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1.
Nat Commun ; 10(1): 4673, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31611594

RESUMO

Advances in precision molecular imaging promise to transform our ability to detect, diagnose and treat disease. Here, we describe the engineering and validation of a new cystine knot peptide (knottin) that selectively recognizes human integrin αvß6 with single-digit nanomolar affinity. We solve its 3D structure by NMR and x-ray crystallography and validate leads with 3 different radiolabels in pre-clinical models of cancer. We evaluate the lead tracer's safety, biodistribution and pharmacokinetics in healthy human volunteers, and show its ability to detect multiple cancers (pancreatic, cervical and lung) in patients at two study locations. Additionally, we demonstrate that the knottin PET tracers can also detect fibrotic lung disease in idiopathic pulmonary fibrosis patients. Our results indicate that these cystine knot PET tracers may have potential utility in multiple disease states that are associated with upregulation of integrin αvß6.

2.
Theranostics ; 9(25): 7924-7947, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31656546

RESUMO

Immunotherapy has proven to be an effective approach in a growing number of cancers. Despite durable clinical responses achieved with antibodies targeting immune checkpoint molecules, many patients do not respond. The common denominator for immunotherapies that have successfully been introduced in the clinic is their potential to induce or enhance infiltration of cytotoxic T-cells into the tumour. However, in clinical research the molecules, cells and processes involved in effective responses during immunotherapy remain largely obscure. Therefore, in vivo imaging technologies that interrogate T-cell responses in patients represent a powerful tool to boost further development of immunotherapy. This review comprises a comprehensive analysis of the in vivo imaging technologies that allow the characterisation of T-cell responses induced by anti-cancer immunotherapy, with emphasis on technologies that are clinically available or have high translational potential. Throughout we discuss their respective strengths and weaknesses, providing arguments for selecting the optimal imaging options for future research and patient management.

3.
J Nucl Med ; 2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519806

RESUMO

A considerable limitation of current small animal positron emission tomography/computed tomography (PET/CT) imaging is the low throughput of image acquisitions. Subsequently, to design sufficiently-powered studies, high costs accumulate. Together with Mediso Medical Imaging Systems, a four-bed mouse 'hotel' was developed to simultaneously image up to four mice, thereby reducing the cost and maximising radiotracer usage when compared to scans performed with a single mouse bed. Methods: For physiological evaluation of the four-bed mouse hotel, temperature and anaesthesia were tested for uniformity, followed by [18F]fluorodeoxyglucose (FDG) PET/CT imaging of 'mini' image quality (IQ) phantoms specifically designed to fit the new imaging system. Post-reconstruction, National Electrical Manufacturers Association (NEMA) NU-4 tests examined uniformity, recovery coefficients (RCs) and spill-over ratios (SORs). To evaluate the bed under standard in vivo imaging conditions, four mice were simultaneously scanned by dynamic [18F]FDG PET/CT over 60 minutes using the four-bed mouse hotel, with quantified images compared to those acquired using a single mouse bed. Results: The bed maintained a constant temperature of 36.8°C ± 0.4°C (n = 4), with anaesthesia distributed evenly to each nose cone (2.9 ± 0.1 L/min, n = 4). The NEMA tests performed on reconstructed mini IQ phantom images acquired using the four-bed mouse hotel revealed values within the tolerable limits for uniformity, RC values in >2mm rods, and SORs in the non-radioactive water- and air-filled chambers. There was low variability in radiotracer uptake in all major organs of mice scanned using the four-animal bed versus those imaged using a single bed imaging platform. Conclusion: Analysis of images acquired using the four-bed mouse hotel confirmed its utility to increase the throughput of small animal PET imaging without considerable loss of image quality and quantitative precision. In comparison to a single mouse bed, the cost and time associated with each scan were substantially reduced.

4.
Bioconjug Chem ; 30(5): 1331-1342, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30973715

RESUMO

Poly(ADP ribose) polymerase (PARP) enzymes generate poly(ADP ribose) post-translational modifications on target proteins for an array of functions centering on DNA and cell stress. PARP isoforms 1 and 2 are critically charged with the surveillance of DNA integrity and are the first line guardians of the genome against DNA breaks. Here we present a novel probe ([18F]-SuPAR) for noninvasive imaging of PARP-1/2 activity using positron emission tomography (PET). [18F]-SuPAR is a radiofluorinated nicotinamide adenine dinucleotide (NAD) analog that can be recognized by PARP-1/2 and incorporated into the long branched polymers of poly(ADP ribose) (PAR). The measurement of PARP-1/2 activity was supported by a reduction of radiotracer uptake in vivo following PARP-1/2 inhibition with talazoparib treatment, a potent PARP inhibitor recently approved by FDA for treatment of breast cancer, as well as ex vivo colocalization of radiotracer analog and poly(ADP ribose). With [18F]-SuPAR, we were able to map the dose- and time-dependent activation of PARP-1/2 following radiation therapy in breast and cervical cancer xenograft mouse models. Tumor response to therapy was determined by [18F]-SuPAR PET within 8 h of administration of a single dose of radiation equivalent to one round of stereotactic ablative radiotherapy.

