Project description:To seek ferroptosis related genes in liver cancer cells, we treated HepG2 cells using ferroptosis inducer Erastin and inhibitor Ferrostatin, respectively. We found that a subset of genes were up-regulated in Erastin treatment groups and down-regulated in Ferrostatin treatment groups, suggesting that these genes might be correlated with ferroptosis.
Project description:Ferroptosis is a unique form of intracellular iron-dependent cell death that differs from apoptosis, necrosis, and autophagy. GPX4, an antioxidant defense enzyme, plays a pivotal role as regulator of ferroptosis. Extensive researches suggest that targeting GPX4 holds promise for cancer therapy. However, the current GPX4 inhibitors face challenges due to unfavorable drug-like properties, which hinder their progress in clinical development. In this study, we identified a novel inhibitor called MI-2, demonstrating potent ferroptosis-inducing capacity. Mechanistically, MI-2 effectively inhibits the activity of GPX4 by direct interaction. Furthermore, MI-2 promotes the degradation of GPX4 through its well-established target, MALT1. In multiple cancer models, MI-2 has demonstrated synergistic effects when combined with sorafenib or regorafenib, resulting in enhanced ferroptosis induction. These findings highlight the dual modulatory effects of MI-2 on GPX4 activity and stability, offering a promising starting point for the development of drug-like GPX4 inhibitors with translational potential.
Project description:Ferroptosis is a form of regulated cell death driven by the iron-dependent accumulation of oxidized polyunsaturated-fatty-acid-containing phospholipids (PUFA-PLs). Three key molecular features of ferroptosis are peroxidation of PUFA-PLs, accumulation of redox-active ferrous iron, and defective lipid peroxide repair (Dixon and Stockwell, 2019). However, there is currently no reliable way to selectively stain ferroptotic cells in tissue sections to characterize the extent of ferroptosis in animal models of disease and in patient tissue samples. We sought to address this gap by immunizing mice with membranes from lymphoma cells treated with the ferroptosis inducer piperazine erastin (PE), and screening ~4,750 of the resulting monoclonal antibodies generated for their ability to selectively detect cells undergoing ferroptosis. We found that one antibody, termed 3F3 Ferroptotic Membrane Antibody (3F3-FMA), was effective as a selective ferroptosis-staining reagent using immunofluorescence (IF). The antigen of 3F3-FMA was identified by immunoprecipitation and mass spectrometry as the human transferrin receptor 1 protein (TfR1), which imports iron from the extracellular environment into cells. We validated this finding with several additional anti-TfR1 antibodies, and compared them to other potential ferroptosis-detecting reagents via immunofluorescence staining, using fluorescence microscopy and flow cytometry. We found that anti-TfR1 and anti-malondialdehyde (MDA) adduct antibodies were effective at reliably staining ferroptotic tumor cells in numerous cell culture and tissue contexts. In summary, these findings suggest that anti-TfR1 antibodies can be used to selectively label cells undergoing ferroptosis.
Project description:Ferroptosis, a non-apoptotic programmed cell death triggered by excessive iron-dependent lipid peroxidation, plays a pivotal role in tumor progression. Significant progress has been made in elucidating the role of transcription factors in the regulation of ferroptosis. Nevertheless, the identification of the key transcription factor responsible for inducing ferroptosis remains elusive. In this study, we discovered that ATOH8 is upregulated in prostate cancer cells treated with the ferroptosis inducer. Overexpression of ATOH8 increased the vulnerability of prostate cancer to ferroptosis, while ATOH8 deletion promotes ferroptosis evasion. Mechanistically, ATOH8 suppresses the transcription of SCD, reducing the synthesis of monounsaturated fatty acids that confer resistance to ferroptosis. Additionally, ATOH8 works in conjunction with the E protein E47 to form a transcriptional repression complex that inhibits SCD transcription. Furthermore, we discovered that EZH2 epigenetically suppresses the expression of ATOH8 through DNA methylation and H3K27 methylation. Interestingly, EZH2 was found to be downregulated in ferroptosis, resulting in an upregulation of ATOH8. Pharmacological inhibition of EZH2 combined with ferroptosis inducer significantly suppresses prostate cancer growth in vitro and in vivo. Together, our findings unveil that EZH2-mediated ATOH8 downregulation promotes ferroptosis evasion and suggest that pharmacological manipulation of EZH2 and ATOH8 is a promising therapeutic strategy for prostate cancer.
