18F-FAC PET Visualizes Brain-Infiltrating Leukocytes in a Mouse Model of Multiple Sclerosis.

Brain-infiltrating leukocytes contribute to multiple sclerosis (MS) and autoimmune encephalomyelitis and likely play a role in traumatic brain injury, seizure, and stroke. Brain-infiltrating leukocytes are also primary targets for MS disease-modifying therapies. However, no method exists for noninvasively visualizing these cells in a living organism. 1-(2'-deoxy-2'-18F-fluoroarabinofuranosyl) cytosine (18F-FAC) is a PET radiotracer that measures deoxyribonucleoside salvage and accumulates preferentially in immune cells. We hypothesized that 18F-FAC PET could noninvasively image brain-infiltrating leukocytes. Methods: Healthy mice were imaged with 18F-FAC PET to quantify if this radiotracer crosses the blood-brain barrier (BBB). Experimental autoimmune encephalomyelitis (EAE) is a mouse disease model with brain-infiltrating leukocytes. To determine whether 18F-FAC accumulates in brain-infiltrating leukocytes, EAE mice were analyzed with 18F-FAC PET, digital autoradiography, and immunohistochemistry, and deoxyribonucleoside salvage activity in brain-infiltrating leukocytes was analyzed ex vivo. Fingolimod-treated EAE mice were imaged with 18F-FAC PET to assess if this approach can monitor the effect of an immunomodulatory drug on brain-infiltrating leukocytes. PET scans of individuals injected with 2-chloro-2'-deoxy-2'-18F-fluoro-9-β-d-arabinofuranosyl-adenine (18F-CFA), a PET radiotracer that measures deoxyribonucleoside salvage in humans, were analyzed to evaluate whether 18F-CFA crosses the human BBB. Results: 18F-FAC accumulates in the healthy mouse brain at levels similar to 18F-FAC in the blood (2.54 ± 0.2 and 3.04 ± 0.3 percentage injected dose per gram, respectively) indicating that 18F-FAC crosses the BBB. EAE mice accumulate 18F-FAC in the brain at 180% of the levels of control mice. Brain 18F-FAC accumulation localizes to periventricular regions with significant leukocyte infiltration, and deoxyribonucleoside salvage activity is present at similar levels in brain-infiltrating T and innate immune cells. These data suggest that 18F-FAC accumulates in brain-infiltrating leukocytes in this model. Fingolimod-treated EAE mice accumulate 18F-FAC in the brain at 37% lower levels than control-treated EAE mice, demonstrating that 18F-FAC PET can monitor therapeutic interventions in this mouse model. 18F-CFA accumulates in the human brain at 15% of blood levels (0.08 ± 0.01 and 0.54 ± 0.07 SUV, respectively), indicating that 18F-CFA does not cross the BBB in humans. Conclusion: 18F-FAC PET can visualize brain-infiltrating leukocytes in a mouse MS model and can monitor the response of these cells to an immunomodulatory drug. Translating this strategy into humans will require exploring additional radiotracers

Therapeutic opportunities and challenges in targeting the orphan G protein-coupled receptor GPR35

GPR35 is a class A, rhodopsin-like G protein-coupled receptor (GPCR) first identified more than 20 years ago. In the intervening period identification of strong expression in the lower intestine and colon, as well as in a variety of immune cells including monocytes and a variety of dendritic cells, and in dorsal root ganglia, has suggested potential therapeutic opportunities in targeting this receptor in a range of conditions. GPR35 is, however, unusual in a variety of ways that challenge routes to translation. These include that although a substantial range and diversity of endogenous ligands have been suggested as agonist partners for this receptor it officially remains defined as an ‘orphan’ GPCR; that humans express two distinct protein isoform sequences whilst rodents express only a single form, and that the pharmacology of the human and rodent orthologues of GPR35 is very distinct, with variation between rat and mouse GPR35 as marked as between either of these species and the human forms. 2 Herein we provide perspectives on each of the topics above as well as suggesting ways to overcome the challenges currently hindering potential translation. These include better understanding of the extent and molecular basis for species selective GPR35 pharmacology and the production of novel mouse models in which both ‘on-target’ and ‘off-target’ effects of presumptive GPR35 ligands can be better defined as well as clear understanding in human of isoform expression profile and its significance at both tissue and individual cell level

