bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2022‒06‒26
forty-six papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Proc Natl Acad Sci U S A. 2022 Jun 28. 119(26): e2121987119
      Mechanisms of defense against ferroptosis (an iron-dependent form of cell death induced by lipid peroxidation) in cellular organelles remain poorly understood, hindering our ability to target ferroptosis in disease treatment. In this study, metabolomic analyses revealed that treatment of cancer cells with glutathione peroxidase 4 (GPX4) inhibitors results in intracellular glycerol-3-phosphate (G3P) depletion. We further showed that supplementation of cancer cells with G3P attenuates ferroptosis induced by GPX4 inhibitors in a G3P dehydrogenase 2 (GPD2)-dependent manner; GPD2 deletion sensitizes cancer cells to GPX4 inhibition-induced mitochondrial lipid peroxidation and ferroptosis, and combined deletion of GPX4 and GPD2 synergistically suppresses tumor growth by inducing ferroptosis in vivo. Mechanistically, inner mitochondrial membrane-localized GPD2 couples G3P oxidation with ubiquinone reduction to ubiquinol, which acts as a radical-trapping antioxidant to suppress ferroptosis in mitochondria. Taken together, these results reveal that GPD2 participates in ferroptosis defense in mitochondria by generating ubiquinol.
    Keywords:  GPD2; cell death; ferroptosis; lipid peroxidation; mitochondria
  2. Curr Biol. 2022 Jun 20. pii: S0960-9822(22)00765-5. [Epub ahead of print]32(12): R618-R623
      Mitochondria are central to cellular metabolism. They provide intermediate metabolites that are used in biosynthetic pathways and they process diet-derived nutrients into the energy-rich compound ATP. Mitochondrial ATP biosynthesis is a marvel of thermodynamic efficiency. Via the tricarboxylic acid cycle (TCA) and fatty acid β-oxidation, mitochondria extract electrons from dietary carbon compounds and pass them to nucleotides that ultimately deliver them to the respiratory chain complexes located in invaginations in the inner mitochondrial membrane (IMM) known as cristae. The respiratory chain complexes donate electrons in stepwise redox reactions to molecular oxygen and, with the exception of complex II, use the liberated energy to pump protons across the proton-impermeable IMM, generating a proton electrochemical gradient. This gradient is then utilized by the ATP synthase, which, in a rotary mechanism, catalyzes the formation of the high-energy γ-phosphate chemical bond between ADP and inorganic phosphate. The conversion of the chemical energy of carbon compounds into a physical, vectorial form of energy (the electrochemical gradient) maximizes the yield of the ATP biosynthetic process and is perhaps one of the foundations of life as we know it.
  3. Cancers (Basel). 2022 Jun 16. pii: 2983. [Epub ahead of print]14(12):
      Despite the development of metabolism-based therapy for a variety of malignancies, resistance to single-agent treatment is common due to the metabolic plasticity of cancer cells. Improved understanding of how malignant cells rewire metabolic pathways can guide the rational selection of combination therapy to circumvent drug resistance. Here, we show that human T-ALL cells shift their metabolism from oxidative decarboxylation to reductive carboxylation when the TCA cycle is disrupted. The α-ketoglutarate dehydrogenase complex (KGDHC) in the TCA cycle regulates oxidative decarboxylation by converting α-ketoglutarate (α-KG) to succinyl-CoA, while isocitrate dehydrogenase (IDH) 1 and 2 govern reductive carboxylation. Metabolomics flux analysis of T-ALL reveals enhanced reductive carboxylation upon genetic depletion of the E2 subunit of KGDHC, dihydrolipoamide-succinyl transferase (DLST), mimicking pharmacological inhibition of the complex. Mechanistically, KGDHC dysfunction causes increased demethylation of nuclear DNA by α-KG-dependent dioxygenases (e.g., TET demethylases), leading to increased production of both IDH1 and 2. Consequently, dual pharmacologic inhibition of the TCA cycle and TET demethylases demonstrates additive efficacy in reducing the tumor burden in zebrafish xenografts. These findings provide mechanistic insights into how T-ALL develops resistance to drugs targeting the TCA cycle and therapeutic strategies to overcome this resistance.
    Keywords:  DNA demethylation; T-cell acute lymphoblastic leukemia; TCA cycle; oxidative phosphorylation; reductive carboxylation; α-ketoglutarate
  4. Free Radic Biol Med. 2022 Jun 16. pii: S0891-5849(22)00452-X. [Epub ahead of print]188 92-102
      The rates of formation of superoxide and hydrogen peroxide at different electron-donating sites in isolated mitochondria are critically dependent on the substrates that are added, through their effects on the reduction level of each site and the components of the protonmotive force. However, in intact cells the acute effects of added substrates on different sites of cytosolic and mitochondrial hydrogen peroxide production are unclear. Here we tested the effects of substrate addition on cytosolic and mitochondrial hydrogen peroxide release from intact AML12 liver cells. In 30-min starved cells replete with endogenous substrates, addition of glucose, fructose, palmitate, alanine, leucine or glutamine had no effect on the rate or origin of cellular hydrogen peroxide release. However, following 150-min starvation of the cells to deplete endogenous glycogen (and other substrates), cellular hydrogen peroxide production, particularly from NADPH oxidases (NOXs), was decreased, GSH/GSSH ratio increased, and antioxidant gene expression was unchanged. Addition of glucose or glutamine (but not the other substrates) increased hydrogen peroxide release. There were similar relative increases from each of the three major sites of production: mitochondrial sites IQ and IIIQo, and cytosolic NOXs. Glucose supplementation also restored ATP production and mitochondrial NAD reduction level, suggesting that the increased rates of hydrogen peroxide release from the mitochondrial sites were driven by increases in the protonmotive force and the degree of reduction of the electron transport chain. Long-term (24 h) glucose or glutamine deprivation also diminished hydrogen peroxide release rate, ATP production rate and (for glucose deprivation) NAD reduction level. We conclude that the rates of superoxide and hydrogen peroxide production from mitochondrial sites in liver cells are insensitive to extra added substrates when endogenous substrates are not depleted, but these rates are decreased when endogenous substrates are lowered by 150 min of starvation, and can be enhanced by restoring glucose or glutamine supply through improvements in mitochondrial energetic state.
    Keywords:  Liver; Mitochondria; NOX; ROS; Site III(Qo); Site IQ
  5. Mol Carcinog. 2022 Jun 20.
      Primary tumors evolve metabolic mechanisms favoring glycolysis for adenosine triphosphate (ATP) generation and antioxidant defenses. In contrast, metastatic cells frequently depend on mitochondrial respiration and oxidative phosphorylation (OxPhos). This reliance of metastatic cells on OxPhos can be exploited using drugs that target mitochondrial metabolism. Therefore, therapeutic agents that act via diverse mechanisms, including the activation of signaling pathways that promote the production of reactive oxygen species (ROS) and/or a reduction in antioxidant defenses may elevate oxidative stress and inhibit tumor cell survival. In this review, we will provide (1) a mechanistic analysis of function-selective extracellular signal-regulated kinase-1/2 (ERK1/2) inhibitors that inhibit cancer cells through enhanced ROS, (2) a review of the role of mitochondrial ATP synthase in redox regulation and drug resistance, (3) a rationale for inhibiting ERK signaling and mitochondrial OxPhos toward the therapeutic goal of reducing tumor metastasis and treatment resistance. Recent reports from our laboratories using metastatic melanoma and breast cancer models have shown the preclinical efficacy of novel and rationally designed therapeutic agents that target ERK1/2 signaling and mitochondrial ATP synthase, which modulate ROS events that may prevent or treat metastatic cancer. These findings and those of others suggest that targeting a tumor's metabolic requirements and vulnerabilities may inhibit metastatic pathways and tumor growth. Approaches that exploit the ability of therapeutic agents to alter oxidative balance in tumor cells may be selective for cancer cells and may ultimately have an impact on clinical efficacy and safety. Elucidating the translational potential of metabolic targeting could lead to the discovery of new approaches for treatment of metastatic cancer.
