Cysteine induces mitochondrial reductive stress in glioblastoma through hydrogen peroxide production

Amino acid metabolism in glioblastoma pathogenesis, immune evasion, and treatment resistance

Glioblastoma (GBM) ranks among the most lethal primary tumors of the central nervous system. This is partly due to its complex intracellular metabolism and interactions with the surrounding tumor microenvironment (TME). Compelling evidence represents that altered amino acids (AAs) metabolism plays a crucial role in both areas. The role of AAs and their metabolites in glioma biology is an emerging topic. Therefore, this review was conducted to summarize the current knowledge about the molecular mechanisms by which AAs participate in the GBM pathogenesis. AAs can directly influence tumor progression by affecting tumor cell metabolism or indirectly by releasing bioactive agents through particular metabolic pathways. This review begins by examining the metabolic pathways of essential AAs, such as tryptophan, tyrosine, and phenylalanine, which contribute to synthesizing critical neurotransmitters and shape tumor metabolism signatures. We explore how these pathways impact tumor growth and immune modulation, focusing on how AAs and their metabolites can promote malignant properties in GBM cells. AAs also play a pivotal role in reprogramming the TME, contributing to immune evasion and resistance to therapy. The review further discusses how tumor metabolism signatures, influenced by AA metabolism, can enhance the immunosuppressive microenvironment, providing new avenues for targeted immunotherapies. Finally, we outline potential therapeutic strategies to modulate AA metabolism and emphasize critical opportunities for future research to improve GBM management.

Methionine cycle inhibition disrupts antioxidant metabolism and reduces glioblastoma cell survival

Glioblastoma (GBM) is a highly aggressive primary malignant adult brain tumor that inevitably recurs with a fatal prognosis. This is due in part to metabolic reprogramming that allows tumors to evade treatment. Therefore, we must uncover the pathways mediating these adaptations to develop novel and effective treatments. We searched for genes that are essential in GBM cells as measured by a whole-genome pan-cancer CRISPR screen available from DepMap and identified the methionine metabolism genes MAT2A and AHCY. We conducted genetic knockdown, evaluated mitochondrial respiration, and performed targeted metabolomics to study the function of these genes in GBM. We demonstrate that MAT2A or AHCY knockdown induces oxidative stress, hinders cellular respiration, and reduces the survival of GBM cells. Furthermore, selective MAT2a or AHCY inhibition reduces GBM cell viability, impairs oxidative metabolism, and shifts the cellular metabolic profile towards oxidative stress and cell death. Mechanistically, MAT2a and AHCY regulate spare respiratory capacity, the redox buffer cystathionine, lipid and amino acid metabolism, and prevent oxidative damage in GBM cells. Our results point to the methionine metabolic pathway as a novel vulnerability point in GBM.

The Role of Reductive Stress in the Pathogenesis of Endocrine-Related Metabolic Diseases and Cancer

Reductive stress (RS), characterized by excessive accumulation of reducing equivalents such as NADH and NADPH, is emerging as a key factor in metabolic disorders and cancer. While oxidative stress (OS) has been widely studied, RS and its complex interplay with endocrine regulation remain less understood. This review explores molecular circuits of bidirectional crosstalk between metabolic hormones and RS, focusing on their role in diabetes, obesity, cardiovascular diseases, and cancer. RS disrupts insulin secretion and signaling, exacerbates metabolic inflammation, and contributes to adipose tissue dysfunction, ultimately promoting insulin resistance. In cardiovascular diseases, RS alters vascular smooth muscle cell function and myocardial metabolism, influencing ischemia-reperfusion injury outcomes. In cancer, RS plays a dual role: it enhances tumor survival by buffering OS and promoting metabolic reprogramming, yet excessive RS can trigger proteotoxicity and mitochondrial dysfunction, leading to apoptosis. Recent studies have identified RS-targeting strategies, including redox-modulating therapies, nanomedicine, and drug repurposing, offering potential for novel treatments. However, challenges remain, particularly in distinguishing physiological RS from pathological conditions and in overcoming therapy-induced resistance. Future research should focus on developing selective RS biomarkers, optimizing therapeutic interventions, and exploring the role of RS in immune and endocrine regulation.

N-acetylcysteine remodels the tumor microenvironment of primary and recurrent mouse glioblastoma

PURPOSE

Glioblastoma (GBM) exhibits a high ROS character, giving rise to an immunosuppressive microenvironment and tumor vascular abnormality. This study investigated the potential effect of N-acetylcysteine (NAC), an antioxidant, on primary and recurrent mouse brain tumors.

