Kim Yeon Soo, Tang Priscilla W, Welles Jaclyn E, Pan Weihua, Javed Zaineb, Elhaw Amal Taher, Mythreye Karthikeyan, Kimball Scot R, Hempel Nadine
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA.
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA; Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA.
Redox Biol. 2022 Jul;53:102329. doi: 10.1016/j.redox.2022.102329. Epub 2022 May 13.
During metastasis cancer cells must adapt to survive loss of anchorage and evade anoikis. An important pro-survival adaptation is the ability of metastatic tumor cells to increase their antioxidant capacity and restore cellular redox balance. Although much is known about the transcriptional regulation of antioxidant enzymes in response to stress, how cells acutely adapt to alter antioxidant enzyme levels is less well understood. Using ovarian cancer cells as a model, we demonstrate that an increase in mitochondrial superoxide dismutase SOD2 protein expression is a very early event initiated in response to detachment, an important step during metastasis that has been associated with increased oxidative stress. SOD2 protein synthesis is rapidly induced within 0.5-2 h of matrix detachment, and polyribosome profiling demonstrates an increase in the number of ribosomes bound to SOD2 mRNA, indicating an increase in SOD2 mRNA translation in response to anchorage-independence. Mechanistically, we find that anchorage-independence induces cytosolic accumulation of the RNA binding protein HuR/ELAVL1 and promotes HuR binding to SOD2 mRNA. Using HuR siRNA-mediated knockdown, we show that the presence of HuR is necessary for the increase in SOD2 mRNA association with the heavy polyribosome fraction and consequent nascent SOD2 protein synthesis in anchorage-independence. Cellular detachment also activates the stress-response mitogen-activated kinase p38, which is necessary for HuR-SOD2 mRNA interactions and induction of SOD2 protein output. These findings illustrate a novel translational regulatory mechanism of SOD2 by which ovarian cancer cells rapidly increase their mitochondrial antioxidant capacity as an acute stress response to anchorage-independence.
在转移过程中，癌细胞必须适应失去锚定并逃避失巢凋亡。一种重要的促生存适应机制是转移性肿瘤细胞增加其抗氧化能力并恢复细胞氧化还原平衡的能力。尽管我们对抗氧化酶在应激反应中的转录调控了解很多，但细胞如何快速适应改变抗氧化酶水平却知之甚少。以卵巢癌细胞为模型，我们证明线粒体超氧化物歧化酶SOD2蛋白表达的增加是在细胞脱离时启动的非常早期的事件，这是转移过程中的一个重要步骤，与氧化应激增加有关。SOD2蛋白合成在基质脱离后0.5 - 2小时内迅速被诱导，多核糖体分析表明与SOD2 mRNA结合的核糖体数量增加，表明在脱离锚定后SOD2 mRNA翻译增加。从机制上讲，我们发现脱离锚定诱导RNA结合蛋白HuR/ELAVL1在细胞质中积累，并促进HuR与SOD2 mRNA结合。使用HuR siRNA介导的敲低，我们表明HuR的存在对于在脱离锚定后SOD2 mRNA与重多核糖体组分结合增加以及随后新生SOD2蛋白合成是必要的。细胞脱离还激活应激反应丝裂原活化激酶p38，这对于HuR - SOD2 mRNA相互作用和SOD2蛋白输出的诱导是必要的。这些发现阐明了SOD2的一种新的翻译调控机制，通过该机制卵巢癌细胞迅速增加其线粒体抗氧化能力，作为对脱离锚定的急性应激反应。