    Keywords:  cancer metastasis; drug mechanisms; kinase signaling; mitochondria; reactive oxygen species; targeting OxPhos
  6. Methods Mol Biol. 2022 ;2493 153-165
      Mitochondria are cellular organelles that play an essential role in eukaryotes, producing the energy needed for a cell to survive. Beyond the ~3.2 Gb of nuclear genomic DNA, each human cell has hundreds of mitochondria which carry one or a few copies of the 16.5 kb circular mitochondria DNA (mtDNA). Despite its small size, the circular genome encodes 37 genes, including 13 proteins that generate respiratory chain complexes together with other proteins of nuclear origin. Similar to nuclear genome, mtDNA in cancer cells frequently harbor somatically acquired alterations. Whole-genome or whole-exome sequencing of the tumor and its matched normal tissues (frequently blood or adjacent non-tumor tissues) enables sensitive and efficient detection of somatic mtDNA mutations. Because each cancer cell commonly carries hundreds to thousands of mtDNA copies, detection of mtDNA mutations is dependent on the heteroplasmic level of each mutation. Here, we describe strategies to accurately identify somatic mtDNA mutations in cancer genome studies.
    Keywords:  Bioinformatics; Genome sequencing; Genomics; Heteroplasmy; Mitochondria; Next-generation sequencing; Somatic mutations
  7. Cancers (Basel). 2022 Jun 10. pii: 2862. [Epub ahead of print]14(12):
      Cancer cells often display impaired mitochondrial function, reduced oxidative phosphorylation, and augmented aerobic glycolysis (Warburg effect) to fulfill their bioenergetic and biosynthetic needs. Caveolin-1 (CAV1) is a scaffolding protein that promotes cancer cell migration, invasion, and metastasis in a manner dependent on CAV1 phosphorylation on tyrosine-14 (pY14). Here, we show that CAV1 expression increased glycolysis rates, while mitochondrial respiration was reduced by inhibition of the mitochondrial complex IV. These effects correlated with increased reactive oxygen species (ROS) levels that favored CAV1-induced migration and invasion. Interestingly, pY14-CAV1 promoted the metabolic switch associated with increased migration/invasion and augmented ROS-inhibited PTP1B, a phosphatase that controls pY14 levels. Finally, the glycolysis inhibitor 2-deoxy-D-glucose reduced CAV1-enhanced migration in vitro and metastasis in vivo of murine melanoma cells. In conclusion, CAV1 promotes the Warburg effect and ROS production, which inhibits PTP1B to augment CAV1 phosphorylation on tyrosine-14, thereby increasing the metastatic potential of cancer cells.
    Keywords:  PTP1B; caveolin-1; metabolic switch; metastasis; mitochondrial complex IV; tyrosine-14 phosphorylation
  8. Free Radic Biol Med. 2022 Jun 16. pii: S0891-5849(22)00238-6. [Epub ahead of print]
      Attachment of cargo molecules to lipophilic triphenylphosphonium (TPP+) cations is a widely applied strategy for mitochondrial targeting. We previously demonstrated that the vitamin E-derived antioxidant Trolox increases the levels of active mitochondrial complex I (CI), the first complex of the electron transport chain (ETC), in primary human skin fibroblasts (PHSFs) of Leigh Syndrome (LS) patients with isolated CI deficiency. Primed by this finding, we here studied the cellular effects of mitochondria-targeted Trolox (MitoE10), mitochondria-targeted ubiquinone (MitoQ10) and their mitochondria-targeting moiety decylTPP (C10-TPP+). Chronic treatment (96 h) with these molecules of PHSFs from a healthy subject and an LS patient with isolated CI deficiency (NDUFS7-V122 M mutation) did not greatly affect cell number. Unexpectedly, this treatment reduced CI levels/activity, lowered the amount of ETC supercomplexes, inhibited mitochondrial oxygen consumption, increased extracellular acidification, altered mitochondrial morphology and stimulated hydroethidine oxidation. We conclude that the mitochondria-targeting decylTPP moiety is responsible for the observed effects and advocate that every study employing alkylTPP-mediated mitochondrial targeting should routinely include control experiments with the corresponding alkylTPP moiety.
    Keywords:  Complex I; Glycolysis; Mitochondrial targeting; Supercomplexes; Trolox; decylTPP
  9. Redox Biol. 2022 Jun 17. pii: S2213-2317(22)00140-9. [Epub ahead of print]54 102368
      Cell models of cardiac ischemia-reperfusion (IR) injury are essential to facilitate understanding, but current monolayer cell models poorly replicate the in vivo IR injury that occurs within a three-dimensional tissue. Here we show that this is for two reasons: the residual oxygen present in many cellular hypoxia models sustains mitochondrial oxidative phosphorylation; and the loss of lactate from cells into the incubation medium during ischemia enables cells to sustain glycolysis. To overcome these limitations, we incubated isolated adult mouse cardiomyocytes anoxically while inhibiting lactate efflux. These interventions recapitulated key markers of in vivo ischemia, notably the accumulation of succinate and the loss of adenine nucleotides. Upon reoxygenation after anoxia the succinate that had accumulated during anoxia was rapidly oxidized in association with extensive mitochondrial superoxide/hydrogen peroxide production and cell injury, mimicking reperfusion injury. This cell model will enable key aspects of cardiac IR injury to be assessed in vitro.
    Keywords:  Cardiomyocytes; Hydrogen peroxide; Ischemia-reperfusion injury; Metabolism; Mitochondria
  10. Commun Biol. 2022 Jun 23. 5(1): 620
      Imbalanced mitochondrial dNTP pools are known players in the pathogenesis of multiple human diseases. Here we show that, even under physiological conditions, dGTP is largely overrepresented among other dNTPs in mitochondria of mouse tissues and human cultured cells. In addition, a vast majority of mitochondrial dGTP is tightly bound to NDUFA10, an accessory subunit of complex I of the mitochondrial respiratory chain. NDUFA10 shares a deoxyribonucleoside kinase (dNK) domain with deoxyribonucleoside kinases in the nucleotide salvage pathway, though no specific function beyond stabilizing the complex I holoenzyme has been described for this subunit. We mutated the dNK domain of NDUFA10 in human HEK-293T cells while preserving complex I assembly and activity. The NDUFA10E160A/R161A shows reduced dGTP binding capacity in vitro and leads to a 50% reduction in mitochondrial dGTP content, proving that most dGTP is directly bound to the dNK domain of NDUFA10. This interaction may represent a hitherto unknown mechanism regulating mitochondrial dNTP availability and linking oxidative metabolism to DNA maintenance.
  11. Acta Physiol (Oxf). 2022 Jun 20. e13852
      Mitochondria are complex small organelles of eukaryotic cells and build the cellular source of energy. Several morphological features of mitochondria such as the double membrane and the circular DNA structure support the thesis that they originated from a prokaryotic eubacterial ancestor that has been taken up by the eukaryotic cell very early during the eukaryotic evolution. Since this "uptake-event" mitochondria were integrated into cellular processes and regulation which was realized by the transfer of mitochondrial genes into the host cell genome. 1 The mitochondrial genome reduced to for instance 13 encoded protein subunits of the oxidative phosphorylation system in human cells. Mitochondria offer energy for the cell by producing about 95% of cellular ATP.2 Nutrients, mainly pyruvate from the glycolysis enter the tricarboxylic acid cycle and undergo iterative oxidations whereas electrons are transferred to the reduction equivalents NADH and FADH2 . These redox equivalents transport electrons to the electron transport chain located on the inner mitochondrial membrane and protons are pumped into the perimembranal room. The F1 F0 -ATP synthase generates ATP driven by protons flowing down an electrochemical gradient during a process named oxidative phosphorylation. As a byproduct reactive oxygen species are generated. Mitochondria are more than simple batteries for the cell, they are furthermore involved in numerous vital cellular processes, among them are calcium homeostasis, cell death, fatty acid oxidation, reactive oxygen species (ROS) signaling, cholesterol synthesis and nucleotide synthesis, topics that are frequently published in Acta Physiologica.
