bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2023‒01‒08
23 papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Front Oncol. 2022 ;12 1063531
      Introduction: Cancer bioenergetics is an essential hallmark of neoplastic transformation. Warburg postulated that mitochondrial OXPHOS is impaired in cancer cells, leading to aerobic glycolysis as the primary metabolic pathway. However, mitochondrial function is altered but not entirely compromised in most malignancies, and that mitochondrial uncoupling is known to increase the carcinogenic potential and modifies treatment response by altering metabolic reprogramming. Our earlier study showed that transient DNP exposure increases glycolysis in human glioma cells (BMG-1). The current study investigated the persistent effect of DNP on the energy metabolism of BMG-1 cells and its influence on tumor progression in glioma xenografts.Methods: BMG-1 cells were treated with 2,4-dinitrophenol (DNP) in-vitro, to establish the OXPHOS-modified (OPM-BMG) cells. Further cellular metabolic characterization was carried out in both in-vitro cellular model and in-vivo tumor xenografts to dissect the role of metabolic adaptation in these cells and compared them with their parental phenotype.
    Results and Discussion: Chronic exposure to DNP in BMG-1 cells resulted in dual-state hyper-energy metabolism with elevated glycolysis++ and OXPHOS++ compared to parental BMG-1 cells with low glycolysis+ and OXPHOS+. Tumor xenograft of OPM-BMG cells showed relatively increased tumor-forming potential and accelerated tumor growth in nude mice. Moreover, compared to BMG-1, OPM-BMG tumor-derived cells also showed enhanced migration and invasion potential. Although mitochondrial uncouplers are proposed as a valuable anti-cancer strategy; however, our findings reveal that prolonged exposure to uncouplers provides tumor growth advantage over the existing glioma phenotype that may lead to poor clinical outcomes.
    Keywords:  Warburg effect; cancer cell metabolism; glioma tumor; oxidative phosphorylation; tumor bioenergetics
  2. J Biol Chem. 2023 Jan 02. pii: S0021-9258(22)01308-4. [Epub ahead of print] 102865
      Mitochondrial ribosomes are specialized to translate the 13 membrane proteins encoded in the mitochondrial genome, which shapes the oxidative phosphorylation (OXPHOS) complexes essential for cellular energy metabolism. Despite the importance of mitochondrial translation control, it is challenging to identify and quantify the mitochondrial-encoded proteins due to their hydrophobic nature and low abundance. Here, we introduce a mass spectrometry-based proteomic method that combines biochemical isolation of mitochondria with pulse stable isotope labeling by amino acids in cell culture (pSILAC). Our method provides the highest protein identification rate with the shortest measurement time among currently available methods, enabling us to quantify 12 out of the 13 mitochondrial-encoded proteins. We applied this method to uncover the global picture of (post-)translational regulation of both mitochondrial- and nuclear-encoded subunits of OXPHOS complexes. We found that inhibition of mitochondrial translation led to degradation of orphan nuclear-encoded subunits that are considered to form subcomplexes with the mitochondrial-encoded subunits. This method should be readily applicable to study mitochondrial translation programs in many contexts, including oxidative stress and mitochondrial disease.
    Keywords:  Mitochondria; OXPHOS; Protein complex; Proteomics; Translation; pulse SILAC
  3. Theranostics. 2023 ;13(1): 324-338
      Rationale: Mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) mutations and subsequent metabolic defects are closely involved in tumorigenesis and progression in a cancer-type specific manner. To date, the mutational pattern of mtDNA somatic mutations in colorectal cancer (CRC) tissues and its clinical implication are still not completely clear. Methods: In the present study, we generated a large mtDNA somatic mutation dataset from three CRC cohorts (432, 1,015, and 845 patients, respectively) and then most comprehensively characterized the CRC-specific evolutionary pattern and its clinical implication. Results: Our results showed that the mtDNA control region (mtCTR) with a high mutation density exhibited a distinct mutation spectrum characterizing a high enrichment of L-strand C > T mutations, which was contrary to the H-strand C > T mutational bias observed in the mtDNA coding region (mtCDR) (P < 0.001). Further analysis clearly confirmed the relaxed evolutionary selection of mtCTR mutations, which was mainly characterized by the similar distribution of hypervariable region (HVS) and non-HVS mutation density. Moreover, significant negative selection was identified in mutations of mtDNA complex V (ATP6/ATP8) and tRNA loop regions. Although our data showed that oxidative metabolism was commonly increased in CRC cells, mtDNA somatic mutations in CRC tissues were not closely associated with mitochondrial biogenesis, oxidative metabolism, and clinical progression, suggesting a cancer-type specific relationship between mtDNA mutations and mitochondrial metabolic functions in CRC cells. Conclusion: Our study identified the CRC-specific evolutionary mode of mtDNA mutations, which is possibly matched to specific mitochondrial metabolic remodeling and confers new mechanic insight into CRC tumorigenesis.
