Synthesis, biodistribution and micro-PET imaging of radiolabeled antimitotic agent T138067 analogues

Radiolabeled antimitotic agents [11C]T138067 and [18F]T138067 have been synthesized for evaluation as new potential positron emission tomography (PET) biomarkers for cancer imaging. In vivo biodistribution and micro-PET imaging of [11C]T138067 were performed in breast cancer animal models MCF-7 transfected with IL-1alpha implanted athymic mice and MDA-MB-435 implanted athymic mice. The results suggest that the uptakes of [11C]T138067 in both MCF-7 transfected with IL-1alpha tumor and MDA-MB-435 tumor are non-specific binding.     

Synthesis and preliminary biological evaluation of 6-O-[11C]-[(methoxymethyl)benzyl]guanines,new potential PET breast cancer imaging agents for the DNA repair protein AGT

Novel radiolabeled O(6)-benzylguanine derivatives, 6-O-[(11)C]-[(methoxymethyl)benzyl]guanines ([(11)C]p-O(6)-MMBG, 1a; [(11)C]m-O(6)-MMBG, 1b; ([(11)C]o-O(6)-MMBG, 1c), have been synthesized for evaluation as new potential positron emission tomography (PET) breast cancer imaging agents for DNA repair protein, O(6)-alkylguanine-DNA alkyltransferase (AGT).     

Design and synthesis of carbon-11-labeled dual aromatase–steroid sulfatase inhibitors as new potential PET agents for imaging of aromatase and steroid sulfatase expression in breast cancer

Aromatase and steroid sulfatase (STS) are particularly attractive targets in the treatment of estrogen-receptor-positive breast cancer and the development of enzyme-based cancer imaging agents for the biomedical imaging technique positron emission tomography (PET). New carbon-11-labeled sulfamate derivatives were first designed and synthesized as potential PET dual aromatase–steroid sulfatase inhibitor (DASSI) radiotracers for imaging of aromatase and STS expression in breast cancer. The target tracers 5-(((4-cyanophenyl)(4H-1,2,4-triazol-4-yl)amino)methyl)-2-[¹¹C]methoxyphenyl sulfamate ([¹¹C]8a) and 4-(((4-cyanophenyl)(4H-1,2,4-triazol-4-yl)amino)methyl)-2-[¹¹C]methoxyphenyl sulfamate ([¹¹C]8b) were prepared from their corresponding precursors 5-(((4-cyanophenyl)(4H-1,2,4-triazol-4-yl)amino)methyl)-2-hydroxyphenyl sulfamate (16) and 4-(((4-cyanophenyl)(4H-1,2,4-triazol-4-yl)amino)methyl)-2-hydroxyphenyl sulfamate (21) with [¹¹C]CH₃OTf under basic conditions through the O-[¹¹C]methylation and isolated by the reversed-phase high pressure liquid chromatography (HPLC) method in 30–45% radiochemical yields based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB). The specific activity at end of synthesis (EOS) was 111–185 GBq/μmol.     

Accomodation of S-cis-tamoxifen-N(2)-guanine adduct within a bent and widened DNA minor groove

The non-steroidal anti-estrogen tamoxifen [TAM] has been in clinical use over the last two decades as a potent adjunct chemotherapeutic agent for treatment of breast cancer. It has also been given prophylactically to women with a strong family history of breast cancer. However, tamoxifen treatment has also been associated with increased endometrial cancer, possibly resulting from the reaction of metabolically activated tamoxifen derivatives with cellular DNA. Such DNA adducts can be mutagenic and the activities of isomeric adducts may be conformation-dependent. We therefore investigated the high resolution NMR solution conformation of one covalent adduct (cis-isomer, S-epimer of [TAM]G) formed from the reaction of tamoxifen [TAM] to N(2)-of guanine in the d(C-[TAM]G-C).d(G-C-G) sequence context at the 11-mer oligonucleotide duplex level. Our NMR results establish that the S-cis [TAM]G lesion is accomodated within a widened minor groove without disruption of the Watson-Crick [TAM]G. C and flanking Watson-Crick G.C base-pairs. The helix axis of the bound DNA oligomer is bent by about 30 degrees and is directed away from the minor groove adduct site. The presence of such a bulky [TAM]G adduct with components of the TAM residue on both the 5'- and the 3'-side of the modified base could compromise the fidelity of the minor groove polymerase scanning machinery.     

