The vast majority of brain tumors in adults exhibit glial characteristics. Brain tumors in children are diverse: Many have neuronal characteristics, whereas others have glial features. Here we show that activation of the Gi protein-coupled receptor CXCR4 is critical for the growth of both malignant neuronal and glial tumors. Systemic administration of CXCR4 antagonist AMD 3100 inhibits growth of intracranial glioblastoma and medulloblastoma xenografts by increasing apoptosis and decreasing the proliferation of tumor cells. This reflects the ability of AMD 3100 to reduce the activation of extracellular signal-regulated kinases 1 and 2 and Akt, all of which are pathways downstream of CXCR4 that promote survival, proliferation, and migration. These studies (i) demonstrate that CXCR4 is critical to the progression of diverse brain malignances and (ii) provide a scientific rationale for clinical evaluation of AMD 3100 in treating both adults and children with malignant brain tumors.

The cerebral metabolic rate of oxygen (CMRO 2 ) was dynamically evaluated on a pixel-by-pixel basis in isoflurane-anesthetized and spontaneously breathing rats following graded electrical somatosensory forepaw stimulations (4, 6, and 8mA). In contrast to ␣-chloralose, which is the most widely used anesthetic in forepaw-stimulation fMRI studies of rats under mechanical ventilation, isoflurane (1.1-1.2%) provided a stable anesthesia level over a prolonged period, without the need to adjust the ventilation volume/rate or sample blood gases. Combined cerebral blood flow signals (CBF) and blood oxygenation level-dependent (BOLD) fMRI signals were simultaneously measured with the use of a multislice continuous arterial spin labeling (CASL) technique (two-coil setup). CMRO 2 was calculated using the biophysical BOLD model of Ogawa et al. (Proc Natl Acad Sci USA 1992;89:5951-5955). The stimulus-evoked BOLD percent changes at 4, 6, and 8mA were, respectively, 0.5% ؎ 0.2%, 1.4% ؎ 0.3%, and 2.0% ؎ 0.3% (mean ؎ SD, N ‫؍‬ 6). The CBF percent changes were 23% ؎ 6%, 58% ؎ 9%, and 87% ؎ 14%. The CMRO 2 percent changes were 14% ؎ 4%, 24% ؎ 6%, and 43% ؎ 11%. BOLD, CBF, and CMRO 2 activations were localized to the forepaw somatosensory cortices without evidence of plateau for oxygen consumption, indicative of partial coupling of CBF and CMRO 2 . This study describes a useful forepaw-stimulation model for fMRI, and demonstrate that CMRO 2 Under normal and resting physiological conditions in the brain, almost all (Ͼ99%) of the energy required for adenosine triphosphate (ATP) production is supplied by oxidative metabolism, and the cerebral metabolic rate of oxygen (CMRO 2 ) is tightly coupled to the cerebral blood flow (CBF) and the cerebral metabolic rate of glucose (CMR glucose ) (1). CBF and CMR glucose changes during task-induced increases in neuronal activity have consistently been demonstrated to be similar (ϳ50%) (2,3). However, the magnitude of stimulus-evoked CMRO 2 changes remains controversial. Following Fox et al.'s (2) initial study with positron emission tomography (PET), stimulusevoked CMRO 2 changes were reported as negligible (2,4,5), substantial but smaller than the CBF and CMR glucose increases (6 -10), or markedly increased by 200 -400% (11).CMRO 2 can be measured by various noninvasive techniques, including PET (2,6,12,13), 13 C MR spectroscopy (11,14), direct and indirect H 2 17 O NMR (15), and functional fMRI (fMRI) with biophysical modeling of the blood oxygenation level-dependent (BOLD) signals (7,9,16,17). These techniques all have some unique advantages and disadvantages. PET CMRO 2 measurement is based on the Kety-Schmidt method. Multiple physiological parameters must be deconvolved by the application of complex kinetic models to the data sets that are poor in signal-tonoise ratio (SNR). These measurements also take a long time, and multiple measurements cannot be made dynamically or in a single subject. Although 13 C spectroscopy and H 2 17 O NMR techniques can be quantitative, they have relatively poor...