    Keywords:  colorectal cancer; evolutionary selection; metabolic remodeling; mitochondrial DNA; somatic mutations
  4. Subcell Biochem. 2023 ;102 77-98
      Mitochondria are subcellular organelles present in most eukaryotic cells which play a significant role in numerous aspects of cell biology. These include carbohydrate and fatty acid metabolism to generate cellular energy through oxidative phosphorylation, apoptosis, cell signalling, haem biosynthesis and reactive oxygen species production. Mitochondrial dysfunction is a feature of many human ageing tissues, and since the discovery that mitochondrial DNA mutations were a major underlying cause of changes in oxidative phosphorylation capacity, it has been proposed that they have a role in human ageing. However, there is still much debate on whether mitochondrial DNA mutations play a causal role in ageing or are simply a consequence of the ageing process. This chapter describes the structure of mammalian mitochondria, and the unique features of mitochondrial genetics, and reviews the current evidence surrounding the role of mitochondrial DNA mutations in the ageing process. It then focusses on more recent discoveries regarding the role of mitochondrial dysfunction in stem cell ageing and age-related inflammation.
    Keywords:  Ageing; Cellular damage; DNA; Free radical damage; Mitochondria; Molecular damage; Mutations
  5. Nat Commun. 2023 Jan 03. 14(1): 39
      The mitochondrial F1FO-ATP synthase produces the bulk of cellular ATP. The soluble F1 domain contains the catalytic head that is linked via the central stalk and the peripheral stalk to the membrane embedded rotor of the FO domain. The assembly of the F1 domain and its linkage to the peripheral stalk is poorly understood. Here we show a dual function of the mitochondrial Hsp70 (mtHsp70) in the formation of the ATP synthase. First, it cooperates with the assembly factors Atp11 and Atp12 to form the F1 domain of the ATP synthase. Second, the chaperone transfers Atp5 into the assembly line to link the catalytic head with the peripheral stalk. Inactivation of mtHsp70 leads to integration of assembly-defective Atp5 variants into the mature complex, reflecting a quality control function of the chaperone. Thus, mtHsp70 acts as an assembly and quality control factor in the biogenesis of the F1FO-ATP synthase.
  6. Sci Rep. 2023 Jan 04. 13(1): 149
      Oncocytic thyroid cancer is characterized by the aberrant accumulation of abnormal mitochondria in the cytoplasm and a defect in oxidative phosphorylation. We performed metabolomics analysis to compare metabolic reprogramming among the oncocytic and non-oncocytic thyroid cancer cell lines XTC.UC1 and TPC1, respectively, and a normal thyroid cell line Nthy-ori 3-1. We found that although XTC.UC1 cells exhibit higher glucose uptake than TPC1 cells, the glycolytic intermediates are not only utilized to generate end-products of glycolysis, but also diverted to branching pathways such as lipid metabolism and the serine synthesis pathway. Glutamine is preferentially used to produce glutathione to reduce oxidative stress in XTC.UC1 cells, rather than to generate α-ketoglutarate for anaplerotic flux into the TCA cycle. Thus, growth, survival and redox homeostasis of XTC.UC1 cells rely more on both glucose and glutamine than do TPC1 cells. Furthermore, XTC.UC1 cells contained higher amounts of intracellular amino acids which is due to higher expression of the amino acid transporter ASCT2 and enhanced autophagy, thus providing the building blocks for macromolecules and energy production. These metabolic alterations are required for oncocytic cancer cells to compensate their defective mitochondrial function and to alleviate excess oxidative stress.
