bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2022‒09‒11
twenty-six papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Biochim Biophys Acta Bioenerg. 2022 Sep 02. pii: S0005-2728(22)00385-1. [Epub ahead of print]1863(8): 148915
      Although the development of chemoresistance is multifactorial, active chemotherapeutic efflux driven by upregulations in ATP binding cassette (ABC) transporters are commonplace. Chemotherapeutic efflux pumps, like ABCB1, couple drug efflux to ATP hydrolysis and thus potentially elevate cellular demand for ATP resynthesis. Elevations in both mitochondrial content and cellular respiration are common phenotypes accompanying many models of cancer cell chemoresistance, including those dependent on ABCB1. The present study set out to characterize potential mitochondrial remodeling commensurate with ABCB1-dependent chemoresistance, as well as investigate the impact of ABCB1 activity on mitochondrial respiratory kinetics. To do this, comprehensive bioenergetic phenotyping was performed across ABCB1-dependent chemoresistant cell models and compared to chemosensitive controls. In doxorubicin (DOX) resistant ovarian cancer cells, the combination of both increased mitochondrial content and enhanced respiratory complex I (CI) boosted intrinsic oxidative phosphorylation (OXPHOS) power output. With respect to ABCB1, acute ABCB1 inhibition partially normalized intact basal mitochondrial respiration between chemosensitive and chemoresistant cells, suggesting that active ABCB1 contributes to mitochondrial remodeling in favor of enhanced OXPHOS. Interestingly, while enhanced OXPHOS power output supported ABCB1 drug efflux when DOX was present, in the absence of chemotherapeutic stress, enhanced OXPHOS power output was associated with reduced tumorigenicity.
    Keywords:  ABCB1; Mitochondria; OXPHOS; cancer chemoresistance; doxorubicin; ovarian cancer
  2. Hum Cell. 2022 Sep 05.
      Mitochondrial respiration and metabolism play an important role in the occurrence and development of colorectal cancer (CRC). In this study, we identified a functional pool of SLIT-ROBO Rho GTPase-activating protein 2 (SRGAP2) in the mitochondria of CRC cells as an important regulator of CRC chemosensitivity. We found that SRGAP2 levels were increased in CRC cells in comparison to normal colorectal cells. Loss of mitochondrial SRGAP2 led to significant decrease in mitochondrial respiration and strongly sensitized the CRC cells to chemotherapy drugs. Mechanistically, SRGAP2 physically interacts with mitochondrial complex I and positively modulates its activity. In particular, chemosensitization upon SRGAP2 loss was phenocopied by the treatment of complex I inhibitor. Thus, our results demonstrate that SRGAP2 functions as a key regulator of CRC chemosensitivity, identifying SRGAP2 as a promising therapeutic target to enhance the efficacy of chemotherapy in CRC.
    Keywords:  Chemosensitivity; Colorectal cancer; Mitochondrial complex I activity; Mitochondrial respiration
  3. Int J Mol Sci. 2022 Aug 25. pii: 9655. [Epub ahead of print]23(17):
      The oxidative phosphorylation (OXPHOS) system couples the transfer of electrons to oxygen with pumping of protons across the inner mitochondrial membrane, ensuring the ATP production. Evidence suggests that respiratory chain complexes may also assemble into supramolecular structures, called supercomplexes (SCs). The SCs appear to increase the efficiency/capacity of OXPHOS and reduce the reactive oxygen species (ROS) production, especially that which is produced by complex I. Studies suggest a mutual regulation between complex I and SCs, while SCs organization is important for complex I assembly/stability, complex I is involved in the supercomplex formation. Complex I is a pacemaker of the OXPHOS system, and it has been shown that the PKA-dependent phosphorylation of some of its subunits increases the activity of the complex, reducing the ROS production. In this work, using in ex vivo and in vitro models, we show that the activation of cAMP/PKA cascade resulted in an increase in SCs formation associated with an enhanced capacity of electron flux and ATP production rate. This is also associated with the phosphorylation of the NDUFS4 subunit of complex I. This aspect highlights the key role of complex I in cellular energy production.