5.
Methods Mol Biol ; 1928: 29-44, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30725448

RESUMO

Positron emission tomography (PET) enables the noninvasive spatiotemporal analysis of cancer metabolism in vivo. Both natural and nonnatural PET tracers have been developed to assess metabolic pathways during tumorigenesis, cancer progression, and metastasis. Here we describe the dynamic in vivo PET/CT imaging of the glucose analogue [18F]fluoro-2-deoxy-D-glucose (FDG), taking into consideration the methodology for alternative metabolic PET substrates.


Assuntos
Metabolismo Energético , Neoplasias/diagnóstico por imagem , Neoplasias/metabolismo , Tomografia por Emissão de Pósitrons , Animais , Biomarcadores , Radioisótopos de Carbono , Modelos Animais de Doenças , Fluordesoxiglucose F18 , Humanos , Processamento de Imagem Assistida por Computador , Imagem Tridimensional , Redes e Vias Metabólicas , Camundongos , Neoplasias/patologia , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos
6.
Clin Cancer Res ; 25(8): 2471-2482, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30651275

RESUMO

PURPOSE: Drug resistance is a major obstacle for the effective treatment of patients with high-grade serous ovarian cancer (HGSOC). Currently, there is no satisfactory way to identify patients with HGSOC that are refractive to the standard of care. Here, we propose the system xc - radiotracer (4S)-4-(3-[18F]fluoropropyl)-l-glutamate ([18F]FSPG) as a non-invasive method to measure upregulated antioxidant pathways present in drug-resistant HGSOC. EXPERIMENTAL DESIGN: Using matched chemotherapy sensitive and resistant ovarian cancer cell lines, we assessed their antioxidant capacity and its relation to [18F]FSPG uptake, both in cells and in animal models of human ovarian cancer. We identified the mechanisms driving differential [18F]FSPG cell accumulation and evaluated [18F]FSPG tumor uptake as predictive marker of treatment response in drug-resistant tumors. RESULTS: High intracellular glutathione (GSH) and low reactive oxygen species corresponded to decreased [18F]FSPG cell accumulation in drug-resistant versus drug-sensitive cells. Decreased [18F]FSPG uptake in drug-resistant cells was a consequence of changes in intracellular cystine, a key precursor in GSH biosynthesis. In vivo, [18F]FSPG uptake was decreased nearly 80% in chemotherapy-resistant A2780 tumors compared with parental drug-sensitive tumors, with nonresponding tumors displaying high levels of oxidized-to-reduced GSH. Treatment of drug-resistant A2780 tumors with doxorubicin resulted in no detectable change in tumor volume, GSH, or [18F]FSPG uptake. CONCLUSIONS: This study demonstrates the ability of [18F]FSPG to detect upregulated antioxidant pathways present in drug-resistant cancer. [18F]FSPG may therefore enable the identification of patients with HGSOC that are refractory to standard of care, allowing the transferal of drug-resistant patients to alternative therapies, thereby improving outcomes in this disease.

7.
Cancer Res ; 2018 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-30401715

RESUMO

The cell's endogenous antioxidant system is vital to maintenance of redox homeostasis. Despite its central role in normal and pathophysiology, no non-invasive tools exist to measure this system in patients. The cystine/glutamate antiporter system xc- maintains the balance between intracellular reactive oxygen species and antioxidant production through the provision of cystine, a key precursor in glutathione biosynthesis. Here we show that tumor cell retention of a system xc--specific positron emission tomography radiotracer, (S)-4-(3-[18F]fluoropropyl)-L-glutamic acid ([18F]FSPG), decreases in proportion to levels of oxidative stress following treatment with a range of redox-active compounds. The decrease in [18F]FSPG retention correlated with a depletion of intracellular cystine resulting from increased de novo glutathione biosynthesis, shown through [U-13C6, U-15N2]cystine isotopic tracing. In vivo, treatment with the chemotherapeutic doxorubicin decreased [18F]FSPG tumor uptake in a mouse model of ovarian cancer, coinciding with markers of oxidative stress but preceding tumor shrinkage and decreased glucose utilization. Having already been used in pilot clinical trials, [18F]FSPG PET could be rapidly translated to the clinic as an early redox indicator of tumor response to treatment.

