bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2022‒08‒28
39 papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Mol Cancer Res. 2022 Aug 22. pii: MCR-21-1032. [Epub ahead of print]
      Acute myeloid leukemia (AML) is a hematological malignancy metabolically dependent on oxidative phosphorylation and mitochondrial electron transport chain (ETC) activity. AML cells are distinct from their normal hematopoietic counterparts by this metabolic reprogramming, which presents targets for new selective therapies. Here, metabolic changes in AML cells after ETC impairment are investigated. Genetic knockdown of the ETC complex II (CII) chaperone protein SDHAF1 (succinate dehydrogenase assembly factor 1) suppressed CII activity and delayed AML cell growth in vitro and in vivo. As a result, a novel small molecule that directly binds to the ubiquinone binding site of CII and inhibits its activity was identified. Pharmacological inhibition of CII induced selective cell death in AML cells while sparing normal hematopoietic progenitors. Through stable isotope tracing, results show that genetic or pharmacological inhibition of CII truncates the tricarboxylic acid cycle (TCA) and leads to anaplerotic glutamine metabolism to reestablish the truncated cycle. The inhibition of CII showed divergent fates of AML cells since they lacked the metabolic plasticity to adequately utilize glutamine metabolism, resulting in preferential depletion of key metabolites in the TCA cycle and death; normal cells were unaffected. These findings provide insight into the metabolic mechanisms that underlie AML's selective inhibition of CII. Implications: This work highlights the effects of direct CII inhibition in mediating selective AML cell death and provides insights into glutamine anaplerosis as a metabolic adaptation that can be therapeutically targeted.
  2. Redox Biol. 2022 Aug 13. pii: S2213-2317(22)00203-8. [Epub ahead of print]56 102431
      YAP1 and TAZ are transcriptional co-activator proteins that play fundamental roles in many biological processes, from cell proliferation and cell lineage fate determination to tumorigenesis. We previously demonstrated that Limb Expression 1 (LIX1) regulates YAP1 and TAZ activity and controls digestive mesenchymal progenitor proliferation. However, LIX1 mode of action remains elusive. Here, we found that endogenous LIX1 is localized in mitochondria and is anchored to the outer mitochondrial membrane through S-palmitoylation of cysteine 84, a residue conserved in all LIX1 orthologs. LIX1 downregulation altered the mitochondrial ultrastructure, resulting in a significantly decreased respiration and attenuated production of mitochondrial reactive oxygen species (mtROS). Mechanistically, LIX1 knock-down impaired the stability of the mitochondrial proteins PHB2 and OPA1 that are found in complexes with mitochondrial-specific phospholipids and are required for cristae organization. Supplementation with unsaturated fatty acids counteracted the effects of LIX1 knock-down on mitochondrial morphology and ultrastructure and restored YAP1/TAZ signaling. Collectively, our data demonstrate that LIX1 is a key regulator of cristae organization, modulating mtROS level and subsequently regulating the signaling cascades that control fate commitment of digestive mesenchyme-derived cells.
    Keywords:  Cell fate; Cristae; Linoleic acid; Mitochondria; Sarcoma; Smooth muscle; YAP1/TAZ; mtROS
  3. Cell Stem Cell. 2022 Aug 19. pii: S1934-5909(22)00304-6. [Epub ahead of print]
      Skeletal muscle regeneration depends on the correct expansion of resident quiescent stem cells (satellite cells), a process that becomes less efficient with aging. Here, we show that mitochondrial dynamics are essential for the successful regenerative capacity of satellite cells. The loss of mitochondrial fission in satellite cells-due to aging or genetic impairment-deregulates the mitochondrial electron transport chain (ETC), leading to inefficient oxidative phosphorylation (OXPHOS) metabolism and mitophagy and increased oxidative stress. This state results in muscle regenerative failure, which is caused by the reduced proliferation and functional loss of satellite cells. Regenerative functions can be restored in fission-impaired or aged satellite cells by the re-establishment of mitochondrial dynamics (by activating fission or preventing fusion), OXPHOS, or mitophagy. Thus, mitochondrial shape and physical networking controls stem cell regenerative functions by regulating metabolism and proteostasis. As mitochondrial fission occurs less frequently in the satellite cells in older humans, our findings have implications for regeneration therapies in sarcopenia.
    Keywords:  Drp1; OXPHOS; aging; metabolism; mitochondria; mitochondrial dynamics; mitophagy; muscle regeneration; muscle stem cells; satellite cells
  4. Front Immunol. 2022 ;13 918241
      Activated effector T cells (Teff) and/or compromised regulatory T cells (Treg) underlie many chronic inflammatory diseases. We discovered a novel pathway to regulate survival and expansion of Teff without compromising Treg survival and a potential therapeutic to treat these diseases. We found dimethylguanidino valeric acid (DMGV) as a rheostat for Teff survival: while cell-intrinsic DMGV generated by Alanine-Glyoxylate Aminotransferase 2 (AGXT2) is essential for survival and expansion by inducing mitochondrial ROS and regulation of glycolysis, an excessive (or exogenous) DMGV level inhibits activated Teff survival, thereby the AGXT2-DMGV-ROS axis functioning as a switch to turn on and off Teff expansion. DMGV-induced ROS is essential for glycolysis in Teff, and paradoxically DMGV induces ROS only when glycolysis is active. Mechanistically, DMGV rapidly activates mitochondrial calcium uniporter (MCU), causing a surge in mitochondrial Ca2+ without provoking calcium influx to the cytosol. The mitochondrial Ca2+ surge in turn triggers the mitochondrial Na+/Ca2+ exchanger (NCLX) and the subsequent mitochondrial Na+ import induces ROS by uncoupling the Coenzyme Q cycle in Complex III of the electron transport chain. In preclinical studies, DMGV administration significantly diminished the number of inflammatory T cells, effectively suppressing chronic inflammation in mouse models of colitis and rheumatoid arthritis. DMGV also suppressed expansion of cancer cells in vitro and in a mouse T cell leukemic model by the same mechanism. Our data provide a new pathway regulating T cell survival and a novel mode to treat autoimmune diseases and cancers.