    Keywords:  NDUFS4; cAMP/PKA; complex I; mitochondria; mitochondrial supercomplexes
  4. iScience. 2022 Sep 16. 25(9): 104923
      Although it is reported that mitochondria-localized nuclear transcription factors (TFs) regulate mitochondrial processes such as apoptosis and mitochondrial transcription/respiration, the functions and mechanisms of mitochondrial dynamics regulated by mitochondria-localized nuclear TFs are yet to be fully characterized. Here, we identify STAT6 as a mitochondrial protein that is localized in the outer membrane of mitochondria (OMM). STAT6 in OMM inhibits mitochondrial fusion by blocking MFN2 dimerization. This implies that STAT6 has a critical role in mitochondrial dynamics. Moreover, mitochondrial accumulation of STAT6 in response to hypoxic conditions reveals that STAT6 is a regulator of mitochondrial processes including fusion/fission mechanisms.
    Keywords:  Biological sciences; Molecular biology; Molecular interaction; Natural sciences
  5. Redox Biol. 2022 Aug 30. pii: S2213-2317(22)00224-5. [Epub ahead of print]56 102452
      PURPOSE: Bile acids are steroid synthesized in liver, which are essential for fat emulsification, cholesterol excretion and gut microbial homeostasis. However, the role of bile acids in leukemia progression remains unclear. We aim at exploring the effects and mechanisms of chenodeoxycholic acid (CDCA), a type of bile acids, on acute myeloid leukemia (AML) progression.RESULTS: Here, we found that CDCA was decreased in feces and plasma of AML patients, positively correlated with the diversity of gut microbiota, and negatively associated with AML prognosis. We further demonstrated that CDCA suppressed AML progression both in vivo and in vitro. Mechanistically, CDCA bound to mitochondria to cause mitochondrial morphology damage containing swelling and reduction of cristae, decreased mitochondrial membrane potential and elevated mitochondrial calcium level, which resulted in the production of excessive reactive oxygen species (ROS). Elevated ROS further activated p38 MAPK signaling pathway, which collaboratively promoted the accumulation of lipid droplets (LDs) through upregulating the expression of the diacylglycerol O-acyltransferase 1 (DGAT1). As the consequence of the abundance of ROS and LDs, lipid peroxidation was enhanced in AML cells. Moreover, we uncovered that CDCA inhibited M2 macrophage polarization and suppressed the proliferation-promoting effects of M2 macrophages on AML cells in co-cultured experiments.
    CONCLUSION: Our findings demonstrate that CDCA suppresses AML progression through synergistically promoting LDs accumulation and lipid peroxidation via ROS/p38 MAPK/DGAT1 pathway caused by mitochondrial dysfunction in leukemia cells and inhibiting M2 macrophage polarization.
    Keywords:  Acute myeloid leukemia; Chenodeoxycholic acid; Lipid droplets; Mitochondria
  6. J Cell Biol. 2022 Oct 03. pii: e202205104. [Epub ahead of print]221(10):
      Mitochondria are dynamic organelles that play essential roles in cell growth and survival. Processes of fission and fusion are critical for the distribution, segregation, and maintenance of mitochondria and their genomes (mtDNA). While recent work has revealed the significance of mitochondrial organization for mtDNA maintenance, the impact of mtDNA perturbations on mitochondrial dynamics remains less understood. Here, we develop a tool to induce mitochondria-specific DNA damage using a mitochondrial-targeted base modifying bacterial toxin, DarT. Following damage, we observe dynamic reorganization of mitochondrial networks, likely driven by mitochondrial dysfunction. Changes in the organization are associated with the loss of mtDNA, independent of mitophagy. Unexpectedly, perturbation to exonuclease function of mtDNA replicative polymerase, Mip1, results in rapid loss of mtDNA. Our data suggest that, under damage, partitioning of defective mtDNA and organelle are de-coupled, with emphasis on mitochondrial segregation independent of its DNA. Together, our work underscores the importance of genome maintenance on mitochondrial function, which can act as a modulator of organelle organization and segregation.
