目的:检测热休克蛋白90(heat shock protein90,Hsp90)抑制剂协同索拉非尼(Sorafenib)对肝癌耐药细胞的作用机制,并研究其对Sorafenib诱导肝癌耐药细胞铁死亡的增敏效应.方法:MTT法检测格尔德霉素(Geldanamycin)联用Sorafenib在抑制HepG2/Sorafenib细胞增殖中的联合效应;流式细胞术检测HepG2/Sorafenib及HepG2细胞株在Sorafenib作用下,细胞内活性氧(reactive oxygen species,ROS)水平的变化,以及Geldanamycin对细胞内ROS的协同诱导效应;FerroOrange染色法检测HepG2/Sorafenib及HepG2细胞株在Sorafenib作用下,细胞内二价铁离子水平变化;RT-PCR及Western blot实验检测Geldanamycin对铁死亡相关基因SLC7A11及GPX4等转录和表达的调节作用.结果:Geldanamycin可增强HepG2/Sorafenib耐药细胞株对Sorafenib的敏感性,经30 nmol/L浓度的Geldanamycin预处理后,Sorafenib的半数抑制率IC50由原来的(2.6±0.1)×103 nmol/L降为(37.2±6.9)nmol/L,变化差异显著(P<0.01).当Sorafenib浓度高于32 nmol/L后,二者的联用指数CI小于0.2,表明Geldanamycin与Sorafenib联用处理HepG2/Sorafenib耐药细胞株具有强烈的协同效应;HepG2/Sorafenib耐药细胞株经30 nmol/L Geldanamycin预处理后,其细胞内的ROS水平可重新被Sorafenib诱导,相同浓度下与无Geldanamycin处理组比较,增强了4.2倍(P<0.01);30 nmol/L Geldanamycin可显著增强Sorafenib诱导HepG2/Sorafenib细胞内二价铁离子水平提高,提示其协同Sorafenib促细胞铁死亡作用;Geldanamycin能通过Akt-Nrf2途径下调SLC7A11蛋白的转录,并影响GPX4蛋白的表达.结论:抑制Hsp90能减弱肝癌耐药细胞株对Sorafenib诱导铁死亡的耐受性,其机制可能是通过阻断Akt/Nrf2介导的SLC7A11转录下调实现的.

masc RNA is a small cytoplasmic RNA derived from the lnc RNA MALAT 1 . After being processed by the tRNA processing enzymes RN ase P and RN ase Z, masc RNA undergoes CCA addition like tRNA s and folds into a tRNA ‐like cloverleaf structure. While MALAT 1 functions in multiple cellular processes, the role of masc RNA was largely unknown. Here, we show that masc RNA binds directly to the multi‐ tRNA synthetase complex ( MSC ) component glutaminyl‐ tRNA synthetase ( QARS ). masc RNA promotes global protein translation and cell proliferation by positively regulating QARS protein levels. Our results uncover a role of masc RNA that is independent of MALAT 1 , but could be part of the molecular mechanism of MALAT 1 's function in cancer, and provide a paradigm for understanding tRNA ‐like structures in mammalian cells.