Increased Expression of System xc- in Glioblastoma Confers an Altered Metabolic State and Temozolomide Resistance

The amino acid transporter SLC7A11 expression in breast cancer

Breast cancer (BC), characterized by its diverse molecular profiles and clinical outcomes, presents a significant challenge in the development of effective therapeutic strategies. Metabolic reprogramming, a defining characteristic of cancer, has emerged as a promising target for novel therapies. SLC7A11, an amino acid transporter that facilitates cysteine uptake in exchange for glutamate, plays a crucial role in sustaining the altered metabolism of cancer cells. This study delves into the comprehensive analysis of SLC7A11 at the genomic, transcriptomic, and protein levels in extensive BC datasets to elucidate its potential role in different BC subtypes. SLC7A11 gene copy number and mRNA expression were evaluated using the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort (n = 1,980) and Breast Cancer Gene Expression Miner (n = 4,712). SLC7A11 protein was assessed using immunohistochemistry in a large BC cohort (n = 1,981). Additionally, The Cancer Genome Atlas (TCGA) dataset was used to explore SLC7A11 DNA methylation patterns using MethSurv (n = 782) and association of SLC7A11 mRNA expression with immune infiltrates using TIMER (n = 1,100). High SLC7A11 mRNA and SLC7A11 protein expression were significantly associated with high tumor grade (p ≤ .02), indicating a potential role in cancer progression. Interestingly, SLC7A11 copy number gain was observed in HER2+ tumors (p = .01), suggesting a subtype-specific association. In contrast, SLC7A11 mRNA expression was higher in the basal-like/triple-negative (TN; p < .001) and luminal B tumors (p = .02), highlighting its differential expression across BC subtypes. Notably, high SLC7A11 protein expression was predominantly observed in Estrogen Receptor (ER)-negative and Triple Negative (TN) BC, suggesting a role in these aggressive subtypes. Further analysis revealed that SLC7A11 was positively correlated with other amino acid transporters and enzymes associated with glutamine metabolism, implying a coordinated role in metabolic regulation. Additionally, SLC7A11 gene expression was positively associated with neutrophil and macrophage infiltration, suggesting a potential link between SLC7A11 and tumor immunity. Our findings suggest that SLC7A11 plays a significant role in BC metabolism, demonstrating differential expression across subtypes and associations with poor patient outcomes. Further functional studies are warranted to elucidate the precise mechanisms by which SLC7A11 contributes to BC progression and to explore its potential as a therapeutic target.

From bedside to bench: New insights in epilepsy-associated tumors based on recent classification updates and animal models on brain tumor networks

Low-grade neuroepithelial tumors (LGNTs), particularly those with glioneuronal histology, are highly associated with pharmacoresistant epilepsy. Increasing research focused on these neoplastic lesions did not translate into drug discovery; and anticonvulsant or antitumor therapies are not available yet. During the last years, animal modeling has improved, thereby leading to the possibility of generating brain tumors in mice mimicking crucial genetic, molecular and immunohistological features. Among them, intraventricular in utero electroporation (IUE) has been proven to be a valuable tool for the generation of animal models for LGNTs allowing endogenous tumor growth within the mouse brain parenchyma. Epileptogenicity is mostly determined by the slow-growing patterns of these tumors, thus mirroring intrinsic interactions between tumor cells and surrounding neurons is crucial to investigate the mechanisms underlying convulsive activity. In this review, we provide an updated classification of the human LGNT and summarize the most recent data from human and animal models, with a focus on the crosstalk between brain tumors and neuronal function.

Disrupted glutamate homeostasis as a target for glioma therapy

Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). Gliomas, malignant brain tumors with a dismal prognosis, alter glutamate homeostasis in the brain, which is advantageous for their growth, survival, and invasion. Alterations in glutamate homeostasis result from its excessive production and release to the extracellular space. High glutamate concentration in the tumor microenvironment destroys healthy tissue surrounding the tumor, thus providing space for glioma cells to expand. Moreover, it confers neuron hyperexcitability, leading to epilepsy, a common symptom in glioma patients. This mini-review briefly describes the biochemistry of glutamate production and transport in gliomas as well as the activation of glutamate receptors. It also summarizes the current pre-clinical and clinical studies identifying pharmacotherapeutics targeting glutamate transporters and receptors emerging as potential therapeutic strategies for glioma.

Ferroptosis in Cancer: Epigenetic Control and Therapeutic Opportunities

Ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, has emerged as a critical pathway in cancer biology. This review delves into the epigenetic mechanisms that modulate ferroptosis in cancer cells, focusing on how DNA methylation, histone modifications, and non-coding RNAs influence the expression and function of essential genes involved in this process. By unraveling the complex interplay between these epigenetic mechanisms and ferroptosis, the article sheds light on novel gene targets and functional insights that could pave the way for innovative cancer treatments to enhance therapeutic efficacy and overcome resistance in cancer therapy.

Oncogenic accumulation of cysteine promotes cancer cell proliferation by regulating the translation of D-type cyclins

Malignant cells exhibit a high demand for amino acids to sustain their abnormal proliferation. Particularly, the intracellular accumulation of cysteine is often observed in cancer cells. Previous studies have shown that deprivation of intracellular cysteine in cancer cells results in the accumulation of lipid peroxides in the plasma membrane and induction of ferroptotic cell death, indicating that cysteine plays a critical role in the suppression of ferroptosis. Herein, we found that the oncogenic accumulation of cysteine also contributes to cancer cell proliferation by promoting the cell cycle progression, which is independent of its suppressive effect on ferroptosis. The growth ability of four types of cancer cells, including murine hepatocarcinoma cells, but not of primary hepatocytes, were dependent on the exogenous supply of cysteine. Deprivation of intracellular cysteine in cancer cells induced cell cycle arrest at the G0/G1 phase, accompanied by a decrease in the expression of cyclin D1 and D2 proteins. The cysteine deprivation-induced decrease in D-type cyclin expression was associated with the upregulation of eukaryotic translation initiation factor 4E binding protein 1, which represses the translation of cyclin D1 and D2 proteins by binding to eukaryotic translation initiation factor 4E. Similar results were observed in hepatocarcinoma cells treated with erastin, an inhibitor of cystine/glutamate antiporter, xCT. These findings reveal an unappreciated role of cysteine in regulating the growth of malignant cancer cells and deepen our understanding of the cytotoxic effect of xCT inhibitor to prevent cancer cell proliferation.

Mechanism of ferroptosis regulating ischemic stroke and pharmacologically inhibiting ferroptosis in treatment of ischemic stroke

Ferroptosis is a newly discovered form of programmed cell death that is non-caspase-dependent and is characterized by the production of lethal levels of iron-dependent lipid reactive oxygen species (ROS). In recent years, ferroptosis has attracted great interest in the field of cerebral infarction because it differs morphologically, physiologically, and genetically from other forms of cell death such as necrosis, apoptosis, autophagy, and pyroptosis. In addition, ROS is considered to be an important prognostic factor for ischemic stroke, making it a promising target for stroke treatment. This paper summarizes the induction and defense mechanisms associated with ferroptosis, and explores potential treatment strategies for ischemic stroke in order to lay the groundwork for the development of new neuroprotective drugs.

