Autophagy regulates fatty acid availability for oxidative phosphorylation through mitochondria-endoplasmic reticulum contact sites

Autophagy as a Therapeutic Target in Breast Tumors: The Cancer stem cell perspective

Breast cancer is a heterogeneous disease, with a subpopulation of tumor cells known as breast cancer stem cells (BCSCs) with self-renewal and differentiation abilities that play a critical role in tumor initiation, progression, and therapy resistance. The tumor microenvironment (TME) is a complex area where diverse cancer cells reside creating a highly interactive environment with secreted factors, and the extracellular matrix. Autophagy, a cellular self-digestion process, influences dynamic cellular processes in the tumor TME integrating diverse signals that regulate tumor development and heterogeneity. Autophagy acts as a double-edged sword in the breast TME, with both tumor-promoting and tumor-suppressing roles. Autophagy promotes breast tumorigenesis by regulating tumor cell survival, migration and invasion, metabolic reprogramming, and epithelial-mesenchymal transition (EMT). BCSCs harness autophagy to maintain stemness properties, evade immune surveillance, and resist therapeutic interventions. Conversely, excessive, or dysregulated autophagy may lead to BCSC differentiation or cell death, offering a potential avenue for therapeutic exploration. The molecular mechanisms that regulate autophagy in BCSCs including the mammalian target of rapamycin (mTOR), AMPK, and Beclin-1 signaling pathways may be potential targets for pharmacological intervention in breast cancer. This review provides a comprehensive overview of the relationship between autophagy and BCSCs, highlighting recent advancements in our understanding of their interplay. We also discuss the current state of autophagy-targeting agents and their preclinical and clinical development in BCSCs.

Unveiling the role of AGT in lipid metabolism and regulated cell death in colon cancer

BACKGROUND

Lipid metabolism and regulated cell death (RCD) play a role in the remodeling of tumor immune microenvironment and regulation of cancer progression. Since the underlying immune mechanisms of colon cancer remain elusive, this study aims to identify potential therapeutic target genes.

METHODS

Differential genes related to lipid metabolism and RCD in COAD patients were identified using R language and online tools. Based on the expression of genes, two groups were classified using consensus clustering. CIBERSORT and ssGSEA were used to detect immune infiltration in both groups. Prognostic signature genes for colon cancer were screened using machine learning algorithms. KEGG, GO and GSEA for gene pathway enrichment. In addition, interacting genes in the immune module were obtained using a weighted gene co-expression network (WGCNA). Finally, expression and mutation of key in colon cancer genes were detected using TIMER, HPR, cBioPortal website and qPCR.

RESULTS

The consensus clustering analysis revealed that 231 relevant differential genes were highly associated with immune infiltration. A series of machine learning and website analyses identified AGT as a hub gene linked to lipid metabolism and regulated cell death, which is overexpressed in colon cancer.

CONCLUSION

AGT, as a signature gene of lipid metabolism and regulated cell death, plays a critical role in the development of COAD and is associated with tumor immune infiltration.

No energy, no autophagy-Mechanisms and therapeutic implications of autophagic response energy requirements

Autophagy is a lysosome-mediated self-degradation process of central importance for cellular quality control. It also provides macromolecule building blocks and substrates for energy metabolism during nutrient or energy deficiency, which are the main stimuli for autophagy induction. However, like most biological processes, autophagy itself requires ATP, and there is an energy threshold for its initiation and execution. We here present the first comprehensive review of this often-overlooked aspect of autophagy research. The studies in which ATP deficiency suppressed autophagy in vitro and in vivo were classified according to the energy pathway involved (oxidative phosphorylation or glycolysis). A mechanistic insight was provided by pinpointing the critical ATP-consuming autophagic events, including transcription/translation/interaction of autophagy-related molecules, autophagosome formation/elongation, autophagosome fusion with the lysosome, and lysosome acidification. The significance of energy-dependent fine-tuning of autophagic response for preserving the cell homeostasis, and potential implications for the therapy of cancer, autoimmunity, metabolic disorders, and neurodegeneration are discussed.

Fibrotic pathways and fibroblast-like synoviocyte phenotypes in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis, characterized by osteophyte formation, cartilage degradation, and structural and cellular alterations of the synovial membrane. Activated fibroblast-like synoviocytes (FLS) of the synovial membrane have been identified as key drivers, secreting humoral mediators that maintain inflammatory processes, proteases that cause cartilage and bone destruction, and factors that drive fibrotic processes. In normal tissue repair, fibrotic processes are terminated after the damage has been repaired. In fibrosis, tissue remodeling and wound healing are exaggerated and prolonged. Various stressors, including aging, joint instability, and inflammation, lead to structural damage of the joint and micro lesions within the synovial tissue. One result is the reduced production of synovial fluid (lubricants), which reduces the lubricity of the cartilage areas, leading to cartilage damage. In the synovial tissue, a wound-healing cascade is initiated by activating macrophages, Th2 cells, and FLS. The latter can be divided into two major populations. The destructive thymocyte differentiation antigen (THY)1─ phenotype is restricted to the synovial lining layer. In contrast, the THY1+ phenotype of the sublining layer is classified as an invasive one with immune effector function driving synovitis. The exact mechanisms involved in the transition of fibroblasts into a myofibroblast-like phenotype that drives fibrosis remain unclear. The review provides an overview of the phenotypes and spatial distribution of FLS in the synovial membrane of OA, describes the mechanisms of fibroblast into myofibroblast activation, and the metabolic alterations of myofibroblast-like cells.

Pparα activation stimulates autophagic flux through lipid catabolism-independent route

Autophagy is a cellular process that involves the fusion of autophagosomes and lysosomes to degrade damaged proteins or organelles. Triglycerides are hydrolyzed by autophagy, releasing fatty acids for energy through mitochondrial fatty acid oxidation (FAO). Inhibited mitochondrial FAO induces autophagy, establishing a crosstalk between lipid catabolism and autophagy. Peroxisome proliferator-activated receptor α (PPARα), a transcription factor, stimulates lipid catabolism genes, including fatty acid transport and mitochondrial FAO, while also inducing autophagy through transcriptional regulation of transcription factor EB (TFEB). Therefore, the study explores whether PPARα regulates autophagy through TFEB transcriptional control or mitochondrial FAO. In aquaculture, addressing liver lipid accumulation in fish is crucial. Investigating the link between lipid catabolism and autophagy is significant for devising lipid-lowering strategies and maintaining fish health. The present study investigated the impact of dietary fenofibrate and L-carnitine on autophagy by activating Pparα and enhancing FAO in Nile tilapia (Oreochromis niloticus), respectively. The dietary fenofibrate and L-carnitine reduced liver lipid content and enhanced ATP production, particularly fenofibrate. FAO enhancement by L-carnitine showed no changes in autophagic protein levels and autophagic flux. Moreover, fenofibrate-activated Pparα promoted the expression and nuclear translocation of Tfeb, upregulating autophagic initiation and lysosomal biogenesis genes. Pparα activation exhibited an increasing trend of LC3II protein at the basal autophagy and cumulative p62 protein trends after autophagy inhibition in zebrafish liver cells. These data show that Pparα activation-induced autophagic flux should be independent of lipid catabolism.

FLT3-Mutated Leukemic Stem Cells: Mechanisms of Resistance and New Therapeutic Targets

Despite the availability of target drugs in the first and second line, only 30% of FLT3mut AMLs are cured. Among the multiple mechanisms of resistance, those of FLT3mut LSC are the most difficult to eradicate because of their metabolic and genomic characteristics. Reactivation of glycogen synthesis, inhibition of the RAS/MAPK pathway, and degradation of FLT3 may be potential aids to fight the resistance of LSC to FLT3i. LSC is also characterized by the expression of a CD34+/CD25+/CD123+/CD99+ immunophenotype. The receptor and ligand of FLT3, the natural killer group 2 member D ligand (NKGD2L), and CD123 are some of the targets of chimeric antigen receptor T cells (CAR-T), bispecific T-cell engager molecules (BiTEs), CAR-NK and nanoparticles recently designed and reported here. The combination of these new therapeutic options, hopefully in a minimal residual disease (MRD)-driven approach, could provide the future answer to the challenge of treating FLT3mut AML.

