bims-mibica 2022-07-31 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2022‒07‒31
35 papers selected by
Kelsey Fisher-Wellman
East Carolina University

Skeletal progenitors preserve proliferation and self-renewal upon inhibition of mitochondrial respiration by rerouting the TCA cycle.
Alkyl esters of 7-hydroxycoumarin-3-carboxylic acid as potent tissue-specific uncouplers of oxidative phosphorylation: Involvement of ATP/ADP translocase in mitochondrial uncoupling.
EGFR signaling activates intestinal stem cells by promoting mitochondrial biogenesis and β-oxidation.
Mitigation of age-dependent accumulation of defective mitochondrial genomes.
TNK2/ACK1-mediated phosphorylation of ATP5F1A (ATP synthase F1 subunit alpha) selectively augments survival of prostate cancer while engendering mitochondrial vulnerability.
Mitochondrial Elongation and OPA1 Play Crucial Roles during the Stemness Acquisition Process in Pancreatic Ductal Adenocarcinoma.
Targeting lactate dehydrogenase B-dependent mitochondrial metabolism affects tumor initiating cells and inhibits tumorigenesis of non-small cell lung cancer by inducing mtDNA damage.
The ubiquitous expression of pyruvate carboxylase among human prostate tumors.
Aberrant human ClpP activation disturbs mitochondrial proteome homeostasis to suppress pancreatic ductal adenocarcinoma.
Gemcitabine Resistance in Pancreatic Ductal Carcinoma Cell Lines Stems from Reprogramming of Energy Metabolism.
Succinate dehydrogenase inversely regulates red cell distribution width and healthy lifespan in chronically hypoxic mice.
Silencing VDAC1 to Treat Mesothelioma Cancer: Tumor Reprograming and Altering Tumor Hallmarks.
Light-activated mitochondrial fission through optogenetic control of mitochondria-lysosome contacts.
Rapid nutrient depletion to below the physiological range by cancer cells cultured in Plasmax.
PI3K drives the de novo synthesis of coenzyme A from vitamin B5.
Top3α is the replicative topoisomerase in mitochondrial DNA replication.
Metabolic Adaptation-Mediated Cancer Survival and Progression in Oxidative Stress.
Gramicidin A accumulates in mitochondria, reduces ATP levels, induces mitophagy, and inhibits cancer cell growth.
Structures of Atm1 provide insight into [2Fe-2S] cluster export from mitochondria.
SLC38A6, regulated by EP300-mediated modifications of H3K27ac, promotes cell proliferation, glutamine metabolism, and mitochondrial respiration in hepatocellular carcinoma.
O-GlcNAcylation promotes pancreatic tumor growth by regulating malate dehydrogenase 1.
A cancer cell-intrinsic GOT2-PPARd axis suppresses antitumor immunity.
Oxidative Phosphorylation Regulates Interleukin-10 Production in Regulatory B Cells via the Extracellular Signal-related Kinase Pathway.
Quantitative Proteome Analysis Reveals Melissa officinalis Extract Targets Mitochondrial Respiration in Colon Cancer Cells.
The hexokinase "HKDC1" interaction with the mitochondria is essential for liver cancer progression.
Targeting de novo lipogenesis and the Lands cycle induces ferroptosis in KRAS-mutant lung cancer.
Akt protein boosts cancer metabolism through a two-pronged attack.
Autophagic secretion of mitochondria (ASM): An alternative way for getting rid of damaged mitochondria.
GOT2 Silencing Promotes Reprogramming of Glutamine Metabolism and Sensitizes Hepatocellular Carcinoma to Glutaminase Inhibitors.
Metabolic balance in colorectal cancer is maintained by optimal Wnt signaling levels.
Loss of sphingosine kinase 2 promotes the expansion of hematopoietic stem cells by improving their metabolic fitness.
Lactate promotes metastasis of normoxic colorectal cancer stem cells through PGC-1α-mediated oxidative phosphorylation.
Melatonin Reverses the Warburg-Type Metabolism and Reduces Mitochondrial Membrane Potential of Ovarian Cancer Cells Independent of MT1 Receptor Activation.
Targeting Acute Myeloid Leukemia with Venetoclax; Biomarkers for Sensitivity and Rationale for Venetoclax-Based Combination Therapies.
Mitochondrial surface coating with artificial lipid membrane improves the transfer efficacy.

Cell Rep. 2022 Jul 26. pii: S2211-1247(22)00907-X. [Epub ahead of print]40(4): 111105

Skeletal progenitors preserve proliferation and self-renewal upon inhibition of mitochondrial respiration by rerouting the TCA cycle.

Guillaume Tournaire, Shauni Loopmans, Steve Stegen, Gianmarco Rinaldi, Guy Eelen, Sophie Torrekens, Karen Moermans, Peter Carmeliet, Bart Ghesquière, Bernard Thienpont, Sarah-Maria Fendt, Nick van Gastel, Geert Carmeliet.

  A functional electron transport chain (ETC) is crucial for supporting bioenergetics and biosynthesis. Accordingly, ETC inhibition decreases proliferation in cancer cells but does not seem to impair stem cell proliferation. However, it remains unclear how stem cells metabolically adapt. In this study, we show that pharmacological inhibition of complex III of the ETC in skeletal stem and progenitor cells induces glycolysis side pathways and reroutes the tricarboxylic acid (TCA) cycle to regenerate NAD+ and preserve cell proliferation. These metabolic changes also culminate in increased succinate and 2-hydroxyglutarate levels that inhibit Ten-eleven translocation (TET) DNA demethylase activity, thereby preserving self-renewal and multilineage potential. Mechanistically, mitochondrial malate dehydrogenase and reverse succinate dehydrogenase activity proved to be essential for the metabolic rewiring in response to ETC inhibition. Together, these data show that the metabolic plasticity of skeletal stem and progenitor cells allows them to bypass ETC blockade and preserve their self-renewal.

Keywords:  CP: Metabolism; CP: Stem cell research; NAD regeneration; TCA rerouting; TET activity; cell-based regenerative medicine; electron transport chain; metabolic plasticity; proliferation; reverse succinate dehydrogenase; self-renewal; skeletal stem cells

DOI:  https://doi.org/10.1016/j.celrep.2022.111105
Arch Biochem Biophys. 2022 Jul 22. pii: S0003-9861(22)00250-8. [Epub ahead of print] 109366

Alkyl esters of 7-hydroxycoumarin-3-carboxylic acid as potent tissue-specific uncouplers of oxidative phosphorylation: Involvement of ATP/ADP translocase in mitochondrial uncoupling.

Vladimir S Krasnov, Roman S Kirsanov, Ljudmila S Khailova, Lyudmila B Popova, Konstantin G Lyamzaev, Alexander M Firsov, Galina A Korshunova, Elena A Kotova, Yuri N Antonenko.

  An impressive body of evidence has been accumulated now on sound beneficial effects of mitochondrial uncouplers in struggling with the most dangerous pathologies such as cancer, infective diseases, neurodegeneration and obesity. To increase their efficacy while gaining further insight in the mechanism of the uncoupling action has been remaining a challenge. Encouraged by our previous promising results on lipophilic derivatives of 7-hydroxycoumarin-4-acetic acid (UB-4 esters), here, we use a 7-hydroxycoumarin-3-carboxylic acid scaffold to synthesize a new series of 7-hydroxycoumarin (umbelliferone, UB)-derived uncouplers of oxidative phosphorylation - alkyl esters of umbelliferone-3-carboxylic acid (UB-3 esters) with varying carbon chain length. Compared to the UB-4 derivatives, UB-3 esters proved to be stronger uncouplers: the most effective of them caused a pronounced increase in the respiration rate of isolated rat heart mitochondria (RHM) at submicromolar concentrations. Both of these series of UB derivatives exhibited a striking difference between their uncoupling patterns in mitochondria isolated from liver and heart or kidney, namely: a pronounced but transient decrease in membrane potential, followed by its recovery, was observed after the addition of these compounds to isolated rat liver mitochondria (RLM), while the depolarization of RHM and rat kidney mitochondria (RKM) was rather stable under the same conditions. Interestingly, partial reversal of this depolarization in RHM and RKM was caused by carboxyatractyloside, an inhibitor of ATP/ADP translocase, thereby pointing to the involvement of this mitochondrial membrane protein in the uncoupling activity of both UB-3 and UB-4 esters. The fast membrane potential recovery in RLM uncoupled by the addition of the UB esters was apparently associated with hydrolysis of these compounds, catalyzed by mitochondrial aldehyde dehydrogenase (ALDH2), being in high abundance in liver compared to other tissues. Protonophoric properties of the UB derivatives in isolated mitochondria were confirmed by measurements of RHM swelling in the presence of potassium acetate. In model bilayer lipid membranes (BLM), proton-carrying activity of UB-3 esters was demonstrated by measuring fluorescence response of the pH-dependent dye pyranine in liposomes. Electrophysiological experiments on identified neurons from Lymnaea stagnalis demonstrated low neurotoxicity of UB-3 esters. Resazurin-based cell viability assay showed low toxicity of UB-3 esters to HEK293 cells and primary human fibroblasts. Thus, the present results enable us to consider UB-3 esters as effective tissue-specific protonophoric mitochondrial uncouplers.