  12. Science. 2022 Jun 24. 376(6600): eabh2841
      Tumor necrosis factor (TNF) is a critical host resistance factor against tuberculosis. However, excess TNF produces susceptibility by increasing mitochondrial reactive oxygen species (mROS), which initiate a signaling cascade to cause pathogenic necrosis of mycobacterium-infected macrophages. In zebrafish, we identified the mechanism of TNF-induced mROS in tuberculosis. Excess TNF in mycobacterium-infected macrophages elevates mROS production by reverse electron transport (RET) through complex I. TNF-activated cellular glutamine uptake leads to an increased concentration of succinate, a Krebs cycle intermediate. Oxidation of this elevated succinate by complex II drives RET, thereby generating the mROS superoxide at complex I. The complex I inhibitor metformin, a widely used antidiabetic drug, prevents TNF-induced mROS and necrosis of Mycobacterium tuberculosis-infected zebrafish and human macrophages; metformin may therefore be useful in tuberculosis therapy.
  13. Nat Metab. 2022 Jun 23.
      Production of oxidized biomass, which requires regeneration of the cofactor NAD+, can be a proliferation bottleneck that is influenced by environmental conditions. However, a comprehensive quantitative understanding of metabolic processes that may be affected by NAD+ deficiency is currently missing. Here, we show that de novo lipid biosynthesis can impose a substantial NAD+ consumption cost in proliferating cancer cells. When electron acceptors are limited, environmental lipids become crucial for proliferation because NAD+ is required to generate precursors for fatty acid biosynthesis. We find that both oxidative and even net reductive pathways for lipogenic citrate synthesis are gated by reactions that depend on NAD+ availability. We also show that access to acetate can relieve lipid auxotrophy by bypassing the NAD+ consuming reactions. Gene expression analysis demonstrates that lipid biosynthesis strongly anti-correlates with expression of hypoxia markers across tumor types. Overall, our results define a requirement for oxidative metabolism to support biosynthetic reactions and provide a mechanistic explanation for cancer cell dependence on lipid uptake in electron acceptor-limited conditions, such as hypoxia.
  14. ACS Appl Mater Interfaces. 2022 Jun 21.
      Atomically precise gold nanoclusters (AuNCs) are an emerging class of quantum-sized nanomaterials with well-defined molecular structures and unique biophysical properties, rendering them highly attractive for biological applications. We set out to study the impact of different ligand shells of atomically similar nanoclusters on cellular recognition and response. To understand the effects of atomically precise nanoclusters with identical composition on cells, we selected two different water-soluble gold nanoclusters protected with captopril (Capt) and glutathione (GSH): Au25(Capt)18 (CNC) and Au25(GSH)18 (GNC), respectively. We demonstrated that a change of the ligand of the cluster completely changes its biological functions. Whereas both nanoclusters are capable of internalization, only CNC exhibits remarkable cytotoxicity, more specifically on cancer cells. CNC shows enhanced cytotoxicity by inhibiting the OXPHOS of mitochondria, possibly by inhibiting the ATP synthase complex of the electron transport chain (ETC), and by initiating the leakage of electrons into the mitochondrial lumen. The resulting increase in both mitochondrial and total cellular ROS triggers cell death indicated by the appearance of cellular markers of apoptosis. Remarkably, this effect of nanoclusters is independent of any external light source excitation. Our findings point to the prevailing importance of the ligand shell for applications of atomically precise nanoclusters in biology and medicine.
    Keywords:  atomically precise nanoclusters; captopril (Capt); cytotoxicity; glutathione (GSH); oxidative phosphorylation (OXPHOS); reactive oxygen species (ROS)
  15. Int J Mol Sci. 2022 Jun 15. pii: 6653. [Epub ahead of print]23(12):
      Leukemia is one of the most common primary malignancies of the hematologic system in both children and adults and remains a largely incurable or relapsing disease. The elucidation of disease subtypes based on mutational profiling has not improved clinical outcomes. IDH1/2 are critical enzymes of the TCA cycle that produces α-ketoglutarate (αKG). However, their mutated version is well reported in various cancer types, including leukemia, which produces D-2 hydroxyglutarate (D-2HG), an oncometabolite. Recently, some studies have shown that wild-type IDH1 is highly expressed in non-small cell lung carcinoma (NSCLC), primary glioblastomas (GBM), and several hematological malignancies and is correlated with disease progression. This work shows that the treatment of wild-type IDH1 leukemia cells with a specific IDH1 inhibitor shifted leukemic cells toward glycolysis from the oxidative phosphorylation (OXPHOS) phenotype. We also noticed a reduction in αKG in treated cells, possibly suggesting the inhibition of IDH1 enzymatic activity. Furthermore, we found that IDH1 inhibition reduced the metabolites related to one-carbon metabolism, which is essential for maintaining global methylation in leukemic cells. Finally, we observed that metabolic alteration in IDH1 inhibitor-treated leukemic cells promoted reactive oxygen species (ROS) formation and the loss of mitochondrial membrane potential, leading to apoptosis in leukemic cells. We showed that targeting wild-type IDH1 leukemic cells promotes metabolic alterations that can be exploited for combination therapies for a better outcome.
    Keywords:  OXPHOS; glutamine metabolism; metabolomics; reactive oxygen species; wild-type IDH1
  16. BMB Rep. 2022 Jun 21. pii: 5590. [Epub ahead of print]
      MitoNEET, a mitochondrial outer membrane protein containing the Asn-Glu-Glu-Thr (NEET) sequence, controls the formation of intermitochondrial junctions and confers autophagy resistance. Moreover, mitoNEET as a mitochondrial substrate undergoes ubiquitination by activated Parkin during the initiation of mitophagy. Therefore, mitoNEET is linked to the regulation of autophagy and mitophagy. Mitophagy is the selective removal of the damaged or unnecessary mitochondria, which is crucial to sustaining mitochondrial quality control. In numerous human diseases, the accumulation of damaged mitochondria by impaired mitophagy has been observed. However, the therapeutic strategy targeting of mitoNEET as a mitophagy-enhancing mediator requires further research. Herein, we confirmed that mitophagy is indeed activated by mitoNEET inhibition. CCCP (carbonyl cyanide m-chlorophenyl hydrazone), which leads to mitochondrial depolarization, induces mitochondrial dysfunction and superoxide production. This, in turn, contributes to the induction of mitophagy; mitoNEET protein levels were initially increased before an increase in LC3-Ⅱ protein following CCCP treatment. Pharmacological inhibition of mitoNEET using mitoNEET Ligand-1 (NL-1) promoted accumulation of Pink1 and Parkin, which are mitophagy-associated proteins, and activation of mitochondria-lysosome crosstalk, in comparison to CCCP alone. Inhibition of mitoNEET using NL-1, or mitoNEET shRNA transfected into RAW264.7 cells, abrogated CCCP-induced ROS and mitochondrial cell death; additionally, it activated the expression of PGC-1α and SOD2, regulators of oxidative metabolism. In particular, the increase in PGC-1α, which is a major regulator of mitochondrial biogenesis, promotes mitochondrial quality control. These results indicated that mitoNEET is a potential therapeutic target in numerous human diseases to enhance mitophagy and protect cells by maintaining a network of healthy mitochondria.
  17. Nat Commun. 2022 Jun 23. 13(1): 3585
      Mitochondrial ADP/ATP carriers import ADP into the mitochondrial matrix and export ATP to the cytosol to fuel cellular processes. Structures of the inhibited cytoplasmic- and matrix-open states have confirmed an alternating access transport mechanism, but the molecular details of substrate binding remain unresolved. Here, we evaluate the role of the solvent-exposed residues of the translocation pathway in the process of substrate binding. We identify the main binding site, comprising three positively charged and a set of aliphatic and aromatic residues, which bind ADP and ATP in both states. Additionally, there are two pairs of asparagine/arginine residues on opposite sides of this site that are involved in substrate binding in a state-dependent manner. Thus, the substrates are directed through a series of binding poses, inducing the conformational changes of the carrier that lead to their translocation. The properties of this site explain the electrogenic and reversible nature of adenine nucleotide transport.
