Sosuke Miyoshi

The evolutionarily conserved G protein-coupled receptor SREB2/GPR85 influences brain size, behavior, and vulnerability to schizophrenia

The G protein-coupled receptor (GPCR) family is highly diversified and involved in many forms of information processing. SREB2 (GPR85) is the most conserved GPCR throughout vertebrate evolution and is expressed abundantly in brain structures exhibiting high levels of plasticity, e.g., the hippocampal dentate gyrus. Here, we show that SREB2 is involved in determining brain size, modulating diverse behaviors, and potentially in vulnerability to schizophrenia. Mild overexpression of SREB2 caused significant brain weight reduction and ventricular enlargement in transgenic (Tg) mice as well as behavioral abnormalities mirroring psychiatric disorders, e.g., decreased social interaction, abnormal sensorimotor gating, and impaired memory. SREB2 KO mice showed a reciprocal phenotype, a significant increase in brain weight accompanying a trend toward enhanced memory without apparent other behavioral abnormalities. In both Tg and KO mice, no gross malformation of brain structures was observed. Because of phenotypic overlap between SREB2 Tg mice and schizophrenia, we sought a possible link between the two. Minor alleles of two SREB2 SNPs, located in intron 2 and in the 3′ UTR, were overtransmitted to schizophrenia patients in a family-based sample and showed an allele load association with reduced hippocampal gray matter volume in patients. Our data implicate SREB2 as a potential risk factor for psychiatric disorders and its pathway as a target for psychiatric therapy.

Cancer Detection Using a PET Tracer, 11C-Glycylsarcosine, Targeted to H+/Peptide Transporter

H+/peptide transporter, PEPT1, is functionally expressed in some human cancer cell lines and might be a candidate molecular target for detection of cancers in vivo using PET. The aim of the present study was to establish a novel tumor-imaging technology using a PET tracer targeted to H+/peptide transporter(s). We also compared the tracer with 18F-FDG, focusing on the specificity of their accumulation between tumor and inflammatory tissues. Methods: A dipeptide PET tracer, 11C-glycylsarcosine (11C-Gly-Sar), was injected intravenously into athymic mice transplanted with human pancreatic, prostate, and gastric cancer cells. The distribution patterns of 11C-Gly-Sar and 18F-FDG in the tumor-bearing mice, and in mice with inflammatory tissue, were assessed by imaging with a positron planar imaging system (PPIS). Tissue distributions of tracer radioactivity were also measured. The expression levels of PEPT1 and PEPT2 (PEPTs) proteins in tumor xenografts and inflammatory tissue were examined by immunohistochemical analysis. The messenger RNA expression levels of PEPTs in 58 available cancer cell lines were quantified by means of real-time polymerase chain reaction. Results: All 3 tumor xenografts were well visualized with the PPIS after injection of 11C-Gly-Sar. Expression of PEPTs in those xenografts was confirmed by immunohistochemical analysis. Tumor-to-blood concentration ratios of 11C-Gly-Sar increased in a time-dependent manner and were much higher than unity. Most of the radioactivity found in the tumor tissue was recovered as the intact tracer. These results indicated that 11C-Gly-Sar was taken up by the PEPTs in tumor xenografts. It is noteworthy that 11C-Gly-Sar was minimally present in inflammatory tissues that expressed no PEPT1 or PEPT2 protein, whereas 18F-FDG was highly accumulated, with the values of the selectivity index being >25.1 and 0.72 for 11C-Gly-Sar and 18F-FDG, respectively. The mRNAs of PEPT1 and PEPT2 were expressed in 27.6% and 93.1%, respectively, of the cancer cell lines examined in the present study. Conclusion: The present study indicates that 11C-Gly-Sar is a promising tumor-imaging agent and is superior to 18F-FDG for distinguishing between tumors and inflammatory tissue. Because PEPTs were ubiquitously expressed in various types of tumor cells examined, 11C-Gly-Sar could be useful for the detection of many types of cancers.