Keywords:  7-Hydroxycoumarin; ATP/ADP translocase; Mitochondrial aldehyde dehydrogenase; OxPhos uncoupler; Protonophore; Rat heart mitochondria

DOI:  https://doi.org/10.1016/j.abb.2022.109366
Curr Biol. 2022 Jul 19. pii: S0960-9822(22)01104-6. [Epub ahead of print]

EGFR signaling activates intestinal stem cells by promoting mitochondrial biogenesis and β-oxidation.

Chenge Zhang, Yinhua Jin, Marco Marchetti, Mitchell R Lewis, Omar T Hammouda, Bruce A Edgar.

  EGFR-RAS-ERK signaling promotes growth and proliferation in many cell types, and genetic hyperactivation of RAS-ERK signaling drives many cancers. Yet, despite intensive study of upstream components in EGFR signal transduction, the identities and functions of downstream effectors in the pathway are poorly understood. In Drosophila intestinal stem cells (ISCs), the transcriptional repressor Capicua (Cic) and its targets, the ETS-type transcriptional activators Pointed (pnt) and Ets21C, are essential downstream effectors of mitogenic EGFR signaling. Here, we show that these factors promote EGFR-dependent metabolic changes that increase ISC mass, mitochondrial growth, and mitochondrial activity. Gene target analysis using RNA and DamID sequencing revealed that Pnt and Ets21C directly upregulate not only DNA replication and cell cycle genes but also genes for oxidative phosphorylation, the TCA cycle, and fatty acid beta-oxidation. Metabolite analysis substantiated these metabolic functions. The mitochondrial transcription factor B2 (mtTFB2), a direct target of Pnt, was required and partially sufficient for EGFR-driven ISC growth, mitochondrial biogenesis, and proliferation. MEK-dependent EGF signaling stimulated mitochondrial biogenesis in human RPE-1 cells, indicating the conservation of these metabolic effects. This work illustrates how EGFR signaling alters metabolism to coordinately activate cell growth and cell division.

Keywords:  Ets21C; ISC; Pointed; intestinal stem cell; mitochondrial biogenesis; mtTFB2; proliferation

DOI:  https://doi.org/10.1016/j.cub.2022.07.003
Proc Natl Acad Sci U S A. 2022 Aug 02. 119(31): e2119009119

Mitigation of age-dependent accumulation of defective mitochondrial genomes.

Pei-I Tsai, Ekaterina Korotkevich, Patrick H O'Farrell.

  Unknown processes promote the accumulation of mitochondrial DNA (mtDNA) mutations during aging. Accumulation of defective mitochondrial genomes is thought to promote the progression of heteroplasmic mitochondrial diseases and degenerative changes with natural aging. We used a heteroplasmic Drosophila model to test 1) whether purifying selection acts to limit the abundance of deleterious mutations during development and aging, 2) whether quality control pathways contribute to purifying selection, 3) whether activation of quality control can mitigate accumulation of deleterious mutations, and 4) whether improved quality control improves health span. We show that purifying selection operates during development and growth but is ineffective during aging. Genetic manipulations suggest that a quality control process known to enforce purifying selection during oogenesis also suppresses accumulation of a deleterious mutation during growth and development. Flies with nuclear genotypes that enhance purifying selection sustained higher genome quality, retained more vigorous climbing activity, and lost fewer dopaminergic neurons. A pharmacological agent thought to enhance quality control produced similar benefits. Importantly, similar pharmacological treatment of aged mice reversed age-associated accumulation of a deleterious mtDNA mutation. Our findings reveal dynamic maintenance of mitochondrial genome fitness and reduction in the effectiveness of purifying selection during life. Importantly, we describe interventions that mitigate and even reverse age-associated genome degeneration in flies and in mice. Furthermore, mitigation of genome degeneration improved well-being in a Drosophila model of heteroplasmic mitochondrial disease.

Keywords:  aging; heteroplasmy; mitochondria; mtDNA; mutations

DOI:  https://doi.org/10.1073/pnas.2119009119
Autophagy. 2022 Jul 27. 1-26

TNK2/ACK1-mediated phosphorylation of ATP5F1A (ATP synthase F1 subunit alpha) selectively augments survival of prostate cancer while engendering mitochondrial vulnerability.

Surbhi Chouhan, Mithila Sawant, Cody Weimholt, Jingqin Luo, Robert W Sprung, Mailyn Terrado, David M Mueller, H Shelton Earp, Nupam P Mahajan.

  The challenge of rapid macromolecular synthesis enforces the energy-hungry cancer cell mitochondria to switch their metabolic phenotypes, accomplished by activation of oncogenic tyrosine kinases. Precisely how kinase activity is directly exploited by cancer cell mitochondria to meet high-energy demand, remains to be deciphered. Here we show that a non-receptor tyrosine kinase, TNK2/ACK1 (tyrosine kinase non receptor 2), phosphorylated ATP5F1A (ATP synthase F1 subunit alpha) at Tyr243 and Tyr246 (Tyr200 and 203 in the mature protein, respectively) that not only increased the stability of complex V, but also increased mitochondrial energy output in cancer cells. Further, phospho-ATP5F1A (p-Y-ATP5F1A) prevented its binding to its physiological inhibitor, ATP5IF1 (ATP synthase inhibitory factor subunit 1), causing sustained mitochondrial activity to promote cancer cell growth. TNK2 inhibitor, (R)-9b reversed this process and induced mitophagy-based autophagy to mitigate prostate tumor growth while sparing normal prostate cells. Further, depletion of p-Y-ATP5F1A was needed for (R)-9b-mediated mitophagic response and tumor growth. Moreover, Tnk2 transgenic mice displayed increased p-Y-ATP5F1A and loss of mitophagy and exhibited formation of prostatic intraepithelial neoplasia (PINs). Consistent with these data, a marked increase in p-Y-ATP5F1A was seen as prostate cancer progressed to the malignant stage. Overall, this study uncovered the molecular intricacy of tyrosine kinase-mediated mitochondrial energy regulation as a distinct cancer cell mitochondrial vulnerability and provided evidence that TNK2 inhibitors can act as "mitocans" to induce cancer-specific mitophagy.AbbreviationsATP5F1A: ATP synthase F1 subunit alpha; ATP5IF1: ATP synthase inhibitory factor subunit 1; CRPC: castration-resistant prostate cancer; DNM1L: dynamin 1 like; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; Mdivi-1: mitochondrial division inhibitor 1; Mut-ATP5F1A: Y243,246A mutant of ATP5F1A; OXPHOS: oxidative phosphorylation; PC: prostate cancer; PINK1: PTEN induced kinase 1; p-Y-ATP5F1A: phosphorylated tyrosine 243 and 246 on ATP5F1A; TNK2/ACK1: tyrosine kinase non receptor 2; Ub: ubiquitin; WT: wild type.

Keywords:  ATP5F1A; ATP5IF1; TNK2/ACK1; mitochondrial dysfunction; mitochondrial vulnerability; mitophagy; tyrosine phosphorylation

DOI:  https://doi.org/10.1080/15548627.2022.2103961
Cancers (Basel). 2022 Jul 14. pii: 3432. [Epub ahead of print]14(14):

Mitochondrial Elongation and OPA1 Play Crucial Roles during the Stemness Acquisition Process in Pancreatic Ductal Adenocarcinoma.

Cristian Andres Carmona-Carmona, Elisa Dalla Pozza, Giulia Ambrosini, Barbara Cisterna, Marta Palmieri, Ilaria Decimo, José M Cuezva, Emanuela Bottani, Ilaria Dando.

  Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer with an overall 5-year survival rate of less than 9%. The high aggressiveness of PDAC is linked to the presence of a subpopulation of cancer cells with a greater tumorigenic capacity, generically called cancer stem cells (CSCs). CSCs present a heterogeneous metabolic profile that might be supported by an adaptation of mitochondrial function; however, the role of this organelle in the development and maintenance of CSCs remains controversial. To determine the role of mitochondria in CSCs over longer periods, which may reflect more accurately their quiescent state, we studied the mitochondrial physiology in CSCs at short-, medium-, and long-term culture periods. We found that CSCs show a significant increase in mitochondrial mass, more mitochondrial fusion, and higher mRNA expression of genes involved in mitochondrial biogenesis than parental cells. These changes are accompanied by a regulation of the activities of OXPHOS complexes II and IV. Furthermore, the protein OPA1, which is involved in mitochondrial dynamics, is overexpressed in CSCs and modulates the tumorsphere formation. Our findings indicate that CSCs undergo mitochondrial remodeling during the stemness acquisition process, which could be exploited as a promising therapeutic target against pancreatic CSCs.

Keywords:  OPA1; cancer stem cells; mitochondrial dynamics; mitochondrial fusion; pancreatic ductal adenocarcinoma

DOI:  https://doi.org/10.3390/cancers14143432
Cell Mol Life Sci. 2022 Jul 25. 79(8): 445

Targeting lactate dehydrogenase B-dependent mitochondrial metabolism affects tumor initiating cells and inhibits tumorigenesis of non-small cell lung cancer by inducing mtDNA damage.

Haibin Deng, Yanyun Gao, Verdiana Trappetti, Damian Hertig, Darya Karatkevich, Tereza Losmanova, Christian Urzi, Huixiang Ge, Gerrit Adriaan Geest, Remy Bruggmann, Valentin Djonov, Jean-Marc Nuoffer, Peter Vermathen, Nicola Zamboni, Carsten Riether, Adrian Ochsenbein, Ren-Wang Peng, Gregor Jan Kocher, Ralph Alexander Schmid, Patrick Dorn, Thomas Michael Marti.

  Once considered a waste product of anaerobic cellular metabolism, lactate has been identified as a critical regulator of tumorigenesis, maintenance, and progression. The putative primary function of lactate dehydrogenase B (LDHB) is to catalyze the conversion of lactate to pyruvate; however, its role in regulating metabolism during tumorigenesis is largely unknown. To determine whether LDHB plays a pivotal role in tumorigenesis, we performed 2D and 3D in vitro experiments, utilized a conventional xenograft tumor model, and developed a novel genetically engineered mouse model (GEMM) of non-small cell lung cancer (NSCLC), in which we combined an LDHB deletion allele with an inducible model of lung adenocarcinoma driven by the concomitant loss of p53 (also known as Trp53) and expression of oncogenic KRAS (G12D) (KP). Here, we show that epithelial-like, tumor-initiating NSCLC cells feature oxidative phosphorylation (OXPHOS) phenotype that is regulated by LDHB-mediated lactate metabolism. We show that silencing of LDHB induces persistent mitochondrial DNA damage, decreases mitochondrial respiratory complex activity and OXPHOS, resulting in reduced levels of mitochondria-dependent metabolites, e.g., TCA intermediates, amino acids, and nucleotides. Inhibition of LDHB dramatically reduced the survival of tumor-initiating cells and sphere formation in vitro, which can be partially restored by nucleotide supplementation. In addition, LDHB silencing reduced tumor initiation and growth of xenograft tumors. Furthermore, we report for the first time that homozygous deletion of LDHB significantly reduced lung tumorigenesis upon the concomitant loss of Tp53 and expression of oncogenic KRAS without considerably affecting the animal's health status, thereby identifying LDHB as a potential target for NSCLC therapy. In conclusion, our study shows for the first time that LDHB is essential for the maintenance of mitochondrial metabolism, especially nucleotide metabolism, demonstrating that LDHB is crucial for the survival and proliferation of NSCLC tumor-initiating cells and tumorigenesis.

Keywords:  Cancer stem cells; Cellular plasticity; Lung cancer; Mitochondrial DNA; Mitochondrial metabolism; Nucleotide metabolism; Tumorigenicity

DOI:  https://doi.org/10.1007/s00018-022-04453-5
Bratisl Lek Listy. 2022 ;123(7): 487-490

The ubiquitous expression of pyruvate carboxylase among human prostate tumors.

Eduard Gondas, Mark Hives, Jan Kliment, Monika Kmetova Sivonova, Dusan Dobrota, Radovan Murin.

Pyruvate carboxylase (PC) is a mitochondrial enzyme catalyzing the ATP-dependent reaction of pyruvate prolongation with bicarbonate ion to oxaloacetate. The synthesis of oxaloacetate by PC, an intermediate of the Krebs cycle, is recently recognized as a significant anaplerotic reaction that supports the biosynthetic capability, growth, aggressiveness, and even viability of several cancer cell types. PC expression was confirmed in several types of cancer cells and tumors. To evaluate the possibility that prostate tumor-forming cells are also exploiting the anaplerotic role of PC, we applied immunoblotting analysis to estimate its presence. Our results revealed that PC is present among the lysate proteins derived from prostate cancer and benign prostatic hyperplasia samples. The expression of PC in cells of prostate tumors and benign prostatic hyperplasia supposes that PC could facilitate the formation of oxaloacetate in situ and enhance the autonomy of their biosynthetic metabolism from the availability of extracellular substrates by increasing the cellular anaplerotic capability (Tab. 1, Fig. 1, Ref. 30). Keywords: pyruvate carboxylase, prostate cancer, cancer metabolism, anaplerosis.

DOI: https://doi.org/10.4149/BLL_2022_077
Cell Chem Biol. 2022 Jul 20. pii: S2451-9456(22)00245-8. [Epub ahead of print]

Aberrant human ClpP activation disturbs mitochondrial proteome homeostasis to suppress pancreatic ductal adenocarcinoma.

Pengyu Wang, Tao Zhang, Xinjing Wang, Hongying Xiao, Huiti Li, Lin-Lin Zhou, Teng Yang, Bingyan Wei, Zeyun Zhu, Lu Zhou, Song Yang, Xiongxiong Lu, Yonghui Zhang, Yue Huang, Jianhua Gan, Cai-Guang Yang.

  The mitochondrial caseinolytic protease P (ClpP) is a target candidate for treating leukemia; however, the effects of ClpP modulation on solid tumors have not been adequately explored. Here, we report a potent activator of ClpP with the therapeutic potential for pancreatic ductal adenocarcinoma (PDAC). We first validated that aberrant ClpP activation leads to growth arrest of PDAC cells and tumors. We then performed high-throughput screening and synthetic optimization, from which we identified ZG111, a potent activator of ClpP. ZG111 binds to ClpP and promotes the ClpP-mediated degradation of respiratory chain complexes. This degradation activates the JNK/c-Jun pathway, induces the endoplasmic reticulum stress response, and consequently causes the growth arrest of PDAC cells. ZG111 also produces inhibitory effects on tumor growth in cell line-derived and patient-derived xenograft mouse models. Altogether, our data demonstrate a promising therapeutic strategy for PDAC suppression through the chemical activation of ClpP.

Keywords:  ClpP activator; cancer therapy; mitochondrial proteome homeostasis; oxidative phosphorylation; pancreatic ductal adenocarcinoma; respiratory chain complexes; target validation

DOI:  https://doi.org/10.1016/j.chembiol.2022.07.002
Int J Mol Sci. 2022 Jul 15. pii: 7824. [Epub ahead of print]23(14):

Gemcitabine Resistance in Pancreatic Ductal Carcinoma Cell Lines Stems from Reprogramming of Energy Metabolism.

Rina Fujiwara-Tani, Takamitsu Sasaki, Tadataka Takagi, Shiori Mori, Shingo Kishi, Yukiko Nishiguchi, Hitoshi Ohmori, Kiyomu Fujii, Hiroki Kuniyasu.

  Pancreatic ductal adenocarcinoma (PDAC) is associated with poor prognosis because it is often detected at an advanced stage, and drug resistance interferes with treatment. However, the mechanism underlying drug resistance in PDAC remains unclear. Here, we investigated metabolic changes between a parental PDAC cell line and a gemcitabine (GEM)-resistant PDAC cell line. We established a GEM-resistant cell line, MIA-G, from MIA-PaCa-2 parental (MIA-P) cells using continuous therapeutic-dose GEM treatment. MIA-G cells were also more resistant to 5-fluorouracil in comparison to MIA-P cells. Metabolic flux analysis showed a higher oxygen consumption rate (OCR) in MIA-G cells than in MIA-P cells. Notably, OCR was suppressed by GEM treatment only in MIA-G cells. GEM treatment increased mitochondrial membrane potential and mitochondrial reactive oxygen species (ROS) in MIA-P cells, but not in MIA-G cells. Glutamine uptake and peroxidase levels were elevated in MIA-G cells. The antioxidants N-acetyl-L-cysteine and vitamin C increased the sensitivity to GEM in both cell lines. In MIA-G cells, the expression of the mitochondrial transcription factor A also decreased. Furthermore, rotenone reduced the sensitivity of MIA-P cells to GEM. These findings suggest that the suppression of oxidative phosphorylation contributes to GEM resistance by reducing ROS production. Our study provides a new approach for reducing GEM resistance in PDAC.