METHODS

We measured reactive oxygen species (ROS)/ glutathione (GSH) levels in human GBM. Additionally, we conducted NAC trials on primary mouse brain tumor models (GL261-Luc, CT2A-Luc) and a recurrent mouse GBM model (GL261-iCasp9-Luc). After brain tumor inoculation, mice received a daily 100 mg/kg NAC treatment, and the tumor volume was monitored via IVIS imaging. The efficacy of NAC was evaluated through survival time, tumor volume, ROS/GSH levels, M1/M2 macrophages, immune cells infiltration, and tumor vascularization.

RESULTS

Human GBM suffered from significant oxidative stress. With NAC treatment, mouse brain tumors exhibited a lower ROS level, more M1-like tumor-associated macrophages/microglia (TAMs), more CD8 + T cell infiltration, and a normalized vascular character. NAC inhibited tumor growth and suppressed recurrence in mouse brain tumor models.

CONCLUSION

NAC is a promising adjunctive drug to remodel the brain tumors microenvironment.

Inhibition of LDHB suppresses the metastatic potential of lung cancer by reducing mitochondrial GSH catabolism

Metastasis, the leading cause of cancer death, is closely linked to lactate metabolism. Our study aimed to investigate the role of lactate dehydrogenase B (LDHB), which mainly catalyzes the conversion of lactate to pyruvate, in the metastatic potential of lung cancer. We found that LDHB silencing reduced the invasion and migration ability of lung cancer cells in vitro. On the molecular level, LDHB silencing decreased the total intracellular levels of the antioxidant glutathione (GSH). Surprisingly, LDHB silencing did not increase cellular or mitochondrial reactive oxygen species (ROS) levels. Furthermore, supplementation with GSH monoethyl ester (GSH-mee), a cell-permeable derivative of GSH, partially restored the reduced in vitro colony formation capacity, the oxygen consumption rate, and the invasion and migration capacity of lung cancer cells after LDHB silencing. Using metabolic inhibitors, we showed that the rescue of colony formation after silencing LDHB by GSH-mee was due to enhanced GSH catabolism by γ-L-Glutamyl transpeptidase (GGT), which was mainly present in the mitochondrial fraction of lung cancer cells. Furthermore, we observed that high GGT expression was a prerequisite for the rescue of migratory capacity by GSH-mee after LDHB silencing. Finally, our in vivo experiments demonstrated that targeting LDHB reduced the metastasis of human and mouse lung cancer cells in immunodeficient and immunocompetent mouse models, respectively. In conclusion, LDHB silencing decreases GSH catabolism mediated by GGT, which is primarily located in the mitochondria of cancer cells. Therefore, targeting LDHB is a promising therapeutic approach for the prevention and treatment of metastatic lung cancer.

"Reductive stress" the overlooked side of cellular redox modulation in cancer: opportunity for design of next generation redox chemotherapeutics

The last three decades of redox biology research have been dominated by the term "oxidative stress" since it was first coined by Helmut Sies to represent a form of cellular redox modulation characterized by redox imbalance toward overproduction of oxidants. Almost every pathological condition, including cancer, has been linked with oxidative stress and so forth; targeting oxidative stress became the strategy for the new drug discovery with anticancer drugs aiming to selectively induce oxidative stress in cancerous cells while antioxidants aiming to prevent carcinogenesis as prophylactic agents. Time has now come to realize, how harmful the other side of the cellular redox spectrum, "reductive stress," characterized by redox imbalance toward the accumulation of reducing equivalents, maybe during carcinogenesis, and to tap its potential for the design of next-generation chemotherapeutic agents. Adjuvants-causing reductive stress may also work synergistically with radiation therapy under hypoxia to achieve better tumor control. Keeping this evolving field into account, the present review provides a current understating of the role of reductive stress in carcinogenesis, the status of reductive stress-based chemotherapeutic agents with particular emphasis on sulfhydryl and selenium-containing compounds and the gap areas that need to be addressed in future.

