Kinetics of angiogenic changes in a new mouse model for hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>The increasing incidence of hepatocellular carcinoma in Western countries has led to an expanding interest of scientific research in this field. Therefore, a vast need of experimental models that mimic the natural pathogenesis of hepatocellular carcinoma (HCC) in a short time period is present. The goal of our study was (1) to develop an efficient mouse model for HCC research, in which tumours develop in a natural background of fibrosis and (2) to assess the time-dependent angiogenic changes in the pathogenesis of HCC.</p> <p>Methods</p> <p>Weekly intraperitoneal injections with the hepatocarcinogenic compound N-nitrosodiethylamine was applied as induction method and samples were taken at several time points to assess the angiogenic changes during the progression of HCC.</p> <p>Results</p> <p>The N-nitrosodiethylamine-induced mouse model provides well vascularised orthotopic tumours after 25 weeks. It is a representative model for human HCC and can serve as an excellent platform for the development of new therapeutic targets.</p

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

[18F]Fluoromethylcholine and analogues: synthesis, in vitro and in vivo evaluation, and kinetic modelling

To date, the tracer most used for molecular imaging in oncology is [18F]FDG. Despite its clinical use for the visualisation of various types of cancers, [18F]FDG displays several shortcomings including uptake in brown fat or inflamed tissues, high urinary clearance or brain uptake, and low uptake in poorly differentiated tumours. This rationalizes the drive to develop new tracers that are based on other metabolic pathways like protein synthesis, tumour cell proliferation, or fatty acid synthesis. In this respect, [18F]FCho is a promising alternative because its uptake in tumour cell is correlated to up regulated and elevated levels of choline kinase and choline transporters. Due to the affinity for the kinase enzyme, choline is metabolically trapped in tumour cells with superior imaging properties as result. To further elaborate the potential of [18F]FCho as radiotracer, a semi-automated Scintomics synthesis module was modified for its production. However, using the prescribed synthesis procedures, we observed high levels of residual DMAE in the [18F]FCho solution thus obtained. Remarkably, few attention has been paid to this defect, especially since in previously published reports it was noted that [11C]Cho uptake was altered by the presence of residual DMAE. As a consequence, we attempted to produce [18F]FCho with higher purity (i.e., lower DMAE levels) and, in line with this, to elucidate the role of residual DMAE on [18F]FCho uptake using F98 glioma cell lines and xenograft mouse models (Chapter 3). Having a [18F]FCho preparation method available, an investigational medicinal product dossier was compiled for 2 clinical trials to be conducted using this tracer: 1) for the early detection of glioma recurrence after treatment of the primary tumour and 2) for differentiation between cirrhotic changes and malignant lesions in well-differentiated hepatocellular carcinomas (HCC). These trials required the implementation of a fully validated quality system for the production and quality control of the final [18F]FCho solution. To assure long-term stability of this procedure, a retrospective study was conducted to evaluate the quality of the produced tracer and the validated synthesis procedure. Moreover, the compliance of the synthesis procedures and quality controls with the forthcoming PIC/s regulations for hospital pharmacies was evaluated (Chapter 4). Considering the need for quantification of the radiotracer uptake to evaluate biological processes, we assumed it was appropriate to determine a proper kinetic model for [18F]FCho. The selected kinetic model was verified against the corresponding, but simplified graphical analysis to obtain a robust and reliable method that allows absolute quantification of the tracer uptake in tissues (Chapter 5). [18F]FCho is currently used for the visualisation of various tumours, but oxidative metabolisation to the corresponding betaine compromises sensitivity. The development of analogues, which are less susceptible to this oxidation, seems a feasible strategy to induce tracer uptake in the tumours with improved sensitivity. For this reason, dimethylaminoethanol (DMAE) and homocholine were labelled with [18F]fluoride and evaluated in vivo as potential biomarkers for the aberrant phospholipids metabolism. Indeed, preliminary in vitro tests indicated that [14C]- and [11C]-labelled DMAE are better tracers to visualize the tumours phospholipids metabolism, because their uptake in various tumour cells was 2 to 7-fold higher than for [14C]- and [11C]-labelled choline. Considering the better radiophysical properties of [18F]fluorinated compounds, synthesis was attempted of [18F]-labelled DMAE as a new tracer for tumour imaging (Chapter 6). On the other hand, it was published that homocholine shows reduced affinity for the choline dehydrogenase enzyme. Accordingly, evaluation of radiolabelled homocholine and its analogues as potential biomarkers for the aberrant phospholipids metabolism was aimed at (Chapter 7)

PET with 18F-labelled choline-based tracers for tumour imaging: a review of the literature

