bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2022‒03‒20
thirty papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. FEBS Open Bio. 2022 Mar 18.
      Mutations in genes encoding cytochrome c oxidase (COX; mitochondrial complex IV) subunits and assembly factors (e.g., SCO1, SCO2, COA6) are linked to severe metabolic syndromes. Notwithstanding that SCO2 is under transcriptional control of tumour suppressor p53, the role of mitochondrial complex IV dysfunction in cancer metabolism remains obscure. Herein, we demonstrate that the loss of SCO2 in HCT116 colorectal cancer cells leads to significant metabolic and signaling perturbations. Specifically, abrogation of SCO2 increased NAD+ regenerating reactions and decreased glucose oxidation through citric acid cycle while enhancing pyruvate carboxylation. This was accompanied by a reduction in amino acid levels and the accumulation of lipid droplets. In addition, SCO2 loss resulted in hyperactivation of the IGF1R/AKT axis with paradoxical downregulation of mTOR signaling which was accompanied by increased AMPK activity. Accordingly, abrogation of SCO2 expression appears to increase the sensitivity of cells to IGF1R and AKT, but not mTOR inhibitors. Finally, the loss of SCO2 was associated with reduced proliferation and enhanced migration of HCT116 cells. Collectively, herein we describe potential adaptive signaling and metabolic perturbations triggered by mitochondrial complex IV dysfunction.
    Keywords:  AKT; AMPK; SCO2; cytochrome C oxidase; mTOR; metabolism; mitochondrial dysfunction
  2. ACS Med Chem Lett. 2022 Mar 10. 13(3): 348-357
      Mitochondria are key regulators of energy supply and cell death. Generation of ATP within mitochondria occurs through oxidative phosphorylation (OXPHOS), a process which utilizes the four complexes (complex I-IV) of the electron transport chain and ATP synthase. Certain oncogenic mutations (e.g., LKB1 or mIDH) can further enhance the reliance of cancer cells on OXPHOS for their energetic requirements, rendering cells sensitive to complex I inhibition and highlighting the potential value of complex I as a therapeutic target. Herein, we describe the discovery of a potent, selective, and species cross-reactive complex I inhibitor. A high-throughput screen of the Bayer compound library followed by hit triaging and initial hit-to-lead activities led to a lead structure which was further optimized in a comprehensive lead optimization campaign. Focusing on balancing potency and metabolic stability, this program resulted in the identification of BAY-179, an excellent in vivo suitable tool with which to probe the biological relevance of complex I inhibition in cancer indications.
  3. Front Cell Dev Biol. 2022 ;10 786268
      Mitochondria are complex organelles containing 13 proteins encoded by mitochondrial DNA and over 1,000 proteins encoded on nuclear DNA. Many mitochondrial proteins are associated with the inner or outer mitochondrial membranes, either peripherally or as integral membrane proteins, while others reside in either of the two soluble mitochondrial compartments, the mitochondrial matrix and the intermembrane space. The biogenesis of the five complexes of the oxidative phosphorylation system are exemplars of this complexity. These large multi-subunit complexes are comprised of more than 80 proteins with both membrane integral and peripheral associations and require soluble, membrane integral and peripherally associated assembly factor proteins for their biogenesis. Mutations causing human mitochondrial disease can lead to defective complex assembly due to the loss or altered function of the affected protein and subsequent destabilization of its interactors. Here we couple sodium carbonate extraction with quantitative mass spectrometry (SCE-MS) to track changes in the membrane association of the mitochondrial proteome across multiple human knockout cell lines. In addition to identifying the membrane association status of over 840 human mitochondrial proteins, we show how SCE-MS can be used to understand the impacts of defective complex assembly on protein solubility, giving insights into how specific subunits and sub-complexes become destabilized.
    Keywords:  OXPHOS (oxidative phosphorylation); carbonate extraction; membrane protein; mitochondria; proteomic analyses; respiratory chain assembly
  4. EMBO Rep. 2022 Mar 17. e52606
      Mitochondrial dysfunction can either extend or decrease Caenorhabditis elegans lifespan, depending on whether transcriptionally regulated responses can elicit durable stress adaptation to otherwise detrimental lesions. Here, we test the hypothesis that enhanced metabolic flexibility is sufficient to circumvent bioenergetic abnormalities associated with the phenotypic threshold effect, thereby transforming short-lived mitochondrial mutants into long-lived ones. We find that CEST-2.2, a carboxylesterase mainly localizes in the intestine, may stimulate the survival of mitochondrial deficient animals. We report that genetic manipulation of cest-2.2 expression has a minor lifespan impact on wild-type nematodes, whereas its overexpression markedly extends the lifespan of complex I-deficient gas-1(fc21) mutants. We profile the transcriptome and lipidome of cest-2.2 overexpressing animals and show that CEST-2.2 stimulates lipid metabolism and fatty acid beta-oxidation, thereby enhancing mitochondrial respiratory capacity through complex II and LET-721/ETFDH, despite the inherited genetic lesion of complex I. Together, our findings unveil a metabolic pathway that, through the tissue-specific mobilization of lipid deposits, may influence the longevity of mitochondrial mutant C. elegans.