Preclinical molecular imaging of the translocator protein (TSPO) in a metastases model based on breast cancer xenografts propagated in the murine brain

Previous studies have demonstrated the feasibility of translocator protein (TSPO) imaging to visualize and quantify human breast adenocarcinoma (MDA-MB-231) cells in vivo using a TSPO-targeted near-infrared (NIR) probe (NIR-conPK11195). This study aimed to extend the use of the TSPO-targeted probe to a more biologically relevant and clinically important tumor microenvironment as well as to assess our ability to longitudinally detect the presence and progression of breast cancer cells in the brain. The in vivo biodistribution and accumulation of NIR-conPK11195 and free (unconjugated) NIR dye were quantitatively evaluated in intracranial MDA-MB-231-bearing mice and non-tumor-bearing control mice longitudinally once a week from two to five weeks post-inoculation. The in vivo time-activity curves illustrate distinct clearance profiles for NIR-conPK11195 and free NIR dye, resulting in preferential accumulation of the TSPO-targeted probe in the intracranial tumor bearing hemisphere (TBH) with significant tumor contrast over normal muscle tissue (p < 0.005 at five weeks; p < 0.01 at four weeks). In addition, the TSPO-labeled TBHs demonstrated significant contrast over the TBHs of mice injected with free NIR dye (p < 0.001 at four and five weeks) as well as over the TSPO-labeled non-tumor-bearing hemispheres (NTBHs) of control mice (p < 0.005 at four and five weeks). Overall, TSPO-targeted molecular imaging appears useful for visualizing and quantifying breast cancer xenografts propagated in the murine brain and may assist in preclinical detection, diagnosis and monitoring of metastatic disease as well as drug discovery. Furthermore, these results indicate it should be possible to perform TSPO-imaging of breast cancer cells in the brain using radiolabeled TSPO-targeted agents, particularly in light of the fact that [11C]-labeled TSPO probes such as [11C]-PK 11195 have been successfully used to image gliomas in the clinic.     

Synthesis of carbon-11-labeled casimiroin analogues as new potential PET agents for imaging of quinone reductase 2 and aromatase expression in breast cancer

Carbon-11-labeled casimiroin analogues were first designed and synthesized as new potential PET agents for imaging of quinone reductase (QR) 2 and aromatase expression in breast cancer. [¹¹C]casimiroin (6-[¹¹C]methoxy-9-methyl-[1,3]dioxolo[4,5-h]quinolin-8(9H)-one, [¹¹C]11) and its carbon-11-labeled analogues 5,6,8-trimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]17), 8-methoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21a), 6,8-dimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21b), and 5,8-dimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21c), were prepared from their corresponding precursors with [¹¹C]methyl triflate ([¹¹C]CH₃OTf) under basic conditions (NaH) through either O- or N-[¹¹C]methylation and isolated by semi-preparative HPLC method in 40-50% radiochemical yields decay corrected to end of bombardment (EOB), based on [¹¹C]CO₂, and 111-185 GBq/μmol specific activity at the end of synthesis (EOS).     

BRCA1 mutations in African Americans

The breast cancer predisposing gene, BRCA1, was analyzed for germline mutations in 45 African American families at high-risk for hereditary breast cancer. Patients were considered high-risk if they had a family history of the disease, early onset breast cancer, bilateral breast cancer, or breast and ovarian cancer. The entire BRCA1 coding and flanking intron regions have been examined by single stranded conformation polymorphism analysis followed by sequencing of variant bands. Eleven different BRCA1 germline mutations/variations were identified in 7 patients from the 45 high-risk families. Two pathogenic, protein-truncating mutations were detected in exon 11. A ten base pair tandem duplication, 943ins10, was present in a woman with breast and ovarian cancer whose first-degree relatives had prostate cancer. A four base pair deletion, 3450del4, was detected in a breast cancer patient with five cases of breast cancer in the family; two of the proband's sisters with breast cancer also carried the same mutation. Four amino acid substitutions (Lys1183Arg, Leu1564Pro, Gln1785His, and Glu1794Asp) and four nucleotide substitutions in intron 22 (IVS22+78 C/A, IVS22+67 T/C, IVS22+8 T/A and IVS22+7 T/C) were observed in patients and not in control subjects. One early onset breast cancer patient carried five distinct BRCA1 variations, two amino acid substitutions and three substitutions in intron 22. An amino acid substitution in exon 11, Ser1140Gly, was identified in 3 different unrelated patients and in 6 of 92 control samples. The latter probably represents a benign polymorphism. Electronic Publication     

