bims-mibica 2024-01-14 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2024–01–14
38 papers selected by
Kelsey Fisher-Wellman, East Carolina University

Accessory subunit NDUFB4 participates in mitochondrial complex I supercomplex formation.
Targeting cancer and immune cell metabolism with the complex I inhibitors metformin and IACS-010759.
The nonessential amino acid cysteine is required to prevent ferroptosis in acute myeloid leukemia.
Mutational profiling of mitochondrial DNA reveals an epithelial ovarian cancer-specific evolutionary pattern contributing to high oxidative metabolism.
Hexamethylene amiloride synergizes with venetoclax to induce lysosome-dependent cell death in acute myeloid leukemia.
eIF5A controls mitoprotein import by relieving ribosome stalling at the TIM50 translocase mRNA.
Effects of aging on glucose and lipid metabolism in mice.
METTL17 is an Fe-S cluster checkpoint for mitochondrial translation.
p66ShcA promotes malignant breast cancer phenotypes by alleviating energetic and oxidative stress.
Systems-level analyses dissociate genetic regulators of reactive oxygen species and energy production.
Sulfur Amino Acid Restriction alters mitochondrial function depending on tissue, sex, and Methionine sulfoxide reductase A (MsrA) status.
Ovarian cancer cells regulate their mitochondrial content and high mitochondrial content is associated with a poor prognosis.
MARCH5-mediated downregulation of ACC2 promotes fatty acid oxidation and tumor progression in ovarian cancer.
Monosomy 7/del(7q) Cause Sensitivity to Inhibitors of Nicotinamide Phosphoribosyltransferase in Acute Myeloid Leukemia.
NF1 deficiency drives metabolic reprogramming in ER+ breast cancer.
UCP2 and pancreatic cancer: conscious uncoupling for therapeutic effect.
Propionate promotes ferroptosis and apoptosis through mitophagy and ACSL4-mediated ferroptosis elicits anti-leukemia immunity.
Identification of TMEM126A as OXA1L-interacting protein reveals cotranslational quality control in mitochondria.
The mitochondrial genome-encoded peptide MOTS-c interacts with Bcl-2 to alleviate nonalcoholic steatohepatitis progression.
Huntington disease affects mitochondrial network dynamics predisposing to pathogenic mtDNA mutations.
Peroxisomal β-oxidation enzyme, DECR2, regulates lipid metabolism and promotes treatment resistance in advanced prostate cancer.
Hypoxia and intra-complex genetic suppressors rescue complex I mutants by a shared mechanism.
Sonrotoclax overcomes BCL2 G101V mutation-induced venetoclax resistance in preclinical models of hematologic malignancy.
Inhibition of mitochondrial function by approved drugs overcomes nasopharyngeal carcinoma chemoresistance.
A mitochondria-targeting dihydroartemisinin derivative as a reactive oxygen species -based immunogenic cell death inducer.
The E3 ligase HUWE1 increases the sensitivity of CRC to oxaliplatin through TOMM20 degradation.
Disordered-to-ordered transitions in assembly factors allow the complex II catalytic subunit to switch binding partners.
Metabolite profiling of human renal cell carcinoma reveals tissue-origin dominance in nutrient availability.
Antitumour effect of the mitochondrial complex III inhibitor Atovaquone in combination with anti-PD-L1 therapy in mouse cancer models.
CircPTEN-MT from PTEN regulates mitochondrial energy metabolism.
High Mitochondrial Protein Expression as a Potential Predictor of Relapse Risk in Acute Myeloid Leukemia Patients with the Monocytic FAB Subtypes M4 and M5.
Glyoxylate reductase: Definitive identification in human liver mitochondria, its importance for the compartment-specific detoxification of glyoxylate.
Nicotinamide mononucleotide induces autophagy and ferroptosis via AMPK/mTOR pathway in hepatocellular carcinoma.
The Combined Treatment with Ketogenic Diet and Metformin Slows Tumor Growth in Two Mouse Models of Triple Negative Breast Cancer.
Reprogramming of pyrimidine nucleotide metabolism supports vigorous cell proliferation of normal and malignant T cells.
Bakuchiol targets mitochondrial proteins, prohibitins and voltage-dependent anion channels: new insights into developing anti-viral agents.
Acute endoplasmic reticulum stress-induced mitochondria respiratory chain damage: The role of activated calpains.
Mitofusin 1 silencing decreases the senescent associated secretory phenotype, promotes immune cell recruitment and delays melanoma tumor growth after chemotherapy.

J Biol Chem. 2024 Jan 08. pii: S0021-9258(24)00002-4. [Epub ahead of print] 105626

Accessory subunit NDUFB4 participates in mitochondrial complex I supercomplex formation.

Gaganvir Parmar, Claire Fong-McMaster, Chantal Pileggi, David A Patten, Alexanne Cuillerier, Stephanie Myers, Ying Wang, Siegfried Hekimi, Miroslava Cuperlovic-Culf, Mary-Ellen Harper.

  Mitochondrial electron transport chain (ETC) complexes organize into supramolecular structures called respiratory supercomplexes (SCs). The role of respiratory SC remains largely unconfirmed despite evidence supporting their necessity for mitochondrial respiratory function. The mechanisms underlying the formation of the I1III2IV1 "respirasome" SC are also not fully understood, further limiting insights into these processes in physiology and diseases, including neurodegeneration and metabolic syndromes. NDUFB4 is a complex I accessory subunit that contains residues that interact with the subunit UQCRC1 from complex III, suggesting that NDUFB4 is integral for I1III2IV1 respirasome integrity. Here, we introduced specific point mutations to Asn24 (N24) and Arg30 (R30) residues on NDUFB4 to decipher the role of I1III2-containing respiratory SCs in cellular metabolism while minimizing the functional consequences to complex I assembly. Our results demonstrate that NDUFB4 point mutations N24A and R30A impair I1III2IV1 respirasome assembly and reduce mitochondrial respiratory flux. Steady-state metabolomics also revealed a global decrease in TCA cycle metabolites, affecting NADH-generating substrates. Taken together, our findings highlight an integral role of NDUFB4 in respirasome assembly and demonstrate the functional significance of SCs in regulating mammalian cell bioenergetics.

Keywords:  Mitochondria; NDUFB4; electron transport chain; oxidative phosphorylation; respirasome; steady-state metabolomics; supercomplexes

DOI:  https://doi.org/10.1016/j.jbc.2024.105626
Mol Oncol. 2024 Jan 12.

Targeting cancer and immune cell metabolism with the complex I inhibitors metformin and IACS-010759.

Marc Pujalte-Martin, Amine Belaïd, Simon Bost, Michel Kahi, Pascal Peraldi, Matthieu Rouleau, Nathalie M Mazure, Frédéric Bost.

  Metformin and IACS-010759 are two distinct antimetabolic agents. Metformin, an established antidiabetic drug, mildly inhibits mitochondrial complex I, while IACS-010759 is a new potent mitochondrial complex I inhibitor. Mitochondria is pivotal in the energy metabolism of cells by providing adenosine triphosphate through oxidative phosphorylation (OXPHOS). Hence, mitochondrial metabolism and OXPHOS become a vulnerability when targeted in cancer cells. Both drugs have promising antitumoral effects in diverse cancers, supported by preclinical in vitro and in vivo studies. We present evidence of their direct impact on cancer cells and their immunomodulatory effects. In clinical studies, while observational epidemiologic studies on metformin were encouraging, actual trial results were not as expected. However, IACS-01075 exhibited major adverse effects, thereby causing a metabolic shift to glycolysis and elevated lactic acid concentrations. Therefore, the future outlook for these two drugs depends on preventive clinical trials for metformin and investigations into the plausible toxic effects on normal cells for IACS-01075.

Keywords:  IACS-010759; cancer; clinical trial; immunometabolism; metformin; microenvironment

DOI:  https://doi.org/10.1002/1878-0261.13583
Blood Adv. 2024 Jan 09. 8(1): 56-69

The nonessential amino acid cysteine is required to prevent ferroptosis in acute myeloid leukemia.

Alan Cunningham, Lieve L Oudejans, Marjan Geugien, Diego Antonio Pereira-Martins, Albertus T J Wierenga, Ayşegül Erdem, Dominique Sternadt, Gerwin Huls, Jan Jacob Schuringa.

ABSTRACT: Cysteine is a nonessential amino acid required for protein synthesis, the generation of the antioxidant glutathione, and for synthesizing the nonproteinogenic amino acid taurine. Here, we highlight the broad sensitivity of leukemic stem and progenitor cells to cysteine depletion. By CRISPR/CRISPR-associated protein 9-mediated knockout of cystathionine-γ-lyase, the cystathionine-to-cysteine converting enzyme, and by metabolite supplementation studies upstream of cysteine, we functionally prove that cysteine is not synthesized from methionine in acute myeloid leukemia (AML) cells. Therefore, although perhaps nutritionally nonessential, cysteine must be imported for survival of these specific cell types. Depletion of cyst(e)ine increased reactive oxygen species (ROS) levels, and cell death was induced predominantly as a consequence of glutathione deprivation. nicotinamide adenine dinucleotide phosphate hydrogen oxidase inhibition strongly rescued viability after cysteine depletion, highlighting this as an important source of ROS in AML. ROS-induced cell death was mediated via ferroptosis, and inhibition of glutathione peroxidase 4 (GPX4), which functions in reducing lipid peroxides, was also highly toxic. We therefore propose that GPX4 is likely key in mediating the antioxidant activity of glutathione. In line, inhibition of the ROS scavenger thioredoxin reductase with auranofin also impaired cell viability, whereby we find that oxidative phosphorylation-driven AML subtypes, in particular, are highly dependent on thioredoxin-mediated protection against ferroptosis. Although inhibition of the cystine-glutamine antiporter by sulfasalazine was ineffective as a monotherapy, its combination with L-buthionine-sulfoximine (BSO) further improved AML ferroptosis induction. We propose the combination of either sulfasalazine or antioxidant machinery inhibitors along with ROS inducers such as BSO or chemotherapy for further preclinical testing.

