bims-mibica 2024-03-31 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2024–03–31
thirty papers selected by
Kelsey Fisher-Wellman, East Carolina University

Complex I activity in hypoxia: implications for oncometabolism.
IF1 Promotes Cellular Proliferation and Inhibits Oxidative Phosphorylation in Mouse Embryonic Fibroblasts under Normoxia and Hypoxia.
BCAA metabolism in pancreatic cancer affects lipid balance by regulating fatty acid import into mitochondria.
Tumour immunogenicity goes with the (mitochondrial electron) flow.
Platinum iodido drugs show potential anti-tumor activity, affecting cancer cell metabolism and inducing ROS and senescence in gastrointestinal cancer cells.
Mitophagy mediated by BNIP3 and NIX protects against ferroptosis by downregulating mitochondrial reactive oxygen species.
A stagewise response to mitochondrial dysfunction in mitochondrial DNA maintenance disorders.
Getting more bang for their buck: BCL2 inhibitors boost dendritic-cell function to enhance anti-cancer immune surveillance.
Olutasidenib in post-venetoclax patients with mutant isocitrate dehydrogenase 1 (mIDH1) acute myeloid leukemia (AML).
Pyrimidines maintain mitochondrial pyruvate oxidation to support de novo lipogenesis.
Distinct types of intramitochondrial protein aggregates protect mitochondria against proteotoxic stress.
PROTAC-Mediated Dual Degradation of BCL-xL and BCL-2 Is a Highly Effective Therapeutic Strategy in Small-Cell Lung Cancer.
Mitochondrial H2O2 release does not directly cause damage to chromosomal DNA.
Thioredoxin is a metabolic rheostat controlling regulatory B cells.
Solute Transport through Mitochondrial Porins In Vitro and In Vivo.
Cyclin dependent kinase 4/6 inhibitor palbociclib synergizes with BCL2 inhibitor venetoclax in experimental models of mantle cell lymphoma without RB1 deletion.
Force-induced tail-autotomy mitochondrial fission and biogenesis of matrix-excluded mitochondrial-derived vesicles for quality control.
Malate, a natural inhibitor of 6PGD, improves the efficacy of chemotherapy in lung cancer.
BCL-2 inhibition in haematological malignancies: Clinical application and complications.
Emerging mechanisms in the redox regulation of mitochondrial cytochrome c oxidase assembly and function.
Precision mitochondrial medicine.
The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis.
NSAID targets SIRT3 to trigger mitochondrial dysfunction and gastric cancer cell death.
Glutamine antagonist DRP-104 suppresses tumor growth and enhances response to checkpoint blockade in KEAP1 mutant lung cancer.
SIRT3 and SIRT4 double-genes remodeled the mitochondrial network to induce hepatocellular carcinoma cell line differentiation and suppress malignant phenotypes.
Effective Targeting of Melanoma Cells by Combination of Mcl-1 and Bcl-2/Bcl-xL/Bcl-w Inhibitors.
Embracing cancer complexity: Hallmarks of systemic disease.
Cladribine plus cytarabine plus venetoclax in acute myeloid leukemia relapsed or refractory to venetoclax plus hypomethylating agent.
Phosphorylations and Acetylations of Cytochrome c Control Mitochondrial Respiration, Mitochondrial Membrane Potential, Energy, ROS, and Apoptosis.
AMPK inhibition sensitizes acute leukemia cells to BH3 mimetic-induced cell death.

Biochem Soc Trans. 2024 Mar 25. pii: BST20230189. [Epub ahead of print]

Complex I activity in hypoxia: implications for oncometabolism.

Christos Chinopoulos.

  Certain cancer cells within solid tumors experience hypoxia, rendering them incapable of oxidative phosphorylation (OXPHOS). Despite this oxygen deficiency, these cells exhibit biochemical pathway activity that relies on NAD+. This mini-review scrutinizes the persistent, residual Complex I activity that oxidizes NADH in the absence of oxygen as the electron acceptor. The resulting NAD+ assumes a pivotal role in fueling the α-ketoglutarate dehydrogenase complex, a critical component in the oxidative decarboxylation branch of glutaminolysis - a hallmark oncometabolic pathway. The proposition is that through glutamine catabolism, high-energy phosphate intermediates are produced via substrate-level phosphorylation in the mitochondrial matrix substantiated by succinyl-CoA ligase, partially compensating for an OXPHOS deficiency. These insights provide a rationale for exploring Complex I inhibitors in cancer treatment, even when OXPHOS functionality is already compromised.

Keywords:  OXPHOS; cancer; hypoxia; mitochondria; mtSLP

DOI:  https://doi.org/10.1042/BST20230189
Cells. 2024 Mar 21. pii: 551. [Epub ahead of print]13(6):

IF1 Promotes Cellular Proliferation and Inhibits Oxidative Phosphorylation in Mouse Embryonic Fibroblasts under Normoxia and Hypoxia.

Lothar Lauterboeck, Sung Wook Kang, Donnell White, Rong Bao, Parnia Mobasheran, Qinglin Yang.

  ATP synthase inhibitory factor subunit 1 (IF1) is an inhibitory subunit of mitochondrial ATP synthase, playing a crucial role in regulating mitochondrial respiration and energetics. It is well-established that IF1 interacts with the F1 sector of ATP synthase to inhibit the reversal rotation and, thus, ATP hydrolysis. Recent evidence supports that IF1 also inhibits forward rotation or the ATP synthesis activity. Adding to the complexity, IF1 may also facilitate mitophagy and cristae formation. The implications of these complex actions of IF1 for cellular function remain obscure. In the present study, we found that IF1 expression was markedly upregulated in hypoxic MEFs relative to normoxic MEFs. We investigate how IF1 affects cellular growth and function in cultured mouse embryonic fibroblasts derived from mouse lines with systemic IF1 overexpression and knockout under normoxia and hypoxia. Cell survival and proliferation analyses revealed that IF1 overexpression exerted limited effects on cellular viability but substantially increased proliferation under normoxia, whereas it facilitated both cellular viability and proliferation under hypoxia. The absence of IF1 may have a pro-survival effect but not a proliferative one in both normoxia and hypoxia. Cellular bioenergetic analyses revealed that IF1 suppressed cellular respiration when subjected to normoxia and was even more pronounced when subjected to hypoxia with increased mitochondrial ATP production. In contrast, IF1 knockout MEFs showed markedly increased cellular respiration under both normoxia and hypoxia with little change in mitochondrial ATP. Glycolytic stress assay revealed that IF1 overexpression modestly increased glycolysis in normoxia and hypoxia. Interestingly, the absence of IF1 in MEFs led to substantial increases in glycolysis. Therefore, we conclude that IF1 mainly inhibits cellular respiration and enhances cellular glycolysis to preserve mitochondrial ATP. On the other hand, IF1 deletion can significantly facilitate cellular respiration and glycolysis without leading to mitochondrial ATP deficit.

Keywords:  ATP; ATP synthase inhibitory factor subunit 1; cell proliferation; cellular glycolysis; cellular respiration; cellular viability; mitochondria; mouse embryonic fibroblasts

DOI:  https://doi.org/10.3390/cells13060551
Cancer Metab. 2024 Mar 26. 12(1): 10

BCAA metabolism in pancreatic cancer affects lipid balance by regulating fatty acid import into mitochondria.

