Head-to-head comparison of [68Ga]Ga-FAPI-04 and [18F]-FDG PET/CT in evaluating the extent of disease in gastric adenocarcinoma.

BACKGROUND: [18F]-Fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) may sometimes be suboptimal for imaging gastric adenocarcinoma. The recently introduced [68Ga]Ga-FAPI-04 (FAPI) PET/CT targets tumor stroma and has shown considerable potential in evaluating the extent of disease in a variety of tumors. METHODS: We performed a head-to-head prospective comparison of FAPI and FDG PET/CT in the same group of 13 patients with gastric adenocarcinoma who presented for either initial staging (n = 10) or restaging (n = 3) of disease. Lesion detection and maximum standardized uptake value (SUVmax) were compared between the two types of radiotracers. RESULTS: All ten primary gastric tumors were FAPI-positive (100% detection rate), whereas only five were also FDG-positive (50%). SUVmax was not significantly different, but the tumor-to-background ratio was higher for FAPI (mean, median, and range of 4.5, 3.2, and 0.8-9.7 for FDG and 12.9, 11.9, and 2.2-23.9 for FAPI, P = 0.007). The level of detection of regional lymph node involvement was comparable. FAPI showed a superior detection rate for peritoneal carcinomatosis (100% vs. none). Two patients with widespread peritoneal carcinomatosis underwent a follow-up FAPI scan after chemotherapy: one showed partial remission and the other showed progressive disease. CONCLUSIONS: The findings of this pilot study suggest that FAPI PET/CT outperforms FDG PET/CT in detecting both primary gastric adenocarcinoma and peritoneal carcinomatosis from gastric cancer. FAPI PET/CT also shows promise for monitoring response to treatment in patients with peritoneal carcinomatosis from gastric cancer; however, larger trials are needed to validate these preliminary findings.

Fine-tuning of the automated [18 F]PSMA-1007 radiosynthesis.

Radiolabeled prostate-specific membrane antigen (PSMA) targeting PET-tracers have become desirable radiopharmaceuticals for the imaging of prostate cancer (PC). Recently, the PET radiotracer [18 F]PSMA-1007 was introduced as an alternative to [68 Ga]Ga-PSMA-11, for staging and diagnosing biochemically recurrent PC. We incorporated a one-step procedure for [18 F]PSMA-1007 radiosynthesis, using both Synthra RNplus and GE TRACERlab FxFN automated modules, in accordance with the recently described radiolabeling procedure. Although the adapted [18 F]PSMA-1007 synthesis resulted in repeatable radiochemical yields (55 ± 5%, NDC), suboptimal radiochemical purities of 87 ± 8% were obtained using both modules. As described here, modifications made to the radiolabeling and the solid-phase extraction purification steps reduced synthesis time to 32 minutes and improved radiochemical purity to 96.10%, using both modules, without shearing the radiochemical yield.

Regulation of GLUT4 activity in myotubes by 3-O-methyl-d-glucose.

The rate of glucose influx to skeletal muscles is determined primarily by the number of functional units of glucose transporter-4 (GLUT4) in the myotube plasma membrane. The abundance of GLUT4 in the plasma membrane is tightly regulated by insulin or contractile activity, which employ distinct pathways to translocate GLUT4-rich vesicles from intracellular compartments. Various studies have indicated that GLUT4 intrinsic activity is also regulated by conformational changes and/or interactions with membrane components and intracellular proteins in the vicinity of the plasma membrane. Here we show that the non-metabolizable glucose analog 3-O-methyl-d-glucose (MeGlc) augmented the rate of hexose transport into myotubes by increasing GLUT4 intrinsic activity without altering the content of the transporter in the plasma membrane. This effect was not a consequence of ATP depletion or hyperosmolar stress and did not involve Akt/PKB or AMPK signal transduction pathways. MeGlc reduced the inhibitory potency (increased Ki) of indinavir, a selective inhibitor of GLUT4, in a dose-dependent manner. Kinetic analyses indicate that MeGlc induced changes in GLUT4 or GLUT4 complexes within the plasma membrane, which enhanced the hexose transport activity and reduced the potency of indinavir inhibition. Finally, we present a simple kinetic analysis for screening and discovering low molecular weight compounds that augment GLUT4 activity.