DOI: https://doi.org/10.1182/bloodadvances.2023010786
Clin Transl Med. 2024 Jan;14(1): e1523

Mutational profiling of mitochondrial DNA reveals an epithelial ovarian cancer-specific evolutionary pattern contributing to high oxidative metabolism.

Fanfan Xie, Wenjie Guo, Xingguo Wang, Kaixiang Zhou, Shanshan Guo, Yang Liu, Tianlei Sun, Shengjing Li, Zhiyang Xu, Qing Yuan, Huanqin Zhang, Xiwen Gu, Jinliang Xing, Shujuan Liu.

   BACKGROUND: Epithelial ovarian cancer (EOC) heavily relies on oxidative phosphorylation (OXPHOS) and exhibits distinct mitochondrial metabolic reprogramming. Up to now, the evolutionary pattern of somatic mitochondrial DNA (mtDNA) mutations in EOC tissues and their potential roles in metabolic remodelling have not been systematically elucidated.
METHODS: Based on a large somatic mtDNA mutation dataset from private and public EOC cohorts (239 and 118 patients, respectively), we most comprehensively characterised the EOC-specific evolutionary pattern of mtDNA mutations and investigated its biological implication.
RESULTS: Mutational profiling revealed that the mitochondrial genome of EOC tissues was highly unstable compared with non-cancerous ovary tissues. Furthermore, our data indicated the delayed heteroplasmy accumulation of mtDNA control region (mtCTR) mutations and near-complete absence of mtCTR non-hypervariable segment (non-HVS) mutations in EOC tissues, which is consistent with stringent negative selection against mtCTR mutation. Additionally, we observed a bidirectional and region-specific evolutionary pattern of mtDNA coding region mutations, manifested as significant negative selection against mutations in complex V (ATP6/ATP8) and tRNA loop regions, and potential positive selection on mutations in complex III (MT-CYB). Meanwhile, EOC tissues showed higher mitochondrial biogenesis compared with non-cancerous ovary tissues. Further analysis revealed the significant association between mtDNA mutations and both mitochondrial biogenesis and overall survival of EOC patients.
CONCLUSIONS: Our study presents a comprehensive delineation of EOC-specific evolutionary patterns of mtDNA mutations that aligned well with the specific mitochondrial metabolic remodelling, conferring novel insights into the functional roles of mtDNA mutations in EOC tumourigenesis and progression.

Keywords:  epithelial ovarian cancer; evolutionary selection; metabolic remodelling; mitochondrial DNA; somatic mutations

DOI:  https://doi.org/10.1002/ctm2.1523
iScience. 2024 Jan 19. 27(1): 108691

Hexamethylene amiloride synergizes with venetoclax to induce lysosome-dependent cell death in acute myeloid leukemia.

Xinya Jiang, Kexiu Huang, Xiaofan Sun, Yue Li, Lei Hua, Fangshu Liu, Rui Huang, Juan Du, Hui Zeng.

  Tumors maintain an alkaline intracellular environment to enable rapid growth. The proton exporter NHE1 participates in maintenance of this pH gradient. However, whether targeting NHE1 could inhibit the growth of tumor cells remains unknown. Here, we report that the NHE1 inhibitor Hexamethylene amiloride (HA) efficiently suppresses the growth of AML cell lines. Moreover, HA combined with venetoclax synergized to efficiently inhibit the growth of AML cells. Interestingly, lysosomes are the main contributors to the synergism of HA and venetoclax in inhibiting AML cells. Most importantly, the combination of HA and venetoclax also had prominent anti-leukemia effects in both xenograft models and bone marrow samples from AML patients. In summary, our results provide evidence that the NHE1 inhibitor HA or its combination with venetoclax efficiently inhibits the growth of AML in vitro and in vivo.

Keywords:  Cancer; Cell biology; Cellular toxicology; Molecular medicine

DOI:  https://doi.org/10.1016/j.isci.2023.108691
bioRxiv. 2023 Dec 19. pii: 2023.12.19.572290. [Epub ahead of print]

eIF5A controls mitoprotein import by relieving ribosome stalling at the TIM50 translocase mRNA.

Marina Barba-Aliaga, Vanessa Bernal, Cynthia Rong, Brian M Zid, Paula Alepuz.

The efficient import of nuclear-encoded proteins into mitochondria is crucial for proper mitochondrial function. The conserved translation factor eIF5A is primarily known as an elongation factor which binds ribosomes to alleviate ribosome stalling at sequences encoding polyprolines or combinations of proline with glycine and charged amino acids. eIF5A is known to impact the mitochondrial function across a variety of species although the precise molecular mechanism underlying this impact remains unclear. We found that depletion of eIF5A in yeast drives reduced translation and levels of TCA cycle and oxidative phosphorylation proteins. We further found that loss of eIF5A leads to the accumulation of mitoprotein precursors in the cytosol as well as to the induction of a mitochondrial import stress response. Here we identify an essential polyproline-containing protein as a direct eIF5A target for translation: the mitochondrial inner membrane protein Tim50, which is the receptor sub-unit of the TIM23 translocase complex. We show how eIF5A directly controls mitochondrial protein import through the alleviation of ribosome stalling along TIM50 mRNA at the mitochondrial surface. Removal of the polyprolines from Tim50 rescues the mitochondrial import stress response, as well as the translation of oxidative phosphorylation reporter genes in an eIF5A loss of function. Overall, our findings elucidate how eIF5A impacts the mitochondrial function by reducing ribosome stalling and facilitating protein translation, thereby positively impacting the mitochondrial import process.

DOI: https://doi.org/10.1101/2023.12.19.572290
bioRxiv. 2023 Dec 18. pii: 2023.12.17.572088. [Epub ahead of print]

Effects of aging on glucose and lipid metabolism in mice.

Evan C Lien, Ngoc Vu, Anna M Westermark, Laura V Danai, Allison N Lau, Yetiş Gültekin, Matthew A Kukurugya, Bryson D Bennett, Matthew G Vander Heiden.

Aging is accompanied by multiple molecular changes that contribute to aging-associated pathologies, such as accumulation of cellular damage and mitochondrial dysfunction. Tissue metabolism can also change with age, in part because mitochondria are central to cellular metabolism. Moreover, the co-factor NAD+, which is reported to decline across multiple tissue types during aging, plays a central role in metabolic pathways such as glycolysis, the tricarboxylic acid cycle, and the oxidative synthesis of nucleotides, amino acids, and lipids. To further characterize how tissue metabolism changes with age, we intravenously infused [U-13C]-glucose into young and old C57BL/6J, WSB/EiJ, and Diversity Outbred mice to trace glucose fate into downstream metabolites within plasma, liver, gastrocnemius muscle, and brain tissues. We found that glucose incorporation into central carbon and amino acid metabolism was robust during healthy aging across these different strains of mice. We also observed that levels of NAD+, NADH, and the NAD+/NADH ratio were unchanged in these tissues with healthy aging. However, aging tissues, particularly brain, exhibited evidence of up-regulated fatty acid and sphingolipid metabolism reactions that regenerate NAD+ from NADH. Because mitochondrial respiration, a major source of NAD+ regeneration, is reported to decline with age, our data supports a model where NAD+-generating lipid metabolism reactions may buffer against changes in NAD+/NADH during healthy aging.

DOI: https://doi.org/10.1101/2023.12.17.572088
Mol Cell. 2024 Jan 04. pii: S1097-2765(23)01035-3. [Epub ahead of print]

METTL17 is an Fe-S cluster checkpoint for mitochondrial translation.

Tslil Ast, Yuzuru Itoh, Shayan Sadre, Jason G McCoy, Gil Namkoong, Jordan C Wengrod, Ivan Chicherin, Pallavi R Joshi, Piotr Kamenski, Daniel L M Suess, Alexey Amunts, Vamsi K Mootha.

  Friedreich's ataxia (FA) is a debilitating, multisystemic disease caused by the depletion of frataxin (FXN), a mitochondrial iron-sulfur (Fe-S) cluster biogenesis factor. To understand the cellular pathogenesis of FA, we performed quantitative proteomics in FXN-deficient human cells. Nearly every annotated Fe-S cluster-containing protein was depleted, indicating that as a rule, cluster binding confers stability to Fe-S proteins. We also observed depletion of a small mitoribosomal assembly factor METTL17 and evidence of impaired mitochondrial translation. Using comparative sequence analysis, mutagenesis, biochemistry, and cryoelectron microscopy, we show that METTL17 binds to the mitoribosomal small subunit during late assembly and harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability. METTL17 overexpression rescued the mitochondrial translation and bioenergetic defects, but not the cellular growth, of FXN-depleted cells. These findings suggest that METTL17 acts as an Fe-S cluster checkpoint, promoting translation of Fe-S cluster-rich oxidative phosphorylation (OXPHOS) proteins only when Fe-S cofactors are replete.

Keywords:  FA; Fe-S cluster; Friedreich’s ataxia; METTL17; frataxin; mitochondria; mitoribosome

DOI:  https://doi.org/10.1016/j.molcel.2023.12.016
Redox Biol. 2024 Jan 05. pii: S2213-2317(24)00004-1. [Epub ahead of print]70 103028

p66ShcA promotes malignant breast cancer phenotypes by alleviating energetic and oxidative stress.