Keywords:  ROS; drug resistance; energy metabolism; gemcitabine; pancreatic ductal carcinoma

DOI:  https://doi.org/10.3390/ijms23147824
JCI Insight. 2022 Jul 26. pii: e158737. [Epub ahead of print]

Succinate dehydrogenase inversely regulates red cell distribution width and healthy lifespan in chronically hypoxic mice.

Bora E Baysal, Abdulrahman A Alahmari, Tori C Rodrick, Debra Tabaczynski, Leslie Curtin, Mukund Seshadri, Drew R Jones, Sandra Sexton.

  Increased red cell distribution width (RDW), which measures erythrocyte volume (MCV) variability (anisocytosis), has been linked to early mortality in many diseases and in older adults through unknown mechanisms. Hypoxic stress has been proposed as a potential mechanism. However, experimental models to investigate the link between increased RDW and reduced survival are lacking. Here, we show that lifelong hypobaric hypoxia (~10% O2) increases erythrocyte numbers, hemoglobin and RDW, while reducing longevity in male mice. Compound heterozygous knockout (chKO) mutations in succinate dehydrogenase (Sdh; mitochondrial complex II) genes Sdhb, Sdhc and Sdhd reduce Sdh subunit protein levels, RDW, and increase healthy lifespan compared to wild-type (WT) mice in chronic hypoxia. RDW-SD, a direct measure of MCV variability, and the standard deviation of MCV (1SD-RDW) show the most statistically significant reductions in Sdh hKO mice. Tissue metabolomic profiling of 147 common metabolites shows the largest increase in succinate with elevated succinate to fumarate and succinate to oxoglutarate (2-ketoglutarate) ratios in Sdh hKO mice. These results demonstrate that mitochondrial complex II level is an underlying determinant of both RDW and healthy lifespan in hypoxia, and suggest that therapeutic targeting of Sdh might reduce high RDW-associated clinical mortality in hypoxic diseases.

Keywords:  Hematology; Hypoxia; Mitochondria; Pulmonology

DOI:  https://doi.org/10.1172/jci.insight.158737
Biomolecules. 2022 Jun 27. pii: 895. [Epub ahead of print]12(7):

Silencing VDAC1 to Treat Mesothelioma Cancer: Tumor Reprograming and Altering Tumor Hallmarks.

Swaroop Kumar Pandey, Renen Machlof-Cohen, Manikandan Santhanam, Anna Shteinfer-Kuzmine, Varda Shoshan-Barmatz.

  Mesothelioma, an aggressive cancer with a poor prognosis, is linked to asbestos exposure. However, carbon nanotubes found in materials we are exposed to daily can cause mesothelioma cancer. Cancer cells reprogram their metabolism to support increased biosynthetic and energy demands required for their growth and motility. Here, we examined the effects of silencing the expression of the voltage-dependent anion channel 1 (VDAC1), controlling the metabolic and energetic crosstalk between mitochondria and the rest of the cell. We demonstrate that VDAC1 is overexpressed in mesothelioma patients; its levels increase with disease stage and are associated with low survival rates. Silencing VDAC1 expression using a specific siRNA identifying both mouse and human VDAC1 (si-m/hVDAC1-B) inhibits cell proliferation of mesothelioma cancer cells. Treatment of xenografts of human-derived H226 cells or mouse-derived AB1 cells with si-m/hVDAC1-B inhibited tumor growth and caused metabolism reprogramming, as reflected in the decreased expression of metabolism-related proteins, including glycolytic and tricarboxylic acid (-)cycle enzymes and the ATP-synthesizing enzyme. In addition, tumors depleted of VDAC1 showed altered microenvironments and inflammation, both associated with cancer progression. Finally, tumor VDAC1 silencing also eliminated cancer stem cells and induced cell differentiation to normal-like cells. The results show that silencing VDAC1 expression leads to reprogrammed metabolism and to multiple effects from tumor growth inhibition to modulation of the tumor microenvironment and inflammation, inducing differentiation of malignant cells. Thus, silencing VDAC1 is a potential therapeutic approach to treating mesothelioma.

Keywords:  VDAC1; mesothelioma; metabolism; mitochondria

DOI:  https://doi.org/10.3390/biom12070895
Nat Commun. 2022 Jul 25. 13(1): 4303

Light-activated mitochondrial fission through optogenetic control of mitochondria-lysosome contacts.

Kangqiang Qiu, Weiwei Zou, Hongbao Fang, Mingang Hao, Kritika Mehta, Zhiqi Tian, Jun-Lin Guan, Kai Zhang, Taosheng Huang, Jiajie Diao.

Mitochondria are highly dynamic organelles whose fragmentation by fission is critical to their functional integrity and cellular homeostasis. Here, we develop a method via optogenetic control of mitochondria-lysosome contacts (MLCs) to induce mitochondrial fission with spatiotemporal accuracy. MLCs can be achieved by blue-light-induced association of mitochondria and lysosomes through various photoactivatable dimerizers. Real-time optogenetic induction of mitochondrial fission is tracked in living cells to measure the fission rate. The optogenetic method partially restores the mitochondrial functions of SLC25A46-/- cells, which display defects in mitochondrial fission and hyperfused mitochondria. The optogenetic MLCs system thus provides a platform for studying mitochondrial fission and treating mitochondrial diseases.

DOI: https://doi.org/10.1038/s41467-022-31970-5
Am J Physiol Cell Physiol. 2022 Jul 25.

Rapid nutrient depletion to below the physiological range by cancer cells cultured in Plasmax.

Georgina Gardner, Feresteh Moradi, Christopher Moffatt, Meagan Cliche, Bianca Garlisi, John Gratton, Fatima Mehmood, Jeffrey A Stuart.

  Mammalian cell culture is a fundamental tool used to study living cells. Presently, the standard protocol for performing cell culture involves the use of commercial media that contain an excess of nutrients. While this reduces the likelihood of cell starvation, it creates non-physiologic culture conditions that have been shown to 're-wire' cellular metabolism. Recently, researchers have developed new media like Plasmax, formulated to approximate the nutrient composition of human blood plasma. Although this represents an improvement in cell culture practice, physiologic media may be vulnerable to nutrient depletion. In this study we directly addressed this concern by measuring the rates of glucose and amino acid depletion from Plasmax in several cancer cell lines (PC-3, LNCaP, MCF-7, SH-SY5Y) over 48 hours. In all cell lines, depletion of glucose from Plasmax was rapid such that, by 48h, cells were hypoglycemic (<2mM glucose). Most amino acids were similarly rapidly depleted to sub-physiological levels by 48h. In contrast, glucose and most amino acids remained within the physiological range at 24h. When the experiment was done at physiological oxygen (5%) versus standard (18%)with LNCaP cells, no effect on glucose or amino acid consumption was observed. Using RNA sequencing, we show that this nutrient depletion is associated with enrichment of starvation responses, apoptotic signalling, and endoplasmic reticulum stress. A shift from glycolytic metabolism to mitochondrial respiration at 5% O2 was also measured using Seahorse analysis. Taken together, these results exemplify the metabolic considerations for Plasmax, highlighting that cell culture in Plasmax requires daily media exchange.

Keywords:  amino acids; metabolism; metabolomics; physiologic cell culture; physioxia

DOI:  https://doi.org/10.1152/ajpcell.00403.2021
Nature. 2022 Jul 27.

PI3K drives the de novo synthesis of coenzyme A from vitamin B5.

Christian C Dibble, Samuel A Barritt, Grace E Perry, Evan C Lien, Renee C Geck, Sarah E DuBois-Coyne, David Bartee, Thomas T Zengeya, Emily B Cohen, Min Yuan, Benjamin D Hopkins, Jordan L Meier, John G Clohessy, John M Asara, Lewis C Cantley, Alex Toker.

