bims-mibica 2024-03-17 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2024–03–17
28 papers selected by
Kelsey Fisher-Wellman, East Carolina University

The ATPase Inhibitory Factor 1 (IF1) Contributes to the Warburg Effect and Is Regulated by Its Phosphorylation in S39 by a Protein Kinase A-like Activity.
Fatty acid oxidation drives mitochondrial hydrogen peroxide production by α-ketoglutarate dehydrogenase.
Mitochondrial metabolism sustains CD8+ T cell migration for an efficient infiltration into solid tumors.
Increased O-GlcNAcylation by Upregulation of Mitochondrial O-GlcNAc Transferase (mOGT) Inhibits the Activity of Respiratory Chain Complexes and Controls Cellular Bioenergetics.
FAM83B regulates mitochondrial metabolism and anti-apoptotic activity in pulmonary adenocarcinoma.
PRODH safeguards human naive pluripotency by limiting mitochondrial oxidative phosphorylation and reactive oxygen species production.
Yeast Bxi1/Ybh3 mediates conserved mitophagy and apoptosis in yeast and mammalian cells: convergence in Bcl-2 family.
PROTAC-mediated dual degradation of BCL-xL and BCL-2 is a highly effective therapeutic strategy in small-cell lung cancer.
Novel meriolin derivatives activate the mitochondrial apoptosis pathway in the presence of antiapoptotic Bcl-2.
NME3 is a gatekeeper for DRP1-dependent mitophagy in hypoxia.
Expression of Mitochondrial Long Non-Coding RNAs, MDL1 and MDL1AS, Are Good Prognostic and/or Diagnostic Biomarkers for Several Cancers, Including Colorectal Cancer.
13 C-SpaceM: Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer.
Targeting PARP14 with lomitapide suppresses drug resistance through the activation of DRP1-induced mitophagy in multiple myeloma.
A first-in-class TIMM44 blocker inhibits bladder cancer cell growth.
Targeting cuproplasia and cuproptosis in cancer.
The Ubiquitin Ligase RBX2/SAG Regulates Mitochondrial Ubiquitination and Mitophagy.
Study of an FBXO7 patient mutation reveals Fbxo7 and PI31 co-regulate proteasomes and mitochondria.
Metabolic priming by multiple enzyme systems supports glycolysis, HIF1α stabilisation, and human cancer cell survival in early hypoxia.
DHODH inhibition represents a therapeutic strategy and improves abiraterone treatment in castration-resistant prostate cancer.
MFN2 suppresses the accumulation of lipid droplets and the progression of clear cell renal cell carcinoma.
OGDH and Bcl-xL loss causes synthetic lethality in glioblastoma.
Mitochondria act as a key regulatory factor in cancer progression: Current concepts on mutations, mitochondrial dynamics, and therapeutic approach.
Forchlorfenuron-Induced Mitochondrial Respiration Inhibition and Metabolic Shifts in Endometrial Cancer.
Identification of fatty acid oxidation-related subtypes by integrated analysis of bulk- and single-cell transcriptome profiling in colorectal cancer.
Genetic ablation of Immt induces a lethal disruption of the MICOS complex.
Proguanil Suppresses Breast Tumor Growth In Vitro and In Vivo by Inducing Apoptosis via Mitochondrial Dysfunction.
FASN Inhibition Decreases MHC-I Degradation and Synergizes with PD-L1 Checkpoint Blockade in Hepatocellular Carcinoma.
m6A RNA methylation regulates mitochondrial function.

Cancers (Basel). 2024 Feb 29. pii: 1014. [Epub ahead of print]16(5):

The ATPase Inhibitory Factor 1 (IF1) Contributes to the Warburg Effect and Is Regulated by Its Phosphorylation in S39 by a Protein Kinase A-like Activity.

José M Cuezva, Sonia Domínguez-Zorita.

  The relevant role played by the ATPase Inhibitory Factor 1 (IF1) as a physiological in vivo inhibitor of mitochondrial ATP synthase in cancer and non-cancer cells, and in the mitochondria of different mouse tissues, as assessed in different genetic loss- and gain-of-function models of IF1 has been extensively documented. In this review we summarize our findings and those of others that favor the implication of IF1 in metabolic reprogramming to an enhanced glycolytic phenotype, which is mediated by its binding and inhibition of the ATP synthase. Moreover, we emphasize that IF1 is phosphorylated in vivo in its S39 by the c-AMP-dependent PKA activity of mitochondria to render an inactive inhibitor that is unable to interact with the enzyme, thus triggering the activation of ATP synthase. Overall, we discuss and challenge the results that argue against the role of IF1 as in vivo inhibitor of mitochondrial ATP synthase and stress that IF1 cannot be regarded solely as a pro-oncogenic protein because in some prevalent carcinomas, it prevents metastatic disease.

Keywords:  ATP synthase; ATPase Inhibitory Factor 1; cancer; metabolic reprogramming; mitochondria; oxidative phosphorylation

DOI:  https://doi.org/10.3390/cancers16051014
J Biol Chem. 2024 Mar 11. pii: S0021-9258(24)01654-5. [Epub ahead of print] 107159

Fatty acid oxidation drives mitochondrial hydrogen peroxide production by α-ketoglutarate dehydrogenase.

Cathryn Grayson, Ben Faerman, Olivia Koufos, Ryan J Mailloux.

In the present study, we examined the mitochondrial hydrogen peroxide (mH2O2) generating capacity of α-ketoglutarate dehydrogenase (KGDH) and compared it to components of the electron transport chain (ETC) using liver mitochondria isolated from male and female C57BL6N mice. We show for the first time there are some sex dimorphisms in the production of mH2O2 by ETC complexes I and III when mitochondria are fueled with different substrates. However, in our investigations into these sex effects, we made the unexpected discovery that: 1. KGDH serves as a major mH2O2 supplier in male and female liver mitochondria and 2. KGDH can form mH2O2 when mitochondria are energized with fatty acids, but only when malate is used to prime the Krebs cycle. Surprisingly, 2-keto-3-methylvaleric acid (KMV), a site-specific inhibitor for KGDH, nearly abolished mH2O2 generation in both male and female liver mitochondria oxidizing palmitoyl-carnitine. KMV inhibited mH2O2 production in liver mitochondria from male and female mice oxidizing myristoyl-, octanoyl-, or butyryl-carnitine. S1QEL 1.1 (S1) and S3QEL 2 (S3), compounds that inhibit reactive oxygen species (ROS) generation by complexes I and III, respectively, without interfering with OxPhos, had a negligible effect on the rate of mH2O2 production when pyruvate or acyl-carnitines were used as fuels. However, inclusion of KMV in reaction mixtures containing S1 and/or S3 almost abolished mH2O2 generation. Together, our findings suggest KGDH is the main mH2O2 generator in liver mitochondria, even when fatty acids are used as fuel.

DOI: https://doi.org/10.1016/j.jbc.2024.107159
Nat Commun. 2024 Mar 11. 15(1): 2203

Mitochondrial metabolism sustains CD8+ T cell migration for an efficient infiltration into solid tumors.