    Keywords:   Caenorhabditis elegans ; carboxylesterase CEST-2.2; epigenetics; lipid metabolism; mitochondria
  5. Cell Cycle. 2022 Mar 17. 1-16
      We showed previously that POLG mutations cause major changes in mitochondrial function, including loss of mitochondrial respiratory chain (MRC) complex I, mitochondrial DNA (mtDNA) depletion and an abnormal NAD+/NADH ratio in both neural stem cells (NSCs) and astrocytes differentiated from induced pluripotent stem cells (iPSCs). In the current study, we looked at mitochondrial remodeling as stem cells transit pluripotency and during differentiation from NSCs to both dopaminergic (DA) neurons and astrocytes comparing the process in POLG-mutated and control stem cells. We saw that mitochondrial membrane potential (MMP), mitochondrial volume, ATP production and reactive oxygen species (ROS) changed in similar ways in POLG and control NSCs, but mtDNA replication, MRC complex I and NAD+ metabolism failed to remodel normally. In DA neurons differentiated from NSCs, we saw that POLG mutations caused failure to increase MMP and ATP production and blunted the increase in mtDNA and complex I. Interestingly, mitochondrial remodeling during astrocyte differentiation from NSCs was similar in both POLG-mutated and control NSCs. Further, we showed downregulation of the SIRT3/AMPK pathways in POLG-mutated cells, suggesting that POLG mutations lead to abnormal mitochondrial remodeling in early neural development due to the downregulation of these pathways. [Figure: see text].
    Keywords:  DA neurons; Mitochondrial remodeling; NSCs; POLG; astrocytes; iPSCs
  6. Curr Biol. 2022 Mar 08. pii: S0960-9822(22)00328-1. [Epub ahead of print]
      Mitochondrial damage (MtD) represents a dramatic change in cellular homeostasis, necessitating metabolic changes and stimulating mitophagy. One rapid response to MtD is a rapid peri-mitochondrial actin polymerization termed ADA (acute damage-induced actin). The activation mechanism for ADA is unknown. Here, we use mitochondrial depolarization or the complex I inhibitor metformin to induce ADA. We show that two parallel signaling pathways are required for ADA. In one pathway, increased cytosolic calcium in turn activates PKC-β, Rac, WAVE regulatory complex, and Arp2/3 complex. In the other pathway, a drop in cellular ATP in turn activates AMPK (through LKB1), Cdc42, and FMNL formins. We also identify putative guanine nucleotide exchange factors for Rac and Cdc42, Trio and Fgd1, respectively, whose phosphorylation states increase upon mitochondrial depolarization and whose suppression inhibits ADA. The depolarization-induced calcium increase is dependent on the mitochondrial sodium-calcium exchanger NCLX, suggesting initial mitochondrial calcium efflux. We also show that ADA inhibition results in enhanced mitochondrial shape changes upon mitochondrial depolarization, suggesting that ADA inhibits these shape changes. These depolarization-induced shape changes are not fragmentation but a circularization of the inner mitochondrial membrane, which is dependent on the inner mitochondrial membrane protease Oma1. ADA inhibition increases the proteolytic processing of an Oma1 substrate, the dynamin GTPase Opa1. These results show that ADA requires the combined action of the Arp2/3 complex and formin proteins to polymerize a network of actin filaments around mitochondria and that the ADA network inhibits the rapid mitochondrial shape changes that occur upon mitochondrial depolarization.
    Keywords:  AMPK; Arp2/3 complex; CCCP; FMNL formins; OMA1; OPA1; PKCβ; actin; calcium; mitochondrial depolarization
  7. Cell Death Dis. 2022 Mar 16. 13(3): 241
      Mitochondria are the major organelles in sensing cellular stress and inducing the response for cell survival. Mitochondrial Lon has been identified as an important stress protein involved in regulating proliferation, metastasis, and apoptosis in cancer cells. However, the mechanism of retrograde signaling by Lon on mitochondrial DNA (mtDNA) damage remains to be elucidated. Here we report the role of Lon in the response to cisplatin-induced mtDNA damage and oxidative stress, which confers cancer cells on cisplatin resistance via modulating calcium levels in mitochondria and cytosol. First, we found that cisplatin treatment on oral cancer cells caused oxidative damage of mtDNA and induced Lon expression. Lon overexpression in cancer cells decreased while Lon knockdown sensitized the cytotoxicity towards cisplatin treatment. We further identified that cisplatin-induced Lon activates the PYK2-SRC-STAT3 pathway to stimulate Bcl-2 and IL-6 expression, leading to the cytotoxicity resistance to cisplatin. Intriguingly, we found that activation of this pathway is through an increase of intracellular calcium (Ca2+) via NCLX, a mitochondrial Na+/Ca2+ exchanger. We then verified that NCLX expression is dependent on Lon levels; Lon interacts with and activates NCLX activity. NCLX inhibition increased the level of mitochondrial calcium and sensitized the cytotoxicity to cisplatin in vitro and in vivo. In summary, mitochondrial Lon-induced cisplatin resistance is mediated by calcium release into cytosol through NCLX, which activates calcium-dependent PYK2-SRC-STAT3-IL-6 pathway. Thus, our work uncovers the novel retrograde signaling by mitochondrial Lon on resistance to cisplatin-induced mtDNA stress, indicating the potential use of Lon and NCLX inhibitors for better clinical outcomes in chemoresistant cancer patients.