Mitochondrial Dysfunction of Astrocytes Mediates Lipid Accumulation in Temporal Lobe Epilepsy

Lipid-accumulated reactive astrocytes (LARAs) have recently been confirmed to be a pivotal cell type present in temporal lobe epilepsy (TLE) lesions. These cells not only induce anomalous lipid accumulation within the epileptic foci but also decrease the seizure threshold by employing upregulated activation of the adenosine A2A receptor (A2AR). Furthermore, disturbances in mitochondrial oxidative phosphorylation (OxPhos) have been noted as significant drivers of lipid accumulation in astrocytes. Moreover, the deficiency of OxPhos in astrocytes can induce severe neuroinflammation, which can worsen the progression of TLE. Accordingly, further exploration of the correlation between mitochondrial dysfunction, LARAs-mediated lipid accumulation, and A2AR activation within epilepsy lesions is warranted. It could potentially elucidate the vital role of mitochondrial dysfunction in the pathogenesis of TLE.

Flvcr1a deficiency promotes heme-based energy metabolism dysfunction in skeletal muscle

The definition of cell metabolic profile is essential to ensure skeletal muscle fiber heterogeneity and to achieve a proper equilibrium between the self-renewal and commitment of satellite stem cells. Heme sustains several biological functions, including processes profoundly implicated with cell metabolism. The skeletal muscle is a significant heme-producing body compartment, but the consequences of impaired heme homeostasis on this tissue have been poorly investigated. Here, we generate a skeletal-muscle-specific feline leukemia virus subgroup C receptor 1a (FLVCR1a) knockout mouse model and show that, by sustaining heme synthesis, FLVCR1a contributes to determine the energy phenotype in skeletal muscle cells and to modulate satellite cell differentiation and muscle regeneration.

Crosstalk between autophagy and metabolism: implications for cell survival in acute myeloid leukemia

Acute myeloid leukemia (AML), a prevalent form of leukemia in adults, is often characterized by low response rates to chemotherapy, high recurrence rates, and unfavorable prognosis. A critical barrier in managing refractory or recurrent AML is the resistance to chemotherapy. Increasing evidence indicates that tumor cell metabolism plays a crucial role in AML progression, survival, metastasis, and treatment resistance. Autophagy, an essential regulator of cellular energy metabolism, is increasingly recognized for its role in the metabolic reprogramming of AML. Autophagy sustains leukemia cells during chemotherapy by not only providing energy but also facilitating rapid proliferation through the supply of essential components such as amino acids and nucleotides. Conversely, the metabolic state of AML cells can influence the activity of autophagy. Their mutual coordination helps maintain intrinsic cellular homeostasis, which is a significant contributor to chemotherapy resistance in leukemia cells. This review explores the recent advancements in understanding the interaction between autophagy and metabolism in AML cells, emphasizing their roles in cell survival and drug resistance. A comprehensive understanding of the interplay between autophagy and leukemia cell metabolism can shed light on leukemia cell survival strategies, particularly under adverse conditions such as chemotherapy. This insight may also pave the way for innovative targeted treatment strategies.

Polyamine Signal through HCC Microenvironment: A Key Regulator of Mitochondrial Preservation and Turnover in TAMs

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, and, with increasing research on the tumor immune microenvironment (TIME), the immunosuppressive micro-environment of HCC hampers further application of immunotherapy, even though immunotherapy can provide survival benefits to patients with advanced liver cancer. Current studies suggest that polyamine metabolism is not only a key metabolic pathway for the formation of immunosuppressive phenotypes in tumor-associated macrophages (TAMs), but it is also profoundly involved in mitochondrial quality control signaling and the energy metabolism regulation process, so it is particularly important to further investigate the role of polyamine metabolism in the tumor microenvironment (TME). In this review, by summarizing the current research progress of key enzymes and substrates of the polyamine metabolic pathway in regulating TAMs and T cells, we propose that polyamine biosynthesis can intervene in the process of mitochondrial energy metabolism by affecting mitochondrial autophagy, which, in turn, regulates macrophage polarization and T cell differentiation. Polyamine metabolism may be a key target for the interactive dialog between HCC cells and immune cells such as TAMs, so interfering with polyamine metabolism may become an important entry point to break intercellular communication, providing new research space for developing polyamine metabolism-based therapy for HCC.

Adipo-glial signaling mediates metabolic adaptation in peripheral nerve regeneration

The peripheral nervous system harbors a remarkable potential to regenerate after acute nerve trauma. Full functional recovery, however, is rare and critically depends on peripheral nerve Schwann cells that orchestrate breakdown and resynthesis of myelin and, at the same time, support axonal regrowth. How Schwann cells meet the high metabolic demand required for nerve repair remains poorly understood. We here report that nerve injury induces adipocyte to glial signaling and identify the adipokine leptin as an upstream regulator of glial metabolic adaptation in regeneration. Signal integration by leptin receptors in Schwann cells ensures efficient peripheral nerve repair by adjusting injury-specific catabolic processes in regenerating nerves, including myelin autophagy and mitochondrial respiration. Our findings propose a model according to which acute nerve injury triggers a therapeutically targetable intercellular crosstalk that modulates glial metabolism to provide sufficient energy for successful nerve repair.

Lead exposure induced lipid metabolism disorders by regulating the lipophagy process in microglia

Environmental lead (Pb) pollution is a worldwide public health problem and causes various diseases, especially neurodegenerative diseases. It is increasingly recognized that microglia-mediated neuroinflammation plays a crucial role in lead neurotoxicity, but the underlying mechanisms remain to be further explored. Recent studies indicated that cell metabolism, especially lipid metabolism, regulates many microglial functions, including cytokine secretion and phagocytosis. Whether lipid metabolism is involved in Pb-induced neuroinflammation is still unknown. In the current studies, we investigated the effects of Pb on microglial lipid metabolism by utilizing lipidomics. Histochemistry staining and oxygen consumption rate (OCR) were used to validate lipidomics results. Fenofibrate (FEN), a peroxisome proliferator-activated receptor-α (PPAR-α) agonist, was applied to investigate whether lipid metabolism regulation mitigated Pb's neuroinflammatory response. Microglial autophagic proteins were detected to investigate the role of lipophagy in Pb's effect on lipid metabolism. Our results showed that Pb exposure increased concentrations of various lipid metabolites and induced lipid metabolism disorders, especially in fatty acid metabolism. Pb caused lipid droplet (LD) accumulation and slightly enhanced fatty acid oxidation (FAO) in microglia. FEN pretreatment markedly inhibited Pb's effects on LDs and further mitigated Pb-induced inflammatory response by reducing pro-cytokines' expression and enhancing phagocytosis function. FEN intervention also inhibited Pb's neurotoxicity by improving cognition-related behaviors. Pb exposure induced an abnormal increase of autophagic proteins, but the FEN addition partially neutralized Pb's effects on autophagy. Our data indicate that the Pb-induced neuroinflammation is regulated by fatty acid metabolism via the lipophagy process. Therapies focusing on lipid metabolism regulation are powerful tactics in Pb toxicity prevention and treatment.

An Overview on Lipid Droplets Accumulation as Novel Target for Acute Myeloid Leukemia Therapy

Metabolic reprogramming is a key alteration in tumorigenesis. In cancer cells, changes in metabolic fluxes are required to cope with large demands on ATP, NADPH, and NADH, as well as carbon skeletons. In particular, dysregulation in lipid metabolism ensures a great energy source for the cells and sustains cell membrane biogenesis and signaling molecules, which are necessary for tumor progression. Increased lipid uptake and synthesis results in intracellular lipid accumulation as lipid droplets (LDs), which in recent years have been considered hallmarks of malignancies. Here, we review current evidence implicating the biogenesis, composition, and functions of lipid droplets in acute myeloid leukemia (AML). This is an aggressive hematological neoplasm originating from the abnormal expansion of myeloid progenitor cells in bone marrow and blood and can be fatal within a few months without treatment. LD accumulation positively correlates with a poor prognosis in AML since it involves the activation of oncogenic signaling pathways and cross-talk between the tumor microenvironment and leukemic cells. Targeting altered LD production could represent a potential therapeutic strategy in AML. From this perspective, we discuss the main inhibitors tested in in vitro AML cell models to block LD formation, which is often associated with leukemia aggressiveness and which may find clinical application in the future.

