PET imaging of tumor glycolysis downstream of hexokinase through noninvasive measurement of pyruvate kinase M2

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.

Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes

As an emerging class of optical nanomaterials, semiconducting polymer nanoparticles (SPNs) are highly photostable, optically active and versatile in chemistry; these properties make them attractive as molecular imaging agents to enable imaging of biological events and functionalities at multiple scales. More recently, a variety of SPNs have been found to exhibit high photoacoustic properties, and further empowered photoacoustic imaging for contrast enhanced in vivo molecular imaging. Target-sensitive components can be incorporated in the SPNs to create activatable imaging probes to sense and monitor the target dynamics in living objects. Intrinsically biophotonic and biocompatible, SPNs can be further engineered for multimodal imaging and for real-time imaging of drug delivery. WIREs Nanomed Nanobiotechnol 2017, 9:e1418. doi: 10.1002/wnan.1418 For further resources related to this article, please visit the WIREs website.

Molecular Magnetic Resonance Imaging of Tumor Response to Therapy

Personalized cancer medicine requires measurement of therapeutic efficacy as early as possible, which is optimally achieved by three-dimensional imaging given the heterogeneity of cancer. Magnetic resonance imaging (MRI) can obtain images of both anatomy and cellular responses, if acquired with a molecular imaging contrast agent. The poor sensitivity of MRI has limited the development of activatable molecular MR contrast agents. To overcome this limitation of molecular MRI, a novel implementation of our caspase-3-sensitive nanoaggregation MRI (C-SNAM) contrast agent is reported. C-SNAM is triggered to self-assemble into nanoparticles in apoptotic tumor cells, and effectively amplifies molecular level changes through nanoaggregation, enhancing tissue retention and spin-lattice relaxivity. At one-tenth the current clinical dose of contrast agent, and following a single imaging session, C-SNAM MRI accurately measured the response of tumors to either metronomic chemotherapy or radiation therapy, where the degree of signal enhancement is prognostic of long-term therapeutic efficacy. Importantly, C-SNAM is inert to immune activation, permitting radiation therapy monitoring.

Diketopyrrolopyrrole-Based Semiconducting Polymer Nanoparticles for In Vivo Photoacoustic Imaging

Diketopyrrolopyrrole-based semiconducting polymer nanoparticles with high photostability and strong photoacoustic brightness are designed and synthesized, which results in 5.3-fold photoacoustic signal enhancement in tumor xenografts after systemic administration.

Semiconducting Polymer Nanoparticles with Persistent Near-Infrared Luminescence for In Vivo Optical Imaging

Materials with persistent luminescence are attractive for in vivo optical imaging since they have a long lifetime that allows the separation of excitation of fluorophores and image acquisition for time-delay imaging, thus eliminating tissue autofluorescence associated with fluorescence imaging. Persistently luminescent nanoparticles have previously been fabricated from toxic rare-earth metals. This work reports that nanoparticles made of the conjugated polymer MEH-PPV can generate luminescence persisting for an hour upon single excitation. A near-infrared dye was encapsulated in the conjugated polymer nanoparticle to successfully generate persistent near-infrared luminescence through resonance energy transfer. This new persistent luminescence nanoparticles have been demonstrated for optical imaging applications in living mice.

Quantitative detection of cells expressing BlaC using droplet-based microfluidics for use in the diagnosis of tuberculosis

This paper describes a method for the quantitative detection of cells expressing BlaC, a β-lactamase naturally expressed by Mycobacterium tuberculosis, intended for the diagnosis of tuberculosis. The method is based on the compartmentalization of bacteria in picoliter droplets at limiting dilutions such that each drop contains one or no cells. The co-encapsulation of a fluorogenic substrate probe for BlaC allows the quantification of bacteria by enumerating the number of fluorescent drops. Quantification of 10 colony forming units per milliliter is demonstrated. Furthermore, the encapsulation of single cell in drops maintains the specificity of the detection scheme even when the concentration of bacteria that do not express BlaC exceeds that expressing BlaC by one million-fold.

