Lipid droplets and ferroptosis as new players in brain cancer glioblastoma progression and therapeutic resistance

The marine-derived compound TAG alleviates Parkinson's disease by restoring RUBCN-mediated lipid metabolism homeostasis

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its prevalence is increasing. Currently, no effective therapies for PD exist. Marine-derived natural compounds are considered important resources for the discovery of new drugs due to their distinctive structures and diverse activities. In this study, tetrahydroauroglaucin (TAG), a polyketide isolated from a marine sponge, was found to have notable neuroprotective effects on MPTP/MPP+-induced neurotoxicity. RNA sequencing analysis and metabolomics revealed that TAG significantly improved lipid metabolism disorder in PD models. Further investigation indicated that TAG markedly decreased the accumulation of lipid droplets (LDs), downregulated the expression of RUBCN, and promoted autophagic flux. Moreover, conditional knockdown of Rubcn notably attenuated PD-like symptoms and the accumulation of LDs, accompanied by blockade of the neuroprotective effect of TAG. Collectively, our results first indicated that TAG, a promising PD therapeutic candidate, could suppress the accumulation of LDs through the RUBCN-autophagy pathway, which highlighted a novel and effective strategy for PD treatment.

A new strategy for screening novel functional genes involved in reduction of lipid droplet accumulation

Lipid droplets (LDs) are organelles that store excess lipids and provide fatty acids for energy production during starvation. LDs are also essential for cellular maintenance, but excessive accumulation of LDs triggers various cancers in addition to metabolic diseases such as diabetes. In this study, we aimed to develop a strategy to identify new genes that reduces accumulation of LDs in cancer cells using an RNA interference (RNAi) screening system employing artificial sequence-enriched shRNA libraries. Monitoring LDs by fluorescent activated cell sorting, the subsequently collected cumulative LDs cells, and shRNA sequence analysis identified a clone that potentially functioned to accumulate LDs. The clone showed no identical sequence to human Refseq. It showed very similar sequence to seven genes by allowing three mismatches. Among these genes, we identified the mediator complex subunit 6 (MED6) gene as a target of this shRNA. Silencing of MED6 led to an increase in LD accumulation and expression of the marker genes, PLIN2 and DGAT1, in fatty cells. MED6 is a member of the mediator complex that regulates RNA polymerase II transcription through transcription factor II. Some mediator complexes play important roles in both normal and pathophysiological transcription processes. These results suggest that MED6 transcriptionally regulates the genes involved in lipid metabolism and suppresses LD accumulation.

The lipid droplet in cancer: From being a tumor-supporting hallmark to clinical therapy

INTRODUCTION

Abnormal lipid metabolism, one of the hallmarks in cancer, has gradually emerged as a novel target for cancer treatment. As organelles that store and release excess lipids, lipid droplets (LDs) resemble "gears" and facilitate cancer development in the body.

AIM

This review discusses the life cycle of LDs, the relationship between abnormal LDs and cancer hallmarks, and the application of LDs in theragnostic and clinical contexts to provide a contemporary understanding of the role of LDs in cancer.

METHODS

A systematic literature search was conducted in PubMed and SPORTDiscus. Retrieve and summarize clinical trials of drugs that target proteins associated with LD formation using the Clinical Trials website. Create a schematic diagram of lipid droplets in the tumor microenvironment using Adobe Illustrator.

CONCLUSION

As one of the top ten hallmarks of cancer, abnormal lipid metabolism caused by excessive generation of LDs interrelates with other hallmarks. The crosstalk between excessive LDs and intracellular free fatty acids (FFAs) promotes an inflammatory environment that supports tumor growth. Moreover, LDs contribute to cancer metastasis and cell death resistance in vivo. Statins, as HMGCR inhibitors, are promising to be the pioneering commercially available anti-cancer drugs that target LD formation.

Ferroptosis resistance in cancer: recent advances and future perspectives

Ferroptosis is an iron-dependent, non-apoptotic form of regulated cell death and has been implicated in the occurrence and development of various diseases, including heart disease, nervous system diseases and cancer. Ferroptosis induction recently emerged as an attractive strategy for cancer therapy. Ferroptosis has become a potential target for intervention in these diseases or injuries in relevant preclinical models. This review summarizes recent progress on the mechanisms of ferroptosis resistance in cancer, highlights redox status and metabolism's role in it. Combination therapy for ferroptosis has great potential in cancer treatment, especially malignant tumors that are resistant to conventional therapies. This review will lead us to have a comprehensive understanding of the future exploration of ferroptosis and cancer therapy. A deeper understanding of the relationship between ferroptosis resistance and metabolism reprogramming may provide new strategies for tumor treatment and drug development based on ferroptosis.

