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Herein, we report the development of an 18 F-labeled, activity-based small-molecule probe targeting the cancer-associated serine hydrolase NCEH1. We undertook a focused medicinal chemistry campaign to simultaneously preserve potent and specific NCEH1 labeling in live cells and animals, while permitting facile 18 F radionuclide incorporation required for PET imaging. The resulting molecule, [18 F]JW199, labels active NCEH1 in live cells at nanomolar concentrations and greater than 1000-fold selectivity relative to other serine hydrolases. [18 F]JW199 displays rapid, NCEH1-dependent accumulation in mouse tissues. Finally, we demonstrate that [18 F]JW199 labels aggressive cancer tumor cells in vivo, which uncovered localized NCEH1 activity at the leading edge of triple-negative breast cancer tumors, suggesting roles for NCEH1 in tumor aggressiveness and metastasis.

The measurement of extracellular pH (pHe) has significant clinical value for pathological diagnoses and for monitoring the effects of pH-altering therapies. One of the major problems of measuring pHe with a relaxation-based MRI contrast agent is that the longitudinal relaxivity depends on both pH and the concentration of the agent, requiring the use of a second pH-unresponsive agent to measure the concentration. Here we tested the feasibility of measuring pH with a relaxation-based dendritic MRI contrast agent in a concentration-independent manner at clinically relevant field strengths. The transverse and longitudinal relaxation times in solutions of the contrast agent (GdDOTA-4AmP)44-G5, a G5–PAMAM dendrimer-based MRI contrast agent in water, were measured at 3 T and 7 T magnetic field strengths as a function of pH. At 3 T, longitudinal relaxivity (r1) increased from 7.91 to 9.65 mM−1 s−1 (on a per Gd3+ basis) on changing pH from 8.84 to 6.35. At 7 T, r1 relaxivity showed pH response, albeit at lower mean values; transverse relaxivity (r2) remained independent of pH and magnetic field strengths. The longitudinal relaxivity of (GdDOTA-4AmP)44-G5 exhibited a strong and reversible pH dependence. The ratio of relaxation rates R2/R1 also showed a linear relationship in a pH-responsive manner, and this pH response was independent of the absolute concentration of (GdDOTA-4AmP)44-G5 agent. Importantly, the nanoprobe (GdDOTA-4AmP)44-G5 shows pH response in the range commonly found in the microenvironment of solid tumors. Copyright © 2015 John Wiley & Sons, Ltd.

Aim: The authors have investigated the usefulness of in vivo chemical exchange saturation transfer MRI for detecting gliomas using a dual-modality imaging contrast agent. Materials & methods: A paramagnetic chemical exchange saturation transfer MRI contrast agent, Eu-1,4,7,10-tetraazacclododecane-1,4,7,10-tetraacetic acid-Gly4 and a fluorescent agent, DyLight® 680, were conjugated to a generation 5 polyamidoamine dendrimer to create the dual-modality, nano-sized imaging contrast agent. Results: The agent was detected with in vivo chemical exchange saturation transfer MRI in an U87 glioma model. These results were validated using in vivo and ex vivo fluorescence imaging. Conclusion: This study demonstrated the merits of using a nano-sized imaging contrast agent for detecting gliomas and using a dual-modality agent for detecting gliomas at different spatial scales. Original submitted 9 January 2012; Revised submitted 18 April 2012; Published online 14 August 2012

Background Due to their unique property to migrate to pathological lesions, stem cells are used as a delivery vehicle for therapeutic genes to tumors, especially for glioma. It is critically important to track the movement, localization, engraftment efficiency and functional capability or expression of transgenes of selected cell populations following transplantation. The purposes of this study were to investigate whether 1) intravenously administered, genetically transformed cord blood derived EPCs can carry human sodium iodide symporter (hNIS) to the sites of tumors in rat orthotopic model of human glioma and express transgene products, and 2) whether accumulation of these administered EPCs can be tracked by different in vivo imaging modalities. Methods and Results Collected EPCs were cultured and transduced to carry hNIS. Cellular viability, differential capacity and Tc-99m uptake were determined. Five to ten million EPCs were intravenously administered and Tc-99-SPECT images were acquired on day 8, to determine the accumulation of EPCs and expression of transgenes (increase activity of Tc-99m) in the tumors. Immunohistochemistry was performed to determine endothelial cell markers and hNIS positive cells in the tumors. Transduced EPCs were also magnetically labeled and accumulation of cells was confirmed by MRI and histochemistry. SPECT analysis showed increased activity of Tc-99m in the tumors that received transduced EPCs, indicative of the expression of transgene (hNIS). Activity of Tc-99m in the tumors was also dependent on the number of administered transduced EPCs. MRI showed the accumulation of magnetically labeled EPCs. Immunohistochemical analysis showed iron and hNIS positive and, human CD31 and vWF positive cells in the tumors. Conclusion EPC was able to carry and express hNIS in glioma following IV administration. SPECT detected migration of EPCs and expression of the hNIS gene. EPCs can be used as gene carrier/delivery system for glioma therapy as well as imaging probes.

The naturally occurring cyclic tetrapeptide, chlamydocin, originally isolated from fungus Diheterospora chlamydosphoria, consists of α-aminoisobutyric acid, l-phenylalanine, d-proline and an unusual amino acid (S)-2-amino-8-((S)-oxiran-2-yl)-8-oxooctanoic acid (Aoe) and inhibits the histone deacetylases (HDACs), a class of regulatory enzymes. The epoxyketone moiety of Aoe is the key functional group for inhibition. The cyclic tetrapeptide scaffold is supposed to play important role for effective binding to the surface of enzymes. In place of the epoxyketone group, hydroxamic acid and sulfhydryl group have been applied to design inhibitor ligands to zinc atom in catalytic site of HDACs. In the research for more potent HDAC inhibitors, we replaced the epoxyketone moiety of Aoe with different functional groups and synthesized a series of chlamydocin analogs as HDAC inhibitors. Among the functional groups, methoxymethylketone moiety showed as potent inhibition as the hydroxamic acid. On the contrary, we confirmed that borate, trifruoromethylketone, and 2-aminoanilide are almost inactive in HDAC inhibition.

A series of chlamydocin analogs with various carbonyl functionalities were designed and synthesized as histone deacetylase (HDAC) inhibitors. Chlamydocin is a cyclic tetrapeptide containing an epoxyketone surrogate in the side chain which makes it irreversible inhibitor of HDACs, whereas apicidins are a class of cyclic tetrapeptides that contain an ethylketone moiety as zinc ligand. We replaced the epoxyketone moiety of chlamydocin with several ketones and aldehyde to synthesize potent reversible and selective HDAC inhibitors. The inhibitory activity of the cyclic tetrapeptides against histone deacetylase enzymes were evaluated and the result showed most of them are potent inhibitors. Some of them have remarkable selectivity among the HDACs.