  7. Cancers (Basel). 2022 Aug 31. pii: 4260. [Epub ahead of print]14(17):
      Colorectal cancer (CRC) is among the deadliest cancers worldwide, with metastasis being the main cause of patient mortality. During CRC progression the complex tumor ecosystem changes in its composition at virtually every stage. However, clonal dynamics and associated niche-dependencies at these stages are unknown. Hence, it is of importance to utilize models that faithfully recapitulate human CRC to define its clonal dynamics. We used an optical barcoding approach in mouse-derived organoids (MDOs) that revealed niche-dependent clonal selection. Our findings highlight that clonal selection is controlled by a site-specific niche, which critically contributes to cancer heterogeneity and has implications for therapeutic intervention.
    Keywords:  clonal selection; colorectal cancer; metastasis; mouse models; mouse-derived organoids; niche; orthotopic transplantation; tumor heterogeneity
  8. Chemistry. 2022 Sep 09.
      Phomoxanthone A is a naturally occurring molecule and a powerful anti-cancer agent, although its mechanism of action is unknown. To facilitate the determination of its biological target(s) we used affinity-based labelling using a phomoxanthone A probe. Labelled proteins were pulled down, subjected to chemoproteomics analysis using LC-MS/MS and ATP synthase was identified as a likely target. Mitochondrial ATP synthase was validated in cultured cells lysates and in live intact cells. Our studies show sixty percent inhibition of ATP synthase by 260  m M phomoxanthone A.
    Keywords:  Medicinal Chemistry; Natural products; cancer; photo affinity labelling
  9. J Invest Dermatol. 2022 Sep 01. pii: S0022-202X(22)01890-5. [Epub ahead of print]
      Circulating tumor cells (CTCs) are the key link between a primary tumor and distant metastases, but once in the bloodstream loss of adhesion induces cell death. To identify mechanisms relevant for melanoma CTC survival we performed RNAseq and discovered that detached melanoma cells and isolated melanoma CTCs rewire lipid metabolism by up-regulating fatty acid transport and fatty acid beta-oxidation (FAO) related genes. In melanoma patients high expression of fatty acid transporters and FAO enzymes significantly correlates with reduced progression free and overall survival. Amongst the highest expressed regulators in melanoma CTCs were the carnitine-transferases CROT and CRAT, which control the shuttle of peroxisome derived medium-chain fatty acids (MCFAs) towards mitochondria to fuel mitochondrial FAO. Knockdown of CROT or CRAT and short-term treatment with peroxisomal or mitochondrial FAO inhibitors thioridazine or ranolazine suppressed melanoma metastasis in mice. CROT and CRAT depletion could be rescued by MCFA supplementation, indicating that the peroxisomal supply of fatty acids is crucial for the survival of non-adherent melanoma cells. Our study identifies targeting the fatty acid based cross-talk between peroxisomes and mitochondria as a potential therapeutic opportunity to challenge melanoma progression. Moreover, the discovery of the anti-metastatic activity of the FDA-approved drug ranolazine carries translational potential.
    Keywords:  CRAT; CROT; anoikis; fatty acid oxidation; melanoma; metastasis
  10. ACS Appl Bio Mater. 2022 Sep 06.
      Mitochondrion is a multifunctional organelle in a cell, and it is one of the important targets of antitumor therapy. Conventional mitochondrial targeting strategies can hardly distinguish the mitochondria in cancer cells from those in normal cells, which might raise a concern about the biosafety. Recent studies suggest that a relatively high temperature of mitochondria exists in cancer cells. We named it tumor intrinsic mitochondrial overheating (TIMO). By taking advantage of the difference in mitochondrial temperatures between cancer cells and normal cells, therapeutic agents can be specifically delivered to the mitochondria in cancer cells. Here we will briefly overview the mitochondria-targeted delivery strategies. In addition, the recent discovery of hot mitochondria in cancer cells and the development of mitochondrial temperature-responsive delivery systems for antitumor therapy will be reviewed.