11C]sorafenib: radiosynthesis and preliminary PET study of brain uptake in P-gp/Bcrp knockout mice

Sorafenib (Nexavar, BAY43-9006, 1) is a second-generation, orally active multikinase inhibitor that is approved for the treatment of some cancers in patients. In this Letter, we developed [¹¹C]1 as a novel positron emission tomography (PET) probe, and evaluated the influence of ABC transporters-mediated efflux on brain uptake using PET with [¹¹C]1 in P-glycoprotein (P-gp)/breast cancer resistance protein (Bcrp) knockout mice versus wild-type mice. [¹¹C]1 was synthesized by the reaction of hydrochloride of aniline 2 with [¹¹C]phosgene ([¹¹C]COCl₂) to give isocyanate [¹¹C]6, followed by reaction with another aniline 3. Small-animal PET study with [¹¹C]1 indicated that the radioactivity level (AUC_0-60 min, SUV × min) in the brains of P-gp/Bcrp knockout mice was about three times higher than in wild-type mice.     

The pattern of clinical breast cancer metastasis correlates with a single nucleotide polymorphism in the C1qA component of complement

Complement is one of primary defense mechanisms against intravascular microorganisms and could play a role in the immune response to malignancy and hence its clinical behavior. We evaluated if the sole coding polymorphism of C1qA associates with outcome in patients with breast carcinoma. Genotyping for C1qA_[276A/G] was performed in 63 breast cancer subjects with localized tumor and compared with that in 38 breast cancer subjects with metastasis. Established risk factors for clinical outcome were considered and evaluated in multivariable analysis. Breast cancer subjects with heterozygous or homozygous C1qA_[276G] genotype had a higher rate of metastasis than subjects with the homozygous C1qA_[276A] genotype [hazard ratio (HR) 2.4, 95% confidence interval (CI) 1.1–4.1]. This association was stronger when only metastatic sites associated with hematogenous spread, i.e., to the bone, liver, and brain, were considered (HR 3.5, 95% CI 1.4–5.6) and remained statistically significant after adjustment for the number of positive lymph nodes, estrogen receptor status, and progesterone receptor status. There was no statistical difference in the C1qA_[276A/G] allelic distribution between all subjects with breast cancer and controls. These results suggest there could be an association of a single nucleotide polymorphism at position 276 of the C1qA component of complement with breast cancer metastasis to sites linked to hematogenous spread of disease. The C1qA polymorphism associated with decreased distant metastasis has also been correlated with an increased incidence of subcutaneous systemic lupus and C1q deficiencies, suggesting that an altered immune response may play a role in the observed association. Supported in part by National Institute of Health grant R21-CA90822, Friends You Can Count On! grant 1-87093-00, and the Woody and Louise White Cancer Research Fund.     

Analysis of DNA adducts by accelerator mass spectrometry in human breast tissue after administration of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and benzo[a]pyrene

Epidemiological evidence has suggested an association between meat consumption and the risk of breast cancer. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine found in cooked meat, has been implicated in the aetiology of breast cancer and has been shown to induce tumour formation in rodent mammary glands. In addition, polycyclic aromatic hydrocarbons, such as benzo[a]pyrene (B[a]P) which has also been shown to induce tumour formation at a number of sites in rodents including the breast, are produced during the cooking of meat through the pyrolysis of fats. The aim of this study was to examine the bioavailability of these compounds to human breast tissue and their ability to bind to DNA to form DNA adducts. Patients undergoing breast surgery at York District Hospital were orally administered prior to surgery a capsule containing 20microg of 14C PhIP (182kBq, specific activity 2.05GBq/mmol) or 5microg of 14C B[a]P (36kBq, specific activity 1.81GBq/mmol). At surgery, normal and tumour breast tissue was resected and tissue concentrations of carcinogen measured by liquid scintillation counting and DNA adduct levels by accelerator mass spectrometry (AMS) were subsequently determined. It was found that both 14C PhIP and 14C B[a]P were able to reach the target organ where they had the ability to form DNA adducts. The level of adducts ranged from 26.22-477.35 and 6.61-208. 38 adducts/10(12) nucleotides following administration of 14C PhIP and 14C B[a]P, respectively, with no significant difference observed between levels in normal or tumour tissue. In addition, the data obtained in this study were comparable to adduct levels previously found in colon samples following administration of the same compounds to individuals undergoing colorectal surgery. This is the first report that these two carcinogens bind to human breast DNA after administration of a defined low dose.     

