bims-mibica 2024-01-21 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2024–01–21
28 papers selected by
Kelsey Fisher-Wellman, East Carolina University

Residual Complex I activity and amphidirectional Complex II operation support glutamate catabolism through mtSLP in anoxia.
Targeting Erbin-mitochondria axis in platelets/megakaryocytes promotes B cell-mediated antitumor immunity.
Covalent inhibition of pro-apoptotic BAX.
LINC complex protein nesprin-2 has pro-apoptotic activity via Bcl-2 family proteins.
Regulation of mitochondrial metabolism by autophagy supports leptin-induced cell migration.
Identification of SLC25A46 interaction interfaces with mitochondrial membrane fusogens Mfn2 and Opa1.
An ETFDH-driven metabolon supports OXPHOS efficiency in skeletal muscle by regulating coenzyme Q homeostasis.
α-Ketoglutarate supplementation and NAD+ modulation enhance metabolic rewiring and radiosensitization in SLC25A1 inhibited cancer cells.
Significance of quantitative analyses of the impact of heterogeneity in mitochondrial content and shape on cell differentiation.
Activation of Ca2+ phosphatase Calcineurin regulates Parkin translocation to mitochondria and mitophagy in flies.
Development of a mouse model expressing a bifunctional glutathione synthesizing enzyme to study glutathione limitation in vivo.
NAD+ dependent UPRmt activation underlies intestinal aging caused by mitochondrial DNA mutations.
Foretinib is effective in acute myeloid leukemia by inhibiting FLT3 and overcoming secondary mutations that drive resistance to quizartinib and gilteritinib.
Cell-free chromatin particles released from dying cells inflict mitochondrial damage and ROS production in living cells.
Tumor cell-intrinsic PD-1 promotes Merkel cell carcinoma growth by activating downstream mTOR-mitochondrial ROS signaling.
The CIpP activator, TR-57, is highly effective as a single agent and in combination with venetoclax against CLL cells in vitro.
In situ architecture of Opa1-dependent mitochondrial cristae remodeling.
Inhibition of NRF2 enhances the acute myeloid leukemia cell death induced by venetoclax via the ferroptosis pathway.
The mitochondrial ATP-dependent potassium channel (mitoKATP) controls skeletal muscle structure and function.
Solid tumor growth depends on an intricate equilibrium of malignant cell states.
Genetically encoded tool for manipulation of ΔΨm identifies the latter as the driver of integrative stress response induced by ATP Synthase dysfunction.
Mitophagy plays a "double-edged sword" role in the radiosensitivity of cancer cells.
Phosphorylation of INF2 by AMPK promotes mitochondrial fission and oncogenic function in endometrial cancer.
Two mitochondrial DNA polymorphisms modulate cardiolipin binding and lead to synthetic lethality.
MTFR2-dependent mitochondrial fission promotes HCC progression.
NAD+ supplementation prevents STING-induced senescence in CD8+ T cells by improving mitochondrial homeostasis.
Cyclic fasting-mimicking diet plus bortezomib and rituximab is an effective treatment for chronic lymphocytic leukemia.
Mitochondrial DNA copy number plays opposing roles in T-lymphocyte infiltration of colorectal cancer based on mismatch repair status: new directions for immunotherapy?

Sci Rep. 2024 Jan 19. 14(1): 1729

Residual Complex I activity and amphidirectional Complex II operation support glutamate catabolism through mtSLP in anoxia.

Dora Ravasz, David Bui, Sara Nazarian, Gergely Pallag, Noemi Karnok, Jennie Roberts, Bryan P Marzullo, Daniel A Tennant, Bennett Greenwood, Alex Kitayev, Collin Hill, Timea Komlódi, Carolina Doerrier, Kristyna Cunatova, Erika Fernandez-Vizarra, Erich Gnaiger, Michael A Kiebish, Alexandra Raska, Krasimir Kolev, Bence Czumbel, Niven R Narain, Thomas N Seyfried, Christos Chinopoulos.

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in the mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in isolated mitochondria in real-time, we demonstrate that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. 13C metabolic tracing or untargeted analysis of metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system showed that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase Complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Complex II operated amphidirectionally during the anoxic event, providing quinones to Complex I and reducing fumarate to succinate. Our results highlight the importance of quinone provision to Complex I oxidizing NADH maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.

DOI: https://doi.org/10.1038/s41598-024-51365-4
Cell Metab. 2024 Jan 03. pii: S1550-4131(23)00471-0. [Epub ahead of print]

Targeting Erbin-mitochondria axis in platelets/megakaryocytes promotes B cell-mediated antitumor immunity.

Zilong Zhang, Xu Xu, Di Zhang, Songsong Zhao, Chuyi Wang, Guilin Zhang, Wenshu Chen, Jinglin Liu, Huimin Gong, Youlutuziayi Rixiati, Shi Li, Tong Shen, Jianming Li.

  The roles of platelets/megakaryocytes (MKs), the key components in the blood system, in the tumor microenvironment and antitumor immunity are unclear. In patients with colorectal cancer, the number of platelets was significantly increased in patients with metastasis, and Erbin expression was highly expressed in platelets from patients with metastases. Moreover, Erbin knockout in platelets/MKs suppressed lung metastasis in mice and promoted aggregations of platelets. Mechanistically, Erbin-deficient platelets have increasing mitochondrial oxidative phosphorylation and secrete lipid metabolites like acyl-carnitine (Acar) by abolishing interaction with prothrombotic protein ESAM. Notably, Acar enhanced the activity of mitochondrial electron transport chain complex and mitochondrial oxidative phosphorylation in B cells by acetylation of H3K27 epigenetically. Targeting Erbin in platelets/MKs by a nanovesicle system dramatically attenuated lung metastasis in mice in vivo. Our study identifies an Erbin-mitochondria axis in platelets/MKs, which suppresses B cell-mediated antitumor immunity, suggesting a new way for the treatment of metastasis.

Keywords:  B cells; colorectal cancer; metastasis; mitochondrial metabolism; platelets/megakaryocytes

DOI:  https://doi.org/10.1016/j.cmet.2023.12.020
Nat Chem Biol. 2024 Jan 17.

Covalent inhibition of pro-apoptotic BAX.