Oleic Acid Exhibits Anti-Proliferative and Anti-Invasive Activities via the PTEN/AKT/mTOR Pathway in Endometrial Cancer

Reprogramming of fatty acid metabolism promotes cell growth and metastasis through a variety of processes that stimulate signaling molecules, energy storage, and membrane biosynthesis in endometrial cancer. Oleic acid is one of the most important monounsaturated fatty acids in the human body, which appears to have both pro- and anti-tumorigenic activities in various pre-clinical models. In this study, we evaluated the potential anti-tumor effects of oleic acid in endometrial cancer cells and the LKB1fl/flp53fl/fl mouse model of endometrial cancer. Oleic acid increased lipogenesis, inhibited cell proliferation, caused cell cycle G1 arrest, induced cellular stress and apoptosis, and suppressed invasion in endometrial cancer cells. Targeting of diacylglycerol acyltransferases 1 and 2 effectively increased the cytotoxicity of oleic acid. Moreover, oleic acid significantly increased the expression of wild-type PTEN, and knockdown of PTEN by shRNA partially reversed the anti-proliferative and anti-invasive effects of oleic acid. Inhibition of the AKT/mTOR pathway by ipatasertib effectively increased the anti-tumor activity of oleic acid in endometrial cancer cells. Oleic acid treatment (10 mg/kg, daily, oral) for four weeks significantly inhibited tumor growth by 52.1% in the LKB1fl/flp53fl/fl mice. Our findings demonstrated that oleic acid exhibited anti-tumorigenic activities, dependent on the PTEN/AKT/mTOR signaling pathway, in endometrial cancer.

Dissecting the Role of Autophagy-Related Proteins in Cancer Metabolism and Plasticity

Modulation of autophagy as an anticancer strategy has been widely studied and evaluated in several cell models. However, little attention has been paid to the metabolic changes that occur in a cancer cell when autophagy is inhibited or induced. In this review, we describe how the expression and regulation of various autophagy-related (ATGs) genes and proteins are associated with cancer progression and cancer plasticity. We present a comprehensive review of how deregulation of ATGs affects cancer cell metabolism, where inhibition of autophagy is mainly reflected in the enhancement of the Warburg effect. The importance of metabolic changes, which largely depend on the cancer type and form part of a cancer cell's escape strategy after autophagy modulation, is emphasized. Consequently, pharmacological strategies based on a dual inhibition of metabolic and autophagy pathways emerged and are reviewed critically here.

Lipid droplet deposition in the regenerating liver: A promoter, inhibitor, or bystander?

Liver regeneration (LR) is a complex process involving intricate networks of cellular connections, cytokines, and growth factors. During the early stages of LR, hepatocytes accumulate lipids, primarily triacylglycerol, and cholesterol esters, in the lipid droplets. Although it is widely accepted that this phenomenon contributes to LR, the impact of lipid droplet deposition on LR remains a matter of debate. Some studies have suggested that lipid droplet deposition has no effect or may even be detrimental to LR. This review article focuses on transient regeneration-associated steatosis and its relationship with the liver regenerative response.

Targeting drug-tolerant cells: A promising strategy for overcoming acquired drug resistance in cancer cells

Drug resistance remains the greatest challenge in improving outcomes for cancer patients who receive chemotherapy and targeted therapy. Surmounting evidence suggests that a subpopulation of cancer cells could escape intense selective drug treatment by entering a drug-tolerant state without genetic variations. These drug-tolerant cells (DTCs) are characterized with a slow proliferation rate and a reversible phenotype. They reside in the tumor region and may serve as a reservoir for resistant phenotypes. The survival of DTCs is regulated by epigenetic modifications, transcriptional regulation, mRNA translation remodeling, metabolic changes, antiapoptosis, interactions with the tumor microenvironment, and activation of signaling pathways. Thus, targeting the regulators of DTCs opens a new avenue for the treatment of therapy-resistant tumors. In this review, we first provide an overview of common characteristics of DTCs and the regulating networks in DTCs development. We also discuss the potential therapeutic opportunities to target DTCs. Last, we discuss the current challenges and prospects of the DTC-targeting approach to overcome acquired drug resistance. Reviewing the latest developments in DTC research could be essential in discovering of methods to eliminate DTCs, which may represent a novel therapeutic strategy for preventing drug resistance in the future.

PtdIns4P exchange at endoplasmic reticulum-autolysosome contacts is essential for autophagy and neuronal homeostasis

Inter-organelle contacts enable crosstalk among organelles, facilitating the exchange of materials and coordination of cellular events. In this study, we demonstrated that, upon starvation, autolysosomes recruit Pi4KIIα (Phosphatidylinositol 4-kinase II α) to generate phosphatidylinositol-4-phosphate (PtdIns4P) on their surface and establish endoplasmic reticulum (ER)-autolysosome contacts through PtdIns4P binding proteins Osbp (Oxysterol binding protein) and cert (ceramide transfer protein). We found that the Sac1 (Sac1 phosphatase), Osbp, and cert proteins are required for the reduction of PtdIns4P on autolysosomes. Loss of any of these proteins leads to defective macroautophagy/autophagy and neurodegeneration. Osbp, cert, and Sac1 are required for ER-Golgi contacts in fed cells. Our data establishes a new mode of organelle contact formation - the ER-Golgi contact machinery can be reused by ER-autolysosome contacts by re-locating PtdIns4P from the Golgi apparatus to autolysosomes when faced with starvation.Abbreviations: Atg1: Autophagy-related 1; Atg8: Autophagy-related 8; Atg9: Autophagy-related 9; Atg12: Autophagy-related 12; cert: ceramide transfer protein; Cp1/CathL: cysteine proteinase-1; CTL: control; ER: endoplasmic reticulum; ERMCS: ER-mitochondria contact site; fwd: four wheel drive; GM130: Golgi matrix protein 130 kD; Osbp: Oxysterol binding protein; PG: phagophore; PtdIns4K: phosphatidylinositol 4-kinase; Pi4KIIα: Phosphatidylinositol 4-kinase II α; Pi4KIIIα: Phosphatidylinositol 4-kinase III α; PtdIns4P: phosphatidylinositol-4-phosphate; PR: photoreceptor cell; RT: room temperature; Sac1: Sac1 phosphatase; Stv: starvation; Syx17: Syntaxin 17; TEM: transmission electron microscopy; VAP: VAMP-associated protein.

Functional Materials for Subcellular Targeting Strategies in Cancer Therapy: Progress and Prospects

Neoadjuvant and adjuvant therapies have made significant progress in cancer treatment. However, tumor adjuvant therapy still faces challenges due to the intrinsic heterogeneity of cancer, genomic instability, and the formation of an immunosuppressive tumor microenvironment. Functional materials possess unique biological properties such as long circulation times, tumor-specific targeting, and immunomodulation. The combination of functional materials with natural substances and nanotechnology has led to the development of smart biomaterials with multiple functions, high biocompatibilities, and negligible immunogenicities, which can be used for precise cancer treatment. Recently, subcellular structure-targeting functional materials have received particular attention in various biomedical applications including the diagnosis, sensing, and imaging of tumors and drug delivery. Subcellular organelle-targeting materials can precisely accumulate therapeutic agents in organelles, considerably reduce the threshold dosages of therapeutic agents, and minimize drug-related side effects. This review provides a systematic and comprehensive overview of the research progress in subcellular organelle-targeted cancer therapy based on functional nanomaterials. Moreover, it explains the challenges and prospects of subcellular organelle-targeting functional materials in precision oncology. The review will serve as an excellent cutting-edge guide for researchers in the field of subcellular organelle-targeted cancer therapy.

Targeting PP2A-dependent autophagy enhances sensitivity to ruxolitinib in JAK2V617F myeloproliferative neoplasms

The Janus kinase 2 (JAK2)-driven myeloproliferative neoplasms (MPNs) are chronic malignancies associated with high-risk complications and suboptimal responses to JAK inhibitors such as ruxolitinib. A better understanding of cellular changes induced by ruxolitinib is required to develop new combinatory therapies to improve treatment efficacy. Here, we demonstrate that ruxolitinib induced autophagy in JAK2^V617F cell lines and primary MPN patient cells through the activation of protein phosphatase 2A (PP2A). Inhibition of autophagy or PP2A activity along with ruxolitinib treatment reduced proliferation and increased the death of JAK2^V617F cells. Accordingly, proliferation and clonogenic potential of JAK2^V617F-driven primary MPN patient cells, but not of normal hematopoietic cells, were markedly impaired by ruxolitinib treatment with autophagy or PP2A inhibitor. Finally, preventing ruxolitinib-induced autophagy with a novel potent autophagy inhibitor Lys05 improved leukemia burden reduction and significantly prolonged the mice's overall survival compared with ruxolitinib alone. This study demonstrates that PP2A-dependent autophagy mediated by JAK2 activity inhibition contributes to resistance to ruxolitinib. Altogether, our data support that targeting autophagy or its identified regulator PP2A could enhance sensitivity to ruxolitinib of JAK2^V617F MPN cells and improve MPN patient care.

