REDIportal: millions of novel A-to-I RNA editing events from thousands of RNAseq experiments.

RNA editing is a relevant epitranscriptome phenomenon able to increase the transcriptome and proteome diversity of eukaryotic organisms. ADAR mediated RNA editing is widespread in humans in which millions of A-to-I changes modify thousands of primary transcripts. RNA editing has pivotal roles in the regulation of gene expression or modulation of the innate immune response or functioning of several neurotransmitter receptors. Massive transcriptome sequencing has fostered the research in this field. Nonetheless, different aspects of the RNA editing biology are still unknown and need to be elucidated. To support the study of A-to-I RNA editing we have updated our REDIportal catalogue raising its content to about 16 millions of events detected in 9642 human RNAseq samples from the GTEx project by using a dedicated pipeline based on the HPC version of the REDItools software. REDIportal now allows searches at sample level, provides overviews of RNA editing profiles per each RNAseq experiment, implements a Gene View module to look at individual events in their genic context and hosts the CLAIRE database. Starting from this novel version, REDIportal will start collecting non-human RNA editing changes for comparative genomics investigations. The database is freely available at http://srv00.recas.ba.infn.it/atlas/index.html.

Changes over the years in radiopharmaceutical design.

Of the many uses of radiopharmaceuticals, developing radiotracers that contribute significantly to diagnosis and therapy of patients has been a major focus. This requires a broad spectrum of expertise including that of the attending physician who lends insight to an unmet clinical need neither addressed by other imaging techniques nor by analysis of tissue, blood, and urine for diagnostics and addressed by pharmaceuticals for therapeutic applications. The design criteria have depended on radiochemistry, on matching the radiopharmaceutical with the imaging devices, and basing the design on current pharmaceuticals. The chelates of technetium-99m were based on radiochemistry rather than clinical need yet are still used today in >70% of the clinical studies. Targeted radiotracers in neurologic and psychiatric disorders, inflammation, cardiovascular disease, and oncology have all been studied with the goal of determining the change in the density of a target protein as a function of disease or treatment or, especially in oncology, detection of the total extent of disease. In the latter approach, PET in university settings leads the way; however, the use of SPECT/CT has increased the specificity of SPECT imaging to complement the cost-effective generator and instant kits already available. Remarkable advances have been achieved in radionuclide therapy using theragnostic agents, with the exclusive domain of oncology. For this application the design of radionuclide therapy follows that used for diagnostics. The increased impact of the discipline depends on the opportunity to continue the search for the most appropriate radiopharmaceutical for each individual patient.

Theragnostics before we found its name.

Theragnostics embraces "gnosis" and "prognosis" and concerns a treatment strategy which combines diagnostics with therapeutics. The birth of what we call today theragnostics can be traced in 1936, with the proposal of radioiodine, the first radiopharmaceutical approved in 1951 by FDA, in USA, as 131I sodium iodide. In 1957, 89Sr was also approved as first therapeutic radiotracer for skeletal metastases, followed in the subsequent years by 186Rh, 153Sm and, more recently, 223Ra, the first alpha emitter clinically utilized, allowing curative results and not only a palliative effect. Proposed in first eighties as [131I] Metaiodobenzylguanidine (MIBG), the theragnostic couple 123I/131I MIBG is still used in neural crest tumors, while, starting from partially unsatisfactory results in 70's, models based on antibodies for radioimmunoscintigraphy/radioimmunotherapy have been subsequently upgraded thanks to the introduction of monoclonal antibodies and other significant biological and technical improvements. The "Theragnostics called with this name" can be dated to early 90's with the first proposal of the somatostatin model, actually widely operating in neuroendocrine tumors with radio-chelates usable for diagnosis and therapy. Since then, many investigators are working on new theragnostics agents, also outside of the nuclear medicine, based on peptides, antibodies and other tools to find new models applicable in the clinical practice. The fast growth is stimulated by the interest of big pharma. Theragnostic concepts are the roots of nuclear medicine and new great goals are soon to be achieved in the direction of an increasing precision and tailored medicine.

The brain cognitive reserve hypothesis: A review with emphasis on the contribution of nuclear medicine neuroimaging techniques.