Matthew W McHenry, Peiwen Shi, Christina M Camara, Daniel T Cohen, T Justin Rettenmaier, Utsarga Adhikary, Micah A Gygi, Ka Yang, Steven P Gygi, Thomas E Wales, John R Engen, James A Wells, Loren D Walensky.

BCL-2-associated X protein (BAX) is a promising therapeutic target for activating or restraining apoptosis in diseases of pathologic cell survival or cell death, respectively. In response to cellular stress, BAX transforms from a quiescent cytosolic monomer into a toxic oligomer that permeabilizes the mitochondria, releasing key apoptogenic factors. The mitochondrial lipid trans-2-hexadecenal (t-2-hex) sensitizes BAX activation by covalent derivatization of cysteine 126 (C126). In this study, we performed a disulfide tethering screen to discover C126-reactive molecules that modulate BAX activity. We identified covalent BAX inhibitor 1 (CBI1) as a compound that selectively derivatizes BAX at C126 and inhibits BAX activation by triggering ligands or point mutagenesis. Biochemical and structural analyses revealed that CBI1 can inhibit BAX by a dual mechanism of action: conformational constraint and competitive blockade of lipidation. These data inform a pharmacologic strategy for suppressing apoptosis in diseases of unwanted cell death by covalent targeting of BAX C126.

DOI: https://doi.org/10.1038/s41589-023-01537-6
Cell Death Discov. 2024 Jan 15. 10(1): 29

LINC complex protein nesprin-2 has pro-apoptotic activity via Bcl-2 family proteins.

Liora Lindenboim, Hila Zohar, Gregg G Gundersen, Howard J Worman, Reuven Stein.

The apoptotic intrinsic pathway is initiated by perforation of the mitochondrial outer membrane by the effector pro-apoptotic proteins of the Bcl-2 family, Bax and Bak. Bax and Bak need to be activated, a process facilitated by the action of BH3-only pro-apoptotic members of the Bcl-2 family. The latter either directly activates the effector proteins or antagonizes the action of pro-survival Bcl-2 family members such as Bcl-xL. The nuclear envelope is a known target of the apoptotic machinery; however, it may also act as mediator of apoptosis. We showed previously that the nuclear envelope protein nesprin-2, a component of the linker of nucleoskeleton and cytoskeleton (LINC) complex, can bind to Bax in close proximity to the mitochondria and that the binding increases in apoptotic cells. We now show that depleting nesprin-2 inhibits the apoptotic mitochondrial pathway as measured by Bax and Bak activation and cytochrome c release. This survival effect was Bcl-xL-dependent. Nesprin-2 depletion also inhibited spontaneous exposure of the N-terminus of Bak in cells lacking Bcl-xL and increased the presence of Bcl-xL and Bax in the mitochondria. These results indicate that nesprin-2 promotes Bak activation and regulates mitochondrial translocation/retrotranslocation of Bcl-2 family proteins. Our findings demonstrate a new apoptotic pathway whereby the nuclear envelope, via nesprin-2, regulates apoptosis.

DOI: https://doi.org/10.1038/s41420-023-01763-w
Sci Rep. 2024 01 16. 14(1): 1408

Regulation of mitochondrial metabolism by autophagy supports leptin-induced cell migration.

Alin García-Miranda, José Benito Montes-Alvarado, Fabiola Lilí Sarmiento-Salinas, Verónica Vallejo-Ruiz, Eduardo Castañeda-Saucedo, Napoleón Navarro-Tito, Paola Maycotte.

Leptin is an adipokine secreted by adipose tissue, which promotes tumor progression by activating canonical signaling pathways such as MAPK/ERK. Recent studies have shown that leptin induces autophagy, and this process is involved in leptin-induced characteristics of malignancy. Autophagy is an intracellular degradation process associated with different hallmarks of cancer, such as cell survival, migration, and metabolic reprogramming. However, its relationship with metabolic reprogramming has not been clearly described. The purpose of this study was to determine the role of leptin-induced autophagy in cancer cell metabolism and its association with cellular proliferation and migration in breast cancer cells. We used ER+/PR+ and triple-negative breast cancer cell lines treated with leptin, autophagy inhibition, or mitochondrial metabolism inhibitors. Our results show that leptin induces autophagy, increases proliferation, mitochondrial ATP production and mitochondrial function in ER+/PR+ cells. Importantly, autophagy was required to maintain metabolic changes and cell proliferation driven by leptin. In triple-negative cells, leptin did not induce autophagy or cell proliferation but increased glycolytic and mitochondrial ATP production, mitochondrial function, and cell migration. In triple negative cells, autophagy was required to support metabolic changes and cell migration, and autophagy inhibition decreased cellular migration similar to mitochondrial inhibitors. In conclusion, leptin-induced autophagy supports mitochondrial metabolism in breast cancer cells as well as glycolysis in triple negative cells. Importantly, leptin-induced mitochondrial metabolism promoted cancer cell migration.

DOI: https://doi.org/10.1038/s41598-024-51406-y
bioRxiv. 2023 Dec 29. pii: 2023.12.29.573615. [Epub ahead of print]

Identification of SLC25A46 interaction interfaces with mitochondrial membrane fusogens Mfn2 and Opa1.

Sivakumar Boopathy, Camila Makhlouta Lugo, Bridget E Luce, Julie L McDonald, Pusparanee Hakim, Jackeline Ponce, Beatrix Ueberheide, Luke H Chao.

Mitochondrial fusion requires the sequential merger of four bilayers to two. The outer-membrane solute carrier protein SLC25A46 interacts with both the outer and inner-membrane dynamin family GTPases Mfn1/2 and Opa1. While SLC25A46 levels are known affect mitochondrial morphology, how SLC25A46 interacts with Mfn1/2 and Opa1 to regulate membrane fusion is not understood. In this study, we use crosslinking mass-spectrometry and AlphaFold 2 modeling to identify interfaces mediating a SLC25A46-Opa1-Mfn1/2 complex. We reveal that the bundle signaling element of Opa1 interacts with SLC25A46, and the helical repeat 1 region of Mfn2 interacts with the SLC25A46 N-terminus. We validate these newly identified interaction interfaces and show that they play a role in mitochondrial network maintenance.

DOI: https://doi.org/10.1101/2023.12.29.573615
Nat Metab. 2024 Jan 19.

An ETFDH-driven metabolon supports OXPHOS efficiency in skeletal muscle by regulating coenzyme Q homeostasis.