In response to hormones and growth factors, the class I phosphoinositide-3-kinase (PI3K) signalling network functions as a major regulator of metabolism and growth, governing cellular nutrient uptake, energy generation, reducing cofactor production and macromolecule biosynthesis1. Many of the driver mutations in cancer with the highest recurrence, including in receptor tyrosine kinases, Ras, PTEN and PI3K, pathologically activate PI3K signalling2,3. However, our understanding of the core metabolic program controlled by PI3K is almost certainly incomplete. Here, using mass-spectrometry-based metabolomics and isotope tracing, we show that PI3K signalling stimulates the de novo synthesis of one of the most pivotal metabolic cofactors: coenzyme A (CoA). CoA is the major carrier of activated acyl groups in cells4,5 and is synthesized from cysteine, ATP and the essential nutrient vitamin B5 (also known as pantothenate)6,7. We identify pantothenate kinase 2 (PANK2) and PANK4 as substrates of the PI3K effector kinase AKT8. Although PANK2 is known to catalyse the rate-determining first step of CoA synthesis, we find that the minimally characterized but highly conserved PANK49 is a rate-limiting suppressor of CoA synthesis through its metabolite phosphatase activity. Phosphorylation of PANK4 by AKT relieves this suppression. Ultimately, the PI3K-PANK4 axis regulates the abundance of acetyl-CoA and other acyl-CoAs, CoA-dependent processes such as lipid metabolism and proliferation. We propose that these regulatory mechanisms coordinate cellular CoA supplies with the demands of hormone/growth-factor-driven or oncogene-driven metabolism and growth.

DOI: https://doi.org/10.1038/s41586-022-04984-8
Nucleic Acids Res. 2022 Jul 29. pii: gkac660. [Epub ahead of print]

Top3α is the replicative topoisomerase in mitochondrial DNA replication.

Anu Hangas, Nina J Kekäläinen, Alisa Potter, Craig Michell, Kauko J Aho, Chiara Rutanen, Johannes N Spelbrink, Jaakko L Pohjoismäki, Steffi Goffart.

Mitochondrial DNA has been investigated for nearly fifty years, but many aspects of the maintenance of this essential small genome remain unknown. Like any genome, mammalian mitochondrial DNA requires the function of topoisomerases to counter and regulate the topological tension arising during replication, transcription, segregation, and repair. However, the functions of the different mitochondrial topoisomerases are poorly understood. Here, we investigate the role of Topoisomerase 3α (Top3α) in mtDNA replication and transcription, providing evidence that this enzyme, previously reported to act in mtDNA segregation, also participates in mtDNA replication fork progression. Top3α knockdown caused replication fork stalling, increased mtDNA catenation and decreased mtDNA levels. Overexpression in contrast induced abundant double-strand breaks around the replication origin OH and abortion of early replication, while at the same time improving the resolution of mtDNA replication termination intermediates. Both Top3α knockdown and overexpression affected mitochondrial RNA transcription, leading to a decrease in steady-state levels of mitochondrial transcripts. Together, our results indicate that the mitochondrial isoform of Top3α is not only involved in mtDNA segregation, as reported previously, but also supports the progression of the replication fork. Mitochondrial Top3α is also influencing the progression of transcription, with its absence affecting downstream transcript levels.

DOI: https://doi.org/10.1093/nar/gkac660
Antioxidants (Basel). 2022 Jul 05. pii: 1324. [Epub ahead of print]11(7):

Metabolic Adaptation-Mediated Cancer Survival and Progression in Oxidative Stress.

Yongquan Tang, Zhe Zhang, Yan Chen, Siyuan Qin, Li Zhou, Wei Gao, Zhisen Shen.

  Undue elevation of ROS levels commonly occurs during cancer evolution as a result of various antitumor therapeutics and/or endogenous immune response. Overwhelming ROS levels induced cancer cell death through the dysregulation of ROS-sensitive glycolytic enzymes, leading to the catastrophic depression of glycolysis and oxidative phosphorylation (OXPHOS), which are critical for cancer survival and progression. However, cancer cells also adapt to such catastrophic oxidative and metabolic stresses by metabolic reprograming, resulting in cancer residuality, progression, and relapse. This adaptation is highly dependent on NADPH and GSH syntheses for ROS scavenging and the upregulation of lipolysis and glutaminolysis, which fuel tricarboxylic acid cycle-coupled OXPHOS and biosynthesis. The underlying mechanism remains poorly understood, thus presenting a promising field with opportunities to manipulate metabolic adaptations for cancer prevention and therapy. In this review, we provide a summary of the mechanisms of metabolic regulation in the adaptation of cancer cells to oxidative stress and the current understanding of its regulatory role in cancer survival and progression.

Keywords:  cancer stemness; metabolic adaptation; metabolic reprogramming; oxidative stress; tumor metastasis

DOI:  https://doi.org/10.3390/antiox11071324
Chem Sci. 2022 Jun 29. 13(25): 7482-7491

Gramicidin A accumulates in mitochondria, reduces ATP levels, induces mitophagy, and inhibits cancer cell growth.

Yun-Wei Xue, Hiroaki Itoh, Shingo Dan, Masayuki Inoue.

Gramicidin A (1) is a linear 15-mer peptidic natural product. Because of its sequence of alternating d- and l-chirality, 1 folds into a β6.3-helix in a lipid bilayer and forms a head-to-head dimer to function as a transmembrane channel for monovalent cations (H+, Na+, and K+). The potent anticancer activity of 1 was believed to be mainly attributed to the free ion diffusion across the plasma membrane. In this study, we investigated the cytostatic action of 1 in nanomolar concentrations using the human breast cancer cell line MCF-7, and revealed the unprecedented spatiotemporal behavior of 1 for the first time. Compound 1 not only disrupted the ion concentration gradients of the plasma membrane, but also localized in the mitochondria and depolarized the inner mitochondrial membrane. The diminished H+ gradient in the mitochondria inhibited ATP synthesis. The resultant mitochondrial malfunction led to mitophagy, while the cellular energy depletion induced G1 phase accumulation. The multiple events occurred in a time-dependent fashion and ultimately caused potent inhibition of cell growth. The present study provides valuable information for the design and development of new cytostatic agents exploiting channel-forming natural products.

DOI: https://doi.org/10.1039/d2sc02024f
Nat Commun. 2022 Jul 27. 13(1): 4339

Structures of Atm1 provide insight into [2Fe-2S] cluster export from mitochondria.

Ping Li, Amber L Hendricks, Yong Wang, Rhiza Lyne E Villones, Karin Lindkvist-Petersson, Gabriele Meloni, J A Cowan, Kaituo Wang, Pontus Gourdon.

In eukaryotes, iron-sulfur clusters are essential cofactors for numerous physiological processes, but these clusters are primarily biosynthesized in mitochondria. Previous studies suggest mitochondrial ABCB7-type exporters are involved in maturation of cytosolic iron-sulfur proteins. However, the molecular mechanism for how the ABCB7-type exporters participate in this process remains elusive. Here, we report a series of cryo-electron microscopy structures of a eukaryotic homolog of human ABCB7, CtAtm1, determined at average resolutions ranging from 2.8 to 3.2 Å, complemented by functional characterization and molecular docking in silico. We propose that CtAtm1 accepts delivery from glutathione-complexed iron-sulfur clusters. A partially occluded state links cargo-binding to residues at the mitochondrial matrix interface that line a positively charged cavity, while the binding region becomes internalized and is partially divided in an early occluded state. Collectively, our findings substantially increase the understanding of the transport mechanism of eukaryotic ABCB7-type proteins.

DOI: https://doi.org/10.1038/s41467-022-32006-8
Carcinogenesis. 2022 Jul 28. pii: bgac061. [Epub ahead of print]

SLC38A6, regulated by EP300-mediated modifications of H3K27ac, promotes cell proliferation, glutamine metabolism, and mitochondrial respiration in hepatocellular carcinoma.

Li Huang, Lixing Li, Bin Cheng, Tonghai Xing.

  Hepatocellular carcinoma (HCC) is a common form of liver cancer. The incidence of HCC is increasing and effective prevention methods are needed. The solute carrier family 38 member 6 (SLC38A6) plays an important role in the metabolism of glutamine, which is a central nutrient for many cancers. However, the regulation and function of SLC38A6 in HCC are unclear. SLC38A6 levels in human HCC tissue arrays and cells were determined. SLC38A6 was silenced or overexpressed to determine its role in regulating cell viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration. A luminescence assay was used to study the interaction between SLC38A6 and EP300. The interactions between SLC38A6, H3K27ac, and EP300 were determined using chromatin immunoprecipitation assays. Quantitative RT-PCR and immunoblots were performed to measure mRNAs and proteins, respectively. SLC38A6 expression was higher in HCC compared with expression in normal tissue. Silencing SLC38A6 inhibited cell viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration, while SLC38A6 overexpression had the opposite effects. Silencing SLC38A6 also inhibited tumor growth in vivo. Silencing EP300 significantly suppressed the interaction between H3K27ac and the SLC38A6 promoter, leading to decreased SLC38A6. SLC38A6 is regulated by EP300-mediated modifications of H3K27ac and promotes viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration in HCC cells.