Antioxidant activities of orange peel extract in ghee (butter oil) stored at different storage temperatures

Antioxidant activities of butylatedhydroxyanisole (BHA) and orange peel powder extract in ghee stored at different storage temperatures (T1:6 ± 2 °C; T2: 32 ± 2 °C; T3:60 ± 2 °C) were evaluated during storage period of 21 days. Peroxide value (PV), thiobarbituric acid (TBA), radical scavenging activity (RSA) and free fatty acids (FFA) of ghee samples were analyzed during the study. PV, TBA and FFA of ghee samples increased significantly while radical scavenging activity (RSA) of ghee samples decreased significantly at accelerated temperature (T3) as compared to the temperatures at T1 and T2. Effect of storage temperature on development of peroxides and TBA of ghee samples was significantly higher than the effect of treatment and storage period while treatment had more significant effect on the change in FFA and RSA as compared to storage temperature and storage period. Ghee incorporated with orange peel extract (OPE) showed stronger activity in quenching DPPH radicals and least development of PV, TBA and FFA than ghee incorporated with BHA and control. The study revealed that orange peel could be a good natural source of antioxidants which can be used in fat rich food products like ghee to retard oxidative deterioration.

Preclinical Kinetic Analysis of the Caspase-3/7 PET Tracer 18F-C-SNAT: Quantifying the Changes in Blood Flow and Tumor Retention After Chemotherapy

Early detection of tumor response to therapy is crucial to the timely identification of the most efficacious treatments. We recently developed a novel apoptosis imaging tracer, (18)F-C-SNAT (C-SNAT is caspase-sensitive nanoaggregation tracer), that undergoes an intramolecular cyclization reaction after cleavage by caspase-3/7, a biomarker of apoptosis. This caspase-3/7-dependent reaction leads to an enhanced accumulation and retention of (18)F activity in apoptotic tumors. This study aimed to fully examine in vivo pharmacokinetics of the tracer through PET imaging and kinetic modeling in a preclinical mouse model of tumor response to systemic anticancer chemotherapy.

METHODS

Tumor-bearing nude mice were treated 3 times with intravenous injections of doxorubicin before undergoing a 120-min dynamic (18)F-C-SNAT PET/CT scan. Time-activity curves were extracted from the tumor and selected organs. A 2-tissue-compartment model was fitted to the time-activity curves from tumor and muscle, using the left ventricle of the heart as input function, and the pharmacokinetic rate constants were calculated.

RESULTS

Both tumor uptake (percentage injected dose per gram) and the tumor-to-muscle activity ratio were significantly higher in the treated mice than untreated mice. Pharmacokinetic rate constants calculated by the 2-tissue-compartment model showed a significant increase in delivery and accumulation of the tracer after the systemic chemotherapeutic treatment. Delivery of (18)F-C-SNAT to the tumor tissue, quantified as K1, increased from 0.31 g⋅(mL⋅min)(-1) in untreated mice to 1.03 g⋅(mL⋅min)(-1) in treated mice, a measurement closely related to changes in blood flow. Accumulation of (18)F-C-SNAT, quantified as k3, increased from 0.03 to 0.12 min(-1), proving a higher retention of (18)F-C-SNAT in treated tumors independent from changes in blood flow. An increase in delivery was also found in the muscular tissue of treated mice without increasing accumulation.

CONCLUSION

(18)F-C-SNAT has significantly increased tumor uptake and significantly increased tumor-to-muscle ratio in a preclinical mouse model of tumor therapy. Furthermore, our kinetic modeling of (18)F-C-SNAT shows that chemotherapeutic treatment increased accumulation (k3) in the treated tumors, independent of increased delivery (K1).

A Systematic Comparison of 18F-C-SNAT to Established Radiotracer Imaging Agents for the Detection of Tumor Response to Treatment

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.