    Keywords:  cancer; drug delivery; mitochondria; nanomedicine; temperature
  11. Cancer Res. 2022 Sep 09. pii: CAN-22-0237. [Epub ahead of print]
      Exercise prevents cancer incidence and recurrence, yet the underlying mechanism behind this relationship remains mostly unknown. Here we report that exercise induces metabolic reprogramming of internal organs that increases nutrient demand and protects against metastatic colonization by limiting nutrient availability to the tumor, generating an exercise-induced metabolic shield. Proteomic and ex vivo metabolic capacity analyses of murine internal organs revealed that exercise induces catabolic processes, glucose uptake, mitochondrial activity, and GLUT expression. Proteomic analysis of routinely active human subject plasma demonstrated increased carbohydrate utilization following exercise. Epidemiological data from a 20-year prospective study of a large human cohort of initially cancer-free participants revealed that exercise prior to cancer initiation had a modest impact on cancer incidence in low metastatic stages but significantly reduced the likelihood of highly metastatic cancer. In three models of melanoma in mice, exercise prior to cancer injection significantly protected against metastases in distant organs. The protective effects of exercise were dependent on mTOR activity, and inhibition of the mTOR pathway with rapamycin treatment ex vivo reversed the exercise-induced metabolic shield. Under limited glucose conditions, active stroma consumed significantly more glucose at the expense of the tumor. Collectively, these data suggest a clash between the metabolic plasticity of cancer and exercise-induced metabolic reprogramming of the stroma, raising an opportunity to block metastasis by challenging the metabolic needs of the tumor.
  12. Cell Metab. 2022 Aug 30. pii: S1550-4131(22)00353-9. [Epub ahead of print]
      Adipocytes transfer mitochondria to macrophages in white and brown adipose tissues to maintain metabolic homeostasis. In obesity, adipocyte-to-macrophage mitochondria transfer is impaired, and instead, adipocytes release mitochondria into the blood to induce a protective antioxidant response in the heart. We found that adipocyte-to-macrophage mitochondria transfer in white adipose tissue is inhibited in murine obesity elicited by a lard-based high-fat diet, but not a hydrogenated-coconut-oil-based high-fat diet, aging, or a corn-starch diet. The long-chain fatty acids enriched in lard suppress mitochondria capture by macrophages, diverting adipocyte-derived mitochondria into the blood for delivery to other organs, such as the heart. The depletion of macrophages rapidly increased the number of adipocyte-derived mitochondria in the blood. These findings suggest that dietary lipids regulate mitochondria uptake by macrophages locally in white adipose tissue to determine whether adipocyte-derived mitochondria are released into systemic circulation to support the metabolic adaptation of distant organs in response to nutrient stress.
    Keywords:  CD36; EXT1; aging; beige fat; brown adipose tissue; cell-free mitochondria; fatty acids; heparan sulfate; horizontal mitochondria transfer; intercellular mitochondria transfer; lipids; macrophage; mitochondria; obesity; palmitate; white adipose tissue
  13. Front Immunol. 2022 ;13 897862
      Multiple myeloma is an incurable cancer of plasma cells that is predominantly located in the bone marrow. Multiple myeloma cells are characterized by distinctive biological features that are intricately linked to their core function, the assembly and secretion of large amounts of antibodies, and their diverse interactions with the bone marrow microenvironment. Here, we provide a concise and introductory discussion of major metabolic hallmarks of plasma cells and myeloma cells, their roles in myeloma development and progression, and how they could be exploited for therapeutic purposes. We review the role of glucose consumption and catabolism, assess the dependency on glutamine to support key metabolic processes, and consider metabolic adaptations in drug-resistant myeloma cells. Finally, we examine the complex metabolic effects of proteasome inhibitors on myeloma cells and the extracellular matrix, and we explore the complex relationship between myeloma cells and bone marrow adipocytes.