  8. Mol Ther Oncolytics. 2022 Mar 17. 24 695-706
      Cancer cell energy metabolism plays an important role in dictating the efficacy of oncolysis by oncolytic viruses. To understand the role of multiple myeloma metabolism in reovirus oncolysis, we performed semi-targeted mass spectrometry-based metabolomics on 12 multiple myeloma cell lines and revealed a negative correlation between NAD+ levels and susceptibility to oncolysis. Likewise, a negative correlation was observed between the activity of the rate-limiting NAD+ synthesis enzyme NAMPT and oncolysis. Indeed, depletion of NAD+ levels by pharmacological inhibition of NAMPT using FK866 sensitized several myeloma cell lines to reovirus-induced killing. The myelomas that were most sensitive to this combination therapy expressed a functional p53 and had a metabolic and transcriptomic profile favoring mitochondrial metabolism over glycolysis, with the highest synergistic effect in KMS12 cells. Mechanistically, U-13C-labeled glucose flux, extracellular flux analysis, multiplex proteomics, and cell death assays revealed that the reovirus + FK866 combination caused mitochondrial dysfunction and energy depletion, leading to enhanced autophagic cell death in KMS12 cells. Finally, the combination of reovirus and NAD+ depletion achieved greater antitumor effects in KMS12 tumors in vivo and patient-derived CD138+ multiple myeloma cells. These findings identify NAD+ depletion as a potential combinatorial strategy to enhance the efficacy of oncolytic virus-based therapies in multiple myeloma.
    Keywords:  FK866; NAD+; NAMPT; aerobic glycolysis; autophagy; cancer metabolism; mitochondrial metabolism; oncolytic virus; p53; reovirus
  9. Redox Biol. 2022 Mar 02. pii: S2213-2317(22)00049-0. [Epub ahead of print]51 102277
      Glutaredoxin 2 (Grx2) is a glutathione-dependent oxidoreductase that facilitates glutathionylation/de-glutathionylation of target proteins. The main variants of Grx2 are the mitochondrial Grx2a and the cytosolic Grx2c. The aim of this study was to investigate the specific role of mitochondrial Grx2 in vivo using a mitochondrial Grx2 depleted (mGD) mouse model. mGD mice displayed an altered mitochondrial morphology and functioning. Furthermore, the lack of Grx2 in the mitochondrial compartment is responsible for increased blood lipid levels under a normal diet, a metabolic dysfunction-associated fatty liver disease (MAFLD) phenotype and a decreased glycogen storage capacity. In addition, depleting Grx2a leads to an alteration in abundance and in glutathionylation pattern of different mitochondrial enzymes, highlighting the selective role of Grx2 in the regulation of metabolic pathways. Overall, our findings identify the involvement of mitochondrial Grx2a in the regulation of cell metabolism and highlight a previously unknown association between Grx2 and MAFLD.
    Keywords:  Glutaredoxin 2; Lipid metabolism; MAFLD; Mitochondria; Mouse model; ROS production
  10. J Cell Sci. 2022 Mar 17. pii: jcs.258937. [Epub ahead of print]
      MicroRNAs play a significant role in nuclear and mitochondrial anterograde and retrograde signaling. Most of the miRNAs found inside mitochondria are nuclear genome encoded, with few mitochondrial genome encoded non-coding RNAs have been reported. In this study, we have identified 13 mitochondrial genome-encoded microRNAs (mitomiRs), which were differentially expressed in breast cancer cell lines (MCF-7, MDA-MB-468, and MDA-MB-231), non-malignant breast epithelial cell line (MCF-10A), and normal and breast cancer tissue specimens. We found that mitochondrial DNA depletion and inhibition of mitochondrial transcription leads to reduced expression of mitomiRs in breast cancer cells. MitomiRs physically interact with Ago2, an RNA-induced silencing complex (RISC) protein, in the cytoplasm and inside mitochondria. MitomiRs regulate the expression of both nuclear and mitochondrial transcripts in breast cancer cells. We showed that mitomiR-5 targets PPARGC1A and regulates mtDNA copy number in breast cancer cells. MitomiRs identified in the present study may be a promising tool for expression and functional analysis in patients with a defective mitochondrial phenotype, including cancer and metabolic syndromes.
    Keywords:   PPARGC1A ; MicroRNAs; Mitochondria; mitomiRs; mtDNA copy number
  11. Eur Urol Focus. 2022 Mar 11. pii: S2405-4569(21)00312-6. [Epub ahead of print]
      BACKGROUND: Succinate dehydrogenase-deficient and fumarate hydratase-deficient renal cell carcinomas (SDHRCC and FHRCC) are rare kidney cancers driven by loss of TCA cycle enzymes.OBJECTIVE: To define and compare the genomic and metabolomic hallmarks of SDHRCC and FHRCC.
    DESIGN, SETTING, AND PARTICIPANTS: We analyzed SDHRCC and FHRCC tumors with either immunohistochemical evidence of loss of protein expression or genomically confirmed biallelic inactivation of SDHA/B/C/D/AF2 or FH.
    OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Somatic alterations were identified using clinical pipelines, with allele-specific copy number alterations (CNAs) identified using FACETS. Mass spectrometry-based metabolomic profiling was performed on available SDHRCC and FHRCC tumors.
    RESULTS AND LIMITATIONS: Tumors were analyzed for 42 patients (25 FHRCC, 17 SDHRCC). In the germline analysis, 16/17 SDHRCCs harbored a germline alteration in SDHB, whereas only 17/22 FHRCCs had pathogenic germline FH variants. SDHRCCs had a lower mutation burden (p = 0.02) and CNA burden (p = 0.0002) than FHRCCs. All SDHRCCs presented with deletion of chromosome 1p (overlapping SDHB), whereas FHRCCs demonstrated high but not ubiquitous loss of 1q (FH locus). Both SDHRCCs and FHRCCs exhibited significant idiopathic accumulation of the metabolite guanine. FHRCC tumors had elevated levels of urea cycle metabolites (argininosuccinate, citrulline, and fumarate), whereas SDHRCC tumors had elevation of numerous acylcarnitines. These characteristic metabolic changes allowed identification of a previously unrecognized SDH-deficient RCC.
    CONCLUSIONS: Despite sharing similar genetic etiology, SDHRCC and FHRCC represent distinct molecular entities with unique genetic and metabolic abnormalities.
    PATIENT SUMMARY: Kidney cancers driven by loss of the gene encoding either the succinate dehydrogenase or fumarate hydratase enzyme are rare. We sought to define and compare the genetic and metabolic features of these cancer entities.
    Keywords:  Cancer genomics; FH; FHRCC; Metabolism; Renal cell carcinoma; SDH; SDHRCC
  12. Methods Mol Biol. 2022 ;2474 11-19
      Mitochondrial function, a key indicator of cell health, can be assessed through monitoring changes in mitochondrial membrane potential (MMP). Cationic fluorescent dyes are commonly used tools to assess MMP. We used a water-soluble mitochondrial membrane potential indicator (m-MPI) to detect changes in MMP in various types of cells, such as HepG2, HepaRG, and AC16 cells. A homogenous cell-based MMP assay has been optimized and performed in a 1536-well plate format, which can be used to screen several compound libraries for mitochondrial toxicity by evaluating the effects of chemical compounds on MMP.
    Keywords:  1536-well plate; Mesoxalonitrile 4-trifluoromethoxyphenylhydrazone (FCCP); Mitochondrial membrane potential (MMP); Mitochondrial membrane potential indicator (m-MPI); Mitochondrial toxicity
  13. J Biol Chem. 2022 Mar 09. pii: S0021-9258(22)00255-1. [Epub ahead of print] 101815
      Mitochondrial transcription factor A (TFAM) plays important roles in mitochondrial DNA (mtDNA) compaction, transcription initiation, and in the regulation of processes like transcription and replication processivity. It is possible that TFAM is locally regulated within the mitochondrial matrix via such mechanisms like phosphorylation by protein kinase A (PKA) and non-enzymatic acetylation by acetyl-CoA. Here we demonstrate that DNA-bound TFAM is less susceptible to these modifications. We confirmed using electrophoretic mobility shift assays that phosphorylated or acetylated TFAM compacted circular double-stranded DNA just as well as unmodified TFAM and provide an in-depth analysis of acetylated sites on TFAM. We show that both modifications of TFAM increase the processivity of mitochondrial RNA polymerase during transcription through TFAM-imposed barriers on DNA, but that TFAM bearing either modification retains its full activity in transcription initiation. We conclude that TFAM phosphorylation by PKA and non-enzymatic acetylation by acetyl-CoA are unlikely to occur at the mtDNA and that modified free TFAM retains its vital functionalities like compaction and transcription initiation while enhancing transcription processivity.
    Keywords:  Acetylation; DNA compaction; Mitochondrial transcription; Phosphorylation
  14. Mol Cell. 2022 Mar 17. pii: S1097-2765(22)00168-X. [Epub ahead of print]82(6): 1086-1088
      Li et al. (2022) discover that Toxoplasma infection triggers remodeling of the mitochondrial outer membrane through generation of a mitochondrial subdomain termed "structure positive for outer mitochondrial membrane" (SPOT).
  15. Science. 2022 Mar 18. 375(6586): 1254-1261
      Copper is an essential cofactor for all organisms, and yet it becomes toxic if concentrations exceed a threshold maintained by evolutionarily conserved homeostatic mechanisms. How excess copper induces cell death, however, is unknown. Here, we show in human cells that copper-dependent, regulated cell death is distinct from known death mechanisms and is dependent on mitochondrial respiration. We show that copper-dependent death occurs by means of direct binding of copper to lipoylated components of the tricarboxylic acid (TCA) cycle. This results in lipoylated protein aggregation and subsequent iron-sulfur cluster protein loss, which leads to proteotoxic stress and ultimately cell death. These findings may explain the need for ancient copper homeostatic mechanisms.