  18. Sci Adv. 2022 Jun 24. 8(25): eabn9699
      Hürthle cell carcinomas (HCCs) display two exceptional genotypes: near-homoplasmic mutation of mitochondrial DNA (mtDNA) and genome-wide loss of heterozygosity (gLOH). To understand the phenotypic consequences of these genetic alterations, we analyzed genomic, metabolomic, and immunophenotypic data of HCC and other thyroid cancers. Both mtDNA mutations and profound depletion of citrate pools are common in HCC and other thyroid malignancies, suggesting that thyroid cancers are broadly equipped to survive tricarboxylic acid cycle impairment, whereas metabolites in the reduced form of NADH-dependent lysine degradation pathway were elevated exclusively in HCC. The presence of gLOH was not associated with metabolic phenotypes but rather with reduced immune infiltration, indicating that gLOH confers a selective advantage partially through immunosuppression. Unsupervised multimodal clustering revealed four clusters of HCC with distinct clinical, metabolomic, and microenvironmental phenotypes but overlapping genotypes. These findings chart the metabolic and microenvironmental landscape of HCC and shed light on the interaction between genotype, metabolism, and the microenvironment in cancer.
  19. Chem Sci. 2022 Jun 01. 13(21): 6197-6204
      Mitochondria are essential intracellular organelles involved in many cellular processes, especially adenosine triphosphate (ATP) production. Since cancer cells require high ATP levels for proliferation, ATP elimination can be a unique target for cancer growth inhibition. We describe a newly developed mitochondria-targeting nucleopeptide (MNP) that sequesters ATP by self-assembling with ATP inside mitochondria. MNP interacts strongly with ATP through electrostatic and hydrogen bonding interactions. MNP exhibits higher binding affinity for ATP (-637.5 kJ mol-1) than for adenosine diphosphate (ADP) (-578.2 kJ mol-1). To improve anticancer efficacy, the small-sized MNP/ADP complex formed large assemblies with ATP inside cancer cell mitochondria. ATP sequestration and formation of large assemblies of the MNP/ADP-ATP complex inside mitochondria caused physical stress by large structures and metabolic disorders in cancer cells, leading to apoptosis. This work illustrates a facile approach to developing cancer therapeutics that relies on molecular assemblies.
  20. Biomolecules. 2022 Jun 04. pii: 786. [Epub ahead of print]12(6):
      Mitochondrial function is dependent on molecular chaperones, primarily due to their necessity in the formation of respiratory complexes and clearance of misfolded proteins. Heat shock proteins (Hsps) are a subset of molecular chaperones that function in all subcellular compartments, both constitutively and in response to stress. The Hsp90 chaperone TNF-receptor-associated protein-1 (TRAP1) is primarily localized to the mitochondria and controls both cellular metabolic reprogramming and mitochondrial apoptosis. TRAP1 upregulation facilitates the growth and progression of many cancers by promoting glycolytic metabolism and antagonizing the mitochondrial permeability transition that precedes multiple cell death pathways. TRAP1 attenuation induces apoptosis in cellular models of cancer, identifying TRAP1 as a potential therapeutic target in cancer. Similar to cytosolic Hsp90 proteins, TRAP1 is also subject to post-translational modifications (PTM) that regulate its function and mediate its impact on downstream effectors, or 'clients'. However, few effectors have been identified to date. Here, we will discuss the consequence of TRAP1 deregulation in cancer and the impact of post-translational modification on the known functions of TRAP1.
    Keywords:  Hsp90; TRAP1; Warburg effect; cancer; chaperone; metabolism; mitochondria; post-translational modification
  21. Int J Mol Sci. 2022 Jun 10. pii: 6510. [Epub ahead of print]23(12):
      Altered lipid metabolism is a potential target for therapeutic intervention in cancer. Overexpression of Fatty Acid Synthase (FASN) correlates with poor prognosis in colorectal cancer (CRC). While multiple studies show that upregulation of lipogenesis is critically important for CRC progression, the contribution of FASN to CRC initiation is poorly understood. We utilize a C57BL/6-Apc/Villin-Cre mouse model with knockout of FASN in intestinal epithelial cells to show that the heterozygous deletion of FASN increases mouse survival and decreases the number of intestinal adenomas. Using RNA-Seq and gene set enrichment analysis, we demonstrate that a decrease in FASN expression is associated with inhibition of pathways involved in cellular proliferation, energy production, and CRC progression. Metabolic and reverse phase protein array analyses demonstrate consistent changes in alteration of metabolic pathways involved in both anabolism and energy production. Downregulation of FASN expression reduces the levels of metabolites within glycolysis and tricarboxylic acid cycle with the most significant reduction in the level of citrate, a master metabolite, which enhances ATP production and fuels anabolic pathways. In summary, we demonstrate the critical importance of FASN during CRC initiation. These findings suggest that targeting FASN is a potential therapeutic approach for early stages of CRC or as a preventive strategy for this disease.
    Keywords:  Apc mutation; colorectal cancer; colorectal cancer initiation; fatty acid synthase; lipid metabolism
  22. Front Oncol. 2022 ;12 835549
      Next-generation sequencing and bioinformatics analyses have clearly revealed the roles of mitochondrial ribosomal genes in cancer development. Mitochondrial ribosomes are composed of three RNA components encoded by mitochondrial DNA and 82 specific protein components encoded by nuclear DNA. They synthesize mitochondrial inner membrane oxidative phosphorylation (OXPHOS)-related proteins and participate in various biological activities via the regulation of energy metabolism and apoptosis. Mitochondrial ribosomal genes are strongly associated with clinical features such as prognosis and foci metastasis in patients with cancer. Accordingly, mitochondrial ribosomes have become an important focus of cancer research. We review recent advances in bioinformatics research that have explored the link between mitochondrial ribosomes and cancer, with a focus on the potential of mitochondrial ribosomal genes as biomarkers in cancer.
    Keywords:  apoptosis; bioinformatics; biomarker; cancer; energy metabolism; mitochondrial ribosome
  23. IUBMB Life. 2022 Jun 22.
      S-adenosyl-L-methionine (SAM) is a coenzyme and the most commonly used methyl-group donor for the modification of metabolites, DNA, RNA and proteins. SAM biosynthesis and SAM regeneration from the methylation reaction product S-adenosyl-L-homocysteine (SAH) take place in the cytoplasm. Therefore, the intramitochondrial SAM-dependent methyltransferases require the import of SAM and export of SAH for recycling. Orthologous mitochondrial transporters belonging to the mitochondrial carrier family have been identified to catalyze this antiport transport step: Sam5p in yeast, SLC25A26 (SAMC) in humans, and SAMC1-2 in plants. In mitochondria SAM is used by a vast number of enzymes implicated in the following processes: the regulation of replication, transcription, translation, and enzymatic activities; the maturation and assembly of mitochondrial tRNAs, ribosomes and protein complexes; and the biosynthesis of cofactors, such as ubiquinone, lipoate, and molybdopterin. Mutations in SLC25A26 and mitochondrial SAM-dependent enzymes have been found to cause human diseases, which emphasizes the physiological importance of these proteins.
