The sigma-2 receptors are promising therapeutic targets because of their significant upregulation in tumor cells compared with normal tissue. Here, we characterize CM572 [3-(4-(4-(4-14.6 6 6.9 nM), a novel isothiocyanate derivative of the putative sigma-2 antagonist, SN79 [6-acetyl-3-(4-(4-(4-CM572 bound irreversibly to sigma-2 receptors by virtue of the isothiocyanate moiety but not to sigma-1. Studies in human SK-N-SH neuroblastoma cells revealed that CM572 induced an immediate dose-dependent increase in cytosolic calcium concentration. A 24-hour treatment of SK-N-SH cells with CM572 induced dose-dependent cell death, with an EC 50 5 7.6 6 1.7 mM. This effect was sustained over 24 hours even after a 60-minute pretreatment with CM572, followed by extensive washing to remove ligand, indicating an irreversible effect consistent with the irreversible binding data. Western blot analysis revealed that CM572 also induced cleavage activation of proapoptotic BH3-interacting domain death agonist. These data suggest irreversible agonist-like activity. Low concentrations of CM572 that were minimally effective were able to attenuate significantly the calcium signal and cell death induced by the sigma-2 agonist CB-64D [(1)-1R,5R-(E)-8-benzylidene-5-(3-hydroxyphenyl)-2-methylmorphan-7-one]. CM572 was also cytotoxic against PANC-1 pancreatic and MCF-7 breast cancer cell lines. The cytotoxic activity of CM572 was selective for cancer cells over normal cells, being much less potent against primary human melanocytes and human mammary epithelial cells. Taken together, these data show that CM572 is a selective, irreversible sigma-2 receptor partial agonist. This novel irreversible ligand may further our understanding of the endogenous role of this receptor, in addition to having potential use in targeted cancer diagnosis and therapy.
Protein tyrosine phosphatases such as PTP1B and YopH are potential targets for the development of therapeutic agents against a variety of pathological conditions including diabetes, obesity, and infection by the bacterium Yersinia pestis. A focused library of bidentate α-ketoacid-based inhibitors has been screened against several tyrosine phosphatases. Compound 2a has IC(50) values of 43 and 220 nM against YopH and PTP1B, respectively, and shows a 30-fold selectivity for PTP1B over the closely related phosphatase TCPTP.
Sigma-2 receptors, recently identified as TMEM97, have been implicated in cancer and neurodegenerative disease. Structurally distinct sigma-2 receptor ligands induce cell death in tumor cells, linking sigma-2 receptors to apoptotic pathways. Recently, we reported that sigma-2 receptors can also stimulate glycolytic hallmarks, effects consistent with a prosurvival function and upregulation in cancer cells. Both apoptotic and metabolically stimulative effects were observed with compounds related to the canonical sigma-2 antagonist SN79. Here we investigate a series of 6-substituted SN79 analogs to assess the structural determinants governing these divergent effects. Substitutions on the benzoxazolone ring of the core SN79 structure resulted in high-affinity sigma-2 receptor ligands (K i 5 0.56-17.9 nM), with replacement of the heterocyclic oxygen by N-methyl (producing N-methylbenzimidazolones) generally decreasing sigma-1 affinity and a sulfur substitution (producing benzothiazolones) imparting high affinity at both subtypes, lowering subtype selectivity. Substitution at the 6-position with COCH 3 , NO 2 , NH 2 , or F resulted in ligands that were not cytotoxic. Five of these ligands induced an increase in metabolic activity, as measured by increased reduction of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) in human SK-N-SH neuroblastoma cells, further supporting a role for sigma-2 receptors in metabolism. Substitution with 6-isothiocyanate resulted in ligands that were sigma-2 selective and that irreversibly bound to the sigma-2 receptor, but not to the sigma-1 receptor. These ligands induced cell death upon both acute and continuous treatment (EC 50 5 7.6-32.8 mM), suggesting that irreversible receptor binding plays a role in cytotoxicity. These ligands will be useful for further study of these divergent roles of sigma-2 receptors. Part of this work was presented as follows: Nicholson HE, Alsharif W, McCurdy CR, and Bowen WD (2015) Evaluation of structural changes in SN79derived sigma-2 receptor modulators: effect on apoptotic efficacy in SK-N-SH neuroblastoma.
High overexpression of sigma (σ) receptors (σ1 and σ2 subtypes) in a variety of human solid tumors has prompted the development of σ receptor-targeting radioligands, as imaging agents for tumor detection. A majority of these radioligands to date target the σ2 receptor, a potential marker of tumor proliferative status. The identification of approximately equal proportions of both σ receptor subtypes in prostate tumors suggests that a high affinity, dual σ receptor-targeting radioligand could potentially provide enhanced tumor targeting efficacy in prostate cancer. To accomplish this goal, we designed a series of ligands which bind to both σ receptor subtypes with high affinity. Ligand 3a in this series, displaying optimal dual σ receptor subtype affinity (σ1, 6.3 nM; σ2, 10.2 nM) was radiolabeled with fluorine-18 (18F) to give [18F]3a and evaluated as a σ receptor-targeting radioligand in the mouse PC-3 prostate tumor model. Cellular assays with PC-3 cells demonstrated that a major proportion of [18F]3a was localized to cell surface σ receptors, while ∼10% of [18F]3a was internalized within cells after incubation for 3.5 h. Serial PET imaging in mice bearing PC-3 tumors revealed that uptake of [18F]3a was 1.6 ± 0.8, 4.4 ± 0.3, and 3.6 ± 0.6% ID/g (% injection dose per gram) in σ receptor-positive prostate tumors at 15 min, 1.5 h, and 3.5 h postinjection, respectively (n = 3) resulting in clear tumor visualization. Blocking studies conducted with haloperidol (a nonselective inhibitor for both σ receptor subtypes) confirmed that the uptake of [18F]3a was σ receptor-mediated. Histology analysis confirmed similar expression of σ1 and σ2 in PC-3 tumors which was significantly greater than its expression in normal organs/tissues such as liver, kidney, and muscle. Metabolite studies revealed that >50% of radioactivity in PC-3 tumors at 30 min postinjection represented intact [18F]3a. Prominent σ receptor-specific uptake of [18F]3a in prostate tumors and its subsequent clear visualization with PET imaging indicate potential utility for the diagnosis of prostate carcinoma.