Disulfidptosis, A Novel Cell Death Pathway: Molecular Landscape and Therapeutic Implications

Programmed cell death is pivotal for several physiological processes, including immune defense. Further, it has been implicated in the pathogenesis of developmental disorders and the onset of numerous diseases. Multiple modes of programmed cell death, including apoptosis, pyroptosis, necroptosis, and ferroptosis, have been identified, each with their own unique characteristics and biological implications. In February 2023, Liu Xiaoguang and his team discovered "disulfidptosis," a novel pathway of programmed cell death. Their findings demonstrated that disulfidptosis is triggered in glucose-starved cells exhibiting high expression of a protein called SLC7A11. Furthermore, disulfidptosis is marked by a drastic imbalance in the NADPH/NADP+ ratio and the abnormal accumulation of disulfides like cystine. These changes ultimately lead to the destabilization of the F-actin network, causing cell death. Given that high SLC7A11 expression is a key feature of certain cancers, these findings indicate that disulfidptosis could serve as the basis of innovative anti-cancer therapies. Hence, this review delves into the discovery of disulfidptosis, its underlying molecular mechanisms and metabolic regulation, and its prospective applications in disease treatment.

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Deciphering Ferroptosis: From Molecular Pathways to Machine Learning-Guided Therapeutic Innovation

Ferroptosis is a unique form of cell death reliant on iron and lipid peroxidation. It disrupts redox balance, causing cell death by damaging the plasma membrane, with inducers acting through enzymatic pathways or transport systems. In cancer treatment, suppressing ferroptosis or circumventing it holds significant promise. Beyond cancer, ferroptosis affects aging, organs, metabolism, and nervous system. Understanding ferroptosis mechanisms holds promise for uncovering novel therapeutic strategies across a spectrum of diseases. However, detection and regulation of this regulated cell death are still mired with challenges. The dearth of cell, tissue, or organ-specific biomarkers muted the pharmacological use of ferroptosis. This review covers recent studies on ferroptosis, detailing its properties, key genes, metabolic pathways, and regulatory networks, emphasizing the interaction between cellular signaling and ferroptotic cell death. It also summarizes recent findings on ferroptosis inducers, inhibitors, and regulators, highlighting their potential therapeutic applications across diseases. The review addresses challenges in utilizing ferroptosis therapeutically and explores the use of machine learning to uncover complex patterns in ferroptosis-related data, aiding in the discovery of biomarkers, predictive models, and therapeutic targets. Finally, it discusses emerging research areas and the importance of continued investigation to harness the full therapeutic potential of targeting ferroptosis.

Exploring Amino Acid Transporters as Therapeutic Targets for Cancer: An Examination of Inhibitor Structures, Selectivity Issues, and Discovery Approaches

Amino acid transporters are abundant amongst the solute carrier family and have an important role in facilitating the transfer of amino acids across cell membranes. Because of their impact on cell nutrient distribution, they also appear to have an important role in the growth and development of cancer. Naturally, this has made amino acid transporters a novel target of interest for the development of new anticancer drugs. Many attempts have been made to develop inhibitors of amino acid transporters to slow down cancer cell growth, and some have even reached clinical trials. The purpose of this review is to help organize the available information on the efforts to discover amino acid transporter inhibitors by focusing on the amino acid transporters ASCT2 (SLC1A5), LAT1 (SLC7A5), xCT (SLC7A11), SNAT1 (SLC38A1), SNAT2 (SLC38A2), and PAT1 (SLC36A1). We discuss the function of the transporters, their implication in cancer, their known inhibitors, issues regarding selective inhibitors, and the efforts and strategies of discovering inhibitors. The goal is to encourage researchers to continue the search and development within the field of cancer treatment research targeting amino acid transporters.

Nanomedicine targeting ferroptosis to overcome anticancer therapeutic resistance

A potential reason for the failure of tumor therapies is treatment resistance. Resistance to chemotherapy, radiotherapy, and immunotherapy continues to be a major obstacle in clinic, resulting in tumor recurrence and metastasis. The major mechanisms of therapy resistance are inhibitions of cell deaths, like apoptosis and necrosis, through drug inactivation and excretion, repair of DNA damage, tumor heterogeneity, or changes in tumor microenvironment, etc. Recent studies have shown that ferroptosis play a major role in therapies resistance by inducing phospholipid peroxidation and iron-dependent cell death. Some ferroptosis inducers in combination with clinical treatment techniques have been used to enhance the effect in tumor therapy. Notably, versatile ferroptosis nanoinducers exhibit an extensive range of functions in reversing therapy resistance, including directly triggering ferroptosis and feedback regulation. Herein, we provide a detailed description of the design, mechanism, and therapeutic application of ferroptosis-mediated synergistic tumor therapeutics. We also discuss the prospect and challenge of nanomedicine in tumor therapy resistance by regulating ferroptosis and combination therapy.

Self-engineered binary nanoassembly enabling closed-loop glutathione depletion-amplified tumor ferroptosis

Ferroptosis has emerged as a promising target for anticancer treatment, comprising iron-dependent lipid peroxidation and excessive accumulation of reactive oxygen species. Given that glutathione (GSH) overproduced in tumor cells antagonizes the cellular oxidation system, the reduction of GSH production has been extensively explored to induce ferroptosis. However, reducing GSH production alone is insufficient to trigger an intense lipid peroxidation storm. It is highly desirable to achieve systemic GSH depletion through simultaneous production and consumption intervention. Herein, we propose a bidirectional blockage strategy for closed-loop GSH depletion-amplified tumor ferroptosis. Sorafenib (Sor) and gambogic acid (GA) were elaborately fabricated as a self-engineered carrier-free nanoassembly without any nanocarrier materials. The PEGylated dual-drug nanoassembly enables favorable co-delivery and tumor-specific release of Sor and GA. Notably, a closed-loop GSH depletion is observed as a result of a Sor-induced decrease in GSH production and GA-accelerated GSH consumption in vitro and in vivo. As expected, this uniquely engineered dual-drug nanoassembly demonstrates vigorous antitumor activity in 4T1 breast tumor-bearing mice. This study presents a novel nanotherapeutic modality for ferroptosis-driven cancer treatment.

Novel approaches targeting ferroptosis in treatment of glioma

Glioma is a malignant brain tumor with a high mortality rate; hence novel treatment approaches are being explored to improve patient outcomes. Ferroptosis, a newly described form of regulated cell death, is emerging as a potential therapeutic target in glioma. Ferroptosis is characterized by the accumulation of lipid peroxides due to a loss of intracellular antioxidant systems represented by the depletion of glutathione and decreased activity of glutathione peroxidase 4 (GPX4). Since glioma cells have a high demand for iron and lipid metabolism, modulation of ferroptosis may represent a promising therapeutic approach for this malignancy. Recent studies indicate that ferroptosis inducers like erastin and RSL3 display potent anticancer activity in a glioma model. In addition, therapeutic strategies, including GPX4 targeting, lipid metabolism modulation, inhibition of amino acid transporters, and ferroptosis targeting natural compounds, have shown positive results in preclinical studies. This review will provide an overview of the functions of ferroptosis in glioma and its potential as a suitable target for glioma therapy.