Mitophagy Promotes Resistance to BH3 Mimetics in Acute Myeloid Leukemia

BH3 mimetics are used as an efficient strategy to induce cell death in several blood malignancies, including acute myeloid leukemia (AML). Venetoclax, a potent BCL-2 antagonist, is used clinically in combination with hypomethylating agents for the treatment of AML. Moreover, MCL1 or dual BCL-2/BCL-xL antagonists are under investigation. Yet, resistance to single or combinatorial BH3-mimetic therapies eventually ensues. Integration of multiple genome-wide CRISPR/Cas9 screens revealed that loss of mitophagy modulators sensitizes AML cells to various BH3 mimetics targeting different BCL-2 family members. One such regulator is MFN2, whose protein levels positively correlate with drug resistance in patients with AML. MFN2 overexpression is sufficient to drive resistance to BH3 mimetics in AML. Insensitivity to BH3 mimetics is accompanied by enhanced mitochondria-endoplasmic reticulum interactions and augmented mitophagy flux, which acts as a prosurvival mechanism to eliminate mitochondrial damage. Genetic or pharmacologic MFN2 targeting synergizes with BH3 mimetics by impairing mitochondrial clearance and enhancing apoptosis in AML.

SIGNIFICANCE

AML remains one of the most difficult-to-treat blood cancers. BH3 mimetics represent a promising therapeutic approach to eliminate AML blasts by activating the apoptotic pathway. Enhanced mitochondrial clearance drives resistance to BH3 mimetics and predicts poor prognosis. Reverting excessive mitophagy can halt BH3-mimetic resistance in AML. This article is highlighted in the In This Issue feature, p. 1501.

Novel tumor therapy strategies targeting endoplasmic reticulum-mitochondria signal pathways

Organelles form tight connections through membrane contact sites, thereby cooperating to regulate homeostasis and cell function. Among them, the contact between endoplasmic reticulum (ER), the main intracellular calcium storage organelles, and mitochondria has been recognized for decades, and its main roles in the ion and lipid transport, ROS signaling, membrane dynamic changes and cellular metabolism are basically determined. At present, many tumor chemotherapeutic drugs rely on ER-mitochondrial calcium signal to function, but the mechanism of targeting resident molecules at the mitochondria-associated endoplasmic reticulum membranes (MAM) to sensitize traditional chemotherapy and the new tumor therapeutic targets identified based on the signal pathways on the MAM have not been thoroughly discussed. In this review, we highlight the key roles of various signaling pathways at the ER-mitochondria contact site in tumorigenesis and focus on novel anticancer therapy strategies targeting potential targets at this contact site.

Identification of DDIT4 as a potential prognostic marker associated with chemotherapeutic and immunotherapeutic response in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is the most heterogenous and aggressive subtype of breast cancer. Chemotherapy remains the standard treatment option for patients with TNBC owing to the unavailability of acceptable targets and biomarkers in clinical practice. Novel biomarkers and targets for patient stratification and treatment of TNBC are urgently needed. It has been reported that the overexpression of DNA damage-inducible transcript 4 gene (DDIT4) is associated with resistance to neoadjuvant chemotherapy and poor prognosis in patients with TNBC. In this study, we aimed to identify novel biomarkers and therapeutic targets using RNA sequencing (RNA-seq) and data mining using data from public databases.

METHODS

RNA sequencing (RNA-Seq) was performed to detect the different gene expression patterns in the human TNBC cell line HS578T treated with docetaxel or doxorubicin. Sequencing data were further analyzed by the R package "edgeR" and "clusterProfiler" to identify the profile of differentially expressed genes (DEGs) and annotate gene functions. The prognostic and predictive value of DDIT4 expression in patients with TNBC was further validated by published online data resources, including TIMER, UALCAN, Kaplan-Meier plotter, and LinkedOmics, and GeneMANIA and GSCALite were used to investigate the functional networks and hub genes related to DDIT4, respectively.

RESULTS

Through the integrative analyses of RNA-Seq data and public datasets, we observed the overexpression of DDIT4 in TNBC tissues and found that patients with DDIT4 overexpression showed poor survival outcomes. Notably, immune infiltration analysis showed that the levels of DDIT4 expression correlated negatively with the abundance of tumor-infiltrating immune cells and immune biomarker expression, but correlated positively with immune checkpoint molecules. Furthermore, DDIT4 and its hub genes (ADM, ENO1, PLOD1, and CEBPB) involved in the activation of apoptosis, cell cycle, and EMT pathways. Eventually, we found ADM, ENO1, PLOD1, and CEBPB showed poor overall survival in BC patients.

CONCLUSION

In this study, we found that DDIT4 expression is associated with the progression, therapeutic efficacy, and immune microenvironment of patients with TNBC, and DDIT4 would be as a potential prognostic biomarker and therapeutic target. These findings will help to identify potential molecular targets and improve therapeutic strategies against TNBC.

Dietary intake of household cadmium-contaminated rice caused genome-wide DNA methylation changes on gene/hubs related to metabolic disorders and cancers

Cadmium (Cd) contamination in food has raised broad concerns in food safety and human health. The toxicity of Cd to animals/humans have been widely reported, yet little is known about the health risk of dietary Cd intake at the epigenetic level. Here, we investigated the effect of a household Cd-contaminated rice (Cd-rice) on genome-wide DNA methylation (DNAm) changes in the model mouse. Feeding Cd-rice increased kidney Cd and urinary Cd concentrations compared with the Control rice (low-Cd rice), whereas supplementation of ethylenediamine tetraacetic acid iron sodium salt (NaFeEDTA) in the diet significantly increased urinary Cd and consequently decreased kidney Cd concentrations. Genome-wide DNAm sequencing revealed that dietary Cd-rice exposure caused the differentially methylated sites (DMSs), which were mainly located in the promoter (32.5%), downstream (32.5%), and intron (26.1%) regions of genes. Notably, Cd-rice exposure induced hypermethylation at the promoter sites of genes Caspase-8 and interleukin-1β (Il-1β), and consequently, their expressions were down-regulated. The two genes are critical in apoptosis and inflammation, respectively. In contrast, Cd-rice induced hypomethylation of the gene midline 1 (Mid1), which is vital to neurodevelopment. Furthermore, 'pathways in cancer' was significantly enriched as the leading canonical pathway. Supplementation of NaFeEDTA partly alleviated the toxic symptoms and DNAm alternations induced by Cd-rice exposure. These results highlight the broad effects of elevated dietary Cd intake on the level of DNAm, providing epigenetic evidence on the specific endpoints of health risks induced by Cd-rice exposure.

Advances in Understanding the Links between Metabolism and Autophagy in Acute Myeloid Leukemia: From Biology to Therapeutic Targeting

Autophagy is a highly conserved cellular degradation process that regulates cellular metabolism and homeostasis under normal and pathophysiological conditions. Autophagy and metabolism are linked in the hematopoietic system, playing a fundamental role in the self-renewal, survival, and differentiation of hematopoietic stem and progenitor cells, and in cell death, particularly affecting the cellular fate of the hematopoietic stem cell pool. In leukemia, autophagy sustains leukemic cell growth, contributes to survival of leukemic stem cells and chemotherapy resistance. The high frequency of disease relapse caused by relapse-initiating leukemic cells resistant to therapy occurs in acute myeloid leukemia (AML), and depends on the AML subtypes and treatments used. Targeting autophagy may represent a promising strategy to overcome therapeutic resistance in AML, for which prognosis remains poor. In this review, we illustrate the role of autophagy and the impact of its deregulation on the metabolism of normal and leukemic hematopoietic cells. We report updates on the contribution of autophagy to AML development and relapse, and the latest evidence indicating autophagy-related genes as potential prognostic predictors and drivers of AML. We review the recent advances in autophagy manipulation, combined with various anti-leukemia therapies, for an effective autophagy-targeted therapy for AML.