Neuropathological and clinical evidence indicates that the clinical expression of Alzheimer's disease (AD) occurs as neuropathology exceeds the brain reserve capacity. The brain or cognitive reserve (BCR) hypothesis states that high premorbid intelligence, education, and an active and stimulating lifestyle provide reserve capacity, which acts as a buffer against the cognitive deficits due to accumulating neuropathology. Neuroimaging studies that assessed the BCR hypothesis are critically reviewed with emphasis on study design and statistical analysis. Many studies were performed in the last two decades owing to the increasing availability of positron emission tomography (PET) and PET/computed tomography scanners and to the synthesis of new radiopharmaceuticals, including tracers for amyloid and tau proteins. Studies with different tracers provided complementary consistent results supporting the BCR hypothesis. Many studies were appropriately designed with a measure of reserve, a measure of brain anatomy/function/neuropathology, and a measure of cognitive functions that are necessary. Most of the early studies were performed with PET and [ 18 F]fluorodeoxyglucose, and occasionally with [ 15 O]water, reporting a significant association between higher occupation/education and lower glucose metabolism (blood flow) in associative temporo-parietal cortex in patients with AD and also in patients with MCI, after correcting for the degree in the cognitive impairment. On the contrary, performances on several neuropsychological tests increased with increasing education for participants with elevated [ 11 C]PiB uptake. Studies with the tracers specific for tau protein showed that patients with AD with elevated tau deposits had higher cognitive performances compared with patients with similar levels of tau deposits. BCR in AD is also associated with a preserved cholinergic function. The BCR hypothesis has been validated with methodologically sound study designs and sophisticated neuroimaging techniques using different radiotracers and providing an explanation for neuropathological and clinical observations on patients with AD.

Amyloid burden identifies neuropsychological phenotypes at increased risk of progression to Alzheimer's disease in mild cognitive impairment patients.

PURPOSE: The extent of amyloid burden associated with cognitive impairment in amnestic mild cognitive impairment is unknown. The primary aim of the study was to determine the extent to which amyloid burden is associated to the cognitive impairment. The secondary objective was to test the relationship between amyloid accumulation and memory or cognitive impairment. MATERIALS AND METHODS: In this prospective study 66 participants with amnestic mild cognitive impairment underwent clinical, neuropsychological and PET amyloid imaging tests. Composite scores assessing memory and non-memory domains were used to identify two clinical classes of neuropsychological phenotypes expressing different degree of cognitive impairment. Detection of amyloid status and definition of optimal amyloid ± cutoff for discrimination relied on unsupervised k-means clustering method. RESULTS: Threshold for identifying low and high amyloid retention groups was of SUVr = 1.3. Aß + participants showed poorer global cognitive and episodic memory performance than subjects with low amyloid deposition. Aß positivity significantly identified individuals with episodic memory impairment with a sensitivity and specificity of 80 and 79%, (χ2 = 21.48; P < 0.00001). Positive and negative predictive values were 82 and 76%, respectively. Amyloid deposition increased linearly as function of memory impairment with a rate of 0.13/ point of composite memory score (R = -44, P = 0.0003). CONCLUSION: The amyloid burden of SUVr = 1.3 allows early identification of subjects with episodic memory impairment which might predict progression from MCI to Alzheimer's disease. TRIAL REGISTRATION: EudraCT 2015-001184-39.

The future of choline PET in the era of prostate specific membrane antigen.

Radiolabeled choline was the first radiopharmaceutical agent employed in prostate cancer patients. It has been considered a metabolic agent able to detect the presence of prostate cancer cell, both in the initial phase of the disease and in the restaging setting. Three agents are now available in clinical practice: one radiolabeled with 11C (called 11C-Choline) and two with 18F (either as 18F-methylcholine or 18F-ethylcholine). During the years, different studies have been performed with 11C -Choline and 18F-Choline demonstrating their performance for the detection of prostate cancer, in different settings of the disease. However, recently, new radiopharmaceutical agents for prostate cancer have been developed, gaining an important role for the diagnosis of prostate cancer, particularly in the restaging setting. The present review has been conceived in order to discuss the current role of radiolabeled choline PET/CT in the era of new agents for prostate cancer, in particular in the era of radiolabeled PSMA.