Luca Simula, Mattia Fumagalli, Lene Vimeux, Irena Rajnpreht, Philippe Icard, Gary Birsen, Dongjie An, Frédéric Pendino, Adrien Rouault, Nadège Bercovici, Diane Damotte, Audrey Lupo-Mansuet, Marco Alifano, Marie-Clotilde Alves-Guerra, Emmanuel Donnadieu.

The ability of CD8+ T cells to infiltrate solid tumors and reach cancer cells is associated with improved patient survival and responses to immunotherapy. Thus, identifying the factors controlling T cell migration in tumors is critical, so that strategies to intervene on these targets can be developed. Although interstitial motility is a highly energy-demanding process, the metabolic requirements of CD8+ T cells migrating in a 3D environment remain unclear. Here, we demonstrate that the tricarboxylic acid (TCA) cycle is the main metabolic pathway sustaining human CD8+ T cell motility in 3D collagen gels and tumor slices while glycolysis plays a more minor role. Using pharmacological and genetic approaches, we report that CD8+ T cell migration depends on the mitochondrial oxidation of glucose and glutamine, but not fatty acids, and both ATP and ROS produced by mitochondria are required for T cells to migrate. Pharmacological interventions to increase mitochondrial activity improve CD8+ T cell intratumoral migration and CAR T cell recruitment into tumor islets leading to better control of tumor growth in human xenograft models. Our study highlights the rationale of targeting mitochondrial metabolism to enhance the migration and antitumor efficacy of CAR T cells in treating solid tumors.

DOI: https://doi.org/10.1038/s41467-024-46377-7
Cancers (Basel). 2024 Mar 05. pii: 1048. [Epub ahead of print]16(5):

Increased O-GlcNAcylation by Upregulation of Mitochondrial O-GlcNAc Transferase (mOGT) Inhibits the Activity of Respiratory Chain Complexes and Controls Cellular Bioenergetics.

Paweł Jóźwiak, Joanna Oracz, Angela Dziedzic, Rafał Szelenberger, Dorota Żyżelewicz, Michał Bijak, Anna Krześlak.

  O-linked β-N-acetylglucosamine (O-GlcNAc) is a reversible post-translational modification involved in the regulation of cytosolic, nuclear, and mitochondrial proteins. The interplay between O-GlcNAcylation and phosphorylation is critical to control signaling pathways and maintain cellular homeostasis. The addition of O-GlcNAc moieties to target proteins is catalyzed by O-linked N-acetylglucosamine transferase (OGT). Of the three splice variants of OGT described, one is destined for the mitochondria (mOGT). Although the effects of O-GlcNAcylation on the biology of normal and cancer cells are well documented, the role of mOGT remains poorly understood. In this manuscript, the effects of mOGT on mitochondrial protein phosphorylation, electron transport chain (ETC) complex activity, and the expression of VDAC porins were investigated. We performed studies using normal and breast cancer cells with upregulated mOGT or its catalytically inactive mutant. Proteomic approaches included the isolation of O-GlcNAc-modified proteins of the electron transport chain, followed by their analysis using mass spectrometry. We found that mitochondrial OGT regulates the activity of complexes I-V of the respiratory chain and identified a group of 19 ETC components as mOGT substrates in mammary cells. Furthermore, we observed that the upregulation of mOGT inhibited the interaction of VDAC1 with hexokinase II. Our results suggest that the deregulation of mOGT reprograms cellular energy metabolism via interaction with and O-GlcNAcylation of proteins involved in ATP production in mitochondria and its exchange between mitochondria and the cytosol.

Keywords:  O-GlcNAc; VDAC; breast cells; electron transport chain; mOGT; mitochondria

DOI:  https://doi.org/10.3390/cancers16051048
Apoptosis. 2024 Mar 13.

FAM83B regulates mitochondrial metabolism and anti-apoptotic activity in pulmonary adenocarcinoma.

Jiajia Wang, Panpan Li, Limin Sun, Jing Zhang, Ke Yue, Yan Wang, Xiaojuan Wu.

  Chemotherapy is an effective therapeutic modality; nevertheless, a significant proportion of patients diagnosed with lung adenocarcinoma (LUAD) demonstrate resistance to chemotherapy. Therefore, it is crucial to understand the potential regulatory mechanisms to develop novel treatment strategies. This study aims to understand how increased FAM83B expression impacts mitochondrial activity, cell apoptosis, and chemotherapy effectiveness in LUAD. Multiple assays, such as CCK8, wound healing, EdU, and transwell assays, were employed to confirm the augmented chemotherapy resistance, heightened cell proliferation, migration, and invasion caused by FAM83B overexpression in LUAD cells. Furthermore, MIMP, MTG, and ATP assays were utilized to quantify changes in mitochondrial metabolism. In vitro functional assays were performed to evaluate the influence of FAM83B overexpression on the malignant progression and resistance mechanisms to chemotherapy in LUAD. In the context of this study, it was determined that LUAD patients with increased FAM83B expression had shorter survival times, and tissue samples with FAM83B overexpression were more prone to metastasis compared to primary samples. As a result, FAM83B is identified as an adverse prognostic marker. The mechanistic analysis demonstrated that FAM83B impedes the translocation of calbindin 2 (CALB2) from the cytoplasm to the mitochondria, resulting in the inhibition of apoptosis and the promotion of mitochondrial activity. Consequently, this ultimately confers resistance to chemotherapy in LUAD. Furthermore, the administration of metformin, which blocks mitochondrial oxidative phosphorylation (OXPHOS), can restore sensitivity to drug resistance in LUAD. Taken together, these findings provide substantial evidence supporting the notion that FAM83B enhances chemotherapy resistance in LUAD through the upregulation of mitochondrial metabolism and the inhibition of apoptosis.

Keywords:  Apoptosis; CALB2; Chemotherapy resistance; FAM83B; Lung adenocarcinoma; Mitochondrial metabolism

DOI:  https://doi.org/10.1007/s10495-024-01944-7
EMBO Rep. 2024 Mar 13.

PRODH safeguards human naive pluripotency by limiting mitochondrial oxidative phosphorylation and reactive oxygen species production.

Cheng Chen, Qianyu Liu, Wenjie Chen, Zhiyuan Gong, Bo Kang, Meihua Sui, Liming Huang, Ying-Jie Wang.

  Naive human embryonic stem cells (hESCs) that resemble the pre-implantation epiblasts are fueled by a combination of aerobic glycolysis and oxidative phosphorylation, but their mitochondrial regulators are poorly understood. Here we report that, proline dehydrogenase (PRODH), a mitochondria-localized proline metabolism enzyme, is dramatically upregulated in naive hESCs compared to their primed counterparts. The upregulation of PRODH is induced by a reduction in c-Myc expression that is dependent on PD0325901, a MEK inhibitor routinely present in naive hESC culture media. PRODH knockdown in naive hESCs significantly promoted mitochondrial oxidative phosphorylation (mtOXPHOS) and reactive oxygen species (ROS) production that triggered autophagy, DNA damage, and apoptosis. Remarkably, MitoQ, a mitochondria-targeted antioxidant, effectively restored the pluripotency and proliferation of PRODH-knockdown naive hESCs, indicating that PRODH maintains naive pluripotency by preventing excessive ROS production. Concomitantly, PRODH knockdown significantly slowed down the proteolytic degradation of multiple key mitochondrial electron transport chain complex proteins. Thus, we revealed a crucial role of PRODH in limiting mtOXPHOS and ROS production, and thereby safeguarding naive pluripotency of hESCs.