Sigma-1 and sigma-2 receptors are potential targets for therapeutic and diagnostic agents for various types of cancer. Sigma-1 receptors promote proliferation and survival, whereas activation of sigma-2 receptors induces apoptosis. Thus, there has been particular focus on sigma-2 receptors, which may be related to the PGRMC1 complex. While several selective ligands for sigma-2 receptors have been developed, there is a scarcity of tools for studying structure and function, particularly antagonists. SN-79 is a high affinity ligand for sigma-2 receptors, with 10-fold selectivity for sigma-2 over sigma-1 (Ki = 30 nM vs. 290 nM, respectively). Four isothiocyanate derivatives of SN-79 were characterized in rat liver membranes using [3H](+)-pentazocine to label sigma-1 and [3H]DTG (in presence of unlabeled (+)-pentazocine) for sigma-2. The isothiocyanate derivatives all exhibited lower affinity for sigma-2 receptors compared to SN-79. Sigma-2 Ki values were 320, 102, 395, and 271 nM for CM-572, CM-617, CM-621, and CM-769, respectively. Irreversible binding was examined by pretreating membranes for 60 min with the compound, extensively washing the membranes, and then determining recovery of radioligand binding. Loss of radioligand binding upon pretreatment results from “wash-resistant binding” of the compound and indicates covalent attachment to the receptor. Pretreatment with 100 nM CM-572 or CM-617 resulted in recovery of only 25% and 40% of sigma-2 binding, respectively. Treatment with 100 nM CM-621 or CM-769 had no effect. Therefore, while all four compounds bind to sigma-2 receptors with roughly comparable affinities, only CM-572 and CM-617 bind irreversibly. None of the compounds had an effect on sigma-1 receptor binding, indicating selective acylation of the sigma-2 receptor. In dose studies, CM-572 exhibited an IC50 ∼30 nM. Human SK-N-SH neuroblastoma cells were used to examine the biological activity of CM-572. Cells were pretreated for 1 h with CM-572 at concentrations up to 100 uM, then washed free of ligand, normal media added, and monitored by MTT assay after 24 h. There was no effect on cell viability up to a concentration of 10 uM, where ∼20% cytotoxicity was observed. About 80% cytotoxicity was observed at 100 uM. This suggests that CM-572 may have an irreversible partial agonist effect. However, pretreatment with CM-572 was unable to attenuate cell death induced by the sigma-2 agonist, CB-64D. A component of the signaling cascade of sigma-2 receptor activation is calcium release from the ER. In Fura-2 loaded cells, CM-572 produced no calcium signal at 3 uM and a small signal at 10 uM, though much smaller than the robust signal induced by CB-64D. Larger signals were produced at 30 uM and 100 uM CM-572. Interestingly, 3 uM and 10 uM CM-572 attenuated the calcium signal induced by 30 uM CB-64D. Taken together, these data indicate that CM-572 may be an irreversible partial agonist at sigma-2 receptors. Citation Format: Hilary Nicholson, Anthony Comeau, Christophe Mesangeau, Christopher R. McCurdy, Wayne D. Bowen. Development of selective irreversible antagonists for sigma-2 receptors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2242. doi:10.1158/1538-7445.AM2013-2242
Ha Jin and his works have contributed significantly to world Englishes knowledge, both through direct scholarly engagement with contact literatures and through the linguistic creativity exhibited in his works of fiction (Jin 2010). His fiction writing also acts as a site of scholarly inquiry (e.g., Zhang 2002). Underexplored, however, are how local varieties of English as used to create queer identities. This paper will seek to address this gap by exploring how Ha Jin created queer spaces in his short story “The Bridegroom.” This investigation will utilize a Kachruvian world Englishes approach to analyzing contact literatures (B. Kachru 1985, 1990, Y. Kachru & Nelson 2006, Thumboo 2006). This analysis will be supported by interfacing it with perspectives from the fields of queer theory and queer linguistics (Jagose 1996, Leap & Motschenbacher 2012), which will allow for a contextually sensitive understanding of queer experiences in China. This approach will enable us to examine how Ha Jin utilized the rhetorical and linguistic markers of China English to explore historical attitudes towards queerness during the post-Cultural Revolution period. These markers include the use of local idioms and culturally-localized rhetorical moves to render a uniquely Chinese queer identity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.