Tuberous sclerosis complex (TSC) is a familial tumor disorder for which there is no effective medical therapy. Disease-causing mutations in the TSC1 or TSC2 gene lead to increased mammalian target of rapamycin (mTOR) kinase activity in the conserved mTOR signaling pathway, which regulates nutrient uptake, cell growth, and protein translation. The normal function of TSC1 and TSC2 gene products is to form a complex that reduces mTOR kinase activity. Thus, mTOR kinase inhibition may be a useful targeted therapeutic approach. Elevated interferon-gamma (IFN-gamma) expression is associated with decreased severity of kidney tumors in TSC patients and mouse models; therefore, IFN-gamma also has therapeutic potential. We studied cohorts of Tsc2+/- mice and a novel mouse model of Tsc2-null tumors in order to evaluate the efficacy of targeted therapy for TSC. We found that treatment with either an mTOR kinase inhibitor (CCI-779, a rapamycin analog) or with IFN-gamma reduced the severity of TSC-related disease without significant toxicity. These results constitute definitive preclinical data that justify proceeding with clinical trials using these agents in selected patients with TSC and related disorders.

Compelling evidence points to immune cell infiltration as a critical component of successful immunotherapy. However, there are currently no clinically available, non-invasive methods capable of evaluating immune contexture prior to or during immunotherapy. In this study, we evaluate a T cell-specific PET agent, [18F]F-AraG, as an imaging biomarker predictive of response to checkpoint inhibitor therapy. We determined the specificity of the tracer for activated T cells in vitro and in a virally induced model of rhabdomyosarcoma. Of all immune cells tested, activated human CD8+ effector cells showed the highest accumulation of [18F]F-AraG. Isolation of lymphocytes from the rhabdomyosarcoma tumors showed that more than 80% of the intratumoral signal came from accumulation of [18F]F-AraG in immune cells, primarily CD8+ and CD4+. Longitudinal monitoring of MC38 tumor bearing mice undergoing anti-PD-1 treatment revealed differences in signal between PD-1 and isotype antibody-treated mice early into treatment. The differences in [18F]F-AraG signal were also apparent between responders and non-responders to anti-PD-1 therapy. Importantly, we found that the signal in the tumor draining lymph nodes provides key information about response to anti-PD-1 therapy. Overall, [18F]F-AraG has potential to serve as a much needed immunomonitoring clinical tool for timely evaluation of immunotherapy.

PurposePSMA-617 is a small molecule targeting the prostate-specific membrane antigen (PSMA). In this work, we estimate the radiation dosimetry for this ligand labeled with the alpha-emitter 213Bi.MethodsThree patients with metastatic prostate cancer underwent PET scans 0.1 h, 1 h, 2 h, 3 h, 4 h and 5 h after injection of 68Ga-PSMA-617. Source organs were kidneys, liver, spleen, salivary glands, bladder, red marrow and representative tumor lesions. The imaging nuclide 68Ga was extrapolated to the half-life of 213Bi. The residence times of 213Bi were forwarded to the instable daughter nuclides. OLINDA was used for dosimetry calculation. Results are discussed in comparison to literature data for 225Ac-PSMA-617.ResultsAssuming a relative biological effectiveness of 5 for alpha radiation, the dosimetry estimate revealed equivalent doses of mean 8.1 Sv RBE5/GBq for salivary glands, 8.1 Sv RBE5/GBq for kidneys and 0.52 Sv RBE5/GBq for red marrow. Liver (1.2 Sv RBE5/GBq), spleen (1.4 Sv RBE5/GBq), bladder (0.28 Sv RBE5/GBq) and other organs (0.26 SvRBE5/GBq) were not dose-limiting. The effective dose is 0.56 Sv RBE5/GBq. Tumor lesions were in the range 3.2–9.0 SvRBE5/GBq (median 7.6 SvRBE5/GBq). Kidneys would limit the cumulative treatment activity to 3.7 GBq; red marrow might limit the maximum single fraction to 2 GBq. Despite promising results, the therapeutic index was inferior compared to 225Ac-PSMA-617.ConclusionsDosimetry of 213Bi-PSMA-617 is in a range traditionally considered reasonable for clinical application. Nevertheless, compared to 225Ac-PSMA-617, it suffers from higher perfusion-dependent off-target radiation and a longer biological half-life of PSMA-617 in dose-limiting organs than the physical half-life of 213Bi, rendering this nuclide as a second choice radiolabel for targeted alpha therapy of prostate cancer.Electronic supplementary materialThe online version of this article (10.1007/s00259-017-3817-y) contains supplementary material, which is available to authorized users.