8.
J Neuroinflammation ; 15(1): 55, 2018 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-29471880

RESUMO

BACKGROUND: The cystine/glutamate antiporter (xc-) has been implicated in several neurological disorders and, specifically, in multiple sclerosis (MS) as a mediator of glutamate excitotoxicity and proinflammatory immune responses. We aimed to evaluate an xc-specific positron emission tomography (PET) radiotracer, (4S)-4-(3-[18F]fluoropropyl)-L-glutamate ([18F]FSPG), for its ability to allow non-invasive monitoring of xc- activity in a mouse model of MS. METHODS: Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by subcutaneous injection of myelin oligodendrocyte glycoprotein (MOG35-55) peptide in complete Freund's adjuvant (CFA) followed by pertussis toxin. Control mice received CFA emulsion and pertussis toxin without MOG peptide, while a separate cohort of naïve mice received no treatment. PET studies were performed to investigate the kinetics and distribution of [18F]FSPG in naïve, control, pre-symptomatic, and symptomatic EAE mice, compared to 18F-fluorodeoxyglucose ([18F]FDG). After final PET scans, each mouse was perfused and radioactivity in dissected tissues was measured using a gamma counter. Central nervous system (CNS) tissues were further analyzed using ex vivo autoradiography or western blot. [18F]FSPG uptake in human monocytes, and T cells pre- and post-activation was investigated in vitro. RESULTS: [18F]FSPG was found to be more sensitive than [18F]FDG at detecting pathological changes in the spinal cord and brain of EAE mice. Even before clinical signs of disease, a small but significant increase in [18F]FSPG signal was observed in the spinal cord of EAE mice compared to controls. This increase in PET signal became more pronounced in symptomatic EAE mice and was confirmed by ex vivo biodistribution and autoradiography. Likewise, in the brain of symptomatic EAE mice, [18F]FSPG uptake was significantly higher than controls, with the largest changes observed in the cerebellum. Western blot analyses of CNS tissues revealed a significant correlation between light chain of xc- (xCT) protein levels, the subunit of xc- credited with its transporter activity, and [18F]FSPG-PET signal. In vitro [18F]FSPG uptake studies suggest that both activated monocytes and T cells contribute to the observed in vivo PET signal. CONCLUSION: These data highlight the promise of [18F]FSPG-PET as a technique to provide insights into neuroimmune interactions in MS and the in vivo role of xc- in the development and progression of this disease, thus warranting further investigation.

9.
Mol Imaging Biol ; 20(2): 194-199, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-28971330

RESUMO

PURPOSE: We recently reported that high thymidine phosphorylase (TP) expression is accompanied by low tumor thymidine concentration and high 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT) uptake in four untreated lung cancer xenografts. Here, we investigated whether this relationship also holds true for a broader range of tumor models. PROCEDURES: Lysates from n = 15 different tumor models originating from n = 6 institutions were tested for TP and thymidylate synthase (TS) expression using western blots. Results were correlated to [18F]FLT accumulation in the tumors as determined by positron emission tomography (PET) measurements in the different institutions and to previously published thymidine concentrations. RESULTS: Expression of TP correlated positively with [18F]FLT SUVmax (ρ = 0.549, P < 0.05). Furthermore, tumors with high TP levels possessed lower levels of thymidine (ρ = - 0.939, P < 0.001). CONCLUSIONS: In a broad range of tumors, [18F]FLT uptake as measured by PET is substantially influenced by TP expression and tumor thymidine concentrations. These data strengthen the role of TP as factor confounding [18F]FLT uptake.

