Caspase-dependent generation of reactive oxygen species in human astrocytoma cells contributes to resistance to TRAIL-mediated apoptosis

Abstract

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF family of cytokines, causes apoptosis by caspase activation in various cell types, particularly in transformed cells. Numerous types of tumors are relatively resistant to TRAIL-induced cytotoxicity; however, the reasons for this are not yet fully understood. We report here a new signal transduction pathway involving protein kinase Cd (PKCd), NADPH oxidase 4 (NOX4) and reactive oxygen species (ROS), that inhibits caspase-dependent cell death induced by TRAIL ligation in human malignant astrocytoma cells. In our experiments, TRAIL ligation-induced generation of intracellular ROS through caspase-dependent proteolytic activation of PKCd and subsequent activation of the NOX4 complex. Suppression of intracellular ROS induction using various pharmacological inhibitors or PKCd-or NOX4-specific RNA interference enhanced the enzymatic activity of caspase-3 by blocking the oxidative modification of its catalytic cysteine residue, resulting in marked augmentation of TRAIL-mediated cell death. These results collectively indicate that TRAIL-induced activation of PKCd and NOX4 can modulate TRAIL-mediated apoptosis by promoting oxidative modification of active caspase-3 in a negative-feedback manner. Along with other members of the tumor necrosis factor (TNF) family of cytokines, TNF-related apoptosis-inducing ligand (TRAIL) transduces apoptotic signals through direct protein-protein interactions, such as those between caspases and adapter proteins such as Fas-associated protein with death domain (FADD). Although TRAIL is of interest to oncologists and cancer biologists because it is more cytotoxic to transformed cells than to their normal counterparts, numerous types of malignancies are reported to be resistant to TRAIL-induced toxicity. The postulated molecular mechanisms underlying this resistance to death-receptor signaling include downregulation of agonistic receptors, overexpression of decoy receptors, lack of deathinducing machinery, and abundance of endogenous inhibitors of apoptosis. [1][2][3][4] TRAIL has recently been shown to induce not only caspasedependent apoptosis but also the expression of pro-inflammatory genes such as CXCL8. 5 TRAIL-induced expression of CXCL8 is also mediated by upstream caspase-8 and the subsequent activation of the transcription factors NF-kB and AP-1. 5 Resistance of cells to death receptor-mediated cell death might enhance their ability to transduce proliferative and pro-inflammatory responses. 6 Therefore, it is important to delineate the molecular mechanisms responsible for relative resistance to TRAIL-mediated apoptotic processes.Reactive oxygen species (ROS), such as superoxide anions, H 2 O 2 , and hydroxyl radicals, are generated by the mitochondrial electron-transport chain during normal cellular respiration. Under normal conditions, antioxidant defense systems involving catalase, superoxide dismutase, and glutathione peroxidase regulate intracellular ROS levels to maintain physiological hom...

Peroxiredoxin 6 interferes with TRAIL-induced death-inducing signaling complex formation by binding to death effector domain caspase

“…Previous studies demonstrated that TRAIL treatment triggers the production of reactive oxygen species (ROS), resulting in intracellular oxidizing conditions. 31 Interestingly, we observed that in vitro binding of Prx6 to caspase-10 was decreased by increased ROS level with the treatment of hydrogen peroxide, but was increased by decreased ROS level with the treatment of ROS scavenger, dithiothreiton (DTT) (Supplementary Figure 3). Thus, we propose a hypothesis that cytosolic accumulation of ROS also may reduce the binding affinity of Prx6 to DED caspase and enhance the chances of FADD to interact with DED caspases to form DISC.…”

Bortezomib and SAHA Synergistically Induce ROS-Driven Caspase-Dependent Apoptosis of Nasopharyngeal Carcinoma and Block Replication of Epstein–Barr Virus

“…The ROS generation likely played a critical role in the induction of apoptosis of NPC cells because NAC, a ROS scavenger, could markedly reduce the sub-G 1 cell populations, in line with previously reported function of ROS generation in various cancer cell types upon treatment with bortezomib/SAHA (13)(14)(15)(16)19). We sought to clarify the relationship between ROS generation and caspase-dependent apoptosis in the NPC cells as conflicting data on the link between ROS generation and caspase activation have been reported in the literature (33,34). Our data showed that ROS generation resulted in caspase activation and subsequent apoptosis of NPC cells because NAC effectively reduced caspase activation, whereas Z-VAD-FMK failed to reduce ROS production.…”

Proteasome inhibitor sensitizes oral squamous cell carcinoma cells to TRAIL-mediated apoptosis

“…We demonstrated that treatment of OSCC cells with a proteasome inhibitor significantly enhanced TRAIL-mediated apoptosis. Molecules involved in TRAIL-mediated apoptosis that are regulated by the ubiquitin-proteasome pathway include members of the death receptor, Bcl-2 (28,29), and IAP families (30,31), and inhibitors of κB (IκB) (23,32). Furthermore, proteasome inhibitors can also decrease c-FLIP protein levels in cells, resulting in induced apoptosis signaling caused by increased caspase-8 activation (33)(34)(35)(36).…”