To give an up-to-date overview of the potential clinical utility of F-18-labelled choline derivatives for tumour imaging with positron emission tomography. A PubMed search for F-18-labelled choline analogues was performed. Review articles and reference lists were used to supplement the search findings. F-18-labelled choline analogues have been investigated as oncological PET probes for many types of cancer on the basis of enhanced cell proliferation. To date, studies have focused on the evaluation of prostate cancer. Available studies have provided preliminary results for detecting local and metastatic disease. Experience with F-18-fluorocholine PET in other tumour types, including brain and liver tumours, is still limited. In the brain, excellent discrimination between tumour and normal tissue can be achieved due to the low physiological uptake of F-18-fluorocholine. In the liver, in which there is a moderate to high degree of physiological uptake in normal tissue, malignancy discrimination may be more challenging. PET/CT with F-18-fluorocholine can be used to detect (recurrent) local prostate cancer, but seems to have limited value for T (tumour) and N (nodal) staging. In patients presenting with recurrent biochemical prostate cancer, it is a suitable single-step examination with the ability to exclude distant metastases when local salvage treatment is intended. In the brain, high-grade gliomas, metastases and benign lesions can be distinguished on the basis of F-18-fluorocholine uptake. Moreover, PET imaging is able to differentiate between radiation-induced injury and tumour recurrence. In the liver, F-18-fluorocholine PET/CT seems promising for the detection of hepatocellular carcinoma

Reduced dimethylaminoethanol in [18F]fluoromethylcholine: an important step towards enhanced tumour visualization

[F-18]Fluoromethylcholine ([F-18]FCho) is a radiotracer generally used for tumour visualization in patients. Due to high levels of dimethylaminoethanol (DMAE) remaining in [F-18]FCho solutions synthesized by currently available methods, tumour visualization might be compromised. An improved purification method involving an optimized purification step for reducing the levels of DMAE was conceived. The physiological explanation for the interference of residual DMAE in [F-18]FCho pharmacokinetics was further elaborated in a xenograft mouse model. The use of a series of polymer solid-phase extraction cartridges (Oasis HLB/WCX), instead of the commonly used combination of tC18 and Accell CM cartridges, reduced DMAE levels from 402.2 +/- 49.6 ppm to 3.0 +/- 0.5 ppm. Subsequent in vitro tests proved that (1) [F-18]FCho uptake was reduced in the presence of DMAE at concentrations above 0.5 A mu M and (2) DMAE is a competitive inhibitor of [F-18]FCho transport. In vivo experiments in xenograft mouse models corroborated reduced tumour uptake at DMAE plasma levels of about 2.5 A mu M as found in patients injected with contaminated [F-18]FCho. Residual DMAE, even at levels below choline plasma concentrations found during fasting, compromises [F-18]FCho uptake in vivo and care should be taken to avoid its interference in molecular imaging with [F-18]FCho

FDG and choline PET for early assessment of treatment response in hepatocellular carcinoma

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Distribution patterns of 18F-labelled fluoromethylcholine in normal structures and tumors of the head A PET/MRI evaluation

Purpose: To evaluate the distribution of F-18-labelled fluoromethylcholine (FCho) in normal structures and tumors of the head region using positron emission tomography (PET) and magnetic resonance imaging. Materials and Methods: We retrospectively reviewed the positron emission tomography, magnetic resonance imaging, and the coregistered images obtained in 17 patients with suspected high-grade gliomas. The accumulation of F-18-FCho in the normal structures and in brain lesions was visually and semiquantitatively assessed. A 4-point grading system was used for the visual analysis. A standardized uptake value (SUV) was used to quantify uptake. Results: In the normal brain parenchyma, F-18-FCho uptake was faint (SUVmean, 0.15 +/- 0.03 (SD)). Uptake was generally moderate in the choroid plexus (SUVmean, 0.82 +/- 0.16), cavernous sinus (SUVmean, 0.87 +/- 0.19), extraocular eye muscles (SUVmean, 1.10 +/- 0.27), masticatory muscles (SUVmean, 0.99 +/- 0.22), and bone marrow (SUVmean, 1.06 +/- 0.26), whereas uptake was usually moderately intense in the pituitary gland (SUVmean, 1.90 +/- 0.21). Uptake was variable in the lacrimal glands and the mucosa of the nasal cavity (for SUVmean of subgroups see text). Intense uptake was observed in the parotid glands (SUVmean, 3.27 +/- 0.73). (Moderately) intense F-18-FCho uptake was observed in glioblastomas (range SUVmax, 2.26-6.37) and typical meningiomas (range SUVmax, 3.75-5.81). Uptake was globally faint in grade II and III gliomas (range SUVmax, 0.33-0.78). F-18-FCho uptake was also demonstrated in benign lesions, such as a tumefactive demyelinating brain lesion. Conclusions: F-18-FCho uptake was faint in the normal brain parenchyma and usually moderate in the choroid plexus, cavernous sinus, extraocular eye muscles, masticatory muscles, and bone marrow. Uptake in the pituitary gland was generally moderately intense, whereas uptake in the lacrimal glands and the mucosa of the nasal cavity was variable. Parotid glands had intense uptake. Also, uptake in glioblastomas and meningiomas was usually (moderately) intense, whereas uptake in grade II and III gliomas was globally faint. However, F-18-FCho uptake was not tumor specific