    Keywords:  bone marrow (BM) adipocytes; cancer biology; metabolism; multiple myeloma; plasma cell; proteasome; proteostasis
  14. J Proteome Res. 2022 Sep 08.
      It is generally believed that vascular endothelial cells (VECs) rely on glycolysis instead of the tricarboxylic acid (TCA) cycle under both normoxic and hypoxic conditions. However, the metabolic pattern of human umbilical vein endothelial cells (HUVECs) under extreme ischemia (hypoxia and nutrient deprivation) needs to be elucidated. We initiated a lethal ischemic model of HUVECs, performed proteomics and bioinformatics, and verified the metabolic pattern shift of HUVECs. Ischemic HUVECs displayed extensive aerobic respiration, including upregulation of the TCA cycle and mitochondrial respiratory chain in mitochondria and downregulation of glycolysis in cytoplasm. The TCA cycle was enhanced while the cell viability was decreased through the citrate synthase pathway when substrates of the TCA cycle (acetate and/or pyruvate) were added and vice versa when inhibitors of the TCA cycle (palmitoyl-CoA and/or avidin) were applied. The inconsistency of the TCA cycle level and cell viability suggested that the extensive TCA cycle can keep cells alive yet generate toxic substances that reduce cell viability. The data revealed that HUVECs depend on "ischemic TCA cycle" instead of glycolysis to keep cells alive under lethal ischemic conditions, but consideration must be given to relieve cell injury.
    Keywords:  citrate synthase; glycolysis; ischemia; tricarboxylic acid cycle; vascular endothelial cells
  15. Eur J Med Res. 2022 Sep 08. 27(1): 172
      Pancreatic adenocarcinoma (PDAC) and lung cancer are expected to represent the most common cancer types worldwide until 2030. Under typical conditions, mitochondria provide the bulk of the energy needed to sustain cell life. For that inhibition of mitochondrial complex ΙΙ (CΙΙ) and ubiquinone oxidoreductase with natural treatments may represent a promising cancer treatment option. A naturally occurring flavonoid with biological anti-cancer effects is chyrsin. Due to their improved bioavailability, penetrative power, and efficacy, chitosan-chrysin nano-formulations (CCNPs) are being used in medicine with increasing frequency. Chitosan (cs) is also regarded as a highly versatile and adaptable polymer. The cationic properties of Cs, together with its biodegradability, high adsorption capacity, biocompatibility, effect on permeability, ability to form films, and adhesive properties, are advantages. In addition, Cs is thought to be both safe and economical. CCNPs may indeed be therapeutic candidates in the treatment of pancreatic adenocarcinoma (PDAC) and lung cancer by blocking succinate ubiquinone oxidoreductase.
    Keywords:  Cancer; Chitosan; Chrysin; Mitochondria; Succinate dehydrogenase
  16. Anal Chem. 2022 Sep 08.
      Mitochondrial glutathione (mGSH) is both the cause of the oxidative damage and a mechanism for maintaining the redox homeostasis in mitochondria. To effectively measure mGSH dynamics in living cells, we have developed a new FRET-based nanosensor by immobilizing rhodamine B into dendritic mesoporous silica nanoparticles and installing GSH probes and mitochondria-targeting motifs onto the surface of nanoparticles. The result shows that these nanosensors show efficient FRET and a full reversibility and rapid response (<10 s) to GSH in the range of 0.5-20 mM, due to their unique nanostructure and well-overlapped spectra. The excellent photostability and low cytotoxicity make them an effective means for monitoring mGSH concentration in real time. When the mGSH nanosensors are used for quantitatively measuring mGSH variations under glucose deprivation stimulation in HeLa cells, they successfully prove themselves a useful tool for mitochondrial redox activity studies.