Klára Gotvaldová, Jitka Špačková, Jiří Novotný, Kamila Baslarová, Petr Ježek, Lenka Rossmeislová, Jan Gojda, Katarína Smolková.

   BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) has been associated with the host dysmetabolism of branched-chain amino acids (BCAAs), however, the implications for the role of BCAA metabolism in PDAC development or progression are not clear. The mitochondrial catabolism of valine, leucine, and isoleucine is a multistep process leading to the production of short-chain R-CoA species. They can be subsequently exported from mitochondria as short-chain carnitines (SC-CARs), utilized in anabolic pathways, or released from the cells.
METHODS: We examined the specificities of BCAA catabolism and cellular adaptation strategies to BCAA starvation in PDAC cells in vitro. We used metabolomics and lipidomics to quantify major metabolic changes in response to BCAA withdrawal. Using confocal microscopy and flow cytometry we quantified the fluorescence of BODIPY probe and the level of lipid droplets (LDs). We used BODIPY-conjugated palmitate to evaluate transport of fatty acids (FAs) into mitochondria. Also, we have developed a protocol for quantification of SC-CARs, BCAA-derived metabolites.
RESULTS: Using metabolic profiling, we found that BCAA starvation leads to massive triglyceride (TG) synthesis and LD accumulation. This was associated with the suppression of activated FA transport into the mitochondrial matrix. The suppression of FA import into mitochondria was rescued with the inhibitor of the acetyl-CoA carboxylase (ACC) and the activator of AMP kinase (AMPK), which both regulate carnitine palmitoyltransferase 1A (CPT1) activation status.
CONCLUSIONS: Our data suggest that BCAA catabolism is required for the import of long chain carnitines (LC-CARs) into mitochondria, whereas the disruption of this link results in the redirection of activated FAs into TG synthesis and its deposition into LDs. We propose that this mechanism protects cells against mitochondrial overload with LC-CARs and it might be part of the universal reaction to amino acid perturbations during cancer growth, regulating FA handling and storage.

Keywords:  BCAA metabolism; Fatty acid/Transport; Fluorescence microscopy; Lipid droplets; Lipidomics; Mitochondria; Pancreatic cancer; Triglycerides

DOI:  https://doi.org/10.1186/s40170-024-00335-5
Mol Oncol. 2024 Mar 22.

Tumour immunogenicity goes with the (mitochondrial electron) flow.

Asma Ahmed, Stephen W G Tait.

  Mitochondrial metabolism and electron transport chain (ETC) function are essential for tumour proliferation and metastasis. However, the impact of ETC function on cancer immunogenicity is not well understood. In a recent study, Mangalhara et al. found that inhibition of complex II leads to enhanced tumour immunogenicity, T-cell-mediated cytotoxicity and inhibition of tumour growth. Surprisingly, this antitumour effect is mediated by succinate accumulation affecting histone methylation. Histone methylation promotes the transcriptional upregulation of major histocompatibility complex-antigen processing and presentation (MHC-APP) genes in a manner independent of interferon signalling. Modulating mitochondrial electron flow to enhance tumour immunogenicity provides an exciting new therapeutic avenue and may be particularly attractive for tumours with reduced expression of MHC-APP genes or dampened interferon signalling.

Keywords:  complex II; electron transport chain; major histocompatibility complex class I; succinate

DOI:  https://doi.org/10.1002/1878-0261.13627
Commun Biol. 2024 Mar 22. 7(1): 353

Platinum iodido drugs show potential anti-tumor activity, affecting cancer cell metabolism and inducing ROS and senescence in gastrointestinal cancer cells.

Jorge Melones-Herrero, Sonia Alcalá, Laura Ruiz-Cañas, Carlos Benítez-Buelga, Sandra Batres-Ramos, Carmela Calés, Oscar Lorenzo, Rosario Perona, Adoración G Quiroga, Bruno Sainz, Isabel Sánchez-Pérez.

Cisplatin-based chemotherapy has associated clinical disadvantages, such as high toxicity and resistance. Thus, the development of new antitumor metallodrugs able to overcome different clinical barriers is a public healthcare priority. Here, we studied the mechanism of action of the isomers trans and cis-[PtI2(isopropylamine)2] (I5 and I6, respectively) against gastrointestinal cancer cells. We demonstrate that I5 and I6 modulate mitochondrial metabolism, decreasing OXPHOS activity and negatively affecting ATP-linked oxygen consumption rate. Consequently, I5 and I6 generated Reactive Oxygen Species (ROS), provoking oxidative damage and eventually the induction of senescence. Thus, herein we propose a loop with three interconnected processes modulated by these iodido agents: (i) mitochondrial dysfunction and metabolic disruptions; (ii) ROS generation and oxidative damage; and (iii) cellular senescence. Functionally, I5 reduces cancer cell clonogenicity and tumor growth in a pancreatic xenograft model without systemic toxicity, highlighting a potential anticancer complex that warrants additional pre-clinical studies.

DOI: https://doi.org/10.1038/s42003-024-06052-5
Cell Death Differ. 2024 Mar 22.

Mitophagy mediated by BNIP3 and NIX protects against ferroptosis by downregulating mitochondrial reactive oxygen species.

Shun-Ichi Yamashita, Yuki Sugiura, Yuta Matsuoka, Rae Maeda, Keiichi Inoue, Kentaro Furukawa, Tomoyuki Fukuda, David C Chan, Tomotake Kanki.

Mitophagy plays an important role in the maintenance of mitochondrial homeostasis and can be categorized into two types: ubiquitin-mediated and receptor-mediated pathways. During receptor-mediated mitophagy, mitophagy receptors facilitate mitophagy by tethering the isolation membrane to mitochondria. Although at least five outer mitochondrial membrane proteins have been identified as mitophagy receptors, their individual contribution and interrelationship remain unclear. Here, we show that HeLa cells lacking BNIP3 and NIX, two of the five receptors, exhibit a complete loss of mitophagy in various conditions. Conversely, cells deficient in the other three receptors show normal mitophagy. Using BNIP3/NIX double knockout (DKO) cells as a model, we reveal that mitophagy deficiency elevates mitochondrial reactive oxygen species (mtROS), which leads to activation of the Nrf2 antioxidant pathway. Notably, BNIP3/NIX DKO cells are highly sensitive to ferroptosis when Nrf2-driven antioxidant enzymes are compromised. Moreover, the sensitivity of BNIP3/NIX DKO cells is fully rescued upon the introduction of wild-type BNIP3 and NIX, but not the mutant forms incapable of facilitating mitophagy. Consequently, our results demonstrate that BNIP3 and NIX-mediated mitophagy plays a role in regulating mtROS levels and protects cells from ferroptosis.

DOI: https://doi.org/10.1038/s41418-024-01280-y
Biochim Biophys Acta Mol Basis Dis. 2024 Mar 21. pii: S0925-4439(24)00120-0. [Epub ahead of print] 167131

A stagewise response to mitochondrial dysfunction in mitochondrial DNA maintenance disorders.

Amy E Vincent, Chun Chen, Tiago Bernardino Gomes, Valeria Di Leo, Tuomas Laalo, Kamil Pabis, Rodrick Capaldi, Michael F Marusich, David McDonald, Andrew Filby, Andrew Fuller, Diana Lehmann Urban, Stephan Zierz, Marcus Deschauer, Doug Turnbull, Amy K Reeve, Conor Lawless.