10.
J Nucl Med ; 58(6): 881-887, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28209913

RESUMO

Cell death is an important target for imaging the early response of tumors to treatment. We describe here the validation of a phosphatidylserine-binding agent for detecting tumor cell death in vivo based on the C2A domain of synaptotagmin-I. Methods: The capability of near-infrared fluorophore-labeled and 99mTc- and 111In-labeled derivatives of C2Am for imaging tumor cell death, using planar near-infrared fluorescence imaging and SPECT, respectively, was evaluated in implanted and genetically engineered mouse models of lymphoma and in a human colorectal xenograft. Results: The fluorophore-labeled C2Am derivative showed predominantly renal clearance and high specificity and sensitivity for detecting low levels of tumor cell death (2%-5%). There was a significant correlation (R > 0.9, P < 0.05) between fluorescently labeled C2Am binding and histologic markers of cell death, including cleaved caspase-3, whereas there was no such correlation with a site-directed mutant of C2Am (iC2Am) that does not bind phosphatidylserine. 99mTc-C2Am and 111In-C2Am also showed favorable biodistribution profiles, with predominantly renal clearance and low nonspecific retention in the liver and spleen at 24 h after probe administration. 99mTc-C2Am and 111In-C2Am generated tumor-to-muscle ratios in drug-treated tumors of 4.3× and 2.2×, respectively, at 2 h and 7.3× and 4.1×, respectively, at 24 h after administration. Conclusion: Given the favorable biodistribution profile of 99mTc- and 111In-labeled C2Am, and their ability to produce rapid and cell death-specific image contrast, these agents have potential for clinical translation.


Assuntos
Apoptose , Imagem Molecular/métodos , Neoplasias Experimentais/metabolismo , Neoplasias Experimentais/patologia , Tomografia por Emissão de Pósitrons/métodos , Sinaptotagmina I/farmacocinética , Animais , Biomarcadores/metabolismo , Linhagem Celular Tumoral , Feminino , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Nus , Neoplasias Experimentais/diagnóstico por imagem , Domínios Proteicos , Compostos Radiofarmacêuticos/farmacocinética , Sinaptotagmina I/química , Distribuição Tecidual
11.
Sci Transl Med ; 9(373)2017 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-28100832

RESUMO

High-grade gliomas are aggressive cancers that often become rapidly fatal. Immunotherapy using CD8+ cytotoxic T lymphocytes (CTLs), engineered to express both herpes simplex virus type 1 thymidine kinase (HSV1-TK) and interleukin-13 (IL-13) zetakine chimeric antigen receptor (CAR), is a treatment strategy with considerable potential. To optimize this and related immunotherapies, it would be helpful to monitor CTL viability and trafficking to glioma cells. We show that noninvasive positron emission tomography (PET) imaging with 9-[4-[18F]fluoro-3-(hydroxymethyl)butyl]guanine ([18F]FHBG) can track HSV1-tk reporter gene expression present in CAR-engineered CTLs. [18F]FHBG imaging was safe and enabled the longitudinal imaging of T cells stably transfected with a PET reporter gene in patients. Further optimization of this imaging approach for monitoring in vivo cell trafficking should greatly benefit various cell-based therapies for cancer.


Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Genes Reporter , Glioma/diagnóstico por imagem , Imunoterapia/métodos , Receptores de Antígenos de Linfócitos T/metabolismo , Linfócitos T Citotóxicos/citologia , Idoso , Neoplasias Encefálicas/terapia , Feminino , Expressão Gênica , Terapia Genética/métodos , Glioma/terapia , Humanos , Interleucina-13/metabolismo , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia , Tomografia por Emissão de Pósitrons , Estudos Prospectivos , Timidina Quinase/metabolismo
12.
J Neurooncol ; 126(2): 253-64, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26650066

RESUMO

Glioblastoma multiforme (GBM) is an aggressive, malignant cancer Johnson and O'Neill (J Neurooncol 107: 359-364, 2012). An extract from the winter cherry plant (Withania somnifera ), AshwaMAX, is concentrated (4.3 %) for Withaferin A; a steroidal lactone that inhibits cancer cells Vanden Berghe et al. (Cancer Epidemiol Biomark Prev 23: 1985-1996, 2014). We hypothesized that AshwaMAX could treat GBM and that bioluminescence imaging (BLI) could track oral therapy in orthotopic murine models of glioblastoma. Human parietal-cortical glioblastoma cells (GBM2, GBM39) were isolated from primary tumors while U87-MG was obtained commercially. GBM2 was transduced with lentiviral vectors that express Green Fluorescent Protein (GFP)/firefly luciferase fusion proteins. Mutational, expression and proliferative status of GBMs were studied. Intracranial xenografts of glioblastomas were grown in the right frontal regions of female, nude mice (n = 3-5 per experiment). Tumor growth was followed through BLI. Neurosphere cultures (U87-MG, GBM2 and GBM39) were inhibited by AshwaMAX at IC50 of 1.4, 0.19 and 0.22 µM equivalent respectively and by Withaferin A with IC50 of 0.31, 0.28 and 0.25 µM respectively. Oral gavage, every other day, of AshwaMAX (40 mg/kg per day) significantly reduced bioluminescence signal (n = 3 mice, p < 0.02, four parameter non-linear regression analysis) in preclinical models. After 30 days of treatment, bioluminescent signal increased suggesting onset of resistance. BLI signal for control, vehicle-treated mice increased and then plateaued. Bioluminescent imaging revealed diffuse growth of GBM2 xenografts. With AshwaMAX, GBM neurospheres collapsed at nanomolar concentrations. Oral treatment studies on murine models confirmed that AshwaMAX is effective against orthotopic GBM. AshwaMAX is thus a promising candidate for future clinical translation in patients with GBM.