Kyle Lewis, Rachel La Selva, Elias Maldonado, Matthew G Annis, Ouafa Najyb, Eduardo Cepeda Cañedo, Stephanie Totten, Steven Hébert, Valérie Sabourin, Caitlynn Mirabelli, Emma Ciccolini, Camille Lehuédé, Luc Choinière, Mariana Russo, Daina Avizonis, Morag Park, Julie St-Pierre, Claudia L Kleinman, Peter M Siegel, Josie Ursini-Siegel.

  Significant efforts have focused on identifying targetable genetic drivers that support the growth of solid tumors and/or increase metastatic ability. During tumor development and progression to metastatic disease, physiological and pharmacological selective pressures influence parallel adaptive strategies within cancer cell sub-populations. Such adaptations allow cancer cells to withstand these stressful microenvironments. This Darwinian model of stress adaptation often prevents durable clinical responses and influences the emergence of aggressive cancers with increased metastatic fitness. However, the mechanisms contributing to such adaptive stress responses are poorly understood. We now demonstrate that the p66ShcA redox protein, itself a ROS inducer, is essential for survival in response to physiological stressors, including anchorage independence and nutrient deprivation, in the context of poor outcome breast cancers. Mechanistically, we show that p66ShcA promotes both glucose and glutamine metabolic reprogramming in breast cancer cells, to increase their capacity to engage catabolic metabolism and support glutathione synthesis. In doing so, chronic p66ShcA exposure contributes to adaptive stress responses, providing breast cancer cells with sufficient ATP and redox balance needed to withstand such transient stressed states. Our studies demonstrate that p66ShcA functionally contributes to the maintenance of aggressive phenotypes and the emergence of metastatic disease by forcing breast tumors to adapt to chronic and moderately elevated levels of oxidative stress.

Keywords:  Anoikis; Breast cancer; Glutathione; Metabolic plasticity; Oxidative stress; p66ShcA

DOI:  https://doi.org/10.1016/j.redox.2024.103028
Proc Natl Acad Sci U S A. 2024 Jan 16. 121(3): e2307904121

Systems-level analyses dissociate genetic regulators of reactive oxygen species and energy production.

Neal K Bennett, Megan Lee, Adam L Orr, Ken Nakamura.

  Respiratory chain dysfunction can decrease ATP and increase reactive oxygen species (ROS) levels. Despite the importance of these metabolic parameters to a wide range of cellular functions and disease, we lack an integrated understanding of how they are differentially regulated. To address this question, we adapted a CRISPRi- and FACS-based platform to compare the effects of respiratory gene knockdown on ROS to their effects on ATP. Focusing on genes whose knockdown is known to decrease mitochondria-derived ATP, we showed that knockdown of genes in specific respiratory chain complexes (I, III, and CoQ10 biosynthesis) increased ROS, whereas knockdown of other low ATP hits either had no impact (mitochondrial ribosomal proteins) or actually decreased ROS (complex IV). Moreover, although shifting metabolic conditions profoundly altered mitochondria-derived ATP levels, it had little impact on mitochondrial or cytosolic ROS. In addition, knockdown of a subset of complex I subunits-including NDUFA8, NDUFB4, and NDUFS8-decreased complex I activity, mitochondria-derived ATP, and supercomplex level, but knockdown of these genes had differential effects on ROS. Conversely, we found an essential role for ether lipids in the dynamic regulation of mitochondrial ROS levels independent of ATP. Thus, our results identify specific metabolic regulators of cellular ATP and ROS balance that may help dissect the roles of these processes in disease and identify therapeutic strategies to independently target energy failure and oxidative stress.

Keywords:  ATP; CRISPRi; ROS; metabolism; mitochondria

DOI:  https://doi.org/10.1073/pnas.2307904121
Res Sq. 2023 Dec 21. pii: rs.3.rs-3755231. [Epub ahead of print]

Sulfur Amino Acid Restriction alters mitochondrial function depending on tissue, sex, and Methionine sulfoxide reductase A (MsrA) status.

Kevin M Thyne, Raechel Camones, Adam B Salmon.

Methionine restriction (MR) has been shown to affect mitochondrial function including altering oxygen consumption, reactive oxygen species (ROS) generation, Complex expression, and oxidative damage. The sulfur-containing amino acid methionine can become oxidized forming methionine sulfoxide which can lead to changes in protein function and signaling. Methionine sulfoxide reductases are endogenous enzymes capable of reducing methionine sulfoxide, with Methionine sulfoxide reductase A (MsrA) being ubiquitously expressed in mammals. Here we investigated if the effects of MR on mitochondrial function required functional MsrA in the liver and kidney which are the major tissues involved in sulfur biochemistry and both highly express MsrA. Moreover, MsrA is endogenously found in the mitochondria thereby providing potential mechanisms linking diet to mitochondrial phenotype. We found sex-specific changes in oxygen consumption of isolated mitochondria and females showed changes with MR in a tissue-dependent manner - increased in liver and decreased in kidney. Loss of MsrA increased or decreased oxygen consumption depending on the tissue and which portion of the electron transport chain was being tested. In general, males had few changes in either tissue regardless of MR or MsrA status. Hydrogen peroxide production was increased in the kidney with MR regardless of sex or MsrA status. However, in the liver, production was increased by MR in females and only slightly higher with loss of MsrA in both sexes. Mitochondrial Complex expression was found to be largely unchanged in either tissue suggesting these effects are driven by regulatory mechanisms and not by changes in expression. Together these results suggest that sex and MsrA status do impact the mitochondrial effects of MR in a tissue-specific manner.

DOI: https://doi.org/10.21203/rs.3.rs-3755231/v1
BMC Cancer. 2024 Jan 08. 24(1): 43

Ovarian cancer cells regulate their mitochondrial content and high mitochondrial content is associated with a poor prognosis.

Jil Weigelt, Mariam Petrosyan, Leticia Oliveira-Ferrer, Barbara Schmalfeldt, Catharina Bartmann, Johannes Dietl, Christine Stürken, Udo Schumacher.

  Most cancer patients ultimately die from the consequences of distant metastases. As metastasis formation consumes energy mitochondria play an important role during this process as they are the most important cellular organelle to synthesise the energy rich substrate ATP, which provides the necessary energy to enable distant metastasis formation. However, mitochondria are also important for the execution of apoptosis, a process which limits metastasis formation. We therefore wanted to investigate the mitochondrial content in ovarian cancer cells and link its presence to the patient's prognosis in order to analyse which of the two opposing functions of mitochondria dominates during the malignant progression of ovarian cancer. Monoclonal antibodies directed against different mitochondrial specific proteins, namely heat shock proteins 60 (HSP60), fumarase and succinic dehydrogenase, were used in immunohistochemistry in preliminary experiments to identify the antibody most suited to detect mitochondria in ovarian cancer cells in clinical tissue samples. The clearest staining pattern, which even delineated individual mitochondria, was seen with the anti-HSP60 antibody, which was used for the subsequent clinical study staining primary ovarian cancers (n = 155), borderline tumours (n = 24) and recurrent ovarian cancers (n = 26). The staining results were semi-quantitatively scored into three groups according to their mitochondrial content: low (n = 26), intermediate (n = 50) and high (n = 84). Survival analysis showed that high mitochondrial content correlated with a statistically significant overall reduced survival rate In addition to the clinical tissue samples, mitochondrial content was analysed in ovarian cancer cells grown in vitro (cell lines: OVCAR8, SKOV3, OVCAR3 and COV644) and in vivo in severe combined immunodeficiency (SCID) mice.In in vivo grown SKOV3 and OVCAR8 cells, the number of mitochondria positive cells was markedly down-regulated compared to the in vitro grown cells indicating that mitochondrial number is subject to regulatory processes. As high mitochondrial content is associated with a poor prognosis, the provision of high energy substrates by the mitochondria seems to be more important for metastasis formation than the inhibition of apoptotic cell death, which is also mediated by mitochondria. In vivo and in vitro grown human ovarian cancer cells showed that the mitochondrial content is highly adaptable to the growth condition of the cancer cells.

Keywords:  Immunohistochemistry; Intraperitoneal metastases; Mitochondria; Ovarian cancer; Ovarian cancer prognosis; Ovarian cancer xenografts

DOI:  https://doi.org/10.1186/s12885-023-11667-8
Free Radic Biol Med. 2024 Jan 09. pii: S0891-5849(24)00004-2. [Epub ahead of print]

MARCH5-mediated downregulation of ACC2 promotes fatty acid oxidation and tumor progression in ovarian cancer.

Shuhua Zhao, Qingqiang Wang, Xiaohong Zhang, Boyi Ma, Yuan Shi, Yadong Yin, Weina Kong, Wei Zhang, Jibin Li, Hong Yang.

  Lipid metabolic reprogramming has been recognized as a hallmark of human cancer. Acetyl-CoA Carboxylases (ACCs) are key rate-limiting enzymes involved in fatty acid metabolism regulation by catalyzing the carboxylation of acetyl-CoA to malonyl-CoA. Previously, most studies focused on the role of ACC1 in fatty acid metabolism in cancer, while the function of ACC2 remains largely uncharacterized in human cancers, especially in ovarian cancer (OC). Here, we show that ACC2 was significantly downregulated in cancerous tissue of OC, and the downregulation of ACC2 is closely associated with lager tumor size, metastases and worse prognosis in OC patients. Downregulation of ACC2 promoted proliferation and metastasis of OC both in vitro and in vivo by enhancing FAO. Notably, mitochondria-associated ubiquitin ligase (MARCH5) was identified to interact with and downregulate ACC2 by ubiquitination and degradation in OC. Moreover, ACC2 downregulation-enhanced FAO contributed to the progression of OC promoted by MARCH5. In conclusion, our findings demonstrate that MARCH5-mediated downregulation of ACC2 promotes FAO and tumorigenesis in OC, suggesting MARCH5-ACC2 axis as a potent candidate for the treatment and prevention of OC.