  17. Front Bioeng Biotechnol. 2022 ;10 870193
      Cartilage and other skeletal soft tissues heal poorly after injury, in part due to their lack of vascularity and low metabolic rate. No pharmacologic approaches have proven effective in preventing chronic degenerative disease after joint injury. Mesenchymal stromal cells (MSCs) have been investigated for their ability to treat pain associated with osteoarthritis (OA) and preserve articular cartilage. Limitations of MSCs include variability in cell phenotype, low engraftment and retention rates, and inconsistent clinical outcomes. Therefore, acellular biologic therapies such as extracellular vesicles (EVs) are currently being investigated. MSC-derived EVs have been found to replicate many of the therapeutic effects of their cells of origin, but the mechanisms driving this remain unclear. Recent evidence in non-orthopedic tissues suggests MSCs can rescue injured cells by donating mitochondria, restoring mitochondrial function in recipient cells, preserving cell viability, and promoting tissue repair. Our group hypothesized that MSCs package mitochondria for export into EVs, and that these so-called "mitoEVs" could provide a delivery strategy for cell-free mitochondria-targeted therapy. Therefore, the goals of this study were to: 1) characterize the vesicle fractions of the MSCs secretome with respect to mitochondrial cargoes, 2) determine if MSC-EVs contain functional mitochondria, and 3) determine if chondrocytes can take up MSC-derived mitoEVs. We isolated exosome, microvesicle, and vesicle-free fractions from MSC-conditioned media. Using a combination of dynamic light scattering and nanoparticle tracking, we determined that MSC-EV populations fall within the three size categories typically used to classify EVs (exosomes, microvesicles, apoptotic bodies). Fluorescent nanoparticle tracking, immunoblotting, and flow cytometry revealed that mitochondrial cargoes are abundant across all EV size populations, and mitoEVs are nearly ubiquitous among the largest EVs. Polarization staining indicated a subset of mitoEVs contain functional mitochondria. Finally, flow cytometry and fluorescent imaging confirmed uptake of mitoEVs by chondrocytes undergoing rotenone/antimycin-induced mitochondrial dysfunction. These data indicate that MSCs package intact, functional mitochondria into EVs, which can be transferred to chondrocytes in the absence of direct cell-cell interactions. This work suggests intercellular transfer of healthy MT to chondrocytes could represent a new, acellular approach to augment mitochondrial content and function in poorly-healing avascular skeletal soft tissues.
    Keywords:  MSCs; mitoEVs; mitochondria; mitochondrial transfer; regenerative orthobiologic; secretome
  18. Biomed Res Int. 2022 ;2022 7626405
      Methods: Cell viability, glycolytic activity, Annexin V-PE binding activity, reactive oxygen species levels, mitochondrial membrane potential, ATP content, Western blot analysis, and spheroid viability were measured for this study.Results: Acidic pH-tolerant prostate cancer cells, PC-3AcT and DU145AcT, increased cytotoxicity with ERK1/2 inhibition in a curcumin concentration-dependent manner at concentrations that resulted in >90% cell viability in normal prostate epithelial HPrEC cells. ERK1/2 inhibition by curcumin and/or PD98059 suppressed cell growth, reduced glucose consumption, and downregulated the expression of key regulatory enzymes in glucose metabolism including hexokinases, phosphofructokinase, and pyruvate dehydrogenase. In addition, these compounds caused loss of mitochondrial membrane potential with increased intracellular ROS levels, decreased levels of complexes I, III, and IV in the mitochondrial electron transport chain, and cellular ATP depletion, leading to upregulation of marker proteins in apoptosis (cleaved caspase-3 and cleaved PARP) and necroptosis (p-MLKL and p-RIP3). The results of curcumin and/or PD98059 treatment in 3D cultures showed similar trends to those in 2D cultures.
    Conclusion: Taken together, the results provide mechanistic evidence for the antiglycolytic and cytotoxic roles of curcumin through inhibition of the MEK/ERK signaling pathway in prostate carcinoma cells preadapted to acidic conditions.
  19. PLoS One. 2022 ;17(9): e0273766
      Cancer cachexia is accompanied by muscle atrophy, sharing multiple common catabolic pathways with sarcopenia, including mitochondrial dysfunction. This study investigated gene expression from skeletal muscle tissues of older healthy adults, who are at risk of age-related sarcopenia, to identify potential gene biomarkers whose dysregulated expression and protein interference were involved in non-small cell lung cancer (NSCLC). Screening of the literature resulted in 14 microarray datasets (GSE25941, GSE28392, GSE28422, GSE47881, GSE47969, GSE59880 in musculoskeletal ageing; GSE118370, GSE33532, GSE19804, GSE18842, GSE27262, GSE19188, GSE31210, GSE40791 in NSCLC). Differentially expressed genes (DEGs) were used to construct protein-protein interaction networks and retrieve clustering gene modules. Overlapping module DEGs were ranked based on 11 topological algorithms and were correlated with prognosis, tissue expression, and tumour purity in NSCLC. The analysis revealed that the dysregulated expression of the mammalian mitochondrial ribosomal proteins, Mitochondrial Ribosomal Protein S26 (MRPS26), Mitochondrial Ribosomal Protein S17 (MRPS17), Mitochondrial Ribosomal Protein L18 (MRPL18) and Mitochondrial Ribosomal Protein L51 (MRPL51) were linked to reduced survival and tumour purity in NSCLC while tissue expression of the same genes followed an opposite direction in healthy older adults. These results support a potential link between the mitochondrial ribosomal microenvironment in ageing muscle and NSCLC. Further studies comparing changes in sarcopenia and NSCLC associated cachexia are warranted.