Beta cell response to nutrient overload involves phospholipid remodelling and lipid peroxidation.

AIMS/HYPOTHESIS: Membrane phospholipids are the major intracellular source for fatty acid-derived mediators, which regulate myriad cell functions. We showed previously that high glucose levels triggered the hydrolysis of polyunsaturated fatty acids from beta cell phospholipids. These fatty acids were subjected to free radical-catalysed peroxidation to generate the bioactive aldehyde 4-hydroxy-2E-nonenal (4-HNE). The latter activated the nuclear peroxisome proliferator-activated receptor-δ (PPARδ), which in turn augmented glucose-stimulated insulin secretion. The present study aimed at investigating the combined effects of glucose and fatty acid overload on phospholipid turnover and the subsequent generation of lipid mediators, which affect insulin secretion and beta cell viability. METHODS: INS-1E cells were incubated with increasing glucose concentrations (5-25 mmol/l) without or with palmitic acid (PA; 50-500 µmol/l) and taken for fatty acid-based lipidomic analysis and functional assays. Rat isolated islets of Langerhans were used similarly. RESULTS: PA was incorporated into membrane phospholipids in a concentration- and time-dependent manner; incorporation was highest at 25 mmol/l glucose. This was coupled to a rapid exchange with saturated, mono-unsaturated and polyunsaturated fatty acids. Importantly, released arachidonic acid and linoleic acid were subjected to peroxidation, resulting in the generation of 4-HNE, which further augmented insulin secretion by activating PPARδ in beta cells. However, this adaptive increase in insulin secretion was abolished at high glucose and PA levels, which induced endoplasmic reticulum stress, apoptosis and cell death. CONCLUSIONS/INTERPRETATION: These findings highlight a key role for phospholipid remodelling and fatty acid peroxidation in mediating adaptive and cytotoxic interactions induced by nutrient overload in beta cells.

Organic Cation Transporter-Mediated Accumulation of Quinolinium Salts in the LV Myocardium of Rodents.

PURPOSE: Quaternary ammonium salts have demonstrated marked accumulation in the left ventricular (LV) myocardium of rodents and swine. To investigate the mechanism underlying this uptake, the present study examined the interaction of [18F]fluoroethylquinolinium ([18F]FEtQ) with the family of organic cation transporters (OCTs). PROCEDURES: The cellular uptake of [18F]FEtQ into HEK293 cells, expressing human OCT1, -2, or -3 (HEK293-hOCT), and its inhibition by corticosterone was evaluated in vitro. The inhibitory effect of decynium 22 (D 22) in vivo was also studied, using PET/CT of HEK293-hOCT tumor-bearing mice. Furthermore, the distribution kinetics of [18F]FEtQ were determined in rats, with and without pre-administration of corticosterone, and following administration to a non-human primate (NHP). RESULTS: The accumulation of [18F]FEtQ in HEK293-hOCT cells was 15-20-fold higher than in control cells and could be inhibited by corticosterone. in vivo, the uptake of [18F]FEtQ in the LV myocardium of corticosterone-treated rats was significantly reduced compared to that of untreated animals. Similarly, following administration of D 22 to HEK293-hOCT tumor-bearing mice, the peak tumor uptake of [18F]FEtQ was reduced by 40-45 % compared to baseline. Contrary to the distinct accumulation of [18F]FEtQ in the LV myocardium of rats, no cardiac uptake was observed following its administration to a NHP. CONCLUSIONS: The quinolinium salt derivative [18F]FEtQ interacts with the family of OCTs, and this interaction could account, at least in part, for the increased uptake in the LV myocardium of rodents. Nonetheless, its low affinity for hOCT3 and the results of PET/CT imaging in a NHP indicate a limited clinical applicability as a radiopharmaceutical for cardiac and/or OCT imaging.

Development and preclinical evaluation of novel fluorinated ammonium salts for PET myocardial perfusion imaging.