Assuntos
Antineoplásicos/administração & dosagem , Neoplasias Encefálicas/tratamento farmacológico , Glioblastoma/tratamento farmacológico , Extratos Vegetais/administração & dosagem , Withania/química , Vitanolídeos/administração & dosagem , Animais , Antineoplásicos/farmacologia , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Receptores ErbB/metabolismo , Feminino , Glioblastoma/metabolismo , Glioblastoma/patologia , Humanos , Medições Luminescentes , Camundongos , Camundongos Nus , Células-Tronco Neurais/efeitos dos fármacos , Extratos Vegetais/química , Vitanolídeos/farmacologia , Ensaios Antitumorais Modelo de Xenoenxerto
13.
Sci Transl Med ; 7(310): 310ra169, 2015 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-26491079

RESUMO

Cancer cells reprogram their metabolism to meet increased biosynthetic demands, commensurate with elevated rates of replication. Pyruvate kinase M2 (PKM2) catalyzes the final and rate-limiting step in tumor glycolysis, controlling the balance between energy production and the synthesis of metabolic precursors. We report here the synthesis and evaluation of a positron emission tomography (PET) radiotracer, [(11)C]DASA-23, that provides a direct noninvasive measure of PKM2 expression in preclinical models of glioblastoma multiforme (GBM). In vivo, orthotopic U87 and GBM39 patient-derived tumors were clearly delineated from the surrounding normal brain tissue by PET imaging, corresponding to exclusive tumor-associated PKM2 expression. In addition, systemic treatment of mice with the PKM2 activator TEPP-46 resulted in complete abrogation of the PET signal in intracranial GBM39 tumors. Together, these data provide the basis for the clinical evaluation of imaging agents that target this important gatekeeper of tumor glycolysis.


Assuntos
Hexoquinase/metabolismo , Tomografia por Emissão de Pósitrons , Piruvato Quinase/metabolismo , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/enzimologia , Radioisótopos de Carbono , Glicólise , Humanos
14.
Clin Cancer Res ; 21(17): 3896-905, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-25972517

RESUMO

PURPOSE: An early readout of tumor response to therapy through measurement of drug or radiation-induced cell death may provide important prognostic indications and improved patient management. It has been shown that the uptake of (18)F-C-SNAT can be used to detect early response to therapy in tumors by positron emission tomography (PET) via a mechanism of caspase-3-triggered nanoaggregation. EXPERIMENTAL DESIGN: Here, we compared the preclinical utility of (18)F-C-SNAT for the detection of drug-induced cell death to clinically evaluated radiotracers, (18)F-FDG, (99m)Tc-Annexin V, and (18)F-ML-10 in tumor cells in culture, and in tumor-bearing mice in vivo. RESULTS: In drug-treated lymphoma cells, (18)F-FDG, (99m)Tc-Annexin V, and (18)F-C-SNAT cell-associated radioactivity correlated well to levels of cell death (R(2) > 0.8; P < 0.001), with no correlation measured for (18)F-ML-10 (R(2) = 0.05; P > 0.05). A similar pattern of response was observed in two human NSCLC cell lines following carboplatin treatment. EL-4 tumor uptake of (99m)Tc-Annexin V and (18)F-C-SNAT were increased 1.4- and 2.1-fold, respectively, in drug-treated versus naïve control animals (P < 0.05), although (99m)Tc-Annexin V binding did not correlate to ex vivo TUNEL staining of tissue sections. A differential response was not observed with either (18)F-FDG or (18)F-ML-10. CONCLUSIONS: We have demonstrated here that (18)F-C-SNAT can sensitively detect drug-induced cell death in murine lymphoma and human NSCLC. Despite favorable image contrast obtained with (18)F-C-SNAT, the development of next-generation derivatives, using the same novel and promising uptake mechanism, but displaying improved biodistribution profiles, are warranted for maximum clinical utility.