A cell state-specific metabolic vulnerability to GPX4-dependent ferroptosis in glioblastoma

Glioma cells hijack developmental programs to control cell state. Here, we uncover a glioma cell state-specific metabolic liability that can be therapeutically targeted. To model cell conditions at brain tumor inception, we generated genetically engineered murine gliomas, with deletion of p53 alone (p53) or with constitutively active Notch signaling (N1IC), a pathway critical in controlling astrocyte differentiation during brain development. N1IC tumors harbored quiescent astrocyte-like transformed cell populations while p53 tumors were predominantly comprised of proliferating progenitor-like cell states. Further, N1IC transformed cells exhibited increased mitochondrial lipid peroxidation, high ROS production and depletion of reduced glutathione. This altered mitochondrial phenotype rendered the astrocyte-like, quiescent populations more sensitive to pharmacologic or genetic inhibition of the lipid hydroperoxidase GPX4 and induction of ferroptosis. Treatment of patient-derived early-passage cell lines and glioma slice cultures generated from surgical samples with a GPX4 inhibitor induced selective depletion of quiescent astrocyte-like glioma cell populations with similar metabolic profiles. Collectively, these findings reveal a specific therapeutic vulnerability to ferroptosis linked to mitochondrial redox imbalance in a subpopulation of quiescent astrocyte-like glioma cells resistant to standard forms of treatment.

ABCC2 induces metabolic vulnerability and cellular ferroptosis via enhanced glutathione efflux in gastric cancer

BACKGROUND

Although it is traditionally believed that ATP binding cassette subfamily C member 2 (ABCC2) is a multidrug resistance-associated protein correlated with a worse prognosis, our previous and several other studies demonstrated the contrary to be true in gastric cancer (GC). We aim to explore the underlying mechanism of this discovery.

METHODS

Our study utilized whole-exome sequencing (WES), RNA sequencing, and droplet digital PCR (ddPCR) analysis of 80 gastric cancer samples, along with comprehensive immunohistochemical (IHC) analysis of 1044 human GC tissue samples.By utilizing CRISPRCas9 to genetically modify cell lines with the ABCC2-24C > T (rs717620) point mutation and conducting dual-luciferase reporter assays, we identified that transcription factors SOX9 and ETS1 serve as negative regulators of ABCC2 expression. Seahorse assay and mass spectrometry were used to discover altered metabolic patterns. Gain and loss-of-function experiments in GC cell lines and preclinical models were carried out to validate ABCC2 biological function.

RESULTS

ABCC2 high expression correlated with better prognosis, and rs717620 can influence ABCC2 expression by disrupting the binding of ETS1 and SOX9. Gain and loss-of-function experiments in GC cell lines demonstrated amino acid deprivation reduces proliferation, migration, and drug resistance in ABCC2-high GC cells. ABCC2 leads to reduced intracellular amino acid pools and disruption of cellular energy metabolism. This phenomenon depended on ABCC2-mediated GSH extrusion, resulting in alterations in redox status, thereby increasing the cell's susceptibility to ferroptosis. Furthermore, patient-derived organoids and patient-derived tumor-like cell clusters were used to observe impact of ABCC2 on therapeutic effect. In the xenograft model with high ABCC2 expression, we observed that constricting amino acid intake in conjunction with GPX4 inactivation resulted in notable tumor regression.

CONCLUSIONS

Our findings demonstrate a significant role of ABCC2 in amino acid metabolism and ferroptosis by mediating GSH efflux in GC. This discovery underlines the potential of combining multiple ferroptosis targets as a promising therapeutic strategy for GC with high ABCC2 expression.

HIGHLIGHTS

ABCC2 plays a crucial role in inducing metabolic vulnerability and ferroptosis in gastric cancer through enhanced glutathione efflux. The ABCC2 24C > T polymorphism is a key factor influencing its expression. These results highlight the potential of ABCC2 as a predictive biomarker and therapeutic target in gastric cancer.

Deciphering Glioblastoma: Fundamental and Novel Insights into the Biology and Therapeutic Strategies of Gliomas

Gliomas constitute a diverse and complex array of tumors within the central nervous system (CNS), characterized by a wide range of prognostic outcomes and responses to therapeutic interventions. This literature review endeavors to conduct a thorough investigation of gliomas, with a particular emphasis on glioblastoma (GBM), beginning with their classification and epidemiological characteristics, evaluating their relative importance within the CNS tumor spectrum. We examine the immunological context of gliomas, unveiling the intricate immune environment and its ramifications for disease progression and therapeutic strategies. Moreover, we accentuate critical developments in understanding tumor behavior, focusing on recent research breakthroughs in treatment responses and the elucidation of cellular signaling pathways. Analyzing the most novel transcriptomic studies, we investigate the variations in gene expression patterns in glioma cells, assessing the prognostic and therapeutic implications of these genetic alterations. Furthermore, the role of epigenetic modifications in the pathogenesis of gliomas is underscored, suggesting that such changes are fundamental to tumor evolution and possible therapeutic advancements. In the end, this comparative oncological analysis situates GBM within the wider context of neoplasms, delineating both distinct and shared characteristics with other types of tumors.