  16. iScience. 2022 Mar 18. 25(3): 103957
      Babies are born young, largely independent of the age of their mothers. Mother-daughter age asymmetry in yeast is achieved, in part, by inheritance of higher-functioning mitochondria by buds and retention of some high-functioning mitochondria in mother cells. The mitochondrial F box protein, Mfb1p, tethers mitochondria at both poles in a cell cycle-regulated manner: it localizes to and anchors mitochondria at the mother cell tip throughout the cell cycle and at the bud tip before cytokinesis. Here, we report that cell polarity and polarized localization of Mfb1p decline with age in Saccharomyces cerevisiae. Moreover, deletion of genes (BUD1, BUD2, and BUD5) that mediate symmetry breaking during establishment of cell polarity and asymmetric yeast cell division cause depolarized Mfb1p localization and defects in mitochondrial distribution and quality control. Our results support a role for the polarity machinery in lifespan through modulating Mfb1 function in asymmetric inheritance of mitochondria during yeast cell division.
    Keywords:  Biological sciences; Cell biology; Genetics; Molecular biology
  17. Mol Cancer Res. 2022 Mar 17. pii: molcanres.0027.2022. [Epub ahead of print]
      Expression of the fusion oncoprotein EWS/FLI causes Ewing sarcoma, an aggressive pediatric tumor characterized by widespread epigenetic deregulation. These epigenetic changes are targeted by novel lysine specific demethylase-1 (LSD1) inhibitors, which are currently in early phase clinical trials. Single agent targeted therapy often induces resistance, and successful clinical development requires knowledge of resistance mechanisms, enabling the design of effective combination strategies. Here, we used a genome-scale CRISPR-Cas9 loss-of-function screen to identify genes whose knockout (KO) conferred resistance to the LSD1 inhibitor SP-2509 in Ewing sarcoma cell lines. Multiple genes required for mitochondrial electron transport chain (ETC) complexes III and IV function were hits in our screen. We validated this finding using genetic and chemical approaches including CRISPR KO, ETC inhibitors, and mitochondrial depletion. Further global transcriptional profiling revealed that altered complex III/IV function disrupted the oncogenic program mediated by EWS/FLI and LSD1 and blunted the transcriptomic response to SP-2509. Implications: These findings demonstrate that mitochondrial dysfunction modulates SP-2509 efficacy and suggest that new therapeutic strategies combining LSD1 with agents which prevent mitochondrial dysfunction may benefit patients with this aggressive malignancy.
  18. J Exp Clin Cancer Res. 2022 Mar 12. 41(1): 95
      BACKGROUND: Mitochondrial fusion and fission proteins have been nominated as druggable targets in cancer. Whether their inhibition is efficacious in triple negative breast cancer (TNBC) that almost invariably develops chemoresistance is unknown.METHODS: We used a combination of bioinformatics analyses of cancer genomic databases, genetic and pharmacological Optic Atrophy 1 (OPA1) inhibition, mitochondrial function and morphology measurements, micro-RNA (miRNA) profiling and formal epistatic analyses to address the role of OPA1 in TNBC proliferation, migration, and invasion in vitro and in vivo.
    RESULTS: We identified a signature of OPA1 upregulation in breast cancer that correlates with worse prognosis. Accordingly, OPA1 inhibition could reduce breast cancer cells proliferation, migration, and invasion in vitro and in vivo. Mechanistically, while OPA1 silencing did not reduce mitochondrial respiration, it increased levels of miRNAs of the 148/152 family known to inhibit tumor growth and invasiveness. Indeed, these miRNAs were epistatic to OPA1 in the regulation of TNBC cells growth and invasiveness.
    CONCLUSIONS: Our data show that targeted inhibition of the mitochondrial fusion protein OPA1 curtails TNBC growth and nominate OPA1 as a druggable target in TNBC.
  19. Bioelectrochemistry. 2022 Mar 06. pii: S1567-5394(22)00040-8. [Epub ahead of print]145 108089
      Salinomycin (SAL), a polyether antibiotic exerting K+/H+-exchange on cellular membranes, effectively kills cancer stem cells. A series of cationic triphenylphosphonium (TPP+)-linked SAL derivatives were synthesized aiming to render them mitochondria-targeted. Remarkably, attaching a TPP+ moiety via a triazole linker at the C-20 position of SAL (compound 5) preserved the ion carrier potency of the antibiotic, while analogs with TPP+ linked at the C-1 position of SAL (6, 8) were ineffective. On planar bilayer lipid membranes (BLM), the SAL analogs 6 and 8 exhibited slow electrical current relaxation upon a voltage jump, similar to previously studied alkyl-TPP compounds. However, 5 demonstrated much faster current relaxation, which suggested its high permeability through BLM resulting in its pronounced potency to transport potassium and hydrogen ions across both artificial (liposomal) and mitochondrial membranes. SAL and 5 did not induce a steady-state electrical current through the planar lipid bilayer, thereby confirming that the transport mechanism is the electrically silent K+/H+ exchange. The ion exchange mediated by 5 in energized mitochondria was more active than that caused by SAL, which was apparently due to accumulation of 5 in mitochondria. Thus, compound 5 can be regarded as a promising lead compound for testing anticancer and antimicrobial activity.