Emergency Department Use in Patients with Cancer: A Population-Based Study

Introduction Emergency Department (ED) visits in cancer patients represent a significant burden to both patients and the health care system. Emergency Care of cancer patients is complex compared to the population. There is lack of knowledge regarding the pattern and reasons for ED visits in this population. Objectives and Approach We sought to identify factors and patterns associated with ED use among cancer patients, in the first year after diagnosis. Adult cancer patients diagnosed between 2011 and 2013 were identified from the Alberta Cancer Registry. This was linked with cancer related treatments extracted from medical records system at provincial cancer centers. ED visits and outpatient clinics were acquired from National Ambulatory Care Reporting System (NACRS). Databases were linked by unique patient identification number. Previous cancer patients were defined by having at least one cancer related diagnosis in NACRS before. The other patients were treated as non-cancer patients. Results Cancer patients accounted for 6.7% of ED visits and 10\% of ED hours. They had higher male percentage (53% vs. 49%), higher admission rate (23% vs. 10%), ambulance usage (20% vs. 12%) and longer stay (LOS) (171 vs. 131 mins) compared to non-cancer patients. 24% of cancer patients had 4 or more ED visits/year and accounted for 59% of visits. Lung and liver cancer patients had higher ED utilization than patients with other cancers. Breast cancer patients had more after-treatment-ED-visits (41% within a week vs. 26% in lung cancer). Use of ED was highest within 1 month of diagnosis for all types except breast cancer, which was highest at 2 months after. Differences were observed between urban and rural area for numbers reported above. Conclusion/Implications These data suggest high ED utilization by cancer patients, and variation in utilization by cancer type. Identifying the timing and risk factors of ED visit for each cancer type, especially on frequent ED users presents opportunities to improve care in oncology clinics and ED

Interim-treatment quantitative PET parameters predict progression and death among patients with hodgkin's disease

PURPOSE: We hypothesized that quantitative PET parameters may have predictive value beyond that of traditional clinical factors such as the International Prognostic Score (IPS) among Hodgkin's disease (HD) patients. METHODS: Thirty HD patients treated at presentation or relapse had staging and interim-treatment PET-CT scans. The majority of patients (53%) had stage III-IV disease and 67% had IPS ≥ 2. Interim-treatment scans were performed at a median of 55 days from the staging PET-CT. Chemotherapy regimens used: Stanford V (67%), ABVD (17%), VAMP (10%), or BEACOPP (7%). Hypermetabolic tumor regions were segmented semiautomatically and the metabolic tumor volume (MTV), mean standardized uptake value (SUVmean), maximum SUV (SUVmax) and integrated SUV (iSUV) were recorded. We analyzed whether IPS, absolute value PET parameters or the calculated ratio of interim- to pre-treatment PET parameters were associated with progression free survival (PFS) or overall survival (OS). RESULTS: Median follow-up of the study group was 50 months. Six of the 30 patients progressed clinically. Absolute value PET parameters from pre-treatment scans were not significant. Absolute value SUVmax from interim-treatment scans was associated with OS as determined by univariate analysis (p < 0.01). All four calculated PET parameters (interim/pre-treatment values) were associated with OS: MTV(int/pre )(p < 0.01), SUVmean(int/pre )(p < 0.05), SUVmax(int/pre )(p = 0.01), and iSUV(int/pre )(p < 0.01). Absolute value SUVmax from interim-treatment scans was associated with PFS (p = 0.01). Three calculated PET parameters (int/pre-treatment values) were associated with PFS: MTV(int/pre )(p = 0.01), SUVmax(int/pre )(p = 0.02) and iSUV(int/pre )(p = 0.01). IPS was associated with PFS (p < 0.05) and OS (p < 0.01). CONCLUSIONS: Calculated PET metrics may provide predictive information beyond that of traditional clinical factors and may identify patients at high risk of treatment failure early for treatment intensification

Receptor selectivity between the G proteins Gα12 and Gα13 is defined by a single leucine-to-isoleucine variation

Despite recent advances in structural definition of GPCR–G protein complexes, the basis of receptor selectivity between G proteins remains unclear. The Gα12 and Gα13 subtypes together form the least studied group of heterotrimeric G proteins. G protein–coupled receptor 35 (GPR35) has been suggested to couple efficiently to Gα13 but weakly to Gα12. Using combinations of cells genome-edited to not express G proteins and bioluminescence resonance energy transfer–based sensors, we confirmed marked selectivity of GPR35 for Gα13. Incorporating Gα12/Gα13 chimeras and individual residue swap mutations into these sensors defined that selectivity between Gα13 and Gα12 was imbued largely by a single leucine-to-isoleucine variation at position G.H5.23. Indeed, leucine could not be substituted by other amino acids in Gα13 without almost complete loss of GPR35 coupling. The critical importance of leucine at G.H5.23 for GPR35–G protein interaction was further demonstrated by introduction of this leucine into Gαq, resulting in the gain of coupling to GPR35. These studies demonstrate that Gα13 is markedly the most effective G protein for interaction with GPR35 and that selection between Gα13 and Gα12 is dictated largely by a single conservative amino acid variation.—Mackenzie, A. E., Quon, T., Lin, L.-C., Hauser, A. S., Jenkins, L., Inoue, A., Tobin, A. B., Gloriam, D. E., Hudson, B. D., Milligan, G. Receptor selectivity between the G proteins Gα12 and Gα13 is defined by a single leucine-to-isoleucine variation