长链非编码RNA RP11-214F16.8 促进乳腺癌细胞增殖

长链非编码RNAs (long non-coding RNAs, lncRNAs)在乳腺癌发生发展中的作用备受瞩目。本研究通过大数据分析发现,lncRNA RP11-214F16.8在乳腺癌组织中的表达量显著高于正常组织,且其表达量与乳腺癌患者预后负相关。因此,本文采用qRT-PCR技术,在收集的临床样本中验证RP11-214F16.8的表达,证实其在乳腺癌组织中相对表达量为5.65±0.72,其在癌旁组织中表达量为2.63±0.35,且RP11-214F16.8的表达量与乳腺癌瘤体大小和临床TNM分期相关。此外发现,RP11-214F16.8在乳腺癌细胞中的表达量高于正常乳腺上皮细胞。在乳腺癌MCF-7细胞中,过表达RP11-214F16.8后,MCF-7细胞的增殖能力显著增强。而在MDA-MB-231细胞中,敲低RP11-214F16.8的表达,获得相反的结果。进一步研究发现,RP11-214F16.8可上调细胞周期蛋白 D3、CDK4的表达,而下调p18蛋白表达量,进而加速细胞增殖。总之,RP11-214F16.8在乳腺癌中高表达,且促进乳腺癌细胞增殖,进而推动乳腺癌进程。这一研究发现,将为乳腺癌发生发展的网络机制研究提供新的理论依据。     

The effect of flavonoid derivatives on doxorubicin transport and metabolism

This study investigated the effect of naturally occurring flavonoids and synthetic aurone derivatives on the formation of cardiotoxic doxorubicinol and transport of doxorubicin in breast cancer cells. Quercetin significantly inhibited the formation of doxorubicinol. Quercetin and aurones did not significantly affect transport of [14C]doxorubicin in human resistant breast cancer cells. In conclusion, quercetin should be further tested for its potency to decrease doxorubicin-mediated toxicity.     

11 beta-chloromethyl-[3H]estradiol-17 beta: a very high affinity, reversible ligand for the estrogen receptor

It has been suggested that binding of 11 beta-chloromethyl estradiol (11 beta-CME2) to the estrogen receptor is irreversible, since its complex with receptor fails to undergo exchange with estradiol (E2). To investigate this behavior directly, 11 beta-CME2 was prepared in high specific activity, tritium-labeled form: The binding of [3H]11 beta-CME2 to the estrogen receptor from lamb and rat uterus and MCF-7 human breast cancer cells was shown to be fully reversible; the 11 beta-CME2 complex with receptor, as well as that of a structural analog 11 beta-ethyl estradiol, however, do not dissociate or exchange with [3H]E2 over a 22 h period at 25 degrees C. By competitive or direct binding assays, the affinity of 11 beta-CME2 for the estrogen receptor can be estimated to be as much as 10- to 30-fold higher than that of E2. The complexes of estrogen receptor from MCF-7 cells with [3H]11 beta-CME2 and [3H]E2 show identical velocity sedimentation profiles on sucrose gradients, under conditions when the receptor is either a monomer of a dimer. Because of its very high affinity and unusual dissociation kinetics, [3H]11 beta-CME2 should be a very useful ligand for studies of estrogen receptor dynamics and in the assay of estrogen receptor concentrations in tumors and tissues.     

Novel positron emission tomography tracer distinguishes normal from cancerous cells

Development of tumor-specific probes for imaging by positron emission tomography has broad implications in clinical oncology, such as diagnosis, staging, and monitoring therapeutic responses in patients, as well as in biomedical research. Thymidylate synthase (TSase)-based de novo biosynthesis of DNA is an important target for drug development. Increased DNA replication in proliferating cancerous cells requires TSase activity, which catalyzes the reductive methylation of dUMP to dTMP using (R)-N(5),N(10)-methylene-5,6,7,8-tetrahydrofolate (MTHF) as a cofactor. In principle, radiolabeled MTHF can be used as a substrate for this reaction to identify rapidly dividing cells. In this proof-of-principle study, actively growing (log phase) breast cancer (MCF7, MDA-MB-231, and hTERT-HME1), normal breast (human mammary epithelial and MCF10A), colon cancer (HT-29), and normal colon (FHC) cells were incubated with [(14)C]MTHF in culture medium from 30 min to 2 h, and uptake of radiotracer was measured. Cancerous cell lines incorporated significantly more radioactivity than their normal counterparts. The uptake of radioactively labeled MTHF depended upon a combination of cell doubling time, folate receptor status, S phase percentage, and TSase expression in the cells. These findings suggest that the recently synthesized [(11)C]MTHF may serve as a new positron emission tomography tracer for cancer imaging.     