    Keywords:  ADMA; AGXT2; DMGV; MCU; NLCX ; SDMA
  5. Antioxidants (Basel). 2022 Jul 29. pii: 1487. [Epub ahead of print]11(8):
      α-ketoglutarate dehydrogenase complex (KGDHc), or 2-oxoglutarate dehydrogenase complex (OGDHc) is a rate-limiting enzyme in the tricarboxylic acid cycle, that has been identified in neurodegenerative diseases such as in Alzheimer's disease. The aim of the present study was to establish the role of the KGDHc and its subunits in the bioenergetics and reactive oxygen species (ROS) homeostasis of brain mitochondria. To study the bioenergetic profile of KGDHc, genetically modified mouse strains were used having a heterozygous knock out (KO) either in the dihydrolipoyl succinyltransferase (DLST+/-) or in the dihydrolipoyl dehydrogenase (DLD+/-) subunit. Mitochondrial oxygen consumption, hydrogen peroxide (H2O2) production, and expression of antioxidant enzymes were measured in isolated mouse brain mitochondria. Here, we demonstrate that the ADP-stimulated respiration of mitochondria was partially arrested in the transgenic animals when utilizing α-ketoglutarate (α-KG or 2-OG) as a fuel substrate. Succinate and α-glycerophosphate (α-GP), however, did not show this effect. The H2O2 production in mitochondria energized with α-KG was decreased after inhibiting the adenine nucleotide translocase and Complex I (CI) in the transgenic strains compared to the controls. Similarly, the reverse electron transfer (RET)-evoked H2O2 formation supported by succinate or α-GP were inhibited in mitochondria isolated from the transgenic animals. The decrease of RET-evoked ROS production by DLST+/- or DLD+/- KO-s puts the emphasis of the KGDHc in the pathomechanism of ischemia-reperfusion evoked oxidative stress. Supporting this notion, expression of the antioxidant enzyme glutathione peroxidase was also decreased in the KGDHc transgenic animals suggesting the attenuation of ROS-producing characteristics of KGDHc. These findings confirm the contribution of the KGDHc to the mitochondrial ROS production and in the pathomechanism of ischemia-reperfusion injury.
    Keywords:  DLD; DLST; KGDHc; OGDHc; RET; ROS; antioxidant systems; cellular respiration; ischemia-reperfusion; mitochondria; oxoglutarate dehydrogenase complex; reactive oxygen species; reverse electron transfer; succinate; transgenic animal; α-glycerophosphate; α-ketoglutarate dehydrogenase complex
  6. Biology (Basel). 2022 Jul 28. pii: 1132. [Epub ahead of print]11(8):
      Several intermediate metabolites harbour cell-signalling properties, thus, it is likely that specific metabolites enable the communication between neighbouring cells, as well as between host cells with the microbiota, pathogens, and tumour cells. Mitochondria, a source of intermediate metabolites, participate in a wide array of biological processes beyond that of ATP production, such as intracellular calcium homeostasis, cell signalling, apoptosis, regulation of immune responses, and host cell-microbiota crosstalk. In this regard, mitochondria's plasticity allows them to adapt their bioenergetics status to intra- and extra-cellular cues, and the mechanisms driving such plasticity are currently a matter of intensive research. Here, we addressed whether mitochondrial ultrastructure and activity are differentially shaped when human monocytes are exposed to an exogenous source of lactate (derived from glycolysis), succinate, and fumarate (Krebs cycle metabolic intermediates), or butyrate and acetate (short-chain fatty acids produced by intestinal microbiota). It has previously been shown that fumarate induces mitochondrial fusion, increases the mitochondrial membrane potential (Δψm), and reshapes the mitochondrial cristae ultrastructure. Here, we provide evidence that, in contrast to fumarate, lactate, succinate, and butyrate induce mitochondrial fission, while acetate induces mitochondrial swelling. These traits, along with mitochondrial calcium influx kinetics and glycolytic vs. mitochondrial ATP-production rates, suggest that these metabolites differentially shape mitochondrial function, paving the way for the understanding of metabolite-induced metabolic reprogramming of monocytes and its possible use for immune-response intervention.
    Keywords:  Krebs cycle; glycolysis; innate immunity; mitochondria; mitochondrial reprogramming; short-chain fatty acids
  7. Ann Biomed Eng. 2022 Aug 24.
      Mitochondria, mainly known as energy factories of eukaryotic cells, also exert several additional signaling and metabolic functions and are today recognized as major cellular biosynthetic and signaling hubs. Mitochondria possess their own genome (mitochondrial DNA-mtDNA), that encodes proteins essential for oxidative phosphorylation, and mutations in it are an important contributor to human disease. The mtDNA mutations often exist in heteroplasmic conditions, with both healthy and mutant versions of the mtDNA residing in patients' cells and the level of mutant mtDNA may vary between different tissues and organs and affect the clinical outcome of the disease. Thus, shifting the ratio between healthy and mutant mtDNA in patients' cells provides an intriguing therapeutic option for mtDNA diseases. In this review we describe current strategies for modulating mitochondrial heteroplasmy levels with engineered endonucleases including mitochondrially targeted TALENs and Zinc finger nucleases (ZFNs) and discuss their therapeutic potential. These gene therapy tools could in the future provide therapeutic help both for patients with mitochondrial disease as well as in preventing the transfer of pathogenic mtDNA mutations from a mother to her offspring.
    Keywords:  Gene therapy; Genetic engineering; Oxidative phosphorylation; Restriction endonuclease; Zinc finger nuclease; mitoTALEN
  8. J Pharmacol Toxicol Methods. 2022 Aug 22. pii: S1056-8719(22)00056-9. [Epub ahead of print] 107209
      Mitochondria is an essential organelle; it produces 95% of the adenine triphosphate (ATP) of cells, their dysfunction is related to the pathogenesis of multiple diseases, such as diabetes mellitus, cardiovascular and neurological disorders. Various pharmacologic agents are known to target mitochondrial function. Moreover, the toxic side effects of multiple drugs used to treat diseases are related to the impairment of mitochondrial function. Thus, there is a need to develop a method to evaluate the effect of pharmacologic agents for their potential and side effects to identify effective mitochondrial-modulating agents. Therefore, the objective of this study was to develop and validate an ex-vivo method for studying the effect of pharmacologic agents on mitochondrial function and rescue of dysfunction. Dimethyl sulfoxide (DMSO) concentrations that drugs were soluble in and maintained mitochondrial function were determined. Metformin (MET) is a known mitochondrial complex-1 inhibitor tested for its ability to compromise mitochondrion function. Coenzyme Q10 (Q10) and Resveratrol (RSV), which are known to enhance mitochondrial function, were added alone and dose-dependent, tested for the ability to rescue metformin-induced mitochondrial dysfunction. Ex-vivo liver and brain mitochondrial function was assessed using an oxytherm Clark-type oxygen electrode. DMSO was found to be toxic above 10% and drugs insoluble below 5%. The addition of 0.5 mg/ml MET decreased liver and brain mitochondrial respiratory control rate (RCR). At the same time, Q10 improved RCR in normal mitochondria and a concentration-dependent manner in MET-induced dysfunctional mitochondria. RSV was added in the last step of the experiment to confirm that compromised function is due to MET. Hence this method can be used to screen pharmacological agents for their potential therapeutics or toxic effect on mitochondria.
