Department of Experimental Biology, Faculty of Science, Masaryk University, 62500, Brno, Czech Republic.
International Clinical Research Center, St. Anne's University Hospital, 65691, Brno, Czech Republic.
Cell Death Dis. 2023 Nov 16;14(11):747. doi: 10.1038/s41419-023-06278-x.
Mitochondria are central for cancer responses to therapy-induced stress signals. Refractory tumors often show attenuated sensitivity to apoptotic signaling, yet clinically relevant molecular actors to target mitochondria-mediated resistance remain elusive. Here, we show that MYC-driven neuroblastoma cells rely on intact mitochondrial ribosome (mitoribosome) processivity and undergo cell death following pharmacological inhibition of mitochondrial translation, regardless of their multidrug/mitochondrial resistance and stem-like phenotypes. Mechanistically, inhibiting mitoribosomes induced the mitochondrial stress-activated integrated stress response (ISR), leading to downregulation of c-MYC/N-MYC proteins prior to neuroblastoma cell death, which could be both rescued by the ISR inhibitor ISRIB. The ISR blocks global protein synthesis and shifted the c-MYC/N-MYC turnover toward proteasomal degradation. Comparing models of various neuroectodermal tumors and normal fibroblasts revealed overexpression of MYC proteins phosphorylated at the degradation-promoting site T58 as a factor that predetermines vulnerability of MYC-driven neuroblastoma to mitoribosome inhibition. Reducing N-MYC levels in a neuroblastoma model with tunable MYCN expression mitigated cell death induction upon inhibition of mitochondrial translation and functionally validated the propensity of neuroblastoma cells for MYC-dependent cell death in response to the mitochondrial ISR. Notably, neuroblastoma cells failed to develop significant resistance to the mitoribosomal inhibitor doxycycline over a long-term repeated (pulsed) selection. Collectively, we identify mitochondrial translation machinery as a novel synthetic lethality target for multidrug-resistant MYC-driven tumors.
线粒体在癌症对治疗诱导的应激信号的反应中起核心作用。难治性肿瘤通常对凋亡信号的敏感性降低，但临床上仍难以确定靶向线粒体介导的耐药性的相关分子靶点。在这里，我们表明，即使存在多药/线粒体耐药性和干细胞样表型，MYC 驱动的神经母细胞瘤细胞仍依赖完整的线粒体核糖体（mitoribosome）进程，并在抑制线粒体翻译的药物治疗后发生细胞死亡。从机制上讲，抑制 mitoribosomes 诱导了线粒体应激激活的综合应激反应（ISR），导致神经母细胞瘤细胞死亡前 c-MYC/N-MYC 蛋白下调，这可以被 ISR 抑制剂 ISRIB 挽救。ISR 阻断了全局蛋白质合成，并将 c-MYC/N-MYC 周转率转向蛋白酶体降解。比较各种神经外胚层肿瘤和正常成纤维细胞模型显示，作为决定 MYC 驱动的神经母细胞瘤对 mitoribosome 抑制易感性的因素，在促进降解的位点 T58 磷酸化的 MYC 蛋白过表达。在具有可调节 MYCN 表达的神经母细胞瘤模型中降低 N-MYC 水平，可减轻抑制线粒体翻译后诱导的细胞死亡，并在功能上验证了神经母细胞瘤细胞对线粒体 ISR 下依赖 MYC 的细胞死亡的倾向。值得注意的是，神经母细胞瘤细胞在长期重复（脉冲）选择过程中对 mitoribosomal 抑制剂强力霉素未产生明显的耐药性。总之，我们将线粒体翻译机制确定为多药耐药性 MYC 驱动肿瘤的新的合成致死性靶点。