GPAM mediated lysophosphatidic acid synthesis regulates mitochondrial dynamics in acute myeloid leukemia

Metabolic alterations, especially in the mitochondria, play important roles in several kinds of cancers, including acute myeloid leukemia (AML). However, AML-specific molecular mechanisms that regulate mitochondrial dynamics remain elusive. Through the metabolite screening comparing CD34⁺ AML cells and healthy hematopoietic stem/progenitor cells, we identified enhanced lysophosphatidic acid (LPA) synthesis activity in AML. LPA is synthesized from glycerol-3-phosphate by glycerol-3-phosphate acyltransferases (GPATs), rate-limiting enzymes of the LPA synthesis pathway. Among the four isozymes of GPATs, glycerol-3-phosphate acyltransferases, mitochondrial (GPAM) was highly expressed in AML cells, and the inhibition of LPA synthesis by silencing GPAM or FSG67 (a GPAM-inhibitor) significantly impaired AML propagation through the induction of mitochondrial fission, resulting in the suppression of oxidative phosphorylation and the elevation of reactive oxygen species. Notably, inhibition of this metabolic synthesis pathway by FSG67 administration did not affect normal human hematopoiesis in vivo. Therefore, the GPAM-mediated LPA synthesis pathway from G3P represents a critical metabolic mechanism that specifically regulates mitochondrial dynamics in human AML, and GPAM is a promising potential therapeutic target.

Quantifying organellar ultrastructure in cryo-electron tomography using a surface morphometrics pipeline

Cellular cryo-electron tomography (cryo-ET) enables three-dimensional reconstructions of organelles in their native cellular environment at subnanometer resolution. However, quantifying ultrastructural features of pleomorphic organelles in three dimensions is challenging, as is defining the significance of observed changes induced by specific cellular perturbations. To address this challenge, we established a semiautomated workflow to segment organellar membranes and reconstruct their underlying surface geometry in cryo-ET. To complement this workflow, we developed an open-source suite of ultrastructural quantifications, integrated into a single pipeline called the surface morphometrics pipeline. This pipeline enables rapid modeling of complex membrane structures and allows detailed mapping of inter- and intramembrane spacing, curvedness, and orientation onto reconstructed membrane meshes, highlighting subtle organellar features that are challenging to detect in three dimensions and allowing for statistical comparison across many organelles. To demonstrate the advantages of this approach, we combine cryo-ET with cryo-fluorescence microscopy to correlate bulk mitochondrial network morphology (i.e., elongated versus fragmented) with membrane ultrastructure of individual mitochondria in the presence and absence of endoplasmic reticulum (ER) stress. Using our pipeline, we demonstrate ER stress promotes adaptive remodeling of ultrastructural features of mitochondria including spacing between the inner and outer membranes, local curvedness of the inner membrane, and spacing between mitochondrial cristae. We show that differences in membrane ultrastructure correlate to mitochondrial network morphologies, suggesting that these two remodeling events are coupled. Our pipeline offers opportunities for quantifying changes in membrane ultrastructure on a single-cell level using cryo-ET, opening new opportunities to define changes in ultrastructural features induced by diverse types of cellular perturbations.

Metabolic programming and immune suppression in the tumor microenvironment

Increased glucose metabolism and uptake are characteristic of many tumors and used clinically to diagnose and monitor cancer progression. In addition to cancer cells, the tumor microenvironment (TME) encompasses a wide range of stromal, innate, and adaptive immune cells. Cooperation and competition between these cell populations supports tumor proliferation, progression, metastasis, and immune evasion. Cellular heterogeneity leads to metabolic heterogeneity because metabolic programs within the tumor are dependent not only on the TME cellular composition but also on cell states, location, and nutrient availability. In addition to driving metabolic plasticity of cancer cells, altered nutrients and signals in the TME can lead to metabolic immune suppression of effector cells and promote regulatory immune cells. Here we discuss how metabolic programming of cells within the TME promotes tumor proliferation, progression, and metastasis. We also discuss how targeting metabolic heterogeneity may offer therapeutic opportunities to overcome immune suppression and augment immunotherapies.

Regulation of the immune system by the insulin receptor in health and disease

The signaling pathways downstream of the insulin receptor (InsR) are some of the most evolutionarily conserved pathways that regulate organism longevity and metabolism. InsR signaling is well characterized in metabolic tissues, such as liver, muscle, and fat, actively orchestrating cellular processes, including growth, survival, and nutrient metabolism. However, cells of the immune system also express the InsR and downstream signaling machinery, and there is increasing appreciation for the involvement of InsR signaling in shaping the immune response. Here, we summarize current understanding of InsR signaling pathways in different immune cell subsets and their impact on cellular metabolism, differentiation, and effector versus regulatory function. We also discuss mechanistic links between altered InsR signaling and immune dysfunction in various disease settings and conditions, with a focus on age related conditions, such as type 2 diabetes, cancer and infection vulnerability.

Aflatoxin B1 exposure triggers hepatic lipotoxicity via p53 and perilipin 2 interaction-mediated mitochondria-lipid droplet contacts: An in vitro and in vivo assessment

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins widely found in food contaminants, and its target organ is the liver. It poses a major food security and public health threat worldwide. However, the lipotoxicity mechanism of AFB1 exposure-induced liver injury remains unclear and requires further elucidation. Herein, we investigated the potential hepatic lipotoxicity of AFB1 exposure using in vitro and in vivo models to assess the public health hazards of high dietary AFB1 exposure. We demonstrated that low-dose of AFB1 (1.25 μM for 48 h, about one-fifth of the IC50 in HepG2 and HepaRG cells, IC50 are 5.995 μM and 5.266 μM, respectively) exposure significantly induced hepatic lipotoxicity, including abnormal lipid droplets (LDs) growth, mitochondria-LDs contacts increase, lipophagy disruption, and lipid accumulation. Mechanistically, we showed that AFB1 exposure promoted the mitochondrial p53 (mito-p53) and LDs-associated protein perilipin 2 (PLIN2) interaction-mediated mitochondria-LDs contacts, resulting in lipid accumulation in hepatocytes. Mito-p53-targeted inhibition, knockdown of PLIN2, and rapamycin application efficiently promoted the lysosome-dependent lipophagy and alleviated the hepatic lipotoxicity and liver injury induced by AFB1 exposure. Overall, our study found that mito-p53 and PLIN2 interaction mediates three organelles-mitochondria, LDs, and lysosomal networks to regulate lipid homeostasis in AFB1 exposure-induced hepatotoxicity, revealing how this unique trio of organelles works together and provides a novel insight into the targeted intervention in inter-organelle lipid sensing and trafficking for alleviating hazardous materials-induced hepatic lipotoxicity.

Exploring the mechanism of physcion-1-O-β-D-monoglucoside against acute lymphoblastic leukaemia based on network pharmacology and experimental validation

Objective

To explore the mechanism of PG against acute lymphoblastic leukaemia (ALL) by network pharmacology and experimental verification in vitro.

Methods

First, the biological activity of PG against B-ALL was determined by CCK-8 and flow cytometry. Then, the potential targets of PG were obtained from the PharmMapper database. ALL-related genes were collected from the GeneCards, OMIM and PharmGkb databases. The two datasets were intersected to obtain the target genes of PG in ALL. Then, protein interaction networks were constructed using the STRING database. The key targets were obtained by topological analysis of the network with Cytoscape 3.8.0 software. In addition, the mechanism of PG in ALL was confirmed by protein‒protein interaction, gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. Furthermore, molecular docking was carried out by AutoDock Vina. Finally, Western blotting was performed to confirm the effect of PG on NALM6 cells.

Results

PG inhibited the proliferation of NALM6 cells. A total of 174 antileukaemic targets of PG were obtained by network pharmacology. The key targets included AKT1, MAPK14, EGFR, ESR1, LCK, PTPN11, RHOA, IGF1, MDM2, HSP90AA1, HRAS, SRC and JAK2. Enrichment analysis found that PG had antileukaemic effects by regulating key targets such as MAPK signalling, and PG had good binding activity with MAPK14 protein (-8.9 kcal/mol). PG could upregulate the expression of the target protein p-P38, induce cell cycle arrest, and promote the apoptosis of leukaemia cells.

Conclusion

MAPK14 was confirmed to be one of the key targets and pathways of PG by network pharmacology and molecular experiments.