Keywords:  Electron Transport Chain Complex; Human Naive Pluripotency; PRODH; Reactive Oxygen Species; mtOXPHOS

DOI:  https://doi.org/10.1038/s44319-024-00110-z
Biol Chem. 2024 Mar 12.

Yeast Bxi1/Ybh3 mediates conserved mitophagy and apoptosis in yeast and mammalian cells: convergence in Bcl-2 family.

Yuying Wang, Zhiyuan Hu, Maojun Jiang, Yanxin Zhang, Linjie Yuan, Ziqian Wang, Ting Song, Zhichao Zhang.

  The process of degrading unwanted or damaged mitochondria by autophagy, called mitophagy, is essential for mitochondrial quality control together with mitochondrial apoptosis. In mammalian cells, pan-Bcl-2 family members including conical Bcl-2 members and non-conical ones are involved in and govern the two processes. We have illustrated recently the BH3 receptor Hsp70 interacts with Bim to mediate both apoptosis and mitophagy. However, whether similar pathways exist in lower eukaryotes where conical Bcl-2 members are absent remained unclear. Here, a specific inhibitor of the Hsp70-Bim PPI, S1g-10 and its analogs were used as chemical tools to explore the role of yeast Bxi1/Ybh3 in regulating mitophagy and apoptosis. Using Om45-GFP processing assay, we illustrated that yeast Ybh3 mediates a ubiquitin-related mitophagy pathway in both yeast and mammalian cells through association with Hsp70, which is in the same manner with Bim. Moreover, by using Bax/Bak double knockout MEF cells, Ybh3 was identified to induce apoptosis through forming oligomerization to trigger mitochondrial outer membrane permeabilization (MOMP) like Bax. We not only illustrated a conserved ubiquitin-related mitophagy pathway in yeast but also revealed the multi-function of Ybh3 which combines the function of BH3-only protein and multi-domain Bax protein as one.

Keywords:  Bxi1/Ybh3; Hsp70; mitophagy; ubiquitin

DOI:  https://doi.org/10.1515/hsz-2023-0359
bioRxiv. 2024 Mar 01. pii: 2024.02.27.582353. [Epub ahead of print]

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 to reduce the viability of BCL-xL/2 co-dependent SCLC cell lines in cell culture. In vivo, 5 mg/kg weekly dosing of 753b leads 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. 753b at this dosage was well tolerated in mice without induction of severe thrombocytopenia as seen with navitoclax nor induced 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:  Apoptosis; BCL-2; BCL-XL; PROTAC; Small-cell lung cancer

DOI:  https://doi.org/10.1101/2024.02.27.582353
Cell Death Discov. 2024 Mar 09. 10(1): 125

Novel meriolin derivatives activate the mitochondrial apoptosis pathway in the presence of antiapoptotic Bcl-2.

Laura Schmitt, Ilka Lechtenberg, Daniel Drießen, Hector Flores-Romero, Margaretha A Skowron, Marlena Sekeres, Julia Hoppe, Karina S Krings, Tanya R Llewellyn, Christoph Peter, Björn Stork, Nan Qin, Sanil Bhatia, Daniel Nettersheim, Gerhard Fritz, Ana J García-Sáez, Thomas J J Müller, Sebastian Wesselborg.

Meriolin derivatives represent a new class of kinase inhibitors with a pronounced cytotoxic potential. Here, we investigated a newly synthesized meriolin derivative (termed meriolin 16) that displayed a strong apoptotic potential in Jurkat leukemia and Ramos lymphoma cells. Meriolin 16 induced apoptosis in rapid kinetics (within 2-3 h) and more potently (IC50: 50 nM) than the previously described derivatives meriolin 31 and 36 [1]. Exposure of Ramos cells to meriolin 16, 31, or 36 for 5 min was sufficient to trigger severe and irreversible cytotoxicity. Apoptosis induction by all three meriolin derivatives was independent of death receptor signaling but required caspase-9 and Apaf-1 as central mediators of the mitochondrial death pathway. Meriolin-induced mitochondrial toxicity was demonstrated by disruption of the mitochondrial membrane potential (ΔΨm), mitochondrial release of proapoptotic Smac, processing of the dynamin-like GTPase OPA1, and subsequent fragmentation of mitochondria. Remarkably, all meriolin derivatives were able to activate the mitochondrial death pathway in Jurkat cells, even in the presence of the antiapoptotic Bcl-2 protein. In addition, meriolins were capable of inducing cell death in imatinib-resistant K562 and KCL22 chronic myeloid leukemia cells as well as in cisplatin-resistant J82 urothelial carcinoma and 2102EP germ cell tumor cells. Given the frequent inactivation of the mitochondrial apoptosis pathway by tumor cells, such as through overexpression of antiapoptotic Bcl-2, meriolin derivatives emerge as promising therapeutic agents for overcoming treatment resistance.

DOI: https://doi.org/10.1038/s41420-024-01901-y
Nat Commun. 2024 Mar 13. 15(1): 2264

NME3 is a gatekeeper for DRP1-dependent mitophagy in hypoxia.

Chih-Wei Chen, Chi Su, Chang-Yu Huang, Xuan-Rong Huang, Xiaojing Cuili, Tung Chao, Chun-Hsiang Fan, Cheng-Wei Ting, Yi-Wei Tsai, Kai-Chien Yang, Ti-Yen Yeh, Sung-Tsang Hsieh, Yi-Ju Chen, Yuxi Feng, Tony Hunter, Zee-Fen Chang.

NME3 is a member of the nucleoside diphosphate kinase (NDPK) family localized on the mitochondrial outer membrane (MOM). Here, we report a role of NME3 in hypoxia-induced mitophagy dependent on its active site phosphohistidine but not the NDPK function. Mice carrying a knock-in mutation in the Nme3 gene disrupting NME3 active site histidine phosphorylation are vulnerable to ischemia/reperfusion-induced infarction and develop abnormalities in cerebellar function. Our mechanistic analysis reveals that hypoxia-induced phosphatidic acid (PA) on mitochondria is essential for mitophagy and the interaction of DRP1 with NME3. The PA binding function of MOM-localized NME3 is required for hypoxia-induced mitophagy. Further investigation demonstrates that the interaction with active NME3 prevents DRP1 susceptibility to MUL1-mediated ubiquitination, thereby allowing a sufficient amount of active DRP1 to mediate mitophagy. Furthermore, MUL1 overexpression suppresses hypoxia-induced mitophagy, which is reversed by co-expression of ubiquitin-resistant DRP1 mutant or histidine phosphorylatable NME3. Thus, the site-specific interaction with active NME3 provides DRP1 a microenvironment for stabilization to proceed the segregation process in mitophagy.

DOI: https://doi.org/10.1038/s41467-024-46385-7
Cancers (Basel). 2024 Feb 27. pii: 960. [Epub ahead of print]16(5):

Expression of Mitochondrial Long Non-Coding RNAs, MDL1 and MDL1AS, Are Good Prognostic and/or Diagnostic Biomarkers for Several Cancers, Including Colorectal Cancer.