Performance of FDG-PET/CT in solitary pulmonary nodule based on pre-test likelihood of malignancy: results from the ITALIAN retrospective multicenter trial.

PURPOSE: The aim of this study was to determine the performance of 18F-FDG-PET/CT in patients with solitary pulmonary nodule (SPN), stratifying the risk according to the likelihood of pulmonary malignancy. METHODS: FDG-PET/CT of 502 patients, stratified for pre-test cancer risk, were retrospectively analyzed. FDG uptake in SPN was assessed by a 4-point scoring system and semiquantitative analysis using the ratio between SUVmax in SPN and SUVmean in mediastinal blood pool (BP) and between SUVmax in SPN and SUVmean in liver (L). Histopathology and/or follow-up data were used as standard of reference. RESULTS: SPN was malignant in 180 (36%) patients, benign in 175 (35%), and indeterminate in 147 (29%). The 355 patients with a definitive SPN nature (malignant or benign) were considered for the analysis. Considering FDG uptake ≥ 2, sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and accuracy were 85.6%, 85.7%, 86%, 85.2%, and 85.6% respectively. Sensitivity and PPV were higher (P < 0.05) in intermediate and high-risk patients, while specificity and NPV were higher (P < 0.05) in low-risk patients. On receiver operating characteristic curve analysis, the cut-offs for better discrimination between benign and malignant SPN were 1.56 (sensitivity 81% and specificity 87%) and 1.12 (sensitivity 81% and specificity 86%) for SUVmax/SUVmeanBP and SUVmax/SUVmeanL respectively. In intermediate and high-risk patients, including the SUVmax/SUVmeanBP, the specificity shifted from 85% and 50% to 100%. CONCLUSION: Visual FDG-PET/CT has an acceptable performance in patients with SPN, but accuracy improves when SUVratios are considered, particularly in patients with intermediate and high risk of malignancy.

Risk-related 18F-FDG PET/CT and new diagnostic strategies in patients with solitary pulmonary nodule: the ITALIAN multicenter trial.

PURPOSE: Diagnosis of solitary pulmonary nodule (SPN) is an important public health issue and 18F-FDG PET/CT has proven to be more effective than CT alone. Pre-test risk stratification and clinical presentation of SPN could affect the diagnostic strategy. A relevant issue is whether thoracic segmental (s)-PET/CT could be implemented in patients with SPN. This retrospective multicenter study compared the results of FDG whole-body (wb)-PET/CT to those of s-PET/CT. METHODS: 18F-FDG PET/CT of 502 patients, stratified for pre-test cancer risk, were retrospectively analyzed. The thoracic part of wb-PET/CT, considered s-PET/CT, was compared to wb-PET/CT. Clinical and PET/CT variables were investigated for SPN characterization as well as for identification of patients in whom s-PET/CT could be performed. Histopathology or follow-up data were used as a reference. RESULTS: In the study population, 36% had malignant, 35% benign, and 29% indeterminate SPN. 18F-FDG uptake indicative of thoracic and extra-thoracic lesions was detectable in 13% and 3% of the patients. All patients with extra-thoracic metastases (n = 13) had thoracic lymph node involvement and highest 18F-FDG uptake at level of SPN (negative predictive value 100%). Compared to wb-PET/CT, s-PET/CT could save about 2/3 of 18F-FDG dose, radiation exposure or scan-time, without affecting the clinical impact of PET/CT. CONCLUSION: Pre-test probability of malignancy can guide the diagnostic strategy of 18FDG-PET/CT in patients with SPN. In subjects with low-intermediate pretest probability s-PET/CT imaging might be planned in advance, while in those at high risk and with thoracic lymph node involvement a wb-PET/CT is necessary.

Biochemical and Pathophysiological Premises to Positron Emission Tomography With Choline Radiotracers.