    Keywords:  S-adenosyl-L-methionine; diseases; metabolism; methyltransferase; mitochondria; mitochondrial carrier; mitochondrial transport
  24. Talanta. 2022 Jun 17. pii: S0039-9140(22)00495-7. [Epub ahead of print]249 123699
      Mitochondrial sulfur dioxide (SO2) correlates with various activities of the development and progression of cancer. However, the specific biological function of mitochondrial SO2 in cancerous cells remains amphibolous. Therefore, it is of great significance and urgency to develop a rapid and accurate method to monitor the dynamic fluctuations of mitochondrial SO2 in cancer cells and tumor tissue. Herein, in this work, we introduce a "dual-positive charges" strategy for simultaneously enhancing the sensitivity and mitochondrial targeting ability of SO2 detection in cancer cells for the first time. For proof of concept, the dual positive charged probe DCP was rationally designed and synthesized based on chromenoquinoline fluorophore. Correspondingly, we also synthesized single positive charged SO2 probe MCP as controls. As expected, the detection limit of dual positive charged DCP for SO2 detection was 0.06 μM, which was 7-fold lower than that of the single positive charged probe MCP. Besides, DCP showed a higher mitochondrial co-localization coefficient in cancer cells and it could distinguish cancer cells (HeLa) and normal cells (L929) in co-incubated system. In a word, the evidence suggested that the implementation of dual-positive charges strategy greatly improved the sensitivity to SO2 response and the specificity of mitochondrial targeting in cancer cells. Finally, DCP was successfully applied to monitor SO2 fluctuation in cancer cells, tumor tissue and living zebrafish. Thus, this work provides a powerful tool to investigate the role of mitochondrial SO2 in cancer and other related diseases.
    Keywords:  Cancer discriminating; Dual-positive charges strategy; Mitochondrial targeting; Quantitative detection; SO(2) probe
  25. Nat Commun. 2022 Jun 24. 13(1): 3615
      Mitochondrial cytochrome c oxidase (CcO) or respiratory chain complex IV is a heme aa3-copper oxygen reductase containing metal centers essential for holo-complex biogenesis and enzymatic function that are assembled by subunit-specific metallochaperones. The enzyme has two copper sites located in the catalytic core subunits. The COX1 subunit harbors the CuB site that tightly associates with heme a3 while the COX2 subunit contains the binuclear CuA site. Here, we report that in human cells the CcO copper chaperones form macromolecular assemblies and cooperate with several twin CX9C proteins to control heme a biosynthesis and coordinate copper transfer sequentially to the CuA and CuB sites. These data on CcO illustrate a mechanism that regulates the biogenesis of macromolecular enzymatic assemblies with several catalytic metal redox centers and prevents the accumulation of cytotoxic reactive assembly intermediates.
  26. Oncogene. 2022 Jun 24.
      The dynamics of mitochondrial biogenesis regulation is critical in maintaining cellular homeostasis for immune regulation and tumor prevention. Here, we report that mitochondrial biogenesis disruption through TFAM reduction significantly impairs mitochondrial function, induces autophagy, and promotes esophageal squamous cell carcinoma (ESCC) growth. We found that TFAM protein reduction promotes mitochondrial DNA (mtDNA) release into the cytosol, induces cytosolic mtDNA stress, subsequently activates the cGAS-STING signaling pathway, thereby stimulating autophagy and ESCC growth. STING depletion or mtDNA degradation by DNase I abrogates mtDNA stress response, attenuates autophagy, and decreases the growth of TFAM depleted cells. In addition, autophagy inhibitor also ameliorates mitochondrial dysfunction-induced activation of the cGAS-STING signaling pathway and ESCC growth. In conclusion, our results indicate that mtDNA stress induced by mitochondria biogenesis perturbation activates the cGAS-STING pathway and autophagy to promote ESCC growth, revealing an underappreciated therapeutic strategy for ESCC.
  27. Cell Death Differ. 2022 Jun 20.
      The ability of mitochondria to buffer a rapid rise in cytosolic Ca2+ is a hallmark of proper cell homeostasis. Here, we employed m-3M3FBS, a putative phospholipase C (PLC) agonist, to explore the relationships between intracellular Ca2+ imbalance, mitochondrial physiology, and cell death. m-3M3FBS induced a potent dose-dependent Ca2+ release from the endoplasmic reticulum (ER), followed by a rise in intra-mitochondrial Ca2+. When the latter exceeded the organelle buffering capacity, an abrupt mitochondrial inner membrane permeabilization (MIMP) occurred, releasing matrix contents into the cytosol. MIMP was followed by cell death that was independent of Bcl-2 family members and inhibitable by the intracellular Ca2+ chelator BAPTA-AM. Cyclosporin A (CsA), capable of blocking the mitochondrial permeability transition (MPT), completely prevented cell death induced by m-3M3FBS. However, CsA acted upstream of mitochondria by preventing Ca2+ release from ER stores. Therefore, loss of Ca2+ intracellular balance and mitochondrial Ca2+ overload followed by MIMP induced a cell death process that is distinct from Bcl-2 family-regulated mitochondrial outer membrane permeabilization (MOMP). Further, the inhibition of cell death by CsA or its analogues can be independent of effects on the MPT.
  28. Biomolecules. 2022 May 28. pii: 756. [Epub ahead of print]12(6):
      The anti-diabetic drug metformin is currently tested for the treatment of hematological and solid cancers. Proteasome inhibitors, e.g., Bortezomib, are approved for the treatment of multiple myeloma and mantle cell lymphoma but are also studied for lung cancer therapy. We here analyzed the interaction of the two drugs in two cell lines, namely the mantle cell lymphoma Jeko-1 and the non-small-cell lung cancer (NSCLC) H1299 cells, using proliferation and survival assays, native-gel analysis for proteasome activity and assembly, and expression analysis of proteasome assembly factors. Our results demonstrate that metformin treatment induces resistance of cancer cells to the proteasome inhibitor Bortezomib by impairing the activity and assembly of the 26S proteasome complexes. These effects of metformin on proteasome inhibitor sensitivity in cancer cells are of potential relevance for patients that receive proteasome inhibitor therapy.
    Keywords:  26S proteasome; metformin; proteasome activity; proteasome inhibitor; resistance
  29. BMC Genom Data. 2022 Jun 21. 23(1): 47
      OBJECTIVES: Functional genetic variation plays an important role in predicting patients' response to chemotherapeutic agents. A growing catalogue of mitochondrial DNA (mtDNA) alterations in various cancers point to their important roles in altering the drug responsiveness and survival of cancer cells. In this work, we report the mtDNA sequences, obtained using a nanopore sequencer that can directly sequence unamplified DNA, and the transcriptomes of oral squamous cell carcinoma (OSCC) cell lines with differing responses to cisplatin, to explore the interplay between mtDNA alterations, epigenetic regulation of gene expression, and cisplatin response in OSCC.DATA DESCRIPTION: Two human OSCC cell lines, namely H103 and SAS, and drug-resistant stem-like cells derived from SAS were used in this work. To validate our hypothesis that cisplatin sensitivity is linked to mtDNA changes, we sequenced their mtDNA using a nanopore sequencer, MinION. We also obtained the whole transcriptomic profiles of the cells from a microarray analysis. The mtDNA mutational and whole transcriptomic profiles that we provide can be used alongside other similar datasets to facilitate the identification of new markers of cisplatin sensitivity, and therefore the development of effective therapies for OSCC.
    Keywords:  Cisplatin response; Gene expression; Human Clariom S array; Mitochondrial DNA; Oral squamous cell carcinoma; Oxford Nanopore Technologies
  30. Genes (Basel). 2022 Jun 07. pii: 1025. [Epub ahead of print]13(6):
      Despite two decades of paraganglioma-pheochromocytoma research, the fundamental question of how the different succinate dehydrogenase (SDH)-related tumor phenotypes are initiated has remained unanswered. Here, we discuss two possible scenarios by which missense (hypomorphic alleles) or truncating (null alleles) SDH gene variants determine clinical phenotype. Dysfunctional SDH is a major source of reactive oxygen species (ROS) but ROS are inhibited by rising succinate levels. In scenario 1, we propose that SDH missense variants disrupt electron flow, causing elevated ROS levels that are toxic in sympathetic PPGL precursor cells but well controlled in oxygen-sensing parasympathetic paraganglion cells. We also suggest that SDHAF2 variants, solely associated with HNPGL, may cause the reversal of succinate dehydrogenase to fumarate reductase, producing very high ROS levels. In scenario 2, we propose a modified succinate threshold model of tumor initiation. Truncating SDH variants cause high succinate accumulation and likely initiate tumorigenesis via disruption of 2-oxoglutarate-dependent enzymes in both PPGL and HNPGL precursor tissues. We propose that missense variants (including SDHAF2) cause lower succinate accumulation and thus initiate tumorigenesis only in very metabolically active tissues such as parasympathetic paraganglia, which naturally show very high levels of succinate.