We previously presented the radiolabeled ammonium salt [11C]-dimethyl diphenylammonium trifluoromethanesulfonate ([11C]DMDPA) as a potential novel PET-MPI agent. The current study aimed to increase the clinical applicability of PET-MPI by designing and synthesizing fluorinated ammonium salt derivatives. Four fluorinated DMDPA derivatives and two quinolinium salt analogs were radiolabeled. The dynamic distribution in vivo, following injection of each derivative into male SD rats, was evaluated using small-animal dedicated PET/CT. Organ uptake after injection of [18F]fluoroethylquinolinium acetate ([18F]FEtQ) was examined ex vivo. Four fluorinated DMDPA derivatives were synthesized, two were labeled with fluorine-18: [18F]fluoroethyl-methyldiphenylammonium trifluoromethanesulfonate ([18F]FEMDPA) and [18F]fluorobuthyl-methyldiphenylammonium trifluoromethanesulfonate ([18F]FBMDPA). The other two were labeled using carbon-11: [11C]methyl-(3-fluorophenyl)-methylphenylammonium trifluoromethanesulfonate ([11C]3-F-DMDPA) and [11C]methyl-(4-fluorophenyl)-methylphenylammonium trifluoromethanesulfonate ([11C]4-F-DMDPA). All four DMDPA derivatives exhibited significantly lower heart/liver radioactivity uptake ratios (0.6, 0.4, 0.7 and 0.6, respectively) compared to that of [11C]DMDPA (1.2). Conversely, the two radiolabeled quinolinium salt derivatives, [11C]methylquinolinium iodide ([11C]MeQ) and [18F]FEtQ demonstrated improved heart/liver ratios (2.0 and 1.3, respectively) with clear visualization of the left ventricle myocardium. Renal clearance was the major route of elimination. Among the fluorinated quaternary ammonium salts tested, [18F]FEtQ yielded the best images. Further studies are in progress to elucidate the underlying mechanism of its cardiac uptake.

[18F]-FDHT PET/CT as a tool for imaging androgen receptor expression in high-grade glioma.

BACKGROUND: G lioblastoma (GBM) is associated with poor overall survival. Recently, we showed that androgen receptor (AR) protein is overexpressed in 56% of GBM specimens and AR antagonists induced dose-dependent death in several GBM cell lines and significantly reduced tumor growth and prolonged the lifespan of mice implanted with human GBM. 16ß-18F-fluoro-5α-dihydrotestosterone ([18F]-FDHT) is a positron emission tomography (PET) tracer used to detect AR expression in prostate and breast cancers. This study was aimed at exploring the ability of [18F]-FDHT-PET to detect AR expression in high-grade gliomas. METHODS: Twelve patients with suspected high-grade glioma underwent a regular workup and additional dynamic and static [18F]-FDHT-PET/CT. Visual and quantitative analyses of [18 F]-FDHT kinetics in the tumor and normal brain were performed. Mean and maximum (max) standardized uptake values (SUVs) were determined in selected volumes of interest. The patients had surgery or biopsy after PET/CT. AR protein was analyzed in the tumor samples by western blot. Fold change in AR expression was calculated by densitometry analysis. Correlation between imaging and AR protein samples was determined. RESULTS: In six of the 12 patients, [18 F]-FDHT uptake was significantly higher in the tumor than in the normal brain. These patients also had increased AR protein expression within the tumor. Pearson correlation coefficient analysis for the tumor-to-control normal brain uptake ratio in terms of SUVmean versus AR protein expression was positive and significant (R = 0.84; P = .002). CONCLUSION: [18 F]-FDHT-PET/CT could identify increased AR expression in high-grade glioma.

Signaling and cytotoxic functions of 4-hydroxyalkenals.

