant activity.

Lactate-induced translocation of GLUT1 and GLUT4 is not mediated by the phosphatidyl-inositol-3-kinase pathway in the rat heart.

We have determined the effect of lactate on the translocation of GLUT1 and GLUT4 and on the myocardial uptake and phosphorylation of the glucose analogues 2-deoxy-D-glucose (DG) and 2-18F-fluoro-2-deoxy-D-glucose (18FDG). The involvement of phosphatidyl-inositol-3-kinase (PI3K) in this translocation was determined using wortmannin. Hearts from fed and fasted male Wistar rats were perfused in the presence of 11 mM glucose +/- 10 mM lactate for two hours and the distribution of glucose transporters was determined using Western blot techniques. Two other groups of hearts from fed animals were perfused in the presence of 11 mM glucose +/- 10 mM lactate for two hours followed by perfusion for a further 30 minutes in the presence of 4 mM 2-deoxy-D-glucose. Using 31P NMR spectroscopy, the accumulation of 2-deoxy-D-glucose-6-phosphate (DG6P) was monitored over time. Another group of hearts from fed animals was initially perfused in the presence of 11 mM glucose for 100 minutes and then the perfusate was changed to 11 mM glucose + 10 mM lactate for a further 120 minutes. Using PET, the accumulation of 2-18F-fluoro-deoxy-D-glucose-6-phosphate (18FDG6P) was monitored throughout the whole protocol. Lactate induced the translocation of both GLUT1 and GLUT4 to the plasma membrane (from 67 +/- 1% to 82 +/- 2% and from 16 +/- 1% to 28 +/- 2%, respectively (P < 0.05)) in hearts from fed animals; similar translocations were observed in hearts from fasted animals. Wortmannin did not inhibit the translocation of either GLUT1 or GLUT4. Glucose transporter translocation was accompanied by a significant inhibition of DG6P accumulation (4.24 +/- 0.68 vs. 1.50 +/- 0.38; P < 0.001) and a decrease in the rate of 18FDG6P accumulation. In conclusion, lactate causes translocation of GLUT1 and GLUT4 to the plasma membrane, via a non-PI3K-mediated pathway. Despite this externalisation of the GLUT transporters, a marked decrease in the accumulation of both DG6P and 18FDG6P was observed.

Cerebral hypoxia-ischemia in immature rats: involvement of mitochondrial permeability transition?

The aim of this study was to evaluate the involvement of mitochondrial membrane permeability transition (MPT) after hypoxia-ischemia (HI) in 7-day-old rats. [14C]2-deoxyglucose (DOG) was administered to controls, and at various time points after HI. MPT in the cerebral cortex was measured as entrapment of DOG-6-P in mitochondria. Another group of rats was treated with the MPT inhibitor cyclosporin A (CsA; 10-50 mg/kg i.p.) or vehicle before and after HI, and the effect on brain injury and mitochondrial respiration was evaluated. A significant increase in DOG-6-P entrapment in mitochondria indicated that MPT occurred in two phases: a primary MPT after 0-1.5 h and a secondary MPT after 6.5-8 h of reperfusion. However, CsA did not affect brain injury or mitochondrial respiration. The data suggest that MPT occurred after HI but does not provide evidence for its involvement in the development of injury.

PET: activation of cerebral blood flow and glucose metabolism.

Functional brain mapping based on the PET CBF and glucose metabolic methods remains an exceptionally productive approach for localizing brain function. The imaging techniques are remarkably standardized, and localization remains stable with a variety of data analysis methods (140,141). The methods are suitable for identifying functional reorganization in the setting of neurodegeneration, stroke, trauma, and the effects of epilepsy on cognition.

Nonradioisotope assay of glucose uptake activity in rat skeletal muscle using enzymatic measurement of 2-deoxyglucose 6-phosphate in vitro and in vivo.

We investigated a nonradioisotope method for the evaluation of glucose uptake activity using enzymatic measurement of 2-deoxyglucose 6-phosphate (2DG6P) content in isolated rat soleus muscle in vitro and in vivo. The 2DG6P content in isolated rat soleus muscle after incubation with 2-deoxyglucose (2DG) was increased in a dose-dependent manner by insulin (ED(50) = 0.6 mU/ml), the maximum response being about 5 times that of the basal content in vitro. This increment was completely abolished by wortmannin (100 nM), with no effect on basal 2DG6P content. An insulin-mimetic compound, vanadium, also increased 2DG6P content in a dose-dependent manner. In isolated soleus muscle of Zucker fa/fa rats, well known as an insulin-resistant model, insulin did not increase 2DG6P content. The 2DG6P content in rat soleus muscle increased after 2DG (3 mmol/kg) injection in vivo, and conversely, the 2DG concentration in plasma was decreased in a dose-dependent manner by insulin (ED(50) = 0.11 U/kg). The maximum response of the accumulation of 2DG6P in soleus muscle was about 4 times that of the basal content. This method could be useful for evaluating glucose uptake (transport plus phosphorylation) activity in soleus muscle in vitro and in vivo without using radioactive materials.

Fate of 2-deoxy-2-[18F]fluoro-D-glucose in control and diabetic rats.

Recent experiments conducted in vitro have documented a marked difference in the time course for D-[U-14C]glucose net uptake by pieces of pancreatic tissue versus isolated pancreatic islets. The present study aimed, therefore, at assessing whether the endocrine pancreas contributes to a detectable extent to the overall net uptake of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) by the pancreatic gland. For this purpose, the radioactive content of the pancreas was compared to that of plasma, erythrocytes, liver, brain, hypophysis and parotid gland 3 min, 15 min and 240 min after the intravenous injection of FDG to both control rats and animals injected with streptozotocin and later treated with insulin or not. In the control rats, the radioactive content (cpm/mg wet wt.) of erythrocytes was always lower than that of liver. In other organs, it displayed the following hierarchy pancreas < parotid < hypophysis < brain, the absolute values being either lower (3 min) or much higher (240 min) than in liver. In the diabetic rats, whether treated with insulin or not, the radioactive content of erythrocytes, pancreas, brain, hypophysis and parotid gland, relative to the paired value found in liver, was equal or lower than that of control rats when the animals were hyperglycemic and equal or higher than that of control rats when the animals became hypoglycemic as the result of intensive insulin treatment. Even only 3 min after the injection of FDG, and despite persistent hyperglycemia in the streptozotocin-injected and insulin-treated rats, the pancreas/ liver paired ratio in radioactive content failed to be significantly lower in the diabetic animals than in control rats. These findings indicate that 2-deoxy-2-[18F]fluoro-D-glucose is not a suitable tool to detect any preferential labelling of insulin-producing cells, relative to acinar cells, at least when considering only the total radioactive content of the pancreatic gland.