  Mitochondrial DNA (mtDNA) deletions which clonally expand in skeletal muscle of patients with mtDNA maintenance disorders, impair mitochondrial oxidative phosphorylation dysfunction. Previously we have shown that these mtDNA deletions arise and accumulate in perinuclear mitochondria causing localised mitochondrial dysfunction before spreading through the muscle fibre. We believe that mito-nuclear signalling is a key contributor in the accumulation and spread of mtDNA deletions, and that knowledge of how muscle fibres respond to mitochondrial dysfunction is key to our understanding of disease mechanisms. To understand the contribution of mito-nuclear signalling to the spread of mitochondrial dysfunction, we use imaging mass cytometry. We characterise the levels of mitochondrial Oxidative Phosphorylation proteins alongside a mitochondrial mass marker, in a cohort of patients with mtDNA maintenance disorders. Our expanded panel included protein markers of key signalling pathways, allowing us to investigate cellular responses to different combinations of oxidative phosphorylation dysfunction and ragged red fibres. We find combined Complex I and IV deficiency to be most common. Interestingly, in fibres deficient for one or more complexes, the remaining complexes are often upregulated beyond the increase of mitochondrial mass typically observed in ragged red fibres. We further find that oxidative phosphorylation deficient fibres exhibit an increase in the abundance of proteins involved in proteostasis, e.g. HSP60 and LONP1, and regulation of mitochondrial metabolism (including oxidative phosphorylation and proteolysis, e.g. PHB1). Our analysis suggests that the cellular response to mitochondrial dysfunction changes depending on the combination of deficient oxidative phosphorylation complexes in each fibre.

Keywords:  Cell signalling; Mitochondrial DNA deletion; Mitochondrial disease; Myopathy; OXPHOS

DOI:  https://doi.org/10.1016/j.bbadis.2024.167131
J Transl Med. 2024 Mar 28. 22(1): 317

Getting more bang for their buck: BCL2 inhibitors boost dendritic-cell function to enhance anti-cancer immune surveillance.

Alfredo E Montes-Gómez, Stephen W G Tait.

  The anti-apoptotic BCL-2 protein family regulates cancer cell survival, thus it represents an important therapeutic target. Indeed, a drug class, called BH3-mimetics, have been developed to directly target BCL2 proteins and promote cancer cell death. Conventional wisdom suggests that the primary anti-cancer effect of BCL-2 inhibition is through induction of cancer cell death. However, a recent study by Zhao and colleagues describes that BCL-2 inhibition also enhances the function of classical dendritic cells, unleashing their role in immunosurveillance, promoting T cell immunity and tumour regression. Thus, inhibiting anti-apoptotic BCL-2 function may have a multi-pronged anti-tumour action.

Keywords:  BCL-2; BH3 mimetics; DC maturation; Dendritic cells; Immune checkpoint inhibitors; Interferons; Venetoclax

DOI:  https://doi.org/10.1186/s12967-024-04961-x
Leuk Lymphoma. 2024 Mar 27. 1-8

Olutasidenib in post-venetoclax patients with mutant isocitrate dehydrogenase 1 (mIDH1) acute myeloid leukemia (AML).

Jorge Cortes, Brian A Jonas, Gary Schiller, Alice Mims, Gail J Roboz, Andrew H Wei, Pau Montesinos, P Brent Ferrell, Karen Wl Yee, Pierre Fenaux, Anthony Schwarer, Justin M Watts.

  Olutasidenib, a potent, selective, oral, mutant isocitrate dehydrogenase 1 (mIDH1) inhibitor, is FDA-approved for relapsed/refractory (R/R) acute myeloid leukemia (AML). Here we report efficacy and safety of olutasidenib in 18 patients with mIDH1 AML who were relapsed (10), refractory (6) or had complete remission with incomplete hematologic recovery (CRi; 2) to a venetoclax combination. Of the 16 patients who were R/R, 4 (25%) achieved complete remission (CR), one (6.3%) achieved CR with partial hematologic recovery (CRh), and 7 (43.8%) achieved a composite complete remission (CRc). Median time to CRc was 1.9 months (range 1-2.8). As of data cutoff (18 June 2021), median duration of CRc was not reached (range, 1.2-NR, ongoing at 30.4+ months). Both patients with CRi at study entry achieved a CR. Safety was consistent with the overall profile of olutasidenib. Olutasidenib offers a valuable treatment option for patients with mIDH1 AML previously treated with venetoclax.

Keywords:  IDH1 mutation; Olutasidenib; acute myeloid leukemia

DOI:  https://doi.org/10.1080/10428194.2024.2333451
Science. 2024 Mar 29. 383(6690): 1484-1492

Pyrimidines maintain mitochondrial pyruvate oxidation to support de novo lipogenesis.

Umakant Sahu, Elodie Villa, Colleen R Reczek, Zibo Zhao, Brendan P O'Hara, Michael D Torno, Rohan Mishra, William D Shannon, John M Asara, Peng Gao, Ali Shilatifard, Navdeep S Chandel, Issam Ben-Sahra.

Cellular purines, particularly adenosine 5'-triphosphate (ATP), fuel many metabolic reactions, but less is known about the direct effects of pyrimidines on cellular metabolism. We found that pyrimidines, but not purines, maintain pyruvate oxidation and the tricarboxylic citric acid (TCA) cycle by regulating pyruvate dehydrogenase (PDH) activity. PDH activity requires sufficient substrates and cofactors, including thiamine pyrophosphate (TPP). Depletion of cellular pyrimidines decreased TPP synthesis, a reaction carried out by TPP kinase 1 (TPK1), which reportedly uses ATP to phosphorylate thiamine (vitamin B1). We found that uridine 5'-triphosphate (UTP) acts as the preferred substrate for TPK1, enabling cellular TPP synthesis, PDH activity, TCA-cycle activity, lipogenesis, and adipocyte differentiation. Thus, UTP is required for vitamin B1 utilization to maintain pyruvate oxidation and lipogenesis.

DOI: https://doi.org/10.1126/science.adh2771
Cell Rep. 2024 Mar 28. pii: S2211-1247(24)00346-2. [Epub ahead of print]43(4): 114018

Distinct types of intramitochondrial protein aggregates protect mitochondria against proteotoxic stress.

Lea Bertgen, Jan-Eric Bökenkamp, Tim Schneckmann, Christian Koch, Markus Räschle, Zuzana Storchová, Johannes M Herrmann.

  Mitochondria consist of hundreds of proteins, most of which are inaccessible to the proteasomal quality control system of the cytosol. How cells stabilize the mitochondrial proteome during challenging conditions remains poorly understood. Here, we show that mitochondria form spatially defined protein aggregates as a stress-protecting mechanism. Two different types of intramitochondrial protein aggregates can be distinguished. The mitoribosomal protein Var1 (uS3m) undergoes a stress-induced transition from a soluble, chaperone-stabilized protein that is prevalent under benign conditions to an insoluble, aggregated form upon acute stress. The formation of Var1 bodies stabilizes mitochondrial proteostasis, presumably by sequestration of aggregation-prone proteins. The AAA chaperone Hsp78 is part of a second type of intramitochondrial aggregate that transiently sequesters proteins and promotes their folding or Pim1-mediated degradation. Thus, mitochondrial proteins actively control the formation of distinct types of intramitochondrial protein aggregates, which cooperate to stabilize the mitochondrial proteome during proteotoxic stress conditions.