Juan Cruz Herrero Martín, Beñat Salegi Ansa, Gerardo Álvarez-Rivera, Sonia Domínguez-Zorita, Pilar Rodríguez-Pombo, Belén Pérez, Enrique Calvo, Alberto Paradela, David G Miguez, Alejandro Cifuentes, José M Cuezva, Laura Formentini.

Coenzyme Q (Q) is a key lipid electron transporter, but several aspects of its biosynthesis and redox homeostasis remain undefined. Various flavoproteins reduce ubiquinone (oxidized form of Q) to ubiquinol (QH2); however, in eukaryotes, only oxidative phosphorylation (OXPHOS) complex III (CIII) oxidizes QH2 to Q. The mechanism of action of CIII is still debated. Herein, we show that the Q reductase electron-transfer flavoprotein dehydrogenase (ETFDH) is essential for CIII activity in skeletal muscle. We identify a complex (comprising ETFDH, CIII and the Q-biosynthesis regulator COQ2) that directs electrons from lipid substrates to the respiratory chain, thereby reducing electron leaks and reactive oxygen species production. This metabolon maintains total Q levels, minimizes QH2-reductive stress and improves OXPHOS efficiency. Muscle-specific Etfdh-/- mice develop myopathy due to CIII dysfunction, indicating that ETFDH is a required OXPHOS component and a potential therapeutic target for mitochondrial redox medicine.

DOI: https://doi.org/10.1038/s42255-023-00956-y
Cell Death Discov. 2024 Jan 15. 10(1): 27

α-Ketoglutarate supplementation and NAD+ modulation enhance metabolic rewiring and radiosensitization in SLC25A1 inhibited cancer cells.

Kexu Xiang, Mikhail Kunin, Safa Larafa, Maike Busch, Nicole Dünker, Verena Jendrossek, Johann Matschke.

Metabolic rewiring is the result of the increasing demands and proliferation of cancer cells, leading to changes in the biological activities and responses to treatment of cancer cells. The mitochondrial citrate transport protein SLC25A1 is involved in metabolic reprogramming offering a strategy to induce metabolic bottlenecks relevant to radiosensitization through the accumulation of the oncometabolite D-2-hydroxyglutarate (D-2HG) upon SLC25A1 inhibition (SLC25A1i). Previous studies have revealed the comparative effects of SLC25A1i or cell-permeable D-2HG (octyl-D-2HG) treatments on DNA damage induction and repair, as well as on energy metabolism and cellular function, which are crucial for the long-term survival of irradiated cells. Here, α-ketoglutarate (αKG), the precursor of D-2HG, potentiated the effects observed upon SLC25A1i on DNA damage repair, cell function and long-term survival in vitro and in vivo, rendering NCI-H460 cancer cells more vulnerable to ionizing radiation. However, αKG treatment alone had little effect on these phenotypes. In addition, supplementation with nicotinamide (NAM), a precursor of NAD (including NAD+ and NADH), counteracted the effects of SLC25A1i or the combination of SLC25A1i with αKG, highlighting a potential importance of the NAD+/NADH balance on cellular activities relevant to the survival of irradiated cancer cells upon SLC25A1i. Furthermore, inhibition of histone lysine demethylases (KDMs), as a major factor affected upon SLC25A1i, by JIB04 treatment alone or in combination with αKG supplementation phenocopied the broad effects on mitochondrial and cellular function induced by SLC25A1i. Taken together, αKG supplementation potentiated the effects on cellular processes observed upon SLC25A1i and increased the cellular demand for NAD to rebalance the cellular state and ensure survival after irradiation. Future studies will elucidate the underlying metabolic reprogramming induced by SLC25A1i and provide novel therapeutic strategies for cancer treatment.

DOI: https://doi.org/10.1038/s41420-024-01805-x
Open Biol. 2024 Jan;14(1): 230279

Significance of quantitative analyses of the impact of heterogeneity in mitochondrial content and shape on cell differentiation.

Swati Agarwala, Sukhamoy Dhabal, Kasturi Mitra.

  Mitochondria, classically known as the powerhouse of cells, are unique double membrane-bound multifaceted organelles carrying a genome. Mitochondrial content varies between cell types and precisely doubles within cells during each proliferating cycle. Mitochondrial content also increases to a variable degree during cell differentiation triggered after exit from the proliferating cycle. The mitochondrial content is primarily maintained by the regulation of mitochondrial biogenesis, while damaged mitochondria are eliminated from the cells by mitophagy. In any cell with a given mitochondrial content, the steady-state mitochondrial number and shape are determined by a balance between mitochondrial fission and fusion processes. The increase in mitochondrial content and alteration in mitochondrial fission and fusion are causatively linked with the process of differentiation. Here, we critically review the quantitative aspects in the detection methods of mitochondrial content and shape. Thereafter, we quantitatively link these mitochondrial properties in differentiating cells and highlight the implications of such quantitative link on stem cell functionality. Finally, we discuss an example of cell size regulation predicted from quantitative analysis of mitochondrial shape and content. To highlight the significance of quantitative analyses of these mitochondrial properties, we propose three independent rationale based hypotheses and the relevant experimental designs to test them.

Keywords:  cell differentiation; cell proliferation; mitochondrial content; mitochondrial heterogeneity; mitochondrial shape; stem cells

DOI:  https://doi.org/10.1098/rsob.230279
Cell Death Differ. 2024 Jan 18.

Activation of Ca2+ phosphatase Calcineurin regulates Parkin translocation to mitochondria and mitophagy in flies.

Elena Marchesan, Alice Nardin, Sofia Mauri, Greta Bernardo, Vivek Chander, Simone Di Paola, Monica Chinellato, Sophia von Stockum, Joy Chakraborty, Stephanie Herkenne, Valentina Basso, Emilie Schrepfer, Oriano Marin, Laura Cendron, Diego L Medina, Luca Scorrano, Elena Ziviani.