  20. Nutrients. 2022 Aug 31. pii: 3605. [Epub ahead of print]14(17):
      The mitochondrial malate aspartate shuttle system (MAS) maintains the cytosolic NAD+/NADH redox balance, thereby sustaining cytosolic redox-dependent pathways, such as glycolysis and serine biosynthesis. Human disease has been associated with defects in four MAS-proteins (encoded by MDH1, MDH2, GOT2, SLC25A12) sharing a neurological/epileptic phenotype, as well as citrin deficiency (SLC25A13) with a complex hepatopathic-neuropsychiatric phenotype. Ketogenic diets (KD) are high-fat/low-carbohydrate diets, which decrease glycolysis thus bypassing the mentioned defects. The same holds for mitochondrial pyruvate carrier (MPC) 1 deficiency, which also presents neurological deficits. We here describe 40 (18 previously unreported) subjects with MAS-/MPC1-defects (32 neurological phenotypes, eight citrin deficiency), describe and discuss their phenotypes and genotypes (presenting 12 novel variants), and the efficacy of KD. Of 13 MAS/MPC1-individuals with a neurological phenotype treated with KD, 11 experienced benefits-mainly a striking effect against seizures. Two individuals with citrin deficiency deceased before the correct diagnosis was established, presumably due to high-carbohydrate treatment. Six citrin-deficient individuals received a carbohydrate-restricted/fat-enriched diet and showed normalisation of laboratory values/hepatopathy as well as age-adequate thriving. We conclude that patients with MAS-/MPC1-defects are amenable to dietary intervention and that early (genetic) diagnosis is key for initiation of proper treatment and can even be lifesaving.
    Keywords:  AGC1; Citrullinemia; aspartate glutamate carrier 1 deficiency; citrin deficiency; epilepsy; hepatopathy; mitochondrial disease; modified Atkins diet; serine; treatment
  21. EMBO Mol Med. 2022 Sep 05. e16029
      Glycogen dysregulation is a hallmark of aging, and aberrant glycogen drives metabolic reprogramming and pathogenesis in multiple diseases. However, glycogen heterogeneity in healthy and diseased tissues remains largely unknown. Herein, we describe a method to define spatial glycogen architecture in mouse and human tissues using matrix-assisted laser desorption/ionization mass spectrometry imaging. This assay provides robust and sensitive spatial glycogen quantification and architecture characterization in the brain, liver, kidney, testis, lung, bladder, and even the bone. Armed with this tool, we interrogated glycogen spatial distribution and architecture in different types of human cancers. We demonstrate that glycogen stores and architecture are heterogeneous among diseases. Additionally, we observe unique hyperphosphorylated glycogen accumulation in Ewing sarcoma, a pediatric bone cancer. Using preclinical models, we correct glycogen hyperphosphorylation in Ewing sarcoma through genetic and pharmacological interventions that ablate in vivo tumor growth, demonstrating the clinical therapeutic potential of targeting glycogen in Ewing sarcoma.