Assuntos
Benzotiazóis , Neoplasias/diagnóstico , Oligopeptídeos , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos , Tomografia Computadorizada por Raios X , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/farmacologia , Benzotiazóis/metabolismo , Disponibilidade Biológica , Morte Celular , Linhagem Celular Tumoral , Modelos Animais de Doenças , Feminino , Humanos , Camundongos , Neoplasias/terapia , Oligopeptídeos/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos/metabolismo , Resultado do Tratamento , Carga Tumoral/efeitos dos fármacos
15.
J Nucl Med ; 55(9): 1506-12, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25012458

RESUMO

UNLABELLED: Deregulated cellular metabolism is a hallmark of many cancers. In addition to increased glycolytic flux, exploited for cancer imaging with (18)F-FDG, tumor cells display aberrant lipid metabolism. Pivalic acid is a short-chain, branched carboxylic acid used to increase oral bioavailability of prodrugs. After prodrug hydrolysis, pivalic acid undergoes intracellular metabolism via the fatty acid oxidation pathway. We have designed a new probe, 3-(18)F-fluoro-2,2-dimethylpropionic acid, also called (18)F-fluoro-pivalic acid ((18)F-FPIA), for the imaging of aberrant lipid metabolism and cancer detection. METHODS: Cell intrinsic uptake of (18)F-FPIA was measured in murine EMT6 breast adenocarcinoma cells. In vivo dynamic imaging, time course biodistribution, and radiotracer stability testing were performed. (18)F-FPIA tumor retention was further compared in vivo to (18)F-FDG uptake in several xenograft models and inflammatory tissue. RESULTS: (18)F-FPIA rapidly accumulated in EMT6 breast cancer cells, with retention of intracellular radioactivity predicted to occur via a putative (18)F-FPIA carnitine-ester. The radiotracer was metabolically stable to degradation in mice. In vivo imaging of implanted EMT6 murine and BT474 human breast adenocarcinoma cells by (18)F-FPIA PET showed rapid and extensive tumor localization, reaching 9.1% ± 0.5% and 7.6% ± 1.2% injected dose/g, respectively, at 60 min after injection. Substantial uptake in the cortex of the kidney was seen, with clearance primarily via urinary excretion. Regarding diagnostic utility, uptake of (18)F-FPIA was comparable to that of (18)F-FDG in EMT6 tumors but superior in the DU145 human prostate cancer model (54% higher uptake; P = 0.002). Furthermore, compared with (18)F-FDG, (18)F-FPIA had lower normal-brain uptake resulting in a superior tumor-to-brain ratio (2.5 vs. 1.3 in subcutaneously implanted U87 human glioma tumors; P = 0.001), predicting higher contrast for brain cancer imaging. Both radiotracers showed increased localization in inflammatory tissue. CONCLUSION: (18)F-FPIA shows promise as an imaging agent for cancer detection and warrants further investigation.


Assuntos
Radioisótopos de Flúor , Neoplasias Experimentais/diagnóstico por imagem , Ácidos Pentanoicos , Compostos Radiofarmacêuticos , Animais , Linhagem Celular Tumoral , Humanos , Camundongos , Tomografia por Emissão de Pósitrons
16.
PLoS One ; 9(3): e91694, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24618809

RESUMO

Tumour response to therapy is assessed primarily in the clinic by monitoring reductions in tumour size. However, this approach lacks sensitivity since in many cases several weeks may elapse before there is evidence of tumour shrinkage. There is therefore a need to develop non-invasive imaging techniques for monitoring tumour treatment response in the clinic. Here, we assessed the pre-clinical utility of (18)F-ICMT-11 positron emission tomography--a method for detecting caspase 3/7 activation--in non-small cell lung cancer (NSCLC). (18)F-ICMT-11 uptake was compared to molecular biochemical measures of cell death in PC9 and A549 NSCLC cells following treatment with carboplatin in vitro and in vivo. Carboplatin-induced apoptosis in the ERCC1 low/mutant EGFR PC9 cells was characterised by time and dose-related increased caspase-3/7 activation, poly-ADP-ribose polymerase cleavage and Annexin V staining. 18F-ICMT-11 uptake was consequently increased up to 14-fold at 200 µM carboplatin compared to vehicle treated cells (P<0.01). In contrast, necrosis was the predominant death mechanism in ERCC1 high/wt EGFR A549 cells and no change in (18)F-ICMT-11 uptake was detected. In vivo, histological analysis of PC9 tumour xenografts indicated high pre-therapy necrosis. A 4.6-fold increase in cleaved caspase-3/7 was measured in non-necrotic regions of PC9 tumours at 48 h post carboplatin therapy. Average PET-derived tumour (18)F-ICMT-11 uptake was insensitive to changes in apoptosis in the presence of substantial pre-existing necrosis. PET-based voxel intensity sorting however, identified intra-tumoural regions of high (18)F-ICMT-11 uptake, enabling accurate assessment of apoptosis and therefore therapy response. In A549 tumours that lacked high pre-therapy necrosis, carboplatin induced growth inhibition that was only minimally associated with apoptosis and thus not detectable by (18)F-ICMT-11 PET.


