Cytotoxic Sigma-2 Ligands Trigger Cancer Cell Death via Cholesterol-Induced-ER-Stress
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PROVIDER: PRJNA1082203 | ENA |
REPOSITORIES: ENA
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Project description:Sigma-2-ligands (S2L) are characterized by high-affinity interaction with their cognate sigma-2 receptor, overexpressed in rapidly proliferating tumor cells. As such, S2L were developed as imaging probes (ISO1) or as cancer therapeutics, alone (SV119 [C6], SW43 [C10]) and as delivery vehicles for cytotoxic drug cargoes following chemical conjugation (C6-Erastin, C10-SMAC). However, the exact mechanism of S2L-induced cytotoxicity remains to be fully elucidated. A series of high-affinity S2L were evaluated regarding their cytotoxicity profiles across pancreatic, ovarian, and synovial cancer cell lines. While C6 and C10 displayed distinct cytotoxicities (extended aliphatic side chains), C0 (no aliphatic side chain) and ISO1 (structurally unrelated) were essentially non-toxic, enabling us to investigate the unique mechanism of S2L cytotoxicity. Confocal microscopy and lipidomics analysis in cellular and mouse models revealed that C10 induced an increase in intralysosomal free cholesterol, a corresponding increase in cholesterol esters, suggestive of unaltered intracellular cholesterol trafficking and processing, and cytotoxicity due to cholesterol excess, a phenomenon that contrasts the effects of inhibiting NPC1 function. RNA-sequencing revealed that gene clusters involved in cholesterol homeostasis and ER stress response were activated exclusively by cytotoxic S2L. ER stress markers were confirmed on qPCR, and ER stress modulators inhibited or enhanced cytotoxicity of C10 confirming the involvement of ER stress response in the cytotoxicity of S2L. Moreover, C10 increased sterol regulatory element-binding protein 2 (SREBP2) and low-density lipoprotein receptor (LDLR) which were also confirmed with qPCR and at the protein level and were found to be a pro-survival mechanism activated by ER stress response. Moreover, inhibiting the processes downstream this adaptive response with simvastatin resulted in synergistic treatment outcomes when combined with C10 in vitro and in vivo. Of note, the conjugates retained the S2L-mediated cholesterol phenotype of their parental ligands, which suggests that disrupting cholesterol homeostasis might contribute to the overall cytotoxicity of the drug conjugates. Furthermore, these phenomena were seen exclusively with cytotoxic S2L. Based on these findings, we conclude that S2L-mediated cell death is due to free cholesterol accumulation that leads to ER stress. Consequently, the cytotoxic profiles of S2L drug conjugates are proposed to be enhanced via concurrent ER stress inducers or simvastatin, strategies that could be instrumental on the path toward tumor eradication.
2024-04-30 | GSE260557 | GEO
Project description:Defects in the apoptotic machinery can contribute to tumor formation and resistance to treatment, creating a need to identify new agents that kill cancer cells by alternative mechanisms. To this end, we examined the cytotoxic properties of a novel peptide, CT20p, derived from the C-terminal, alpha-9 helix of Bax, an amphipathic domain with putative membrane binding properties. Like many antimicrobial peptides, CT20p contains clusters of hydrophobic and cationic residues that could enable the peptide to associate with lipid membranes. CT20p caused the release of calcein from mitochondrial-like lipid vesicles without disrupting vesicle integrity and, when expressed as a fusion protein in cells, localized to mitochondria. The amphipathic nature of CT20p allowed it to be encapsulated in polymeric nanoparticles (NPs) that have the capacity to harbor targeting molecules, dyes or drugs. The resulting CT20p-NPs proved an effective killer, in vitro, of colon and breast cancer cells, and in vivo, using a murine breast cancer tumor model. By introducing CT20p to Bax deficient cells, we demonstrated that the peptide's lethal activity was independent of endogenous Bax. CT20p also caused an increase in the mitochondrial membrane potential that was followed by plasma membrane rupture and cell death, without the characteristic membrane asymmetry associated with apoptosis. We determined that cell death triggered by the CT20p-NPs was minimally dependent on effector caspases and resistant to Bcl-2 overexpression, suggesting that it acts independently of the intrinsic apoptotic death pathway. Furthermore, use of CT20p with the apoptosis-inducing drug, cisplatin, resulted in additive toxicity. These results reveal the novel features of CT20p that allow nanoparticle-mediated delivery to tumors and the potential application in combination therapies to activate multiple death pathways in cancer cells.
| S-EPMC3458162 | biostudies-literature
Project description:BackgroundThe 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.MethodsEMT-6 and MDA-MB-435 cells were treated with sigma-2 ligands. The modulation of multiple signaling pathways of cell death was evaluated.ResultsThree 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 μM 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.ConclusionSigma-2 ligands induce cell death by multiple signalling pathways.
| S-EPMC3322954 | biostudies-literature
Project description:G-quadruplexes (G4s) and R-loops are non-canonical DNA structures that can play regulatory functions of basic nuclear processes and can trigger DNA damage and genome instability. We here show that specific G4 ligands can stabilize G4s and simultaneously increase R-loop levels in human cancer cells likely by spreading DNA:RNA heteroduplexes to adjacent regions containing G4 structures. DNA cleavage and DNA damage response induced by G4 ligands were rescued by overexpression of exogenous RNaseH1 in cancer cells independently of BRCA2 status. The data thus show that R-loops are involved in the induction of DNA damage by chemical G4 stabilization. In addition, G4 ligands trigger the formation of micronuclei, particularly in BRCA2-silenced cancer cells, in an R-loop dependent manner. Our results uncover the mechanism of genome instability caused by G4 ligands and can open to the development of unexpected anticancer strategies using G4-targeted agents.