  7. Nat Rev Cancer. 2023 Jan 03.
      Reprogrammed metabolism is a hallmark of cancer. However, the metabolic dependency of cancer, from tumour initiation through disease progression and therapy resistance, requires a spectrum of distinct reprogrammed cellular metabolic pathways. These pathways include aerobic glycolysis, oxidative phosphorylation, reactive oxygen species generation, de novo lipid synthesis, fatty acid β-oxidation, amino acid (notably glutamine) metabolism and mitochondrial metabolism. This Review highlights the central roles of signal transducer and activator of transcription (STAT) proteins, notably STAT3, STAT5, STAT6 and STAT1, in orchestrating the highly dynamic metabolism not only of cancer cells but also of immune cells and adipocytes in the tumour microenvironment. STAT proteins are able to shape distinct metabolic processes that regulate tumour progression and therapy resistance by transducing signals from metabolites, cytokines, growth factors and their receptors; defining genetic programmes that regulate a wide range of molecules involved in orchestration of metabolism in cancer and immune cells; and regulating mitochondrial activity at multiple levels, including energy metabolism and lipid-mediated mitochondrial integrity. Given the central role of STAT proteins in regulation of metabolic states, they are potential therapeutic targets for altering metabolic reprogramming in cancer.
  8. Sci Rep. 2023 Jan 02. 13(1): 18
      Autophagy of damaged mitochondria, called mitophagy, is an important organelle quality control process involved in the pathogenesis of inflammation, cancer, aging, and age-associated diseases. Many of these disorders are associated with altered expression of the inner mitochondrial membrane (IMM) protein Prohibitin 1. The mechanisms whereby dysfunction occurring internally at the IMM and matrix activate events at the outer mitochondrial membrane (OMM) to induce mitophagy are not fully elucidated. Using the gastrointestinal epithelium as a model system highly susceptible to autophagy inhibition, we reveal a specific role of Prohibitin-induced mitophagy in maintaining intestinal homeostasis. We demonstrate that Prohibitin 1 induces mitophagy in response to increased mitochondrial reactive oxygen species (ROS) through binding to mitophagy receptor Nix/Bnip3L and independently of Parkin. Prohibitin 1 is required for ROS-induced Nix localization to mitochondria and maintaining homeostasis of epithelial cells highly susceptible to mitochondrial dysfunction.
  9. J Biol Chem. 2022 Dec 29. pii: S0021-9258(22)01291-1. [Epub ahead of print] 102848
      In eukaryotes carnitine is best known for its ability to shuttle esterified fatty acids across mitochondrial membranes for β-oxidation. It also returns to the cytoplasm, in the form of acetyl-L-carnitine (LAC), some of the resulting acetyl groups for post-translational protein modification and lipid biosynthesis. While dietary LAC supplementation has been clinically investigated, its effects on cellular metabolism are not well understood. To explain how exogenous LAC influences mammalian cell metabolism, we synthesized isotope-labeled forms of LAC and its analogs. In cultures of glucose-limited U87MG glioma cells, exogenous LAC contributed more robustly to intracellular acetyl-CoA pools than did β-hydroxybutyrate, the predominant circulating ketone body in mammals. The fact that most LAC-derived acetyl-CoA is cytosolic is evident from strong labeling of fatty acids in U87MG cells by exogenous 13C2-acetyl-L-carnitine. We found that the addition of d3-acetyl-L-carnitine increases the supply of acetyl-CoA for cytosolic post-translational modifications due to its strong kinetic isotope effect on acetyl-CoA carboxylase, the first committed step in fatty acid biosynthesis. Surprisingly, whereas cytosolic carnitine acetyltransferase (CRAT) is believed to catalyze acetyl group transfer from LAC to Coenzyme A, CRAT-/- U87MG cells were unimpaired in their ability to assimilate exogenous LAC into acetyl-CoA. We identified carnitine octanoyltransferase (CROT) as the key enzyme in this process, implicating a role for peroxisomes in efficient LAC utilization. Our work has opened the door to further biochemical investigations of a new pathway for supplying acetyl-CoA to certain glucose-starved cells.