Keywords:  CP: Cell biology; CP: Molecular biology; Hsp78; MitoStores; Pim1 protease; Var1 bodies; aggregates; chaperones; mitochondria; mitoribosome; protein folding; protein import

DOI:  https://doi.org/10.1016/j.celrep.2024.114018
Cells. 2024 Mar 17. pii: 528. [Epub ahead of print]13(6):

PROTAC-Mediated Dual Degradation of BCL-xL and BCL-2 Is a Highly Effective Therapeutic Strategy in Small-Cell Lung Cancer.

Sajid Khan, Lin Cao, Janet Wiegand, Peiyi Zhang, Maria Zajac-Kaye, Frederic J Kaye, Guangrong Zheng, Daohong Zhou.

  BCL-xL and BCL-2 are validated therapeutic targets in small-cell lung cancer (SCLC). Targeting these proteins with navitoclax (formerly ABT263, a dual BCL-xL/2 inhibitor) induces dose-limiting thrombocytopenia through on-target BCL-xL inhibition in platelets. Therefore, platelet toxicity poses a barrier in advancing the clinical translation of navitoclax. We have developed a strategy to selectively target BCL-xL in tumors, while sparing platelets, by utilizing proteolysis-targeting chimeras (PROTACs) that hijack the cellular ubiquitin proteasome system for target ubiquitination and subsequent degradation. In our previous study, the first-in-class BCL-xL PROTAC, called DT2216, was shown to have synergistic antitumor activities when combined with venetoclax (formerly ABT199, BCL-2-selective inhibitor) in a BCL-xL/2 co-dependent SCLC cell line, NCI-H146 (hereafter referred to as H146), in vitro and in a xenograft model. Guided by these findings, we evaluated our newly developed BCL-xL/2 dual degrader, called 753b, in three BCL-xL/2 co-dependent SCLC cell lines and the H146 xenograft models. 753b was found to degrade both BCL-xL and BCL-2 in these cell lines. Importantly, it was considerably more potent than DT2216, navitoclax, or DT2216 + venetoclax in reducing the viability of BCL-xL/2 co-dependent SCLC cell lines in cell culture. In vivo, 5 mg/kg weekly dosing of 753b was found to lead to significant tumor growth delay, similar to the DT2216 + venetoclax combination in H146 xenografts, by degrading both BCL-xL and BCL-2. Additionally, 753b administration at 5 mg/kg every four days induced tumor regressions. At this dosage, 753b was well tolerated in mice, without observable induction of severe thrombocytopenia as seen with navitoclax, and no evidence of significant changes in mouse body weights. These results suggest that the BCL-xL/2 dual degrader could be an effective and safe therapeutic for a subset of SCLC patients, warranting clinical trials in future.

Keywords:  BCL-2; BCL-xL; PROTAC; apoptosis; small-cell lung cancer

DOI:  https://doi.org/10.3390/cells13060528
Nat Commun. 2024 Mar 28. 15(1): 2725

Mitochondrial H2O2 release does not directly cause damage to chromosomal DNA.

Daan M K van Soest, Paulien E Polderman, Wytze T F den Toom, Janneke P Keijer, Markus J van Roosmalen, Tim M F Leyten, Johannes Lehmann, Susan Zwakenberg, Sasha De Henau, Ruben van Boxtel, Boudewijn M T Burgering, Tobias B Dansen.

Reactive Oxygen Species (ROS) derived from mitochondrial respiration are frequently cited as a major source of chromosomal DNA mutations that contribute to cancer development and aging. However, experimental evidence showing that ROS released by mitochondria can directly damage nuclear DNA is largely lacking. In this study, we investigated the effects of H2O2 released by mitochondria or produced at the nucleosomes using a titratable chemogenetic approach. This enabled us to precisely investigate to what extent DNA damage occurs downstream of near- and supraphysiological amounts of localized H2O2. Nuclear H2O2 gives rise to DNA damage and mutations and a subsequent p53 dependent cell cycle arrest. Mitochondrial H2O2 release shows none of these effects, even at levels that are orders of magnitude higher than what mitochondria normally produce. We conclude that H2O2 released from mitochondria is unlikely to directly damage nuclear genomic DNA, limiting its contribution to oncogenic transformation and aging.

DOI: https://doi.org/10.1038/s41467-024-47008-x
Nat Immunol. 2024 Mar 29.

Thioredoxin is a metabolic rheostat controlling regulatory B cells.

Hannah F Bradford, Thomas C R McDonnell, Alexander Stewart, Andrew Skelton, Joseph Ng, Zara Baig, Franca Fraternali, Deborah Dunn-Walters, David A Isenberg, Adnan R Khan, Claudio Mauro, Claudia Mauri.

Metabolic programming is important for B cell fate, but the bioenergetic requirement for regulatory B (Breg) cell differentiation and function is unknown. Here we show that Breg cell differentiation, unlike non-Breg cells, relies on mitochondrial electron transport and homeostatic levels of reactive oxygen species (ROS). Single-cell RNA sequencing analysis revealed that TXN, encoding the metabolic redox protein thioredoxin (Trx), is highly expressed by Breg cells, unlike Trx inhibitor TXNIP which was downregulated. Pharmacological inhibition or gene silencing of TXN resulted in mitochondrial membrane depolarization and increased ROS levels, selectively suppressing Breg cell differentiation and function while favoring pro-inflammatory B cell differentiation. Patients with systemic lupus erythematosus (SLE), characterized by Breg cell deficiencies, present with B cell mitochondrial membrane depolarization, elevated ROS and fewer Trx+ B cells. Exogenous Trx stimulation restored Breg cells and mitochondrial membrane polarization in SLE B cells to healthy B cell levels, indicating Trx insufficiency underlies Breg cell impairment in patients with SLE.

DOI: https://doi.org/10.1038/s41590-024-01798-w
Biomolecules. 2024 Mar 04. pii: 303. [Epub ahead of print]14(3):

Solute Transport through Mitochondrial Porins In Vitro and In Vivo.

Roland Benz.

  Mitochondria are most likely descendants of strictly aerobic prokaryotes from the class Alphaproteobacteria. The mitochondrial matrix is surrounded by two membranes according to its relationship with Gram-negative bacteria. Similar to the bacterial outer membrane, the mitochondrial outer membrane acts as a molecular sieve because it also contains diffusion pores. However, it is more actively involved in mitochondrial metabolism because it plays a functional role, whereas the bacterial outer membrane has only passive sieving properties. Mitochondrial porins, also known as eukaryotic porins or voltage-dependent anion-selective channels (VDACs) control the permeability properties of the mitochondrial outer membrane. They contrast with most bacterial porins because they are voltage-dependent. They switch at relatively small transmembrane potentials of 20 to 30 mV in closed states that exhibit different permeability properties than the open state. Whereas the open state is preferentially permeable to anionic metabolites of mitochondrial metabolism, the closed states prefer cationic solutes, in particular, calcium ions. Mitochondrial porins are encoded in the nucleus, synthesized at cytoplasmatic ribosomes, and post-translationally imported through special transport systems into mitochondria. Nineteen beta strands form the beta-barrel cylinders of mitochondrial and related porins. The pores contain in addition an α-helical structure at the N-terminal end of the protein that serves as a gate for the voltage-dependence. Similarly, they bind peripheral proteins that are involved in mitochondrial function and compartment formation. This means that mitochondrial porins are localized in a strategic position to control mitochondrial metabolism. The special features of the role of mitochondrial porins in apoptosis and cancer will also be discussed in this article.