Effectiveness of checkpoint immunotherapy in cancer can be undermined by immunosuppressive tumor-associated macrophages (TAMs) with an M2 phenotype. Reprogramming TAMs toward a proinflammatory M1 phenotype is a novel approach to induce antitumor immunity. The M2 phenotype is controlled by key transcription factors such as signal transducer and activator of transcription 6 (STAT6), which have been “undruggable” selectively in TAMs. We describe an engineered exosome therapeutic candidate delivering an antisense oligonucleotide (ASO) targeting STAT6 (exoASO-STAT6), which selectively silences STAT6 expression in TAMs. In syngeneic models of colorectal cancer and hepatocellular carcinoma, exoASO-STAT6 monotherapy results in >90% tumor growth inhibition and 50 to 80% complete remissions. Administration of exoASO-STAT6 leads to induction of nitric oxide synthase 2 ( NOS2 ), an M1 macrophage marker, resulting in remodeling of the tumor microenvironment and generation of a CD8 T cell–mediated adaptive immune response. Collectively, exoASO-STAT6 represents the first platform targeting transcription factors in TAMs in a highly selective manner.

How size and shape of presynaptic active zones are regulated at the molecular level has remained elusive. Here we provide insight from studying rod photoreceptor ribbon-type active zones after disruption of CAST/ERC2, one of the cytomatrix of the active zone (CAZ) proteins. Rod photoreceptors were present in normal numbers, and the a-wave of the electroretinogram (ERG)-reflecting their physiological population response-was unchanged in CAST knock-out (CAST Ϫ/Ϫ ) mice. Using immunofluorescence and electron microscopy, we found that the size of the rod presynaptic active zones, their Ca 2ϩ channel complement, and the extension of the outer plexiform layer were diminished. Moreover, we observed sprouting of horizontal and bipolar cells toward the outer nuclear layer indicating impaired rod transmitter release. However, rod synapses of CAST Ϫ/Ϫ mice, unlike in mouse mutants for the CAZ protein Bassoon, displayed anchored ribbons, normal vesicle densities, clustered Ca 2ϩ channels, and essentially normal molecular organization. The reduction of the rod active zone size went along with diminished amplitudes of the b-wave in scotopic ERGs. Assuming, based on the otherwise intact synaptic structure, an unaltered function of the remaining release apparatus, we take our finding to suggest a scaling of release rate with the size of the active zone. Multielectrode-array recordings of retinal ganglion cells showed decreased contrast sensitivity. This was also observed by optometry, which, moreover, revealed reduced visual acuity. We conclude that CAST supports large active zone size and high rates of transmission at rod ribbon synapses, which are required for normal vision.

The use of functional magnetic resonance imaging (fMRI) in animal models of cocaine addiction is an invaluable tool for investigating the neuroadaptations that lead to this psychiatric disorder. We used blood-oxygen-level-dependent (BOLD) MRI in awake rats to identify the neuronal circuits affected by repeated cocaine administration. Rats were given an injection of cocaine (15 mg/kg, i.p.) or its vehicle for 7 days, abstained from injections for 1 week, and challenged with an intracerebroventricular cocaine injection during functional imaging. Acute cocaine produced robust positive BOLD responses across well-known monoamine-enriched brain regions, such as the prefrontal cortex, nucleus accumbens, dorsal striatum, sensory cortex, hippocampus, thalamus, and midbrain areas. However, repeated cocaine administration resulted in lower BOLD responses in the prefrontal cortex, agranular insular cortex, nucleus accumbens, ventral pallidum, and dorsomedial thalamus, among other brain regions. Reductions in BOLD intensity were not associated with variations in cerebrovascular reactivity between drug naïve rats and those repeatedly exposed to cocaine. Therefore, the lower metabolic activation in response to cocaine could reflect a reduced neuronal and/or synaptic activity upon repeated administration.