    Keywords:  Complex enzyme activity; Electron transport chain; Mitochondrial bioenergetics; Mitochondrial toxicity; Oxidative phosphorylation; Respiratory control rate
  9. Int J Mol Sci. 2022 Aug 13. pii: 9076. [Epub ahead of print]23(16):
      Mitochondrial electron transport chain (ETC) inhibition is a phenomenon interesting in itself and serves as a tool for studying various cellular processes. Despite the fact that searching the term "rotenone" in PubMed returns more than 6900 results, there are many discrepancies regarding the directions of changes reported to be caused by this RTC inhibitor in the delicate redox balance of the cell. Here, we performed a multifaceted study of the popular ETC inhibitors rotenone and antimycin A, involving assessment of mitochondrial membrane potential and the production of hydrogen peroxide and superoxide anions at cellular and mitochondrial levels over a wide range of inhibitor concentrations (1 nmol/dm3-100 µmol/dm3). All measurements were performed with whole cells, with accompanying control of ATP levels. Antimycin A was more potent in hindering HepG2 cells' abilities to produce ATP, decreasing ATP levels even at a 1 nmol/dm3 concentration, while in the case of rotenone, a 10,000-times greater concentration was needed to produce a statistically significant decrease. The amount of hydrogen peroxide produced in the course of antimycin A biological activity increased rapidly at low concentrations and decreased below control level at a high concentration of 100 µmol/dm3. While both inhibitors influenced cellular superoxide anion production in a comparable manner, rotenone caused a greater increase in mitochondrial superoxide anions compared to a modest impact for antimycin A. IC50 values for rotenone and antimycin A with respect to HepG2 cell survival were of the same order of magnitude, but the survival curve of cells treated with rotenone was clearly biphasic, suggesting a concentration-dependent mode of biological action. We propose a clear experimental setup allowing for complete and credible analysis of the redox state of cells under stress conditions which allows for better understanding of the effects of ETC inhibition.
    Keywords:  antimycin A; electron transport chain inhibition; mitochondrial membrane potential; reactive oxygen species; rotenone
  10. Cell Death Dis. 2022 Aug 25. 13(8): 735
      Metabolic status is essential in maintaining normal functions of hematopoietic stem cells (HSCs). However, how the dynamic of the mitochondrion, as a central organelle in metabolism, is molecularly regulated to orchestrate metabolism and HSC stemness remains to be elucidated. Here, we focus on the role of Zeb1, a well-characterized epithelial-to-mesenchymal transition (EMT) inducer which has been demonstrated to confer stem-cell-like characteristics in multiple cancer types in stemness regulation of HSCs. Using a Zeb1-tdTomato reporter mouse model, we find that Zeb1+Lin-Sca-1+c-Kit+ cells (Zeb1+-LSKs) represent a subset of functional long-term HSCs. Zeb1+LSKs exhibit a reduced reactive oxygen species (ROS) level, low mitochondrial mass, low mitochondrial membrane potential (MMP), and particularly small, round fragmented mitochondria. Of note, ectopic expression of Zeb1 leads to a fragmented mitochondrial morphology with a low mitochondrial metabolic status in EML cells. In addition, Zeb1-knockout (Zeb1-KO) LSKs from fetal liver display an exhausted stem-cell activity. Zeb1 deficiency results in elongated and tubulated mitochondria with increased mitochondrial mass, elevated MMP, and higher ROS production. Mechanistically, Zeb1 acts as a transcriptional suppressor on the key mitochondrial-fusion protein Mitofusin-2 (encoded by Mfn2). We highlight an important role of Zeb1 in the regulation of mitochondrial morphology in HSC and the metabolic control of HSC stemness by repressing Mfn2-mediated mitochondrial fusion.
  11. Cancers (Basel). 2022 Aug 09. pii: 3851. [Epub ahead of print]14(16):
      PT-112 is a novel pyrophosphate-platinum conjugate, with clinical activity reported in advanced pretreated solid tumors. While PT-112 has been shown to induce robust immunogenic cell death (ICD) in vivo but only minimally bind DNA, the molecular mechanism underlying PT-112 target disruption in cancer cells is still under elucidation. The murine L929 in vitro system was used to test whether differential metabolic status alters PT-112's effects, including cell cytotoxicity. The results showed that tumor cells presenting mutations in mitochondrial DNA (mtDNA) (L929dt and L929dt cybrid cells) and reliant on glycolysis for survival were more sensitive to cell death induced by PT-112 compared to the parental and cybrid cells with an intact oxidative phosphorylation (OXPHOS) pathway (L929 and dtL929 cybrid cells). The type of cell death induced by PT-112 did not follow the classical apoptotic pathway: the general caspase inhibitor Z-VAD-fmk did not inhibit PT-112-induced cell death, alone or in combination with the necroptosis inhibitor necrostatin-1. Interestingly, PT-112 initiated autophagy in all cell lines, though this process was not complete. Autophagy is known to be associated with an integrated stress response in cancer cells and with subsequent ICD. PT-112 also induced a massive accumulation of mitochondrial reactive oxygen species, as well as changes in mitochondrial polarization-only in the sensitive cells harboring mitochondrial dysfunction-along with calreticulin cell-surface exposure consistent with ICD. PT-112 substantially reduced the amount of mitochondrial CoQ10 in L929 cells, while the basal CoQ10 levels were below our detection limits in L929dt cells, suggesting a potential relationship between a low basal level of CoQ10 and PT-112 sensitivity. Finally, the expression of HIF-1α was much higher in cells sensitive to PT-112 compared to cells with an intact OXPHOS pathway, suggesting potential clinical applications.
    Keywords:  CoQ10; HIF-1α; ICD; PT-112; cancer cell death; immunogenic cell death; mitochondrial ROS
  12. Oncoimmunology. 2022 ;11(1): 2114740
      ATP synthase inhibitory factor 1 (ATPIF1) is a mitochondrial protein with an activity in inhibition of F1Fo-ATP synthase. ATPIF1 activity remains unknown in the control of immune activity of T cells. In this study, we identified ATPIF1 activity in the induction of CD8+ T cell function in tumor models through genetic approaches. ATPIF1 gene inactivation impaired the immune activities of CD8+ T cells leading to quick tumor growth (B16 melanoma and Lewis lung cancer) in ATPIF1-KO mice. The KO T cells exhibited a reduced activity in proliferation and IFN-γ secretion with metabolic reprogramming of increased glycolysis and decreased oxidative phosphorylation (OXPHOS) after activation. T cell exhaustion was increased in the tumor infiltrating leukocytes (TILs) of KO mice as revealed by the single-cell RNA sequencing (scRNA-seq) and confirmed by flow cytometry. In contrast, ATPIF1 overexpression in T cells increased expression of IFN-γ and Granzyme B, subset of central memory T cells in CAR-T cells, and survival rate of NALM-6 tumor-bearing mice. These data demonstrate that ATPIF1 deficiency led to tumor immune deficiency through induction of T cell exhaustion. ATPIF1 overexpression enhanced the T cell tumor immunity. Therefore, ATPIF1 is a potential molecular target in the modulation of antitumor immunity of CD8+ T cells in cancer immunotherapy. Induction of ATPIF1 activity may promote CAR-T activity in cancer therapy.