2018-12-27 | GSE115957 | GEO
Project description:One major challenge in the development of cancer therapeutics is the selective delivery of the drugs to their cellular targets. In the case of pancreatic cancer, the ?-2 receptor is a unique target that triggers apoptosis upon activation. We have previously developed a series of chemical compounds with high affinity for the ?-2 receptor and showed rapid internalization of the ligands. One particular specific ligand of the ?-2 receptor, SV119, binds to pancreatic cancer cells and induces target cell death in vitro and in vivo. In this study, we characterized the ability of SV119 to selectively deliver other death-inducing cargos to augment the cytotoxic properties of SV119 itself. When conjugated to SV119, small molecules that are known to interfere with intracellular prosurvival pathways retained their ability to induce cell death, the efficiency of which was enhanced by the combinatorial effect of SV119 delivered with its small molecule cargo. Our findings define a simple platform technology to increase the tumor-selective delivery of small molecule therapeutics via ?-2 ligands, permitting chemotherapeutic synergy that can optimize efficacy and patient benefit.
| S-EPMC3251632 | biostudies-literature
Project description:Characterization of S.lividans TK24 secreted proteome changes upon deletion of certain sigma factors.
2019-02-16 | PXD006818 | Pride
Project description:Since their discovery as distinct receptor proteins, the specific physiopathological role of sigma receptors (σRs) has been deeply investigated. It has been reported that these proteins, classified into two subtypes indicated as σ1 and σ2, might play a pivotal role in cancer growth, cell proliferation, and tumor aggressiveness. As a result, the development of selective σR ligands with potential antitumor properties attracted significant attention as an emerging theme in cancer research. This perspective deals with the recent advances of σR ligands as novel cytotoxic agents, covering articles published between 2010 and 2020. An up-to-date description of the medicinal chemistry of selective σ1R and σ2R ligands with antiproliferative and cytotoxic activities has been provided, including major pharmacophore models and comprehensive structure-activity relationships for each main class of σR ligands.
| S-EPMC8279423 | biostudies-literature
Project description:Abstract of associated manuscript: The Bacillus subtilis extracytoplasmic function (ECF) sigma(M) factor is activated by cell envelope stress elicited by antibiotics, and by acid, heat, ethanol and superoxide stresses. Here, we have used several complementary approaches to identify genes controlled by sigma(M). In many cases, expression is only partially dependent on sigma(M) because of both overlapping promoter recognition with other ECF sigma factors and the presence of additional promoter elements. Genes regulated by sigma(M) have a characteristic pattern of induction in response to cell envelope-acting antibiotics as evidenced by hierarchical clustering analysis. sigma(M) also contributes to the expression of the Spx transcription factor and thereby indirectly regulates genes of the Spx regulon. Cell envelope stress responses also include regulons controlled by sigma(W), sigma(B) and several two-component regulatory systems (e.g. LiaRS, YycFG, BceRS). Activation of the sigma(M) regulon increases expression of proteins functioning in transcriptional control, cell wall synthesis and shape determination, cell division, DNA damage monitoring, recombinational repair and detoxification.
2008-12-05 | GSE13820 | GEO
Project description:Lytic cell death, such as pyroptosis, can trigger antitumour immune response. However, cancerous cells avoid lytic cell death by various escape mechanisms acquired through evolution. Moreover, persistent uncontrolled lytic cell death may inversely cause hyperactive immune response or T-cell exhaustion. Therefore, an oncolytic system capable of breaking through natural restrictions to dissolve cancer cells in a catalytic and controllable manner is needed. Here, we established a microscale cytotoxic T-cell-inspired oncolytic system (TIOs) by which the NIR light-generated reactive oxygen species could precisely rupture the plasma membrane of cancer cells by direct lipids peroxidation. Similar as cytotoxic T cells, TIOs present antigen-based cell recognition and catalytic cell-lysis ability; thus, the TIOs can trigger significant oncolysis and immune response in vivo. The TIOs exhibited exceptional tumour targeting and penetration without any inflammatory risk. We applied TIOs to antitumour therapies, which showed kinds of tumour models could be cleared efficiently with negligible injuries to major organs. Tumour regression was correlated with oncolysis-mediated inflammation and T-cell-based antitumor immune response. Owing to the tuneability of TIOs-mediated oncolysis, we further revealed that though the T-cell recruitment was comparable, the high-intense oncolysis induced acute inflammation in initial stage was crucial for potent antitumour immunity and immune memory effects, and low-intense oncolysis resulted in T-cell exhaustion and tumour progression. To the mice received low-intense oncolysis, although synergizing with anti-PD-1 therapies or STING activation rescued the immune dysfunction, STING activation released a more powerful boost to durative antitumour immunity by reshaping the stemness of CD8+ T cells. Our study provides new insights to design the oncolytic systems for antitumour immunity. Moreover, our application suggests that the intensity of initial inflammation plays a decisive role in maintaining oncolysis-induced antitumour immune function and STING activation holds promise for reversal of immune dysfunction due to T-cell exhaustion.
2023-08-22 | GSE227675 | GEO