Multiomic screening of invasive GBM cells reveals targetable transsulfuration pathway alterations

While the poor prognosis of glioblastoma arises from the invasion of a subset of tumor cells, little is known of the metabolic alterations within these cells that fuel invasion. We integrated spatially addressable hydrogel biomaterial platforms, patient site-directed biopsies, and multiomics analyses to define metabolic drivers of invasive glioblastoma cells. Metabolomics and lipidomics revealed elevations in the redox buffers cystathionine, hexosylceramides, and glucosyl ceramides in the invasive front of both hydrogel-cultured tumors and patient site-directed biopsies, with immunofluorescence indicating elevated reactive oxygen species (ROS) markers in invasive cells. Transcriptomics confirmed upregulation of ROS-producing and response genes at the invasive front in both hydrogel models and patient tumors. Among oncologic ROS, H2O2 specifically promoted glioblastoma invasion in 3D hydrogel spheroid cultures. A CRISPR metabolic gene screen revealed cystathionine γ-lyase (CTH), which converts cystathionine to the nonessential amino acid cysteine in the transsulfuration pathway, to be essential for glioblastoma invasion. Correspondingly, supplementing CTH knockdown cells with exogenous cysteine rescued invasion. Pharmacologic CTH inhibition suppressed glioblastoma invasion, while CTH knockdown slowed glioblastoma invasion in vivo. Our studies highlight the importance of ROS metabolism in invasive glioblastoma cells and support further exploration of the transsulfuration pathway as a mechanistic and therapeutic target.

Drug Repurposing-Based Brain-Targeting Self-Assembly Nanoplatform Using Enhanced Ferroptosis against Glioblastoma

Glioblastoma (GBM), the most aggressive and lethal form of malignant brain tumor, is a therapeutic challenge due to the drug filtration capabilities of the blood-brain barrier (BBB). Interestingly, glioblastoma tends to resist apoptosis during chemotherapy, but is susceptible to ferroptosis. Developing therapies that can effectively target glioblastoma by crossing the BBB and evoke ferroptosis are, therefore, crucial for improving treatment outcomes. Herein, a versatile biomimetic nanoplatform, L-D-I/NPs, is designed that self-assembled by loading the antimalarial drug dihydroartemisinin (DHA) and the photosensitizer indocyanine green (ICG) onto lactoferrin (LF). This nanoplatform can selectively target glioblastoma by binding to low-density lipoprotein receptor-related protein-1 (LRP1) and crossing the BBB, thus inducing glioblastoma cell ferroptosis by boosting intracellular reactive oxygen species (ROS) accumulation and iron overload. In addition, L-D-I/NPs have demonstrated the ability to effectively suppress the progression of orthotopic glioblastoma and significantly prolong survival in a mouse glioblastoma model. This nanoplatform has facilitated the application of non-chemotherapeutic drugs in tumor treatment with minimal adverse effects, paving the way for highly efficient ferroptosis-based therapies for glioblastoma.

Early to sustained impacts of lethal radiation on circulating miRNAs in a minipig model

Early diagnosis of lethal radiation is imperative since its intervention time windows are considerably short. Hence, ideal diagnostic candidates of radiation should be easily accessible, enable to inform about the stress history and objectively triage subjects in a time-efficient manner. Therefore, the small molecules such as metabolites and microRNAs (miRNAs) from plasma are legitimate biomarker candidate for lethal radiation. Our objectives were to comprehend the radiation-driven molecular pathogenesis and thereby determine biomarkers of translational potential. We investigated an established minipig model of LD70/45 total body irradiation (TBI). In this pilot study, plasma was collected pre-TBI and at multiple time points post-TBI. The majority of differentially expressed miRNAs and metabolites were perturbed immediately after TBI that potentially underlined the severity of its acute impact. The integrative network analysis of miRNA and metabolites showed a cohesive response; the early and consistent perturbations of networks were linked to cancer and the shift in musculoskeletal atrophy synchronized with the comorbidity-networks associated with inflammation and bioenergy synthesis. Subsequent comparative pipeline delivered 92 miRNAs, which demonstrated sequential homology between human and minipig, and potentially similar responses to lethal radiation across these two species. This panel promised to retrospectively inform the time since the radiation occurred; thereby could facilitate knowledge-driven interventions.