Amyloid imaging in aged and young macaques with [11C]PIB and [18F]FDDNP

[11C]PIB and [18F]FDDNP were examined on five aged and five young adult male rhesus macaques using positron emission tomography. Both tracers showed increased accumulation in the striatum, thalamus, cingulate and pons in the aged group. Compared to [11C]PIB, [18F]FDDNP showed higher accumulation in the cortical regions of aged animals as well as young animals. Although [18F]FDDNP may have possible usefulness for imaging, including other proteins, [11C]PIB may be better for amyloid imaging owing to lower non‐specific binding. Synapse 62:472–475, 2008.

Mouse Model of Chromosome 15q13.3 Microdeletion Syndrome Demonstrates Features Related to Autism Spectrum Disorder.

The chromosome 15q13.3 microdeletion is a pathogenic copy number variation conferring epilepsy, intellectual disability, schizophrenia, and autism spectrum disorder (ASD). We generated mice carrying a deletion of 1.2 Mb homologous to the 15q13.3 microdeletion in human patients. Here, we report that mice with a heterozygous deletion on a C57BL/6 background (D/+ mice) demonstrated phenotypes including enlarged/heavier brains (macrocephaly) with enlarged lateral ventricles, decreased social interactions, increased repetitive grooming behavior, reduced ultrasonic vocalizations, decreased auditory-evoked gamma band EEG, and reduced event-related potentials. D/+ mice had normal body weight, activity levels, sensory gating, and cognitive abilities and no signs of epilepsy/seizures. Our results demonstrate that D/+ mice represent ASD-related phenotypes associated with 15q13.3 microdeletion syndrome. Further investigations using this chromosome-engineered mouse model may uncover the common mechanism(s) underlying ASD and other neurodevelopmental/psychiatric disorders representing the 15q13.3 microdeletion syndrome, including epilepsy, intellectual disability, and schizophrenia. SIGNIFICANCE STATEMENT Recently discovered pathologic copy number variations (CNVs) from patients with neurodevelopmental/psychiatric disorders show very strong penetrance and thus are excellent candidates for mouse models of disease that can mirror the human genetic conditions with high fidelity. A 15q13.3 microdeletion in humans results in a range of neurodevelopmental/psychiatric disorders, including epilepsy, intellectual disability, schizophrenia, and autism spectrum disorder (ASD). The disorders conferred by a 15q13.3 microdeletion also have overlapping genetic architectures and comorbidity in other patient populations such as those with epilepsy and schizophrenia/psychosis, as well as schizophrenia and ASD. We generated mice carrying a deletion of 1.2 Mb homologous to the 15q13.3 microdeletion in human patients, which allowed us to investigate the potential causes of neurodevelopmental/psychiatric disorders associated with the CNV.

Combination of YM155, a survivin suppressant, with bendamustine and rituximab: A new combination therapy to treat relapsed/refractory diffuse large B-cell lymphoma

Purpose: There remains an unmet therapeutic need for patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL). The purpose of this study was to evaluate the therapeutic potential of sepantronium bromide (YM155), a survivin suppressant, in combination with either bendamustine or both bendamustine and rituximab using DLBCL models. Experimental Design: Human DLBCL cell lines, DB, SU-DHL-8, and WSU-DLCL2, were treated with YM155 in combination with bendamustine. Cell viability, apoptosis induction, protein expression, and cell-cycle distribution were evaluated. Furthermore, antitumor activities of YM155, in combination with bendamustine or both bendamustine and rituximab, were evaluated in mice bearing human DLBCL xenografts. Results: The combination of YM155 with bendamustine showed greater cell growth inhibition and sub-G1 population than either agent alone. YM155 inhibited bendamustine-induced activation of the ATM pathway and accumulation of survivin at G2–M phase, with greater DNA damage and apoptosis than either single agent alone. In a DLBCL DB murine xenograft model, YM155 enhanced the antitumor activity of bendamustine, resulting in complete tumor regression without affecting body weight. Furthermore, YM155 combined with bendamustine and rituximab, decreased FLT-PET signals in lymph nodes and prolonged overall survival of mice bearing disseminated SU-DHL-8, an activated B-cell–like (ABC)-DLBCL xenografts when compared with the combination of either rituximab and bendamustine or YM155 with rituximab. Conclusions: These results support a clinical trial of the combination of YM155 with bendamustine and rituximab in relapsed/refractory DLBCL. Clin Cancer Res; 20(7); 1814–22. ©2014 AACR.