Absence of linkage to the ataxia telangiectasia locus in familial breast cancer

Heterozygotes for ataxia-telangiectasia (AT) are known to have an increased risk of breast cancer. The gene (or genes) responsible for almost all cases of AT has been localised to chromosome 11q by genetic linkage analysis. To examine the possibility that AT heterozygosity may account for a substantial proportion of familial breast cancer, we have typed five markers on chromosome 11q in 16 breast cancer families. We have found no evidence for linkage between breast cancer and chromosome 11q markers and conclude that the contribution of AT to familial breast cancer is likely to be minimal.     

Metformin Decouples Phospholipid Metabolism in Breast Cancer Cells

Introduction

The antidiabetic drug metformin, currently undergoing trials for cancer treatment, modulates lipid and glucose metabolism both crucial in phospholipid synthesis. Here the effect of treatment of breast tumour cells with metformin on phosphatidylcholine (PtdCho) metabolism which plays a key role in membrane synthesis and intracellular signalling has been examined.

Methods

MDA-MB-468, BT474 and SKBr₃ breast cancer cell lines were treated with metformin and [³H-methyl]choline and [¹⁴C(U)]glucose incorporation and lipid accumulation determined in the presence and absence of lipase inhibitors. Activities of choline kinase (CK), CTP:phosphocholine cytidylyl transferase (CCT) and PtdCho-phospholipase C (PLC) were also measured. [³H] Radiolabelled metabolites were determined using thin layer chromatography.

Results

Metformin-treated cells exhibited decreased formation of [³H]phosphocholine but increased accumulation of [³H]choline by PtdCho. CK and PLC activities were decreased and CCT activity increased by metformin-treatment. [¹⁴C] incorporation into fatty acids was decreased and into glycerol was increased in breast cancer cells treated with metformin incubated with [¹⁴C(U)]glucose.

Conclusion

This is the first study to show that treatment of breast cancer cells with metformin induces profound changes in phospholipid metabolism.     

Synthesis of carbon-11 labeled fluorinated 2-arylbenzothiazoles as novel potential PET cancer imaging agents

Fluorinated 2-arylbenzothiazoles are new potential antitumor drugs, which show potent and selective inhibitory activity against breast, lung, and colon cancer cell lines. Carbon-11 labeled fluorinated 2-arylbenzothiazoles may serve as novel probes for positron emission tomography (PET) to image tyrosine kinase in cancers. The preparation of 4-fluorinated 2-arylbenzothiazoles 4-fluoro-2-(3-benzloxy-4-methoxyphenyl)benzothiazole (6a) and 4-fluoro-2-(3,4-dimethoxyphenyl)benzothiazole (6b) was achieved by a modification of Jacobson thioanilide radical cyclization chemistry. Hydrogenolytic cleavage of the benzyl ether group of compound 6a using H₂/Pd–C provided the precursor 4-fluoro-2-(3-hydroxy-4-methoxyphenyl)benzothiazole (7) for radiolabeling. Synthesis of radiolabeling precursors and the reference standards 5- and 6-fluorinated arylbenzothiazoles (11c–n) was achieved via the reaction of o-aminothiophenol disulfides with substituted benzaldehydes under reducing conditions. The target radiotracers carbon-11 labeled 4-, 5-, and 6-fluorinated arylbenzothiazoles (3-[¹¹C]6b, 4-[¹¹C]11c, 3-[¹¹C]11c, 5-[¹¹C]11f, 4-[¹¹C]11f, 4-[¹¹C]11i, 3-[¹¹C]11i, 5-[¹¹C]11l, and 4-[¹¹C]11l) were prepared by O-[¹¹C]methylation of the phenolic hydroxyl precursors (7, 11d, 11e, 11g, 11h, 11j, 11k, 11m, and 11n) with [¹¹C]methyl triflate and isolated by solid-phase extraction (SPE) purification in 30–55% radiochemical yields.     

Is p53 intronic variant G13964C associated with predisposition to cancer?