Assuntos
Antineoplásicos/farmacologia , Azidas , Carboplatina/farmacologia , Indóis , Neoplasias Pulmonares/diagnóstico , Tomografia por Emissão de Pósitrons , Animais , Antineoplásicos/administração & dosagem , Apoptose , Azidas/metabolismo , Carboplatina/administração & dosagem , Caspase 3/metabolismo , Caspase 7/metabolismo , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos , Ativação Enzimática , Feminino , Humanos , Indóis/metabolismo , Neoplasias Pulmonares/tratamento farmacológico , Ensaios Antitumorais Modelo de Xenoenxerto
17.
Cancer Res ; 74(5): 1319-28, 2014 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-24590807

RESUMO

The high rate of glucose uptake to fuel the bioenergetic and anabolic demands of proliferating cancer cells is well recognized and is exploited with (18)F-2-fluoro-2-deoxy-d-glucose positron emission tomography ((18)F-FDG-PET) to image tumors clinically. In contrast, enhanced glucose storage as glycogen (glycogenesis) in cancer is less well understood and the availability of a noninvasive method to image glycogen in vivo could provide important biologic insights. Here, we demonstrate that (18)F-N-(methyl-(2-fluoroethyl)-1H-[1,2,3]triazole-4-yl)glucosamine ((18)F-NFTG) annotates glycogenesis in cancer cells and tumors in vivo, measured by PET. Specificity of glycogen labeling was demonstrated by isolating (18)F-NFTG-associated glycogen and with stable knockdown of glycogen synthase 1, which inhibited (18)F-NFTG uptake, whereas oncogene (Rab25) activation-associated glycogen synthesis led to increased uptake. We further show that the rate of glycogenesis is cell-cycle regulated, enhanced during the nonproliferative state of cancer cells. We demonstrate that glycogen levels, (18)F-NFTG, but not (18)F-FDG uptake, increase proportionally with cell density and G1-G0 arrest, with potential application in the assessment of activation of oncogenic pathways related to glycogenesis and the detection of posttreatment tumor quiescence.


Assuntos
Glicogênio/metabolismo , Neoplasias/diagnóstico , Neoplasias/metabolismo , Pontos de Checagem do Ciclo Celular/fisiologia , Linhagem Celular Tumoral , Fluordesoxiglucose F18/metabolismo , Fase G1/fisiologia , Humanos , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos/metabolismo , Fase de Repouso do Ciclo Celular/fisiologia , Proteínas rab de Ligação ao GTP/genética
18.
Mol Imaging Biol ; 16(4): 558-66, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24310722

RESUMO

PURPOSE: The purpose of this paper is to study the association between RGD binding kinetics and αvß3 integrin receptor density in the complex tumor milieu. PROCEDURES: We assessed αvß3 in vitro and by (68)Ga-DOTA-[c(RGDfK)]2 positron emission tomography (PET) in tumors with varying αvß3. RESULTS: Intrinsic αvß3 expression decreased in the order of M21 >>> MDA-MB-231 > M21L in cells. Tumor volume of distribution by PET, V T, was significantly higher in M21 compared to isogenic M21L tumors (0.40 ± 0.01 versus 0.25 ± 0.02; p < 0.01) despite similar microvessel density (MVD) likely due to higher αvß3. V T for MDA-MB-231 (0.40 ± 0.04) was comparable to M21 despite lower αvß3 but in keeping with the higher MVD, suggesting superior tracer distribution. CONCLUSIONS: This study demonstrates that radioligand binding kinetics of PET data can be used to discriminate tumors with different αvß3 integrin expression-a key component of the angiogenesis phenotype-in vivo.