Keywords:  VDAC; apoptosis; cancer; lipid bilayer; mitochondrial metabolism; mitochondrial porin; peripheral kinases; pore structure; voltage dependence

DOI:  https://doi.org/10.3390/biom14030303
Exp Hematol Oncol. 2024 Mar 25. 13(1): 34

Cyclin dependent kinase 4/6 inhibitor palbociclib synergizes with BCL2 inhibitor venetoclax in experimental models of mantle cell lymphoma without RB1 deletion.

Diana Malarikova, Radek Jorda, Kristyna Kupcova, Jana Senavova, Alexandra Dolnikova, Eva Pokorna, Dmitry Kazantsev, Kristina Nozickova, Dana Sovilj, Celine Bellanger, David Chiron, Ladislav Andera, Vladimir Krystof, Miroslav Strnad, Karel Helman, Magdalena Klanova, Marek Trneny, Ondrej Havranek, Pavel Klener.

   BACKGROUND: Mantle cell lymphoma (MCL) is a chronically relapsing malignancy with deregulated cell cycle progression. We analyzed efficacy, mode of action, and predictive markers of susceptibility to palbociclib, an approved CDK 4/6 inhibitor, and its combination with venetoclax, a BCL2 inhibitor.
METHODS: A panel of nine MCL cell lines were used for in vitro experiments. Four patient derived xenografts (PDX) obtained from patients with chemotherapy and ibrutinib-refractory MCL were used for in vivo proof-of-concept studies. Changes of the mitochondrial membrane potential, energy-metabolic pathways, AKT activity, and pro-apoptotic priming of MCL cells were evaluated by JC-1 staining, Seahorse XF analyser, genetically encoded fluorescent AKT reporter, and BH3 profiling, respectively. MCL clones with gene knockout or transgenic (over)expression of CDKN2A, MYC, CDK4, and RB1 were used to estimate impact of these aberrations on sensitivity to palbociclib, and venetoclax.
RESULTS: Co-targeting MCL cells with palbociclib and venetoclax induced cytotoxic synergy in vitro and in vivo. Molecular mechanisms responsible for the observed synthetic lethality comprised palbociclib-mediated downregulation of anti-apoptotic MCL1, increased levels of proapoptotic BIM bound on both BCL2, and BCL-XL and increased pro-apoptotic priming of MCL cells mediated by BCL2-independent mechanisms, predominantly palbociclib-triggered metabolic and mitochondrial stress. Loss of RB1 resulted in palbociclib resistance, while deletion of CDKN2A or overexpression of CDK4, and MYC genes did not change sensitivity to palbociclib.
CONCLUSIONS: Our data strongly support investigation of the chemotherapy-free palbociclib and venetoclax combination as an innovative treatment strategy for post-ibrutinib MCL patients without RB1 deletion.

Keywords:  BCL2; Cyclin-dependent kinase (CDK) inhibitors; Mantle cell lymphoma (MCL); Palbociclib; RB1; Venetoclax

DOI:  https://doi.org/10.1186/s40164-024-00499-2
Proc Natl Acad Sci U S A. 2024 Apr 02. 121(14): e2217019121

Force-induced tail-autotomy mitochondrial fission and biogenesis of matrix-excluded mitochondrial-derived vesicles for quality control.

Xiaoying Liu, Linyu Xu, Yutong Song, Zhihao Zhao, Xinyu Li, Cheuk-Yiu Wong, Rong Chen, Jianxiong Feng, Yitao Gou, Yajing Qi, Hei-Man Chow, Shuhuai Yao, Yi Wang, Song Gao, Xingguo Liu, Liting Duan.

  Mitochondria constantly fuse and divide for mitochondrial inheritance and functions. Here, we identified a distinct type of naturally occurring fission, tail-autotomy fission, wherein a tail-like thin tubule protrudes from the mitochondrial body and disconnects, resembling autotomy. Next, utilizing an optogenetic mitochondria-specific mechanostimulator, we revealed that mechanical tensile force drives tail-autotomy fission. This force-induced fission involves DRP1/MFF and endoplasmic reticulum tubule wrapping. It redistributes mitochondrial DNA, producing mitochondrial fragments with or without mitochondrial DNA for different fates. Moreover, tensile force can decouple outer and inner mitochondrial membranes, pulling out matrix-excluded tubule segments. Subsequent tail-autotomy fission separates the matrix-excluded tubule segments into matrix-excluded mitochondrial-derived vesicles (MDVs) which recruit Parkin and LC3B, indicating the unique role of tail-autotomy fission in segregating only outer membrane components for mitophagy. Sustained force promotes fission and MDV biogenesis more effectively than transient one. Our results uncover a mechanistically and functionally distinct type of fission and unveil the role of tensile forces in modulating fission and MDV biogenesis for quality control, underscoring the heterogeneity of fission and mechanoregulation of mitochondrial dynamics.

Keywords:  mitochondrial fission; mitochondrial quality control; optogenetics; photoactivatable proteins; tensile force

DOI:  https://doi.org/10.1073/pnas.2217019121
Lung Cancer. 2024 Mar 25. pii: S0169-5002(24)00074-6. [Epub ahead of print]190 107541

Malate, a natural inhibitor of 6PGD, improves the efficacy of chemotherapy in lung cancer.

Mingming Sun, Qi Feng, Qi Yan, Huifang Zhao, Haiyan Wang, Shuai Zhang, Changliang Shan, Shuangping Liu, Jiyan Wang, Hongyan Zhai.

   OBJECTIVE: Metabolic reprogramming is an important coordinator of tumor development and resistance to therapy, such as the tendency of tumor cells to utilize glycolytic energy rather than oxidative phosphorylation, even under conditions of sufficient oxygen. Therefore, targeting metabolic enzymes is an effective strategy to overcome therapeutic resistance.
MATERIALS AND METHODS: We explored the differential expression and growth-promoting function of MDH2 by immunohistochemistry and immunoblotting experiments in lung cancer patients and lung cancer cells. Pentose phosphate pathway-related phenotypes (including ROS levels, NADPH levels, and DNA synthesis) were detected intracellularly, and the interaction of malate and proteinase 6PGD was detected in vitro. In vivo experiments using implanted xenograft mouse models to explore the growth inhibitory effect and pro-chemotherapeutic function of dimethyl malate (DMM) on lung cancer.
RESULTS: We found that the expression of malate dehydrogenase (MDH2) in the tricarboxylic acid cycle (TCA cycle) was increased in lung cancer. Biological function enrichment analysis revealed that MDH2 not only promoted oxidative phosphorylation, but also promoted the pentose phosphate pathway (PPP pathway). Mechanistically, it was found that malate, the substrate of MDH2, can bind to the PPP pathway metabolic enzyme 6PGD, inhibit its activity, reduce the generation of NADPH, and block DNA synthesis. More importantly, DMM can improve the sensitivity of lung cancer to the clinical drug cisplatin.
CONCLUSION: We have identified malate as a natural inhibitor of 6PGD, which will provide new leads for the development of 6PGD inhibitors. In addition, the metabolic enzyme MDH2 and the metabolite malate may provide a backup option for cells to inhibit their own carcinogenesis, as the accumulated malate targets 6PGD to block the PPP pathway and inhibit cell cycle progression.