Selective removal of dysfunctional mitochondria via autophagy is crucial for the maintenance of cellular homeostasis. This event is initiated by the translocation of the E3 ubiquitin ligase Parkin to damaged mitochondria, and it requires the Serine/Threonine-protein kinase PINK1. In a coordinated set of events, PINK1 operates upstream of Parkin in a linear pathway that leads to the phosphorylation of Parkin, Ubiquitin, and Parkin mitochondrial substrates, to promote ubiquitination of outer mitochondrial membrane proteins. Ubiquitin-decorated mitochondria are selectively recruiting autophagy receptors, which are required to terminate the organelle via autophagy. In this work, we show a previously uncharacterized molecular pathway that correlates the activation of the Ca2+-dependent phosphatase Calcineurin to Parkin translocation and Parkin-dependent mitophagy. Calcineurin downregulation or genetic inhibition prevents Parkin translocation to CCCP-treated mitochondria and impairs stress-induced mitophagy, whereas Calcineurin activation promotes Parkin mitochondrial recruitment and basal mitophagy. Calcineurin interacts with Parkin, and promotes Parkin translocation in the absence of PINK1, but requires PINK1 expression to execute mitophagy in MEF cells. Genetic activation of Calcineurin in vivo boosts basal mitophagy in neurons and corrects locomotor dysfunction and mitochondrial respiratory defects of a Drosophila model of impaired mitochondrial functions. Our study identifies Calcineurin as a novel key player in the regulation of Parkin translocation and mitophagy.

DOI: https://doi.org/10.1038/s41418-023-01251-9
J Biol Chem. 2024 Jan 11. pii: S0021-9258(24)00021-8. [Epub ahead of print] 105645

Development of a mouse model expressing a bifunctional glutathione synthesizing enzyme to study glutathione limitation in vivo.

Rebecca C Timson, Artem Khan, Beste Uygur, Marwa Saad, Hsi-Wen Yeh, Nicole L DelGaudio, Ross Weber, Hanan Alwaseem, Jing Gao, Chingwen Yang, Kıvanç Birsoy.

Glutathione (GSH) is a highly abundant tripeptide thiol that performs diverse protective and biosynthetic functions in cells. While changes in GSH availability are associated with inborn errors of metabolism, cancer and neurodegenerative disorders, studying the limiting role of GSH in physiology and disease has been challenging due to its tight regulation. To address this, we generated cell and mouse models that express a bifunctional glutathione-synthesizing enzyme from Streptococcus thermophilus (GshF), which possesses both glutamate-cysteine ligase and glutathione synthase activities. GshF expression allows efficient production of GSH in the cytosol and mitochondria and prevents cell death in response to GSH depletion, but not ferroptosis induction, indicating that GSH is not a limiting factor under lipid peroxidation. CRISPR screens using engineered enzymes further revealed genes required for cell proliferation under cellular and mitochondrial GSH depletion. Among these, we identified the glutamate-cysteine ligase modifier subunit, Gclm, as a requirement for cellular sensitivity to buthionine sulfoximne, a glutathione synthesis inhibitor. Finally, GshF expression in mice is embryonically lethal but sustains postnatal viability when restricted to adulthood. Overall, our work identifies a conditional mouse model to investigate the limiting role of GSH in physiology and disease.

DOI: https://doi.org/10.1016/j.jbc.2024.105645
Nat Commun. 2024 Jan 16. 15(1): 546

NAD+ dependent UPRmt activation underlies intestinal aging caused by mitochondrial DNA mutations.

Liang Yang, Zifeng Ruan, Xiaobing Lin, Hao Wang, Yanmin Xin, Haite Tang, Zhijuan Hu, Yunhao Zhou, Yi Wu, Junwei Wang, Dajiang Qin, Gang Lu, Kerry M Loomes, Wai-Yee Chan, Xingguo Liu.

Aging in mammals is accompanied by an imbalance of intestinal homeostasis and accumulation of mitochondrial DNA (mtDNA) mutations. However, little is known about how accumulated mtDNA mutations modulate intestinal homeostasis. We observe the accumulation of mtDNA mutations in the small intestine of aged male mice, suggesting an association with physiological intestinal aging. Using polymerase gamma (POLG) mutator mice and wild-type mice, we generate male mice with progressive mtDNA mutation burdens. Investigation utilizing organoid technology and in vivo intestinal stem cell labeling reveals decreased colony formation efficiency of intestinal crypts and LGR5-expressing intestinal stem cells in response to a threshold mtDNA mutation burden. Mechanistically, increased mtDNA mutation burden exacerbates the aging phenotype of the small intestine through ATF5 dependent mitochondrial unfolded protein response (UPRmt) activation. This aging phenotype is reversed by supplementation with the NAD+ precursor, NMN. Thus, we uncover a NAD+ dependent UPRmt triggered by mtDNA mutations that regulates the intestinal aging.

DOI: https://doi.org/10.1038/s41467-024-44808-z
Cancer Res. 2024 Jan 17.

Foretinib is effective in acute myeloid leukemia by inhibiting FLT3 and overcoming secondary mutations that drive resistance to quizartinib and gilteritinib.

Peihong Wang, Yvyin Zhang, Rufang Xiang, Jie Yang, Yanli Xu, Tingfen Deng, Wei Zhou, Caixia Wang, Xinhua Xiao, Shunqing Wang.

FLT3 internal tandem duplication (FLT3-ITD) mutations are one of the most prevalent somatic alterations associated with poor prognosis in patients with acute myeloid leukemia (AML). The clinically-approved FLT3 kinase inhibitors gilteritinib and quizartinib improve the survival of AML patients with FLT3-ITD mutations, but their long-term efficacy is limited by acquisition of secondary drug-resistant mutations. In this study, we conducted virtual screening of a library of 60411 small molecules and identified foretinib as a potent FLT3 inhibitor. An integrated analysis of the BeatAML database showed that foretinib had a lower IC50 value than other existing FLT3 inhibitors in FLT3-ITD AML patients. Foretinib directly bound to FLT3 and effectively inhibited FLT3 signaling. Foretinib potently inhibited proliferation and promoted apoptosis in human AML cell lines and primary AML cells with FLT3-ITD mutations. Foretinib also significantly extended the survival of mice bearing cell-derived and patient-derived FLT3-ITD xenografts, exhibiting stronger efficacy than clinically-approved FLT3 inhibitors in treating FLT3-ITD AML. Moreover, foretinib showed potent activity against secondary mutations of FLT3-ITD that confer resistance to quizartinib and gilteritinib. These findings support the potential of foretinib for treating AML patients with FLT3-ITD mutations, especially for those carrying secondary mutations after treatment failure with other FLT3 inhibitors.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-1534
Cell Death Discov. 2024 Jan 15. 10(1): 30

Cell-free chromatin particles released from dying cells inflict mitochondrial damage and ROS production in living cells.