Keywords:  acetylation; glutamine metabolism; hepatocellular carcinoma; solute carrier family 38 member 6

DOI:  https://doi.org/10.1093/carcin/bgac061
Nat Chem Biol. 2022 Jul 25.

O-GlcNAcylation promotes pancreatic tumor growth by regulating malate dehydrogenase 1.

Qiang Zhu, Hong Zhou, Liming Wu, Zhenyuan Lai, Didi Geng, Weiwei Yang, Jie Zhang, Zhiya Fan, Weijie Qin, Yong Wang, Ruhong Zhou, Wen Yi.

Oncogenic Kras-activated pancreatic ductal adenocarcinoma (PDAC) cells highly rely on an unconventional glutamine catabolic pathway to sustain cell growth. However, little is known about how this pathway is regulated. Here we demonstrate that Kras mutation induces cellular O-linked β-N-acetylglucosamine (O-GlcNAc), a prevalent form of protein glycosylation. Malate dehydrogenase 1 (MDH1), a key enzyme in the glutamine catabolic pathway, is positively regulated by O-GlcNAcylation on serine 189 (S189). Molecular dynamics simulations suggest that S189 glycosylation on monomeric MDH1 enhances the stability of the substrate-binding pocket and strengthens the substrate interactions by serving as a molecular glue. Depletion of O-GlcNAcylation reduces MDH1 activity, impairs glutamine metabolism, sensitizes PDAC cells to oxidative stress, decreases cell proliferation and inhibits tumor growth in nude mice. Furthermore, O-GlcNAcylation levels of MDH1 are elevated in clinical PDAC samples. Our study reveals that O-GlcNAcylation contributes to pancreatic cancer growth by regulating the metabolic activity of MDH1.

DOI: https://doi.org/10.1038/s41589-022-01085-5
Cancer Discov. 2022 Jul 27. pii: CD-22-0661. [Epub ahead of print]

A cancer cell-intrinsic GOT2-PPARd axis suppresses antitumor immunity.

Jaime Abrego, Hannah Sanford-Crane, Chet Oon, Xu Xiao, Courtney B Betts, Duanchen Sun, Shanthi Nagarajan, Luis Diaz, Holly Sandborg, Sohinee Bhattacharyya, Zheng Xia, Lisa M Coussens, Peter Tontonoz, Mara H Sherman.

Despite significant recent advances in precision medicine, pancreatic ductal adenocarcinoma (PDAC) remains near-uniformly lethal. While immune-modulatory therapies hold promise to meaningfully improve outcomes for PDAC patients, development of such therapies requires an improved understanding of the immune evasion mechanisms that characterize the PDAC microenvironment. Here we show that cancer cell-intrinsic glutamic-oxaloacetic transaminase 2 (GOT2) shapes the immune microenvironment to suppress antitumor immunity. Mechanistically, we find that GOT2 functions beyond its established role in the malate-aspartate shuttle and promotes the transcriptional activity of nuclear receptor peroxisome proliferator-activated receptor delta (PPARd), facilitated by direct fatty acid binding. While GOT2 is dispensable for cancer cell proliferation in vivo, the GOT2-PPARd axis promotes spatial restriction of both CD4+ and CD8+ T cells from the tumor microenvironment. Our results demonstrate a non-canonical function for an established mitochondrial enzyme in transcriptional regulation of immune evasion, which may be exploitable to promote a productive antitumor immune response.

DOI: https://doi.org/10.1158/2159-8290.CD-22-0661
Immunology. 2022 Jul 28.

Oxidative Phosphorylation Regulates Interleukin-10 Production in Regulatory B Cells via the Extracellular Signal-related Kinase Pathway.

Yinhong Zhu, Xiaoran Zhang, Shujuan Xie, Weijia Bao, Jingrou Chen, Qili Wu, Xiaorong Lai, Longshan Liu, Shiqiu Xiong, Yanwen Peng.

  Regulatory B cells (Bregs) are immune cells that constrain autoimmune response and restrict inflammation via their expression of interleukin (IL)-10. However, the molecular mechanisms underlying Breg differentiation and IL-10 secretion remain unclear. Previous data suggest that cellular metabolism determines both the fate and function of these cells. Here, we suggest an essential role for mitochondrial oxidative phosphorylation (OXPHOS) in the regulation of IL-10 in these Bregs. We found that IL-10+ B cells from IL-10-green fluorescent protein-expressing mice had higher oxygen consumption rate than IL-10- B cells. In addition, inhibition of OXPHOS decreased the expression of IL-10 in B cells. Further, suppression of OXPHOS diminished the expression of surface markers for Bregs and impaired their therapeutic effects in dextran sulfate sodium (DSS)-induced colitis. Mechanistically, mitochondrial OXPHOS was found to regulate the transcription factor HIF-1α through the extracellular signal-related kinase pathway. Taken together, this study reveals a strong correlation between mitochondrial OXPHOS and Breg phenotype/function, indicating OXPHOS as a therapeutic target in autoimmune diseases driven by Breg dysfunction.

Keywords:  Hypoxia-inducible factor-1α (HIF-1α); extracellular signal-related kinase (ERK) signaling pathway; interleukin (IL)-10; oxidative phosphorylation (OXPHOS); regulatory B cells

DOI:  https://doi.org/10.1111/imm.13554
Molecules. 2022 Jul 15. pii: 4533. [Epub ahead of print]27(14):

Quantitative Proteome Analysis Reveals Melissa officinalis Extract Targets Mitochondrial Respiration in Colon Cancer Cells.

Tzu-Ting Kuo, Li-Chun Lin, Hsin-Yi Chang, Pei-Jung Chiang, Hsin-Yi Wu, Tai-Yuan Chen, Shih-Min Hsia, Tsui-Chin Huang.

  Melissa officinalis (MO), known as lemon balm, is a popular ingredient blended in herbal tea. In recent decades, the bioactivities of MO have been studied in sub-health and pathological status, highlighting MO possesses multiple pharmacological effects. We previously showed that hot water MO extract exhibited anticancer activity in colorectal cancer (CRC). However, the detailed mechanisms underlying MO-induced cell death remain elusive. To elucidate the anticancer regulation of MO extract in colon cancer, a data-driven analysis by proteomics approaches and bioinformatics analysis was applied. An isobaric tandem mass tags-based quantitative proteome analysis using liquid chromatography-coupled tandem mass spectrometry was performed to acquire proteome-wide expression data. The over-representation analysis and functional class scoring method were implemented to interpret the MO-induced biological regulations. In total, 3465 quantifiable proteoforms were identified from 24,348 peptides, with 67 upregulated and 54 downregulated proteins in the MO-treated group. Mechanistically, MO impeded mitochondrial respiratory electron transport by triggering a reactive oxygen species (ROS)-mediated oxidative stress response. MO hindered the mitochondrial membrane potential by reducing the protein expression in the electron transport chain, specifically the complex I and II, which could be restored by ROS scavenger. The findings comprehensively elucidate how MO hot water extract activates antitumor effects in colorectal cancer (CRC) cells.

Keywords:  Melissa officinalis; colorectal cancer; mitochondrial respiratory chain complex; proteomics analysis; reactive oxygen species

DOI:  https://doi.org/10.3390/molecules27144533
Cell Death Dis. 2022 Jul 28. 13(7): 660

The hexokinase "HKDC1" interaction with the mitochondria is essential for liver cancer progression.

Md Wasim Khan, Alexander R Terry, Medha Priyadarshini, Vladimir Ilievski, Zeenat Farooq, Grace Guzman, Jose Cordoba-Chacon, Issam Ben-Sahra, Barton Wicksteed, Brian T Layden.

Liver cancer (LC) is the fourth leading cause of death from cancer malignancies. Recently, a putative fifth hexokinase, hexokinase domain containing 1 (HKDC1), was shown to have significant overexpression in LC compared to healthy liver tissue. Using a combination of in vitro and in vivo tools, we examined the role of HKDC1 in LC development and progression. Importantly, HKDC1 ablation stops LC development and progression via its action at the mitochondria by promoting metabolic reprogramming and a shift of glucose flux away from the TCA cycle. HKDC1 ablation leads to mitochondrial dysfunction resulting in less cellular energy, which cannot be compensated by enhanced glucose uptake. Moreover, we show that the interaction of HKDC1 with the mitochondria is essential for its role in LC progression, and without this interaction, mitochondrial dysfunction occurs. As HKDC1 is highly expressed in LC cells, but only to a minimal degree in hepatocytes under normal conditions, targeting HKDC1, specifically its interaction with the mitochondria, may represent a highly selective approach to target cancer cells in LC.