    Keywords:  acetyl coenzyme A (acetyl‐CoA); acetylcarnitine; cell metabolism; energy metabolism; enzyme turnover; metabolic regulation; mitochondrial metabolism; peroxisome
  10. Sci Adv. 2023 Jan 04. 9(1): eadd3216
      Myopathies secondary to mitochondrial electron transport chain (ETC) dysfunction can result in devastating disease. While the consequences of ETC defects have been extensively studied in culture, little in vivo data are available. Using a mouse model of severe, early-onset mitochondrial myopathy, we characterized the proteomic, transcriptomic, and metabolic characteristics of disease progression. Unexpectedly, ETC dysfunction in muscle results in reduced expression of glycolytic enzymes in our animal model and patient muscle biopsies. The decrease in glycolysis was mediated by loss of constitutive Hif1α signaling, down-regulation of the purine nucleotide cycle enzyme AMPD1, and activation of AMPK. In vivo isotope tracing experiments indicated that myopathic muscle relies on lactate import to supply central carbon metabolites. Inhibition of lactate import reduced steady-state levels of tricarboxylic acid cycle intermediates and compromised the life span of myopathic mice. These data indicate an unexpected mode of metabolic reprogramming in severe mitochondrial myopathy that regulates disease progression.
  11. Mol Cell Biochem. 2023 Jan 06.
      Anthracyclines such as doxorubicin (Dox) are widely used to treat a variety of adult and childhood cancers, however, a major limitation to many of these compounds is their propensity for inducing heart failure. A naturally occurring polyphenolic compound such as Ellagic acid (EA) has been shown by our laboratory to mitigate the cardiotoxic effects of Dox, however, the effects of EA on cancer cell viability have not been established. In this study, we explored the effects of EA alone and in combination with Dox on cancer cell viability and tumorigenesis. Herein, we show that EA induces cell cycle exit and reduces proliferation in colorectal cancer (HCT116) and breast adenocarcinoma cells (MCF7). We show that EA promotes cell cycle exit by a mechanism that inhibits mitochondrial dynamics protein Drp-1. EA treatment of HCT116 and MCF7 cells resulted in a hyperfused mitochondrial morphology that coincided with mitochondrial perturbations including loss of mitochondrial membrane potential, impaired respiratory capacity. Moreover, impaired mitochondrial function was accompanied by a reduction in cell cycle and proliferation markers, CDK1, Ki67, and Cyclin B. This resulted in a reduction in proliferation and widespread death of cancer cells. Furthermore, while Dox treatment alone promoted cell death in both HCT116 and MCF7 cancer cell lines, EA treatment lowered the effective dose of Dox to promote cell death. Hence, the findings of the present study reveal a previously unreported anti-tumor property of EA that impinges on mitochondrial dynamics protein, Drp-1 which is crucial for cell division and tumorigenesis. The ability of EA to lower the therapeutic threshold of Dox for inhibiting cancer cell growth may prove beneficial in reducing cardiotoxicity in cancer patients undergoing anthracycline therapy.
    Keywords:  CDK1; Cancer proliferation; Drp-1; Ellagic Acid; Mitochondrial dynamics
  12. Cancer Res. 2023 Jan 03. pii: CAN-22-2045. [Epub ahead of print]
      Pancreatic ductal adenocarcinoma (PDAC) exhibits severe hypoxia, which is associated with chemoresistance and worse patient outcome. It has been reported that hypoxia induces metabolic reprogramming in cancer cells. However, it is not well known whether metabolic reprogramming contributes to hypoxia. Here, we established that increased glutamine catabolism is a fundamental mechanism inducing hypoxia, and thus chemoresistance, in PDAC cells. An extracellular matrix (ECM) component-based in vitro 3D cell printing model with patient-derived PDAC cells that recapitulates the hypoxic status in PDAC tumors showed that chemoresistant PDAC cells exhibit markedly enhanced glutamine catabolism compared to chemoresponsive PDAC cells. The augmented glutamine metabolic flux increased the oxygen consumption rate via mitochondrial oxidative phosphorylation (OXPHOS), promoting hypoxia and hypoxia-induced chemoresistance. Targeting glutaminolysis relieved hypoxia and improved chemotherapy efficacy in vitro and in vivo. This work suggests that targeting the glutaminolysis-OXPHOS-hypoxia axis is a novel therapeutic target for treating patients with chemoresistant PDAC.