Choline is a quaternary ammonium base that represents an essential component of phospholipids and cell membranes. Malignant transformation is associated with an abnormal choline metabolism at a higher levels with respect to those exclusively due to cell multiplication. The use of Positron Emission Tomography/Computed Tomography (PET/CT) with radiocholine (RCH), labeled with 11 C or 18 F, is widely diffuse in oncology, with main reference to restaging of patients with prostate cancer. The enhanced concentration in neoplasm is based not only on the increasing growing rate, but also on more specific issues, such as the augmented uptake in malignant cells due to the up-regulation of choline kinase. Furthermore the role of hypoxia in decreasing choline's uptake determine an in vivo concentration only in well oxygenated tumors, with a lower uptake when malignancy increases, that is, in tumors positive at 18 F-Fluoro-deoxyglucose. In this paper we have analyzed the most important issues related to the possible utilization of RCH in diagnostic imaging of human cancer. J. Cell. Physiol. 232: 270-275, 2017. © 2016 Wiley Periodicals, Inc.

Molecular Imaging of Huntington's Disease.

The onset and the clinical progression of Huntington Disease (HD) is influenced by several events prompted by a genetic mutation that affects several organs tissues including different regions of the brain. In the last decades years, Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) helped to deepen the knowledge of neurodegenerative mechanisms that guide to clinical symptoms. Brain imaging with PET represents a tool to investigate the physiopathology occurring in the brain and it has been used to predict the age of onset of the disease and to evaluate the therapeutic efficacy of new drugs. This article reviews the contribution of PET and MRI in the research field on Huntington's disease, focusing in particular on some most relevant achievements that have helped recognize the molecular changes, the clinical symptoms and evolution of the disease. J. Cell. Physiol. 232: 1988-1993, 2017. © 2016 Wiley Periodicals, Inc.

Clinical characteristics of patient selection and imaging predictors of outcome in solid tumors treated with checkpoint-inhibitors.

The rapidly evolving knowledge on tumor immunology and the continuous implementation of immunotherapy in cancer have recently led to the FDA and EMA approval of several checkpoint inhibitors as immunotherapic agents in clinical practice. Anti-CTLA-4, anti-PD-1, and anti-PDL-1 antibodies are becoming standard of care in advanced melanoma, as well as in relapsed or metastatic lung and kidney cancer, demonstrating higher and longer response compared to standard chemotherapy. These encouraging results have fostered the evaluation of these antibodies either alone or in combination with other therapies in several dozen clinical trials for the treatment of multiple tumor types. However, not all patients respond to immune checkpoint inhibitors, hence, specific biomarkers are necessary to guide and monitor therapy. The utility of PD-L1 expression as a biomarker has varied in different clinical trials, but, to date, no consensus has been reached on whether PD-L1 expression is an ideal marker for response and patient selection; approximately 20-25% of patients will respond to immunotherapy with checkpoint inhibitors despite a negative PD-L1 staining. On the other hand, major issues concern the evaluation of objective response in patients treated with immunotherapy. Pure morphological criteria as commonly used in solid tumors (i.e. RECIST) are not sufficient because change in size is not an early and reliable marker of tumor response to biological therapies. Thus, the scientific community has required a continuous adaptation of immune-related response criteria (irRC) to overcome the problem. In this context, metabolic information and antibody-based imaging with positron emission tomography (PET) have been investigated, providing a powerful approach for an optimal stratification of patients at staging and during the evaluation of the response to therapy. In the present review we provide an overview on the clinical characteristics of patient selection when using imaging predictors of outcome in solid tumors treated with checkpoint-inhibitors.

The natural history of takotsubo syndrome: a two-year follow-up study with myocardial sympathetic and perfusion G-SPECT imaging.