DOI: https://doi.org/10.1038/s41419-022-04999-z
Nat Commun. 2022 Jul 26. 13(1): 4327

Targeting de novo lipogenesis and the Lands cycle induces ferroptosis in KRAS-mutant lung cancer.

Caterina Bartolacci, Cristina Andreani, Gonçalo Vale, Stefano Berto, Margherita Melegari, Anna Colleen Crouch, Dodge L Baluya, George Kemble, Kurt Hodges, Jacqueline Starrett, Katerina Politi, Sandra L Starnes, Daniele Lorenzini, Maria Gabriela Raso, Luisa M Solis Soto, Carmen Behrens, Humam Kadara, Boning Gao, Ignacio I Wistuba, John D Minna, Jeffrey G McDonald, Pier Paolo Scaglioni.

Mutant KRAS (KM), the most common oncogene in lung cancer (LC), regulates fatty acid (FA) metabolism. However, the role of FA in LC tumorigenesis is still not sufficiently characterized. Here, we show that KMLC has a specific lipid profile, with high triacylglycerides and phosphatidylcholines (PC). We demonstrate that FASN, the rate-limiting enzyme in FA synthesis, while being dispensable in EGFR-mutant or wild-type KRAS LC, is required for the viability of KMLC cells. Integrating lipidomic, transcriptomic and functional analyses, we demonstrate that FASN provides saturated and monounsaturated FA to the Lands cycle, the process remodeling oxidized phospholipids, such as PC. Accordingly, blocking either FASN or the Lands cycle in KMLC, promotes ferroptosis, a reactive oxygen species (ROS)- and iron-dependent cell death, characterized by the intracellular accumulation of oxidation-prone PC. Our work indicates that KM dictates a dependency on newly synthesized FA to escape ferroptosis, establishing a targetable vulnerability in KMLC.

DOI: https://doi.org/10.1038/s41467-022-31963-4
Nature. 2022 Jul 27.

Akt protein boosts cancer metabolism through a two-pronged attack.

Philipp Poeller, Almut Schulze.



Keywords:  Biochemistry; Cancer; Metabolism

DOI:  https://doi.org/10.1038/d41586-022-01603-4
Autophagy. 2022 Jul 28.

Autophagic secretion of mitochondria (ASM): An alternative way for getting rid of damaged mitochondria.

Hayden Weng Siong Tan, Guang Lu, Han-Ming Shen.

  PINK1-PRKN/Parkin-mediated mitophagy represents an important mitochondrial quality control (MQC) pathway that clears damaged/dysfunctional mitochondria. Although the conjugation of mammalian Atg8-family proteins (mATG8s) to phosphatidylethanolamine (PE) is a defining step in autophagy, its role in mitophagy remains unclear. In our recent study, we found that the mATG8 conjugation system is not required for PINK1-PRKN-mediated mitochondria clearance. Instead, mATG8 conjugation system-independent mitochondria clearance relies on secretory autophagy, in a process we term as the autophagic secretion of mitochondria (ASM). As ASM results in the spurious activation of the CGAS-STING1 pathway, we propose that defects in mATG8 lipidation may promote inflammation through ASM.

Keywords:  Extracellular vesicles; PINK1-PRKN; inflammation; mATG8 conjugation system; mitochondrial quality control; mitophagy; secretory autophagy

DOI:  https://doi.org/10.1080/15548627.2022.2107310
Cancer Res. 2022 Jul 27. pii: CAN-22-0042. [Epub ahead of print]

GOT2 Silencing Promotes Reprogramming of Glutamine Metabolism and Sensitizes Hepatocellular Carcinoma to Glutaminase Inhibitors.

Yunzheng Li, Binghua Li, Yanchao Xu, Liyuan Qian, Tiancheng Xu, Gang Meng, Huan Li, Ye Wang, Laizhu Zhang, Xiang Jiang, Qi Liu, Yuanyuan Xie, Chunxiao Cheng, Beicheng Sun, Decai Yu.

Hepatocellular carcinoma (HCC) is one of the primary liver malignancies with a poor prognosis. Glutamic-oxaloacetic transaminase 2 (GOT2) is a highly tissue-specific gene in the liver, but the roles GOT2 plays in the progression of HCC remain unclear. Here, we report that GOT2 is downregulated in HCC tumor tissues and that low expression of GOT2 is associated with advanced progression and poor prognosis. In HCC cells, knockdown of GOT2 promoted proliferation, migration, and invasion. In mouse models of HCC, loss of GOT2 promoted tumor growth as well as hematogenous and intrahepatic metastasis. Mechanistically, silencing of GOT2 enhanced glutaminolysis, nucleotide synthesis, and GSH synthesis by reprogramming glutamine metabolism to support the cellular antioxidant system, which activated the PI3K/AKT/mTOR pathway to contribute to HCC progression. Furthermore, HCC with low expression of GOT2 was highly dependent on glutamine metabolism and sensitive to the glutaminase inhibitor CB-839 in vitro and in vivo. Overall, GOT2 is involved in glutamine metabolic reprogramming to promote HCC progression and may serve as a therapeutic and diagnostic target for HCC.

DOI: https://doi.org/10.1158/0008-5472.CAN-22-0042
Mol Syst Biol. 2022 Aug;18(8): e10874

Metabolic balance in colorectal cancer is maintained by optimal Wnt signaling levels.

Katharina Imkeller, Giulia Ambrosi, Nancy Klemm, Ainara Claveras Cabezudo, Luisa Henkel, Wolfgang Huber, Michael Boutros.

  Wnt pathways are important for the modulation of tissue homeostasis, and their deregulation is linked to cancer development. Canonical Wnt signaling is hyperactivated in many human colorectal cancers due to genetic alterations of the negative Wnt regulator APC. However, the expression levels of Wnt-dependent targets vary between tumors, and the mechanisms of carcinogenesis concomitant with this Wnt signaling dosage have not been understood. In this study, we integrate whole-genome CRISPR/Cas9 screens with large-scale multi-omic data to delineate functional subtypes of cancer. We engineer APC loss-of-function mutations and thereby hyperactivate Wnt signaling in cells with low endogenous Wnt activity and find that the resulting engineered cells have an unfavorable metabolic equilibrium compared with cells which naturally acquired Wnt hyperactivation. We show that the dosage level of oncogenic Wnt hyperactivation impacts the metabolic equilibrium and the mitochondrial phenotype of a given cell type in a context-dependent manner. These findings illustrate the impact of context-dependent genetic interactions on cellular phenotypes of a central cancer driver mutation and expand our understanding of quantitative modulation of oncogenic signaling in tumorigenesis.

Keywords:  APC; functional genomics; multi-omic data integration; quantitative signaling; synthetic lethality

DOI:  https://doi.org/10.15252/msb.202110874
Blood. 2022 Jul 26. pii: blood.2022016112. [Epub ahead of print]

Loss of sphingosine kinase 2 promotes the expansion of hematopoietic stem cells by improving their metabolic fitness.

Changzheng Li, Binghuo Wu, Yishan Li, Yaxi Liu, Jin Wang, Jiayi Xie, Xi Xu, Xiaobin Tian, Zhitao Ye, Jingjing Guan, Jie Chen, Siyu Xie, Baolin Zhang, Boyong Cai, Qianhao Wang, Haopeng Yu, Tian Lan, Cheuk Him Man, Xunlei Kang, Pengxu Qian, John M Perry, Aibin He, Linjia Jiang, Meng Zhao.

Hematopoietic stem cells (HSCs) have reduced capacities to properly maintain and replenish the hematopoietic system during myelosuppressive injury or aging. Expanding and rejuvenating HSCs for therapeutic purposes has been a long-sought goal, with limited progress. Here, we show that enzyme sphingosine kinase 2 (Sphk2), which generates the lipid metabolite sphingosine-1-phosphate, is highly expressed in HSCs. The deletion of Sphk2 markedly promotes self-renewal and increases the regenerative potential of HSCs. More importantly, Sphk2 deletion globally preserves the young HSC gene expression pattern, improves the function, and sustains the multilineage potential of HSCs during aging. Mechanistically, Sphk2 interacts with prolyl hydroxylase 2 and the Von Hippel-Lindau protein to facilitate HIF1α ubiquitination in the nucleus independent of the Sphk2 catalytic activity. Deletion of Sphk2 increases hypoxic responses by stabilizing the HIF1α protein to upregulate PDK3, a glycolysis checkpoint protein for HSC quiescence, which subsequently enhances the function of HSCs by improving their metabolic fitness; specifically, it enhances anaerobic glycolysis but suppresses mitochondrial oxidative phosphorylation and generation of reactive oxygen species. Overall, targeting Sphk2 to enhance the metabolic fitness of HSCs is a promising strategy to expand and rejuvenate functional HSCs.