  13. Structure. 2022 Dec 15. pii: S0969-2126(22)00488-9. [Epub ahead of print]
      The mitochondrial ClpP protease is responsible for mitochondrial protein quality control through specific degradation of proteins involved in several metabolic processes. ClpP overexpression is also required in many cancer cells to eliminate reactive oxygen species (ROS)-damaged proteins and to sustain oncogenesis. Targeting ClpP to dysregulate its function using small-molecule agonists is a recent strategy in cancer therapy. Here, we synthesized imipridone-derived compounds and related chemicals, which we characterized using biochemical, biophysical, and cellular studies. Using X-ray crystallography, we found that these compounds have enhanced binding affinities due to their greater shape and charge complementarity with the surface hydrophobic pockets of ClpP. N-terminome profiling of cancer cells upon treatment with one of these compounds revealed the global proteomic changes that arise and identified the structural motifs preferred for protein cleavage by compound-activated ClpP. Together, our studies provide the structural and molecular basis by which dysregulated ClpP affects cancer cell viability and proliferation.
    Keywords:  ClpP agonist; ClpP protease; HYTANE mass spectrometry; N-terminome; TR compounds; X-ray crystallography; cancer; drug design; imipridones; mitochondria
  14. Adv Ther (Weinh). 2022 Oct;pii: 2200021. [Epub ahead of print]5(10):
      Pancreatic ductal adenocarcinoma (PDAC) is a disease with no effective therapeutics. We have developed a novel targeted therapy drug consisting of a tumor-targeting ligand, near-infrared (NIR) organic heptamethine carbocyanine dye (HMCD), and HMG-CoA inhibitor simvastatin (SIM), and assessed its efficacy in PDAC. PDAC cell specific targeting of DZ-SIM was measured by determining the fluorescence in cells and animals. Mitochondrial bioenergetics and functions were measured by Seahorse and flow cytometry, respectively. Apoptosis was assessed by DNA fragmentation, AnnexinV/Propidium Iodide staining, and TUNEL. Markers of cell invasion, epithelial-to-mesenchymal transition, and cancer stemness were measured. The effect of DZ-SIM on survival, tumor growth and metastasis was measured in the Krasþ/LSLG12D;Trp53þ/LSLR172H;Pdx-1-Cre (KPC) transgenic mice and in syngeneic and subcutaneous PDAC models. NIR fluorescence imaging showed specific localization of DZ-SIM to cancer, but not to normal cells and tissues. DZ-SIM significantly inhibited tumor growth and re-sensitized therapeutically resistant PDAC cells to conventional therapies. DZ-SIM killed cancer cells through unique pathways involving decreasing mitochondrial bioenergetics, including oxygen consumption and ATP production, and increasing ROS production. Mitochondrial depletion prevented the effect of DZ-SIM. Administration of DZ-SIM in 3 PDAC animal models resulted in a marked increase in survival and a decrease in tumor growth and metastasis.
    Keywords:  DZ-SIM; mitochondria; pancreatic cancer
  15. Cancer Biol Ther. 2023 Dec 31. 24(1): 20-32
      The possible anticancer activity of combination (M + E + F) of metformin (M), efavirenz (E), and fluoxetine (F) was investigated in normal HDF cells and HCT116 human colon cancer cells. Metformin increased cellular FOXO3a, p-FOXO3a, AMPK, p-AMPK, and MnSOD levels in HDFs but not in HCT116 cells. Cellular ATP level was decreased only in HDFs by metformin. Metformin increased ROS level only in HCT116 cells. Transfection of si-FOXO3a into HCT116 reversed the metformin-induced cellular ROS induction, indicating that FOXO3a/MnSOD is the key regulator for cellular ROS level. Viability readout with M, E, and F alone decreased slightly, but the combination of three drugs dramatically decreased cell survival in HCT116, A549, and SK-Hep-1 cancer cells but not in HDF cells. ROS levels in HCT116 cells were massively increased by M + E + F combination, but not in HDF cells. Cell cycle analysis showed that of M + E + F combination caused cell death only in HCT116 cells. The combination of M + E + F reduced synergistically mitochondrial membrane potential and mitochondrial electron transport chain complex I and III activities in HCT116 cells when compared with individual treatments. Western blot analysis indicated that DNA damage, apoptosis, autophagy, and necroptosis-realated factors increased in M + E + F-treated HCT116 cells. Oral administration with M + E + F combination for 3 weeks caused dramatic reductions in tumor volume and weight in HCT116 xenograft model of nude mice when compared with untreated ones. Our results suggest that M + E + F have profound anticancer activity both in vitro and in vivo via a cancer cell-specific ROS amplification (CASRA) through ROS-induced DNA damage, apoptosis, autophagy, and necroptosis.