PURPOSE: To investigate changes in sympathetic activity, perfusion, and left ventricular (LV) functionality in takotsubo cardiomyopathy (TTC) patients from onset (T0) to post-onset conditions at 1 month (T1), 1-2 years (T2, T3). METHODS: Twenty-two patients (70 ± 11 years) underwent serial gated single photon emission tomography (G-SPECT) studies with 123I-mIBG and 99mTc-Sestamibi. Statistics were performed using ANOVA/Sheffé post-hoc, correlation test, and receiver operating characteristic (ROC) curve analysis (p < 0.05). RESULTS: Patients presented at T0 with LV ballooning and reduced early-late mIBG uptake (95%, 100%), left ventricular ejection fraction (LVEF)G-SPECT (86%) and perfusion (77 %). Adrenergic dysfunction was greater in apex, it overlaps with contractile impairment, and both were more severe than perfusion defect. During follow-up, LVEFG-SPECT, contractility, and perfusion were normal, while 82% and 90% of patients at T1 and 50% at T2 and T3 continued to show a reduced apical early-late mIBG distribution. These patients presented at T0-T1 with greater impairment of adrenergic function, contractility, and perfusion. A relationship was present within innervation and both perfusion and contractile parameters at T0 and T1, and between the extent of adrenergic defect at T3 and both the defect extent and age at T0 (cut-off point 42.5%, 72 years). CONCLUSION: Outcome for TTC is not limited to a reversible contractile and perfusion abnormalities, but it includes residual adrenergic dysfunction, depending on the level of adrenergic impairment and age of patients at onset. The number of patients, as well as degree of perfusion abnormalities were found to be higher than those previously reported possibly depending on the time-interval between hospital admission and perfusion scan.

Weighted registration of 123I-FP-CIT SPECT images improves accuracy of binding potential estimates in pathologically low striatal uptake.

To test whether the use of a striatum weighted image may improve registration accuracy and diagnostic outcome in patients with parkinsonian syndromes (PS), weighted images were generated by increasing signal intensity of striatal voxels and used as intermediate dataset for co-registering the brain image onto template. Experimental validation was performed using an anthropomorphic striatal phantom. (123)I-FP-CIT SPECT binding ratios were manually determined in 67 PS subjects and compared to those obtained using unsupervised standard (UWR) and weighted registered (WR) approach. Normalized cost function was used to evaluate the accuracy of phantom and subjects registered images to the template. Reproducibility between unsupervised and manual ratios was assessed by using intra-class correlation coefficient (ICC) and Bland and Altman analysis. Correlation coefficient was used to assess the dependence of semi-quantitative ratios on clinical findings. Weighted method improves accuracy of brain registration onto template as determined by cost function in phantom (0.86 ± 0.06 vs. 0.98 ± 0.02; Student's t-test, P = 0.04) and in subject scans (0.69 ± 0.06 vs. 0.53 ± 0.06; Student's t-test, P < 0.0001). Agreement between manual and unsupervised derived binding ratios as measured by ICC was significantly higher on WR as compared to UWR images (0.91 vs. 0.76). Motor UPDRS score was significantly correlated with manual and unsupervised derived binding potential. In phantom, as well as in subjects studies, correlations were more significant using the WR method (BPm: R(2) = 0.36, P = 0.0001; BPwr: R(2) = 0.368, P = 0.0001; BPuwr: R(2) = 0.300, P = 0.0008). Weighted registration improves accuracy of binding potential estimates and may be a promising approach to enhance the diagnostic outcome of SPECT imaging, correlation with disease severity, and for monitoring disease progression in Parkinsonian syndromes.

Algorithm for Reducing Overall Biological Detriment Caused by PET/CT: an Age-Based Study.

Purpose: This study is to use a simple algorithm based on patient's age to reduce the overall biological detriment associated with PET/CT. Materials and Methods: A total of 421 consecutive patients (mean age 64 ± 14 years) undergoing PET for various clinical indications were enrolled. For each scan, effective dose (ED in mSv) and additional cancer risk (ACR) were computed both in a reference condition (REF) and after applying an original algorithm (ALGO). The ALGO modified the mean dose of FDG and the PET scan time parameters; indeed, a lower dose and a longer scan time were reported in the younger, while a higher dose and a shorter scan time in the older patients. Moreover, patients were classified by age bracket (18-29, 30-60, and 61-90 years). Results: The ED was 4.57 ± 0.92 mSv in the REF condition. The ACR were 0.020 ± 0.016 and 0.0187 ± 0.013, respectively, in REF and ALGO. The ACR for the REF and ALGO conditions were significantly reduced in males and females, although it was more evident in the latter gender (all p < 0.0001). Finally, the ACR significantly reduced from the REF condition to ALGO in all three age brackets (all p < 0.0001). Conclusion: Implementation of ALGO protocols in PET can reduce the overall ACR, mainly in young and female patients.

Cumulus Cell Transcriptome after Cumulus-Oocyte Complex Exposure to Nanomolar Cadmium in an In Vitro Animal Model of Prepubertal and Adult Age.