Pablo Garrido, Adrián Casas-Benito, Ignacio M Larrayoz, Judit Narro-Íñiguez, Susana Rubio-Mediavilla, Enrique Zozaya, Alfonso Martín-Carnicero, Alfredo Martínez.

  Non-coding RNAs provide new opportunities to identify biomarkers that properly classify cancer patients. Here, we study the biomarker status of the mitochondrial long non-coding RNAs, MDL1 and MDL1AS. Expression of these genes was studied in public transcriptomic databases. In addition, a cohort of 69 locally advanced rectal cancer (LARC) patients with a follow-up of more than 5 years was used to determine the prognostic value of these markers. Furthermore, cell lines of colorectal (HCT116) and breast (MDA-MB-231) carcinoma were employed to study the effects of downregulating MDL1AS in vitro. Expression of MDL1AS (but not MDL1) was significantly different in tumor cells than in the surrounding tissue in a tumor-type-specific context. Both MDL1 and MDL1AS were accurate biomarkers for the 5-year survival of LARC patients (p = 0.040 and p = 0.007, respectively) with promising areas under the curve in the ROC analyses (0.820 and 0.930, respectively). MDL1AS downregulation reduced mitochondrial respiration in both cell lines. Furthermore, this downregulation produced a decrease in growth and migration on colorectal cells, but the reverse effects on breast cancer cells. In summary, MDL1 and MDL1AS can be used as reliable prognostic biomarkers of LARC, and MDL1AS expression provides relevant information on the diagnosis of different cancers.

Keywords:  breast cancer; growth; long non-coding RNAs; migration; mitochondria; oxidative phosphorylation; rectal cancer

DOI:  https://doi.org/10.3390/cancers16050960
bioRxiv. 2024 Feb 28. pii: 2023.08.18.553810. [Epub ahead of print]

13 C-SpaceM: Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer.

Elena Buglakova, Måns Ekelöf, Michaela Schwaiger-Haber, Lisa Schlicker, Martijn R Molenaar, Shahraz Mohammed, Lachlan Stuart, Andreas Eisenbarth, Volker Hilsenstein, Gary J Patti, Almut Schulze, Marteinn T Snaebjornsson, Theodore Alexandrov.

Metabolism has emerged as a key factor in homeostasis and disease including cancer. Yet, little is known about the heterogeneity of metabolic activity of cancer cells due to the lack of tools to directly probe it. Here, we present a novel method, 13 C-SpaceM for spatial single-cell isotope tracing of glucose-dependent de novo lipogenesis. The method combines imaging mass spectrometry for spatially-resolved detection of 13 C 6 -glucose-derived 13 C label incorporated into esterified fatty acids with microscopy and computational methods for data integration and analysis. We validated 13 C-SpaceM on a spatially-heterogeneous normoxia-hypoxia model of liver cancer cells. Investigating cultured cells, we revealed single-cell heterogeneity of lipogenic acetyl-CoA pool labelling degree upon ACLY knockdown that is hidden in the bulk analysis and its effect on synthesis of individual fatty acids. Next, we adapted 13 C-SpaceM to analyze tissue sections of mice harboring isocitrate dehydrogenase (IDH)-mutant gliomas. We found a strong induction of de novo fatty acid synthesis in the tumor tissue compared to the surrounding brain. Comparison of fatty acid isotopologue patterns revealed elevated uptake of mono-unsaturated and essential fatty acids in the tumor. Furthermore, our analysis uncovered substantial spatial heterogeneity in the labelling of the lipogenic acetyl-CoA pool indicative of metabolic reprogramming during microenvironmental adaptation. Overall, 13 C-SpaceM enables novel ways for spatial probing of metabolic activity at the single cell level. Additionally, this methodology provides unprecedented insight into fatty acid uptake, synthesis and modification in normal and cancerous tissues.

DOI: https://doi.org/10.1101/2023.08.18.553810
Cancer Lett. 2024 Mar 09. pii: S0304-3835(24)00195-2. [Epub ahead of print] 216802

Targeting PARP14 with lomitapide suppresses drug resistance through the activation of DRP1-induced mitophagy in multiple myeloma.

Honghao Zhang, Hao Wang, Yuxing Hu, Yang Gao, Jianyu Chen, Yabo Meng, Yingqi Qiu, Rong Hu, Peiyun Liao, Meifang Li, Yanjie He, Zhao Liang, Xiaoling Xie, Yuhua Li.

  Multiple myeloma (MM) is a hematological malignancy that remains incurable, primarily due to the high likelihood of relapse or development of resistance to current treatments. To explore and discover new medications capable of overcoming drug resistance in MM, we conducted cell viability inhibition screens of 1504 FDA-approved drugs. Lomitapide, a cholesterol-lowering agent, was found to exhibit effective inhibition on bortezomib-resistant MM cells in vitro and in vivo. Our data also indicated that lomitapide decreases the permeability of the mitochondrial outer membrane and induces mitochondrial dysfunction in MM cells. Next, lomitapide treatment upregulated DRP1 and PINK1 expression levels, coupled with the mitochondrial translocation of Parkin, leading to MM cell mitophagy. Excessive mitophagy caused mitochondrial damage and dysfunction induced by lomitapide. Meanwhile, PARP14 was identified as a direct target of lomitapide by SPR-HPLC-MS, and we showed that DRP1-induced mitophagy was crucial in the anti-MM activity mediated by PARP14. Furthermore, PARP14 is overexpressed in MM patients, implying that it is a novel therapeutic target in MM. Collectively, our results demonstrate that DRP1-mediated mitophagy induced by PARP14 may be the cause for mitochondrial dysfunction and damage in response to lomitapide treatment.

Keywords:  Drug resistance; Lomitapide; Mitophagy; Multiple myeloma; PARP14

DOI:  https://doi.org/10.1016/j.canlet.2024.216802
Cell Death Dis. 2024 Mar 11. 15(3): 204

A first-in-class TIMM44 blocker inhibits bladder cancer cell growth.

Lifeng Zhang, Xiaokai Shi, Lei Zhang, Yuanyuan Mi, Li Zuo, Shenglin Gao.

