2-deoxy-fluorglucose–positron emission tomography imaging of the brain: Current clinical applications with emphasis on the dementias

NAT10/ac4C/JunB facilitates TNBC malignant progression and immunosuppression by driving glycolysis addiction

BACKGROUND

N4-Acetylcytidine (ac4C), a highly conserved post-transcriptional mechanism, plays a pivotal role in RNA modification and tumor progression. However, the molecular mechanism by which ac4C modification mediates tumor immunosuppression remains elusive in triple-negative breast cancer (TNBC).

METHODS

NAT10 expression was analyzed in TNBC samples in the level of mRNA and protein, and compared with the corresponding normal tissues. ac4C modification levels also measured in the TNBC samples. The effects of NAT10 on immune microenvironment and tumor metabolism were investigated. NAT10-mediated ac4C and its downstream regulatory mechanisms were determined in vitro and in vivo. The combination therapy of targeting NAT10 in TNBC was further explored.

RESULTS

The results revealed that the loss of NAT10 inhibited TNBC development and promoted T cell activation. Mechanistically, NAT10 upregulated JunB expression by increasing ac4C modification levels on its mRNA. Moreover, JunB further up-regulated LDHA expression and facilitated glycolysis. By deeply digging, remodelin, a NAT10 inhibitor, elevated the surface expression of CTLA-4 on T cells. The combination of remodelin and CTLA-4 mAb can further activate T cells and inhibite tumor progression.

CONCLUSION

Taken together, our study demonstrated that the NAT10-ac4C-JunB-LDHA pathway increases glycolysis levels and creates an immunosuppressive tumor microenvironment (TME). Consequently, targeting this pathway may assist in the identification of novel therapeutic strategies to improve the efficacy of cancer immunotherapy.

18F-FDG PET and a classifier algorithm reveal a characteristic glucose metabolic pattern in adult patients with moyamoya disease and vascular cognitive impairment

Vascular cognitive impairment (VCI) is a critical issue in moyamoya disease (MMD). However, the glucose metabolic pattern in these patients is still unknown. This study aimed to identify the metabolic signature of cognitive impairment in patients with MMD using ¹⁸F-2-fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG PET) and establish a classifier to identify VCI in patients with MMD. One hundred fifty-two patients with MMD who underwent brain ¹⁸F-FDG PET scans before surgery were enrolled and classified into nonvascular cognitive impairment (non-VCI, n = 52) and vascular cognitive impairment (VCI, n = 100) groups according to neuropsychological test results. Additionally, thirty-three health controls (HCs) were also enrolled. Compared to HCs, patients in the VCI group exhibited extensive hypometabolism in the bilateral frontal and cingulate regions and hypermetabolism in the bilateral cerebellum, while patients in the non-VCI group showed hypermetabolism only in the cerebellum and slight hypometabolism in the frontal and temporal regions. In addition, we found that the patients in the VCI group showed hypometabolism mainly in the left basal ganglia compared to those in the non-VCI group. The sparse representation-based classifier algorithm taking the SUVr of 116 Anatomical Automatic Labeling (AAL) areas as features distinguished patients in the VCI and non-VCI groups with an accuracy of 82.4%. This study demonstrated a characteristic metabolic pattern that can distinguish patients with MMD without VCI from those with VCI, namely, hypometabolic lesions in the left hemisphere played a more important role in cognitive decline in patients with MMD.