    Keywords:  FOXO3a; MnSOD; ROS amplification; anticancer activity; apoptosis/necroptosis/autophagy; cancer cell-specific; metformin/efavirenz/fluoxetine; mitochondrial complex I and III
  16. Nat Commun. 2023 Jan 03. 14(1): 30
      The mitochondrial translation machinery highly diverged from its bacterial counterpart. This includes deviation from the universal genetic code, with AGA and AGG codons lacking cognate tRNAs in human mitochondria. The locations of these codons at the end of COX1 and ND6 open reading frames, respectively, suggest they might function as stop codons. However, while the canonical stop codons UAA and UAG are known to be recognized by mtRF1a, the release mechanism at AGA and AGG codons remains a debated issue. Here, we show that upon the loss of another member of the mitochondrial release factor family, mtRF1, mitoribosomes accumulate specifically at AGA and AGG codons. Stalling of mitoribosomes alters COX1 transcript and protein levels, but not ND6 synthesis. In addition, using an in vitro reconstituted mitochondrial translation system, we demonstrate the specific peptide release activity of mtRF1 at the AGA and AGG codons. Together, our results reveal the role of mtRF1 in translation termination at non-canonical stop codons in mitochondria.
  17. J Biol Chem. 2023 Jan 02. pii: S0021-9258(22)01306-0. [Epub ahead of print] 102863
      The pro-apoptotic BH3-only endoplasmic reticulum (ER) resident protein BIK, positively regulates mitochondrial outer membrane permeabilization (MOMP), the point-of-no-return in apoptosis. It is generally accepted that BIK functions at a distance from mitochondria by binding and sequestering anti-apoptotic proteins at the ER thereby promoting ER calcium release. Although BIK is predominantly localized to the ER, we detect by FLIM-FRET microscopy, BH3 region-dependent direct binding between BIK and mitochondria-localized chimeric mutants of the anti-apoptotic proteins BCL-XL and BCL-2 in both BMK and MCF-7 cells. Direct binding was accompanied by cell-type specific differential relocalization in response to co-expression of either BIK or one of its target binding partners, BCL-XL, when co-expressed in cells. In BMK cells with genetic deletion of both BAX and BAK (BMK-DKO) our data suggest a fraction of BIK protein moves towards mitochondria in response to the expression of a mitochondria-localized BCL-XL mutant. In contrast, in MCF-7 cells our data suggest BIK is localized at both ER and mitochondria-associated endoplasmic reticulum membranes (MAMs) and binds to the mitochondria-localized BCL-XL mutant via relocalization of BCL-XL to ER and MAMs. Rather than functioning at a distance, our data suggest BIK initiates MOMP via direct interactions with ER and mitochondria-localized anti-apoptotic proteins, that occur via ER-mitochondria contact sites, and/or by relocalization of either BIK or anti-apoptotic proteins in cells.
    Keywords:  BCL-2 family; BCL-2 interacting killer; BIK; FLIM-FRET; apoptosis; subcellular localization fluorescence lifetime imaging microscopy
  18. Cell Rep. 2022 Dec 23. pii: S2211-1247(22)01798-3. [Epub ahead of print] 111899
      Endoplasmic reticulum (ER) homeostasis requires molecular regulators that tailor mitochondrial bioenergetics to the needs of protein folding. For instance, calnexin maintains mitochondria metabolism and mitochondria-ER contacts (MERCs) through reactive oxygen species (ROS) from NADPH oxidase 4 (NOX4). However, induction of ER stress requires a quick molecular rewiring of mitochondria to adapt to new energy needs. This machinery is not characterized. We now show that the oxidoreductase ERO1⍺ covalently interacts with protein kinase RNA-like ER kinase (PERK) upon treatment with tunicamycin. The PERK-ERO1⍺ interaction requires the C-terminal active site of ERO1⍺ and cysteine 216 of PERK. Moreover, we show that the PERK-ERO1⍺ complex promotes oxidization of MERC proteins and controls mitochondrial dynamics. Using proteinaceous probes, we determined that these functions improve ER-mitochondria Ca2+ flux to maintain bioenergetics in both organelles, while limiting oxidative stress. Therefore, the PERK-ERO1⍺ complex is a key molecular machinery that allows quick metabolic adaptation to ER stress.