    Keywords:  ATPIF1; CD19 CAR-T; CD8+ T cells; single cell RNA sequencing
  13. Cancer Res. 2022 Aug 23. pii: CAN-22-0162. [Epub ahead of print]
      Cancer-associated fibroblasts (CAF) are key regulators of tumorigenesis. Further insights into the tumor promoting mechanisms of action of CAFs could help improve cancer diagnosis and treatment. Here we show that the formin mDia2 regulates the positioning and function of mitochondria in dermal fibroblasts, thereby promoting a pro-tumorigenic CAF phenotype. Mechanistically, mDia2 stabilized the mitochondrial trafficking protein MIRO1. Loss of mDia2 or MIRO1 in fibroblasts or CAFs reduced the presence of mitochondria and ATP levels near the plasma membrane and at CAF-tumor cell contact sites, caused metabolic alterations characteristic of mitochondrial dysfunction, and suppressed the secretion of pro-tumorigenic proteins. In mouse models of squamous carcinogenesis, genetic or pharmacological inhibition of mDia2, MIRO1, or their common upstream regulator activin A inhibited tumor formation. Consistently, co-upregulation of mDia2 and MIRO1 in the stroma of various human cancers negatively correlated with survival. This work unveils a key role of mitochondria in the pro-tumorigenic CAF phenotype and identifies an activin A/mDia2/MIRO1 signaling axis in CAFs with diagnostic and therapeutic potential.
  14. Curr Biol. 2022 Aug 22. pii: S0960-9822(22)01126-5. [Epub ahead of print]32(16): R891-R894
      Mitochondria are central to apoptosis, an immunologically silent form of cell death. The mitochondrial, or 'intrinsic', apoptotic pathway is activated when the permeabilized mitochondrial membrane of stressed cells releases apoptotic effectors. A new study now characterizes how mitochondria are involved in the switch from pyroptotic to necroptotic cell death.
  15. EBioMedicine. 2022 Aug 19. pii: S2352-3964(22)00413-3. [Epub ahead of print]83 104231
      Apoptosis-inducing factor (AIF) is a mitochondrial intermembrane space flavoprotein with diverse functions in cellular physiology. In this regard, a large number of studies have elucidated AIF's participation to chromatin condensation during cell death in development, cancer, cardiovascular and brain disorders. However, the discovery of rare AIFM1 mutations in patients has shifted the interest of biomedical researchers towards AIF's contribution to pathogenic mechanisms underlying inherited AIFM1-linked metabolic diseases. The functional characterization of AIF binding partners has rapidly advanced our understanding of AIF biology within the mitochondria and beyond its widely reported role in cell death. At the present time, it is reasonable to assume that AIF contributes to cell survival by promoting biogenesis and maintenance of the mitochondrial oxidative phosphorylation (OXPHOS) system. With this review, we aim to outline the current knowledge around the vital role of AIF by primarily focusing on currently reported human diseases that have been linked to AIFM1 deficiency.
    Keywords:  Aapoptosis-inducing factor (AIF); CHCHD4; Mitochondria; Mitochondrial diseases; Oxidative phosphorylation (OXPHOS)
  16. Carbohydr Polym. 2022 Nov 01. pii: S0144-8617(22)00783-4. [Epub ahead of print]295 119878
      At present, the tumor's poor oxygen perfusion and limited tumor drug permeation are the major bottlenecks that limit the therapeutic effectiveness of the oxygen-sensitive antitumor therapies, like doxorubicin (Dox)-mediated chemotherapy and photodynamic therapy (PDT). To our best knowledge, the abnormal tumor mitochondria oxidative phosphorylation (OXPHOS) was the vital cause of such phenomenon, which induced the hypoxia tumor microenvironment and enhanced drug efflux from tumor cells via enhanced multidrug resistance protein 1 (MDR-1) expression. In this study, it was newly revealed that biguanide-modified chitosan (Bi-Ch) possessed ideal mitochondria depression capacity, leading to the following decreased dosage needed to disrupt mitochondrial function to reverse tumor hypoxia and depress MDR-1 expression. By doing this, Bi-Ch effectively enhanced Dox accumulation in tumor cells and amplified its cytotoxicity owing to the amplified ROS generation by Dox. Therefore, Bi-Ch could be used to improve the efficacy of oxygen-sensitive tumor therapies in vitro.
    Keywords:  Chitosan; Metformin; Mitochondria oxidative phosphorylation; Multidrug resistance; Oxygen-sensitive tumor therapies
  17. Cancer Lett. 2022 Aug 20. pii: S0304-3835(22)00355-X. [Epub ahead of print] 215871
      Treatments targeting oncogenic fusion proteins are notable examples of successful drug development. Abnormal splicing of genes resulting in fusion proteins is a critical driver of various tumors, but the underlying mechanism remains poorly understood. Here, we show that SUMOylation of the fusion protein Synaptojanin 2 binding protein-Cytochrome-c oxidase 16 (SYNJ2BP-COX16) at K107 induces mitochondrial fission in breast cancer and that the K107 site regulates SYNJ2BP-COX16 mitochondrial subcellular localization. Compared with a non-SUMOylated K107R mutant, wild-type SYNJ2BP-COX16 contributed to breast cancer cell proliferation and metastasis in vivo and in vitro by increasing adenosine triphosphate (ATP) production and cytochrome-c oxidase (COX) activity. SUMOylated SYNJ2BP-COX16 recruits dynamin-related protein 1 (DRP1) to the mitochondria to promote ubiquitin-conjugating enzyme 9 (UBC9) binding to DRP1, enhance SUMOylation of DRP1 and phosphorylation of DRP1 at S616, and then induce mitochondrial fission. Moreover, Mdivi-1, an inhibitor of DRP1 phosphorylation, decreased the localization of DRP1 in mitochondria, and prevents SYNJ2BP-COX16 induced mitochondrial fission, cell proliferation and metastasis. Based on these data, SYNJ2BP-COX16 promotes breast cancer progression through the phosphorylation of DRP1 and subsequent induction of mitochondrial fission, indicating that SUMOylation at the K107 residue of SYNJ2BP-COX16 is a novel potential treatment target for breast cancer.
  18. Nucleic Acids Res. 2022 Aug 24. pii: gkac699. [Epub ahead of print]
      Mitochondrial tRNAs are indispensable for the intra-mitochondrial translation of genes related to respiratory subunits, and mutations in mitochondrial tRNA genes have been identified in various disease patients. However, the molecular mechanism underlying pathogenesis remains unclear due to the lack of animal models. Here, we established a mouse model, designated 'mito-mice tRNALeu(UUR)2748', that carries a pathogenic A2748G mutation in the tRNALeu(UUR) gene of mitochondrial DNA (mtDNA). The A2748G mutation is orthologous to the human A3302G mutation found in patients with mitochondrial diseases and diabetes. A2748G mtDNA was maternally inherited, equally distributed among tissues in individual mice, and its abundance did not change with age. At the molecular level, A2748G mutation is associated with aberrant processing of precursor mRNA containing tRNALeu(UUR) and mt-ND1, leading to a marked decrease in the steady-levels of ND1 protein and Complex I activity in tissues. Mito-mice tRNALeu(UUR)2748 with ≥50% A2748G mtDNA exhibited age-dependent metabolic defects including hyperglycemia, insulin insensitivity, and hepatic steatosis, resembling symptoms of patients carrying the A3302G mutation. This work demonstrates a valuable mouse model with an inheritable pathological A2748G mutation in mt-tRNALeu(UUR) that shows metabolic syndrome-like phenotypes at high heteroplasmy level. Furthermore, our findings provide molecular basis for understanding A3302G mutation-mediated mitochondrial disorders.
