Kiesel Violet A, Sheeley Madeline P, Hicks Emily M, Andolino Chaylen, Donkin Shawn S, Wendt Michael K, Hursting Stephen D, Teegarden Dorothy
Purdue University, Department of Nutrition Science, West Lafayette, IN, United States.
Purdue University, Department of Animal Science, West Lafayette, IN, United States.
Front Oncol. 2022 Jun 30;12:767479. doi: 10.3389/fonc.2022.767479. eCollection 2022.
Regions of hypoxia are common in solid tumors and drive changes in gene expression that increase risk of cancer metastasis. Tumor cells must respond to the stress of hypoxia by activating genes to modify cell metabolism and antioxidant response to improve survival. The goal of the current study was to determine the effect of hypoxia on cell metabolism and markers of oxidative stress in metastatic (metM-Wnt) compared with nonmetastatic (M-Wnt) murine mammary cancer cell lines. We show that hypoxia induced a greater suppression of glutamine to glutamate conversion in metastatic cells (13% in metastatic cells compared to 7% in nonmetastatic cells). We also show that hypoxia increased expression of genes involved in antioxidant response in metastatic compared to nonmetastatic cells, including glutamate cysteine ligase catalytic and modifier subunits and malic enzyme 1. Interestingly, hypoxia increased the mRNA level of the transaminase glutamic pyruvic transaminase 2 (Gpt2, 7.7-fold) only in metM-Wnt cells. The change in Gpt2 expression was accompanied by transcriptional (4.2-fold) and translational (6.5-fold) induction of the integrated stress response effector protein activating transcription factor 4 (ATF4). Genetic depletion ATF4 demonstrated importance of this molecule for survival of hypoxic metastatic cells in detached conditions. These findings indicate that more aggressive, metastatic cancer cells utilize hypoxia for metabolic reprogramming and induction of antioxidant defense, including activation of ATF4, for survival in detached conditions.
缺氧区域在实体瘤中很常见，并驱动基因表达变化，增加癌症转移风险。肿瘤细胞必须通过激活基因来应对缺氧应激，以改变细胞代谢和抗氧化反应，从而提高生存率。本研究的目的是确定与非转移性（M-Wnt）小鼠乳腺癌细胞系相比，缺氧对转移性（metM-Wnt）细胞代谢和氧化应激标志物的影响。我们发现，缺氧对转移性细胞中谷氨酰胺向谷氨酸转化的抑制作用更强（转移性细胞中为13%，非转移性细胞中为7%）。我们还发现，与非转移性细胞相比，缺氧会增加转移性细胞中参与抗氧化反应的基因表达，包括谷氨酸半胱氨酸连接酶催化亚基和调节亚基以及苹果酸酶1。有趣的是，缺氧仅在metM-Wnt细胞中增加了转氨酶谷丙转氨酶2（Gpt2，7.7倍）的mRNA水平。Gpt2表达的变化伴随着综合应激反应效应蛋白激活转录因子4（ATF4）的转录（4.2倍）和翻译（6.5倍）诱导。基因敲除ATF4证明了该分子对缺氧转移性细胞在脱离条件下存活的重要性。这些发现表明，更具侵袭性的转移性癌细胞利用缺氧进行代谢重编程和诱导抗氧化防御，包括激活ATF4，以在脱离条件下存活。