Mitochondrial fusion is a therapeutic vulnerability of acute myeloid leukemia

Mitochondrial metabolism recently emerged as a critical dependency in acute myeloid leukemia (AML). The shape of mitochondria is tightly regulated by dynamin GTPase proteins, which drive opposing fusion and fission forces to consistently adapt bioenergetics to the cellular context. Here, we showed that targeting mitochondrial fusion was a new vulnerability of AML cells, when assayed in patient-derived xenograft (PDX) models. Genetic depletion of mitofusin 2 (MFN2) or optic atrophy 1 (OPA1) or pharmacological inhibition of OPA1 (MYLS22) blocked mitochondrial fusion and had significant anti-leukemic activity, while having limited impact on normal hematopoietic cells ex vivo and in vivo. Mechanistically, inhibition of mitochondrial fusion disrupted mitochondrial respiration and reactive oxygen species production, leading to cell cycle arrest at the G₀/G₁ transition. These results nominate the inhibition of mitochondrial fusion as a promising therapeutic approach for AML.

Multifaceted roles of aerobic glycolysis and oxidative phosphorylation in hepatocellular carcinoma

Liver cancer is a common malignancy with high morbidity and mortality rates. Changes in liver metabolism are key factors in the development of primary hepatic carcinoma, and mitochondrial dysfunction is closely related to the occurrence and development of tumours. Accordingly, the study of the metabolic mechanism of mitochondria in primary hepatic carcinomas has gained increasing attention. A growing body of research suggests that defects in mitochondrial respiration are not generally responsible for aerobic glycolysis, nor are they typically selected during tumour evolution. Conversely, the dysfunction of mitochondrial oxidative phosphorylation (OXPHOS) may promote the proliferation, metastasis, and invasion of primary hepatic carcinoma. This review presents the current paradigm of the roles of aerobic glycolysis and OXPHOS in the occurrence and development of hepatocellular carcinoma (HCC). Mitochondrial OXPHOS and cytoplasmic glycolysis cooperate to maintain the energy balance in HCC cells. Our study provides evidence for the targeting of mitochondrial metabolism as a potential therapy for HCC.

The Regulators of Peroxisomal Acyl-Carnitine Shuttle CROT and CRAT Promote Metastasis in Melanoma

Circulating tumor cells are the key link between a primary tumor and distant metastases, but once in the bloodstream, loss of adhesion induces cell death. To identify the mechanisms relevant for melanoma circulating tumor cell survival, we performed RNA sequencing and discovered that detached melanoma cells and isolated melanoma circulating tumor cells rewire lipid metabolism by upregulating fatty acid (FA) transport and FA beta-oxidation‒related genes. In patients with melanoma, high expression of FA transporters and FA beta-oxidation enzymes significantly correlates with reduced progression-free and overall survival. Among the highest expressed regulators in melanoma circulating tumor cells were the carnitine transferases carnitine O-octanoyltransferase and carnitine acetyltransferase, which control the shuttle of peroxisome-derived medium-chain FAs toward mitochondria to fuel mitochondrial FA beta-oxidation. Knockdown of carnitine O-octanoyltransferase or carnitine acetyltransferase and short-term treatment with peroxisomal or mitochondrial FA beta-oxidation inhibitors thioridazine or ranolazine suppressed melanoma metastasis in mice. Carnitine O-octanoyltransferase and carnitine acetyltransferase depletion could be rescued by medium-chain FA supplementation, indicating that the peroxisomal supply of FAs is crucial for the survival of nonadherent melanoma cells. Our study identifies targeting the FA-based cross-talk between peroxisomes and mitochondria as a potential therapeutic opportunity to challenge melanoma progression. Moreover, the discovery of the antimetastatic activity of the Food and Drug Administration‒approved drug ranolazine carries translational potential.

Endoplasmic Reticulum Architecture and Inter-Organelle Communication in Metabolic Health and Disease

The endoplasmic reticulum (ER) is a key organelle involved in the regulation of lipid and glucose metabolism, proteostasis, Ca²⁺ signaling, and detoxification. The structural organization of the ER is very dynamic and complex, with distinct subdomains such as the nuclear envelope and the peripheral ER organized into ER sheets and tubules. ER also forms physical contact sites with all other cellular organelles and with the plasma membrane. Both form and function of the ER are highly adaptive, with a potent capacity to respond to transient changes in environmental cues such as nutritional fluctuations. However, under obesity-induced chronic stress, the ER fails to adapt, leading to ER dysfunction and the development of metabolic pathologies such as insulin resistance and fatty liver disease. Here, we discuss how the remodeling of ER structure and contact sites with other organelles results in diversification of metabolic function and how perturbations to this structural flexibility by chronic overnutrition contribute to ER dysfunction and metabolic pathologies in obesity.

Design, synthesis and pharmacological evaluation of β-carboline derivatives as potential antitumor agent via targeting autophagy

A series of novel β-carboline derivatives was designed, synthesized and evaluated as potential anticancer agents. Among them, compound 6g showed the most potent antiproliferative activity against the 786-0, HT-29 and 22RV1 cell lines with IC₅₀ values of 2.71, 2.02, and 3.86 μM, respectively. The antitumor efficiency of compound 6gin vivo was also evaluated, and the results revealed that compound 6g significantly suppressed tumor development and reduced tumor weight in a mouse colorectal cancer homograft model. Further investigation on mechanisms of action demonstrated that compound 6g inhibited HCT116 cell growth by stimulating the ATG5/ATG7-dependent autophagic pathway. These molecules might be served as candidates for further development of colorectal cancer therapy agent.

SH3GLB1-related autophagy mediates mitochondrial metabolism to acquire resistance against temozolomide in glioblastoma

Background

The mechanism by which glioblastoma evades temozolomide (TMZ)-induced cytotoxicity is largely unknown. We hypothesized that mitochondria plays a role in this process.

Methods

RNA transcriptomes were obtained from tumor samples and online databases. Expression of different proteins was manipulated using RNA interference or gene amplification. Autophagic activity and mitochondrial metabolism was assessed in vitro using the respective cellular and molecular assays. In vivo analysis were also carried out in this study.

Results

High SH3GLB1 gene expression was found to be associated with higher disease grading and worse survival profiles. Single-cell transcriptome analysis of clinical samples suggested that SH3GLB1 and the altered gene levels of oxidative phosphorylation (OXPHOS) were related to subsets expressing a tumor-initiating cell signature. The SH3GLB1 protein was regulated by promoter binding with Sp1, a factor associated with TMZ resistance. Downregulation of SH3GLB1 resulted in retention of TMZ susceptibility, upregulated p62, and reduced LC3B-II. Autophagy inhibition by SH3GLB1 deficiency and chloroquine resulted in attenuated OXPHOS expression. Inhibition of SH3GLB1 in resistant cells resulted in alleviation of TMZ-enhanced mitochondrial metabolic function, such as mitochondrial membrane potential, mitochondrial respiration, and ATP production. SH3GLB1 modulation could determine tumor susceptibility to TMZ. Finally, in animal models, resistant tumor cells with SH3GLB1 knockdown became resensitized to the anti-tumor effect of TMZ, including the suppression of TMZ-induced autophagy and OXPHOS.

Conclusions

SH3GLB1 promotes TMZ resistance via autophagy to alter mitochondrial function. Characterizing SH3GLB1 in glioblastoma may help develop new therapeutic strategies against this disease in the future.

Canonical and Noncanonical ER Stress-Mediated Autophagy Is a Bite the Bullet in View of Cancer Therapy

Cancer cells adapt multiple mechanisms to counter intense stress on their way to growth. Tumor microenvironment stress leads to canonical and noncanonical endoplasmic stress (ER) responses, which mediate autophagy and are engaged during proteotoxic challenges to clear unfolded or misfolded proteins and damaged organelles to mitigate stress. In these conditions, autophagy functions as a cytoprotective mechanism in which malignant tumor cells reuse degraded materials to generate energy under adverse growing conditions. However, cellular protection by autophagy is thought to be complicated, contentious, and context-dependent; the stress response to autophagy is suggested to support tumorigenesis and drug resistance, which must be adequately addressed. This review describes significant findings that suggest accelerated autophagy in cancer, a novel obstacle for anticancer therapy, and discusses the UPR components that have been suggested to be untreatable. Thus, addressing the UPR or noncanonical ER stress components is the most effective approach to suppressing cytoprotective autophagy for better and more effective cancer treatment.