  19. Elife. 2022 Aug 23. pii: e79422. [Epub ahead of print]11
      Pyruvate kinase (PK) and the phosphoenolpyruvate (PEP) cycle play key roles in nutrient-stimulated KATP channel closure and insulin secretion. To identify the PK isoforms involved, we generated mice lacking β-cell PKm1, PKm2, and mitochondrial PEP carboxykinase (PCK2) that generates mitochondrial PEP. Glucose metabolism generates both glycolytic and mitochondrially-derived PEP, which triggers KATP closure through local PKm1 and PKm2 signaling at the plasma membrane. Amino acids, which generate mitochondrial PEP without producing glycolytic fructose 1,6-bisphosphate to allosterically activate PKm2, signal through PKm1 to raise ATP/ADP, close KATP channels, and stimulate insulin secretion. Raising cytosolic ATP/ADP with amino acids is insufficient to close KATP channels in the absence of PK activity or PCK2, indicating that KATP channels are primarily regulated by PEP that provides ATP via plasma membrane-associated PK, rather than mitochondrially-derived ATP. Following membrane depolarization, the PEP cycle is also involved in an 'off-switch' that facilitates KATP channel reopening and Ca2+ extrusion, as shown by PK activation experiments and β-cell PCK2 deletion, which prolongs Ca2+ oscillations and increases insulin secretion. In conclusion, the differential response of PKm1 and PKm2 to the glycolytic and mitochondrial sources of PEP influences the β-cell nutrient response, and controls the oscillatory cycle regulating insulin secretion.
    Keywords:  cell biology; mouse
  20. J Oral Pathol Med. 2022 Aug 23.
      BACKGROUND: Radiation damage to salivary gland (SG) is inevitable in head and neck cancer patients receiving radiotherapy. Safe and effective treatments for protecting SGs from radiation are still unavailable. Mitochondrial damage is a critical mechanism in irradiated SG, however, treatment targeting mitochondria has not received much attention. Nicotinamide (NAM) is a key component of the mitochondrial metabolism. Here, we investigated the effects and underlying mechanisms of NAM on protecting irradiated submandibular gland (SMG).METHODS: SMG cells and tissues were randomly divided into four groups: control, NAM alone, radiation alone, and radiation with NAM pretreatment. Cell viability was detected by PrestoBlue™ cell viability reagent. Histopathological alterations were observed with HE staining. Pilocarpine-stimulated saliva was measured from Wharton's duct. Cell apoptosis was determined by flow cytometry and TUNEL assay. Nicotinamide phosphoribosyl transferase (NAMPT) was examined with immunofluorescence. The levels of nicotinamide adenine dinucleotide (NAD), mitochondrial membrane potential (MMP) and ATP were measured with the relevant kits. The mitochondrial ultrastructure was observed under transmission electron microscopy.
    RESULTS: NAM significantly mitigated radiation damage both in vitro and in vivo. Also, NAM improved saliva secretion and reduced radiation-induced apoptosis in irradiated SMGs. Moreover, NAM improved NAMPT and the levels of NAD/ATP and MMP, all of which were decreased by radiation in SMG cells. Importantly, NAM protected the mitochondrial ultrastructure from radiation.
    CONCLUSION: These findings demonstrate that NAM alleviates radiation damage in SMG by replenishing NAD and maintaining mitochondrial function and ultrastructure, suggesting that NAM could be used as a prospective radioprotectant for preventing radiation sialadenitis.
    Keywords:  NAD; mitochondrion; nicotinamide; radiation; submandibular gland
  21. Leukemia. 2022 Aug 23.
      Internal tandem duplications (ITD) in the receptor tyrosine kinase FLT3 occur in 25 % of acute myeloid leukemia (AML) patients, drive leukemia progression and confer a poor prognosis. Primary resistance to FLT3 kinase inhibitors (FLT3i) quizartinib, crenolanib and gilteritinib is a frequent clinical challenge and occurs in the absence of identifiable genetic causes. This suggests that adaptive cellular mechanisms mediate primary resistance to on-target FLT3i therapy. Here, we systematically investigated acute cellular responses to on-target therapy with multiple FLT3i in FLT3-ITD + AML using recently developed functional translatome proteomics (measuring changes in the nascent proteome) with phosphoproteomics. This pinpointed AKT-mTORC1-ULK1-dependent autophagy as a dominant resistance mechanism to on-target FLT3i therapy. FLT3i induced autophagy in a concentration- and time-dependent manner specifically in FLT3-ITD + cells in vitro and in primary human AML cells ex vivo. Pharmacological or genetic inhibition of autophagy increased the sensitivity to FLT3-targeted therapy in cell lines, patient-derived xenografts and primary AML cells ex vivo. In mice xenografted with FLT3-ITD + AML cells, co-treatment with oral FLT3 and autophagy inhibitors synergistically impaired leukemia progression and extended overall survival. Our findings identify a molecular mechanism responsible for primary FLT3i treatment resistance and demonstrate the pre-clinical efficacy of a rational combination treatment strategy targeting both FLT3 and autophagy induction.
  22. Cancer Gene Ther. 2022 Aug 23.
      Metabolic reprogramming is a hallmark of cancer development, progression, and metastasis. Several metabolic pathways such as glycolysis, tricarboxylic acid (TCA) cycle, lipid metabolism, and glutamine catabolism are frequently altered to support cancer growth. Importantly, the activity of the rate-limiting metabolic enzymes in these pathways are specifically modulated in cancer cells. This is achieved by transcriptional, translational, and post translational regulations that enhance the expression, activity, stability, and substrate sensitivity of the rate-limiting enzymes. These mechanisms allow the enzymes to retain increased activity supporting the metabolic needs of rapidly growing tumors, sustain their survival in the hostile tumor microenvironments and in the metastatic lesions. In this review, we primarily focused on the post translational modifications of the rate-limiting enzymes in the glucose and glutamine metabolism, TCA cycle, and fatty acid metabolism promoting tumor progression and metastasis.
  23. Front Pharmacol. 2022 ;13 947372
      Recent studies have proposed that pyruvate dehydrogenase E1 component subunit alpha (PDHA1), a cuproptosis-key gene, is crucial to the glucose metabolism reprogram of tumor cells. However, the functional roles and regulated mechanisms of PDHA1 in multiple cancers are largely unknown. The Cancer Genome Atlas (TCGA), GEPIA2, and cBioPortal databases were utilized to elucidate the function of PDHA1 in 33 tumor types. We found that PDHA1 was aberrantly expressed in most cancer types. Lung adenocarcinoma (LUAD) patients with high PDHA1 levels were significantly correlated with poor prognosis of overall survival (OS) and first progression (FP). Kidney renal clear cell carcinoma (KIRC) patients with low PDHA1 levels displayed poor OS and disease-free survival (DFS). However, for stomach adenocarcinoma (STAD), the downregulated PDHA1 expression predicted a good prognosis in patients. Moreover, we evaluated the mutation diversity of PDHA1 in cancers and their association with prognosis. We also analyzed the protein phosphorylation and DNA methylation of PDHA1 in various tumors. The PDHA1 expression was negatively correlated with tumor-infiltrating immune cells, such as myeloid dendritic cells (DCs), B cells, and T cells in pan-cancers. Mechanically, we used single-cell sequencing to discover that the PDHA1 expression had a close link with several cancer-associated signaling pathways, such as DNA damage, cell invasion, and angiogenesis. At last, we conducted a co-expressed enrichment analysis and showed that aberrantly expressed PDHA1 participated in the regulation of mitochondrial signaling pathways, including oxidative phosphorylation, cellular respiration, and electron transfer activity. In summary, PDHA1 could be a prognostic and immune-associated biomarker in multiple cancers.