Glioblastomas: Hijacking Metabolism to Build a Flexible Shield for Therapy Resistance

Significance: Glioblastomas (GBMs) are among the most lethal tumors despite the almost exclusive localization to the brain. This is largely due to therapeutic resistance. Radiation and chemotherapy significantly increase the survival for GBM patients, however, GBMs always recur, and the median overall survival is just over a year. Proposed reasons for such intractable resistance to therapy are numerous and include tumor metabolism, in particular, the ability of tumor cells to reconfigure metabolic fluxes on demand (metabolic plasticity). Understanding how the hard-wired, oncogene-driven metabolic tendencies of GBMs intersect with flexible, context-induced metabolic rewiring promises to reveal novel approaches for combating therapy resistance. Recent Advances: Personalized genome-scale metabolic flux models have recently provided evidence that metabolic flexibility promotes radiation resistance in cancer and identified tumor redox metabolism as a major predictor for resistance to radiation therapy (RT). It was demonstrated that radioresistant tumors, including GBM, reroute metabolic fluxes to boost the levels of reducing factors of the cell, thus enhancing clearance of reactive oxygen species that are generated during RT and promoting survival. Critical Issues: The current body of knowledge from published studies strongly supports the notion that robust metabolic plasticity can act as a (flexible) shield against the cytotoxic effects of standard GBM therapies, thus driving therapy resistance. The limited understanding of the critical drivers of such metabolic plasticity hampers the rational design of effective combination therapies. Future Directions: Identifying and targeting regulators of metabolic plasticity, rather than specific metabolic pathways, in combination with standard-of-care treatments have the potential to improve therapeutic outcomes in GBM. Antioxid. Redox Signal. 39, 957-979.

Function of Long Noncoding RNAs in Glioma Progression and Treatment Based on the Wnt/β-Catenin and PI3K/AKT Signaling Pathways

Gliomas are a deadly primary malignant tumor of the central nervous system, with glioblastoma (GBM) representing the most aggressive type. The clinical prognosis of GBM patients remains bleak despite the availability of multiple options for therapy, which has needed us to explore new therapeutic methods to face the rapid progression, short survival, and therapy resistance of glioblastomas. As the Human Genome Project advances, long noncoding RNAs (lncRNAs) have attracted the attention of researchers and clinicians in cancer research. Numerous studies have found aberrant expression of signaling pathways in glioma cells. For example, lncRNAs not only play an integral role in the drug resistance process by regulating the Wnt/β-catenin or PI3K/Akt signaling but are also involved in a variety of malignant biological behaviors such as glioma proliferation, migration, invasion, and tumor apoptosis. Therefore, the present review systematically assesses the existing research evidence on the malignant progression and drug resistance of glioma, focusing on the critical role and potential function of lncRNAs in the Wnt/β-catenin and PI3K/Akt classical pathways to promote and encourage further research in this field.

Visualization of ferroptosis in brain diseases and ferroptosis-inducing nanomedicine for glioma

A remarkable body of new data establishes that many degenerative brain diseases and some acute injury situations in the brain may be associated with ferroptosis. In recent years, ferroptosis has also attracted great interest in the cancer research community, partly because it is a unique mode of cell death distinct from other forms and thus has great therapeutic potential for brain cancer. Glioblastoma is a highly aggressive and fatal human cancer, accounting for 60% of all primary brain tumors. Despite the development of various pharmacological and surgical modalities, the survival rates of high-grade gliomas have remained poor over the past few decades. Recent evidence has revealed that ferroptosis is involved in tumor initiation, progression, and metastasis, and manipulating ferroptosis could offer a novel strategy for glioma management. Nanoparticles have been exploited as multifunctional platforms that can cross the blood-brain barrier and deliver therapeutic agents to the brain to address the pressing need for accurate visualization of ferroptosis and glioma treatment. To create efficient and durable ferroptosis inducers, many researchers have engineered nanocomposites to induce a more effective ferroptosis for therapy. In this review, we present the mechanism of ferroptosis and outline the current strategies of imaging and nanotherapy of ferroptosis in brain diseases, especially glioma. We aim to provide up-to-date information on ferroptosis and emphasize the potential clinical implications of ferroptosis for glioma diagnosis and treatment. However, regulation of ferroptosis in vivo remains challenging due to a lack of compounds.

From signalling pathways to targeted therapies: unravelling glioblastoma's secrets and harnessing two decades of progress

Glioblastoma, a rare, and highly lethal form of brain cancer, poses significant challenges in terms of therapeutic resistance, and poor survival rates for both adult and paediatric patients alike. Despite advancements in brain cancer research driven by a technological revolution, translating our understanding of glioblastoma pathogenesis into improved clinical outcomes remains a critical unmet need. This review emphasises the intricate role of receptor tyrosine kinase signalling pathways, epigenetic mechanisms, and metabolic functions in glioblastoma tumourigenesis and therapeutic resistance. We also discuss the extensive efforts over the past two decades that have explored targeted therapies against these pathways. Emerging therapeutic approaches, such as antibody-toxin conjugates or CAR T cell therapies, offer potential by specifically targeting proteins on the glioblastoma cell surface. Combination strategies incorporating protein-targeted therapy and immune-based therapies demonstrate great promise for future clinical research. Moreover, gaining insights into the role of cell-of-origin in glioblastoma treatment response holds the potential to advance precision medicine approaches. Addressing these challenges is crucial to improving outcomes for glioblastoma patients and moving towards more effective precision therapies.

Recent Progress in Fluorescent Probes for Real-Time Monitoring of Glioblastoma

Treating glioblastoma (GBM) by resecting to a large extent can prolong a patient's survival by controlling the tumor cells, but excessive resection may produce postoperative complications by perturbing the brain structures. Therefore, various imaging procedures have been employed to successfully diagnose and resect with utmost caution and to protect vital structural or functional features. Fluorescence tagging is generally used as an intraoperative imaging technique in glioma cells in collaboration with other surgical tools such as MRI and navigation methods. However, the existing fluorescent probes may have several limitations, including poor selectivity, less photostability, false signals, and intraoperative re-administration when used in clinical and preclinical studies for glioma surgery. The involvement of smart fluorogenic materials, specifically fluorescent dyes, and biomarker-amended cell-penetrable fluorescent probes have noteworthy advantages for precise glioma imaging. This review outlines the contemporary advancements of fluorescent probes for imaging glioma cells along with their challenges and visions, with the anticipation to develop next-generation smart glioblastoma detection modalities.