    Keywords:  head and neck paraganglioma; neuroendocrine tumor; pheochromocytoma; reactive oxygen species; succinate dehydrogenase
  31. Cell Rep. 2022 Jun 21. pii: S2211-1247(22)00781-1. [Epub ahead of print]39(12): 110995
      Dysregulated cellular metabolism is a cancer hallmark for which few druggable oncoprotein targets have been identified. Increased fatty acid (FA) acquisition allows cancer cells to meet their heightened membrane biogenesis, bioenergy, and signaling needs. Excess FAs are toxic to non-transformed cells but surprisingly not to cancer cells. Molecules underlying this cancer adaptation may provide alternative drug targets. Here, we demonstrate that diacylglycerol O-acyltransferase 1 (DGAT1), an enzyme integral to triacylglyceride synthesis and lipid droplet formation, is frequently up-regulated in melanoma, allowing melanoma cells to tolerate excess FA. DGAT1 over-expression alone transforms p53-mutant zebrafish melanocytes and co-operates with oncogenic BRAF or NRAS for more rapid melanoma formation. Antagonism of DGAT1 induces oxidative stress in melanoma cells, which adapt by up-regulating cellular reactive oxygen species defenses. We show that inhibiting both DGAT1 and superoxide dismutase 1 profoundly suppress tumor growth through eliciting intolerable oxidative stress.
    Keywords:  CP: Cancer; DGAT1; SOD1; fatty acids; lipid droplets; melanoma; oxidative stress; reactive oxygen species
  32. Signal Transduct Target Ther. 2022 Jun 22. 7(1): 192
      Folic acid, served as dietary supplement, is closely linked to one-carbon metabolism and methionine metabolism. Previous clinical evidence indicated that folic acid supplementation displays dual effect on cancer development, promoting or suppressing tumor formation and progression. However, the underlying mechanism remains to be uncovered. Here, we report that high-folate diet significantly promotes cancer development in mice with hepatocellular carcinoma (HCC) induced by DEN/high-fat diet (HFD), simultaneously with increased expression of methionine adenosyltransferase 2A (gene name, MAT2A; protein name, MATIIα), the key enzyme in methionine metabolism, and acceleration of methionine cycle in cancer tissues. In contrast, folate-free diet reduces MATIIα expression and impedes HFD-induced HCC development. Notably, methionine metabolism is dynamically reprogrammed with valosin-containing protein p97/p47 complex-interacting protein (VCIP135) which functions as a deubiquitylating enzyme to bind and stabilize MATIIα in response to folic acid signal. Consistently, upregulation of MATIIα expression is positively correlated with increased VCIP135 protein level in human HCC tissues compared to adjacent tissues. Furthermore, liver-specific knockout of Mat2a remarkably abolishes the advocating effect of folic acid on HFD-induced HCC, demonstrating that the effect of high or free folate-diet on HFD-induced HCC relies on Mat2a. Moreover, folate and multiple intermediate metabolites in one-carbon metabolism are significantly decreased in vivo and in vitro upon Mat2a deletion. Together, folate promotes the integration of methionine and one-carbon metabolism, contributing to HCC development via hijacking MATIIα metabolic pathway. This study provides insight into folate-promoted cancer development, strongly recommending the tailor-made folate supplement guideline for both sub-healthy populations and patients with cancer expressing high level of MATIIα expression.
  33. Biochim Biophys Acta Mol Basis Dis. 2022 Jun 15. pii: S0925-4439(22)00138-7. [Epub ahead of print] 166467
      Mitochondrial transcription factor A (TFAM) is essential for the maintenance, expression, and packaging of mitochondrial DNA (mtDNA). Recently, a pathogenic homozygous variant in TFAM (P178L) has been associated with a severe mtDNA depletion syndrome leading to neonatal liver failure and early death. We have performed a biochemical characterization of the TFAM variant P178L in order to understand the molecular basis for the pathogenicity of this mutation. We observe no effects on DNA binding, and compaction of DNA is only mildly affected by the P178L amino acid change. Instead, the mutation severely impairs mtDNA transcription initiation at the mitochondrial heavy and light strand promoters. Molecular modeling suggests that the P178L mutation affects promoter sequence recognition and the interaction between TFAM and the tether helix of POLRMT, thus explaining transcription initiation deficiency.
    Keywords:  Disease causing mutation; Mitochondria; TFAM; Transcription initiation; mtDNA depletion
  34. Ecotoxicol Environ Saf. 2022 Jun 20. pii: S0147-6513(22)00628-5. [Epub ahead of print]241 113788
      The beneficial roles of resveratrol (RES) in affecting proliferation of multiple cancer cells have attracted intensive attention. However, the underlying mechanism remains unclear. This study aims to bridge the knowledge gap by investigating RES-induced growth inhibition of HeLa cells. Our work focuses on the metergasis of mitochondria in the RES-exposed cells. Therefore, HeLa cells were treated with different concentrations of RES for 30 min and 24 h, respectively. As a result, concentration-dependent increases in cell growth inhibition, ROS (reactive oxygen species) triggering, and LC3-II (light chain 3-II) expression were detected in the HeLa cells exposed to RES for 24 h. Interestingly, a specific concentration-dependent effect was observed in the HeLa cells exposed to RES for 30 min, that is, low concentration RES (≤ 25 μmol/L) reduced ROS levels, inhibited transcription and expression levels of LC3-II, and stimulated mitochondrial respiratory capacities. In contrast, high concentration RES (50 and 100 μmol/L) induced ROS over-production and autophagy in the cells, resulting in decreased levels of mitochondrial membrane potential, mitochondrial DNA copy numbers, and mitochondrial respiratory capacities. Together, our data concluded that RES inhibited HeLa cell proliferation through perturbation of mitochondrial structure and function, and ROS-induced autophagy also played a critical role in the process.
    Keywords:  Autophagy; Cell homeostasis; HeLa cells; Mitochondrial function; Resveratrol
  35. Front Oncol. 2022 ;12 903157
      Cachexia is a debilitating comorbidity affecting many lung cancer patients. We have previously found that cachectic mice with lung cancer have reduced serum ketone body levels due to low PPARα activity in the liver. Restoring hepatic PPARα activity with fenofibrate increased circulating ketones and delayed muscle and white adipose tissue wasting. We hypothesized that the loss of circulating ketones plays a pathophysiologic role in cachexia and performed two dietary intervention studies to test this hypothesis. In the first study, male and female mice were randomized to consume either a very low carbohydrate, ketogenic diet (KD) or normal chow (NC) after undergoing tumor induction. The KD successfully restored serum ketone levels and decreased blood glucose in cachectic mice but did not improve body weight maintenance or survival. In fact, there was a trend for the KD to worsen survival in male but not in female mice. In the second study, we compounded a ketone ester supplement into the NC diet (KE) and randomized tumor-bearing mice to KE or NC after tumor induction. We confirmed that KE was able to acutely and chronically increase ketone body abundance in the serum compared to NC. However, the restoration of ketones in the circulation was not able to improve body weight maintenance or survival in male or female mice with lung cancer. Finally, we investigated PPARα activity in the liver of mice fed KE and NC and found that animals fed a ketone ester supplement showed a significant increase in mRNA expression of several PPARα targets. These data negate our initial hypothesis and suggest that restoring ketone body availability in the circulation of mice with lung cancer does not alter cachexia development or improve survival, despite increasing hepatic PPARα activity.