Brain penetration of telmisartan, a unique centrally acting angiotensin II type 1 receptor blocker, studied by PET in conscious rhesus macaques☆

INTRODUCTION Telmisartan is a widely used, long-acting antihypertensive agent. Known to be a selective angiotensin II type 1 (AT(1)) receptor (AT(1)R) blocker (ARB), telmisartan acts as a partial agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and inhibits centrally mediated effects of angiotensin II in rats following peripheral administration, although the brain penetration of telmisartan remains unclear. We investigated the brain concentration and localization of telmisartan using (11)C-labeled telmisartan and positron emission tomography (PET) in conscious rhesus macaques. METHODS Three male rhesus macaques were bolus intravenously administered [(11)C]telmisartan either alone or as a mixture with unlabeled telmisartan (1mg/kg). Dynamic PET images were acquired for 95min following administration. Blood samples were collected for the analysis of plasma concentration and metabolites, and brain and plasma concentrations were calculated from detected radioactivity using the specific activity of the administered drug preparation, in which whole blood radioactivity was used for the correction of intravascular blood radioactivity in brain. RESULTS Telmisartan penetrated into the brain little but enough to block AT(1)R and showed a consistently increasing brain/plasma ratio within the PET scanning period, suggesting slow clearance of the compound from the brain compared to the plasma clearance. Brain/plasma ratios at 30, 60, and 90min were 0.06, 0.13, and 0.18, respectively. No marked localization according to the AT(1)R distribution was noted over the entire brain, even on tracer alone dosing. CONCLUSIONS Telmisartan penetrated into the brain enough to block AT(1)R and showed a slow clearance from the brain in conscious rhesus macaques, supporting the long-acting and central responses of telmisartan as a unique property among ARBs.

Sepantronium Bromide (YM155) Enhances Response of Human B-cell non-Hodgkin Lymphoma to Rituximab

In the treatment of B-cell non-Hodgkin lymphoma (B-NHL) rituximab improves long-term survival in combination with conventional chemotherapy. However, because the majority of patients with B-NHL eventually relapse, the development of more effective therapies is needed. Here, we evaluated the antitumor effects of a combination treatment involving sepantronium bromide (YM155), a first-in-class survivin suppressant, and rituximab in B-NHL xenograft mice models. To determine the efficacy of the combination treatment, YM155- and rituximab-treated B-NHL cell xenografted mice were monitored for tumor size and survival and subjected to 2′-deoxy-2′-18F-fluoro-d-glucose (18F-FDG) and 3′-18F-fluoro-3′-deoxythymidine (18F-FLT) positron emission tomography (PET) imaging. In addition, the cell proliferation status of excised tumors was examined by Ki-67 immunohistochemistry. In DB, WSU-DLCL-2, and Mino xenograft-bearing mice, the combination treatment of YM155 and rituximab induced significant tumor growth inhibition and tumor regression compared with either single agent. On day 3 after the initiation of treatment a significant decrease in both 18F-FDG and 18F-FLT tumor uptake from pretreatment levels was observed in combination treatment groups. The Ki-67 proliferation index was significantly decreased on day 3 in the xenograft models treated with combination treatment, suggesting that the combination of YM155 and rituximab reduced cell proliferation and glucose metabolism. Furthermore, compared with monotherapy, combination treatment prolonged survival times of severe combined immunodeficient mice with disseminated WSU-FSCCL and Jeko B-NHL tumors. Our findings demonstrate that YM155 and rituximab combination treatment enhances antitumor activity in B-NHL xenografts, and 18F-FLT and 18F-FDG PET imaging may allow the early functional evaluation of treatment responses in patients with B-NHL.

Brain Adenosine A2A Receptor Occupancy by a Novel A1/A2A Receptor Antagonist, ASP5854, in Rhesus Monkeys: Relationship to Anticataleptic Effect