Nucleotide metabolism is linked to cysteine availability

The small molecule erastin inhibits the cystine-glutamate antiporter, system x_c^-, which leads to intracellular cysteine and glutathione depletion. This can cause ferroptosis, which is an oxidative cell death process characterized by uncontrolled lipid peroxidation. Erastin and other ferroptosis inducers have been shown to affect metabolism but the metabolic effects of these drugs have not been systematically studied. To this end, we investigated how erastin impacts global metabolism in cultured cells and compared this metabolic profile to that caused by the ferroptosis inducer RAS-selective lethal 3 or in vivo cysteine deprivation. Common among the metabolic profiles were alterations in nucleotide and central carbon metabolism. Supplementing nucleosides to cysteine-deprived cells rescued cell proliferation in certain contexts, showing that these alterations to nucleotide metabolism can affect cellular fitness. While inhibition of the glutathione peroxidase GPX4 caused a similar metabolic profile as cysteine deprivation, nucleoside treatment did not rescue cell viability or proliferation under RAS-selective lethal 3 treatment, suggesting that these metabolic changes have varying importance in different scenarios of ferroptosis. Together, our study shows how global metabolism is affected during ferroptosis and points to nucleotide metabolism as an important target of cysteine deprivation.

Upstaging and Downstaging in Gliomas-Clinical Implications for the Fifth Edition of the World Health Organization Classification of Tumors of the Central Nervous System

In 2021, the 5th edition of the WHO Classification of Tumors of the Central Nervous System (WHO-CNS5) was published as the sixth volume of the international standard for brain and spinal cord tumor classification. The most remarkable practical change in the current classification involves grading gliomas according to molecular characterization. IDH mutant (10%) and IDH wild-type tumors (90%) are two different entities that possess unique biological features and various clinical outcomes regarding treatment response and overall survival. This article presents two comparative cases that highlight the clinical importance of these new classification standards. The first clinical case aimed to provide a comprehensive argument for determining the IDH status in tumors initially appearing as low-grade astrocytoma upon histologic examination, thus underlining the importance of the WHO-CNS5. The second case showed the implications of the histologic overdiagnosis of glioblastoma using the previous classification system with a treatment span of 7 years that proceeded through full-dose re-irradiation up to metronomic therapy. The new WHO-CNS5 classification significantly impacted complex neurooncological cases, thus changing the initial approach to a more precise therapeutic management.

The Role of Hyperexcitability in Gliomagenesis

Glioblastoma is the most common malignant primary brain tumor. Recent studies have demonstrated that excitatory or activity-dependent signaling-both synaptic and non-synaptic-contribute to the progression of glioblastoma. Glutamatergic receptors may be stimulated via neuron-tumor synapses or release of glutamate by the tumor itself. Ion currents generated by these receptors directly alter the structure of membrane adhesion molecules and cytoskeletal proteins to promote migratory behavior. Additionally, the hyperexcitable milieu surrounding glioma increases the rate at which tumor cells proliferate and drive recurrent disease. Inhibition of excitatory signaling has shown to effectively reduce its pro-migratory and -proliferative effects.

Expression and Prognostic Significance of Ferroptosis-related Proteins SLC7A11 and GPX4 in Renal Cell Carcinoma

BACKGROUND

The ferroptosis inhibitory gene solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) inhibit ferroptosis in carcinoma cells. However, whether SLC7A11 and GPX4 serve as an oncogene in renal cell carcinoma (RCC) remains unclear.

METHODS

Immunohistochemistry (IHC) assays were performed to assess the expression of SLC7A11 and GPX4 in human RCC tissues. Clinical-pathological analysis was performed to explore the correlation between SLC7A11 and GPX4 expression. Kaplan-Meier survival analysis was performed to characterise the associations between protein expression and patient progressionfree survival (PFS).

RESULTS

The upregulation of SLC7A11 and GPX4 was detected by IHC in RCC tissues compared with that in normal renal tissues. Meanwhile, the expression level of SLC7A11 and GPX4 was correlated with tumour diameter and distant metastasis (P<0.05). Kaplan-Meier survival analysis indicated that patients with high SLC7A11 and GPX4 expression levels exhibited worse PFS than those with low SLC7A11 and GPX4 expression levels (P<0.05).

CONCLUSION

The upregulation of SLC7A11 and GPX4 expression was associated with poor prognosis in patients with RCC. SLC7A11 and GPX4 may serve as diagnostic and prognostic biomarkers for patients with RCC.

Relationship between ferroptosis and mitophagy in cardiac ischemia reperfusion injury: a mini-review

Cardiovascular diseases (CVD), with high morbidity and mortality, seriously affect people's life and social development. Clinically, reperfusion therapy is typically used to treat ischemic cardiomyopathy, such as severe coronary heart disease and acute myocardial infarction. However, reperfusion therapy can lead to myocardial ischemia reperfusion injury (MIRI), which can affect the prognosis of patients. Studying the mechanisms of MIRI can help us improve the treatment of MIRI. The pathological process of MIRI involves many mechanisms such as ferroptosis and mitophagy. Ferroptosis can exacerbate MIRI, and regulation of mitophagy can alleviate MIRI. Both ferroptosis and mitophagy are closely related to ROS, but there is no clear understanding of the relationship between ferroptosis and mitophagy. In this review, we analyzed the relationship between ferroptosis and mitophagy according to the role of mTOR, NLPR3 and HIF. In addition, simultaneous regulation of mitophagy and ferroptosis may be superior to single therapy for MIRI. We summarized potential drugs that can regulate mitophagy and/or ferroptosis, hoping to provide reference for the development of drugs and methods for MIRI treatment.

The prognostic and clinicopathological significance of SLC7A11 in human cancers: a systematic review and meta-analysis

Objective

It is of great importance to recognize bio-markers for cancer prognosis. However, the association between solute carrier family 7 member 11 (SLC7A11) and prognosis is still controversial. Therefore, we conducted this systematic review and meta-analysis to identify the prognostic and clinicopathological significance of SLC7A11 in human cancers.

Methods

PubMed, Web of Science, Scopus, the Cochrane Library and Embase database were searched from database inceptions to March 19th 2022. Hand searches were also conducted in references. Prognosis and clinicopathological data were extracted and analyzed.

Results

A total of 12 eligible studies with 1,955 patients were included. The results indicated that SLC7A11 expression is associated with unfavorable overall survival (OS), unfavorable recurrence-free survival (RFS) and unfavorable progression free survival (PFS). And SLC7A11 expression is also associated with more advanced tumor stage.

Conclusions

SLC7A11 expression is associated with more unfavorable prognosis and more advanced tumor stage. Therefore, SLC7A11 could be a potential biomarker for human cancer prognosis.

New insights in ferroptosis: Potential therapeutic targets for the treatment of ischemic stroke

Stroke is a common disease in clinical practice, which seriously endangers people's physical and mental health. The neurovascular unit (NVU) plays a key role in the occurrence and development of ischemic stroke. Different from other classical types of cell death such as apoptosis, necrosis, autophagy, and pyroptosis, ferroptosis is an iron-dependent lipid peroxidation-driven new form of cell death. Interestingly, the function of NVU and stroke development can be regulated by activating or inhibiting ferroptosis. This review systematically describes the NVU in ischemic stroke, provides a comprehensive overview of the regulatory mechanisms and key regulators of ferroptosis, and uncovers the role of ferroptosis in the NVU and the progression of ischemic stroke. We further discuss the latest progress in the intervention of ferroptosis as a therapeutic target for ischemic stroke and summarize the research progress and regulatory mechanism of ferroptosis inhibitors on stroke. In conclusion, ferroptosis, as a new form of cell death, plays a key role in ischemic stroke and is expected to become a new therapeutic target for this disease.

