Department of Medicine, University of Wisconsin Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA.
Department of Biotechnology, Sirius University of Science and Technology, 1 Olympic Ave, 354340, Sochi, Russia.
Breast Cancer Res Treat. 2021 Dec;190(3):373-387. doi: 10.1007/s10549-021-06398-y. Epub 2021 Sep 22.
Tumor cells are dependent on the glutathione and thioredoxin antioxidant pathways to survive oxidative stress. Since the essential amino acid methionine is converted to glutathione, we hypothesized that methionine restriction (MR) would deplete glutathione and render tumors dependent on the thioredoxin pathway and its rate-limiting enzyme thioredoxin reductase (TXNRD).
Triple (ER/PR/HER2)-negative breast cancer (TNBC) cells were treated with control or MR media and the effects on reactive oxygen species (ROS) and antioxidant signaling were examined. To determine the role of TXNRD in MR-induced cell death, TXNRD1 was inhibited by RNAi or the pan-TXNRD inhibitor auranofin, an antirheumatic agent. Metastatic and PDX TNBC mouse models were utilized to evaluate in vivo antitumor activity.
MR rapidly and transiently increased ROS, depleted glutathione, and decreased the ratio of reduced glutathione/oxidized glutathione in TNBC cells. TXNRD1 mRNA and protein levels were induced by MR via a ROS-dependent mechanism mediated by the transcriptional regulators NRF2 and ATF4. MR dramatically sensitized TNBC cells to TXNRD1 silencing and the TXNRD inhibitor auranofin, as determined by crystal violet staining and caspase activity; these effects were suppressed by the antioxidant N-acetylcysteine. H-Ras-transformed MCF-10A cells, but not untransformed MCF-10A cells, were highly sensitive to the combination of auranofin and MR. Furthermore, dietary MR induced TXNRD1 expression in mammary tumors and enhanced the antitumor effects of auranofin in metastatic and PDX TNBC murine models.
MR exposes a vulnerability of TNBC cells to the TXNRD inhibitor auranofin by increasing expression of its molecular target and creating a dependency on the thioredoxin pathway.
肿瘤细胞依赖谷胱甘肽和硫氧还蛋白抗氧化途径来存活氧化应激。由于必需氨基酸蛋氨酸被转化为谷胱甘肽，我们假设蛋氨酸限制（MR）会耗尽谷胱甘肽，使肿瘤依赖于硫氧还蛋白途径及其限速酶硫氧还蛋白还原酶（TXNRD）。
三阴性乳腺癌（TNBC）细胞用对照或 MR 培养基处理，检查对活性氧（ROS）和抗氧化信号的影响。为了确定 TXNRD 在 MR 诱导的细胞死亡中的作用，通过 RNAi 或泛 TXNRD 抑制剂 auranoffin（一种抗风湿剂）抑制 TXNRD1。利用转移性和 PDX TNBC 小鼠模型评估体内抗肿瘤活性。
MR 迅速且短暂地增加了 ROS，耗尽了谷胱甘肽，并降低了 TNBC 细胞中还原型谷胱甘肽/氧化型谷胱甘肽的比例。MR 通过 ROS 依赖性机制诱导 TXNRD1 的表达，该机制由转录调节剂 NRF2 和 ATF4 介导。MR 显著增强了 TNBC 细胞对 TXNRD1 沉默和 TXNRD 抑制剂 auranoffin 的敏感性，通过结晶紫染色和半胱天冬酶活性来确定；这些作用被抗氧化剂 N-乙酰半胱氨酸抑制。H-Ras 转化的 MCF-10A 细胞，而不是未转化的 MCF-10A 细胞，对 auranoffin 和 MR 的组合高度敏感。此外，饮食性 MR 诱导了乳腺肿瘤中 TXNRD1 的表达，并增强了 auranoffin 在转移性和 PDX TNBC 小鼠模型中的抗肿瘤作用。
MR 通过增加其分子靶标表达并使肿瘤对硫氧还蛋白途径产生依赖性，使 TNBC 细胞对 TXNRD 抑制剂 auranoffin 变得脆弱。