    Keywords:  Ewing sarcoma; MALDI imaging; glycogen; glycogen storage disease; spatial metabolism
  22. Nat Commun. 2022 Sep 06. 13(1): 4981
      Lactate is a key metabolite produced from glycolytic metabolism of glucose molecules, yet it also serves as a primary carbon fuel source for many cell types. In the tumor-immune microenvironment, effect of lactate on cancer and immune cells can be highly complex and hard to decipher, which is further confounded by acidic protons, a co-product of glycolysis. Here we show that lactate is able to increase stemness of CD8+ T cells and augments anti-tumor immunity. Subcutaneous administration of sodium lactate but not glucose to mice bearing transplanted MC38 tumors results in CD8+ T cell-dependent tumor growth inhibition. Single cell transcriptomics analysis reveals increased proportion of stem-like TCF-1-expressing CD8+ T cells among intra-tumoral CD3+ cells, a phenotype validated by in vitro lactate treatment of T cells. Mechanistically, lactate inhibits histone deacetylase activity, which results in increased acetylation at H3K27 of the Tcf7 super enhancer locus, leading to increased Tcf7 gene expression. CD8+ T cells in vitro pre-treated with lactate efficiently inhibit tumor growth upon adoptive transfer to tumor-bearing mice. Our results provide evidence for an intrinsic role of lactate in anti-tumor immunity independent of the pH-dependent effect of lactic acid, and might advance cancer immune therapy.
  23. JCI Insight. 2022 Sep 08. pii: e161820. [Epub ahead of print]7(17):
      Fibrolamellar hepatocellular carcinoma (FLC) is a rare and often lethal liver cancer with no proven effective systemic therapy. Inhibition of the antiapoptotic protein BCL-XL was found to synergize with a variety of systemic therapies in vitro using cells dissociated from patient-derived xenografts (PDX) of FLC or cells dissociated directly from surgical patient resections. As BCL-XL is physiologically expressed in platelets, prior efforts to leverage this vulnerability in other cancers have been hampered by severe thrombocytopenia. To overcome this toxicity, we treated FLC models with DT2216, a proteolysis targeting chimera (PROTAC) that directs BCL-XL for degradation via the von Hippel-Lindau (VHL) E3 ligase, which is minimally expressed in platelets. The combination of irinotecan and DT2216 in vitro on cells directly acquired from patients or in vivo using several xenografts derived from patients with FLC demonstrated remarkable synergy and at clinically achievable doses not associated with significant thrombocytopenia.
    Keywords:  Apoptosis inhibitors; Drug therapy; Hepatology; Liver cancer; Oncology
  24. Cell Mol Immunol. 2022 Sep 08.
      Graft-versus-host disease (GVHD) significantly contributes to patient morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HSCT). Sphingosine-1-phosphate (S1P) signaling is involved in the biogenetic processes of different immune cells. In the current study, we demonstrated that recipient sphingosine kinase 1 (Sphk1), but not Sphk2, was required for optimal S1PR1-dependent donor T-cell allogeneic responses by secreting S1P. Using genetic and pharmacologic approaches, we demonstrated that inhibition of Sphk1 or S1PR1 substantially attenuated acute GVHD (aGVHD) while retaining the graft-versus-leukemia (GVL) effect. At the cellular level, the Sphk1/S1P/S1PR1 pathway differentially modulated the alloreactivity of CD4+ and CD8+ T cells; it facilitated T-cell differentiation into Th1/Th17 cells but not Tregs and promoted CD4+ T-cell infiltration into GVHD target organs but was dispensable for the CTL activity of allogeneic CD8+ T cells. At the molecular level, the Sphk1/S1P/S1PR1 pathway augmented mitochondrial fission and increased mitochondrial mass in allogeneic CD4+ but not CD8+ T cells by activating the AMPK/AKT/mTOR/Drp1 pathway, providing a mechanistic basis for GVL maintenance when S1P signaling was inhibited. For translational purposes, we detected the regulatory efficacy of pharmacologic inhibitors of Sphk1 and S1PR1 in GVHD induced by human T cells in a xenograft model. Our study provides novel mechanistic insight into how the Sphk1/S1P/S1PR1 pathway modulates T-cell alloreactivity and validates Sphk1 or S1PR1 as a therapeutic target for the prevention of GVHD and leukemia relapse. This novel strategy may be readily translated into the clinic to benefit patients with hematologic malignancies and disorders.
    Keywords:  GVHD; GVL; S1P; S1PR; Sphk1; mitochondrial fission