Keywords:  6PGD; Cisplatin; Malate; PPP pathway; TCA cycle

DOI:  https://doi.org/10.1016/j.lungcan.2024.107541
Blood Rev. 2024 Mar 21. pii: S0268-960X(24)00028-6. [Epub ahead of print] 101195

BCL-2 inhibition in haematological malignancies: Clinical application and complications.

Dominic J Fowler-Shorten, Charlotte Hellmich, Matthew Markham, Kristian M Bowles, Stuart A Rushworth.

  B-cell lymphoma-2 (BCL-2) family proteins are fundamental regulators of the intrinsic apoptotic pathway which modulate cellular fate. In many haematological malignancies, overexpression of anti-apoptotic factors (BCL-2, BCL-XL and MCL-1) circumvent apoptosis. To address this cancer hallmark, a concerted effort has been made to induce apoptosis by inhibiting BCL-2 family proteins. A series of highly selective BCL-2 homology 3 (BH3) domain mimetics are in clinical use and in ongoing clinical trials for acute myeloid leukaemia (AML), chronic myeloid leukaemia (CML), chronic lymphocytic leukaemia (CLL), and multiple myeloma (MM). These inhibitors serve as promising candidates, both as single agents or in combination therapy to improve patient outcomes. In other diseases such as follicular lymphoma, efficacy has been notably limited. There are also clinical problems with BCL-2 family inhibition, including drug resistance, disease relapse, tumour lysis syndrome, and clinically relevant cytopenias. Here, we provide a balanced view on both the clinical benefits of BCL-2 inhibition as well as the associated challenges.

Keywords:  BCL-2 family inhibitors; Cytopenias; Drug resistance; Haematological malignancies; Venetoclax

DOI:  https://doi.org/10.1016/j.blre.2024.101195
Biochem Soc Trans. 2024 Mar 25. pii: BST20231183. [Epub ahead of print]

Emerging mechanisms in the redox regulation of mitochondrial cytochrome c oxidase assembly and function.

Suleva Povea-Cabello, Michele Brischigliaro, Erika Fernández-Vizarra.

  In eukaryotic cells, mitochondria perform cellular respiration through a series of redox reactions ultimately reducing molecular oxygen to water. The system responsible for this process is the respiratory chain or electron transport system (ETS) composed of complexes I-IV. Due to its function, the ETS is the main source of reactive oxygen species (ROS), generating them on both sides of the mitochondrial inner membrane, i.e. the intermembrane space (IMS) and the matrix. A correct balance between ROS generation and scavenging is important for keeping the cellular redox homeostasis and other important aspects of cellular physiology. However, ROS generated in the mitochondria are important signaling molecules regulating mitochondrial biogenesis and function. The IMS contains a large number of redox sensing proteins, containing specific Cys-rich domains, that are involved in ETS complex biogenesis. The large majority of these proteins function as cytochrome c oxidase (COX) assembly factors, mainly for the handling of copper ions necessary for the formation of the redox reactive catalytic centers. A particular case of ROS-regulated COX assembly factor is COA8, whose intramitochondrial levels are increased by oxidative stress, promoting COX assembly and/or protecting the enzyme from oxidative damage. In this review, we will discuss the current knowledge concerning the role played by ROS in regulating mitochondrial activity and biogenesis, focusing on the COX enzyme and with a special emphasis on the functional role exerted by the redox sensitive Cys residues contained in the COX assembly factors.

Keywords:  complex IV; mitochondrial dysfunction; reactive oxygen species; redox signaling; respiratory chain assembly

DOI:  https://doi.org/10.1042/BST20231183
Camb Prism Precis Med. 2023 ;1 e6

Precision mitochondrial medicine.

Patrick F Chinnery.

  Mitochondria play a key role in cell homeostasis as a major source of intracellular energy (adenosine triphosphate), and as metabolic hubs regulating many canonical cell processes. Mitochondrial dysfunction has been widely documented in many common diseases, and genetic studies point towards a causal role in the pathogenesis of specific late-onset disorder. Together this makes targeting mitochondrial genes an attractive strategy for precision medicine. However, the genetics of mitochondrial biogenesis is complex, with over 1,100 candidate genes found in two different genomes: the nuclear DNA and mitochondrial DNA (mtDNA). Here, we review the current evidence associating mitochondrial genetic variants with distinct clinical phenotypes, with some having clear therapeutic implications. The strongest evidence has emerged through the investigation of rare inherited mitochondrial disorders, but genome-wide association studies also implicate mtDNA variants in the risk of developing common diseases, opening to door for the incorporation of mitochondrial genetic variant analysis in population disease risk stratification.

Keywords:  genetic polymorphism; genetic risk score; genetics; genomics; metabolic diseases

DOI:  https://doi.org/10.1017/pcm.2022.8
Cells. 2024 Mar 07. pii: 473. [Epub ahead of print]13(6):

The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis.

Fernanda L Basei, Ivan Rosa E Silva, Pedro R Firmino Dias, Camila C Ferezin, Andressa Peres de Oliveira, Luidy K Issayama, Livia A R Moura, Fernando Riback da Silva, Jörg Kobarg.

  Mitochondria provide energy for all cellular processes, including reactions associated with cell cycle progression, DNA damage repair, and cilia formation. Moreover, mitochondria participate in cell fate decisions between death and survival. Nek family members have already been implicated in DNA damage response, cilia formation, cell death, and cell cycle control. Here, we discuss the role of several Nek family members, namely Nek1, Nek4, Nek5, Nek6, and Nek10, which are not exclusively dedicated to cell cycle-related functions, in controlling mitochondrial functions. Specifically, we review the function of these Neks in mitochondrial respiration and dynamics, mtDNA maintenance, stress response, and cell death. Finally, we discuss the interplay of other cell cycle kinases in mitochondrial function and vice versa. Nek1, Nek5, and Nek6 are connected to the stress response, including ROS control, mtDNA repair, autophagy, and apoptosis. Nek4, in turn, seems to be related to mitochondrial dynamics, while Nek10 is involved with mitochondrial metabolism. Here, we propose that the participation of Neks in mitochondrial roles is a new functional axis for the Nek family.

Keywords:  Nek kinase family functions; cell cycle; cellular signaling; mitochondrial homeostasis

DOI:  https://doi.org/10.3390/cells13060473
iScience. 2024 Apr 19. 27(4): 109384

NSAID targets SIRT3 to trigger mitochondrial dysfunction and gastric cancer cell death.

Subhashis Debsharma, Saikat Pramanik, Samik Bindu, Somnath Mazumder, Troyee Das, Uttam Pal, Debanjan Saha, Rudranil De, Shiladitya Nag, Chinmoy Banerjee, Nakul Chandra Maiti, Zhumur Ghosh, Uday Bandyopadhyay.