    Keywords:  PPAR alpha; beta hydroxybutyrate; cachexia; ketogenic diet (KD); ketone ester supplementation; lung cancer
  36. Front Oncol. 2022 ;12 852985
      Chronic Myeloid Leukemia is a neoplastic disease characterized by the abnormal expansion of hematopoietic cells with compromised functions. Leukemic cells often display a multidrug resistance phenotype, enabling them to evade a number of structurally unrelated cytotoxic compounds. One of those mechanisms relies on the high expression of efflux transporters, such as the ABC proteins, whose activity depends on the hydrolysis of ATP to reduce intracellular drug accumulation. In the present work, we employed a well-known erythroleukemia cell line, K562, and a multidrug resistant derivative cell, FEPS, to evaluate how hexokinase II, a key regulator for the rate-limiting step glycolysis, contributes to the establishment of the multidrug resistance phenotype. We found that multidrug resistant cells primarily resort to glycolysis to generate ATP. Clotrimazole reduced the expression of mitochondrial hexokinase II, which destabilized bioenergetic parameters such as reactive oxygen species production, ATP, and glutathione levels on multidrug resistant cells. This impaired the activity of ABCC1, leading to increased drug accumulation and cell death. In summary, we propose that decoupling of hexokinase II from the mitochondria emerges as a promising strategy to generate collateral sensitivity and aid in the management of chronic myeloid leukemia in chemotherapy-refractory patients.
    Keywords:  chemoresistance; chronic myelogenous leukemia; glutathione; hexokinase II; metabolism
  37. Proc Natl Acad Sci U S A. 2022 Jun 28. 119(26): e2200923119
      All kingdoms of life produce essential nicotinamide dinucleotide NADP(H) using NAD kinases (NADKs). A panel of published NADK structures from bacteria, eukaryotic cytosol, and yeast mitochondria revealed similar tetrameric enzymes. Here, we present the 2.8-Å structure of the human mitochondrial kinase NADK2 with a bound substrate, which is an exception to this uniformity, diverging both structurally and biochemically from NADKs. We show that NADK2 harbors a unique tetramer disruptor/dimerization element, which is conserved in mitochondrial kinases of animals (EMKA) and absent from other NADKs. EMKA stabilizes the NADK2 dimer but prevents further NADK2 oligomerization by blocking the tetramerization interface. This structural change bears functional consequences and alters the activation mechanism of the enzyme. Whereas tetrameric NADKs undergo cooperative activation via oligomerization, NADK2 is a constitutively active noncooperative dimer. Thus, our data point to a unique regulation of NADP(H) synthesis in animal mitochondria achieved via structural adaptation of the NADK2 kinase.
    Keywords:  NADK; NADK2; cooperative; dimer; structure
  38. Cell Death Dis. 2022 Jun 18. 13(6): 556
      High-grade serous ovarian cancer (HGSOC) is the most lethal gynecologic malignancy mainly due to its extensive metastasis. Cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3), a newly discovered splice variant of solute carrier organic anion transporter family member 1B3 (SLCO1B3), has been reported to be overexpressed in several types of cancer. However, the biological function of Ct-OATP1B3 remains largely unknown. Here, we reveal that Ct-OATP1B3 is overexpressed in HGSOC and promotes the metastasis of HGSOC in vivo and in vitro. Mechanically, Ct-OATP1B3 directly interacts with insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), an RNA-binding protein, which results in enhancement of the mRNA stability and expression of carnitine palmitoyltransferase 1A (CPT1A) and NADH:Ubiquinone Oxidoreductase Subunit A2 (NDUFA2), leading to increased mitochondrial fatty acid beta-oxidation (FAO) and oxidative phosphorylation (OXPHOS) activities. The increased FAO and OXPHOS activities further facilitate adenosine triphosphate (ATP) production and cellular lamellipodia formation, which is the initial step in the processes of tumor cell migration and invasion. Taken together, our study provides an insight into the function and underlying mechanism of Ct-OATP1B3 in HGSOC metastasis, and highlights Ct-OATP1B3 as a novel prognostic marker as well as therapeutic target in HGSOC.
  39. Sci Transl Med. 2022 Jun 22. 14(650): eabn3248
      Acute myeloid leukemia (AML) is an aggressive hematological disorder comprising a hierarchy of quiescent leukemic stem cells (LSCs) and proliferating blasts with limited self-renewal ability. AML has a dismal prognosis, with extremely low 2-year survival rates in the poorest cytogenetic risk patients, primarily due to the failure of intensive chemotherapy protocols to deplete LSCs and toxicity of therapy toward healthy hematopoietic cells. We studied the role of cyclin-dependent kinase regulatory subunit 1 (CKS1)-dependent protein degradation in primary human AML and healthy hematopoiesis xenograft models in vivo. Using a small-molecule inhibitor (CKS1i), we demonstrate a dual role for CKS1-dependent protein degradation in reducing patient-derived AML blasts in vivo and, importantly, depleting LSCs, whereas inhibition of CKS1 has the opposite effect on normal hematopoiesis, protecting normal hematopoietic stem cells from chemotherapeutic toxicity. Proteomic analysis of responses to CKS1i in our patient-derived xenograft mouse model demonstrate that inhibition of CKS1 in AML leads to hyperactivation of RAC1 and accumulation of lethal reactive oxygen species, whereas healthy hematopoietic cells enter quiescence in response to CKS1i, protecting hematopoietic stem cells. Together, these findings demonstrate that CKS1-dependent proteostasis is a key vulnerability in malignant stem cell biology.
  40. World J Stem Cells. 2022 May 26. 14(5): 362-364
      Pharmacological inhibitors of glutathione synthesis and circulation, such as buthionine-sulfoximine, inhibit glutathione metabolism. These drugs decrease the aggressiveness of pancreatic cancer, inhibit tumor stem cell survival, and reduce chemotherapy resistance. Nevertheless, buthionine-sulfoximine also decreases the content of glutathione in normal cells, disrupts the balance between reactive oxygen species and glutathione, and eventually induces cell apoptosis. Pancreatic cancer is usually diagnosed at an advanced stage and has a poor prognosis. Consequently, the use of biomarkers to screen high-risk patients can be an effective method.
    Keywords:  Cancer stem cells; Chemoresistance; Pancreatic cancer; Pancreatic ductal adenocarcinoma; Redox
  41. Cells. 2022 Jun 14. pii: 1920. [Epub ahead of print]11(12):
      Adenosine 5'-triphosphate, or ATP, is the primary molecule for storing and transferring energy in cells. ATP is mainly produced via oxidative phosphorylation in mitochondria, and to a lesser extent, via glycolysis in the cytosol. In general, cytosolic glycolysis is the primary ATP producer in proliferative cells or cells subjected to hypoxia. On the other hand, mitochondria produce over 90% of cellular ATP in differentiated cells under normoxic conditions. Under pathological conditions, ATP demand rises to meet the needs of biosynthesis for cellular repair, signaling transduction for stress responses, and biochemical processes. These changes affect how mitochondria and cytosolic glycolysis function and communicate. Mitochondria undergo remodeling to adapt to the imbalanced demand and supply of ATP. Otherwise, a severe ATP deficit will impair cellular function and eventually cause cell death. It is suggested that ATP from different cellular compartments can dynamically communicate and coordinate to adapt to the needs in each cellular compartment. Thus, a better understanding of ATP dynamics is crucial to revealing the differences in cellular metabolic processes across various cell types and conditions. This requires innovative methodologies to record real-time spatiotemporal ATP changes in subcellular regions of living cells. Over the recent decades, numerous methods have been developed and utilized to accomplish this task. However, this is not an easy feat. This review evaluates innovative genetically encoded biosensors available for visualizing ATP in living cells, their potential use in the setting of human disease, and identifies where we could improve and expand our abilities.