    Keywords:  CP: Metabolism; CP: Molecular biology; ER; ER stress; ERO1; MAMs; MERCs; PERK; bioenergetics; endoplasmic reticulum; mitochondria; mitochondria-associated membranes; mitochondria-endoplasmic reticulum contacts; oxidoreductase
  19. Arch Pathol Lab Med. 2023 Jan 05.
      CONTEXT.—: Mitochondria and mitochondrial DNA have been suggested to play a role in cancer initiation and progression. Knowledge of mitochondrial DNA could provide a breakthrough to advance cancer management.OBJECTIVE.—: To identify the mitochondrial DNA landscape in non-small cell lung carcinoma.
    DESIGN.—: The adenocarcinoma set consisted of 365 pairs of adenocarcinomas and normal lung tissues, whereas the metastasis set included 12 primary non-small cell carcinomas, 15 metastatic tumors, and their normal counterparts. Tumor-specific somatic variants were identified, and if a variant showed heteroplasmy, the proportion of minor alleles was evaluated. Variants with greater than 10% change in allele frequency between tumor and normal pairs were identified as "heteroplasmic shifts."
    RESULTS.—: Tumor-specific variants appeared throughout the whole mitochondrial genome, without a common hot spot. Distinct variant profiles were seen in 289 (79.18%) of all individual adenocarcinomas. The presence of a unique profile and the number and loading of heteroplasmic shifts in tumors increased with higher stage or lymph node metastasis, and were related to shorter survival. In the metastasis set, the primary tumor variants were generally found in metastatic tumors.
    CONCLUSIONS.—: This study shows that somatic mitochondrial DNA mutations present with diverse locations and unique profiles in each individual tumor, implying their clinicopathologic utility.
  20. Nat Commun. 2023 Jan 05. 14(1): 77
      Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome associated with germline TP53 pathogenic variants. Here, we perform whole-genome sequence (WGS) analysis of tumors from 22 patients with TP53 germline pathogenic variants. We observe somatic mutations affecting Wnt, PI3K/AKT signaling, epigenetic modifiers and homologous recombination genes as well as mutational signatures associated with prior chemotherapy. We identify near-ubiquitous early loss of heterozygosity of TP53, with gain of the mutant allele. This occurs earlier in these tumors compared to tumors with somatic TP53 mutations, suggesting the timing of this mark may distinguish germline from somatic TP53 mutations. Phylogenetic trees of tumor evolution, reconstructed from bulk and multi-region WGS, reveal that LFS tumors exhibit comparatively limited heterogeneity. Overall, our study delineates early copy number gains of mutant TP53 as a characteristic mutational process in LFS tumorigenesis, likely arising years prior to tumor diagnosis.
  21. Cell Death Discov. 2023 Jan 02. 9(1): 1
      Small-cell lung cancer (SCLC) is an aggressive malignancy with limited therapeutic options. The dismal prognosis in SCLC is in part associated with an upregulation of BCL-2 family anti-apoptotic proteins, including BCL-XL and MCL-1. Unfortunately, the currently available inhibitors of BCL-2 family anti-apoptotic proteins, except BCL-2 inhibitors, are not clinically relevant because of various on-target toxicities. We, therefore, aimed to develop an effective and safe strategy targeting these anti-apoptotic proteins with DT2216 (our platelet-sparing BCL-XL degrader) and AZD8055 (an mTOR inhibitor) to avoid associated on-target toxicities while synergistically optimizing tumor response. Through BH3 mimetic screening, we identified a subset of SCLC cell lines that is co-dependent on BCL-XL and MCL-1. After screening inhibitors of selected tumorigenic pathways, we found that AZD8055 selectively downregulates MCL-1 in SCLC cells and its combination with DT2216 synergistically killed BCL-XL/MCL-1 co-dependent SCLC cells, but not normal cells. Mechanistically, the combination caused BCL-XL degradation and suppression of MCL-1 expression, and thus disrupted MCL-1 interaction with BIM leading to an enhanced apoptotic induction. In vivo, the DT2216 + AZD8055 combination significantly inhibited the growth of cell line-derived and patient-derived xenografts and reduced tumor burden accompanied by increased survival in a genetically engineered mouse model of SCLC without causing appreciable thrombocytopenia or other normal tissue injuries. Thus, these preclinical findings lay a strong foundation for future clinical studies to test DT2216 + mTOR inhibitor combinations in a subset of SCLC patients whose tumors are co-driven by BCL-XL and MCL-1.