High co-expression of SLC7A11 and GPX4 as a predictor of platinum resistance and poor prognosis in patients with epithelial ovarian cancer

OBJECTIVE

The aim was to assess the expression levels of SLC7A11 and GPX4 in relation to platinum resistance and prognosis in patients with epithelial ovarian cancer (EOC).

DESIGN

A retrospective cohort study.

SETTING

Women's Hospital, Zhejiang University School of Medicine, Hangzhou, China.

POPULATION OR SAMPLE

We included 192 eligible patients from hospital between January 2002 and December 2018.

METHODS

We retrospectively analysed the medical records of patients with EOC. Surgical specimens of EOC were stained for SLC7A11 and GPX4. Survival analysis was performed using the Kaplan-Meier and Cox regression methods.

MAIN OUTCOME MEASURES

Clinical end points include platinum-free interval (PFI), progression-free survival (PFS) and overall survival (OS).

RESULTS

Patients with high co-expression levels of SLC7A11 and GPX4 had a 60-fold higher risk of platinum resistance compared with those with low co-expression (risk ratio, 60.46; 95% confidence interval [CI] 22.76-160.58; p < 0.001). Moreover, high co-expression level of SLC7A11 and GPX4 was an independent prognostic factor for poor OS (p < 0.001, hazard ratio [HR] 4.44, 95% CI, 2.77-7.14) and poor PFS (p < 0.001, HR = 5.73, 95% CI, 3.86-8.73). For in vitro experiments, SLC7A11 and GPX4 expression were both upregulated in platinum-resistant cells compared with their parental ovarian cancer cells, and siRNA-induced SLC7A11 and GPX4 inhibition decreased platinum resistance.

CONCLUSIONS

High expression levels of SLC7A11 and GPX4 are associated with platinum resistance in EOC patients. High co-expression of SLC7A11 and GPX4 may be a significant independent prognostic factor and a potential therapeutic target for platinum resistance in EOC patients.

Ferroptosis and Its Potential Role in Glioma: From Molecular Mechanisms to Therapeutic Opportunities

Glioma is the most common intracranial malignant tumor, and the current main standard treatment option is a combination of tumor surgical resection, chemotherapy and radiotherapy. Due to the terribly poor five-year survival rate of patients with gliomas and the high recurrence rate of gliomas, some new and efficient therapeutic strategies are expected. Recently, ferroptosis, as a new form of cell death, has played a significant role in the treatment of gliomas. Specifically, studies have revealed key processes of ferroptosis, including iron overload in cells, occurrence of lipid peroxidation, inactivation of cysteine/glutathione antiporter system Xc- (xCT) and glutathione peroxidase 4 (GPX4). In the present review, we summarized the molecular mechanisms of ferroptosis and introduced the application and challenges of ferroptosis in the development and treatment of gliomas. Moreover, we highlighted the therapeutic opportunities of manipulating ferroptosis to improve glioma treatments, which may improve the clinical outcome.

Ferroptosis: A novel therapeutic strategy and mechanism of action in glioma

Glioma is the most common malignant tumor of the central nervous system and resistance is easily developed to chemotherapy drugs during the treatment process, resulting in high mortality and short survival in glioma patients. Novel therapeutic approaches are urgently needed to improve the therapeutic efficacy of chemotherapeutic drugs and to improve the prognosis of patients with glioma. Ferroptosis is a novel regulatory cell death mechanism that plays a key role in cancer, neurodegenerative diseases, and other diseases. Studies have found that ferroptosis-related regulators are closely related to the survival of patients with glioma, and induction of ferroptosis can improve glioma resistance to chemotherapy drugs. Therefore, induction of tumor cell ferroptosis may be an effective therapeutic strategy for glioma. This review summarizes the relevant mechanisms of ferroptosis, systematically summarizes the key role of ferroptosis in the treatment of glioma and outlines the relationship between ferroptosis-related ncRNAs and the progression of glioma.

Cancer suppression by ferroptosis and its role in digestive system tumors

Cancer is the second leading cause of death worldwide, and digestive system tumors remain the leading malignancy in China, seriously endangering national health and imposing a huge economic burden. Ferroptosis is a form of cell death characterized by increased intracellular reduced iron and accumulated lipid peroxide. Recent studies have revealed that ferroptosis is closely related to the occurrence and treatment of cancer. Therefore, this paper reviews the studies on ferroptosis and cancer to explore the potential of ferroptosis in the treatment of malignant tumors, especially digestive system tumors, and to provide a new direction for developing treatment options.

Emerging roles of ferroptosis in glioma

Glioma is the most common primary malignant tumor in the central nervous system, and directly affects the quality of life and cognitive function of patients. Ferroptosis, is a new form of regulated cell death characterized by iron-dependent lipid peroxidation. Ferroptosis is mainly due to redox imbalance and involves multiple intracellular biology processes, such as iron metabolism, lipid metabolism, and antioxidants synthesis. Induction of ferroptosis could be a new target for glioma treatment, and ferroptosis-related processes are associated with chemoresistance and radioresistance in glioma. In the present review, we provide the characteristics, key regulators and pathways of ferroptosis and the crosstalk between ferroptosis and other programmed cell death in glioma, we also proposed the application and prospect of ferroptosis in the treatment of glioma.

High levels of NRF2 sensitize temozolomide-resistant glioblastoma cells to ferroptosis via ABCC1/MRP1 upregulation

Glioblastoma patients have a poor prognosis mainly due to temozolomide (TMZ) resistance. NRF2 is an important transcript factor involved in chemotherapy resistance due to its protective role in the transcription of genes involved in cellular detoxification and prevention of cell death processes, such as ferroptosis. However, the relation between NRF2 and iron-dependent cell death in glioma is still poorly understood. Therefore, in this study, we analyzed the role of NRF2 in ferroptosis modulation in glioblastoma cells. Two human glioblastoma cell lines (U251MG and T98G) were examined after treatment with TMZ, ferroptosis inducers (Erastin, RSL3), and ferroptosis inhibitor (Ferrostatin-1). Our results demonstrated that T98G was more resistant to chemotherapy compared to U251MG and showed elevated levels of NRF2 expression. Interestingly, T98G revealed higher sensitivity to ferroptosis, and significant GSH depletion upon system xc^- blockage. NRF2 silencing in T98G cells (T98G-shNRF2) significantly reduced the viability upon TMZ treatment. On the other hand, T98G-shNRF2 was resistant to ferroptosis and reverted intracellular GSH levels, indicating that NRF2 plays a key role in ferroptosis induction through GSH modulation. Moreover, silencing of ABCC1, a well-known NRF2 target that diminishes GSH levels, has demonstrated a similar collateral sensitivity. T98G-siABCC1 cells were more sensitive to TMZ and resistant to Erastin. Furthermore, we found that NRF2 positively correlates with ABCC1 expression in tumor tissues of glioma patients, which can be associated with tumor aggressiveness, drug resistance, and poor overall survival. Altogether, our data indicate that high levels of NRF2 result in collateral sensitivity on glioblastoma via the expression of its pro-ferroptotic target ABCC1, which contributes to GSH depletion when the system xc^- is blocked by Erastin. Thus, ferroptosis induction could be an important therapeutic strategy to reverse drug resistance in gliomas with high NRF2 and ABCC1 expression.

