CHAC1 degradation of glutathione enhances cystine-starvation-induced necroptosis and ferroptosis in human triple negative breast cancer cells via the GCN2-eIF2α-ATF4 pathway
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Meng-Shian Chen1,2, Sheng-Fan Wang1,3, Chih-Yi Hsu4, Pen-Hui Yin5, Tien-Shun Yeh6, Hsin-Chen Lee1,2 and Ling-Ming Tseng2,7,8
1Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
2Taipei-Veterans General Hospital, Comprehensive Breast Health Center, Taipei 112, Taiwan
3Department of Pharmacy, Taipei Veterans General Hospital, Taipei 112, Taiwan
4Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei 112, Taiwan
5Department of Medical Research, Taipei Veterans General Hospital, Taipei 112, Taiwan
6Department of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
7Department of Surgery, Taipei Veterans General Hospital, Taipei 112, Taiwan
8Department of Surgery, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
Hsin-Chen Lee, email: firstname.lastname@example.org
Ling-Ming Tseng, email: email@example.com
Keywords: TNBC; cystine starvation; glutathione; necroptosis; ferroptosis
Received: August 13, 2017 Accepted: November 13, 2017 Published: December 09, 2017
Cancer cells exhibit an abnormal amino acid metabolism and a dependence on specific amino acids, which might provide potential targets for treating cancer patients. In this study, we demonstrated that human triple negative breast cancer (TNBC) cells were highly susceptible to cystine starvation. We found that necrostatin-1 (Nec-1, a RIP1 inhibitor), necrosulfonamide (an MLKL inhibitor), deferoxamine (an ion chelator), ferrostatin-1 (a ferroptosis inhibitor) and RIP1 knockdown can prevent cystine-starvation-induced cell death, suggesting that cystine starvation induces necroptosis and ferroptosis in TNBC cells. Moreover, cystine starvation induced mitochondrial fragmentation, dysfunction, and ROS production. A mitochondrial ROS scavenger, Necrox-5, can prevent cystine-starvation-induced cell death. In addition, cystine starvation was found to activate GCN2, but not PERK, to increase the phosphorylation of eIF2α at serine 51, the protein expression of ATF4, and the expression of ATF4 target genes such as CHAC1, which might be downstream of the RIP1/RIP3-MLKL pathway and contribute to cystine-starvation-induced cell death. Knockdown of CHAC1 rescued the cystine-starvation-induced reduction in glutathione (GSH) levels and cell death. Furthermore, N-acetyl-cysteine (NAC), Trolox, and Nec-1 significantly prevented the cystine-starvation-induced increase in intracellular ROS levels, mitochondrial fragmentation and cell death. In summary, these results suggest that CHAC1 degradation of GSH enhances cystine-starvation-induced necroptosis and ferroptosis through the activated GCN2-eIF2α-ATF4 pathway in TNBC cells. Our findings improve our understanding of the mechanism underlying cystine-starvation-induced TNBC cell death.
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