PDF(Pubmed)
Abstract：
Sigma-2-ligands (S2L) are characterized by high binding affinities to 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 (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 cancer cell lines. While C6 and C10 displayed distinct cytotoxicities, C0 and ISO1 were essentially non-toxic. Confocal microscopy and lipidomics analysis in cellular and mouse models revealed that C10 induced increases in intralysosomal free cholesterol and in cholesterol esters, suggestive of unaltered intracellular cholesterol trafficking. Cytotoxicity was caused by cholesterol excess, a phenomenon that contrasts the effects of NPC1 inhibition. RNA-sequencing revealed gene clusters involved in cholesterol homeostasis and ER stress response exclusively by cytotoxic S2L. ER stress markers were confirmed by qPCR and their targeted modulation inhibited or enhanced cytotoxicity of C10 in a predicted manner. Moreover, C10 increased sterol regulatory element-binding protein 2 (SREBP2) and low-density lipoprotein receptor (LDLR), both found to be pro-survival factors activated by ER stress. Furthermore, inhibition of downstream processes of the adaptive response to S2L with simvastatin resulted in synergistic treatment outcomes in combination with C10. Of note, the S2L conjugates retained the ER stress response of the parental ligands, indicative of cholesterol homeostasis being involved in the overall cytotoxicity of the drug conjugates. 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.
摘要：
Sigma-2-配体（S2L）的特征是对其同源sigma-2受体的高结合亲和力，在快速增殖的肿瘤细胞中过表达。因此，S2L被开发为成像探针（ISO1）或癌症治疗剂，单独(SV119[C6]，SW43[C10])和作为细胞毒性药物货物的运载工具(C6-Erastin，C10-SMAC）。然而,S2L诱导的细胞毒性的确切机制仍有待完全阐明。评估了一系列高亲和力S2L在癌细胞系中的细胞毒性谱。虽然C6和C10表现出不同的细胞毒性，C0和ISO1基本上是无毒的。细胞和小鼠模型的共聚焦显微镜和脂质组学分析显示，C10诱导溶酶体内游离胆固醇和胆固醇酯的增加，提示未改变的细胞内胆固醇运输。细胞毒性是由胆固醇过量引起的，与NPC1抑制作用形成对比的现象。RNA测序揭示了仅由细胞毒性S2L参与胆固醇稳态和ER应激反应的基因簇。通过qPCR确认ER应激标志物,并且它们的靶向调节以预测的方式抑制或增强C10的细胞毒性。此外，C10增加了固醇调节元件结合蛋白2（SREBP2）和低密度脂蛋白受体（LDLR），两者都被发现是内质网应激激活的促生存因素。此外，辛伐他汀对S2L适应性反应的下游过程的抑制导致C10联合治疗结果的协同作用.值得注意的是，S2L缀合物保留了亲本配体的ER应激反应，表明胆固醇稳态参与药物缀合物的整体细胞毒性。基于这些发现,我们得出结论,S2L介导的细胞死亡是由于游离胆固醇积累导致内质网应激.因此,S2L药物缀合物的细胞毒性谱被提出通过并发ER应激诱导剂或辛伐他汀增强，可能有助于根除肿瘤的策略。