Mitochondria play a multifaceted role in supporting bladder cancer progression. Translocase of inner mitochondrial membrane 44 (TIMM44) is essential for maintaining function and integrity of mitochondria. We here tested the potential effect of MB-10 (MitoBloCK-10), a first-in-class TIMM44 blocker, against bladder cancer cells. TIMM44 mRNA and protein expression is significantly elevated in both human bladder cancer tissues and cells. In both patient-derived primary bladder cancer cells and immortalized (T24) cell line, MB-10 exerted potent anti-cancer activity and inhibited cell viability, proliferation and motility. The TIMM44 blocker induced apoptosis and cell cycle arrest in bladder cancer cells, but failed to provoke cytotoxicity in primary bladder epithelial cells. MB-10 disrupted mitochondrial functions in bladder cancer cells, causing mitochondrial depolarization, oxidative stress and ATP reduction. Whereas exogenously-added ATP and the antioxidant N-Acetyl Cysteine mitigated MB-10-induced cytotoxicity of bladder cancer cells. Genetic depletion of TIMM44 through CRISPR-Cas9 method also induced robust anti-bladder cancer cell activity and MB-10 had no effect in TIMM44-depleted cancer cells. Contrarily, ectopic overexpression of TIMM44 using a lentiviral construct augmented proliferation and motility of primary bladder cancer cells. TIMM44 is important for Akt-mammalian target of rapamycin (mTOR) activation. In primary bladder cancer cells, Akt-S6K1 phosphorylation was decreased by MB-10 treatment or TIMM44 depletion, but enhanced after ectopic TIMM44 overexpression. In vivo, intraperitoneal injection of MB-10 impeded bladder cancer xenograft growth in nude mice. Oxidative stress, ATP reduction, Akt-S6K1 inhibition and apoptosis were detected in MB-10-treated xenograft tissues. Moreover, genetic depletion of TIMM44 also arrested bladder cancer xenograft growth in nude mice, leading to oxidative stress, ATP reduction and Akt-S6K1 inhibition in xenograft tissues. Together, targeting overexpressed TIMM44 by MB-10 significantly inhibits bladder cancer cell growth in vitro and in vivo.

DOI: https://doi.org/10.1038/s41419-024-06585-x
Nat Rev Clin Oncol. 2024 Mar 14.

Targeting cuproplasia and cuproptosis in cancer.

Daolin Tang, Guido Kroemer, Rui Kang.

Copper, an essential trace element that exists in oxidized and reduced forms, has pivotal roles in a variety of biological processes, including redox chemistry, enzymatic reactions, mitochondrial respiration, iron metabolism, autophagy and immune modulation; maintaining copper homeostasis is crucial as both its deficiency and its excess are deleterious. Dysregulated copper metabolism has a dual role in tumorigenesis and cancer therapy. Specifically, cuproplasia describes copper-dependent cell growth and proliferation, including hyperplasia, metaplasia and neoplasia, whereas cuproptosis refers to a mitochondrial pathway of cell death triggered by excessive copper exposure and subsequent proteotoxic stress (although complex interactions between cuproptosis and other cell death mechanisms, such as ferroptosis, are likely and remain enigmatic). In this Review, we summarize advances in our understanding of copper metabolism, the molecular machineries underlying cuproplasia and cuproptosis, and their potential targeting for cancer therapy. These new findings advance the rapidly expanding field of translational cancer research focused on metal compounds.

DOI: https://doi.org/10.1038/s41571-024-00876-0
bioRxiv. 2024 Feb 28. pii: 2024.02.24.581168. [Epub ahead of print]

The Ubiquitin Ligase RBX2/SAG Regulates Mitochondrial Ubiquitination and Mitophagy.

Wenjuan Wang, Ermin Li, Jianqiu Zou, Qu Chen, Juan Ayala, Yuan Wen, Md Sadikul Islam, Neal L Weintraub, David J Fulton, Qiangrong Liang, Jiliang Zhou, Jinbao Liu, Jie Li, Yi Sun, Huabo Su.

Clearance of damaged mitochondria via mitophagy is crucial for cellular homeostasis. While the role of ubiquitin (Ub) ligase PARKIN in mitophagy has been extensively studied, increasing evidence suggests the existence of PARKIN-independent mitophagy in highly metabolically active organs such as the heart. Here, we identify a crucial role for Cullin-RING Ub ligase 5 (CRL5) in basal mitochondrial turnover in cardiomyocytes. CRL5 is a multi-subunit Ub ligase comprised by the catalytic RING box protein RBX2 (also known as SAG), scaffold protein Cullin 5 (CUL5), and a substrate-recognizing receptor. Analysis of the mitochondrial outer membrane-interacting proteome uncovered a robust association of CRLs with mitochondria. Subcellular fractionation, immunostaining, and immunogold electron microscopy established that RBX2 and Cul5, two core components of CRL5, localizes to mitochondria. Depletion of RBX2 inhibited mitochondrial ubiquitination and turnover, impaired mitochondrial membrane potential and respiration, and increased cell death in cardiomyocytes. In vivo , deletion of the Rbx2 gene in adult mouse hearts suppressed mitophagic activity, provoked accumulation of damaged mitochondria in the myocardium, and disrupted myocardial metabolism, leading to rapid development of dilated cardiomyopathy and heart failure. Similarly, ablation of RBX2 in the developing heart resulted in dilated cardiomyopathy and heart failure. Notably, the action of RBX2 in mitochondria is not dependent on PARKIN, and PARKIN gene deletion had no impact on the onset and progression of cardiomyopathy in RBX2-deficient hearts. Furthermore, RBX2 controls the stability of PINK1 in mitochondria. Proteomics and biochemical analyses further revealed a global impact of RBX2 deficiency on the mitochondrial proteome and identified several mitochondrial proteins as its putative substrates. These findings identify RBX2-CRL5 as a mitochondrial Ub ligase that controls mitophagy under physiological conditions in a PARKIN-independent, PINK1-dependent manner, thereby regulating cardiac homeostasis.
Non-standard abbreviations and acronyms: RBX2, RING-Box Protein 2; SAG, Sensitive to Apoptosis Gene; Ub, Ubiquitin; pS65-Ub, phosphorylated Ub at serine 65; MAVS, mitochondrial antiviral-signaling protein; AAV, adeno-associated virus; AV, adenovirus; siRNA, Small interfering RNA; GFP, green fluorescent protein; CUL, cullin; RING, Really Interesting New Gene; CRLs, cullin-RING ligases; CSN, COP9 signalosome; APEX2, ascorbate peroxidase 2; mito, mitochondrial; cyto, cytosolic; MOM, mitochondrial outer membrane; CCCP, Carbonyl Cyanide Chlorophenylhydrazone; OMP25, Outer membrane protein 25; PK, proteinase K; HA, hemagglutinin; TMRM, Tetramethylrhodamine methyl ester perchlorate; αMHC,α-myosin heavy chain; CKO, cardiomyocyte-specific knockout; TAM, tamoxifen; TMT, tandem mass tag; KD, knockdown; CTL, control; MCM, MerCreMer; iCKO, inducible cardiomyocyte-specific knockout; BFA, bafilomycin A1; PCA, principle component analysis; MS, Mass spectrometry; DEPs, differentially expressed proteins; FC, fold change; FDR, False Discovery Rate; KEGG, Kyoto encyclopedia of genes and genomes; ER, endoplasmic reticulum; DKO, double knockout; CM, cardiomyocyte; cTnT, cardiac troponin T; NRVCs, neonatal rat ventricular cardiomyocytes; NRVMs, neonatal mouse ventricular cardiomyocytes; NMVFs, neonatal mouse ventricular fibroblasts; HF, heart failure; KO, knockout; MF, Molecular Functions; CC, Cellular Components; BP, Biological Process; TUNEL, Terminal deoxynucleotidyl transferase dUTP nick end labeling; SCF, Skp1-Cullin 1-F-box.

DOI: https://doi.org/10.1101/2024.02.24.581168
FEBS J. 2024 Mar 11.

Study of an FBXO7 patient mutation reveals Fbxo7 and PI31 co-regulate proteasomes and mitochondria.

