Abstract
Although ferroptosis has been recognized as a novel antitumoral treatment, high expression of nuclear factor erythroid 2-related factor 2 (NRF2) has been reported to be an antioxidant transcript factor that protects malignant cells from ferroptosis. Previous findings indicated that metallothionein 1D pseudogene (MT1DP), a long noncoding RNA (lncRNA), functioned to aggravate oxidative stress by repressing antioxidation. Here we aimed at assessing whether MT1DP could regulate erastin-induced ferroptosis on non-small cell lung cancer (NSCLC) and elucidating the mechanism. We found that ectopic expression of MT1DP sensitized A549 and H1299 cells to erastin-induced ferroptosis through downregulation of NRF2; in addition, ectopic MT1DP upregulated malondialdehyde (MDA) and reactive oxygen species (ROS) levels, increased intracellular ferrous iron concentration, and reduced glutathione (GSH) levels in cancer cells exposed to erastin, whereas downregulation of MT1DP showed the opposite effect. RNA pulldown assay and dual-luciferase reporter assay confirmed that MT1DP modulated the expression of NRF2 via stabilizing miR-365a-3p. As low solubility of erastin limits its efficient application, we further prepared folate (FA)-modified liposome (FA-LP) nanoparticles for targeted co-delivery of erastin and MT1DP to enhance the bioavailability and the efficiency of the drug/gene combination. Erastin/MT1DP@FA-LPs (E/M@FA-LPs) sensitized erastin-induced ferroptosis with decreased cellular GSH levels and elevated lipid ROS. In vivo analysis showed that E/M@FA-LPs had a favorable therapeutic effect on lung cancer xenografts. In short, our findings identify a novel strategy to elevate erastin-induced ferroptosis in NSCLCs acting through the MT1DP/miR-365a-3p/NRF2 axis.
Highlights
Ferroptosis, which is a novel subtype of cell death different from other types of cell death both morphologically and biochemically[1,2], is characterized by depletion of glutathione (GSH) and overgeneration of lipid reactiveErastin has been identified as a prototype of recently discovered Ras-selective ferroptotic compounds[4]; previous studies confirmed that a variety of tumor cells were insensitive to erastin5. nuclear factor erythroid2-related factor 2 (NRF2) has been reported to be an important transcription factor that protects malignant cells from oxidative stress, chemotherapeutic agents, and facilitates cancer progression[6,7]
Our previous studies have demonstrated that A549 and H1299 cells are insensitive to ferroptosis induced by erastin[17], so we tested the effect of erastin on metallothionein 1D pseudogene (MT1DP) expression
We found that downregulation of nuclear factor erythroid 2-related factor 2 (NRF2) contributed to decrease significantly the viability of A549 and H1299 cells treated with erastin; overexpression of NRF2 rescued erastin-induced ferroptosis
Summary
2-related factor 2 (NRF2) has been reported to be an important transcription factor that protects malignant cells from oxidative stress, chemotherapeutic agents, and facilitates cancer progression[6,7]. Suppression of NRF2 contributed to an increased oxidative stress level and accelerated ferroptosis[8,9]. LncRNAs have been found to act as part of the cellular antioxidant system that orchestrates signaling pathways to fine-tune cell survival and death in response to external stresses[10,11]. Previous findings indicated that an lncRNA, metallothionein 1D pseudogene (MT1DP), functioned to aggravate oxidative stress by repressing NRF2-mediated antioxidation[12,13]. We confirmed that MT1DP attenuated expression of NRF2 and increased sensitivity of NRF2-overexpressed non-small cell lung cancer (NSCLC) cells to erastininduced ferroptosis via stabilizing miR-365a-3p. In vitro and in vivo experiments indicated that E/M@FA-LPs displayed strong killing effects on tumor cells
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