    Keywords:  Bilayer lipid membrane; Ionophore; K(+)/H(+)-exchange; Liposome; Mitochondria; Salinomycin
  20. IUBMB Life. 2022 Mar 18.
      Multiple mitochondrial matrix enzymes playing key roles in metabolism require cofactors for their action. Due to the high impermeability of the mitochondrial inner membrane, these cofactors need to be synthesized within the mitochondria or be imported, themselves or one of their precursors, into the organelles. Transporters belonging to the protein family of mitochondrial carriers have been identified to transport the coenzymes: thiamine pyrophosphate, coenzyme A, FAD and NAD+ , which are all structurally similar to nucleotides and derived from different B-vitamins. These mitochondrial cofactors bind more or less tightly to their enzymes and, after having been involved in a specific reaction step, are regenerated, spontaneously or by other enzymes, to return to their active form, ready for the next catalysis round. Disease-causing mutations in the mitochondrial cofactor carrier genes compromise not only the transport reaction but also the activity of all mitochondrial enzymes using that particular cofactor and the metabolic pathways in which the cofactor-dependent enzymes are involved. The mitochondrial transport, metabolism and diseases of the cofactors thiamine pyrophosphate, coenzyme A, FAD and NAD+ are the focus of this review.
    Keywords:  coenzyme; coenzyme A; flavin adenine dinucleotide; mitochondria; mitochondrial carrier family SLC25; nicotinamide adenine dinucleotide; thiamine pyrophosphate
  21. Autophagy. 2022 Mar 16. 1-15
      Ethanol increases hepatic mitophagy driven by unknown mechanisms. Type 1 mitophagy sequesters polarized mitochondria for nutrient recovery and cytoplasmic remodeling. In Type 2, mitochondrial depolarization (mtDepo) initiates mitophagy to remove the damaged organelles. Previously, we showed that acute ethanol administration produces reversible hepatic mtDepo. Here, we tested the hypothesis that ethanol-induced mtDepo initiates Type 2 mitophagy. GFP-LC3 transgenic mice were gavaged with ethanol (2-6 g/kg) with and without pre-treatment with agents that decrease or increase mtDepo-Alda-1, tacrolimus, or disulfiram. Without ethanol, virtually all hepatocytes contained polarized mitochondria with infrequent autophagic GFP-LC3 puncta visualized by intravital microscopy. At ~4 h after ethanol treatment, mtDepo occurred in an all-or-none fashion within individual hepatocytes, which increased dose dependently. GFP-LC3 puncta increased in parallel, predominantly in hepatocytes with mtDepo. Mitochondrial PINK1 and PRKN/parkin also increased. After covalent labeling of mitochondria with MitoTracker Red (MTR), GFP-LC3 puncta encircled MTR-labeled mitochondria after ethanol treatment, directly demonstrating mitophagy. GFP-LC3 puncta did not associate with fat droplets visualized with BODIPY558/568, indicating that increased autophagy was not due to lipophagy. Before ethanol administration, rhodamine-dextran (RhDex)-labeled lysosomes showed little association with GFP-LC3. After ethanol treatment, TFEB (transcription factor EB) translocated to nuclei, and lysosomal mass increased. Many GFP-LC3 puncta merged with RhDex-labeled lysosomes, showing autophagosomal processing into lysosomes. After ethanol treatment, disulfiram increased, whereas Alda-1 and tacrolimus decreased mtDepo, and mitophagy changed proportionately. In conclusion, mtDepo after acute ethanol treatment induces mitophagic sequestration and subsequent lysosomal processing.Abbreviations : AcAld, acetaldehyde; ADH, alcohol dehydrogenase; ALDH, aldehyde dehydrogenase; ALD, alcoholic liver disease; Alda-1, N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; LAMP1, lysosomal-associated membrane protein 1; LMNB1, lamin B1; MAA, malondialdehyde-acetaldehyde adducts; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MPT, mitochondrial permeability transition; mtDAMPS, mitochondrial damage-associated molecular patterns; mtDepo, mitochondrial depolarization; mtDNA, mitochondrial DNA; MTR, MitoTracker Red; PI, propidium iodide; PINK1, PTEN induced putative kinase 1; PRKN, parkin; RhDex, rhodamine dextran; TFEB, transcription factor EB; Tg, transgenic; TMRM, tetramethylrhodamine methylester; TOMM20, translocase of outer mitochondrial membrane 20; VDAC, voltage-dependent anion channel.
    Keywords:  Acetaldehyde; Alda-1; alcoholic liver disease; mitochondrial depolarization; mitophagy; tacrolimus
  22. Front Toxicol. 2021 ;3 750431
      Mitochondrial dysfunctions that were not discovered during preclinical and clinical testing have been responsible for at least restriction of use as far as withdrawal of many drugs. To solve mitochondrial machinery complexity, integrative methodologies combining different data, coupled or not to mathematic modelling into systems biology, could represent a strategic way but are still very hard to implement. These technologies should be accurate and precise to avoid accumulation of errors that can lead to misinterpretations, and then alter prediction efficiency. To address such issue, we have developed a versatile functional energy metabolism platform that can measure quantitatively, in parallel, with a very high precision and accuracy, a high number of biological parameters like substrates or enzyme cascade activities in essential metabolism units (glycolysis, respiratory chain ATP production, oxidative stress...) Its versatility (our platform works on either cell lines or small animals and human samples) allows cell metabolism pathways fine tuning comparison from preclinical to clinical studies. Applied here to OXPHOS and/or oxidative stress as an example, it allows discriminating compounds with acute toxic effects but, most importantly, those inducing low noise chronic ones.