Sara Al Rawi, Lorna Simpson, Guðrún Agnarsdóttir, Neil Q McDonald, Veronika Chernuha, Orly Elpeleg, Massimo Zeviani, Roger A Barker, Ronen Spiegel, Heike Laman.

  Mutations in FBXO7 have been discovered to be associated with an atypical parkinsonism. We report here a new homozygous missense mutation in a paediatric patient that causes an L250P substitution in the dimerisation domain of Fbxo7. This alteration selectively ablates the Fbxo7-PI31 interaction and causes a significant reduction in Fbxo7 and PI31 levels in patient cells. Consistent with their association with proteasomes, patient fibroblasts have reduced proteasome activity and proteasome subunits. We also show PI31 interacts with the MiD49/51 fission adaptor proteins, and unexpectedly, PI31 acts to facilitate SCFFbxo7 -mediated ubiquitination of MiD49. The L250P mutation reduces the SCFFbxo7 ligase-mediated ubiquitination of a subset of its known substrates. Although MiD49/51 expression was reduced in patient cells, there was no effect on the mitochondrial network. However, patient cells show reduced levels of mitochondrial function and mitophagy, higher levels of ROS and are less viable under stress. Our study demonstrates that Fbxo7 and PI31 regulate proteasomes and mitochondria and reveals a new function for PI31 in enhancing the SCFFbxo7 E3 ubiquitin ligase activity.

Keywords:  E3 ubiquitin ligase; Fbxo7/PARK15; Parkinson's disease; mitochondria; proteasome

DOI:  https://doi.org/10.1111/febs.17114
EMBO J. 2024 Mar 14.

Metabolic priming by multiple enzyme systems supports glycolysis, HIF1α stabilisation, and human cancer cell survival in early hypoxia.

Fiona Grimm, Agustín Asuaje, Aakriti Jain, Mariana Silva Dos Santos, Jens Kleinjung, Patrícia M Nunes, Stefanie Gehrig, Louise Fets, Salihanur Darici, James I MacRae, Dimitrios Anastasiou.

  Adaptation to chronic hypoxia occurs through changes in protein expression, which are controlled by hypoxia-inducible factor 1α (HIF1α) and are necessary for cancer cell survival. However, the mechanisms that enable cancer cells to adapt in early hypoxia, before the HIF1α-mediated transcription programme is fully established, remain poorly understood. Here we show in human breast cancer cells, that within 3 h of hypoxia exposure, glycolytic flux increases in a HIF1α-independent manner but is limited by NAD+ availability. Glycolytic ATP maintenance and cell survival in early hypoxia rely on reserve lactate dehydrogenase A capacity as well as the activity of glutamate-oxoglutarate transaminase 1 (GOT1), an enzyme that fuels malate dehydrogenase 1 (MDH1)-derived NAD+. In addition, GOT1 maintains low α-ketoglutarate levels, thereby limiting prolyl hydroxylase activity to promote HIF1α stabilisation in early hypoxia and enable robust HIF1α target gene expression in later hypoxia. Our findings reveal that, in normoxia, multiple enzyme systems maintain cells in a primed state ready to support increased glycolysis and HIF1α stabilisation upon oxygen limitation, until other adaptive processes that require more time are fully established.

Keywords:  Glycolysis; HIF1α; Hypoxia; Metabolism; α-Ketoglutarate

DOI:  https://doi.org/10.1038/s44318-024-00065-w
Oncogene. 2024 Mar 13.

DHODH inhibition represents a therapeutic strategy and improves abiraterone treatment in castration-resistant prostate cancer.

Shaoqiang Guo, Miaomiao Miao, Yufeng Wu, Dongyue Pan, Qinyan Wu, Zhanfang Kang, Jianwen Zeng, Guoping Zhong, Chengfei Liu, Junjian Wang.

Castration-resistant prostate cancer (CRPC) is an aggressive disease with poor prognosis, and there is an urgent need for more effective therapeutic targets to address this challenge. Here, we showed that dihydroorotate dehydrogenase (DHODH), an enzyme crucial in the pyrimidine biosynthesis pathway, is a promising therapeutic target for CRPC. The transcript levels of DHODH were significantly elevated in prostate tumors and were negatively correlated with the prognosis of patients with prostate cancer. DHODH inhibition effectively suppressed CRPC progression by blocking cell cycle progression and inducing apoptosis. Notably, treatment with DHODH inhibitor BAY2402234 activated androgen biosynthesis signaling in CRPC cells. However, the combination treatment with BAY2402234 and abiraterone decreased intratumoral testosterone levels and induced apoptosis, which inhibited the growth of CWR22Rv1 xenograft tumors and patient-derived xenograft organoids. Taken together, these results establish DHODH as a key player in CRPC and as a potential therapeutic target for advanced prostate cancer.

DOI: https://doi.org/10.1038/s41388-024-03005-4
Cancer Sci. 2024 Mar 13.

MFN2 suppresses the accumulation of lipid droplets and the progression of clear cell renal cell carcinoma.

Zhiduan Cai, Wenjun Luo, Haoran Wang, Rui Zhu, Yaoji Yuan, Xiangyu Zhan, Mengyuan Xie, Haoquan Zhuang, Haoyu Chen, Yuyu Xu, Xiezhao Li, Leyuan Liu, Guibin Xu.

  Dissolving the lipid droplets in tissue section with alcohol during a hematoxylin and eosin (H&E) stain causes the tumor cells to appear like clear soap bubbles under a microscope, which is a key pathological feature of clear cell renal cell carcinoma (ccRCC). Mitochondrial dynamics have been reported to be closely associated with lipid metabolism and tumor development. However, the relationship between mitochondrial dynamics and lipid metabolism reprogramming in ccRCC remains to be further explored. We conducted bioinformatics analysis to identify key genes regulating mitochondrial dynamics differentially expressed between tumor and normal tissues and immunohistochemistry and Western blot to confirm. After the target was identified, we created stable ccRCC cell lines to test the impact of the target gene on mitochondrial morphology, tumorigenesis in culture cells and xenograft models, and profiles of lipid metabolism. It was found that mitofusin 2 (MFN2) was downregulated in ccRCC tissues and associated with poor prognosis in patients with ccRCC. MFN2 suppressed mitochondrial fragmentation, proliferation, migration, and invasion of ccRCC cells and growth of xenograft tumors. Furthermore, MFN2 impacted lipid metabolism and reduced the accumulation of lipid droplets in ccRCC cells. MFN2 suppressed disease progression and improved prognosis for patients with ccRCC possibly by interrupting cellular lipid metabolism and reducing accumulation of lipid droplets.

Keywords:  Hif2α; MFN2; clear cell renal cell carcinoma; lipid droplets; mitochondrial fusion

DOI:  https://doi.org/10.1111/cas.16151
JCI Insight. 2024 Mar 14. pii: e172565. [Epub ahead of print]

OGDH and Bcl-xL loss causes synthetic lethality in glioblastoma.

Trang Tt Nguyen, Consuelo Torrini, Enyuan Shang, Chang Shu, Jeong-Yeon Mun, Qiuqiang Gao, Nelson Humala, Hasan O Akman, Guoan Zhang, Mike-Andrew Westhoff, Georg Karpel-Massler, Jeffrey N Bruce, Peter Canoll, Markus D Siegelin.