    Keywords:  PDHA1; immunotherapy; mutation; pan-cancer; prognosis
  24. Mol Metab. 2022 Aug 19. pii: S2212-8778(22)00145-4. [Epub ahead of print] 101576
      OBJECTIVE: Dicer is an enzyme that processes microRNAs (miRNAs) precursors into mature miRNAs, which have been implicated in various aspects of cancer progressions, such as clinical aggressiveness, prognosis, and survival outcomes. We previously showed that high expression of Dicer is associated with gemcitabine (GEM) resistance in pancreatic ductal adenocarcinoma (PDAC); thus, in this study, we aimed to focus on how Dicer is involved in GEM resistance in PDAC, including cancer prognosis, cell proliferation, and metabolic regulation.METHODS: We generated stable shRNA knockdown of Dicer in GEM-resistant PANC-1 (PANC-1 GR) cells and explored cell viability by MTT and clonogenicity assays. Metabolomic profiling was employed to investigate metabolic changes between parental cells, PANC-1, and PANC-1 GR cells, and further implied to compare their sensitivity to the glutaminase inhibitor, CB839, and GEM treatments. To identify putative phosphorylation site involves with Dicer and its effects on GEM resistance in PDAC cells, we further generated phosphomimetic or phosphomutant Dicer at S1016 site and examined the changes in drug sensitivity, metabolic alteration, and miRNA regulation.
    RESULTS: We observed that high Dicer levels in pancreatic ductal adenocarcinoma cells were positively correlated with advanced pancreatic cancer and acquired resistance to GEM. Metabolomic analysis indicated that PANC-1 GR cells rapidly utilised glutamine as their major fuel and increased levels of glutaminase (GLS): glutamine synthetase (GLUL) ratio which is related to high Dicer expression. In addition, we found that phosphomimetic Dicer S1016E but not phosphomutant Dicer S1016A facilitated miRNA maturation, causing an imbalance in GLS and GLUL and resulting in an increased response to GLS inhibitors.
    CONCLUSION: Our results suggest that phosphorylation of Dicer on site S1016 affects miRNA biogenesis and glutamine metabolism in GEM-resistant pancreatic cancer.
    Keywords:  Dicer phosphorylation; Gemcitabine resistance; Glutamine metabolism; Pancreatic ductal adenocarcinoma; miRNA biogenesis
  25. Redox Biol. 2022 Aug 18. pii: S2213-2317(22)00219-1. [Epub ahead of print]56 102447
      The regulation of mitochondria function and health is a central node in tissue maintenance, ageing as well as the pathogenesis of various diseases. However, the maintenance of an active mitochondrial functional state and its quality control mechanisms remain incompletely understood. By studying mice with a mitochondria-targeted reporter that shifts its fluorescence from "green" to "red" with time (MitoTimer), we found MitoTimer fluorescence spectrum was heavily dependent on the oxidative metabolic state in the skeletal muscle fibers. The mitoproteolytic activity was enhanced in an energy dependent manner, and accelerated the turnover of MitoTimer protein and respiratory chain substrate, responsible for a green predominant MitoTimer fluorescence spectrum under the oxidative conditions. PGC1α, as well as anti-ageing regents promoted enhanced mitoproteolysis. In addition, cells with the green predominant mitochondria exhibited lower levels of MitoSox and protein carbonylation, indicating a favorable redox state. Thus, we identified MitoTimer as a probe for mitoproteolytic activity in vivo and found a heightened control of mitoproteolysis in the oxidative metabolic state, providing a framework for understanding the maintenance of active oxidative metabolism while limiting oxidative damages.
    Keywords:  MitoTimer; Mitoproteolysis; Muscle fiber type; Oxidative metabolism; PGC-1α
  26. Cancers (Basel). 2022 Aug 13. pii: 3917. [Epub ahead of print]14(16):
      Two-dimensional cell cultures are established models in research for studying and perturbing cell-type specific functions. However, many limitations apply to the cell growth in a monolayer using standard cell culture media. Although they have been used for decades, their formulations do not mimic the composition of the human cell environment. In this study, we analyzed the impact of a newly formulated human plasma-like media (HPLM) on cell proliferation, mitochondrial bioenergetics, and alterations of drug efficacies using three distinct cancer cell lines. Using high-resolution respirometry, we observed that cells grown in HPLM displayed significantly altered mitochondrial bioenergetic profiles, particularly related to mitochondrial density and mild uncoupling of respiration. Furthermore, in contrast to standard media, the growth of cells in HPLM unveiled mitochondrial dysfunction upon exposure to the FDA-approved kinase inhibitor sunitinib. This seemingly context-dependent side effect of this drug highlights that the selection of the cell culture medium influences the assessment of cancer drug sensitivities. Thus, we suggest to prioritize media with a more physiological composition for analyzing bioenergetic profiles and to take it into account for assigning drug efficacies in the cell culture model of choice.
    Keywords:  cancer cells; cell bioenergetics; cell culture media; cell proliferation; kinase inhibitor; mitochondrial function
  27. Nutrients. 2022 Aug 18. pii: 3395. [Epub ahead of print]14(16):
      Myelosuppression is a common and intractable side effect of cancer therapies including radiotherapy and chemotherapy, while the underlying mechanism remains incompletely understood. Here, using a mouse model of radiotherapy-induced myelosuppression, we show that inorganic phosphate (Pi) metabolism is acutely inhibited in hematopoietic stem cells (HSCs) during irradiation-induced myelosuppression, and closely correlated with the severity and prognosis of myelosuppression. Mechanistically, the acute Pi metabolic inhibition in HSCs results from extrinsic Pi loss in the bone marrow niche and the intrinsic transcriptional suppression of soluble carrier family 20 member 1 (SLC20A1)-mediated Pi uptake by p53. Meanwhile, Pi metabolic inhibition blunts irradiation-induced Akt hyperactivation in HSCs, thereby weakening its ability to counteract p53-mediated Pi metabolic inhibition and the apoptosis of HSCs and consequently contributing to myelosuppression progression. Conversely, the modulation of the Pi metabolism in HSCs via a high Pi diet or renal Klotho deficiency protects against irradiation-induced myelosuppression. These findings reveal that Pi metabolism and HSC survival are causally linked by the Akt/p53-SLC20A1 axis during myelosuppression and provide valuable insights into the pathogenesis and management of myelosuppression.