Keywords:  ACC2; Disease progression; FAO; MARCH5; OC

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.01.004
Blood Adv. 2024 Jan 10. pii: bloodadvances.2023010435. [Epub ahead of print]

Monosomy 7/del(7q) Cause Sensitivity to Inhibitors of Nicotinamide Phosphoribosyltransferase in Acute Myeloid Leukemia.

Samuli Eldfors, Joseph Saad, Nemo Koi Ikonen, Disha Malani, Markus Vähä-Koskela, Bjorn T Gjertsen, Mika Kontro, Kimmo Porkka, Caroline A Heckman.

Monosomy 7 and del(7q) (-7/-7q) are frequent chromosomal abnormalities detected in up to 10% of patients with acute myeloid leukemia (AML). Despite unfavorable treatment outcomes, no approved targeted therapies exist for patients with -7/-7q. Therefore, we aimed to identify novel vulnerabilities. Through an analysis of data from ex vivo drug screens of 114 primary AML samples, we discovered that -7/-7q AML cells are highly sensitive to the inhibition of nicotinamide phosphoribosyltransferase (NAMPT). NAMPT is the rate-limiting enzyme in the NAD+ salvage pathway. Mechanistically, the NAMPT gene is located at 7q22.3, and deletion of one copy due to -7/-7q results in NAMPT haploinsufficiency, leading to reduced expression and a therapeutically targetable vulnerability to the inhibition of NAMPT. Our results show that in -7/-7q AML, differentiated CD34+CD38+ myeloblasts are more sensitive to the inhibition of NAMPT than less differentiated CD34+CD38- myeloblasts. Furthermore, the combination of the BCL2 inhibitor venetoclax and the NAMPT inhibitor KPT-9274 resulted in the death of significantly more leukemic blasts in AML samples with -7/-7q compared to the NAMPT inhibitor alone. In conclusion, our findings demonstrate that AML with -7/-7q are highly sensitive to NAMPT inhibition, suggesting that NAMPT inhibitors have the potential to be an effective targeted therapy for patients with monosomy 7 or del(7q).

DOI: https://doi.org/10.1182/bloodadvances.2023010435
Mol Metab. 2024 Jan 10. pii: S2212-8778(24)00007-3. [Epub ahead of print] 101876

NF1 deficiency drives metabolic reprogramming in ER+ breast cancer.

Rachel Rae J House, Elizabeth A Tovar, Curt J Essenburg, Patrick S Dischinger, Abigail E Ellis, Ian Beddows, Ryan D Sheldon, Evan C Lien, Carrie R Graveel, Matthew R Steensma.

   OBJECTIVE: NF1 is a tumor suppressor gene and its protein product, neurofibromin, is a negative regulator of the RAS pathway. NF1 is one of the top driver mutations in sporadic breast cancer such that 27% of breast cancers exhibit damaging NF1 alterations. NF1 loss-of-function is a frequent event in the genomic evolution of estrogen receptor (ER)+ breast cancer metastasis and endocrine resistance. Individuals with Neurofibromatosis type 1 (NF) - a disorder caused by germline NF1 mutations - have an increased risk of dying from breast cancer [1-4]. NF-related breast cancers are associated with decreased overall survival compared to sporadic breast cancer. Despite numerous studies interrogating the role of RAS mutations in tumor metabolism, no study has comprehensively profiled the NF1-deficient breast cancer metabolome to define patterns of energetic and metabolic reprogramming. The goals of this investigation were (1) to define the role of NF1 deficiency in estrogen receptor-positive (ER+) breast cancer metabolic reprogramming and (2) to identify potential targeted pathway and metabolic inhibitor combination therapies for NF1-deficient ER+ breast cancer.
METHODS: We employed two ER+ NF1-deficient breast cancer models: (1) an NF1-deficient MCF7 breast cancer cell line to model sporadic breast cancer, and (2) three distinct, Nf1-deficient rat models to model NF-related breast cancer [1]. IncuCyte proliferation analysis was used to measure the effect of NF1 deficiency on cell proliferation and drug response. Protein quantity was assessed by Western Blot analysis. We then used RNAseq to investigate the transcriptional effect of NF1 deficiency on global and metabolism-related transcription. We measured cellular energetics using Agilent Seahorse XF-96 Glyco Stress Test and Mito Stress Test assays. We performed stable isotope labeling and measured [U-13C]-glucose and [U-13C]-glutamine metabolite incorporation and measured total metabolite pools using mass spectrometry. Lastly, we used a Bliss synergy model to investigate NF1-driven changes in targeted and metabolic inhibitor synergy.
RESULTS: Our results revealed that NF1 deficiency enhanced cell proliferation, altered neurofibromin expression, and increased RAS and PI3K/AKT pathway signaling while constraining oxidative ATP production and restricting energetic flexibility. Neurofibromin deficiency also increased glutamine influx into TCA intermediates and dramatically increased lipid pools, especially triglycerides (TG). Lastly, NF1 deficiency alters the synergy between metabolic inhibitors and traditional targeted inhibitors. This includes increased synergy with inhibitors targeting glycolysis, glutamine metabolism, mitochondrial fatty acid transport, and TG synthesis.
CONCLUSIONS: NF1 deficiency drives metabolic reprogramming in ER+ breast cancer. This reprogramming is characterized by oxidative ATP constraints, glutamine TCA influx, and lipid pool expansion, and these metabolic changes introduce novel metabolic-to-targeted inhibitor synergies.

Keywords:  NF1; Neurofibromatosis Type 1; breast cancer; metabolic inhibition; metabolic reprogramming

DOI:  https://doi.org/10.1016/j.molmet.2024.101876
Cancer Metastasis Rev. 2024 Jan 09.

UCP2 and pancreatic cancer: conscious uncoupling for therapeutic effect.

Emily G Caggiano, Cullen M Taniguchi.

  Pancreatic cancer has an exaggerated dependence on mitochondrial metabolism, but methods to specifically target the mitochondria without off target effects in normal tissues that rely on these organelles is a significant challenge. The mitochondrial uncoupling protein 2 (UCP2) has potential as a cancer-specific drug target, and thus, we will review the known biology of UCP2 and discuss its potential role in the pathobiology and future therapy of pancreatic cancer.

Keywords:  Metabolism; Mitochondria; Pancreatic cancer; Therapeutics; Uncoupling

DOI:  https://doi.org/10.1007/s10555-023-10157-4
Free Radic Biol Med. 2024 Jan 10. pii: S0891-5849(24)00005-4. [Epub ahead of print]

Propionate promotes ferroptosis and apoptosis through mitophagy and ACSL4-mediated ferroptosis elicits anti-leukemia immunity.

Yihong Wei, Wancheng Liu, Ruiqing Wang, Yuhong Chen, Jinting Liu, Xiaodong Guo, Can Can, Xinyu Yang, Dongmei Wang, Xiang Hu, Daoxin Ma.

  Short-chain fatty acids (SCFAs), particularly propionate and butyrate, have been reported in many cancers. However, the relationship between propionate and acute myeloid leukemia (AML) remains unclear. Additionally, Acyl-CoA synthetase long chain family member 4 (ACSL4) has been reported to regulate immunity in solid tumors, but there are still many gaps to be filled in AML. Here, we discovered the underlying mechanism of propionate and ACSL4-mediated ferroptosis for immunotherapy. Our results showed that the level of propionate in the AML patients' feces was decreased, which was correlated to gut microbiota dysbiosis. Moreover, we demonstrated that propionate suppressed AML progression both in vivo and in vitro. In mechanism, propionate induced AML cells apoptosis and ferroptosis. The imbalance of reactive oxygen species (ROS) and redox homeostasis induced by propionate caused mitochondrial fission and mitophagy, which enhanced ferroptosis and apoptosis. Furthermore, ACSL4-mediated ferroptosis caused by propionate increased the immunogenicity of AML cells, induced the release of damage-associated molecular patterns (DAMPs), and promoted the maturation of dendritic cells (DCs). The increased level of immunogenicity due to ferroptosis enable propionate-based whole-cell vaccines to activate immunity, thus further facilitating effective killing of AML cells. Collectively, our study uncovers a crucial role for propionate suppresses AML progression by inducing ferroptosis and the potential mechanisms of ACSL4-mediated ferroptosis in the regulation of AML immunity.

Keywords:  ACSL4; Acute myeloid leukemia; Ferroptosis; Mitophagy; Propionate; ROS

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.01.005
Mol Cell. 2023 Dec 29. pii: S1097-2765(23)01031-6. [Epub ahead of print]

Identification of TMEM126A as OXA1L-interacting protein reveals cotranslational quality control in mitochondria.

Sabine Poerschke, Silke Oeljeklaus, Luis Daniel Cruz-Zaragoza, Alexander Schenzielorz, Drishan Dahal, Hauke Sven Hillen, Hirak Das, Laura Sophie Kremer, Anusha Valpadashi, Mirjam Breuer, Johannes Sattmann, Ricarda Richter-Dennerlein, Bettina Warscheid, Sven Dennerlein, Peter Rehling.

  Cellular proteostasis requires transport of polypeptides across membranes. Although defective transport processes trigger cytosolic rescue and quality control mechanisms that clear translocases and membranes from unproductive cargo, proteins that are synthesized within mitochondria are not accessible to these mechanisms. Mitochondrial-encoded proteins are inserted cotranslationally into the inner membrane by the conserved insertase OXA1L. Here, we identify TMEM126A as a OXA1L-interacting protein. TMEM126A associates with mitochondrial ribosomes and translation products. Loss of TMEM126A leads to the destabilization of mitochondrial translation products, triggering an inner membrane quality control process, in which newly synthesized proteins are degraded by the mitochondrial iAAA protease. Our data reveal that TMEM126A cooperates with OXA1L in protein insertion into the membrane. Upon loss of TMEM126A, the cargo-blocked OXA1L insertase complexes undergo proteolytic clearance by the iAAA protease machinery together with its cargo.