Germline mutations of the p53 gene confer a high risk of diverse malignancies. The highest frequency of inherited p53 defects was noted in Li-Fraumeni syndrome (LFS), but almost half of the mutations were found in families with incomplete Li-Fraumeni-like syndrome (LFL), including familial breast cancer cases. Recently, a germline intronic G13964C base change of the p53 was reported as a high-risk mutation associated with familial breast cancer (LEHMAN et al. 2000). We genotyped Polish cancer patients and healthy control individuals for the G13964C variant. Patients were chosen from cancer families with phenotypes typical for germline mutations of p53 (LFS, LFL), BRCA1 [hereditary breast (ovarian) cancer, HB(O)C] or a complex consistent with both LFL and HB(O)C. Children with leukemia were included in the study as another high risk group (FELIX et al. 1992). The G13964C variant was detected in six of 87 (6.9%) cancer patients (including two ALL children), but also in eight of 96 (8.3%) control individuals (p > 0.4). Thus we found no evidence of the variant's association with a high risk of cancer.     

Breast and ovarian cancer incidence in BRCA1-mutation carriers. Breast Cancer Linkage Consortium.

Dominant predisposition to early-onset breast cancer and/or ovarian cancer in many families is known to be the result of germ-line mutations in a gene on chromosome 17q, known as BRCA1. In this paper we use data from families with evidence of linkage to BRCA1 to estimate the age-specific risks of breast and ovarian cancer in BRCA1-mutation carriers and to examine the variation in risk between and within families. Under the assumption of no heterogeneity of risk between families, BRCA1 is estimated to confer a breast cancer risk of 54% by age 60 years (95% confidence interval [CI] 27%-71%) and an ovarian cancer risk of 30% by age 60 years (95% CI 8%-47%). Similar lifetime-risk estimates are obtained by examining the risks of contralateral breast cancer and of ovarian cancer, in breast cancer cases in linked families. However, there is significant evidence of heterogeneity of risk between families; a much better fit to the data is obtained by assuming two BRCA1 alleles, one conferring a breast cancer risk of 62% and an ovarian cancer risk of 11% by age 60 years, the other conferring a breast cancer risk of 39% and an ovarian cancer risk of 42%, with the first allele representing 71% of all mutations (95% CI 55%-87%). There is no evidence of clustering of breast and ovarian cancer cases within families.     

Synthesis and evaluation of 4-(2-fluoro-4-[11C]methoxyphenyl)-5-((2-methylpyridin-4-yl)methoxy)picolinamide for PET imaging of the metabotropic glutamate receptor 2 in the rat brain

Metabotropic glutamate receptor 2 (mGluR2) has been suggested as a therapeutic target for treating schizophrenia-like symptoms arising from increased glutamate transmission in the human forebrain. However, no reliable positron emission tomography (PET) radiotracer allowing for in vivo visualization of mGluR2 in the human brain is currently available. In this study, we synthesized 4-(2-fluoro-4-[¹¹C]methoxyphenyl)-5-((2-methylpyridin-4-yl)methoxy)picolinamide ([¹¹C]1) and evaluated its potential as a PET tracer for imaging mGluR2 in the rodent brain. Compound 1, a negative allosteric modulator (NAM) of mGluR2, showed high in vitro binding affinity (IC₅₀: 26?nM) for mGluR2 overexpressed in human cells. [¹¹C]1 was synthesized by O-[¹¹C]methylation of the phenol precursor 2 with [¹¹C]methyl iodide. After the reaction, HPLC purification and formulation, [¹¹C]1 of 7.4?±?2.8?GBq (n?=?8) was obtained from [¹¹C]carbon dioxide of 22.5?±?4.8?GBq (n?=?8) with >99% radiochemical purity and 70?±?32?GBq/μmol (n?=?8) molar activity at the end of synthesis. In vitro autoradiography for rat brains showed that [¹¹C]1 binding was heterogeneously distributed in the cerebral cortex, striatum, hippocampus, and cerebellum. This pattern is consistent with the regional distribution pattern of mGluR2 in the rodent brain. The radioactivity was significantly reduced by self- or MNI-137 (a mGluR2 NAM) blocking. Small-animal PET studies indicated a low in vivo specific binding of [¹¹C]1 in the rat brain. The brain uptake was increased in a P-glycoprotein and breast cancer resistant protein double knockout mouse, when compared to a wild-type mouse. While [¹¹C]1 presented limited potential as an in vivo PET tracer for mGluR2, we suggested that it can be used as a lead compound for developing new radiotracers with improved in vivo brain properties.