    Keywords:  apoptosis; hematopoietic stem cell; inorganic phosphate; irradiation; myelosuppression
  28. Analyst. 2022 Aug 26.
      Adenosine triphosphate (ATP) is a direct energy source in cells and the core of the biochemical system, and is closely related to various metabolic activities in living organisms. Therefore, designing a simple and rapid ATP detection method is significant to study its physiological function. Herein, a dual-channel fluorescent probe RhB-NA for the in situ imaging of ATP in living cells was designed and synthesized. When ATP bound to RhB-NA, the spirolactam in rhodamine B was induced to open, resulting in a new fluorescence response at 589 nm. Notably, in cell imaging, the treatment of HeLa cells with exogenous H2O2 and H2S, which have certain effects on the mitochondria, confirmed that RhB-NA could detect fluctuations in ATP levels after the mitochondrial state was affected. We believe that RhB-NA has far-reaching significance for studying certain physiological diseases caused by abnormal ATP levels.
  29. Angew Chem Int Ed Engl. 2022 Aug 25.
      Target identification remains a critical challenge in inorganic drug discovery to deconvolute potential polypharmacology. Here, we describe an improved approach to prioritize candidate protein targets based on a combination of dose-dependent chemoproteomics and treatment effects in living cancer cells for the rhenium tricarbonyl compound TRIP. Chemoproteomics revealed 89 distinct dose-dependent targets with concentrations of competitive saturation between 0.1-32 µM despite the broad proteotoxic effects of TRIP. Target response networks revealed two highly probable targets of which the Fe-S cluster biogenesis factor NUBP2 was competitively saturated by free TRIP at nanomolar concentrations. Importantly, TRIP treatment led to a down-regulation of Fe-S cluster-containing proteins and upregulated ferritin. Fe-S cluster depletion was further verified by assessing mitochondrial bioenergetics. Consequently, TRIP emerges as a first-in-class modulator of the scaffold protein NUBP2, which disturbs Fe-S cluster biogenesis at sub-cytotoxic concentrations in ovarian cancer cells.
    Keywords:  Cancer; Proteomics; Rhenium; mode of action; target identification
  30. Aging Cell. 2022 Aug 22. e13669
      Mitochondrial dysfunction plays an important role in the aging process. However, the mechanism by which this dysfunction causes aging is not fully understood. The accumulation of mutations in the mitochondrial genome (or "mtDNA") has been proposed as a contributor. One compelling piece of evidence in support of this hypothesis comes from the PolgD257A/D257A mutator mouse (Polgmut/mut ). These mice express an error-prone mitochondrial DNA polymerase that results in the accumulation of mtDNA mutations, accelerated aging, and premature death. In this paper, we have used the Polgmut/mut model to investigate whether the age-related biological effects observed in these mice are triggered by oxidative damage to the DNA that compromises the integrity of the genome. Our results show that mutator mouse has significantly higher levels of 8-oxoguanine (8-oxoGua) that are correlated with increased nuclear DNA (nDNA) strand breakage and oxidative nDNA damage, shorter average telomere length, and reduced mtDNA integrity. Based on these results, we propose a model whereby the increased level of reactive oxygen species (ROS) associated with the accumulation of mtDNA mutations in Polgmut/mut mice results in higher levels of 8-oxoGua, which in turn lead to compromised DNA integrity and accelerated aging via increased DNA fragmentation and telomere shortening. These results suggest that mitochondrial play a central role in aging and may guide future research to develop potential therapeutics for mitigating aging process.
    Keywords:  8-oxoguanine; aging; mitochondria; oxidative stress; telomeres
  31. iScience. 2022 Aug 19. 25(8): 104787
      Despite much progress in developing better drugs, many patients with acute myeloid leukemia (AML) still die within a year of diagnosis. This is partly because it is difficult to identify therapeutic targets that are effective across multiple AML subtypes. One common factor across AML subtypes is the presence of a block in differentiation. Overcoming this block should allow for the identification of therapies that are not dependent on a specific mutation for their efficacy. Here, we used a phenotypic screen to identify compounds that stimulate differentiation in genetically diverse AML cell lines. Lead compounds were shown to decrease tumor burden and to increase survival in vivo. Using multiple complementary target deconvolution approaches, these compounds were revealed to be anti-mitotic tubulin disruptors that cause differentiation by inducing a G2-M mitotic arrest. Together, these results reveal a function for tubulin disruptors in causing differentiation of AML cells.
    Keywords:  Biological sciences; Cancer; Chemistry; Molecular biology; Molecular medicine
  32. Cancers (Basel). 2022 Aug 10. pii: 3858. [Epub ahead of print]14(16):
      There is a great need for non-invasive tools that inform of an early molecular response to cancer therapeutic treatment. Here, we tested the hypothesis that proteolytically resistant proteins could be candidate circulating tumor biomarkers for cancer therapy. Proteins resistant to proteolysis are drastically under-sampled by current proteomic workflows. These proteins could be reliable sensors for the response to therapy since they are likely to stay longer in circulation. We selected manganese superoxide dismutase (SOD2), a mitochondrial redox enzyme, from a screening of proteolytic resistant proteins in breast cancer (BC). First, we confirmed the robustness of SOD2 and determined that its proteolytic resistance is mediated by its quaternary protein structure. We also proved that the release of SOD2 upon chemotherapy treatment correlates with cell death in BC cells. Then, after confirming that SOD2 is very stable in human serum, we sought to measure its circulating levels in a cohort of BC patients undergoing neoadjuvant therapy. The results showed that circulating levels of SOD2 increased when patients responded to the treatment according to the tumor shrinkage during neoadjuvant chemotherapy. Therefore, the measurement of SOD2 levels in plasma could improve the non-invasive monitoring of the therapeutic treatment in breast cancer patients. The identification of circulating biomarkers linked to the tumor cell death induced by treatment could be useful for monitoring the action of the large number of cancer drugs currently used in clinics. We envision that our approach could help uncover candidate tumor biomarkers to measure a tumor's response to cancer therapy in real time by sampling the tumor throughout the course of treatment.
    Keywords:  breast cancer; manganese superoxide dismutase (SOD2); response biomarkers; secretome
  33. Cell Rep. 2022 Aug 23. pii: S2211-1247(22)01027-0. [Epub ahead of print]40(8): 111210
      HOXB9 is an important transcription factor associated with unfavorable outcomes in patients with lung adenocarcinoma (LUAD). However, its degradation mechanism remains unclear. Here, we show that HOXB9 is a substrate of AMP kinase alpha (AMPKα). AMPK mediates HOXB9 T133 phosphorylation and downregulates the level of HOXB9 in mice and LUAD cells. Mechanistically, phosphorylated HOXB9 promoted E3 ligase Praja2-mediated HOXB9 degradation. Blocking HOXB9 phosphorylation by depleting AMPKα1/2 or employing the HOXB9 T133A mutant promoted tumor cell growth in cell culture and mouse xenografts via upregulation of HOXB9 and KRAS that is herein identified as a target of HOXB9. Clinically, AMPK activation levels in LUAD samples were positively correlated with pHOXB9 levels; higher pHOXB9 levels were associated with better survival of patients with LUAD. We thus present a HOXB9 degradation mechanism and demonstrate an AMPK-HOXB9-KRAS axis linking glucose-level-regulated AMPK activation to HOXB9 stability and KRAS gene expression, ultimately controlling LUAD progression.