  Gastric cancer (GC) is a deadly malignancy that demands effective therapeutic intervention capitalizing unique drug target/s. Here, we report that indomethacin, a cyclooxygenase non-selective non-steroidal anti-inflammatory drug, arrests GC cell growth by targeting mitochondrial deacetylase Sirtuin 3 (SIRT3). Interaction study revealed that indomethacin competitively inhibited SIRT3 by binding to nicotinamide adenine dinucleotide (NAD)-binding site. The Cancer Genome Atlas data meta-analysis indicated poor prognosis associated with high SIRT3 expression in GC. Further, transcriptome sequencing data of human gastric adenocarcinoma cells revealed that indomethacin treatment severely downregulated SIRT3. Indomethacin-induced SIRT3 downregulation augmented SOD2 and OGG1 acetylation, leading to mitochondrial redox dyshomeostasis, mtDNA damage, respiratory chain failure, bioenergetic crisis, mitochondrial fragmentation, and apoptosis via blocking the AMPK/PGC1α/SIRT3 axis. Indomethacin also downregulated SIRT3 regulators ERRα and PGC1α. Further, SIRT3 knockdown aggravated indomethacin-induced mitochondrial dysfunction as well as blocked cell-cycle progression to increase cell death. Thus, we reveal how indomethacin induces GC cell death by disrupting SIRT3 signaling.

Keywords:  Cancer; Cell biology

DOI:  https://doi.org/10.1016/j.isci.2024.109384
Sci Adv. 2024 Mar 29. 10(13): eadm9859

Glutamine antagonist DRP-104 suppresses tumor growth and enhances response to checkpoint blockade in KEAP1 mutant lung cancer.

Ray Pillai, Sarah E LeBoeuf, Yuan Hao, Connie New, Jenna L E Blum, Ali Rashidfarrokhi, Shih Ming Huang, Christian Bahamon, Warren L Wu, Burcu Karadal-Ferrena, Alberto Herrera, Ellie Ivanova, Michael Cross, Jozef P Bossowski, Hongyu Ding, Makiko Hayashi, Sahith Rajalingam, Triantafyllia Karakousi, Volkan I Sayin, Kamal M Khanna, Kwok-Kin Wong, Robert Wild, Aristotelis Tsirigos, John T Poirier, Charles M Rudin, Shawn M Davidson, Sergei B Koralov, Thales Papagiannakopoulos.

Loss-of-function mutations in KEAP1 frequently occur in lung cancer and are associated with poor prognosis and resistance to standard of care treatment, highlighting the need for the development of targeted therapies. We previously showed that KEAP1 mutant tumors consume glutamine to support the metabolic rewiring associated with NRF2-dependent antioxidant production. Here, using preclinical patient-derived xenograft models and antigenic orthotopic lung cancer models, we show that the glutamine antagonist prodrug DRP-104 impairs the growth of KEAP1 mutant tumors. We find that DRP-104 suppresses KEAP1 mutant tumors by inhibiting glutamine-dependent nucleotide synthesis and promoting antitumor T cell responses. Using multimodal single-cell sequencing and ex vivo functional assays, we demonstrate that DRP-104 reverses T cell exhaustion, decreases Tregs, and enhances the function of CD4 and CD8 T cells, culminating in an improved response to anti-PD1 therapy. Our preclinical findings provide compelling evidence that DRP-104, currently in clinical trials, offers a promising therapeutic approach for treating patients with KEAP1 mutant lung cancer.

DOI: https://doi.org/10.1126/sciadv.adm9859
Biochem Pharmacol. 2024 Mar 26. pii: S0006-2952(24)00151-5. [Epub ahead of print] 116168

SIRT3 and SIRT4 double-genes remodeled the mitochondrial network to induce hepatocellular carcinoma cell line differentiation and suppress malignant phenotypes.

Lijun Zhang, Zhenning Dai, Shanshan Shi, Zi Yan, Jiaxin Yang, Wanting Xue, Yunhao He, Siqi Mi, Cheng Cheng, Liangxu Wang, Nanxiang Li, Wei Tan, Zhenyou Jiang, Hanxiao Sun, Shiyu Li.

  Tumor cells with damaged mitochondria undergo metabolic reprogramming, but gene therapy targeting mitochondria has not been comprehensively reported. In this study, plasmids targeting the normal hepatocyte cell line (L-O2) and hepatocellular carcinoma cell line were generated using three genes SIRT3, SIRT4, and SIRT5. These deacetylases play a variety of regulatory roles in cancer and are related to mitochondrial function. Compared with L-O2, SIRT3 and SIRT4 significantly ameliorated mitochondrial damage in HCCLM3, Hep3B and HepG2 cell lines and regulated mitochondrial biogenesis and mitophagy, respectively. We constructed double-gene plasmid for co-express SIRT3 and SIRT4 using the internal ribosome entry site (IRES). The results indicated that the double-gene plasmid effectively expressed SIRT3 and SIRT4, significantly improved mitochondrial quality and function, and reduced mtDNA level and oxidative stress in HCC cells. MitoTracker analysis revealed that the mitochondrial network was restored. The proliferation, migration capabilities of HCC cells were reduced, whereas their differentiation abilities were enhanced. This study demonstrated that the use of IRES-linked SIRT3 and SIRT4 double-gene vectors induced the differentiation of HCC cells and inhibited their development by ameliorating mitochondrial dysfunction. This intervention helped reverse metabolic reprogramming, and may provide a groundbreaking new framework for HCC treatment.

Keywords:  Hepatocellular carcinoma; Metabolic reprogramming; Mitochondria; Plasmid; Sirtuin

DOI:  https://doi.org/10.1016/j.bcp.2024.116168
Int J Mol Sci. 2024 Mar 19. pii: 3453. [Epub ahead of print]25(6):

Effective Targeting of Melanoma Cells by Combination of Mcl-1 and Bcl-2/Bcl-xL/Bcl-w Inhibitors.

Zhe Peng, Bernhard Gillissen, Antje Richter, Tobias Sinnberg, Max S Schlaak, Jürgen Eberle.

  Recent advances in melanoma therapy have significantly improved the prognosis of metastasized melanoma. However, large therapeutic gaps remain that need to be closed by new strategies. Antiapoptotic Bcl-2 proteins critically contribute to apoptosis deficiency and therapy resistance. They can be targeted by BH3 mimetics, small molecule antagonists that mimic the Bcl-2 homology domain 3 (BH3) of proapoptotic BH3-only proteins. By applying in vitro experiments, we aimed to obtain an overview of the possible suitability of BH3 mimetics for future melanoma therapy. Thus, we investigated the effects of ABT-737 and ABT-263, which target Bcl-2, Bcl-xL and Bcl-w as well as the Bcl-2-selective ABT-199 and the Mcl-1-selective S63845, in a panel of four BRAF-mutated and BRAF-WT melanoma cell lines. None of the inhibitors showed significant effectiveness when used alone; however, combination of S63845 with each one of the three ABTs almost completely abolished melanoma cell survival and induced apoptosis in up to 50-90% of the cells. Special emphasis was placed here on the understanding of the downstream pathways involved, which may allow improved applications of these strategies. Thus, cell death induction was correlated with caspase activation, loss of mitochondrial membrane potential, phosphorylation of histone H2AX, and ROS production. Caspase dependency was demonstrated by a caspase inhibitor, which blocked all effects. Upregulation of Mcl-1, induced by S63845 itself, as reported previously, was blocked by the combinations. Indeed, Mcl-1, as well as XIAP (X-linked inhibitor of apoptosis), were strongly downregulated by combination treatments. These findings demonstrate that melanoma cells can be efficiently targeted by BH3 mimetics, but the right combinations have to be selected. The observed pronounced activation of apoptosis pathways demonstrates the decisive role of apoptosis in the loss of cell viability by BH3 mimetics.