    Keywords:  automatisation; cell energetics; functional metabolism; oxidative stress; oxphos
  23. Nano Lett. 2022 Mar 14.
      Uncontrolled growth of tumor cells is highly dependent on the energy metabolism. Fasting-mimicking diet (FMD) is a low-calorie, low-protein, low-sugar diet representing a promising strategy for cancer treatment. However, triglyceride stored in adipose tissue is hydrolyzed into free fatty acids and glycerol for energy supply during FMD treatment. Herein, we design a nutrient-sensing nanodrug, VFETX, which is self-assembled with vitamin B1 (VB1), ferrous ions, and etomoxir (ETX). FMD treatment upregulate the expression of VB1 transporters on tumor cells, thereby increasing cellular uptake and tumor accumulation of VFETX. Importantly, treatments of VFETX and FMD synergistically inhibit the energy metabolism in tumor cells and subsequently markedly enhance cytotoxicity of ETX. As a result, VFETX nanodrugs efficiently inhibit the growth of two tumor models in vivo without obvious side effects. This study demonstrates the potential of FMD-assisted nutrient-sensing nanodrugs for cancer therapy.
    Keywords:  Biomolecule; cancer therapy; fasting-mimicking diet; self-assembly
  24. J Hematol Oncol. 2022 Mar 12. 15(1): 25
      Acute myeloid leukemia (AML) patients suffer dismal prognosis upon treatment resistance. To study functional heterogeneity of resistance, we generated serially transplantable patient-derived xenograft (PDX) models from one patient with AML and twelve clones thereof, each derived from a single stem cell, as proven by genetic barcoding. Transcriptome and exome sequencing segregated clones according to their origin from relapse one or two. Undetectable for sequencing, multiplex fluorochrome-guided competitive in vivo treatment trials identified a subset of relapse two clones as uniquely resistant to cytarabine treatment. Transcriptional and proteomic profiles obtained from resistant PDX clones and refractory AML patients defined a 16-gene score that was predictive of clinical outcome in a large independent patient cohort. Thus, we identified novel genes related to cytarabine resistance and provide proof of concept that intra-tumor heterogeneity reflects inter-tumor heterogeneity in AML.
    Keywords:  Genetic barcoding; Heterogeneity; In vivo treatment; Single cell; Therapy resistance; Xenograft mouse model
  25. Cell Death Dis. 2022 Mar 14. 13(3): 237
      Solute carrier family 25 (SLC25) encodes transport proteins at the inner mitochondrial membrane and functions as carriers for metabolites. Although SLC25 genetic variants correlate with human metabolic diseases, their roles in colon cancer remain unknown. Cases of colon cancer were retrieved from The Cancer Genome Atlas, and the transcriptionally differentially expressed members (DEMs) of SLC25 were identified. DNA level alterations, clinicopathological characteristics, and clinical survival were also investigated. A risk score model based on the DEMs was constructed to further evaluate their prognostic values in a clinical setting. The results were preliminarily validated using bioinformatic analysis of datasets from the Gene Expression Omnibus, immunohistochemical evaluations in clinical specimens, and functional experiments in colon cancer-derived cell lines. Thirty-seven DEMs were identified among 53 members of SLC25. Eight of 37 DEMs were introduced into a risk score model using integrated LASSO regression and multivariate Cox regression. Validated by GSE395282 and GSE175356, DEMs with high-risk scores were associated with the phenotypes of increasing tumor immune infiltration and decreasing glycolysis and apoptosis contents. SLC25A5 was downregulated in cancer, and its upregulation was related to better overall survival in patients from public datasets and in clinical cases. High SLC25A5 expression was an independent prognostic factor for 79 patients after surgical treatment. A negative correlation between CD8 and SLC25A5 was determined in specimens from 106 patients with advanced colon cancer. SLC25A5 attenuated cell proliferation, upregulated the expression of programmed cell death-related signatures, and exerted its biological function by inhibiting the MAPK signaling pathway. Our study reveals that mitochondrial SLC25 has prognostic value in patients with colon cancer. The bioinformatic analyses by following verification in situ and in vitro provide direction for further functional and mechanistic studies on the identified member of SLC25.
  26. J Biol Chem. 2022 Mar 15. pii: S0021-9258(22)00275-7. [Epub ahead of print] 101835
      In cells undergoing cell-intrinsic apoptosis, mitochondrial outer membrane permeabilization (MOMP) typically marks an irreversible step in the cell death process. However, in some cases a subpopulation of treated cells can exhibit a sublethal response, termed "minority MOMP". In this phenomenon, the affected cells survive, despite a low level of caspase activation and subsequent limited activation of the endonuclease CAD (DFFB). Consequently, these cells can experience DNA damage, increasing the probability of oncogenesis. However, little is known about the minority MOMP response. To discover genes that affect the MOMP response in individual cells, we conducted an imaging-based phenotypic siRNA screen. We identified multiple candidate genes whose downregulation increased the heterogeneity of MOMP within single cells, among which were genes related to mitochondrial dynamics and mitophagy that participate in the mitochondrial quality control (MQC) system. Furthermore, to test the hypothesis that functional MQC is important for reducing the frequency of minority MOMP, we developed an assay to measure the clonogenic survival of caspase-engaged cells. We found that cells deficient in various MQC genes were indeed prone to aberrant post-MOMP survival. Our data highlight the important role of proteins involved in mitochondrial dynamics and mitophagy in preventing apoptotic dysregulation and oncogenesis.