    Keywords:  AMPK; CP: Cancer; CP: Metabolism; HOXB9 T133 phosphorylation; KRAS; LUAD; Praja2; metformin; ubiquitin-mediated degradation
  34. Liver Int. 2022 Aug 25.
      Acyl-CoA thioesterase 9 (ACOT9) is a critical regulator of cellular utilization of fatty acids by catalyzing the hydrolysis of acyl-CoA thioesters to non-esterified fatty acid and coenzyme A (CoA). Recently, ACOT9 was reported to participate in the pathogenesis of non-alcoholic liver disease (NAFLD), which arises from aberrant lipid metabolism and serves as a risk factor for hepatocellular carcinoma (HCC). However, the functions of ACOT9 in carcinogenesis and aberrant lipid metabolism in HCC remain unexplored. Here, we found that ACOT9 expression is significantly elevated in HCC at least in partial due to the down-regulation of miR-449c-3p. Upregulation of ACOT9 is closely associated with poor prognosis for patients with HCC. Knockdown of ACOT9 expression in HCC cells significantly decreased cell proliferation, colony formation, migration and invasion, mainly through suppression of G1-to-S cell cycle transition and epithelial-to-mesenchymal transition (EMT). By contrast, forced ACOT9 expression promoted HCC growth and metastasis. In addition, we found that ACOT9 reprogrammed lipid metabolism in HCC cells by increasing de novo lipogenesis. Furthermore, we demonstrated that increased lipogenesis was involved in ACOT9-promoted HCC growth and metastasis. Altogether, we demonstrate that ACOT9 plays a critical oncogenic role in the promotion of tumor growth and metastasis by reprogramming lipid metabolism in HCC, indicating ACOT9 as a potential therapeutic target in treatment of HCC.
    Keywords:  ACOT9; HCC; growth; lipid metabolism; metastasis
  35. Nutrients. 2022 Aug 17. pii: 3378. [Epub ahead of print]14(16):
      New therapies are needed to improve the low survival rates of patients with metastatic colon cancer. Evidence suggests that amino acid (AA) restriction can be used to target the altered metabolism of cancer cells. In this work, we evaluated the therapeutic potential of selective AA restriction in colon cancer. After observing anticancer activity in vitro, we prepared several artificial diets and evaluated their anticancer activity in two challenging animal models of metastatic colon cancer. These models were established by injecting CT26.WT murine colon cancer cells in the peritoneum (peritoneal dissemination) or in the tail vein (pulmonary metastases) of immunocompetent BALB/cAnNRj mice. Capecitabine, which is a first-line treatment for patients with metastatic colon cancer, was also evaluated in these models. Mice fed diet TC1 (a diet lacking 10 AAs) and diet TC5 (a diet with 6% casein, 5% glutamine, and 2.5% leucine) lived longer than untreated mice in both models; several mice survived the treatment. Diet TC5 was better than several cycles of capecitabine in both cancer models. Cysteine supplementation blocked the activity of diets TC1 and TC5, but cysteine restriction was not sufficient for activity. Our results indicated that artificial diets based on selective AA restriction have therapeutic potential for colon cancer.
    Keywords:  amino acids; anticancer activity; cancer metabolism; colorectal cancer; cysteine; glutamine; leucine; metastasis; selective amino acid restriction therapy
  36. Proc Natl Acad Sci U S A. 2022 Aug 30. 119(35): e2205456119
      Triple negative breast cancer (TNBC) metastases are assumed to exhibit similar functions in different organs as in the original primary tumor. However, studies of metastasis are often limited to a comparison of metastatic tumors with primary tumors of their origin, and little is known about the adaptation to the local environment of the metastatic sites. We therefore used transcriptomic data and metabolic network analyses to investigate whether metastatic tumors adapt their metabolism to the metastatic site and found that metastatic tumors adopt a metabolic signature with some similarity to primary tumors of their destinations. The extent of adaptation, however, varies across different organs, and metastatic tumors retain metabolic signatures associated with TNBC. Our findings suggest that a combination of anti-metastatic approaches and metabolic inhibitors selected specifically for different metastatic sites, rather than solely targeting TNBC primary tumors, may constitute a more effective treatment approach.
    Keywords:  gene expression; genome-scale metabolic models; metastasis; systems biology; triple negative breast cancer
  37. Cell Rep. 2022 Aug 23. pii: S2211-1247(22)01074-9. [Epub ahead of print]40(8): 111256
      Immunotherapy is improving the prognosis and survival of cancer patients, but despite encouraging outcomes in different cancers, the majority of tumors are resistant to it, and the immunotherapy combinations are often accompanied by severe side effects. Here, we show that a periodic fasting-mimicking diet (FMD) can act on the tumor microenvironment and increase the efficacy of immunotherapy (anti-PD-L1 and anti-OX40) against the poorly immunogenic triple-negative breast tumors (TNBCs) by expanding early exhausted effector T cells, switching the cancer metabolism from glycolytic to respiratory, and reducing collagen deposition. Furthermore, FMD reduces the occurrence of immune-related adverse events (irAEs) by preventing the hyperactivation of the immune response. These results indicate that FMD cycles have the potential to enhance the efficacy of anti-cancer immune responses, expand the portion of tumors sensitive to immunotherapy, and reduce its side effects.
    Keywords:  CP: Cancer; CP: Immunology; differential stress sensitization; fasting; fasting-mimicking diet; immunotherapy; inflammation; nutrition; side effects; triple-negative breast cancer
  38. Nat Commun. 2022 Aug 26. 13(1): 5021
      Noncanonical redox cofactors are attractive low-cost alternatives to nicotinamide adenine dinucleotide (phosphate) (NAD(P)+) in biotransformation. However, engineering enzymes to utilize them is challenging. Here, we present a high-throughput directed evolution platform which couples cell growth to the in vivo cycling of a noncanonical cofactor, nicotinamide mononucleotide (NMN+). We achieve this by engineering the life-essential glutathione reductase in Escherichia coli to exclusively rely on the reduced NMN+ (NMNH). Using this system, we develop a phosphite dehydrogenase (PTDH) to cycle NMN+ with ~147-fold improved catalytic efficiency, which translates to an industrially viable total turnover number of ~45,000 in cell-free biotransformation without requiring high cofactor concentrations. Moreover, the PTDH variants also exhibit improved activity with another structurally deviant noncanonical cofactor, 1-benzylnicotinamide (BNA+), showcasing their broad applications. Structural modeling prediction reveals a general design principle where the mutations and the smaller, noncanonical cofactors together mimic the steric interactions of the larger, natural cofactors NAD(P)+.