title: Effective tumor cell death by sigma-2 receptor ligand siramesine involves lysosomal leakage and oxidative stress.
abstract: Acquired resistance to classic caspase-mediated apoptosis is a common problem for the treatment of human cancer. Here, we show that siramesine, a novel sigma-2 receptor ligand, effectively induces caspase-independent programmed cell death in immortalized and transformed cells of various origins. Siramesine-treated tumor cells displayed increased levels of reactive oxygen species, lysosomal membrane permeabilization, chromatin condensation, and shrinkage and detachment of cells. Lipid antioxidants (alpha-tocopherol and gamma-tocopherol), but not other tested antioxidants (butylated hydroxyanisol or N-acetyl cysteine), effectively inhibited siramesine-induced morphologic changes and cell death. Cathepsin B inhibitors (CA-074-Me and R-2525) conferred similar, but less pronounced protection, whereas ectopic expression of antiapoptotic protein Bcl-2, lack of wild-type p53 as well as pharmacologic inhibitors of caspases (zVAD-fmk, DEVD-CHO, and LEHD-CHO), calpains (PD150606), and serine proteases (N-tosyl-L-phenylalanine chloromethyl ketone and pefabloc) failed to protect cells against siramesine-induced death. Importantly, transformation of murine embryonic fibroblasts with activated c-src or v-Ha-ras oncogenes greatly sensitized them to siramesine-induced cytotoxicity. Furthermore, p.o. administration of well-tolerated doses of siramesine had a significant antitumorigenic effect in orthotopic breast cancer and s.c. fibrosarcoma models in mice. These results present siramesine as a promising new drug for the treatment of tumors resistant to traditional therapies.
authors.affiliation: Apoptosis Department, Institute for Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
authors.forename: Marie Stampe
authors.initials: MS
authors.lastname: Ostenfeld
authors.forename: Nicole
authors.initials: N
authors.lastname: Fehrenbacher
authors.forename: Maria
authors.initials: M
authors.lastname: Høyer-Hansen
authors.forename: Christian
authors.initials: C
authors.lastname: Thomsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Farkas
authors.forename: Marja
authors.initials: M
authors.lastname: Jäättelä
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002403:Cathepsins / Q000378:metabolism; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D005260:Female; D005354:Fibrosarcoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008024:Ligands; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects; D017480:Receptors, sigma / Q000378:metabolism*; D013141:Spiro Compounds / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; D008024:Ligands; C109644:Lu 28-179; D017480:Receptors, sigma; D013141:Spiro Compounds; D016159:Tumor Suppressor Protein p53; C106107:sigma-2 receptor; D045304:Cytochromes c; D002403:Cathepsins; D020169:Caspases