    Keywords:  apoptosis; mitochondrial dynamics; mitochondrial heterogeneity; mitochondrial outer membrane permeabilization; mitochondrial quality control; mitophagy; oncogenesis; siRNA screen
  27. Anal Chim Acta. 2022 Apr 08. pii: S0003-2670(22)00192-1. [Epub ahead of print]1201 339621
      Irinotecan (IRI), a topoisomerase I inhibitor blocking DNA synthesis, is a widely used chemotherapy drug for metastatic colorectal cancer. Despite being an effective chemotherapy drug, its clinical effectiveness is limited by both intrinsic and acquired drug resistance. Previous studies indicate IRI induces cancer stemness in irinotecan-resistant (IRI-resistant) cells. Metformin, an oral antidiabetic drug, was recently reported for anticancer effects, likely due to its selective killing of cancer stem cells (CSCs). Given IRI-resistant cells exhibiting high cancer stemness, we hypothesize metformin can sensitize IRI-resistant cells and rescue the therapeutic effect. In this work, we utilized the Single-probe mass spectrometry technique to analyze live IRI-resistant cells under different treatment conditions. We discovered that metformin treatment was associated with the downregulation of lipids and fatty acids, potentially through the inhibition of fatty acid synthase (FASN). Importantly, certain species can be only detected from cells in their living status. The level of synergistic effect of metformin and IRI in their co-treatment of IRI-resistant cells was evaluated using Chou-Talalay combinational index. Using enzymatic activity assay, we determined that the co-treatment exhibit the highest FASN inhibition compared with the mono-treatment of IRI or metformin. To our knowledge, this is the first single-cell MS metabolomics study demonstrating metformin-IRI synergistic effect overcoming drug resistance in IRI-resistant cells.
    Keywords:  Drug-resistant cancer cells; Fatty-acid synthase; Lipidomics; Metabolomics; Metformin; Single cell mass spectrometry
  28. Cancer Res. 2022 Mar 16. pii: canres.4044.2021. [Epub ahead of print]
      Cancer cells are demarcated from normal cells by distinct biological hallmarks, including the reprogramming of metabolic processes. One of the key players involved in metabolic reprogramming is stearoyl-CoA desaturase (SCD), which converts saturated fatty acids to monounsaturated fatty acids in an oxygen-dependent reaction that is crucial for maintaining fatty acid homeostasis. As such, SCD has been identified as a potential therapeutic target in numerous types of cancers, and its inhibition suppresses cancer cell growth in vitro and in vivo. This review summarizes the evidence implicating SCD in cancer progression and proposes novel therapeutic strategies for targeting SCD in solid tumors.
  29. J Chemother. 2022 Mar 14. 1-13
      Therapeutic approaches of advanced colorectal cancer are more complex, here we present a living biobank of patient-derived tumoroids from advanced colorectal cancer patients and show examples of how these tumoroids can be used to to simulate cancer behavior ex vivo and provide more evidence for tumoroids could be utilized as a predictive platform during chemotherapy treatment to identify the chemotherapy response. Morphological, histological and genomic characterization analysis of colorectal cancer tumoroids was conducted. Further, we treated colorectal cancer tumoroids with different drugs to detect cellular activities to evaluate drug sensitivity using CellTiter-Glo 3 D cell viability assay. Then the drug sensitivity of tumoroids was compared with clinical outcomes. Our results implied that tumoroids recapitulated the histological features of the original tumours and genotypic profiling of tumoroids showed a high-level of similarity to the matched primary tumours. Dose-response curves, area under the curve and tumour inhibitory rate of each therapeutic profiling calculations in tumoroids demonstrated a great diversity and we gained 88.24% match ratio between the sensitivity data of tumoroids with their paired patients' clinical outcomes. tumour inhibitory rate of each treatment parameters in tumoroids performed positive correlation with progression-free survival while area under the curve of each treatment parameters performed negative correlation with progression-free survival of the corresponding patients. In summary, We presented a living biobank of tumoroids from advanced colorectal cancer patients and show tumoroids got great potential for predicting clinical responses to chemotherapy treatment of advanced colorectal cancer.
    Keywords:  Tumoroids; advanced colorectal cancer; chemotherapy; living biobank; patient-derived organoids; personalized medicine program
  30. Science. 2022 Mar 18. 375(6586): eaay9040
      Survival improves when cancer is detected early. However, ~50% of cancers are at an advanced stage when diagnosed. Early detection of cancer or precancerous change allows early intervention to try to slow or prevent cancer development and lethality. To achieve early detection of all cancers, numerous challenges must be overcome. It is vital to better understand who is at greatest risk of developing cancer. We also need to elucidate the biology and trajectory of precancer and early cancer to identify consequential disease that requires intervention. Insights must be translated into sensitive and specific early detection technologies and be appropriately evaluated to support practical clinical implementation. Interdisciplinary collaboration is key; advances in technology and biological understanding highlight that it is time to accelerate early detection research and transform cancer survival.