[Differential gene expression in incompatible interaction between Lilium regale Wilson and Fusarium oxysporum f. sp. lilii revealed by combined SSH and microarray analysis]

Fusarium wilt, caused by a soilborne pathogen Fusarium oxysporum f. sp. lilii, is the major disease of lily (Lilium L.). In order to isolate the genes differentially expressed in a resistant reaction to F. oxysporum in L. regale Wilson, a cDNA library was constructed with L. regale root during F. oxysporum infection using the suppression subtractive hybridization (SSH), and a total of 585 unique expressed sequence tags (ESTs) were obtained. Furthermore, the gene expression profiles in the incompatible interaction between L. regale and F. oxysporum were revealed by oligonucleotide microarray analysis of 585 unique ESTs comparison to the compatible interaction between a susceptible Lilium Oriental Hybrid 'Siberia' and F. oxysporum. The result of expression profile analysis indicated that the genes encoding pathogenesis-related proteins (PRs), antioxidative stress enzymes, secondary metabolism enzymes, transcription factors, signal transduction proteins as well as a large number of unknown genes were involved in early defense response of L. regale to F. oxysporum infection. Moreover, the following quantitative reverse transcription PCR (QRT-PCR) analysis confirmed reliability of the oligonucleotide microarray data. In the present study, isolation of differentially expressed genes in L. regale during response to F. oxysporum helped to uncover the molecular mechanism associated with the resistance of L. regale against F. oxysporum.

Magnetic resonance imaging of stem cell apoptosis in arthritic joints with a caspase activatable contrast agent

About 43 million individuals in the U.S. encounter cartilage injuries due to trauma or osteoarthritis, leading to joint pain and functional disability. Matrix-associated stem cell implants (MASI) represent a promising approach for repair of cartilage defects. However, limited survival of MASI creates a significant bottleneck for successful cartilage regeneration outcomes and functional reconstitution. We report an approach for noninvasive detection of stem cell apoptosis with magnetic resonance imaging (MRI), based on a caspase-3-sensitive nanoaggregation MRI probe (C-SNAM). C-SNAM self-assembles into nanoparticles after hydrolysis by caspase-3, leading to 90% amplification of (1)H MR signal and prolonged in vivo retention. Following intra-articular injection, C-SNAM causes significant MR signal enhancement in apoptotic MASI compared to viable MASI. Our results indicate that C-SNAM functions as an imaging probe for stem cell apoptosis in MASI. This concept could be applied to a broad range of cell transplants and target sites.

ATF3-mediated NRF2/HO-1 signaling regulates TLR4 innate immune responses in mouse liver ischemia/reperfusion injury

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor that has been shown to repress inflammatory gene expression in multiple cell types and diseases. However, little is known about the roles and mechanisms of ATF3 in liver ischemia/reperfusion injury (IRI). In warm and cold liver IRI models, we showed that ATF3 deficiency significantly increased ischemia/reperfusion (IR)-stressed liver injury, as evidenced by increased serum alanine aminotransferase levels, histological liver damage, and hepatocellular apoptosis. These may correlate with inhibition of the intrahepatic nuclear factor erythroid-derived 2-related factor 2/heme oxygenase-1 (NRF2/HO-1) signaling pathway leading to enhancing Toll-like receptor 4/nuclear factor kappa beta (TLR4/NF-κB) activation, pro-inflammatory programs and macrophage/neutrophil trafficking, while simultaneously repressing anti-apoptotic molecules in ischemic liver. Interestingly, activation of NRF2/HO-1 signaling using an NRF2 activator, oltipraz (M2), during hepatic IRI-rescued ATF3 anti-inflammatory functions in ATF3-deficient mice. For in vitro studies, ATF3 ablation in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMMs) depressed levels of NRF2/HO-1 and PI3K/AKT, resulting in enhanced TLR4/NF-κB activation. Pretreatment of LPS-stimulated BMMs with M2 increased NRF2/HO-1 expression, promoted PI3K/AKT, which in turn suppressed TLR4/NF-κB-mediated proinflammatory mediators. Thus, our results first demonstrate ATF3-mediated NRF2/HO-1 signaling in the regulation of TLR4-driven inflammatory responses in IR-stressed livers. Our findings provide a rationale for a novel therapeutic strategy for managing IR-induced liver injury.