Gorantla V Raghuram, Bhabesh Kumar Tripathy, Kartikeya Avadhani, Snehal Shabrish, Naveen Kumar Khare, Relestina Lopes, Kavita Pal, Indraneel Mittra.

Mitochondrial damage and the resultant oxidative stress are associated with neurodegenerative diseases, ageing, and cancer. However, the triggers of mitochondrial damage remain unclear. We previously reported that cell-free chromatin particles (cfChPs) released from the billions of cells that die in the body every day can readily enter healthy cells and damage their DNA. Here, we show that cfChPs isolated from the sera of healthy individuals, when applied to NIH3T3 mouse fibroblast cells, cause physical damage to mitochondrial DNA (mtDNA). cfChPs also induce ultrastructural changes, increase mitochondrial mass, alter mitochondrial shape, upregulate mitochondrial outer membrane protein translocase of the outer membrane 20, and change mitochondrial membrane potential. Furthermore, a marked increase was observed in mitochondrial superoxide (ROS) production, as detected by MitoSOX Red, and intracellular superoxide dismutase-1 activation. ROS production was also activated when a conditioned medium containing cfChPs released from hypoxia-induced dying NIH3T3 cells was applied to healthy NIH3T3 cells. ROS activation was significantly reduced when the conditioned medium was pre-treated with three different cfChP-deactivating agents: anti-histone antibody-complexed nanoparticles, DNase I, and the novel pro-oxidant combination of the nutraceuticals resveratrol and copper. Given that 1 × 109-1 × 1012 cells die in the body every day, we hypothesise that cfChPs from dying cells are the major physiological triggers for mtDNA damage and ROS production. Deactivation of cfChPs may provide a novel therapeutic approach to retard ageing and associated degenerative conditions linked to oxidative stress.

DOI: https://doi.org/10.1038/s41420-023-01728-z
Sci Adv. 2024 Jan 19. 10(3): eadi2012

Tumor cell-intrinsic PD-1 promotes Merkel cell carcinoma growth by activating downstream mTOR-mitochondrial ROS signaling.

Christina Martins, Erik Rasbach, Markus V Heppt, Praveen Singh, Zsofi Kulcsar, Julia Holzgruber, Asmi Chakraborty, Kyla Mucciarone, Sonja Kleffel, Anne Brandenburg, Wolfram Hoetzenecker, Nuh N Rahbari, James A DeCaprio, Manisha Thakuria, George F Murphy, Matthew R Ramsey, Christian Posch, Steven R Barthel, Tobias Schatton.

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer. Inhibitors targeting the programmed cell death 1 (PD-1) immune checkpoint have improved MCC patient outcomes by boosting antitumor T cell immunity. Here, we identify PD-1 as a growth-promoting receptor intrinsic to MCC cells. In human MCC lines and clinical tumors, RT-PCR-based sequencing, immunoblotting, flow cytometry, and immunofluorescence analyses demonstrated PD-1 gene and protein expression by MCC cells. MCC-PD-1 ligation enhanced, and its inhibition or silencing suppressed, in vitro proliferation and in vivo tumor xenograft growth. Consistently, MCC-PD-1 binding to PD-L1 or PD-L2 induced, while antibody-mediated PD-1 blockade inhibited, protumorigenic mTOR signaling, mitochondrial (mt) respiration, and ROS generation. Last, pharmacologic inhibition of mTOR or mtROS reversed MCC-PD-1:PD-L1-dependent proliferation and synergized with PD-1 checkpoint blockade in suppressing tumorigenesis. Our results identify an MCC-PD-1-mTOR-mtROS axis as a tumor growth-accelerating mechanism, the blockade of which might contribute to clinical response in patients with MCC.

DOI: https://doi.org/10.1126/sciadv.adi2012
Leuk Lymphoma. 2024 Jan 16. 1-13

The CIpP activator, TR-57, is highly effective as a single agent and in combination with venetoclax against CLL cells in vitro.

Narjis Fatima, Yandong Shen, Kyle Crassini, Olivia Burling, Lauren Thurgood, Edwin J Iwanowicz, Henk Lang, Donald S Karanewsky, Richard I Christopherson, Stephen P Mulligan, O Giles Best.

  Despite advances in treatment, a significant proportion of patients with chronic lymphocytic leukemia (CLL) will relapse with drug-resistant disease.The imipridones, ONC-201 and ONC-212, are effective against a range of different cancers, including acute myeloid leukemia (AML) and tumors of the brain, breast, and prostate. These drugs induce cell death through activation of the mitochondrial protease, caseinolytic protease (CIpP), and the unfolded protein response (UPR).Here we demonstrate that the novel imipridone analog, TR-57, has efficacy as a single agent and synergises with venetoclax against CLL cells under in vitro conditions that mimic the tumor microenvironment. Changes in protein expression suggest TR-57 activates the UPR, inhibits the AKT and ERK1/2 pathways and induces pro-apoptotic changes in the expression of proteins of the BCL-2 family.The study suggests that TR-57, as a single agent and in combination with venetoclax, may represent an effective treatment option for CLL.

Keywords:  Chronic lymphocytic leukemia; ClpP (mitochondrial ATP-dependent Caseinolytic protease P subunit); TR-compounds; imipridone; tumor microenvironment; venetoclax

DOI:  https://doi.org/10.1080/10428194.2023.2300055
EMBO J. 2024 Jan 15.

In situ architecture of Opa1-dependent mitochondrial cristae remodeling.

Michelle Y Fry, Paula P Navarro, Pusparanee Hakim, Virly Y Ananda, Xingping Qin, Juan C Landoni, Sneha Rath, Zintis Inde, Camila Makhlouta Lugo, Bridget E Luce, Yifan Ge, Julie L McDonald, Ilzat Ali, Leillani L Ha, Benjamin P Kleinstiver, David C Chan, Kristopher A Sarosiek, Luke H Chao.

  Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria, while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and show a compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling.

Keywords:  Cristae Remodeling; Cryo-Electron Tomography; Cryo-Focused Ion Beam Milling; Mitochondrial Biology

DOI:  https://doi.org/10.1038/s44318-024-00027-2
Cell Death Discov. 2024 Jan 18. 10(1): 35

Inhibition of NRF2 enhances the acute myeloid leukemia cell death induced by venetoclax via the ferroptosis pathway.