Assuntos
Vasos Sanguíneos/metabolismo , Vasos Sanguíneos/patologia , Integrina alfaVbeta3/metabolismo , Compostos Organometálicos , Peptídeos Cíclicos , Animais , Western Blotting , Linhagem Celular Tumoral , Feminino , Citometria de Fluxo , Humanos , Imuno-Histoquímica , Cinética , Camundongos Endogâmicos BALB C , Camundongos Nus , Neoplasias/irrigação sanguínea , Neoplasias/diagnóstico por imagem , Neoplasias/patologia , Molécula-1 de Adesão Celular Endotelial a Plaquetas/metabolismo , Tomografia por Emissão de Pósitrons , Traçadores Radioativos
19.
Proc Natl Acad Sci U S A ; 109(33): 13374-9, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22837393

RESUMO

Acute kidney injury (AKI) is a common and important medical problem, affecting 10% of hospitalized patients, and it is associated with significant morbidity and mortality. The most frequent cause of AKI is acute tubular necrosis (ATN). Current imaging techniques and biomarkers do not allow ATN to be reliably differentiated from important differential diagnoses, such as acute glomerulonephritis (GN). We investigated whether (13)C magnetic resonance spectroscopic imaging (MRSI) might allow the noninvasive diagnosis of ATN. (13)C MRSI of hyperpolarized [1,4-(13)C(2)]fumarate and pyruvate was used in murine models of ATN and acute GN (NZM2410 mice with lupus nephritis). A significant increase in [1,4-(13)C(2)]malate signal was identified in the kidneys of mice with ATN early in the disease course before the onset of severe histological changes. No such increase in renal [1,4-(13)C(2)]malate was observed in mice with acute GN. The kidney [1-(13)C]pyruvate/[1-(13)C]lactate ratio showed substantial variability and was not significantly decreased in animals with ATN or increased in animals with GN. In conclusion, MRSI of hyperpolarized [1,4-(13)C(2)]fumarate allows the detection of early tubular necrosis and its distinction from glomerular inflammation in murine models. This technique may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with ATN, reducing the need for acute dialysis with its attendant morbidity and cost.


Assuntos
Fumaratos , Necrose Tubular Aguda/diagnóstico , Imagem por Ressonância Magnética/métodos , Animais , Isótopos de Carbono , Diagnóstico Precoce , Ácido Fólico , Humanos , Rim/anormalidades , Rim/patologia , Rim/fisiopatologia , Necrose Tubular Aguda/induzido quimicamente , Necrose Tubular Aguda/fisiopatologia , Cinética , Nefrite Lúpica/diagnóstico , Nefrite Lúpica/patologia , Malatos , Camundongos , Camundongos Endogâmicos C57BL , Ácido Pirúvico
20.
Clin Cancer Res ; 18(4): 1063-72, 2012 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-22235095

RESUMO

PURPOSE: (11)C-Choline-positron emission tomography (PET) has been exploited to detect the aberrant choline metabolism in tumors. Radiolabeled choline uptake within the imaging time is primarily a function of transport, phosphorylation, and oxidation. Rapid choline oxidation, however, complicates interpretation of PET data. In this study, we investigated the biologic basis of the oxidation of deuterated choline analogs and assessed their specificity in human tumor xenografts. EXPERIMENTAL DESIGN: (11)C-Choline, (11)C-methyl-[1,2-(2)H(4)]-choline ((11)C-D4-choline), and (18)F-D4-choline were synthesized to permit comparison. Biodistribution, metabolism, small-animal PET studies, and kinetic analysis of tracer uptake were carried out in human colon HCT116 xenograft-bearing mice. RESULTS: Oxidation of choline analogs to betaine was highest with (11)C-choline, with reduced oxidation observed with (11)C-D4-choline and substantially reduced with (18)F-D4-choline, suggesting that both fluorination and deuteration were important for tracer metabolism. Although all tracers were converted intracellularly to labeled phosphocholine (specific signal), the higher rate constants for intracellular retention (K(i) and k(3)) of (11)C-choline and (11)C-D4-choline, compared with (18)F-D4-choline, were explained by the rapid conversion of the nonfluorinated tracers to betaine within HCT116 tumors. Imaging studies showed that the uptake of (18)F-D4-choline in three tumors with similar radiotracer delivery (K(1)) and choline kinase α expression-HCT116, A375, and PC3-M-were the same, suggesting that (18)F-D4-choline has utility for cancer detection irrespective of histologic type. CONCLUSION: We have shown here that both deuteration and fluorination combine to provide protection against choline oxidation in vivo. (18)F-D4-choline showed the highest selectivity for phosphorylation and warrants clinical evaluation.


Assuntos
Radioisótopos de Carbono , Colina , Deutério , Fluordesoxiglucose F18 , Neoplasias/diagnóstico por imagem , Tomografia por Emissão de Pósitrons , Animais , Linhagem Celular Tumoral , Colina/análogos & derivados , Colina/metabolismo , Modelos Animais de Doenças , Humanos , Rim/metabolismo , Cinética , Masculino , Melanoma/diagnóstico por imagem , Melanoma/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Neoplasias/metabolismo , Oxirredução , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/metabolismo , Traçadores Radioativos
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