  22. Curr Res Pharmacol Drug Discov. 2023 ;4 100148
      We study for the first time whether triphenylphosphonium (TPP) moiety can improve cellular delivery and redox properties of amphipathic cationic peptides based on YRFK/YrFK cell-penetrating and cytoprotective motif. TPP moiety was found to increase reducing activity of both stereoisomeric peptides in solution and on electrode surface in association with TPP-mediated intramolecular interactions. Among TPP-conjugated peptides, newly synthesized TPP3-YrFK featured both increased antioxidant efficacy and proteolytic resistance. TPP-conjugated peptides preferably mitigated endogenic ROS in mitochondria and cytoplasm of model glioblastoma cells with increased oxidative status. This anti-ROS effect was accompanied by mild reversible decrease of reduced glutathione level in the cells with relatively weak change in glutathione redox forms ratio. Such low interference with cell redox status is in accordance with non-cytotoxic nature of the compounds. Intracellular concentrations of label-free peptides were analyzed by LC-MS/MS, which showed substantial TPP-promoted penetration of YrFK motif across cell plasma membrane. However, according to ΔΨm analysis, TPP moiety did not profoundly enhance peptide interaction with mitochondrial inner membrane. Our study clarifies the role of TPP moiety in cellular delivery of amphipathic cationic oligopeptides. The results suggest TPP moiety as a multi-functional modifier for the oligopeptides which is capable of improving cellular pharmacokinetics and antioxidant activity as well as targeting increased ROS levels. The results encourage further investigation of TPP3-YrFK as a peptide antioxidant with multiple benefits.
    Keywords:  ABTS, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid); Amphipathic cationic peptides; CCCP, carbonyl cyanide 3-chlorophenylhydrazone; CD, circular dichroism; Cellular pharmacokinetics; DCFDA, 2′,7′-dichlorofluorescin diacetate; GSH, reduced glutathione; HBSS, Hank's balanced salt solution; Intramolecular interaction; LC–MS/MS, liquid chromatography tandem mass-spectrometry; MCB, monochlorobimane; MRM, multiple reaction monitoring; ROS targeting; ROS, reactive oxygen species; Redox activity; SPPS, solid-phase peptide synthesis; TPP, triphenylphosphonium; Triphenylphosphonium cation; aa, amino acid
  23. Nat Metab. 2023 Jan 02.
      Enhanced glycolysis and accumulation of lactate is a common feature in various types of cancer. Intracellular lactate drives a recently described type of posttranslational modification, lysine lactylation (Kla), on core histones. However, the impact of lactylation on biological processes of tumour cells remains largely unknown. Here we show a global lactylome profiling on a prospectively collected hepatitis B virus-related hepatocellular carcinoma (HCC) cohort. Integrative lactylome and proteome analysis of the tumours and adjacent livers identifies 9,275 Kla sites, with 9,256 sites on non-histone proteins, indicating that Kla is a prevalent modification beyond histone proteins and transcriptional regulation. Notably, Kla preferentially affects enzymes involved in metabolic pathways, including the tricarboxylic acid cycle, and carbohydrate, amino acid, fatty acid and nucleotide metabolism. We further verify that lactylation at K28 inhibits the function of adenylate kinase 2, facilitating the proliferation and metastasis of HCC cells. Our study therefore reveals that Kla plays an important role in regulating cellular metabolism and may contribute to HCC progression.