Keywords:  mitochondria; mitochondrial quality control; mitochondrial translation

DOI:  https://doi.org/10.1016/j.molcel.2023.12.013
Cell Rep. 2024 Jan 10. pii: S2211-1247(23)01599-1. [Epub ahead of print]43(1): 113587

The mitochondrial genome-encoded peptide MOTS-c interacts with Bcl-2 to alleviate nonalcoholic steatohepatitis progression.

Huanyu Lu, Linni Fan, Wenli Zhang, Guo Chen, An Xiang, Li Wang, Zifan Lu, Yue Zhai.

  Nonalcoholic steatohepatitis (NASH) is a metabolism-associated fatty liver disease with accumulated mitochondrial stress, and targeting mitochondrial function is a potential therapy. The mitochondrial genome-encoded bioactive peptide MOTS-c plays broad physiological roles, but its effectiveness and direct targets in NASH treatment are still unclear. Here, we show that long-term preventive and short-term therapeutic effects of MOTS-c treatments alleviate NASH-diet-induced liver steatosis, cellular apoptosis, inflammation, and fibrosis. Mitochondrial oxidative capacity and metabolites profiling analysis show that MOTS-c significantly reverses NASH-induced mitochondrial metabolic deficiency. Moreover, we identify that MOTS-c directly interacts with the BH3 domain of antiapoptotic B cell lymphoma-2 (Bcl-2), increases Bcl-2 protein stability, and suppresses Bcl-2 ubiquitination. By using a Bcl-2 inhibitor or adeno-associated virus (AAV)-mediated Bcl-2 knockdown, we further confirm that MOTS-c improves NASH-induced mitochondrial dysfunction, inflammation, and fibrosis, which are dependent on Bcl-2 function. Therefore, our findings show that MOTS-c is a potential therapeutic agent to inhibit the progression of NASH.

Keywords:  Bcl-2; CP: Metabolism; CP: Molecular biology; MOTS-c; apoptosis; mitochondrial dysfunction; nonalcoholic steatohepatitis

DOI:  https://doi.org/10.1016/j.celrep.2023.113587
Brain. 2024 Jan 09. pii: awae007. [Epub ahead of print]

Huntington disease affects mitochondrial network dynamics predisposing to pathogenic mtDNA mutations.

Andreas Neueder, Kerstin Kojer, Zhenglong Gu, Yiqin Wang, Tanja Hering, Sarah Tabrizi, Jan-Willem Taanman, Michael Orth.

  Huntington disease (HD) predominantly affects the brain causing a mixed movement disorder, cognitive decline and behavioural abnormalities. It also causes a peripheral phenotype involving skeletal muscle. Mitochondrial dysfunction has been reported in tissues of HD models, including skeletal muscle, and lymphoblasts and fibroblasts cultures from HD patients. Mutant huntingtin protein (mutHTT) expression can impair mitochondrial quality control and accelerate mitochondrial ageing. Here we obtained fresh human skeletal muscle, a post-mitotic tissue expressing the mutated HTT allele at physiological levels since birth, and primary cell lines from HTT CAG repeat expansion mutation carriers and matched healthy volunteers to examine whether such a mitochondrial phenotype exists in human HD. Using ultra-deep mitochondrial DNA (mtDNA) sequencing, we show an accumulation of mtDNA mutations affecting oxidative phosphorylation. Tissue proteomics indicate impairments in mtDNA maintenance with increased mitochondrial biogenesis of less efficient oxidative phosphorylation (lower complex I and IV activity). In full-length mutHTT expressing primary human cell lines, fission inducing mitochondrial stress resulted in normal mitophagy. In contrast, expression of high levels of N-terminal mutHTT fragments promoted mitochondrial fission and resulted in slower, less dynamic mitophagy. Expression of high levels of mutHTT fragments due to somatic nuclear HTT CAG instability can thus affect mitochondrial network dynamics and mitophagy leading to pathogenic mtDNA mutations. We show that life-long expression of mutant HTT causes a mitochondrial phenotype indicative of mtDNA instability in fresh post-mitotic human skeletal muscle. Thus, genomic instability may not be limited to nuclear DNA where it results in somatic expansion of HTT CAG repeat length in particularly vulnerable cells, such as striatal neurons. In addition to efforts targeting the causative mutation promoting mitochondrial health may be a complementary strategy in treating diseases with DNA instability, such as HD.

Keywords:  DNA instability; huntingtin fragments; mitochondrial fission; mitophagy; proteomics; ultra-deep mitochondrial DNA sequencing

DOI:  https://doi.org/10.1093/brain/awae007
Br J Cancer. 2024 Jan 12.

Peroxisomal β-oxidation enzyme, DECR2, regulates lipid metabolism and promotes treatment resistance in advanced prostate cancer.

Chui Yan Mah, An Dieu Trang Nguyen, Takuto Niijima, Madison Helm, Jonas Dehairs, Feargal J Ryan, Natalie Ryan, Lake-Ee Quek, Andrew J Hoy, Anthony S Don, Ian G Mills, Johannes V Swinnen, David J Lynn, Zeyad D Nassar, Lisa M Butler.

BACKGROUND: Peroxisomes are central metabolic organelles that have key roles in fatty acid homoeostasis. As prostate cancer (PCa) is particularly reliant on fatty acid metabolism, we explored the contribution of peroxisomal β-oxidation (perFAO) to PCa viability and therapy response.
METHODS: Bioinformatic analysis was performed on clinical transcriptomic datasets to identify the perFAO enzyme, 2,4-dienoyl CoA reductase 2 (DECR2) as a target gene of interest. Impact of DECR2 and perFAO inhibition via thioridazine was examined in vitro, in vivo, and in clinical prostate tumours cultured ex vivo. Transcriptomic and lipidomic profiling was used to determine the functional consequences of DECR2 inhibition in PCa.
RESULTS: DECR2 is upregulated in clinical PCa, most notably in metastatic castrate-resistant PCa (CRPC). Depletion of DECR2 significantly suppressed proliferation, migration, and 3D growth of a range of CRPC and therapy-resistant PCa cell lines, and inhibited LNCaP tumour growth and proliferation in vivo. DECR2 influences cell cycle progression and lipid metabolism to support tumour cell proliferation. Further, co-targeting of perFAO and standard-of-care androgen receptor inhibition enhanced suppression of PCa cell proliferation.
CONCLUSION: Our findings support a focus on perFAO, specifically DECR2, as a promising therapeutic target for CRPC and as a novel strategy to overcome lethal treatment resistance.

DOI: https://doi.org/10.1038/s41416-023-02557-8
Cell. 2024 Jan 05. pii: S0092-8674(23)01342-9. [Epub ahead of print]

Hypoxia and intra-complex genetic suppressors rescue complex I mutants by a shared mechanism.

Joshua D Meisel, Maria Miranda, Owen S Skinner, Presli P Wiesenthal, Sandra M Wellner, Alexis A Jourdain, Gary Ruvkun, Vamsi K Mootha.

  The electron transport chain (ETC) of mitochondria, bacteria, and archaea couples electron flow to proton pumping and is adapted to diverse oxygen environments. Remarkably, in mice, neurological disease due to ETC complex I dysfunction is rescued by hypoxia through unknown mechanisms. Here, we show that hypoxia rescue and hyperoxia sensitivity of complex I deficiency are evolutionarily conserved to C. elegans and are specific to mutants that compromise the electron-conducting matrix arm. We show that hypoxia rescue does not involve the hypoxia-inducible factor pathway or attenuation of reactive oxygen species. To discover the mechanism, we use C. elegans genetic screens to identify suppressor mutations in the complex I accessory subunit NDUFA6/nuo-3 that phenocopy hypoxia rescue. We show that NDUFA6/nuo-3(G60D) or hypoxia directly restores complex I forward activity, with downstream rescue of ETC flux and, in some cases, complex I levels. Additional screens identify residues within the ubiquinone binding pocket as being required for the rescue by NDUFA6/nuo-3(G60D) or hypoxia. This reveals oxygen-sensitive coupling between an accessory subunit and the quinone binding pocket of complex I that can restore forward activity in the same manner as hypoxia.

Keywords:  C. elegans; NADH:ubiquinone oxidoreductase; NDUFA6; NDUFS4; complex I; electron transport chain; hyperoxia; hypoxia; mitochondria; oxygen

DOI:  https://doi.org/10.1016/j.cell.2023.12.010
Blood. 2024 01 11. pii: blood.2023019706. [Epub ahead of print]

Sonrotoclax overcomes BCL2 G101V mutation-induced venetoclax resistance in preclinical models of hematologic malignancy.

Jiuyang Liu, Shuran Li, Qin Wang, Yingcai Feng, Haimei Xing, Xuefei Yang, Ying Guo, Yunhang Guo, Hanzi Sun, Xiaoxin Liu, Shasha Yang, Zhu Mei, Yutong Zhu, Zhenzhen Cheng, Shuaishuai Chen, Min Xu, Wenjing Zhang, Nanyan Wan, Jia Wang, Yanwen Ma, Shuo Zhang, Xudong Luan, Aiying Xu, Lin Li, Haitao Wang, Xiaolong Yang, Yuan Hong, Hai Xue, Xi Yuan, Nan Hu, Xiaomin Song, Zhiwei Wang, Xuesong Liu, Lai Wang, Ye Liu.