Keywords:  BH3 mimetics; apoptosis induction; apoptotic pathways; melanoma; skin cancer; therapeutic strategies

DOI:  https://doi.org/10.3390/ijms25063453
Cell. 2024 Mar 28. pii: S0092-8674(24)00175-2. [Epub ahead of print]187(7): 1589-1616

Embracing cancer complexity: Hallmarks of systemic disease.

Charles Swanton, Elsa Bernard, Chris Abbosh, Fabrice André, Johan Auwerx, Allan Balmain, Dafna Bar-Sagi, René Bernards, Susan Bullman, James DeGregori, Catherine Elliott, Ayelet Erez, Gerard Evan, Mark A Febbraio, Andrés Hidalgo, Mariam Jamal-Hanjani, Johanna A Joyce, Matthew Kaiser, Katja Lamia, Jason W Locasale, Sherene Loi, Ilaria Malanchi, Miriam Merad, Kathryn Musgrave, Ketan J Patel, Sergio Quezada, Jennifer A Wargo, Ashani Weeraratna, Eileen White, Frank Winkler, John N Wood, Karen H Vousden, Douglas Hanahan.

The last 50 years have witnessed extraordinary developments in understanding mechanisms of carcinogenesis, synthesized as the hallmarks of cancer. Despite this logical framework, our understanding of the molecular basis of systemic manifestations and the underlying causes of cancer-related death remains incomplete. Looking forward, elucidating how tumors interact with distant organs and how multifaceted environmental and physiological parameters impinge on tumors and their hosts will be crucial for advances in preventing and more effectively treating human cancers. In this perspective, we discuss complexities of cancer as a systemic disease, including tumor initiation and promotion, tumor micro- and immune macro-environments, aging, metabolism and obesity, cancer cachexia, circadian rhythms, nervous system interactions, tumor-related thrombosis, and the microbiome. Model systems incorporating human genetic variation will be essential to decipher the mechanistic basis of these phenomena and unravel gene-environment interactions, providing a modern synthesis of molecular oncology that is primed to prevent cancers and improve patient quality of life and cancer outcomes.

DOI: https://doi.org/10.1016/j.cell.2024.02.009
Haematologica. 2024 Mar 28.

Cladribine plus cytarabine plus venetoclax in acute myeloid leukemia relapsed or refractory to venetoclax plus hypomethylating agent.

Nickolas Steinauer, Kristen McCullough, Aref Al-Kali, Hassan B Alkhateeb, Kebede H Begna, Abhishek A Mangaonkar, Antoine N Saliba, Mehrdad Torghabeh, Mark R Litzow, William J Hogan, Mithun Shah, Mrinal M Patnaik, Animesh Pardanani, Talha Badar, Hemant Murthy, James Foran, Cecilia Arana Yi, Ayalew Tefferi, Naseema Gangat.

Not available.

DOI: https://doi.org/10.3324/haematol.2024.284962
Cells. 2024 Mar 12. pii: 493. [Epub ahead of print]13(6):

Phosphorylations and Acetylations of Cytochrome c Control Mitochondrial Respiration, Mitochondrial Membrane Potential, Energy, ROS, and Apoptosis.

Paul T Morse, Tasnim Arroum, Junmei Wan, Lucynda Pham, Asmita Vaishnav, Jamie Bell, Lauren Pavelich, Moh H Malek, Thomas H Sanderson, Brian F P Edwards, Maik Hüttemann.

  Cytochrome c (Cytc) has both life-sustaining and cellular death-related functions, depending on subcellular localization. Within mitochondria, Cytc acts as a single electron carrier as part of the electron transport chain (ETC). When released into the cytosol after cellular insult, Cytc triggers the assembly of the apoptosome, committing the cell to intrinsic apoptosis. Due to these dual natures, Cytc requires strong regulation by the cell, including post-translational modifications, such as phosphorylation and acetylation. Six phosphorylation sites and three acetylation sites have been detected on Cytc in vivo. Phosphorylations at T28, S47, Y48, T49, T58, and Y97 tend to be present under basal conditions in a tissue-specific manner. In contrast, the acetylations at K8, K39, and K53 tend to be present in specific pathophysiological conditions. All of the phosphorylation sites and two of the three acetylation sites partially inhibit respiration, which we propose serves to maintain an optimal, intermediate mitochondrial membrane potential (ΔΨm) to minimize reactive oxygen species (ROS) production. Cytc phosphorylations are lost during ischemia, which drives ETC hyperactivity and ΔΨm hyperpolarization, resulting in exponential ROS production thus causing reperfusion injury following ischemia. One of the acetylation sites, K39, shows a unique behavior in that it is gained during ischemia, stimulating respiration while blocking apoptosis, demonstrating that skeletal muscle, which is particularly resilient to ischemia-reperfusion injury compared to other organs, possesses a different metabolic strategy to handle ischemic stress. The regulation of Cytc by these post-translational modifications underscores the importance of Cytc for the ETC, ΔΨm, ROS production, apoptosis, and the cell as a whole.

Keywords:  apoptosis; cytochrome c; electron transport chain; mitochondria; post-translational modifications; respiration

DOI:  https://doi.org/10.3390/cells13060493
Cell Death Differ. 2024 Mar 27.

AMPK inhibition sensitizes acute leukemia cells to BH3 mimetic-induced cell death.

Jia Jia, Wenbo Ji, Antoine N Saliba, Clifford M Csizmar, Kaiqin Ye, Lei Hu, Kevin L Peterson, Paula A Schneider, X Wei Meng, Annapoorna Venkatachalam, Mrinal M Patnaik, Jonathan A Webster, B Douglas Smith, Gabriel Ghiaur, Xinyan Wu, Jun Zhong, Akhilesh Pandey, Karen S Flatten, Qingmei Deng, Hongzhi Wang, Scott H Kaufmann, Haiming Dai.

BH3 mimetics, including the BCL2/BCLXL/BCLw inhibitor navitoclax and MCL1 inhibitors S64315 and tapotoclax, have undergone clinical testing for a variety of neoplasms. Because of toxicities, including thrombocytopenia after BCLXL inhibition as well as hematopoietic, hepatic and possible cardiac toxicities after MCL1 inhibition, there is substantial interest in finding agents that can safely sensitize neoplastic cells to these BH3 mimetics. Building on the observation that BH3 mimetic monotherapy induces AMP kinase (AMPK) activation in multiple acute leukemia cell lines, we report that the AMPK inhibitors (AMPKis) dorsomorphin and BAY-3827 sensitize these cells to navitoclax or MCL1 inhibitors. Cell fractionation and phosphoproteomic analyses suggest that sensitization by dorsomorphin involves dephosphorylation of the proapoptotic BCL2 family member BAD at Ser75 and Ser99, leading BAD to translocate to mitochondria and inhibit BCLXL. Consistent with these results, BAD knockout or mutation to BAD S75E/S99E abolishes the sensitizing effects of dorsomorphin. Conversely, dorsomorphin synergizes with navitoclax or the MCL1 inhibitor S63845 to induce cell death in primary acute leukemia samples ex vivo and increases the antitumor effects of navitoclax or S63845 in several xenograft models in vivo with little or no increase in toxicity in normal tissues. These results suggest that AMPK inhibition can sensitize acute leukemia to multiple BH3 mimetics, potentially allowing administration of lower doses while inducing similar antineoplastic effects.

DOI: https://doi.org/10.1038/s41418-024-01283-9