The purpose of the present study was to measure adenosine A2A receptor (A2AR) occupancy in the brain by a novel adenosine A1/A2A antagonist, 5-[5-amino-3-(4fluorophenyl)pyrazin-2-yl]-1-isopropylpyridine-2(1H)-one (ASP5854), and to determine the degree of receptor occupancy necessary to inhibit haloperidol-induced catalepsy in rhesus monkeys. Methods: A2AR occupancy by ASP5854 (0.001–0.1 mg/kg) was examined in the striatum using an A2AR-specific radiotracer, 11C-SCH442416, and PET in conscious rhesus monkeys. A2AR occupancy was monitored after a single intravenous administration of ASP5854 in 3 animals, and a dynamic PET scan was performed at 1, 4, and 8 h after an intravenous bolus injection of the tracer for approximately 740 MBq. Catalepsy was induced by haloperidol (0.03 mg/kg, intramuscularly) and examined for incidence and duration. Results: ASP5854 dose-dependently increased A2AR occupancy in the striatum and showed long-lasting occupancy even after the reduction of plasma concentration. Haloperidol induced severe catalepsy at 40 min after intramuscular injection. The incidence and duration of cataleptic posture were dose-dependently reduced by ASP5854 at 1 h after oral administration, and the minimum ED50 value was 0.1 mg/kg. Administration of a dose of 0.1 mg/kg yielded a plasma concentration of 97 ± 16.3 ng/mL, which corresponded to 85%–90% of A2AR occupancy. Conclusion: These results showed that ASP5854 antagonized A2AR in the striatum, and the dissociation from A2AR was relatively slow. In addition, more than 85% A2AR occupancy by ASP5854 resulted in an inhibition of haloperidol-induced catalepsy. Thus, such a pharmacodynamic study directly demonstrates both the kinetics of a drug in the brain and the relationship between dose-dependent receptor occupancy and plasma level.

Inhibition of oligopeptide transporter suppress growth of human pancreatic cancer cells

Oligopeptide transporters are abundantly expressed in various types of cancer cells. We here synthesized two novel dipeptides, l-phenylalanyl sarcosine (Phe-Sar) and 4-(4-methoxyphenyl)-l-phenylalanyl sarcosine (Bip(OMe)-Sar), and examined their effect on the growth of human pancreatic cancer AsPC-1 cells, which are known to highly express oligopeptide transporter PEPT1/SLC15A1. Growth of AsPC-1 cells was inhibited by these two peptides and a typical PEPT1/SLC15A1 substrate Gly-Sar. Growth inhibition by Gly-Sar, Phe-Sar and Bip(OMe)-Sar was concentration-dependent with half-maximal inhibitory concentration of 50, 0.91 and 0.55mM, respectively. These peptides also inhibited PEPT1-mediated [(3)H]Gly-Sar uptake with half-maximal inhibitory concentration of 2.6, 0.81 and 0.27mM, respectively. Thus, the rank order of the tumor cell growth inhibition by these three peptides was the same as that of PEPT1-inhibitory activity. Growth of AsPC-1 cells was also inhibited by 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH), which is a typical inhibitor of amino acid transporter system L. The growth inhibition by BCH and Gly-Sar was additive, suggesting that these compounds act at distinct loci. Oligopeptide transporters thus appear to be a promising target for inhibition of pancreatic cancer progression. These results also proposed the idea that oligopeptide transporter is required for growth of AsPC-1 cells.

Magnetically Targeted Viral Envelopes: A PET Investigation of Initial Biodistribution

Gene and drug therapy for organ-specific diseases in part depends on the efficient delivery to a particular region of the body. We examined the biodistribution of a viral envelope commonly used as a nanoscale gene delivery vehicle using positron emission tomography (PET) and investigated the magnetic alteration of its biodistribution. Iron oxide nanoparticles and 18F-fluoride were encapsulated by hemagglutinating virus of Japan envelopes (HVJ-Es). HVJ-Es were then injected intravenously in the rat and imaged dynamically using high-resolution PET. Control subjects received injections of encapsulated materials alone. For magnetic targeting, permanent magnets were fixed on the head during the scan. Based on the quantitative analysis of PET images, HVJ-Es accumulated in the liver and spleen and activity remained higher than control subjects for 2 h. Histological sections of the liver confirmed imaging findings. Pixel-wise activity patterns on coregistered PET images of the head showed a significantly different pattern for the subjects receiving magnetic targeting as compared to all control groups. Imaging demonstrated the initial biodistribution of a viral envelope within the rodent by providing quantitative behavior over time and in specific anatomical regions. Magnetic force altered the biodistribution of the viral envelope to a target structure, and could enable region-specific delivery of therapeutic vehicles noninvasively.