Using AI-Based Evolutionary Algorithms to Elucidate Adult Brain Tumor (Glioma) Etiology Associated with IDH1 for Therapeutic Target Identification

Adult brain tumors (glioma) represent a cancer of unmet need where standard-of-care is non-curative; thus, new therapies are urgently needed. It is unclear whether isocitrate dehydrogenases (IDH1/2) when not mutated have any role in gliomagenesis or tumor growth. Nevertheless, IDH1 is overexpressed in glioblastoma (GBM), which could impact upon cellular metabolism and epigenetic reprogramming. This study characterizes IDH1 expression and associated genes and pathways. A novel biomarker discovery pipeline using artificial intelligence (evolutionary algorithms) was employed to analyze IDH-wildtype adult gliomas from the TCGA LGG-GBM cohort. Ninety genes whose expression correlated with IDH1 expression were identified from: (1) All gliomas, (2) primary GBM, and (3) recurrent GBM tumors. Genes were overrepresented in ubiquitin-mediated proteolysis, focal adhesion, mTOR signaling, and pyruvate metabolism pathways. Other non-enriched pathways included O-glycan biosynthesis, notch signaling, and signaling regulating stem cell pluripotency (PCGF3). Potential prognostic (TSPYL2, JAKMIP1, CIT, TMTC1) and two diagnostic (MINK1, PLEKHM3) biomarkers were downregulated in GBM. Their gene expression and methylation were negatively and positively correlated with IDH1 expression, respectively. Two diagnostic biomarkers (BZW1, RCF2) showed the opposite trend. Prognostic genes were not impacted by high frequencies of molecular alterations and only one (TMTC1) could be validated in another cohort. Genes with mechanistic links to IDH1 were involved in brain neuronal development, cell proliferation, cytokinesis, and O-mannosylation as well as tumor suppression and anaplerosis. Results highlight metabolic vulnerabilities and therapeutic targets for use in future clinical trials.

Redox-dependent AMPK inactivation disrupts metabolic adaptation to glucose starvation in xCT-overexpressing cancer cells

Accelerated aerobic glycolysis is a distinctive metabolic property of cancer cells that confers dependency on glucose for survival. However, the therapeutic strategies targeting this vulnerability are still inefficient and have unacceptable side effects in clinical trials. Therefore, developing biomarkers to predict therapeutic efficacy would be essential to improve the selective targeting of cancer cells. Here, we found that the cell lines sensitive to glucose deprivation have high expression of cystine/glutamate antiporter xCT. We found that cystine uptake and glutamate export through xCT contributed to rapid NADPH depletion under glucose deprivation. This collapse of the redox system oxidized and inactivated AMPK, a major regulator of metabolic adaptation, resulting in a metabolic catastrophe and cell death. While this phenomenon was prevented by pharmacological or genetic inhibition of xCT, overexpression of xCT sensitized resistant cancer cells to glucose deprivation. Taken together, these findings suggest a novel cross-talk between AMPK and xCT for the metabolism and signal transduction and reveal a metabolic vulnerability in xCT-high expressing cancer cells to glucose deprivation.

BH3 mimetic drugs cooperate with Temozolomide, JQ1 and inducers of ferroptosis in killing glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is the most common and aggressive form of brain cancer, with treatment options often constrained due to inherent resistance of malignant cells to conventional therapy. We investigated the impact of triggering programmed cell death (PCD) by using BH3 mimetic drugs in human GBM cell lines. We demonstrate that co-targeting the pro-survival proteins BCL-XL and MCL-1 was more potent at killing six GBM cell lines compared to conventional therapy with Temozolomide or the bromodomain inhibitor JQ1 in vitro. Enhanced cell killing was observed in U251 and SNB-19 cells in response to dual treatment with TMZ or JQ1 combined with a BCL-XL inhibitor, compared to single agent treatment. This was reflected in abundant cleavage/activation of caspase-3 and cleavage of PARP1, markers of apoptosis. U251 and SNB-19 cells were more readily killed by a combination of BH3 mimetics targeting BCL-XL and MCL-1 as opposed to dual treatment with the BCL-2 inhibitor Venetoclax and a BCL-XL inhibitor. The combined loss of BAX and BAK, the essential executioners of intrinsic apoptosis, rendered U251 and SNB-19 cells refractory to any of the drug combinations tested, demonstrating that apoptosis is responsible for their killing. In an orthotopic mouse model of GBM, we demonstrate that the BCL-XL inhibitor A1331852 can penetrate the brain, with A1331852 detected in both tumour and healthy brain regions. We also investigated the impact of combining small molecule inducers of ferroptosis, erastin and RSL3, with BH3 mimetic drugs. We found that a BCL-XL or an MCL-1 inhibitor potently cooperates with inducers of ferroptosis in killing U251 cells. Overall, these findings demonstrate the potential of dual targeting of distinct PCD signalling pathways in GBM and may guide the utility of BCL-XL inhibitors and inducers of ferroptosis with standard of care treatment for improved therapies for GBM.

Insights Into Ferroptosis, a Novel Target for the Therapy of Cancer

Ferroptosis is a new form of programmed cell death (PCD) characterized by an excess iron accumulation and subsequent unbalanced redox states. Ferroptosis is different from the already reported PCD and has unique morphological features and biochemical processes. Ferroptosis was first elaborated by Brent R. Stockwell’s lab in 2012, in which small molecules erastin and RSL-3 induce PCD in Ras mutant cell lines. Ferroptosis involves various physiological processes and occurrence of disease and especially shows strong potential in cancer treatment. Development of small molecule compounds based on Stockwell’s research was found to kill cancer cells, and some FDA-approved drugs were discovered to result in ferroptosis of cancer cells. Radiotherapy and checkpoint therapy have been widely used as a treatment for many types of cancer. Recently, some papers have reported that chemotherapy, radiotherapy, and checkpoint therapy induce ferroptosis of cancer cells, which provides new strategies for cancer treatment. Nevertheless, the limitless proliferation of tumor cells and the lack of cell death mechanisms are important reasons for drug resistance for tumor therapy. Therefore, we reviewed the molecular mechanism of ferroptosis and sensitivity to ferroptosis of different cancer cells and tumor treatment strategy.

The Role of Cystine/Glutamate Antiporter SLC7A11/xCT in the Pathophysiology of Cancer

SLC7A11/xCT is an antiporter that mediates the uptake of extracellular cystine in exchange for glutamate. Cystine is reduced to cysteine, which is a rate-limiting precursor in glutathione synthesis; a process that protects cells from oxidative stress and is, therefore, critical to cell growth, proliferation, and metabolism. SLC7A11 is expressed in different tissues and plays diverse functional roles in the pathophysiology of various diseases, including cancer, by regulating the processes of redox homeostasis, metabolic flexibility/nutrient dependency, immune system function, and ferroptosis. SLC7A11 expression is associated with poor prognosis and drug resistance in cancer and, therefore, represents an important therapeutic target. In this review, we discuss the molecular functions of SLC7A11 in normal versus diseased tissues, with a special focus on how it regulates gastrointestinal cancers. Further, we summarize current therapeutic strategies targeting SLC7A11 as well as novel avenues for treatment.