The peroxidation of n-3 and n-6 polyunsaturated fatty acids (PUFAs) and of their hydroperoxy metabolites is a complex process. It is initiated by free oxygen radical-induced abstraction of a hydrogen atom from the lipid molecule followed by a series of nonenzymatic reactions that ultimately generate the reactive aldehyde species 4-hydroxyalkenals. The molecule 4-hydroxy-2E-hexenal (4-HHE) is generated by peroxidation of n-3 PUFAs, such as linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid. The aldehyde product 4-hydroxy-2E-nonenal (4-HNE) is the peroxidation product of n-6 PUFAs, such as arachidonic and linoleic acids and their 15-lipoxygenase metabolites, namely 15-hydroperoxyeicosatetraenoic acid (15-HpETE) and 13-hydroperoxyoctadecadienoic acid (13-HpODE). Another reactive peroxidation product is 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), which is derived from 12-hydroperoxyeicosatetraenoic acid (12-HpETE), the 12-lipoxygenase metabolite of arachidonic acid. Hydroxyalkenals, notably 4-HNE, have been implicated in various pathophysiological interactions due to their chemical reactivity and the formation of covalent adducts with macromolecules. The progressive accumulation of these adducts alters normal cell functions that can lead to cell death. The lipophilicity of these aldehydes positively correlates to their chemical reactivity. Nonetheless, at low and noncytotoxic concentrations, these molecules may function as signaling molecules in cells. This has been shown mostly for 4-HNE and to some extent for 4-HHE. The capacity of 4-HDDE to generate such "mixed signals" in cells has received less attention. This review addresses the origin and cellular functions of 4-hydroxyalkernals.

Head-to-Head Comparison of 68Ga-PSMA-11 with 18F-PSMA-1007 PET/CT in Staging Prostate Cancer Using Histopathology and Immunohistochemical Analysis as a Reference Standard.

18F-PSMA-1007 is a novel prostate-specific membrane antigen (PSMA)-based radiopharmaceutical for imaging prostate cancer (PCa). The aim of this study was to compare the diagnostic accuracy of 18F-PSMA-1007 with 68Ga-PSMA-11 PET/CT in the same patients presenting with newly diagnosed intermediate- or high-risk PCa. Methods: Sixteen patients with intermediate- or high-risk PCa underwent 18F-PSMA-1007 and 68Ga-PSMA-11 PET/CT within 15 d. PET findings were compared between the 2 radiotracers and with reference-standard pathologic specimens obtained from radical prostatectomy. The Cohen κ-coefficient was used to assess the concordance between 18F-PSMA-1007 and 68Ga-PSMA-11 for detection of intraprostatic lesions. The McNemar test was used to assess agreement between intraprostatic PET/CT findings and histopathologic findings. Sensitivity, specificity, positive predictive value, and negative predictive value were reported for each radiotracer. SUVmax was measured for all lesions, and tumor-to-background activity was calculated. Areas under receiver-operating-characteristic curves were calculated for discriminating diseased from nondiseased prostate segments, and optimal SUV cutoffs were calculated using the Youden index for each radiotracer. Results: PSMA-avid lesions in the prostate were identified in all 16 patients with an almost perfect concordance between the 2 tracers (κ ranged from 0.871 to 1). Aside from the dominant intraprostatic lesion, similarly detected by both radiotracers, a second less intense positive focus was detected in 4 patients only with 18F-PSMA-1007. Three of these secondary foci were confirmed as Gleason grade 3 lesions, whereas the fourth was shown on pathologic examination to represent chronic prostatitis. Conclusion: This pilot study showed that both 18F-PSMA-1007 and 68Ga-PSMA-11 identify all dominant prostatic lesions in patients with intermediate- or high-risk PCa at staging. 18F-PSMA-1007, however, may detect additional low-grade lesions of limited clinical relevance.

Development of a Fluorinated Analogue of Erlotinib for PET Imaging of EGFR Mutation-Positive NSCLC.