Xibao Yu, Yan Wang, Jiaxiong Tan, Yuchen Li, Pengyue Yang, Xuan Liu, Jing Lai, Yue Zhang, Letong Cai, Yinfeng Gu, Ling Xu, Yangqiu Li.

Venetoclax, an inhibitor that selectively targets B cell lymphoma-2 (BCL-2) that has been approved for treating adult acute myeloid leukemia (AML) in combination with hypomethylating agents. However, its short duration of response and emergence of resistance are significant issues. In this study, we found that the sensitivity of AML cells to venetoclax was considerably enhanced by ML385, an inhibitor of the ferroptosis factor nuclear transcription factor erythroid 2-related factor 2 (NRF2). Using AML samples, we verified that NRF2 and its target gene ferritin heavy chain 1 (FTH1) were highly expressed in patients with AML and correlated with poor prognosis. Downregulation of NRF2 could inhibit FTH1 expression and significantly enhance the venetoclax-induced labile iron pool and lipid peroxidation. By contrast, NRF2 overexpression or administration of the reactive oxygen species inhibitor N-acetylcysteine and vitamin E could effectively suppress the anti-AML effects of ML385+venetoclax. Furthermore, the ferroptosis inducer erastin increased the anti-AML effects of venetoclax. Our study demonstrated that NRF2 inhibition could enhance the AML cell death induced by venetoclax via the ferroptosis pathway. Thus, the combination of ML385 with venetoclax may offer a favorable strategy for AML treatment.

DOI: https://doi.org/10.1038/s41420-024-01800-2
Cell Death Dis. 2024 Jan 17. 15(1): 58

The mitochondrial ATP-dependent potassium channel (mitoKATP) controls skeletal muscle structure and function.

Giulia Di Marco, Gaia Gherardi, Agnese De Mario, Ilaria Piazza, Martina Baraldo, Andrea Mattarei, Bert Blaauw, Rosario Rizzuto, Diego De Stefani, Cristina Mammucari.

MitoKATP is a channel of the inner mitochondrial membrane that controls mitochondrial K+ influx according to ATP availability. Recently, the genes encoding the pore-forming (MITOK) and the regulatory ATP-sensitive (MITOSUR) subunits of mitoKATP were identified, allowing the genetic manipulation of the channel. Here, we analyzed the role of mitoKATP in determining skeletal muscle structure and activity. Mitok-/- muscles were characterized by mitochondrial cristae remodeling and defective oxidative metabolism, with consequent impairment of exercise performance and altered response to damaging muscle contractions. On the other hand, constitutive mitochondrial K+ influx by MITOK overexpression in the skeletal muscle triggered overt mitochondrial dysfunction and energy default, increased protein polyubiquitination, aberrant autophagy flux, and induction of a stress response program. MITOK overexpressing muscles were therefore severely atrophic. Thus, the proper modulation of mitoKATP activity is required for the maintenance of skeletal muscle homeostasis and function.

DOI: https://doi.org/10.1038/s41419-024-06426-x
bioRxiv. 2023 Dec 30. pii: 2023.12.30.573100. [Epub ahead of print]

Solid tumor growth depends on an intricate equilibrium of malignant cell states.

Stefan R Torborg, Olivera Grbovic-Huezo, Anupriya Singhal, Matilda Holm, Katherine Wu, Xuexiang Han, Yu-Jui Ho, Caj Haglund, Michael J Mitchell, Scott W Lowe, Lukas E Dow, Kenneth L Pitter, Francisco J Sanchez-Rivera, Andre Levchenko, Tuomas Tammela.

Control of cell identity and number is central to tissue function, yet principles governing organization of malignant cells in tumor tissues remain poorly understood. Using mathematical modeling and candidate-based analysis, we discover primary and metastatic pancreatic ductal adenocarcinoma (PDAC) organize in a stereotypic pattern whereby PDAC cells responding to WNT signals (WNT-R) neighbor WNT-secreting cancer cells (WNT-S). Leveraging lineage-tracing, we reveal the WNT-R state is transient and gives rise to the WNT-S state that is highly stable and committed to organizing malignant tissue. We further show that a subset of WNT-S cells expressing the Notch ligand DLL1 form a functional niche for WNT-R cells. Genetic inactivation of WNT secretion or Notch pathway components, or cytoablation of the WNT-S state disrupts PDAC tissue organization, suppressing tumor growth and metastasis. This work indicates PDAC growth depends on an intricately controlled equilibrium of functionally distinct cancer cell states, uncovering a fundamental principle governing solid tumor growth and revealing new opportunities for therapeutic intervention.

DOI: https://doi.org/10.1101/2023.12.30.573100
bioRxiv. 2023 Dec 27. pii: 2023.12.27.573435. [Epub ahead of print]

Genetically encoded tool for manipulation of ΔΨm identifies the latter as the driver of integrative stress response induced by ATP Synthase dysfunction.

Mangyu Choe, Denis V Titov.

Mitochondrial membrane potential (ΔΨm) is one of the key parameters controlling cellular bioenergetics. Investigation of the role of ΔΨm in live cells is complicated by a lack of tools for its direct manipulation without off-target effects. Here, we adopted the uncoupling protein UCP1 from brown adipocytes as a genetically encoded tool for direct manipulation of ΔΨm. We validated the ability of exogenously expressed UCP1 to induce uncoupled respiration and lower ΔΨm in mammalian cells. UCP1 expression lowered ΔΨm to the same extent as chemical uncouplers but did not inhibit cell proliferation, suggesting that it manipulates ΔΨm without the off-target effects of chemical uncouplers. Using UCP1, we revealed that elevated ΔΨm is the driver of the Integrated Stress Response induced by ATP synthase inhibition in mammalian cells.

DOI: https://doi.org/10.1101/2023.12.27.573435
J Cancer Res Clin Oncol. 2024 Jan 18. 150(1): 14

Mitophagy plays a "double-edged sword" role in the radiosensitivity of cancer cells.

Qian Wang, Chengxin Liu.

