Sigma-2 ligands induce tumour cell death by multiple signalling pathways

Abstract

Background:The sigma-2 receptor has been identified as a biomarker of proliferating cells in solid tumours. In the present study, we studied the mechanisms of sigma-2 ligand-induced cell death in the mouse breast cancer cell line EMT-6 and the human melanoma cell line MDA-MB-435.Methods:EMT-6 and MDA-MB-435 cells were treated with sigma-2 ligands. The modulation of multiple signaling pathways of cell death was evaluated.Results:Three sigma-2 ligands (WC-26, SV119 and RHM-138) induced DNA fragmentation, caspase-3 activation and PARP-1 cleavage. The caspase inhibitor Z-VAD-FMK partially blocked DNA fragmentation and cytotoxicity caused by these compounds. These data suggest that sigma-2 ligand-induced apoptosis and caspase activation are partially responsible for the cell death. WC-26 and siramesine induced formation of vacuoles in the cells. WC-26, SV119, RHM-138 and siramesine increased the synthesis and processing of microtubule-associated protein light chain 3, an autophagosome marker, and decreased the expression levels of the downstream effectors of mammalian target of rapamycin (mTOR), p70S6K and 4EBP1, suggesting that sigma-2 ligands induce autophagy, probably by inhibition of the mTOR pathway. All four sigma-2 ligands decreased the expression of cyclin D1 in a time-dependent manner. In addition, WC-26 and SV119 mainly decreased cyclin B1, E2 and phosphorylation of retinoblastoma protein (pRb); RHM-138 mainly decreased cyclin E2; and 10 μ siramesine mainly decreased cyclin B1 and pRb. These data suggest that sigma-2 ligands also impair cell-cycle progression in multiple phases of the cell cycle.Conclusion:Sigma-2 ligands induce cell death by multiple signalling pathways.

Characterization of CM572, a Selective Irreversible Partial Agonist of the Sigma-2 Receptor with Antitumor Activity

“…Although we have not investigated the effect of CM572 in a melanoma cell line, several studies by others have demonstrated cytotoxic effects of sigma-2 agonists on melanoma in vitro. The nonselective sigma-2 receptor agonist haloperidol induced apoptosis in mouse B16 and human SK-MEL-28 melanoma cells, and the highly selective sigma-2 agonists SV119, WC-26, RHM-138, and siramesine all induced apoptosis in human MDA-MB-435 melanoma cells (Nordenberg et al, 2005;Zeng et al, 2012Zeng et al, , 2014. Thus, it is reasonable to assume that CM572 would also induce apoptosis in melanoma cells.…”

“…Ligands presumed to activate sigma-2 receptors induce apoptotic cell death in cancer cell lines (Vilner et al, 1995a;Crawford and Bowen, 2002;Ostenfeld et al, 2005;Bowen, 2007;Abate et al, 2012;Zeng et al, 2012;Mach et al, 2013). Because of these aspects, the sigma-2 receptor has received growing attention as a potential target in cancer therapy, and efforts are in progress to elucidate the identity and function of this protein and to develop highly selective targeting ligands.…”

“…Several aspects of the purported sigma-2 signaling mechanism have been used in an attempt to define agonists. For example, Mach and colleagues have used the criteria of caspase-3 activation and loss of cell viability in EMT-6 mouse breast cancer and MDA-MB-435 human melanoma cells to define putative sigma-2 agonists and antagonists that correlated with comparisons to siramesine (19-{4-[1-(4-fluorophenyl)-1H-indol-3-yl]butyl}-3H-spiro[2-benzofuran-1,49-piperidine]), a presumed sigma-2 full agonist (Ostenfeld et al, 2005;Zeng et al, 2012Zeng et al, , 2014. The sigma-2 receptors mediate a rapid and transient calcium release from the endoplasmic reticulum of SK-N-SH neuroblastoma cells (Vilner and Bowen, 2000;Cassano et al, 2009).…”

Sigma-2 Receptors Play a Role in Cellular Metabolism: Stimulation of Glycolytic Hallmarks by CM764 in Human SK-N-SH Neuroblastoma

“…A variety of pathways have been described in response to sigma-2 receptor activation, indicating that there exists more than one mechanism of sigma-2 receptor-induced cell death (Zeng et al, 2012). Furthermore, discrete ligands induce independent apoptotic pathways even within a cell type, again suggesting the ability of the sigma-2 receptor to activate multiple signaling pathways (Crawford and Bowen 2002;Cassano et al, 2009;Zeng et al, 2012;Cesen et al, 2013). The sigma-2 receptor has received attention for its potential use as a chemotherapeutic target.…”

“…Upon activation, the sigma-2 receptor induces apoptotic cell death (Crawford and Bowen 2002;Zeng et al, 2012Zeng et al, , 2014. A variety of pathways have been described in response to sigma-2 receptor activation, indicating that there exists more than one mechanism of sigma-2 receptor-induced cell death (Zeng et al, 2012).…”