Genetic Disruption of the γ-Glutamylcysteine Ligase in PDAC Cells Induces Ferroptosis-Independent Cell Death In Vitro without Affecting In Vivo Tumor Growth

Abstract

The conceptualization of a novel type of cell death, called ferroptosis, opens new avenues for the development of more efficient anti-cancer therapeutics. In this context, a full understanding of the ferroptotic pathways, the players involved, their precise role, and dispensability is prerequisite. Here, we focused on the importance of glutathione (GSH) for ferroptosis prevention in pancreatic ductal adenocarcinoma (PDAC) cells. We genetically deleted a unique, rate-limiting enzyme for GSH biosynthesis, γ-glutamylcysteine ligase (GCL), which plays a key role in tumor cell proliferation and survival. Surprisingly, although glutathione peroxidase 4 (GPx4) has been described as a guardian of ferroptosis, depletion of its substrate (GSH) led preferentially to apoptotic cell death, while classical ferroptotic markers (lipid hydroperoxides) have not been observed. Furthermore, the sensitivity of PDAC cells to the pharmacological/genetic inhibition of GPx4 revealed GSH dispensability in this context. To the best of our knowledge, this is the first time that the complete dissection of the xCT-GSH-GPx4 axis in PDAC cells has been investigated in great detail. Collectively, our results revealed the necessary role of GSH in the overall redox homeostasis of PDAC cells, as well as the dispensability of this redox-active molecule for a specific, antioxidant branch dedicated to ferroptosis prevention.

Metabolic Rewiring toward Oxidative Phosphorylation Disrupts Intrinsic Resistance to Ferroptosis of the Colon Adenocarcinoma Cells

“…The selenoenzyme glutathione peroxidase 4 (GPX4) plays a central role in protecting membrane PUFAs from these oxidative insults, i.e., in protecting cells from ferroptosis by converting lipid hydroperoxides into their less toxic alcohol derivatives. To do so, GPX4 uses the reducing power of glutathione (GSH) or other small cellular thiols [ 2 , 3 , 4 , 5 ], which explains why inhibition of GPX4 or deprivation of GSH or cysteine are the most frequently reported conditions triggering ferroptosis [ 1 , 4 , 6 , 7 , 8 ].…”

“…The extensive body of literature accumulated over the last decade unequivocally indicates the great potential of ferroptosis as a strategy for the eradication of tumor cells. During this period, our team, focusing primarily on highly aggressive pancreatic ductal adenocarcinoma (PDAC), has dissected in detail the pivotal antioxidant axis: cysteine-GSH-GPX4, used by cancer cells to forestall ferroptosis [ 4 , 8 , 9 , 10 , 11 , 12 ]. Our work and that of others have shown that the most potent and effective way to induce ferroptosis in PDAC and other types of cancers is either to block cysteine import into the cell, by inhibiting the membrane transporter known as xCT or to block the activity of GPX4 enzyme (reviewed in [ 13 ]).…”