Mismatch in Brain Perfusion and Metabolism Detected with 99mTc-Hexamethyl Propylene Amine Oxime Single Photon Emission Computed Tomography and 18F-Fluorodeoxyglucose Positron Emission Tomography in Moyamoya Disease

We report a 47-year-old woman who developed an ischemic stroke with diplopia and dysarthria. Emergency computed tomography (CT) showed no pathological findings, and magnetic resonance (MR) showed mild ischemic-degenerative lesions. MR angiography and angiogram showed severe stenosis of both internal carotid and main intracranial arteries with plenty collateral vessels with “puff of smoke” suggesting a moyamoya disease (MMD). Brain perfusion single-photon emission CT showed global diminished perfusion in the brain lobes and a marked relative hyperperfusion in the cerebellum. However, brain ¹⁸F-fluorodeoxyglucose-positron emission tomography showed physiological metabolism in the brain cortex with only slightly relative cerebellar hypermetabolism. MMD is a well-known arterial pathology that frequently develops with only mild symptoms until the middle age. Functional neuroimaging findings indicate a mismatch between brain glucose metabolism and brain perfusion, probably due to neuronal subclinical chronic ischemia in the brain cortex with preserved viability of neurons.

Blast-induced mild traumatic brain injury

Traumatic brain injury (TBI) has been a major cause of mortality and morbidity in the wars in Iraq and Afghanistan. Blast exposure has been the most common cause of TBI, occurring through multiple mechanisms. What is less clear is whether the primary blast wave causes brain damage through mechanisms that are distinct from those common in civilian TBI and whether multiple exposures to low-level blast can lead to long-term sequelae. Complicating TBI in soldiers is the high prevalence of posttraumatic stress disorder. At present, the relationship is unclear. Resolution of these issues will affect both treatment strategies and strategies for the protection of troops in the field.

Clinical applications of positron emission tomography-computed tomography in oncology

Positron emission computed tomography (PET) is a functional diagnostic imaging technique, which can accurately measure in vivo distribution of a variety of radiopharmaceuticals. The ability of PET to study various biological processes (glucose, amino acid, phospholipids, receptors etc.) opens up new possibilities for both day-to-day clinical use and research applications in the practice of oncology. Addition of CT to PET has resulted in better specificity and sensitivity than either of the modalities alone, as the combined approach has the ability to demonstrate functional and structural details in the same setting. F-18 fluoro-2-deoxy-D-glucose (FDG), an analogue of glucose, is the most commonly used radiotracer in PET-CT imaging. The F-18 FDG uptake in tumor cells is directly proportional to glucose metabolism in the cells. Since glucose metabolism is increased several folds in the malignant tumors, PET-CT images show preferential higher FDG uptake in malignant cells as compared to normal cells. F-18 FDG PET-CT has been found to be useful in the initial staging, detection of recurrent disease and monitoring the response to the therapy in malignancies including lung cancer, colorectal cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer, breast cancer.

Statistical parametric mapping and cluster counting analysis of [18F] FDG-PET imaging in traumatic brain injury

In this study we investigated regional cerebral glucose metabolism abnormalities of [(18)F] fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging in traumatic brain injury (TBI). PET images of 81 TBI patients and 68 normal controls were acquired and a word list learning task was administered during the uptake period. The TBI group included 35 patients with positive structural imaging (CT or MRI) findings soon after injury, 40 patients with negative findings, and 6 cases without structural imaging. Statistical parametric mapping (SPM) analysis was applied with several levels of spatial smoothing. Cluster counting analysis was performed for each subject to identify abnormal clusters with contiguous voxel values that deviated by two standard deviations or more from the mean of the normal controls, and to count the number of clusters in 10 size categories. SPM maps demonstrated that the 81 patients had significantly lower FDG uptake than normal controls, widely across the cortex (including bilateral frontal and temporal regions), and in the thalamus. Cluster counting results indicated that TBI patients had a higher proportion of larger clusters than controls. These large low-FDG-uptake clusters of the TBI patients were closer to the brain edge than those of controls. These results suggest that deficits of cerebral metabolism in TBI are spread over multiple brain areas, that they are closer to the cortical surface than clusters in controls, and that group spatial patterns of abnormal cerebral metabolism may be similar in TBI patients with cognitive deficits with and without obvious acute abnormalities identified on structural imaging.