Venetoclax, the first-generation inhibitor of the apoptosis regulator B-cell lymphoma 2 (BCL2), disrupts the interaction between BCL2 and pro-apoptotic proteins, promoting the apoptosis in malignant cells. Venetoclax is the mainstay of therapy for relapsed chronic lymphocytic leukemia (CLL) and is under investigation in multiple clinical trials for the treatment of various cancers. Although venetoclax treatment can result in high rates of durable remission, relapse has been widely observed, indicating the emergence of drug resistance. The G101V mutation in BCL2 is frequently observed in relapsed patients treated with venetoclax and sufficient to confer resistance to venetoclax by interfering with compound binding. Therefore, the development of next-generation BCL2 inhibitors to overcome drug resistance is urgently needed. Herein, we discovered sonrotoclax, a potent and selective BCL2 inhibitor, demonstrates stronger cytotoxic activity in various hematological cancer cells and more profound tumor growth inhibition in multiple hematological tumor models compared to venetoclax. Notably, sonrotoclax effectively inhibits venetoclax-resistant BCL2 variants, such as G101V. The crystal structures of wild-type (WT) BCL2/BCL2 G101V in complex with sonrotoclax revealed that sonrotoclax adopts a novel binding mode within the P2 pocket of BCL2 and could explain why sonrotoclax maintains stronger potency than venetoclax against the G101V mutant. In summary, sonrotoclax emerges as a potential second-generation BCL2 inhibitor for the treatment of hematologic malignancies with the potential to overcome BCL2 mutation-induced venetoclax resistance. Sonrotoclax is currently under investigation in multiple clinical trials.

DOI: https://doi.org/10.1182/blood.2023019706
Anticancer Drugs. 2024 Jan 15.

Inhibition of mitochondrial function by approved drugs overcomes nasopharyngeal carcinoma chemoresistance.

Yunlong Zhang, Difeng Guo, Yongbo Zhu, Lin Liu.

The development of chemo-resistance in nasopharyngeal carcinoma (NPC) presents a significant therapeutic challenge, and its underlying mechanisms remain poorly understood. In our previous studies, we highlighted the association between isoprenylcysteine carboxylmethyltransferase (ICMT) and chemoresistance in NPC. In this current research, we revealed that both 5-FU and cisplatin-resistant NPC cells exhibited elevated mitochondrial function and increased expression of mitochondrial genes, independent of ICMT. Our investigations further showed that classic mitochondrial inhibitors, such as oligomycin, antimycin, and rotenone, were notably more effective in reducing viability in chemo-resistant NPC cells compared to parental cells. Moreover, we identified two antimicrobial drugs, tigecycline and atovaquone, recognized as mitochondrial inhibitors, as potent agents for decreasing chemo-resistant NPC cells by targeting mitochondrial respiration. Remarkably, tigecycline and atovaquone, administered at tolerable doses, inhibited chemo-resistant NPC growth in mouse models and extended overall survival rates. This work unveils the efficacy of mitochondrial inhibition as a promising strategy to overcome chemo-resistance in NPC. Additionally, our findings highlight the potential repurposing of clinically available drugs like tigecycline and atovaquone for treating NPC patients who develop chemoresistance.

DOI: https://doi.org/10.1097/CAD.0000000000001566
iScience. 2024 Jan 19. 27(1): 108702

A mitochondria-targeting dihydroartemisinin derivative as a reactive oxygen species -based immunogenic cell death inducer.

Hong-Yang Zhao, Kun-Heng Li, Dan-Dan Wang, Zhi-Li Zhang, Zi-Jian Xu, Ming-Hui Qi, Shi-Wen Huang.

  Immunogenic cell death (ICD) can activate the anticancer immune response and its occurrence requires high reliance on oxidative stress. Inducing mitochondrial reactive oxygen species (ROS) is a desirable capability for ICD inducers. However, in the category of ICD-associated drugs, numerous reported ICD inducers are a series of anthracyclines and weak in ICD induction. Herein, a mitochondria-targeting dihydroartemisinin derivative (T-D) was synthesized by conjugating triphenylphosphonium (TPP) to dihydroartemisinin (DHA). T-D can selectively accumulate in mitochondria to trigger ROS generation, leading to the loss of mitochondrial membrane potential (ΔΨm) and ER stress. Notably, T-D exhibits far more potent ICD-inducing properties than its parent compound. In vivo, T-D-treated breast cancer cell vaccine inhibits metastasis to the lungs and tumor growth. These results indicate that T-D is an excellent ROS-based ICD inducer with the specific function of trigging vigorous ROS in mitochondria and sets an example for incorporating artemisinin-based drugs into the ICD field.

Keywords:  Cell biology; Immunology; Medical biochemistry

DOI:  https://doi.org/10.1016/j.isci.2023.108702
Oncogene. 2024 Jan 06.

The E3 ligase HUWE1 increases the sensitivity of CRC to oxaliplatin through TOMM20 degradation.

Chanhaeng Lee, Sang-Hee Park, Sungjoo Kim Yoon.

Continuous administration of oxaliplatin, the most widely used first-line chemotherapy drug for colorectal cancer (CRC), eventually leads to drug resistance. Increasing the sensitivity of CRC cells to oxaliplatin is a key strategy to overcome this issue. Impairment of mitochondrial function is a pivotal mechanism determining the sensitivity of CRC to oxaliplatin. We discovered an inverse correlation between Translocase of Outer Mitochondrial Membrane 20 (TOMM20) and oxaliplatin sensitivity as well as an inverse relationship between TOMM20 and HECT, UBA, and WWE domain containing E3 ligase 1 (HUWE1) expression in CRC. For the first time, we demonstrated that HUWE1 ubiquitinates TOMM20 directly and also regulates TOMM20 degradation via the PARKIN-mediated pathway. Furthermore, we showed that overexpression of HUWE1 in CRC cells has a negative effect on mitochondrial function, including the generation of ATP and maintenance of mitochondrial membrane potential, leading to increased production of ROS and apoptosis. This effect was amplified when cells were treated simultaneously with oxaliplatin. Our study conclusively shows that TOMM20 is a novel target of HUWE1. Our findings indicate that HUWE1 plays a critical role in regulating oxaliplatin sensitivity by degrading TOMM20 and inducing mitochondrial damage in CRC.

DOI: https://doi.org/10.1038/s41388-023-02928-8
Nat Commun. 2024 Jan 11. 15(1): 473

Disordered-to-ordered transitions in assembly factors allow the complex II catalytic subunit to switch binding partners.

Pankaj Sharma, Elena Maklashina, Markus Voehler, Sona Balintova, Sarka Dvorakova, Michal Kraus, Katerina Hadrava Vanova, Zuzana Nahacka, Renata Zobalova, Stepana Boukalova, Kristyna Cunatova, Tomas Mracek, Hans K Ghayee, Karel Pacak, Jakub Rohlena, Jiri Neuzil, Gary Cecchini, T M Iverson.

Complex II (CII) activity controls phenomena that require crosstalk between metabolism and signaling, including neurodegeneration, cancer metabolism, immune activation, and ischemia-reperfusion injury. CII activity can be regulated at the level of assembly, a process that leverages metastable assembly intermediates. The nature of these intermediates and how CII subunits transfer between metastable complexes remains unclear. In this work, we identify metastable species containing the SDHA subunit and its assembly factors, and we assign a preferred temporal sequence of appearance of these species during CII assembly. Structures of two species show that the assembly factors undergo disordered-to-ordered transitions without the appearance of significant secondary structure. The findings identify that intrinsically disordered regions are critical in regulating CII assembly, an observation that has implications for the control of assembly in other biomolecular complexes.

DOI: https://doi.org/10.1038/s41467-023-44563-7
bioRxiv. 2023 Dec 24. pii: 2023.12.24.573250. [Epub ahead of print]

Metabolite profiling of human renal cell carcinoma reveals tissue-origin dominance in nutrient availability.

Keene L Abbott, Ahmed Ali, Bradley I Reinfeld, Amy Deik, Sonu Subudhi, Madelyn D Landis, Rachel A Hongo, Kirsten L Young, Tenzin Kunchok, Christopher S Nabel, Kayla D Crowder, Johnathan R Kent, Maria Lucia L Madariaga, Rakesh K Jain, Kathryn E Beckermann, Caroline A Lewis, Clary B Clish, Alexander Muir, W Kimryn Rathmell, Jeffrey C Rathmell, Matthew G Vander Heiden.

The tumor microenvironment is a determinant of cancer progression and therapeutic efficacy, with nutrient availability playing an important role. Although it is established that the local abundance of specific nutrients defines the metabolic parameters for tumor growth, the factors guiding nutrient availability in tumor compared to normal tissue and blood remain poorly understood. To define these factors in renal cell carcinoma (RCC), we performed quantitative metabolomic and comprehensive lipidomic analyses of tumor interstitial fluid (TIF), adjacent normal kidney interstitial fluid (KIF), and plasma samples collected from patients. TIF nutrient composition closely resembles KIF, suggesting that tissue-specific factors unrelated to the presence of cancer exert a stronger influence on nutrient levels than tumor-driven alterations. Notably, select metabolite changes consistent with known features of RCC metabolism are found in RCC TIF, while glucose levels in TIF are not depleted to levels that are lower than those found in KIF. These findings inform tissue nutrient dynamics in RCC, highlighting a dominant role of non-cancer driven tissue factors in shaping nutrient availability in these tumors.

DOI: https://doi.org/10.1101/2023.12.24.573250
Cell Death Dis. 2024 Jan 11. 15(1): 32

Antitumour effect of the mitochondrial complex III inhibitor Atovaquone in combination with anti-PD-L1 therapy in mouse cancer models.