  Glioblastoma (GBM) remains an incurable disease, requiring more effective therapies. Through interrogation of publicly available CRISPR and RNAi library screens, we identified the alpha-ketoglutarate dehydrogenase (OGDH) gene, which encodes for an enzyme that is part of the tricarboxylic acid cycle (TCA cycle) as essential for GBM growth. Moreover, by combining a transcriptome and metabolite screening analyses we discovered that loss of function of OGDH by the clinically validated drug compound, CPI-613, was synthetically lethal with Bcl-xL inhibition (genetically and through the clinically validated BH3-mimetic, ABT263) in patient-derived xenograft as well neurosphere GBM cultures. CPI-613 mediated energy deprivation drove an integrated stress response with an up-regulation of the BH3-only domain protein, Noxa in an ATF4 dependent manner as demonstrated by genetic loss of function experiments. Consistently, silencing of Noxa attenuated cell death induced by CPI-613 in model systems of GBM. In patient-derived xenograft models of GBM in mice, the combination treatment of ABT263 and CPI-613 suppressed tumor growth and extended animal survival more potently than each compound on its own. Therefore, combined inhibition of Bcl-xL along with interference of the TCA-cycle might be a treatment strategy for GBM.

Keywords:  Apoptosis pathways; Oncology

DOI:  https://doi.org/10.1172/jci.insight.172565
Mutat Res Rev Mutat Res. 2024 Mar 08. pii: S1383-5742(24)00003-6. [Epub ahead of print]793 108490

Mitochondria act as a key regulatory factor in cancer progression: Current concepts on mutations, mitochondrial dynamics, and therapeutic approach.

Sraddhya Roy, Ananya Das, Aparajita Bairagi, Debangshi Das, Ashna Jha, Amit Kumar Srivastava, Nabanita Chatterjee.

  The diversified impacts of mitochondrial function vs. dysfunction have been observed in almost all disease conditions including cancers. Mitochondria play crucial roles in cellular homeostasis and integrity, however, mitochondrial dysfunctions influenced by alterations in the mtDNA can disrupt cellular balance. Many external stimuli or cellular defects that cause cellular integrity abnormalities, also impact mitochondrial functions. Imbalances in mitochondrial activity can initiate and lead to accumulations of genetic mutations and can promote the processes of tumorigenesis, progression, and survival. This comprehensive review summarizes epigenetic and genetic alterations that affect the functionality of the mitochondria, with considerations of cellular metabolism, and as influenced by ethnicity. We have also reviewed recent insights regarding mitochondrial dynamics, miRNAs, exosomes that play pivotal roles in cancer promotion, and the impact of mitochondrial dynamics on immune cell mechanisms. The review also summarizes recent therapeutic approaches targeting mitochondria in anti-cancer treatment strategies.

Keywords:  Mitochondria; Mitochondrial alterations; cancer progression, immune cells; mitochondrial dynamics

DOI:  https://doi.org/10.1016/j.mrrev.2024.108490
Cancers (Basel). 2024 Feb 28. pii: 976. [Epub ahead of print]16(5):

Forchlorfenuron-Induced Mitochondrial Respiration Inhibition and Metabolic Shifts in Endometrial Cancer.

Kyukwang Kim, Negar Khazan, Rachael B Rowswell-Turner, Rakesh K Singh, Taylor Moore, Myla S Strawderman, John P Miller, Cameron W A Snyder, Ahmad Awada, Richard G Moore.

  Forchlorfenuron (FCF) is a widely used plant cytokinin that enhances fruit quality and size in agriculture. It also serves as a crucial pharmacological tool for the inhibition of septins. However, the precise target of FCF has not yet been fully determined. This study reveals a novel target of FCF and elucidates its downstream signaling events. FCF significantly impairs mitochondrial respiration and mediates metabolic shift toward glycolysis, thus making cells more vulnerable to glycolysis inhibition. Interestingly, FCF's impact on mitochondrial function persists, even in cells lacking septins. Furthermore, the impaired mitochondrial function leads to the degradation of HIF-1α, facilitated by increased cellular oxygen. FCF also induces AMPK activation, suppresses Erk1/2 phosphorylation, and reduces the expression of HER2, β-catenin, and PD-L1. Endometrial cancer is characterized by metabolic disorders such as diabetes and aberrant HER2/Ras-Erk1/2/β-catenin signaling. Thus, FCF may hold promise as a potential therapeutic in endometrial cancer.

Keywords:  AMPK; endometrial cancer; forchlorfenuron; mitochondrial respiration; septins

DOI:  https://doi.org/10.3390/cancers16050976
J Gastrointest Oncol. 2024 Feb 29. 15(1): 147-163

Identification of fatty acid oxidation-related subtypes by integrated analysis of bulk- and single-cell transcriptome profiling in colorectal cancer.

Peng Zou, Chengru Chen, Xiaobin Wu.

   Background: As one of the major metabolic reprogramming pathways, fatty acid oxidation (FAO) contributes to rapid progression in tumor cells. Nevertheless, the genomic patterns of patients' FAO levels in colorectal cancer (CRC) remain unknown. Hence, it is crucial to identify the interplay mechanisms of molecular biochemical features of FAO in CRC.
Methods: Data of patients with CRC were accessed from The Cancer Genome Atlas (TCGA). Unsupervised consensus clustering related to FAO sores was conducted. The differentially expressed genes (DEGs) were screened by clustering according to FAO status polarized in TCGA, followed by the construction of the scores of genes related to FAO (GFAO_Score). Enrichment of FAO and carcinogenesis at the cell level were calculated based on the single-cell RNA (scRNA) sequencing analysis. The clinical values and drug analysis of GFAO_Score were evaluated by external validation cohorts from Gene Expression Omnibus (GEO) datasets.
Results: We classified patients into two distinct FAO clusters which indicated those with lower FAO levels had poor prognosis and high enrichment of carcinogenic-gene pathways. Further, the high FAO-enriched subtypes in epithelial cells revealed carcinogenesis. Three FAO-related genes (ZFHX4, AQP8, and AKR1B10) were screened to construct the GFAO_Score. The high GFAO_Score group leaned toward advanced CRC and unfavorable survival outcomes in the validation cohort. The low GFAO_Score group possessed a better response to immunotherapy and exhibited lower IC50 (50% inhibition concentration) values for certain chemotherapy drugs, such as 5-fluorouracil, irinotecan, oxaliplatin, paclitaxel, and camptothecin.
Conclusions: FAO patterns vary in patients with CRC. The GFAO_Score might contribute to the precise screening of patients according to metabolism reprogramming and optimization of strategies in clinical practice.

Keywords:  Fatty acid oxidation (FAO); colorectal cancer (CRC); metabolic reprogramming; prediction; prognosis

DOI:  https://doi.org/10.21037/jgo-23-833
Life Sci Alliance. 2024 Jun;pii: e202302329. [Epub ahead of print]7(6):

Genetic ablation of Immt induces a lethal disruption of the MICOS complex.

Stephanie M Rockfield, Meghan E Turnis, Ricardo Rodriguez-Enriquez, Madhavi Bathina, Seng Kah Ng, Nathan Kurtz, Nathalie Becerra Mora, Stephane Pelletier, Camenzind G Robinson, Peter Vogel, Joseph T Opferman.