  Mitochondria are organelles with double-membrane structure of inner and outer membrane, which provides main energy support for cell growth and metabolism. Reactive oxygen species (ROS) mainly comes from mitochondrial and can cause irreversible damage to cells under oxidative stress. Thus, mitochondrial homeostasis is the basis for maintaining the normal physiological function of cells and mitophagy plays a pivotal role in the maintenance of mitochondrial homeostasis. At present, to enhance the sensitivity of cancer cells to radiotherapy and chemotherapy by regulating mitochondria has increasingly become a hot spot of cancer therapy. It is particularly important to study the effect of ionizing radiation (IR) on mitochondria and the role of mitophagy in the radiosensitivity of cancer cells. Most of the existing reviews have focused on mitophagy-related molecules or pathways and the impact of mitophagy on diseases. In this review, we mainly focus on discussing the relationship between mitophagy and radiosensitivity of cancer cells around mitochondria and IR.

Keywords:  Cancer; Ionizing radiation; Mitophagy; Radiosensitivity

DOI:  https://doi.org/10.1007/s00432-023-05515-2
Cell Death Dis. 2024 Jan 17. 15(1): 65

Phosphorylation of INF2 by AMPK promotes mitochondrial fission and oncogenic function in endometrial cancer.

Yan Ding, Zeheng Lv, Wenxin Cao, Wenming Shi, Qizhi He, Kun Gao.

Mitochondria are highly dynamic organelles capable of altering their sizes and shapes to maintain metabolic balance through coordinated fission and fusion processes. In various cancer types, mitochondrial hyperfragmentation has been frequently observed, contributing to the progression of cancer toward metastasis. Inverted formin 2 (INF2), which resides in the endoplasmic reticulum (ER), has been found to accelerate actin polymerization and drive mitochondrial fission. In this study, we demonstrate that INF2 expression is significantly upregulated in endometrial cancer (EC) and is associated with a poor prognosis in EC patients. INF2 promotes anchorage-dependent and independent EC cell growth in part by facilitating mitochondrial fission. Furthermore, in conditions of energy stress, AMP-activated protein kinase (AMPK) phosphorylates INF2 at Ser1077, leading to increased localization of INF2 to the ER and enhanced recruitment of the dynamin-related protein 1 (DRP1) to mitochondria. This AMPK-mediated phosphorylation of INF2 at Ser1077 facilitates mitochondrial division and promotes EC cell growth. Pathological examination using immunohistochemical analyses revealed a positive correlation between AMPK activity and phosphorylated INF2 (Ser1077) in EC specimens. Collectively, our findings uncover novel molecular mechanisms involving the AMPK-INF2 axis, which regulates mitochondrial dynamics and malignant cell growth in EC.

DOI: https://doi.org/10.1038/s41419-024-06431-0
Nat Commun. 2024 Jan 19. 15(1): 611

Two mitochondrial DNA polymorphisms modulate cardiolipin binding and lead to synthetic lethality.

Ason C Y Chiang, Jan Ježek, Peiqiang Mu, Ying Di, Anna Klucnika, Martin Jabůrek, Petr Ježek, Hansong Ma.

Genetic screens have been used extensively to probe interactions between nuclear genes and their impact on phenotypes. Probing interactions between mitochondrial genes and their phenotypic outcome, however, has not been possible due to a lack of tools to map the responsible polymorphisms. Here, using a toolkit we previously established in Drosophila, we isolate over 300 recombinant mitochondrial genomes and map a naturally occurring polymorphism at the cytochrome c oxidase III residue 109 (CoIII109) that fully rescues the lethality and other defects associated with a point mutation in cytochrome c oxidase I (CoIT300I). Through lipidomics profiling, biochemical assays and phenotypic analyses, we show that the CoIII109 polymorphism modulates cardiolipin binding to prevent complex IV instability caused by the CoIT300I mutation. This study demonstrates the feasibility of genetic interaction screens in animal mitochondrial DNA. It unwraps the complex intra-genomic interplays underlying disorders linked to mitochondrial DNA and how they influence disease expression.

DOI: https://doi.org/10.1038/s41467-024-44964-2
J Transl Med. 2024 Jan 18. 22(1): 73

MTFR2-dependent mitochondrial fission promotes HCC progression.

La Zhang, Xiuzhen Zhang, Haichuan Liu, Changhong Yang, Jiyao Yu, Wei Zhao, Jiao Guo, Baoyong Zhou, Ning Jiang.

   BACKGROUND: The role of mitochondrial dynamics, encompassing fission, fusion, and mitophagy, in cancer progression has been extensively studied. However, the specific impact of mitochondrial dynamics on hepatocellular carcinoma (HCC) is still under investigation.
METHODS: In this study, mitochondrial dynamic genes were obtained from the MitoCarta 3.0 database, and gene expression data were collected from The Cancer Genome Atlas (TCGA) database. Based on the expression of these dynamic genes and differentially expressed genes (DEGs), patients were stratified into two clusters. Subsequently, a prognostic model was constructed using univariate COX regression and the least absolute shrinkage and selection operator (LASSO) regression, and the prognostic signature was evaluated. We analyzed the interaction between these model genes and dynamic genes to identify hub genes and reveal mitochondrial status. Furthermore, we assessed immune infiltration, tumor mutational burden (TMB), tumor stemness indices (TSI), and the response to immune checkpoint block (ICB) therapy using the TIDE algorithm and risk scores. Additionally, transmission electron microscopy (TEM), hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), western blotting (WB), and immunofluorescence (IF) were conducted to afford detailed visualization of the morphology of the mitochondria and the expression patterns of fission-associated proteins.
RESULTS: Patients in Cluster 2 exhibited heightened mitochondrial fission and had a worse prognosis. The up-regulated dynamic genes in Cluster 2 were identified as fission genes. GO/KEGG analyses reconfirmed the connection of Cluster 2 to augmented mitochondrial fission activities. Subsequently, a ten-gene prognostic signature based on the differentially expressed genes between the two clusters was generated, with all ten genes being up-regulated in the high-risk group. Moreover, the potential links between these ten signature genes and mitochondrial dynamics were explored, suggesting their involvement in mediating mitochondrial fission through interaction with MTFR2. Further investigation revealed that the high-risk group had an unfavorable prognosis, with a higher mutation frequency of TP53, increased immune checkpoint expression, a higher TIS score, and a lower TIDE score. The mitochondrial imbalance characterized by increased fission and upregulated MTFR2 and DNM1L expression was substantiated in both HCC specimens and cell lines.
CONCLUSIONS: In conclusion, we developed a novel MTFR2-related prognostic signature comprising ten mitochondrial dynamics genes. These genes play crucial roles in mitochondrial fission and have the potential to serve as important predictors and therapeutic targets for HCC.