Conservation of core gene expression in vertebrate tissues

Abstract Background Vertebrates share the same general body plan and organs, possess related sets of genes, and rely on similar physiological mechanisms, yet show great diversity in morphology, habitat and behavior. Alteration of gene regulation is thought to be a major mechanism in phenotypic variation and evolution, but relatively little is known about the broad patterns of conservation in gene expression in non-mammalian vertebrates. Results We measured expression of all known and predicted genes across twenty tissues in chicken, frog and pufferfish. By combining the results with human and mouse data and considering only ten common tissues, we have found evidence of conserved expression for more than a third of unique orthologous genes. We find that, on average, transcription factor gene expression is neither more nor less conserved than that of other genes. Strikingly, conservation of expression correlates poorly with the amount of conserved nonexonic sequence, even using a sequence alignment technique that accounts for non-collinearity in conserved elements. Many genes show conserved human/fish expression despite having almost no nonexonic conserved primary sequence. Conclusions There are clearly strong evolutionary constraints on tissue-specific gene expression. A major challenge will be to understand the precise mechanisms by which many gene expression patterns remain similar despite extensive cis-regulatory restructuring

Structure-activity relationship studies of tetrahydroquinolone free fatty acid receptor 3 modulators

Free fatty acid receptor 3 (FFA3, previously GPR41) is activated by short-chain fatty acids, mediates health effects of the gut microbiota, and is a therapeutic target for metabolic and inflammatory diseases. The shortage of well-characterized tool compounds has however impeded progress. Herein, we report structure–activity relationship of an allosteric modulator series and characterization of physicochemical and pharmacokinetic properties of selected compounds, including previous and new tools. Two representatives, 57 (TUG-1907) and 63 (TUG-2015), showed improved solubility and preserved potency. Of these, 57, with EC50 = 145 nM and a solubility of 33 μM, showed high clearance in vivo but is a preferred tool in vitro. In contrast, 63, with EC50 = 162 nM and a solubility of 9 μM, showed lower clearance and seems better suited for in vivo studies. Using 57, we demonstrate for the first time that FFA3 activation leads to calcium mobilization in murine dorsal root ganglia

SUPPORT Tools for evidence-informed health Policymaking (STP) 12: Finding and using research evidence about resource use and costs

This article is part of a series written for people responsible for making decisions about health policies and programmes and for those who support these decision makers

FLT-PET-CT for the Detection of Disease Recurrence After Stereotactic Ablative Radiotherapy or Hyperfractionation for Thoracic Malignancy: A Prospective Pilot Study

Differentiating local recurrence from post-treatment changes on PET scans following stereotactic ablative radiotherapy (SABR) or hyperfractionation for lung tumors is challenging. We performed a prospective pilot study of 3-deoxy-3-[18F]-fluorothymidine (FLT)-PET-CT in patients with equivocal post-radiation FDG-PET-CT to assess disease recurrence.Methods: We prospectively enrolled 10 patients, 9 treated with SABR and 1 with hyperfractionated external beam radiotherapy for thoracic malignancy with subsequent equivocal follow-up FDG-PET-CT, to undergo FLT-PET-CT prior to biopsy or serial imaging. FLT-PET scans were interpreted by a radiologist with experience in reading FLT-PET-CT and blinded to the results of any subsequent biopsy or imaging.Results: Of the 10 patients enrolled, 8 were evaluable after FLT-PET-CT. Based on the FLT-PET-CT, a blinded radiologist accurately predicted disease recurrence vs. inflammatory changes in 7 patients (87.5%). The combination of higher lesion SUVmax and higher ratio of lesion SUVmax to SUVmax of mediastinal blood pool was indicative of recurrence. Qualitative assessment of increased degree of focality of the lesion also appears to be indicative of disease recurrence.Conclusion: Adjunctive FLT-PET-CT imaging can complement FDG-PET-CT scan in distinguishing post-treatment radiation changes from disease recurrence in thoracic malignancies. These findings support the investigation of FLT-PET-CT in a larger prospective study