PET imaging in pediatric neuroradiology: current and future applications

Molecular imaging with positron emitting tomography (PET) is widely accepted as an essential part of the diagnosis and evaluation of neoplastic and non-neoplastic disease processes. PET has expanded its role from the research domain into clinical application for oncology, cardiology and neuropsychiatry. More recently, PET is being used as a clinical molecular imaging tool in pediatric neuroimaging. PET is considered an accurate and noninvasive method to study brain activity and to understand pediatric neurological disease processes. In this review, specific examples of the clinical use of PET are given with respect to pediatric neuroimaging. The current use of co-registration of PET with MR imaging is exemplified in regard to pediatric epilepsy. The current use of PET/CT in the evaluation of head and neck lymphoma and pediatric brain tumors is also reviewed. Emerging technologies including PET/MRI and neuroreceptor imaging are discussed.

Resting brain glucose uptake in headache-free migraineurs

BACKGROUND AND OBJECTIVE

To compare metabolism in the brains of migraineurs during headache-free periods with those obtained from healthy volunteers.

METHODS

Eleven migraineurs (defined by the International Headache Society's criteria) presented during spontaneous headache-free intervals to undergo (18)FDG PET brain imaging of glucose metabolism. The control group consisted of 14 healthy volunteers. Comparison of images was done using Statistical Parametric Mapping to detect significant (P < .05) differences in brain glucose metabolism between the 2 groups.

RESULTS

Two regions of significant increase in glucose uptake were identified in migraineurs relative to the control population. The 2 regions were mapped predominantly to the posterior white matter of the cerebrum and cerebellum.

CONCLUSIONS

Our study demonstrates the presence of what may be a primary metabolic disturbance in the posterior white matter of the brain in migraineurs.

Multicentre assessment and monitored use of [18F]FDG-PET in oncology: the Spanish experience

PURPOSE

The aim of this study was to evaluate the diagnostic effectiveness of [(18)F]FDG-PET in oncological diseases and to assess its clinical utility and impact (on the clinical and therapeutic management of these patients). This health technology assessment was performed in Spain, using the monitored use (MU) procedure.

METHODS

A multicentre and prospective follow-up study was performed in a non-consecutive sample of oncological patients who were examined with PET and other conventional diagnostic tests. A protocol for this MU method (PET-MU protocol) was developed, including the three forms used to collect all the information. Enrollment of new patients began in June 2002 and continued until August 2004. A descriptive analysis and an evaluation of the diagnostic effectiveness of FDG-PET were performed.

RESULTS

The study population comprised 2,824 oncological patients (the third form relating to follow-up was completed for only 967 of these patients) from 100 Spanish hospitals and 16 PET centres. Seventy-nine percent of cases met the clinical requirements of the PET-MU protocol. Global diagnostic parameters of PET performance and their 95% CI values were as follows: sensitivity 86% (82-89%), specificity 83% (79-86%), positive and negative predictive values 87% (83-90%) and 82% (77-85%) respectively, diagnostic accuracy 84% (82-87%) and diagnostic odds ratio 28.75 (19.75-41.84). PET detected unsuspected new lesions in 39% of patients and avoided other unnecessary diagnostic techniques and treatments in 69% of cases. In 88% of cases, PET was considered useful by the physicians who asked for the PET tests (it was deemed decisive in 30% and very useful in almost 37%).

CONCLUSION

This PET-MU study has confirmed the high diagnostic effectiveness of FDG-PET for oncological indications and demonstrates that it has a great influence on the clinical and therapeutic management of patients.

Positron emission tomography: clinical applications in oncology. Part 2

This review continues from a previous review on this topic, which was published in the December issue. In that review, the role of positron emission tomography in lung cancer, lymphoma, breast cancer, head and neck cancer, gastroesophageal cancer, colorectal cancer, malignant melanoma, bone tumors and ovarian cancer was discussed. In this review, the role of positron emission tomography in other malignancies, such as gynecological malignancies other than ovary, pancreatic cancer, hepatocellular cancer, gastrointestinal tumors, urological malignancies, neuroendocrine tumors, adrenocortical tumors, soft-tissue sarcomas, pituitary and brain tumors, is discussed.