The mitochondrial contact site and cristae organizing system (MICOS) is important for crista junction formation and for maintaining inner mitochondrial membrane architecture. A key component of the MICOS complex is MIC60, which has been well studied in yeast and cell culture models. However, only one recent study has demonstrated the embryonic lethality of losing Immt (the gene encoding MIC60) expression. Tamoxifen-inducible ROSA-CreERT2-mediated deletion of Immt in adult mice disrupted the MICOS complex, increased mitochondria size, altered cristae morphology, and was lethal within 12 d. Pathologically, these mice displayed defective intestinal muscle function (paralytic ileus) culminating in dehydration. We also identified bone marrow (BM) hypocellularity in Immt-deleted mice, although BM transplants from wild-type mice did not improve survival. Altogether, this inducible mouse model demonstrates the importance of MIC60 in vivo, in both hematopoietic and non-hematopoietic tissues, and provides a valuable resource for future mechanistic investigations into the MICOS complex.

DOI: https://doi.org/10.26508/lsa.202302329
Cancers (Basel). 2024 Feb 22. pii: 872. [Epub ahead of print]16(5):

Proguanil Suppresses Breast Tumor Growth In Vitro and In Vivo by Inducing Apoptosis via Mitochondrial Dysfunction.

Nehal Gupta, Marina Curcic, Sanjay K Srivastava.

  Breast cancer, ranking as the second leading cause of female cancer-related deaths in the U.S., demands the exploration of innovative treatments. Repurposing FDA-approved drugs emerges as an expedited and cost-effective strategy. Our study centered on proguanil, an antimalarial drug, reveals notable anti-proliferative effects on diverse breast cancer cell lines, including those derived from patients. Proguanil-induced apoptosis was associated with a substantial increase in reactive oxygen species (ROS) production, leading to reduced mitochondrial membrane potential, respiration, and ATP production. Proguanil treatment upregulated apoptotic markers (Bax, p-H2AX, cleaved-caspase 3, 9, cleaved PARP) and downregulated anti-apoptotic proteins (bcl-2, survivin) in breast cancer cell lines. In female Balb/c mice implanted with 4T1 breast tumors, daily oral administration of 20 mg/kg proguanil suppressed tumor enlargement by 55%. Western blot analyses of proguanil-treated tumors supported the in vitro findings, demonstrating increased levels of p-H2AX, Bax, c-PARP, and c-caspase3 as compared to controls. Our results collectively highlight proguanil's anticancer efficacy in vitro and in vivo in breast cancer, prompting further consideration for clinical investigations.

Keywords:  DNA damage; ROS; antimalarial drug; apoptosis; breast cancer; drug repurposing; mitochondria; mitochondrial dysfunction; oxidative phosphorylation

DOI:  https://doi.org/10.3390/cancers16050872
Cancer Res. 2024 Mar 15. 84(6): 855-871

FASN Inhibition Decreases MHC-I Degradation and Synergizes with PD-L1 Checkpoint Blockade in Hepatocellular Carcinoma.

Jiao Huang, Wai Ying Tsang, Xiao-Na Fang, Yu Zhang, Jie Luo, Lan-Qi Gong, Bai-Feng Zhang, Ching Ngar Wong, Zhi-Hong Li, Bei-Lei Liu, Jin-Lin Huang, Yu-Ma Yang, Shan Liu, Liu-Xian Ban, Yiu Hong Chan, Xin-Yuan Guan.

Immune checkpoint inhibitors (ICI) transformed the treatment landscape of hepatocellular carcinoma (HCC). Unfortunately, patients with attenuated MHC-I expression remain refractory to ICIs, and druggable targets for upregulating MHC-I are limited. Here, we found that genetic or pharmacologic inhibition of fatty acid synthase (FASN) increased MHC-I levels in HCC cells, promoting antigen presentation and stimulating antigen-specific CD8+ T-cell cytotoxicity. Mechanistically, FASN inhibition reduced palmitoylation of MHC-I that led to its lysosomal degradation. The palmitoyltransferase DHHC3 directly bound MHC-I and negatively regulated MHC-I protein levels. In an orthotopic HCC mouse model, Fasn deficiency enhanced MHC-I levels and promoted cancer cell killing by tumor-infiltrating CD8+ T cells. Moreover, the combination of two different FASN inhibitors, orlistat and TVB-2640, with anti-PD-L1 antibody robustly suppressed tumor growth in vivo. Multiplex IHC of human HCC samples and bioinformatic analysis of The Cancer Genome Atlas data further illustrated that lower expression of FASN was correlated with a higher percentage of cytotoxic CD8+ T cells. The identification of FASN as a negative regulator of MHC-I provides the rationale for combining FASN inhibitors and immunotherapy for treating HCC.
SIGNIFICANCE: Inhibition of FASN increases MHC-I protein levels by suppressing its palmitoylation and lysosomal degradation, which stimulates immune activity against hepatocellular carcinoma and enhances the efficacy of immune checkpoint inhibition.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-0966
Hum Mol Genet. 2024 Mar 14. pii: ddae029. [Epub ahead of print]

m6A RNA methylation regulates mitochondrial function.

Michael Kahl, Zhaofa Xu, Saravanan Arumugam, Brittany Edens, Mariafausta Fischietti, Allen C Zhu, Leonidas C Platanias, Chuan He, Xiaoxi Zhuang, Yongchao C Ma.

  RNA methylation of N6-methyladenosine (m6A) is emerging as a fundamental regulator of every aspect of RNA biology. RNA methylation directly impacts protein production to achieve quick modulation of dynamic biological processes. However, whether RNA methylation regulates mitochondrial function is not known, especially in neuronal cells which require a high energy supply and quick reactive responses. Here we show that m6A RNA methylation regulates mitochondrial function through promoting nuclear-encoded mitochondrial complex subunit RNA translation. Conditional genetic knockout of m6A RNA methyltransferase Mettl14 (Methyltransferase like 14) by Nestin-Cre together with metabolomic analysis reveals that Mettl14 knockout-induced m6A depletion significantly downregulates metabolites related to energy metabolism. Furthermore, transcriptome-wide RNA methylation profiling of wild type and Mettl14 knockout mouse brains by m6A-Seq shows enrichment of methylation on mitochondria-related RNA. Importantly, loss of m6A leads to a significant reduction in mitochondrial respiratory capacity and membrane potential. These functional defects are paralleled by the reduced expression of mitochondrial electron transport chain complexes, as well as decreased mitochondrial super-complex assembly and activity. Mechanistically, m6A depletion decreases the translational efficiency of methylated RNA encoding mitochondrial complex subunits through reducing their association with polysomes, while not affecting RNA stability. Together, these findings reveal a novel role for RNA methylation in regulating mitochondrial function. Given that mitochondrial dysfunction and RNA methylation have been increasingly implicate in neurodegenerative disorders, our findings not only provide insights into fundamental mechanisms regulating mitochondrial function, but also open up new avenues for understanding the pathogenesis of neurological diseases.

Keywords:  m6A RNA methylation; metabolomics; mitochondria; neurological disease; transcriptomics

DOI:  https://doi.org/10.1093/hmg/ddae029