Project description:Ferroptosis, a non-apoptotic programmed cell death triggered by excessive iron-dependent lipid peroxidation, plays a pivotal role in tumor progression. Significant progress has been made in elucidating the role of transcription factors in the regulation of ferroptosis. Nevertheless, the identification of the key transcription factor responsible for inducing ferroptosis remains elusive. In this study, we discovered that ATOH8 is upregulated in prostate cancer cells treated with the ferroptosis inducer. Overexpression of ATOH8 increased the vulnerability of prostate cancer to ferroptosis, while ATOH8 deletion promotes ferroptosis evasion. Mechanistically, ATOH8 suppresses the transcription of SCD, reducing the synthesis of monounsaturated fatty acids that confer resistance to ferroptosis. Additionally, ATOH8 works in conjunction with the E protein E47 to form a transcriptional repression complex that inhibits SCD transcription. Furthermore, we discovered that EZH2 epigenetically suppresses the expression of ATOH8 through DNA methylation and H3K27 methylation. Interestingly, EZH2 was found to be downregulated in ferroptosis, resulting in an upregulation of ATOH8. Pharmacological inhibition of EZH2 combined with ferroptosis inducer significantly suppresses prostate cancer growth in vitro and in vivo. Together, our findings unveil that EZH2-mediated ATOH8 downregulation promotes ferroptosis evasion and suggest that pharmacological manipulation of EZH2 and ATOH8 is a promising therapeutic strategy for prostate cancer.
Project description:Despite the remarkable success of programmed death 1/PD-L1 inhibition in tumor therapy, only a minority of patients benefits from it. Previous studies suggest the anti-PD-1 treatment failure may attribute to the intrinsic functions of PD-L1 in cancer cells. Here, we established a genome-wide CRISPR synthetic lethality screen to systematic explore the PD-L1 intrinsic function in head and neck squamous cell carcinoma (HNSCC) cells. Ferroptosis related genes were identified to be essential for PD-L1 deficient cell viability. Genetic and pharmacological induction of ferroptosis accelerated cell death in PD-L1 knockout cells. PD-L1 knockout cells were also highly susceptible to immunogenic ferroptosis in vitro and in vivo. Mechanistically, nuclear PD-L1 transcriptionally activated SOD2 expression to maintain redox homeostasis. Importantly, the lower ROS and ferroptosis were observed in HNSCC patients with the higher expression of PD-L1. In summary, our study illustrates that PD-L1 confers ferroptosis resistance by activating SOD2-meidated redox homeostasis in HNSCC cells, indicating an enhanced therapeutic effect can be achieved by targeting the intrinsic PD-L1 function during immunotherapy.
Project description:Despite the remarkable success of programmed death 1/PD-L1 inhibition in tumor therapy, only a minority of patients benefits from it. Previous studies suggest the anti-PD-1 treatment failure may attribute to the intrinsic functions of PD-L1 in cancer cells. Here, we established a genome-wide CRISPR synthetic lethality screen to systematic explore the PD-L1 intrinsic function in head and neck squamous cell carcinoma (HNSCC) cells. Ferroptosis related genes were identified to be essential for PD-L1 deficient cell viability. Genetic and pharmacological induction of ferroptosis accelerated cell death in PD-L1 knockout cells. PD-L1 knockout cells were also highly susceptible to immunogenic ferroptosis in vitro and in vivo. Mechanistically, nuclear PD-L1 transcriptionally activated SOD2 expression to maintain redox homeostasis. Importantly, the lower ROS and ferroptosis were observed in HNSCC patients with the higher expression of PD-L1. In summary, our study illustrates that PD-L1 confers ferroptosis resistance by activating SOD2-meidated redox homeostasis in HNSCC cells, indicating an enhanced therapeutic effect can be achieved by targeting the intrinsic PD-L1 function during immunotherapy.
Project description:Ferroptosis is a form of regulated cell death driven by lipid peroxidation of polyunsaturated fatty acids (PUFAs). Endogenous PUFAs are nonconjugated PUFAs and their peroxidation proceeds via the hydrogen-atom transfer (HAT) mechanism. We previously reported that lipids with conjugated double bonds undergo lipid peroxidation mostly via a different mechanism, peroxyl radical addition (PRA), and were much more readily oxidizable than nonconjugated ones. In this study, we aim to elucidate the effects of various unsaturated lipids in sensitizing ferroptosis. We found that while some peroxidation-reactive lipids, such as 7-dehydrocholesterol, vitamins D3 and A, and coenzyme Q10, suppress ferroptosis, both nonconjugated and conjugated PUFAs enhanced cell death induced by RSL3, a ferroptosis inducer. Importantly, we showed that conjugated linolenic acid (CLA 18:3) could act as a ferroptosis inducer by itself and conjugated linoleic acid (CLA 18:2) was more potent in sensitizing cells to RSL3-induced cell death than any nonconjugated PUFAs. We next sought to elucidate the mechanism underlying the different ferroptosis-inducing potency of conjugated and nonconjugated PUFAs. Lipidomics revealed that conjugated and nonconjugated PUFAs are incorporated into distinct cellular lipid species. Furthermore, the different peroxidation mechanisms predict the formation of higher levels of reactive electrophilic aldehydes from conjugated PUFAs than nonconjugated PUFAs, which was confirmed by aldehyde-trapping and mass spectrometry. RNA sequencing revealed that protein processing in the endoplasmic reticulum and proteasome are among the most significantly upregulated pathways in cells treated with CLA 18:3, suggesting increased ER stress and activation of unfolded protein response. Significantly, using click chemistry, we observed increased protein adduction by oxidized lipids in cells treated with an alkynylated CLA 18:2 probe. These results suggest that protein damage by lipid electrophiles is a key step in ferroptosis.