PURPOSE: Positron emission tomography (PET) using [11C]erlotinib identifies non-small cell lung carcinoma (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFRm). The short half-life of C-11, however, limits its clinical utility to centers with a nearby cyclotron. We therefore developed a F-18-labeled analogue of erlotinib for imaging EGFRm NSCLC. PROCEDURES: 6-O-Fluoroethylerlotinib (6-O-FEE) was synthesized and its anti-proliferative activity was tested using human NSCLC cell lines. The F-18-labeled compound, 6-O-[18F]FEE, was obtained in a two-step synthesis, and PET acquisitions were carried out following its injection to NSCLC tumor-bearing mice. RESULTS: In vitro, 6-O-FEE had maintained the selectivity and potency of erlotinib to EGFRm NSCLC. In vivo, 6-O-[18F]FEE accumulation in EGFRm tumors at 60 min after injection was 2- and 3.3-fold higher than in erlotinib-resistant or erlotinib-insensitive tumors, respectively. CONCLUSIONS: 6-O-[18F]FEE holds promise for imaging EGFRm NSCLC, warranting further investigation to fully explore its potential for stratifying NSCLC patients.

Supportive data on the regulation of GLUT4 activity by 3-O-methyl-D-glucose.

The data presented in this article are related to the research article entitled "Regulation of GLUT4 activity in myotubes by 3-O-methyl-D-glucose" (Shamni et al., 2017) [1]. These data show that the experimental procedures used to analyze the effects of 3-O-methyl-D-glucose (MeGlc) on the rate of hexose transport into myotubes were valid and controlled. The stimulatory effect of MeGlc was limited to glucose transporter 4 (GLUT4) and was independent of ambient glucose and protein synthesis. Cornish-Bowden kinetic analysis of uptake data revealed that MeGlc attenuated indinavir-induced inhibition of hexose transport in a competitive manner.

Role of lipid peroxidation and PPAR-δ in amplifying glucose-stimulated insulin secretion.

OBJECTIVE: Previous studies show that polyunsaturated fatty acids (PUFAs) increase the insulin secretory capacity of pancreatic ß-cells. We aimed at identifying PUFA-derived mediators and their cellular targets that are involved in the amplification of insulin release from ß-cells preexposed to high glucose levels. RESEARCH DESIGN AND METHODS: The content of fatty acids in phospholipids of INS-1E ß-cells was determined by lipidomics analysis. High-performance liquid chromatography was used to identify peroxidation products in ß-cell cultures. Static and dynamic glucose-stimulated insulin secretion (GSIS) assays were performed on isolated rat islets and/or INS-1E cells. The function of peroxisome proliferator-activated receptor-δ (PPAR-δ) in regulating insulin secretion was investigated using pharmacological agents and gene expression manipulations. RESULTS: High glucose activated cPLA(2) and, subsequently, the hydrolysis of arachidonic and linoleic acid (AA and LA, respectively) from phospholipids in INS-1E cells. Glucose also increased the level of reactive oxygen species, which promoted the peroxidation of these PUFAs to generate 4-hydroxy-2E-nonenal (4-HNE). The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets. These effects were blocked with GSK0660, a selective PPAR-δ antagonist, and the antioxidant N-acetylcysteine or by silencing PPAR-δ expression. High glucose, 4-HNE, and GW501516 also induced luciferase expression in a PPAR-δ-mediated transactivation assay. Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range. CONCLUSIONS: Elevated glucose levels augment the release of AA and LA from phospholipids and their peroxidation to 4-HNE in ß-cells. This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in ß-cells.

Pathological aspects of lipid peroxidation.

Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.

Novel D-xylose derivatives stimulate muscle glucose uptake by activating AMP-activated protein kinase alpha.

Type 2 diabetes mellitus has reached epidemic proportions; therefore, the search for novel antihyperglycemic drugs is intense. We have discovered that D-xylose increases the rate of glucose transport in a non-insulin-dependent manner in rat and human myotubes in vitro. Due to the unfavorable pharmacokinetic properties of D-xylose we aimed at synthesizing active derivatives with improved parameters. Quantitative structure-activity relationship analysis identified critical hydroxyl groups in D-xylose. These data were used to synthesize various hydrophobic derivatives of D-xylose of which compound 19 the was most potent compound in stimulating the rate of hexose transport by increasing the abundance of glucose transporter-4 in the plasma membrane of myotubes. This effect resulted from the activation of AMP-activated protein kinase without recruiting the insulin transduction mechanism. These results show that lipophilic D-xylose derivatives may serve as prototype molecules for the development of novel antihyperglycemic drugs for the treatment of diabetes.