Cadmium (Cd), a highly toxic pollutant, impairs oocyte fertilization, through oxidative damage on cumulus cells (CCs). This study analysed the transcriptomic profile of CCs of cumulus-oocyte complexes (COCs) from adult and prepubertal sheep, exposed to Cd nanomolar concentration during in vitro maturation. In both age-groups, CCs of matured oocytes underwent RNA-seq, data analysis and validation. Differentially expressed genes (DEGs) were identified in adult (n = 99 DEGs) and prepubertal (n = 18 DEGs) CCs upon Cd exposure. Transcriptomes of adult CCs clustered separately between Cd-exposed and control samples, whereas prepubertal ones did not as observed by Principal Component Analysis. The transcriptomic signature of Cd-induced CC toxicity was identified by gene annotation and literature search. Genes associated with previous studies on ovarian functions and/or Cd effects were confirmed and new genes were identified, thus implementing the knowledge on their involvement in such processes. Enrichment and validation analysis showed that, in adult CCs, Cd acted as endocrine disruptor on DEGs involved in hormone biosynthesis, cumulus expansion, regulation of cell signalling, growth and differentiation and oocyte maturation, whereas in prepubertal CCs, Cd affected DEGs involved in CC development and viability and CC-oocyte communications. In conclusion, these DEGs could be used as valuable non-invasive biomarkers for oocyte competence.

Rethinking Tako-tsubo Cardiomyopathy: The Contribution of Myocardial Pathology and Molecular Imaging.

BACKGROUND: Despite substantial research, the mechanisms behind stress Tako-tsubo cardiomyopathy (TTC) remain rather elusive. OBJECTIVE: The purpose of this paper was to provide a detailed review of the mainstream factors underlying the pathophysiology of TTC, highlighting the novel contributions of molecular pathology and in-vivo molecular imaging. METHODS: A careful literature review selected all papers discussing TTC, specifically those providing novel insights from myocardial pathology and cardiac molecular imaging. RESULTS: Results concerning myocardial pathology, defect extension, sites and relationships between functional parameters underline the existence of a causal relationship between a determinant (e.g., the release of catecholamines induced by stress) and an outcome for TTC, which is not limited to a reversible contractile cardiomyopathy, but it includes reversible changes in myocardial perfusion and a long-lasting residual deficit in sympathetic function. Besides, they reinforce the hypothesis that sympathetic nerves may exert a complex control on cardiac contractile function, which is likely to be direct or indirect through metabolism and microvascular perfusion changes during anaerobic and aerobic conditions. CONCLUSION: TTC is characterized by acute transient left ventricular systolic dysfunction, which can be challenging to distinguish from myocardial infarction at presentation. Catecholamineinduced myocardial injury is the most established theory, but other factors, including myocardial metabolism and perfusion, should be considered of utmost importance. Each effort to clarify the numerous pathways and emerging abnormalities may provide novel approaches to treat the acute episode, avoid recurrences, and prevent major adverse cardiovascular events.

The Role of Molecular Imaging in Patients with Brain Metastases: A Literature Review.

Over the last several years, molecular imaging has gained a primary role in the evaluation of patients with brain metastases (BM). Therefore, the "Response Assessment in Neuro-Oncology" (RANO) group recommends amino acid radiotracers for the assessment of BM. Our review summarizes the current use of positron emission tomography (PET) radiotracers in patients with BM, ranging from present to future perspectives with new PET radiotracers, including the role of radiomics and potential theranostics approaches. A comprehensive search of PubMed results was conducted. All studies published in English up to and including December 2022 were reviewed. Current evidence confirms the important role of amino acid PET radiotracers for the delineation of BM extension, for the assessment of response to therapy, and particularly for the differentiation between tumor progression and radionecrosis. The newer radiotracers explore non-invasively different biological tumor processes, although more consistent findings in larger clinical trials are necessary to confirm preliminary results. Our review illustrates the role of molecular imaging in patients with BM. Along with magnetic resonance imaging (MRI), the gold standard for diagnosis of BM, PET is a useful complementary technique for processes that otherwise cannot be obtained from anatomical MRI alone.