Ferroptosis Involvement in Glioblastoma Treatment

Glioblastoma multiforme (GBM) is one of the deadliest brain tumors. Current standard therapy includes tumor resection surgery followed by radiotherapy and chemotherapy. Due to the tumors invasive nature, recurrences are almost a certainty, giving the patients after diagnosis only a 12–15 months average survival time. Therefore, there is a dire need of finding new therapies that could potentially improve patient outcomes. Ferroptosis is a newly described form of cell death with several implications in cancer, among which GBM. Agents that target different molecules involved in ferroptosis and that stimulate this process have been described as potentially adjuvant anti-cancer treatment options. In GBM, ferroptosis stimulation inhibits tumor growth, improves patient survival, and increases the efficacy of radiation and chemotherapy. This review provides an overview of the current knowledge regarding ferroptosis modulation in GBM.

Amino Acid Metabolism in Cancer Drug Resistance

Despite the numerous investigations on resistance mechanisms, drug resistance in cancer therapies still limits favorable outcomes in cancer patients. The complexities of the inherent characteristics of tumors, such as tumor heterogeneity and the complicated interaction within the tumor microenvironment, still hinder efforts to overcome drug resistance in cancer cells, requiring innovative approaches. In this review, we describe recent studies offering evidence for the essential roles of amino acid metabolism in driving drug resistance in cancer cells. Amino acids support cancer cells in counteracting therapies by maintaining redox homeostasis, sustaining biosynthetic processes, regulating epigenetic modification, and providing metabolic intermediates for energy generation. In addition, amino acid metabolism impacts anticancer immune responses, creating an immunosuppressive or immunoeffective microenvironment. A comprehensive understanding of amino acid metabolism as it relates to therapeutic resistance mechanisms will improve anticancer therapeutic strategies.

A xCT role in tumour-associated ferroptosis shed light on novel therapeutic options

Solute carrier family 7 member 11 (SLC7A11; also known as xCT), a key component of the cystine/glutamate antiporter, is essential for the maintenance of cellular redox status and the regulation of tumor-associated ferroptosis. Accumulating evidence has demonstrated that xCT overexpression, resulting from different oncogenic and tumor suppressor signaling, promotes tumor progression and multidrug resistance partially via suppressing ferroptosis. In addition, recent studies have highlighted the role of xCT in regulating the metabolic flexibility in cancer cells. In this review, the xCT activities in intracellular redox balance and in ferroptotic cell death have been summarized. Moreover, the role of xCT in promoting tumor development, drug resistance, and nutrient dependency in cancer cells has been explored. Finally, different therapeutic strategies, xCT-based, for anti-cancer treatments have been discussed.

Wild-type isocitrate dehydrogenase under the spotlight in glioblastoma

Brain tumors actively reprogram their cellular metabolism to survive and proliferate, thus offering potential therapeutic opportunities. Over the past decade, extensive research has been done on mutant IDH enzymes as markers of good prognosis in glioblastoma, a highly aggressive brain tumor in adults with dismal prognosis. Yet, 95% of glioblastoma are IDH wild-type. Here, we review current knowledge about IDH wild-type enzymes and their putative role in mechanisms driving tumor progression. After a brief overview on tumor metabolic adaptation, we present the diverse metabolic function of IDH enzymes and their roles in glioblastoma initiation, progression and response to treatments. Finally, we will discuss wild-type IDH targeting in primary glioblastoma.

Reversing tozasertib resistance in glioma through inhibition of pyruvate dehydrogenase kinases

Acquired resistance to conventional chemotherapeutic agents limits their effectiveness and can cause cancer treatment to fail. Because enzymes in the aurora kinase family are vital regulators of several mitotic events, we reasoned that targeting these kinases with tozasertib, a pan-aurora kinase inhibitor, would not only cause cytokinesis defects, but also induce cell death in high-grade pediatric and adult glioma cell lines. We found that tozasertib induced cell cycle arrest, increased mitochondrial permeability and reactive oxygen species generation, inhibited cell growth and migration, and promoted cellular senescence and pro-apoptotic activity. However, sustained exposure to tozasertib at clinically relevant concentrations conferred resistance, which led us to examine the mechanistic basis for the emergence of drug resistance. RNA-sequence analysis revealed a significant upregulation of the gene encoding pyruvate dehydrogenase kinase isoenzyme 4 (PDK4), a pyruvate dehydrogenase (PDH) inhibitory kinase that plays a crucial role in the control of metabolic flexibility under various physiological conditions. Upregulation of PDK1, PDK2, PDK3, or PDK4 protein levels was positively correlated with tozasertib-induced resistance through inhibition of PDH activity. Tozasertib-resistant cells exhibited increased mitochondrial mass as measured by 10-N-nonyl-Acridine Orange. Inhibition of PDK with dichloroacetate resulted in increased mitochondrial permeability and cell death in tozasertib-resistant glioma cell lines. Based on these results, we believe that PDK is a selective target for the tozasertib resistance phenotype and should be considered for further preclinical evaluations.

Interleukin-6 facilitates tumor progression by inducing ferroptosis resistance in head and neck squamous cell carcinoma

Ferroptosis resistance is an important mechanism of tumor progression. Interleukin-6 (IL-6) is a representative inflammatory cytokine during chronic inflammation; however, our current understanding of its regulatory role of ferroptosis during carcinogenesis of head and neck squamous cell carcinoma is limited. Chromatin immunoprecipitation and functional observations were performed to investigate xCT-regulatory function of IL-6. We observed a gradual increase in lipid peroxide 4-hydroxynonenal and IL-6 levels during progression from normal oral mucosa to leukoplakia and HNSCC. Meanwhile, the expression of xCT, a key amino acid antiporter assisting ferroptosis resistance, was correlated with IL-6 levels. The upregulated expression of xCT in HNSCC is associated with poor prognosis. Silencing of xCT inhibited HNSCC cell proliferation in vitro and tumor growth in vivo, inducing ferroptosis. Mechanistically, IL-6 transcriptionally activates xCT expression through the JAK2/STAT3 pathway. Furthermore, IL-6 reversed ferroptosis and growth suppression that was induced by xCT knockdown or ferroptosis inducer erastin. Our results demonstrate the critical role of IL-6-induced ferroptosis resistance during HNSCC carcinogenesis. The IL-6/STAT3/xCT axis acts as a novel mechanism driving tumor progression and thus may potentially be utilized as a target for tumor prevention and therapy.