Enhanced Sensitivity of Tumor Cells to Autophagy Inhibitors Using Fasting-Mimicking Diet and Targeted Lysosomal Delivery Nanoplatform

Autophagy is one of the key pathways for tumor cell survival and proliferation. Therefore, inhibition of autophagy has been extensively studied for cancer therapy. However, current autophagy inhibitors lack specificity and are ineffective in limiting tumor progression. Herein, we report a nanoplatform for tumor-site-targeted delivery of hydroxychloroquine (HCQ) using insulin-like growth factors 2 receptor (IGF2R)-targeted liposomes (iLipo-H). A fasting-mimicking diet (FMD) is used to increase the autophagy levels in tumor cells, thereby increasing the sensitivity of tumor cells to HCQ. In addition, FMD treatment upregulates the expression of IGF2R in tumor cells, but not normal cells. Consequently, iLipo-H nanoparticles efficiently accumulate at the tumor site under FMD condition. In vivo studies demonstrate that iLipo-H nanoparticles efficiently inhibit 4T1 tumor growth without obvious side effects, especially under FMD condition. This study provides a promising strategy to increase the sensitivity of tumor cells to autophagy inhibitors for effective cancer therapy.

Dysregulated hepatic lipid metabolism and gut microbiota associated with early-stage NAFLD in ASPP2-deficiency mice

BACKGROUND

Growing evidence indicates that lipid metabolism disorders and gut microbiota dysbiosis were related to the progression of non-alcoholic fatty liver disease (NAFLD). Apoptosis-stimulating p53 protein 2 (ASPP2) has been reported to protect against hepatocyte injury by regulating the lipid metabolism, but the mechanisms remain largely unknown. In this study, we investigate the effect of ASPP2 deficiency on NAFLD, lipid metabolism and gut microbiota using ASPP2 globally heterozygous knockout (ASPP2+/-) mice.

METHODS

ASPP2+/- Balb/c mice were fed with methionine and choline deficient diet for 3, 10 and 40 day to induce an early and later-stage of NAFLD, respectively. Fresh fecal samples were collected and followed by 16S rRNA sequencing. HPLC-MRM relative quantification analysis was used to identify changes in hepatic lipid profiles. The expression level of innate immunity-, lipid metabolism- and intestinal permeability-related genes were determined. A spearman's rank correlation analysis was performed to identify possible correlation between hepatic medium and long-chain fatty acid and gut microbiota in ASPP2-deficiency mice.

RESULTS

Compared with the WT control, ASPP2-deficiency mice developed moderate steatosis at day 10 and severe steatosis at day 40. The levels of hepatic long chain omega-3 fatty acid, eicosapentaenoic (EPA, 20:5 n-3) and docosahexaenoic (DHA, 22:6 n-3), were decreased at day 10 and increased at day 40 in ASPP+/- mice. Fecal microbiota analysis showed significantly increased alpha and beta diversity, as well as the composition of gut microbiota at the phylum, class, order, family, genus, species levels in ASPP2+/- mice. Moreover, ASPP-deficiency mice exhibited impaired intestinal barrier function, reduced expression of genes associated with chemical barrier (REG3B, REG3G, Lysozyme and IAP), and increased expression of innate immune components (TLR4 and TLR2). Furthermore, correlation analysis between gut microbiota and fatty acids revealed that EPA was significantly negatively correlated with Bifidobacterium family.

CONCLUSION

Our findings suggested that ASPP2-deficiency promotes the progression of NAFLD, alterations in fatty acid metabolism and gut microbiota dysbiosis. The long chain fatty acid EPA was significantly negatively correlated with Bifidobacterial abundance, which is a specific feature of NAFLD in ASPP2-deficiency mice. Totally, the results provide evidence for a mechanism of ASPP2 on dysregulation of fatty acid metabolism and gut microbiota dysbiosis.

Induction of the hepatic aryl hydrocarbon receptor by alcohol dysregulates autophagy and phospholipid metabolism via PPP2R2D

Disturbed lipid metabolism precedes alcoholic liver injury. Whether and how AhR alters degradation of lipids, particularly phospho-/sphingo-lipids during alcohol exposure, was not explored. Here, we show that alcohol consumption in mice results in induction and activation of aryl hydrocarbon receptor (AhR) in the liver, and changes the hepatic phospho-/sphingo-lipids content. The levels of kynurenine, an endogenous AhR ligand, are elevated with increased hepatic tryptophan metabolic enzymes in alcohol-fed mice. Either alcohol or kynurenine treatment promotes AhR activation with autophagy dysregulation via AMPK. Protein Phosphatase 2 Regulatory Subunit-Bdelta (Ppp2r2d) is identified as a transcriptional target of AhR. Consequently, PPP2R2D-dependent AMPKα dephosphorylation causes autophagy inhibition and mitochondrial dysfunction. Hepatocyte-specific AhR ablation attenuates steatosis, which is associated with recovery of phospho-/sphingo-lipids content. Changes of AhR targets are corroborated using patient specimens. Overall, AhR induction by alcohol inhibits autophagy in hepatocytes through AMPKα, which is mediated by Ppp2r2d gene transactivation, revealing an AhR-dependent metabolism of phospho-/sphingo-lipids.

Overcoming therapeutic resistance to platinum-based drugs by targeting Epithelial–Mesenchymal transition

Platinum-based drugs (PBDs), including cisplatin, carboplatin, and oxaliplatin, have been widely used in clinical practice as mainstay treatments for various types of cancer. Although there is firm evidence of notable achievements with PBDs in the management of cancers, the acquisition of resistance to these agents is still a major challenge to efforts at cure. The introduction of the epithelial-mesenchymal transition (EMT) concept, a critical process during embryonic morphogenesis and carcinoma progression, has offered a mechanistic explanation for the phenotypic switch of cancer cells upon PBD exposure. Accumulating evidence has suggested that carcinoma cells can enter a resistant state via induction of the EMT. In this review, we discussed the underlying mechanism of PBD-induced EMT and the current understanding of its role in cancer drug resistance, with emphasis on how this novel knowledge can be exploited to overcome PBD resistance via EMT-targeted compounds, especially those under clinical trials.

Low expression of the metabolism-related gene SLC25A21 predicts unfavourable prognosis in patients with acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease associated with poor outcomes. To identify AML-specific genes with prognostic value, we analysed transcriptome and clinical information from The Cancer Genome Atlas (TCGA) database, Gene Expression Omnibus (GEO) datasets, and Genotype-Tissue Expression (GTEx) project. The metabolism-related gene, SLC25A21 was found to be significantly downregulated in AML, and was associated with high white blood cell (WBC) counts, high pretrial blood (PB) and bone marrow (BM) blast abundance, FLT3 mutation, NPM1 mutation, and death events (all p value <0.05). We validated the expression of SLC25A21 in our clinical cohort, and found that SLC25A21 was downregulated in AML. Moreover, we identified low expression of SLC25A21 as an independent prognostic factor by univariate Cox regression (hazard ratio [HR]: 0.550; 95% Confidence interval [CI]: 0.358–0.845; p value = 0.006) and multivariate Cox regression analysis (HR: 0.341; 95% CI: 0.209–0.557; p value <0.05). A survival prediction nomogram was established with a C-index of 0.735, which indicated reliable prognostic prediction. Subsequently, based on the median SLC25A21 expression level, patients in the TCGA-LAML cohort were divided into low- and high-expression groups. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs highlighted growth factor binding, extracellular structure organization, cytokine‒cytokine receptor interaction, etc. The results of gene set enrichment analysis (GSEA) indicated that the epithelial-mesenchymal transition, KRAS signalling, oxidative phosphorylation, and reactive oxygen species pathways were enriched. Through gene coexpression and protein‒protein interaction (PPI) network analysis, we identified two hub genes, EGFR and COL1A2, which were linked to worse clinical outcomes. Furthermore, we found that lower SLC25A21 expression was closely associated with a significant reduction in the levels of infiltrating immune cells, which might be associated with immune escape of AML cells. A similar trend was observed for the expression of checkpoint genes (CTLA4, LAG3, TIGIT, and HAVCR2). Finally, drug sensitivity testing suggested that the low-expression SLC25A21 group is sensitive to doxorubicin, mitomycin C, linifanib but resistant to JQ1, belinostat, and dasatinib. Hence, our study demonstrated that a low expression level of SLC25A21 predicts an unfavourable prognosis in patients with AML.