    Keywords:  ATP; ATP dynamics; cellular bioenergetics; energy metabolism; genetically encoded fluorescent biosensors; glycolysis; mitochondria; real-time ATP monitor; spatiotemporal
  42. J Vis Exp. 2022 Jun 01.
      The mitochondrial permeability transition pore (mPTP) is a voltage-gated, nonselective, inner mitochondrial membrane (IMM) mega-channel important in health and disease. The mPTP mediates leakage of protons across the IMM during low-conductance opening and is specifically inhibited by cyclosporine A (CsA). Coenzyme Q (CoQ) is a regulator of the mPTP, and tissue-specific differences have been found in CoQ content and open probability of the mPTP in forebrain and heart mitochondria in a newborn mouse model of fragile X syndrome (FXS, Fmr1 knockout). We developed a technique to determine the voltage threshold for mPTP opening in this mutant strain, exploiting the role of the mPTP as a proton leak channel. To do so, oxygen consumption and membrane potential (ΔΨ) were simultaneously measured in isolated mitochondria using polarography and a tetraphenylphosphonium (TPP+) ion-selective electrode during leak respiration. The threshold for mPTP opening was determined by the onset of CsA-mediated inhibition of proton leak at specific membrane potentials. Using this approach, differences in voltage gating of the mPTP were precisely defined in the context of CoQ excess. This novel technique will permit future investigation for enhancing the understanding of physiological and pathological regulation of low-conductance opening of the mPTP.
  43. Nat Metab. 2022 Jun 20.
      Stress-adaptive mechanisms enable tumour cells to overcome metabolic constraints under nutrient and oxygen shortage. Aspartate is an endogenous metabolic limitation under hypoxic conditions, but the nature of the adaptive mechanisms that contribute to aspartate availability and hypoxic tumour growth are poorly understood. Here we identify GOT2-catalysed mitochondrial aspartate synthesis as an essential metabolic dependency for the proliferation of pancreatic tumour cells under hypoxic culture conditions. In contrast, GOT2-catalysed aspartate synthesis is dispensable for pancreatic tumour formation in vivo. The dependence of pancreatic tumour cells on aspartate synthesis is bypassed in part by a hypoxia-induced potentiation of extracellular protein scavenging via macropinocytosis. This effect is mutant KRAS dependent, and is mediated by hypoxia-inducible factor 1 (HIF1A) and its canonical target carbonic anhydrase-9 (CA9). Our findings reveal high plasticity of aspartate metabolism and define an adaptive regulatory role for macropinocytosis by which mutant KRAS tumours can overcome nutrient deprivation under hypoxic conditions.
  44. Cell Death Dis. 2022 Jun 23. 13(6): 566
      The availability of asparagine is the limitation of cell growth and metastasis. Asparagine synthetase (ASNS) was an essential enzyme for endogenous asparagine products. In our study, ASNS-induced asparagine products were essential to maintain tumor growth and colony formations in vitro. But mutated ASNS which defected endogenous asparagine products still upregulated cell invasiveness, which indicated that ASNS promoted invasiveness by alternative pathways. Mechanically, ASNS modulated Wnt signal transduction by promoting GSK3β phosphorylation on ser9 and stabilizing the β-catenin complex, as result, ASNS could promote more β-catenin translocation into nucleus independent of endogenous asparagine. At the same time, ASNS modulated mitochondrial response to Wnt stimuli with increased mitochondrial potential and membrane fusion. In summary, ASNS promoted metastasis depending on Wnt pathway and mitochondrial functions even without endogenous asparagine products.
  45. Front Mol Biosci. 2022 ;9 869413
      Although the antineoplastic activity of metformin (MET) is well established, the underlying mechanism of the activity is not understood. Since MET activates AMP kinase (AMPK) and proline dehydrogenase/proline oxidase (PRODH/POX) is stimulated by AMPK ligands (implicated in the regulation of cancer cell survival/apoptosis), the effect of MET on PRODH/POX-dependent apoptosis in wild-type MCF-7 cells (MCF-7WT) and POX knockdown MCF-7 cells (MCF-7crPOX cells) was studied. PRODH/POX catalyzes proline degradation generating ROS-induced apoptosis or autophagy. Availability of proline for PRODH/POX functions is regulated by the activity of prolidase (enzyme releasing proline from imidodipeptides), collagen biosynthesis (process consuming proline), and metabolism of proline, ornithine, and glutamic acid. We have found that MET is cytotoxic for MCF-7 cells (IC50∼17 mM), and to the lower extent for MCF-7crPOX cells (IC50∼28 mM). In MCF-7WT cells, the effect was accompanied by the inhibition of DNA biosynthesis, collagen biosynthesis, stimulation of ROS formation, AMPKα phosphorylation, and expression of prolidase, p53, caspase 8, caspase 9, and cleaved PARP. In MET-treated MCF-7crPOX cells, the processes were less affected than in MCF-7WT cells and the expression of caspase 9 was decreased, while cleaved caspase 8 and cleaved PARP were not detected. The effects were accompanied by an increase in the prolidase activity and proline concentration. The mechanism for MET-induced apoptosis involves the up-regulation of prolidase activity and a decrease in collagen biosynthesis contributing to an increase in the concentration of substrate (proline) for PRODH/POX-dependent ROS formation and activation of caspases -9 and -8. The data suggest that PRODH/POX participates in the MET-induced intrinsic and extrinsic apoptosis in MCF-7 cells.
    Keywords:  PRODH/POX; apoptosis; breast cancer cells; metformin; proline dehydrogenase; proline oxidase
  46. World J Surg Oncol. 2022 Jun 22. 20(1): 211
      BACKGROUND: More and more evidence suggests that cancer is a mitochondrial metabolic disease recently and mitochondria dysfunction is critical to tumorigenesis. As a gatekeeper of mitochondria, the voltage-dependent anion channel 1 (VDAC1) is associated with the development of breast cancer (BC). However, its potential mechanism and clinical significance remain unclear; thus, in this research, we aimed to explore it.METHODS: VDAC1 expression in BC tissues and normal tissues was obtained from The Cancer Genome Atlas (TCGA) and validated by datasets from the gene expression omnibus (GEO) database. Then, the relationships between VDAC1 expression and clinicopathological features were analyzed. Receiver operating characteristics (ROC) curves were used to identify the diagnostic value of VDAC1. The prognostic value was evaluated by Kaplan-Meier survival curves and Cox regression analysis. VDAC1 with its co-expression genes were subjected to enrichment analysis to explore potential mechanisms in BC and the protein-protein interaction (PPI) network was constructed. At last, the association between VDAC1 expression and infiltration levels of immune cell infiltration by various methods, as well as their corresponding markers, was analyzed. We also analyzed the correction between VDAC1 expression and eight immune checkpoint genes and the tumor immune dysfunction and exclusion (TIDE) scores of each BC sample in TCGA were calculated and the differences between high and low VDAC1 expression groups were analyzed.
    RESULTS: VDAC1 expression was remarkably elevated in BC (p < 0.001), and high expression of VDAC1 was associated with the positive expression of ER (p = 0.004), PR (p = 0.033), and HER2 (p = 0.001). ROC analysis suggested that VDAC1 had diagnosed value in BC. The Kaplan-Meier analysis suggested that higher expression of VDAC1 was associated with shorter overall survival (OS), and further Cox regression analysis revealed that VDAC1 was an independent factor of unfavorable prognosis in BC patients. Enrichment analysis of VDAC1 and its co-expression suggested that VDAC1 was related to the regulation of mitochondrial energy metabolism and protein modification, and the HIF-1 singing pathway might be the potential mechanism in BC. Notably, we found that VDAC1 expression was infiltration levels of most types of immune cells, as well as the expression of marker genes of immune cells. The ICGs PDCD1, CTLA4, LAG3, SIGLEC15, and TIGIT were negatively corrected with VDAC1 expression in BC. TIDE scores between the low and high expression groups showed no difference.
    CONCLUSION: Overexpressed VDAC1 in BC could be severed as a novel biomarker for diagnosis and VDAC1 was an independent factor for adverse prognosis prediction. Our study revealed that VDAC1 might inhibit tumor immunity and might be a novel therapeutic target in BC.
    Keywords:  Bioinformatics; Breast cancer; Diagnosis; Immune cells; Prognosis; VDAC1