DOI: https://doi.org/10.1182/blood.2022016112
Cell Death Dis. 2022 Jul 27. 13(7): 651

Lactate promotes metastasis of normoxic colorectal cancer stem cells through PGC-1α-mediated oxidative phosphorylation.

Shuang Liu, Hui Zhao, Yibing Hu, Chang Yan, Yulong Mi, Xiaolan Li, Deding Tao, Jichao Qin.

Uneven oxygen supply in solid tumors leads to hypoxic and normoxic regions. Hypoxic cells exhibit increased secretion of lactate, which creates an acidic tumor microenvironment (TME). This acidic TME is positively associated with tumor metastasis. Despite the increased metastatic capacity of hypoxic cells, they are located relatively further away from the blood vessels and have limited access to the circulatory system. Studies have shown that cancer stem cells (CSCs) are enriched for tumor metastasis-initiating cells and generally undergo aerobic respiration, which could be enhanced by lactate. We therefore hypothesized that TME-derived lactate may promote the metastasis of normoxic CSCs. In the present study, the abundance of hypoxic and normoxic CSCs was analyzed in primary CRC tumors. It was found that the proportion of normoxic CSCs was positively associated with tumor stage. Using two human CRC cell lines, LoVo and SW480, and a patient-derived xenograft (XhCRC), it was found that treatment with lactate promoted normoxic CSC metastasis. Metabolism analysis indicated that, upon treatment with lactate, oxidative phosphorylation (OXPHOS) activity in normoxic CSCs was enhanced, whereas hypoxic CSCs were rarely altered. At the molecular level, the expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a master regulator of lactate oxidation, was found to be elevated in normoxic CSCs. Furthermore, PGC-1α knockdown markedly reduced the metastatic potential of normoxic CSCs. Notably, both the PGC-1α-mediated OXPHOS activity and metastatic potential were impaired when hypoxia-inducible factor-1α (HIF-1α) was activated in normoxic CSCs. Together, these findings provide a therapeutic strategy against tumor metastasis through the targeting of PGC-1α and, thus, the suppression of lactate-feeding OXPHOS in normoxic CSCs may improve the therapeutic benefit of patients with cancer, particularly CRC.

DOI: https://doi.org/10.1038/s41419-022-05111-1
Molecules. 2022 Jul 07. pii: 4350. [Epub ahead of print]27(14):

Melatonin Reverses the Warburg-Type Metabolism and Reduces Mitochondrial Membrane Potential of Ovarian Cancer Cells Independent of MT1 Receptor Activation.

Maira Smaniotto Cucielo, Roberta Carvalho Cesário, Henrique Spaulonci Silveira, Letícia Barbosa Gaiotte, Sérgio Alexandre Alcantara Dos Santos, Debora Aparecida Pires de Campos Zuccari, Fábio Rodrigues Ferreira Seiva, Russel J Reiter, Luiz Gustavo de Almeida Chuffa.

  Ovarian cancer (OC) is the most lethal gynecologic malignancy, and melatonin has shown various antitumor properties. Herein, we investigated the influence of melatonin therapy on energy metabolism and mitochondrial integrity in SKOV-3 cells and tested whether its effects depended on MT1 receptor activation. SKOV-3 cells were exposed to different melatonin concentrations, and experimental groups were divided as to the presence of MT1 receptors (melatonin groups) or receptor absence by RNAi silencing (siRNA MT1+melatonin). Intracellular melatonin levels increased after treatment with melatonin independent of the MT1. The mitochondrial membrane potential of SKOV-3 cells decreased in the group treated with the highest melatonin concentration. Melatonin reduced cellular glucose consumption, while MT1 knockdown increased its consumption. Interconversion of lactate to pyruvate increased after treatment with melatonin and was remarkable in siRNA MT1 groups. Moreover, lactate dehydrogenase activity decreased with melatonin and increased after MT1 silencing at all concentrations. The UCSC XenaBrowser tool showed a positive correlation between the human ASMTL gene and the ATP synthase genes, succinate dehydrogenase gene (SDHD), and pyruvate dehydrogenase genes (PDHA and PDHB). We conclude that melatonin changes the glycolytic phenotype and mitochondrial integrity of SKOV-3 cells independent of the MT1 receptor, thus decreasing the survival advantage of OC cells.

Keywords:  SKOV-3 cells; Warburg effect; glucose; melatonin; mitochondrial metabolism; ovarian cancer

DOI:  https://doi.org/10.3390/molecules27144350
Cancers (Basel). 2022 Jul 15. pii: 3456. [Epub ahead of print]14(14):

Targeting Acute Myeloid Leukemia with Venetoclax; Biomarkers for Sensitivity and Rationale for Venetoclax-Based Combination Therapies.

Mila S Griffioen, David C de Leeuw, Jeroen J W M Janssen, Linda Smit.

  Venetoclax is a BCL-2 inhibitor that effectively improves clinical outcomes in newly diagnosed, relapsed and refractory acute myeloid leukemia (AML) patients, with complete response rates (with and without complete blood count recovery) ranging between 34-90% and 21-33%, respectively. Here, we aim to give an overview of the efficacy of venetoclax-based therapy for AML patients, as compared to standard chemotherapy, and on factors and mechanisms involved in venetoclax sensitivity and resistance in AML (stem) cells, with the aim to obtain a perspective of response biomarkers and combination therapies that could enhance the sensitivity of AML cells to venetoclax. The presence of molecular aberrancies can predict responses to venetoclax, with a higher response in NPM1-, IDH1/2-, TET2- and relapsed or refractory RUNX1-mutated AML. Decreased sensitivity to venetoclax was observed in patients harboring FLT3-ITD, TP53, K/NRAS or PTPN11 mutations. Moreover, resistance to venetoclax was observed in AML with a monocytic phenotype and patients pre-treated with hypomethylating agents. Resistance to venetoclax can arise due to mutations in BCL-2 or pro-apoptotic proteins, an increased dependency on MCL-1, and usage of additional/alternative sources for energy metabolism, such as glycolysis and fatty acid metabolism. Clinical studies are testing combination therapies that may circumvent resistance, including venetoclax combined with FLT3- and MCL-1 inhibitors, to enhance venetoclax-induced cell death. Other treatments that can potentially synergize with venetoclax, including MEK1/2 and mitochondrial complex inhibitors, need to be evaluated in a clinical setting.

Keywords:  AML; biomarkers; resistance; sensitivity; therapeutic combinations; venetoclax (BCL-2 inhibitor)

DOI:  https://doi.org/10.3390/cancers14143456
Commun Biol. 2022 Jul 25. 5(1): 745

Mitochondrial surface coating with artificial lipid membrane improves the transfer efficacy.

Takafumi Nakano, Yoshihiko Nakamura, Ji-Hyun Park, Masayoshi Tanaka, Kazuhide Hayakawa.

Extracellular mitochondria are present and act as non-cell-autonomous signals to support energetic homeostasis. While mitochondria allograft is a promising approach in rescuing neurons, glia, and vascular cells in CNS injury and disease, there are profound limitations in cellular uptake of mitochondria together with the efficacy. Here, we modified mitochondria by coating them with cationic DOTAP mixed with DOPE via a modified inverted emulsion method to improve mitochondrial transfer and efficacy. We initially optimized the method using control microbeads and liposomes followed by using mitochondria isolated from intact cerebral cortex of male adult C57BL/6J mice. After the coating process, FACS analysis indicated that approximately 86% of mitochondria were covered by DOTAP/DOPE membrane. Moreover, the artificial membrane-coated mitochondria (AM-mito) shifted the zeta-potential toward positive surface charge, confirming successful coating of isolated mitochondria. Mitochondrial proteins (TOM40, ATP5a, ACADM, HSP60, COX IV) and membrane potentials were well maintained in AM-mito. Importantly, the coating improved mitochondrial internalization and neuroprotection in cultured neurons. Furthermore, intravenous infusion of AM-mito immediately after focal cerebral ischemia-reperfusion amplified cerebroprotection in vivo. Collectively, these findings indicate that mitochondrial surface coating with artificial lipid membrane is feasible and may improve the therapeutic efficacy of mitochondria allograft.

DOI: https://doi.org/10.1038/s42003-022-03719-9