Mitochondrial Porin Is Involved in Development, Virulence, and Autophagy in Fusarium graminearum

Mitochondrial porin, the voltage-dependent anion-selective channel (VDAC), is the most abundant protein in the outer membrane, and is critical for the exchange of metabolites and phospholipids in yeast and mammals. However, the functions of porin in phytopathogenic fungi are not known. In this study, we characterized a yeast porin orthologue, Fgporin, in Fusarium graminearum. The deletion of Fgporin resulted in defects in hyphal growth, conidiation, and perithecia development. The Fgporin deletion mutant showed reduced virulence, deoxynivalenol production, and lipid droplet accumulation. In addition, the Fgporin deletion mutant exhibited morphological changes and the dysfunction of mitochondria, and also displayed impaired autophagy in the non-nitrogen medium compared to the wild type. Yeast two-hybrid and bimolecular fluorescence complementation assays indicated that Fgporin interacted with FgUps1/2, but not with FgMdm35. Taken together, these results suggest that Fgporin is involved in hyphal growth, asexual and sexual reproduction, virulence, and autophagy in F. graminearum.

Endoplasmic reticulum-mitochondria miscommunication is an early and causal trigger of hepatic insulin resistance and steatosis

BACKGROUND & AIMS

Hepatic insulin resistance in obesity and type 2 diabetes was recently associated with endoplasmic reticulum (ER)-mitochondria miscommunication. These contact sites (mitochondria-associated membranes: MAMs) are highly dynamic and involved in many functions; however, whether MAM dysfunction plays a causal role in hepatic insulin resistance and steatosis is not clear. Thus, we aimed to determine whether and how organelle miscommunication plays a role in the onset and progression of hepatic metabolic impairment.

METHODS

We analyzed hepatic ER-mitochondria interactions and calcium exchange in a time-dependent and reversible manner in mice with diet-induced obesity. Additionally, we used recombinant adenovirus to express a specific organelle spacer or linker in mouse livers, to determine the causal impact of MAM dysfunction on hepatic metabolic alterations.

RESULTS

Disruption of ER-mitochondria interactions and calcium exchange is an early event preceding hepatic insulin resistance and steatosis in mice with diet-induced obesity. Interestingly, an 8-week reversal diet concomitantly reversed hepatic organelle miscommunication and insulin resistance in obese mice. Mechanistically, disrupting structural and functional ER-mitochondria interactions through the hepatic overexpression of the organelle spacer FATE1 was sufficient to impair hepatic insulin action and glucose homeostasis. In addition, FATE1-mediated organelle miscommunication disrupted lipid-related mitochondrial oxidative metabolism and induced hepatic steatosis. Conversely, reinforcement of ER-mitochondria interactions through hepatic expression of a synthetic linker prevented diet-induced glucose intolerance after 4 weeks' overnutrition. Importantly, ER-mitochondria miscommunication was confirmed in the liver of obese patients with type 2 diabetes, and correlated with glycemia, HbA1c and HOMA-IR index.

CONCLUSIONS

ER-mitochondria miscommunication is an early causal trigger of hepatic insulin resistance and steatosis, and can be reversed by switching to a healthy diet. Thus, targeting MAMs could help to restore metabolic homeostasis.

LAY SUMMARY

The literature suggests that interactions between the endoplasmic reticulum and mitochondria could play a role in hepatic insulin resistance and steatosis during chronic obesity. In the present study, we reappraised the time-dependent regulation of hepatic endoplasmic reticulum-mitochondria interactions and calcium exchange, investigating reversibility and causality, in mice with diet-induced obesity. We also assessed the relevance of our findings to humans. We show that organelle miscommunication is an early causal trigger of hepatic insulin resistance and steatosis that can be improved by nutritional strategies.

Mitochondria-Associated Endoplasmic Reticulum Membranes: Inextricably Linked with Autophagy Process

Mitochondria-associated membranes (MAMs), physical connection sites between the endoplasmic reticulum (ER) and the outer mitochondrial membrane (OMM), are involved in numerous cellular processes, such as calcium ion transport, lipid metabolism, autophagy, ER stress, mitochondria morphology, and apoptosis. Autophagy is a highly conserved intracellular process in which cellular contents are delivered by double-membrane vesicles, called autophagosomes, to the lysosomes for destruction and recycling. Autophagy, typically triggered by stress, eliminates damaged or redundant protein molecules and organelles to maintain regular cellular activity. Dysfunction of MAMs or autophagy is intimately associated with various diseases, including aging, cardiovascular, infections, cancer, multiple toxic agents, and some genetic disorders. Increasing evidence has shown that MAMs play a significant role in autophagy development and maturation. In our study, we concentrated on two opposing functions of MAMs in autophagy: facilitating the formation of autophagosomes and inhibiting autophagy. We recognized the link between MAMs and autophagy in the occurrence and progression of the diseases and therefore collated and summarized the existing intrinsic molecular mechanisms. Furthermore, we draw attention to several crucial data and open issues in the area that may be helpful for further study.

ER-mitochondria contact sites; a multifaceted factory for Ca2+ signaling and lipid transport

Membrane contact sites (MCS) between organelles of eukaryotic cells provide structural integrity and promote organelle homeostasis by facilitating intracellular signaling, exchange of ions, metabolites and lipids and membrane dynamics. Cataloguing MCS revolutionized our understanding of the structural organization of a eukaryotic cell, but the functional role of MSCs and their role in complex diseases, such as cancer, are only gradually emerging. In particular, the endoplasmic reticulum (ER)-mitochondria contacts (EMCS) are key effectors of non-vesicular lipid trafficking, thereby regulating the lipid composition of cellular membranes and organelles, their physiological functions and lipid-mediated signaling pathways both in physiological and diseased conditions. In this short review, we discuss key aspects of the functional complexity of EMCS in mammalian cells, with particular emphasis on their role as central hubs for lipid transport between these organelles and how perturbations of these pathways may favor key traits of cancer cells.

Ubiquitin-specific peptidase 10 ameliorates hepatic steatosis in nonalcoholic steatohepatitis model by restoring autophagic activity

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a critical event in the progression of nonalcoholic fatty liver disease (NAFLD). Steatosis induces lipotoxicity, driving the transition of simple fatty liver (NAFL) to NASH. Autophagy affects NAFLD by improving steatosis.

AIM

To investigate whether ubiquitin-specific peptidase (USP)10 alleviates hepatic steatosis through autophagy.

METHODS

A methionine-choline-deficient diet (MCDD) and choline-deficient diet (CDD) were used to model rodent NASH and NAFL, respectively. HepG2 cells were treated with palmitic acid to model hepatocellular steatosis. A viral carrier was used to regulate the USP10 level. Real-time fluorescence quantitative polymerase chain reaction, western blotting, histology, and electron microscopy were used to detect autophagic activity and steatosis.

RESULTS

In vivo, a time-dependent correlation of USP10 and autophagic activity in the liver was found during NAFLD (including NAFL and NASH) modeling. After 8 weeks of modeling, the autophagic activity of NASH was lower than that of the healthy controls and those with NAFL. USP10 could promote autophagy-related pathways and molecules and increase the synthesis of autophagosomes in NASH, improving steatosis, inflammation, and fibrosis. In vitro, autophagy inhibitors reversed the lipid-lowering effect of USP10 without decreasing the level of fatty acid β-oxidation.

CONCLUSION

USP10 ameliorated histological steatosis, inflammation, and fibrosis. USP10 alleviated hepatic steatosis in NASH in an autophagy-dependent manner.

Cell death regulation by MAMs: from molecular mechanisms to therapeutic implications in cardiovascular diseases

The endoplasmic reticulum (ER) and mitochondria are interconnected intracellular organelles with vital roles in the regulation of cell signaling and function. While the ER participates in a number of biological processes including lipid biosynthesis, Ca²⁺ storage and protein folding and processing, mitochondria are highly dynamic organelles governing ATP synthesis, free radical production, innate immunity and apoptosis. Interplay between the ER and mitochondria plays a crucial role in regulating energy metabolism and cell fate control under stress. The mitochondria-associated membranes (MAMs) denote physical contact sites between ER and mitochondria that mediate bidirectional communications between the two organelles. Although Ca²⁺ transport from ER to mitochondria is vital for mitochondrial homeostasis and energy metabolism, unrestrained Ca²⁺ transfer may result in mitochondrial Ca²⁺ overload, mitochondrial damage and cell death. Here we summarize the roles of MAMs in cell physiology and its impact in pathological conditions with a focus on cardiovascular disease. The possibility of manipulating ER-mitochondria contacts as potential therapeutic approaches is also discussed.