Gonzalo Rodriguez-Berriguete, Rathi Puliyadi, Nicole Machado, Alessandro Barberis, Remko Prevo, Martin McLaughlin, Francesca M Buffa, Kevin J Harrington, Geoff S Higgins.

Immune checkpoint blockade (ICB) provides effective and durable responses for several tumour types by unleashing an immune response directed against cancer cells. However, a substantial number of patients treated with ICB develop relapse or do not respond, which has been partly attributed to the immune-suppressive effect of tumour hypoxia. We have previously demonstrated that the mitochondrial complex III inhibitor atovaquone alleviates tumour hypoxia both in human xenografts and in cancer patients by decreasing oxygen consumption and consequently increasing oxygen availability in the tumour. Here, we show that atovaquone alleviates hypoxia and synergises with the ICB antibody anti-PD-L1, significantly improving the rates of tumour eradication in the syngeneic CT26 model of colorectal cancer. The synergistic effect between atovaquone and anti-PD-L1 relied on CD8+ T cells, resulted in the establishment of a tumour-specific memory immune response, and was not associated with any toxicity. We also tested atovaquone in combination with anti-PD-L1 in the LLC (lung) and MC38 (colorectal) cancer syngeneic models but, despite causing a considerable reduction in tumour hypoxia, atovaquone did not add any therapeutic benefit to ICB in these models. These results suggest that atovaquone has the potential to improve the outcomes of patients treated with ICB, but predictive biomarkers are required to identify individuals likely to benefit from this intervention.

DOI: https://doi.org/10.1038/s41419-023-06405-8
J Genet Genomics. 2024 Jan 04. pii: S1673-8527(24)00001-8. [Epub ahead of print]

CircPTEN-MT from PTEN regulates mitochondrial energy metabolism.

Danhui Ruan, Jiancheng Xu, Yang Liu, Juan Luo, Xuyang Zhao, Yuhua Li, Guangxi Wang, Jiawen Feng, Hui Liang, Yue Yin, Jianyuan Luo, Yuxin Yin.

  PTEN is a multifunctional gene that is involved in a variety of physiological and pathological processes. Circular RNAs (circRNAs) are generated from back-splicing events during mRNA processing and participate in cell biological processes through binding to RNAs or proteins. However, PTEN-related circRNAs are largely unknown. Here we report that circPTEN-MT (hsa_circ_0002934) is a circular RNA encoded by exons 3, 4, and 5 of PTEN and is a critical regulator of mitochondrial energy metabolism. CircPTEN-MT is localized to mitochondria and physically associated with leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), which regulates posttranscriptional gene expression in mitochondria. Knocking down circPTEN-MT reduces the interaction of LRPPRC and SRA stem-loop interacting RNA binding protein (SLIRP) and inhibits the polyadenylation of mitochondrial mRNA, which decreases the mRNA level of the mitochondrial complex Ι subunit and reduces mitochondrial membrane potential (MMP) and ATP production. Our data demonstrate that circPTEN-MT is an important regulator of cellular energy metabolism. This study expands our understanding of the role of PTEN which produces both linear and circular RNAs with different and independent functions.

Keywords:  Circular RNA/ LRPPRC/ Mitochondrial energy metabolism/ mtDNA post-transcriptional regulation

DOI:  https://doi.org/10.1016/j.jgg.2023.12.011
Cancers (Basel). 2023 Dec 19. pii: 8. [Epub ahead of print]16(1):

High Mitochondrial Protein Expression as a Potential Predictor of Relapse Risk in Acute Myeloid Leukemia Patients with the Monocytic FAB Subtypes M4 and M5.

Frode Selheim, Elise Aasebø, Øystein Bruserud, Maria Hernandez-Valladares.

  AML is a highly aggressive and heterogeneous form of hematological cancer. Proteomics-based stratification of patients into more refined subgroups may contribute to a more precise characterization of the patient-derived AML cells. Here, we reanalyzed liquid chromatography-tandem mass spectrometry (LC-MS/MS) generated proteomic and phosphoproteomic data from 26 FAB-M4/M5 patients. The patients achieved complete hematological remission after induction therapy. Twelve of them later developed chemoresistant relapse (RELAPSE), and 14 patients were relapse-free (REL_FREE) long-term survivors. We considered not only the RELAPSE and REL_FREE characteristics but also integrated the French-American-British (FAB) classification, along with considering the presence of nucleophosmin 1 (NPM1) mutation and cytogenetically normal AML. We found a significant number of differentially enriched proteins (911) and phosphoproteins (257) between the various FAB subtypes in RELAPSE patients. Patients with the myeloblastic M1/M2 subtype showed higher levels of RNA processing-related routes and lower levels of signaling related to terms like translation and degranulation when compared with the M4/M5 subtype. Moreover, we found that a high abundance of proteins associated with mitochondrial translation and oxidative phosphorylation, particularly observed in the RELAPSE M4/M5 NPM1 mutated subgroup, distinguishes relapsing from non-relapsing AML patient cells with the FAB subtype M4/M5. Thus, the discovery of subtype-specific biomarkers through proteomic profiling may complement the existing classification system for AML and potentially aid in selecting personalized treatment strategies for individual patients.

Keywords:  FAB subtypes; acute myeloid leukemia; mass spectrometry; mitochondria; phosphoproteomic; proteomic; relapse

DOI:  https://doi.org/10.3390/cancers16010008
J Inherit Metab Dis. 2024 Jan 10.

Glyoxylate reductase: Definitive identification in human liver mitochondria, its importance for the compartment-specific detoxification of glyoxylate.

Sander F Garrelfs, Serhii Chornyi, Heleen Te Brinke, Jos Ruiter, Jaap Groothoff, Ronald J A Wanders.

  Glyoxylate is a key metabolite generated from various precursor substrates in different subcellular compartments including mitochondria, peroxisomes, and the cytosol. The fact that glyoxylate is a good substrate for the ubiquitously expressed enzyme lactate dehydrogenase (LDH) requires the presence of efficient glyoxylate detoxification systems to avoid the formation of oxalate. Furthermore, this detoxification needs to be compartment-specific since LDH is actively present in multiple subcellular compartments including peroxisomes, mitochondria, and the cytosol. Whereas the identity of these protection systems has been established for both peroxisomes and the cytosol as concluded from the deficiency of alanine glyoxylate aminotransferase (AGT) in primary hyperoxaluria type 1 (PH1) and glyoxylate reductase (GR) in PH2, the glyoxylate protection system in mitochondria has remained less well defined. In this manuscript, we show that the enzyme glyoxylate reductase has a bimodal distribution in human embryonic kidney (HEK293), hepatocellular carcinoma (HepG2), and cervical carcinoma (HeLa) cells and more importantly, in human liver, and is actively present in both the mitochondrial and cytosolic compartments. We conclude that the metabolism of glyoxylate in humans requires the complicated interaction between different subcellular compartments within the cell and discuss the implications for the different primary hyperoxalurias.

Keywords:  glyoxylate metabolism; hydroxyproline; hyperoxaluria; mitochondria; oxalate; peroxisomal disorders; peroxisomes

DOI:  https://doi.org/10.1002/jimd.12711
Mol Carcinog. 2024 Jan 10.

Nicotinamide mononucleotide induces autophagy and ferroptosis via AMPK/mTOR pathway in hepatocellular carcinoma.

Zhanbo Sun, Lixian Liu, Hongyuan Liang, Lingyun Zhang.

  Hepatocellular carcinoma (HCC) is a common malignancy worldwide. Herein, we investigated the role of nicotinamide mononucleotide (NMN) in HCC progression. HCC cells were treated with NMN (125, 250, and 500 μM), and then nicotinamide adenine dinucleotide (NAD+ ) and NADH levels in HCC cells were measured to calculate NAD+ /NADH ratio. Cell proliferation, apoptosis, autophagy and ferroptosis were determined. AMPK was knocked down to confirm the involvement of AMPK/mTOR signaling. Furthermore, tumor-inhibitory effect of NMN was investigated in xenograft models. Exposure to NMN dose-dependently increased NAD+ level and NAD+ /NADH ratio in HCC cells. After NMN treatment, cell proliferation was inhibited, whereas apoptosis was enhanced in both cell lines. Additionally, NMN dose-dependently enhanced autophagy/ferroptosis and activated AMPK/mTOR pathway in HCC cells. AMPK knockdown partially rescued the effects of NMN in vitro. Furthermore, NMN treatment restrained tumor growth in nude mice, activated autophagy/ferroptosis, and promoted apoptosis and necrosis in tumor tissues. The results indicate that NMN inhibits HCC progression by inducing autophagy and ferroptosis via AMPK/mTOR signaling. NMN may serve as a promising agent for HCC treatment.

Keywords:  autophagy; ferroptosis; hepatocellular carcinoma; nicotinamide adenine dinucleotide biosynthesis; nicotinamide mononucleotide

DOI:  https://doi.org/10.1002/mc.23673
Res Sq. 2023 Dec 20. pii: rs.3.rs-3664129. [Epub ahead of print]

The Combined Treatment with Ketogenic Diet and Metformin Slows Tumor Growth in Two Mouse Models of Triple Negative Breast Cancer.

Karen Schmidt, Amber Thatcher, Albert Grobe, Linda Hicks, Haiwei Gu, Dorothy D Sears, Lesley G Ellies, Leonid Kalachev, Eugene Kroll.