Recent advances of ferroptosis in tumor: From biological function to clinical application

Ferroptosis is a recently recognized form of cell death with distinct features in terms of morphology, biochemistry, and molecular mechanisms. Unlike other types of cell death, ferroptosis is characterized by iron dependence, reactive oxygen species accumulation and lipid peroxidation. Recent studies have demonstrated that selective autophagy plays a vital role in the induction of ferroptosis, including ferritinophagy, lipophagy, clockophagy, and chaperone-mediated autophagy. Emerging evidence has indicated the involvement of ferroptosis in tumorigenesis through regulating various biological processes, including tumor growth, metastasis, stemness, drug resistance, and recurrence. Clinical and preclinical studies have found that novel therapies targeting ferroptosis exert great potential in the treatment of tumors. This review provides a comprehensive overview of the molecular mechanisms in ferroptosis, especially in autophagy-driven ferroptosis, discusses the recent advances in the biological roles of ferroptosis in tumorigenesis, and highlights the application of novel ferroptosis-targeted therapies in the clinical treatment of tumors.

A comprehensive overview of recent developments on the mechanisms and pathways of ferroptosis in cancer: the potential implications for therapeutic strategies in ovarian cancer

Cancer cells adapt to environmental changes and alter their metabolic pathways to promote survival and proliferation. Metabolic reprogramming not only allows tumor cells to maintain a reduction-oxidation balance by rewiring resources for survival, but also causes nutrient addiction or metabolic vulnerability. Ferroptosis is a form of regulated cell death characterized by the iron-dependent accumulation of lipid peroxides. Excess iron in ovarian cancer amplifies free oxidative radicals and drives the Fenton reaction, thereby inducing ferroptosis. However, ovarian cancer is characterized by ferroptosis resistance. Therefore, the induction of ferroptosis is an exciting new targeted therapy for ovarian cancer. In this review, potential metabolic pathways targeting ferroptosis were summarized to promote anticancer effects, and current knowledge and future perspectives on ferroptosis for ovarian cancer therapy were discussed. Two therapeutic strategies were highlighted in this review: directly inducing the ferroptosis pathway and targeting metabolic vulnerabilities that affect ferroptosis. The overexpression of SLC7A11, a cystine/glutamate antiporter SLC7A11 (also known as xCT), is involved in the suppression of ferroptosis. xCT inhibition by ferroptosis inducers (e.g., erastin) can promote cell death when carbon as an energy source of glucose, glutamine, or fatty acids is abundant. On the contrary, xCT regulation has been reported to be highly dependent on the metabolic vulnerability. Drugs that target intrinsic metabolic vulnerabilities (e.g., GLUT1 inhibitors, PDK4 inhibitors, or glutaminase inhibitors) predispose cancer cells to death, which is triggered by decreased nicotinamide adenine dinucleotide phosphate generation or increased reactive oxygen species accumulation. Therefore, therapeutic approaches that either directly inhibit the xCT pathway or target metabolic vulnerabilities may be effective in overcoming ferroptosis resistance. Real-time monitoring of changes in metabolic pathways may aid in selecting personalized treatment modalities. Despite the rapid development of ferroptosis-inducing agents, therapeutic strategies targeting metabolic vulnerability remain in their infancy. Thus, further studies must be conducted to comprehensively understand the precise mechanism linking metabolic rewiring with ferroptosis.

The regulatory role of lipophagy in central nervous system diseases

Lipid droplets (LDs) are the organelles for storing neutral lipids, which are broken down when energy is insufficient. It has been suggested that excessive accumulation of LDs can affect cellular function, which is important to coordinate homeostasis of lipids in vivo. Lysosomes play an important role in the degradation of lipids, and the process of selective autophagy of LDs through lysosomes is known as lipophagy. Dysregulation of lipid metabolism has recently been associated with a variety of central nervous system (CNS) diseases, but the specific regulatory mechanisms of lipophagy in these diseases remain to be elucidated. This review summarizes various forms of lipophagy and discusses the role that lipophagy plays in the development of CNS diseases in order to reveal the related mechanisms and potential therapeutic targets for these diseases.