Background: Resistance to modern adjuvant treatment is in part due to the failure of programmed cell death. Therefore the molecules that execute the apoptotic program are potential targets for the development of anti-cancer therapeutics. The sigma-2 receptor has been found to be over-expressed in some types of malignant tumors, and, recently, small molecule ligands to the sigma-2 receptor were found to induce cancer cell apoptosis.

Recently, a novel method for detection of DNA synthesis has been developed based on the incorporation of 5-ethynyl-2′-deoxyuridine (EdU), a thymidine analogue, into cellular DNA and the subsequent reaction of EdU with a fluorescent azide in a copper-catalyzed [3+2] cycloaddition ("Click" reaction). In the present study, we evaluated this method for studying cell proliferation in the adult central nervous system in comparison with the "gold standard" method of 5-bromo-2′-deoxyuridine (BrdU) staining using two behavioral paradigms, voluntary exercise and restraint stress. Our data demonstrate that the number of EdU positive cells in the dentate gyrus of the hippocampus (DG) slightly increased in an EdU dose-dependent manner in both the control and voluntary exercise (running) mouse groups. The number of EdU-labeled cells was comparable to the number of BrdUlabeled cells in both the control and running mice. Furthermore, EdU and BrdU co-localized to the same cells within the DG. Voluntary exercise significantly increased the number of EdU and BrdU positive cells in the DG. In contrast, restraint stress significantly decreased the number of EdU positive cells. The EdU positive cells differentiated into mature neurons. EdU staining is compatible with immunohistochemical staining of other antigens. Moreover, our data demonstrated EdU staining can be combined with BrdU staining, providing a valuable tool of double labeling DNA synthesis, e.g., for tracking the two populations of neurons generated at different time points. In conclusion, Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A series of fluorine-containing benzamide analogs was synthesized and evaluated as candidate ligands for positron emission tomography (PET) imaging of the sigma-2 (sigma2) receptor status of solid tumors. Four compounds having a moderate to high affinity for sigma2 receptors and a moderate to low affinity for sigma-1 (sigma1) receptors were radiolabeled with fluorine-18 via displacement of the corresponding mesylate precursor with [18F]fluoride. Biodistribution studies in female Balb/c mice bearing EMT-6 tumor allografts demonstrated that all four F-18-labeled compounds had a high tumor uptake (2.5-3.7% ID/g) and acceptable tumor/normal tissue ratios at 1 and 2 h post-i.v. injection. An analysis of the chemistry and biodistribution data suggested that N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2-[18F]-fluoroethoxy)-5-methylbenzamide ([18F]3c) and N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2-[18F]-fluoroethoxy)-5-iodo-3-methoxybenzamide ([18F]3f) are acceptable compounds for imaging the sigma2 receptor status of solid tumors.

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A new class of vesicular acetylcholine transporter inhibitor that incorporates a carbonyl group into the benzovesamicol structure was synthesized and analogs were evaluated in vitro.

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We synthesized and characterized two novel fluorescent sigma-2 receptor selective ligands, SW120 and SW116, and evaluated these ligands as potential probes for imaging cell proliferation. Both ligands are highly selective for sigma-2 receptors versus sigma-1 receptors. SW120 and SW116 were internalized into MDA-MB-435 cells, and 50% of the maximum fluorescent intensity was reached in 11 and 24 minutes, respectively. In vitro studies showed that 50% of SW120 or SW116 washed out of cells in 1 hour. The internalization of SW120 was reduced ≈30% by phenylarsine oxide, an inhibitor of endocytosis, suggesting that sigma-2 ligands are internalized, in part, by an endocytotic pathway. Subcellular localization studies using confocal and two-photon microscopy showed that SW120 and SW116 partially colocalized with fluorescent markers of mitochondria, endoplasmic reticulum, lysosomes, and the plasma membrane, suggesting that sigma-2 receptors localized to the cytoplasmic organelles and plasma membrane. SW120 did not colocalize with the nuclear dye 4′,6-diamidino-2-phenylindole. In vivo studies showed that the uptake of SW120 in solid tumors and peripheral blood mononuclear cells of mice positively correlated with the expression level of the cell proliferation marker Ki-67, suggesting that sigma-2 fluorescent probes may be used to image cell proliferation in mice.