BACKGROUND Many tumors contain hypoxic microenvironments caused by inefficient tumor vascularization. Hypoxic tumors have been shown to resist conventional cancer therapies. Hypoxic cancer cells rely on glucose to meet their energetic and anabolic needs to fuel uncontrolled proliferation and metastasis. This glucose dependency is linked to a metabolic shift in response to hypoxic conditions. METHODS To leverage the glucose dependency of hypoxic tumor cells, we assessed the effects of a controlled reduction in systemic glucose by combining dietary carbohydrate restriction, using a ketogenic diet, with gluconeogenesis inhibition, using metformin, on two mouse models of triple-negative breast cancer (TNBC). RESULTS We confirmed that MET - 1 breast cancer cells require abnormally high glucose concentrations to survive in a hypoxic environment in vitro. Then, we showed that, compared to a ketogenic diet or metformin alone, animals treated with the combination regimen showed significantly lower tumor burden, higher tumor latency and slower tumor growth. As a result, lowering systemic glucose by this combined dietary and pharmacologic approach improved overall survival in our mouse model by 31 days, which is approximately equivalent to 3 human years. CONCLUSION This is the first preclinical study to demonstrate that reducing systemic glucose by combining a ketogenic diet and metformin significantly inhibits tumor proliferation and increases overall survival. Our findings suggest a possible treatment for a broad range of hypoxic and glycolytic tumor types, one that can also augment existing treatment options to improve patient outcomes.

DOI: https://doi.org/10.21203/rs.3.rs-3664129/v1
Blood Adv. 2024 Jan 08. pii: bloodadvances.2023011131. [Epub ahead of print]

Reprogramming of pyrimidine nucleotide metabolism supports vigorous cell proliferation of normal and malignant T cells.

Tatsuro Watanabe, Yuta Yamamoto, Yuki Kurahashi, Kazunori Kawazoe, Keisuke Kidoguchi, Hiroshi Ureshino, Kazuharu Kamachi, Nao Yoshida-Sakai, Yuki Fukuda-Kurahashi, Hideaki Nakamura, Seiji Okada, Eisaburo Sueoka, Shinya Kimura.

Adult T cell leukemia/lymphoma (ATL) is triggered by infection with human T cell lymphotropic virus-1 (HTLV-1). Here, we describe the reprogramming of pyrimidine biosynthesis in both normal T cells and ATL cells through regulation of uridine-cytidine kinase 2 (UCK2), which supports vigorous proliferation. UCK2 catalyzes mono-phosphorylation of cytidine/uridine and their analogues, during pyrimidine biosynthesis and drug metabolism. We found that UCK2 was overexpressed aberrantly in HTLV-1-infected T cells, but not in normal T cells. T cell activation via T cell receptor (TCR) signaling induced expression of UCK2 in normal T cells. Somatic alterations and epigenetic modifications in ATL cells activate TCR signaling. Therefore, we believe that expression of UCK2 in HTLV-1-infected cells is induced by dysregulated TCR signaling. Recently, we established azacitidine-resistant (AZA-R) cells showing absent expression of UCK2. AZA-R cells proliferated normally in vitro, whereas UCK2 knockdown inhibited the ATL cell growth. Although uridine and cytidine accumulated in AZA-R cells, possibly due to dysfunction of pyrimidine salvage biosynthesis induced by loss of UCK2 expression, the amount of UTP and CTP was almost the same as in parental cells. Furthermore, AZA-R cells were more susceptible to an inhibitor of dihydroorotic acid dehydrogenase, which performs the rate-limiting enzyme of de novo pyrimidine nucleotide biosynthesis, and more resistant to dipyridamole, an inhibitor of pyrimidine salvage biosynthesis, suggesting that AZA-R cells adapt to UCK2 loss by increasing de novo pyrimidine nucleotide biosynthesis. Taken together, the data suggest that fine-tuning pyrimidine biosynthesis supports vigorous cell proliferation of both normal T cells and ATL cells.

DOI: https://doi.org/10.1182/bloodadvances.2023011131
J Biol Chem. 2024 Jan 08. pii: S0021-9258(24)00008-5. [Epub ahead of print] 105632

Bakuchiol targets mitochondrial proteins, prohibitins and voltage-dependent anion channels: new insights into developing anti-viral agents.

Masaki Shoji, Tomoyuki Esumi, Takeshi Masuda, Narue Tanaka, Risa Okamoto, Hinako Sato, Mihiro Watanabe, Etsuhisa Takahashi, Hiroshi Kido, Sumio Ohtsuki, Takashi Kuzuhara.

  We previously reported that bakuchiol, a phenolic isoprenoid anti-cancer compound, and its analogs exert anti-influenza activity. However, the proteins targeted by bakuchiol remain unclear. Here, we investigated the chemical structures responsible for the anti-influenza activity of bakuchiol and found that all functional groups and C6 chirality of bakuchiol were required for its anti-influenza activity. Based on these results, we synthesized a molecular probe containing a biotin tag bound to the C1 position of bakuchiol. With this probe, we performed a pulldown assay for Madin-Darby canine kidney (MDCK) cell lysates and purified the specific bakuchiol-binding proteins with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Using nano-liquid chromatography with tandem mass spectrometry analysis, we identified prohibitin (PHB) 2, voltage dependent anion channel (VDAC) 1, and VDAC2 as binding proteins of bakuchiol. We confirmed the binding of bakuchiol to PHB1, PHB2, and VDAC2 in vitro using western blot analysis. Immunofluorescence analysis showed that bakuchiol was bound to PHBs and VDAC2 in cells and co-localized in the mitochondria. The knockdown of PHBs or VDAC2 by transfection with specific siRNAs, along with bakuchiol cotreatment, led to significantly reduced influenza nucleoprotein (NP) expression levels and viral titers in the conditioned medium of virus-infected MDCK cells, compared to the levels observed with transfection or treatment alone. These findings indicate that reducing PHBs or VDAC2 protein, combined with bakuchiol treatment, additively suppressed the growth of influenza virus. Our findings indicate that bakuchiol exerts anti-influenza activity via a novel mechanism involving these mitochondrial proteins, providing new insight for developing anti-influenza agents.

Keywords:  bakuchiol; influenza A virus; prohibitin; target protein; voltage-dependent anion channel

DOI:  https://doi.org/10.1016/j.jbc.2024.105632
FASEB J. 2024 Jan 31. 38(2): e23404

Acute endoplasmic reticulum stress-induced mitochondria respiratory chain damage: The role of activated calpains.

Qun Chen, Ling Li, Arun Samidurai, Jeremy Thompson, Ying Hu, Belinda Willard, Edward J Lesnefsky.

  The induction of acute endoplasmic reticulum (ER) stress damages the electron transport chain (ETC) in cardiac mitochondria. Activation of mitochondria-localized calpain 1 (CPN1) and calpain 2 (CPN2) impairs the ETC in pathological conditions, including aging and ischemia-reperfusion in settings where ER stress is increased. We asked if the activation of calpains causes the damage to the ETC during ER stress. Control littermate and CPNS1 (calpain small regulatory subunit 1) deletion mice were used in the current study. CPNS1 is an essential subunit required to maintain CPN1 and CPN2 activities, and deletion of CPNS1 prevents their activation. Tunicamycin (TUNI, 0.4 mg/kg) was used to induce ER stress in C57BL/6 mice. Cardiac mitochondria were isolated after 72 h of TUNI treatment. ER stress was increased in both control littermate and CPNS1 deletion mice with TUNI treatment. The TUNI treatment activated both cytosolic and mitochondrial CPN1 and 2 (CPN1/2) in control but not in CPNS1 deletion mice. TUNI treatment led to decreased oxidative phosphorylation and complex I activity in control but not in CPNS1 deletion mice compared to vehicle. The contents of complex I subunits, including NDUFV2 and ND5, were decreased in control but not in CPNS1 deletion mice. TUNI treatment also led to decreased oxidation through cytochrome oxidase (COX) only in control mice. Proteomic study showed that subunit 2 of COX was decreased in control but not in CPNS1 deletion mice. Our results provide a direct link between activation of CPN1/2 and complex I and COX damage during acute ER stress.

Keywords:  calpain 1; calpain 2; complex I; cytochrome oxidase; tunicamycin

DOI:  https://doi.org/10.1096/fj.202301158RR
Sci Rep. 2024 01 09. 14(1): 909

Mitofusin 1 silencing decreases the senescent associated secretory phenotype, promotes immune cell recruitment and delays melanoma tumor growth after chemotherapy.

Doménica Tarallo, Jennyfer Martínez, Alejandro Leyva, Amy Mónaco, Carolina Perroni, Marcos Tassano, Juan Pablo Gambini, Mónica Cappetta, Rosario Durán, María Moreno, Celia Quijano.

Cellular senescence is a therapy endpoint in melanoma, and the senescence-associated secretory phenotype (SASP) can affect tumor growth and microenvironment, influencing treatment outcomes. Metabolic interventions can modulate the SASP, and mitochondrial energy metabolism supports resistance to therapy in melanoma. In a previous report we showed that senescence, induced by the DNA methylating agent temozolomide, increased the level of fusion proteins mitofusin 1 and 2 in melanoma, and silencing Mfn1 or Mfn2 expression reduced interleukin-6 secretion by senescent cells. Here we expanded these observations evaluating the secretome of senescent melanoma cells using shotgun proteomics, and explored the impact of silencing Mfn1 on the SASP. A significant increase in proteins reported to reduce the immune response towards the tumor was found in the media of senescent cells. The secretion of several of these immunomodulatory proteins was affected by Mfn1 silencing, among them was galectin-9. In agreement, tumors lacking mitofusin 1 responded better to treatment with the methylating agent dacarbazine, tumor size was reduced and a higher immune cell infiltration was detected in the tumor. Our results highlight mitochondrial dynamic proteins as potential pharmacological targets to modulate the SASP in the context of melanoma treatment.

DOI: https://doi.org/10.1038/s41598-024-51427-7