Keywords:  Fission; Hepatocellular carcinoma; MTFR2; Mitochondrial dynamics; Prognostic model

DOI:  https://doi.org/10.1186/s12967-023-04845-6
J Cell Biochem. 2024 Jan 15.

NAD+ supplementation prevents STING-induced senescence in CD8+ T cells by improving mitochondrial homeostasis.

Bin Ye, Yingting Pei, Lujing Wang, Dehao Meng, Yu Zhang, Shuang Zou, Henian Li, Jinying Liu, Ziying Xie, Changhong Tian, Yuqi Jiang, Yu Qiao, Xu Gao, Yanfen Zhang, Ning Ma.

  Understanding the connection between senescence phenotypes and mitochondrial dysfunction is crucial in aging and premature aging diseases. Loss of mitochondrial function leads to a decline in T cell function, which plays a significant role in this process. However, more research is required to determine if improving mitochondrial homeostasis alleviates senescence phenotypes. Our research has shown an association between NAD+ and senescent T cells through the cGAS-STING pathway, which can lead to an inflammatory phenotype. Further research is needed to fully understand the role of NAD+ in T-cell aging and how it can be utilized to improve mitochondrial homeostasis and alleviate senescence phenotypes. We demonstrate here that mitochondrial dysfunction and cellular senescence with a senescence-associated secretory phenotype (SASP) occur in senescent T cells and tumor-bearing mice. Senescence is mediated by a stimulator of interferon genes (STING) and involves ectopic cytoplasmic DNA. We further show that boosting intracellular NAD+ levels with nicotinamide mononucleotide (NMN) prevents senescence and SASP by promoting mitophagy. NMN treatment also suppresses senescence and neuroinflammation and improves the survival cycle of mice. Encouraging mitophagy may be a useful strategy to prevent CD8+ T cells from senescence due to mitochondrial dysfunction. Additionally, supplementing with NMN to increase NAD+ levels could enhance survival rates in mice while also reducing senescence and inflammation, and enhancing mitophagy as a potential therapeutic intervention.

Keywords:  SASP; cGAS-STING; mitochondria; nicotinamide mononucleotide; senescence

DOI:  https://doi.org/10.1002/jcb.30522
Cancer Res. 2024 Jan 19.

Cyclic fasting-mimicking diet plus bortezomib and rituximab is an effective treatment for chronic lymphocytic leukemia.

Franca Raucci, Claudio Vernieri, Maira Di Tano, Francesca Ligorio, Olga Blaževitš, Samuel Lazzeri, Anastasiya Shmahala, Giuseppe Fragale, Giulia Salvadori, Gabriele Varano, Stefano Casola, Roberta Buono, Euplio Visco, Filippo de Braud, Valter D Longo.

Cyclic fasting-mimicking diet (FMD) is an experimental nutritional intervention with potent antitumor activity in preclinical models of solid malignancies. FMD cycles are also safe and active metabolically and immunologically in cancer patients. Here, we reported on the outcome of FMD cycles in two chronic lymphocytic leukemia (CLL) patients and investigated the effects of fasting and FMD cycles in pre-clinical CLL models. Fasting mimicking conditions in murine CLL models had mild cytotoxic effects, which resulted in apoptosis activation mediated in part by lowered insulin and IGF-1 concentrations. In CLL cells, fasting conditions promoted an increase in proteasome activity that served as a starvation escape pathway. Pharmacological inhibition of this escape mechanism with the proteasome inhibitor bortezomib (BTZ) resulted in a strong enhancement of the pro-apoptotic effects of starvation conditions in vitro. In mouse CLL models, combining cyclic fasting/FMD with BTZ and rituximab (RTX), an anti-CD20 antibody, delayed CLL progression and resulted in significant prolongation of mouse survival. Overall, the effect of proteasome inhibition in combination with FMD cycles in promoting CLL death supports the targeting of starvation escape pathways as an effective treatment strategy that should be tested in clinical trials.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-0295
Br J Cancer. 2024 Jan 13.

Mitochondrial DNA copy number plays opposing roles in T-lymphocyte infiltration of colorectal cancer based on mismatch repair status: new directions for immunotherapy?

Mian Chen, Huashan Liu, Wenfeng Liang, Pinzhu Huang, Fujin Ye, Yebing Cai, Zhenxing Liang, Li Xiong, Liang Kang, Liang Huang.

BACKGROUND: Researchers have previously reported that mitochondrial DNA copy number (mtDNA-CN) can play different roles in microsatellite instable/mismatch repair-deficient (MSI/dMMR) and microsatellite stable/mismatch repair-proficient (MSS/pMMR) colorectal cancer (CRC). To support malignancy, dMMR CRC relies on glycolysis, while pMMR CRC favors oxidative phosphorylation. However, it is unclear whether mtDNA-CN changes are related to T cell infiltration in CRC.
METHODS: The mtDNA-CN was detected by qRT-PCR in 532 patients, and the expression of CD3 and CD8 in 485 patients was detected by immunohistochemistry. The correlation between mtDNA-CN and the prognosis of CRC patients was further analyzed, and the correlation between mtDNA-CN and T lymphocyte infiltration was also analyzed. Biopsy specimens from the immune checkpoint inhibitors (ICIs) treatment cohort were obtained to verify the correlation between mtDNA-CN and the efficacy of ICIs. The effects of mtDNA-CN and MMR status on gene expression were analyzed by RNA-seq.
RESULTS: Our results show that mtDNA-CN has inverse relationships to CRC prognosis in cases with different MMR statuses, potentially inducing the U-shaped association in CRC. The opposing correlations between mtDNA-CN and T lymphocyte infiltration in cases of dMMR CRC and pMMR CRC further suggest that mtDNA-CN might play an important role in CRC development. More importantly, cases of pMMR CRC with lower mtDNA-CN and of dMMR CRC with higher mtDNA-CN can benefit more dramatically from ICIs. Furthermore, RNA-seq revealed a link between the level of mtDNA-CN and T lymphocyte infiltration in CRC cases with different MMR statuses.
CONCLUSION: Our study found a potential relationship between mtDNA-CN and CRC development that differs by MMR status, potentially providing a rationale for the use of mtDNA-CN as both a predictive biomarker and a therapeutic target for ICIs.

DOI: https://doi.org/10.1038/s41416-023-02568-5