Molecular basis for redox control by the human cystine/glutamate antiporter system xc. Nat Commun 2021;12:7147. [PMID: 34880232 PMCID: PMC8654953 DOI: 10.1038/s41467-021-27414-1]

Cysteine plays an essential role in cellular redox homoeostasis as a key constituent of the tripeptide glutathione (GSH). A rate limiting step in cellular GSH synthesis is the availability of cysteine. However, circulating cysteine exists in the blood as the oxidised di-peptide cystine, requiring specialised transport systems for its import into the cell. System xc- is a dedicated cystine transporter, importing cystine in exchange for intracellular glutamate. To counteract elevated levels of reactive oxygen species in cancerous cells system xc- is frequently upregulated, making it an attractive target for anticancer therapies. However, the molecular basis for ligand recognition remains elusive, hampering efforts to specifically target this transport system. Here we present the cryo-EM structure of system xc- in both the apo and glutamate bound states. Structural comparisons reveal an allosteric mechanism for ligand discrimination, supported by molecular dynamics and cell-based assays, establishing a mechanism for cystine transport in human cells.

Transcriptional Regulation of Amino Acid Transport in Glioblastoma Multiforme

Simple Summary

Glioblastoma multiforme (GBM) is a highly invasive brain tumor that typically has poor patient outcomes. This is due in part to aggressive tumor expansion within the brain parenchyma. This process is aided by assiduous glutamate release via the System xc- (SXC) cystine–glutamate antiporter. SXC is over-expressed in roughly half of GBM tumors where it is responsible for glutamate-mediated neuronal cell death and provides excess glutamate to fuel tumor-associated epilepsy. Available pharmacological inhibitors have some promise, although they lack specificity and have poor bioavailability. Therefore, identifying regulators of SXC may provide a superior avenue to target GBM. In this study, we identify tumor protein 53 (TP53) as a molecular regulator of SXC in GBM.

Abstract

Glioblastoma multiforme (GBM) is a deadly brain tumor with a large unmet therapeutic need. Here, we tested the hypothesis that wild-type p53 is a negative transcriptional regulator of SLC7A11, the gene encoding the System xc- (SXC) catalytic subunit, xCT, in GBM. We demonstrate that xCT expression is inversely correlated with p53 expression in patient tissue. Using representative patient derived (PDX) tumor xenolines with wild-type, null, and mutant p53 we show that p53 expression negatively correlates with xCT expression. Using chromatin immunoprecipitation studies, we present a molecular interaction whereby p53 binds to the SLC7A11 promoter, suppressing gene expression in PDX GBM cells. Accordingly, genetic knockdown of p53 increases SLC7A11 transcript levels; conversely, over-expressing p53 in p53-null GBM cells downregulates xCT expression and glutamate release. Proof of principal studies in mice with flank gliomas demonstrate that daily treatment with the mutant p53 reactivator, PRIMA-1^Met, results in reduced tumor growth associated with reduced xCT expression. These findings suggest that p53 is a molecular switch for GBM glutamate biology, with potential therapeutic utility.

NADPH debt drives redox bankruptcy: SLC7A11/xCT-mediated cystine uptake as a double-edged sword in cellular redox regulation

Cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11; also known as xCT) plays a key role in antioxidant defense by mediating cystine uptake, promoting glutathione synthesis, and maintaining cell survival under oxidative stress conditions. Recent studies showed that, to prevent toxic buildup of highly insoluble cystine inside cells, cancer cells with high expression of SLC7A11 (SLC7A11^high) are forced to quickly reduce cystine to more soluble cysteine, which requires substantial NADPH supply from the glucose-pentose phosphate pathway (PPP) route, thereby inducing glucose- and PPP-dependency in SLC7A11^high cancer cells. Limiting glucose supply to SLC7A11^high cancer cells results in significant NADPH “debt”, redox “bankruptcy”, and subsequent cell death. This review summarizes our current understanding of NADPH-generating and -consuming pathways, discusses the opposing role of SLC7A11 in protecting cells from oxidative stress–induced cell death such as ferroptosis but promoting glucose starvation–induced cell death, and proposes the concept that SLC7A11-mediated cystine uptake acts as a double-edged sword in cellular redox regulation. A detailed understanding of SLC7A11 in redox biology may identify metabolic vulnerabilities in SLC7A11^high cancer for therapeutic targeting.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Cysteine Boosts Fitness Under Hypoxia-Mimicked Conditions in Ovarian Cancer by Metabolic Reprogramming

Among gynecologic malignancies, ovarian cancer is the third most prevalent and the most common cause of death, especially due to diagnosis at an advanced stage together with resistance to therapy. As a solid tumor grows, cancer cells in the microenvironment are exposed to regions of hypoxia, a selective pressure prompting tumor progression and chemoresistance. We have previously shown that cysteine contributes to the adaptation to this hypoxic microenvironment, but the mechanisms by which cysteine protects ovarian cancer cells from hypoxia-induced death are still to be unveiled. Herein, we hypothesized that cysteine contribution relies on cellular metabolism reprogramming and energy production, being cysteine itself a metabolic source. Our results strongly supported a role of xCT symporter in energy production that requires cysteine metabolism instead of hydrogen sulfide (H2S) per se. Cysteine degradation depends on the action of the H2S-synthesizing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and/or 3-mercaptopyruvate sulfurtransferase (MpST; together with cysteine aminotransferase, CAT). In normoxia, CBS and CSE inhibition had a mild impact on cysteine-sustained ATP production, pointing out the relevance of CAT + MpST pathway. However, in hypoxia, the concomitant inhibition of CBS and CSE had a stronger impact on ATP synthesis, thus also supporting a role of their hydrogen sulfide and/or cysteine persulfide-synthesizing activity in this stressful condition. However, the relative contributions of each of these enzymes (CBS/CSE/MpST) on cysteine-derived ATP synthesis under hypoxia remains unclear, due to the lack of specific inhibitors. Strikingly, NMR analysis strongly supported a role of cysteine in the whole cellular metabolism rewiring under hypoxia. Additionally, the use of cysteine to supply biosynthesis and bioenergetics was reinforced, bringing cysteine to the plateau of a main carbon sources in cancer. Collectively, this work supports that sulfur and carbon metabolism reprogramming underlies the adaptation to hypoxic microenvironment promoted by cysteine in ovarian cancer.

Antioxidant responses related to temozolomide resistance in glioblastoma

Glioblastoma remains one of the most challenging and devastating cancers, with only a very small proportion of patients achieving 5-year survival. The current standard of care consists of surgery, followed by radiation therapy with concurrent and maintenance chemotherapy with the alkylating agent temozolomide. To date, this drug is the only one that provides a significant survival benefit, albeit modest, as patients end up acquiring resistance to this drug. As a result, tumor progression and recurrence inevitably occur, leading to death. Several factors have been proposed to explain this resistance, including an upregulated antioxidant system to keep the elevated intracellular ROS levels, a hallmark of cancer cells, under control. In this review, we discuss the mechanisms of chemoresistance -including the important role of glioblastoma stem cells-with emphasis on antioxidant defenses and how agents that impair redox balance (i.e.: sulfasalazine, erastin, CB-839, withaferin, resveratrol, curcumin, chloroquine, and hydroxychloroquine) might be advantageous in combined therapies against this type of cancer.