BACKGROUND: Mitochondrial transfer is becoming recognized as an important immunomodulatory mechanism used by mesenchymal stem cells (MSCs) to influence immune cells. While effects on T cells and macrophages have been documented, the influence on B cells remains unexplored. This study investigates the modulation of B lymphocyte fate by MSC-mediated mitochondrial transfer. METHODS: MSCs labelled with MitoTracker dyes or derived from mito::mKate2 transgenic mice were co-cultured with splenocytes. Flow cytometry assessed mitochondrial transfer, reactive oxygen species (ROS) levels, apoptosis and mitophagy. Glucose uptake was measured using the 2-NBDG assay. RNA sequencing analysed gene expression changes in CD19+ mitochondria recipients and nonrecipients. Pathway analysis identified affected processes. In an LPS-induced inflammation model, mito::mKate2 MSCs were administered, and B cells from different organs were analysed for mitochondrial uptake and phenotypic changes. MSC-derived mitochondria were also isolated to confirm uptake by FACS-sorted CD19+ cells. RESULTS: MSCs transferred mitochondria to CD19+ cells, though less than to other immune cells. Transfer correlated with ROS levels and mitophagy induction. Mitochondria were preferentially acquired by activated B cells, as indicated by increased CD69 expression and glycolytic activity. Bidirectional transfer occurred, with immune cells exchanging dysfunctional mitochondria for functional ones. CD19+ recipients exhibited increased viability, proliferation and altered gene expression, with upregulated cell division genes and downregulated antigen presentation genes. In vivo, mitochondrial acquisition reduced B cell activation and inflammatory cytokine production. Pre-sorted B cells also acquired isolated mitochondria, exhibiting a similar anti-inflammatory phenotype. CONCLUSIONS: These findings highlight mitochondrial trafficking as a key MSC-immune cell interaction mechanism with immunomodulatory therapeutic potential.

• Keywords
• B cell, immunoregulation, mesenchymal stem cell, metabolism, mitochondria,
• MeSH
• Lymphocyte Activation MeSH
• Antigens, CD19 metabolism   MeSH
• Apoptosis MeSH
• B-Lymphocytes * immunology   physiology   metabolism   MeSH
• Antigens, CD MeSH
• Antigens, Differentiation, T-Lymphocyte MeSH
• Coculture Techniques MeSH
• Lectins, C-Type MeSH
• Mesenchymal Stem Cells * physiology   MeSH
• Mitochondria * metabolism   physiology   MeSH
• Mitophagy MeSH
• Mice, Transgenic MeSH
• Mice MeSH
• Reactive Oxygen Species metabolism   MeSH
• Spleen cytology   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Antigens, CD19 MeSH
• Antigens, CD MeSH
• CD69 antigen MeSH Browser
• Antigens, Differentiation, T-Lymphocyte MeSH
• Lectins, C-Type MeSH
• Reactive Oxygen Species MeSH

Horizontal transfer of mitochondria from the tumour microenvironment to cancer cells to support proliferation and enhance tumour progression has been shown for various types of cancer in recent years. Glioblastoma, the most aggressive adult brain tumour, has proven to be no exception when it comes to dynamic intercellular mitochondrial movement, as shown in this study using an orthotopic tumour model of respiration-deficient glioblastoma cells. Although confirmed mitochondrial transfer was shown to facilitate tumour progression in glioblastoma, we decided to investigate whether the related electron transport chain recovery is necessary for tumour formation in the brain. Based on experiments using time-resolved analysis of tumour formation by glioblastoma cells depleted of their mitochondrial DNA, we conclude that functional mitochondrial respiration is essential for glioblastoma growth in vivo, because it is needed to support coenzyme Q redox cycling for de novo pyrimidine biosynthesis controlled by respiration-linked dihydroorotate dehydrogenase enzyme activity. We also demonstrate here that astrocytes are key mitochondrial donors in this model.

• MeSH
• Astrocytes metabolism   pathology   MeSH
• Cell Respiration MeSH
• Dihydroorotate Dehydrogenase MeSH
• Glioblastoma * pathology   metabolism   genetics   MeSH
• Humans MeSH
• DNA, Mitochondrial genetics   MeSH
• Mitochondria * metabolism   MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Brain Neoplasms * pathology   metabolism   genetics   MeSH
• Oxidoreductases Acting on CH-CH Group Donors metabolism   MeSH
• Cell Proliferation MeSH
• Electron Transport MeSH
• Ubiquinone metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Dihydroorotate Dehydrogenase MeSH
• DNA, Mitochondrial MeSH
• Oxidoreductases Acting on CH-CH Group Donors MeSH
• Ubiquinone MeSH

Intercellular mitochondria transfer is an evolutionarily conserved process in which one cell delivers some of their mitochondria to another cell in the absence of cell division. This process has diverse functions depending on the cell types involved and physiological or disease context. Although mitochondria transfer was first shown to provide metabolic support to acceptor cells, recent studies have revealed diverse functions of mitochondria transfer, including, but not limited to, the maintenance of mitochondria quality of the donor cell and the regulation of tissue homeostasis and remodelling. Many mitochondria-transfer mechanisms have been described using a variety of names, generating confusion about mitochondria transfer biology. Furthermore, several therapeutic approaches involving mitochondria-transfer biology have emerged, including mitochondria transplantation and cellular engineering using isolated mitochondria. In this Consensus Statement, we define relevant terminology and propose a nomenclature framework to describe mitochondria transfer and transplantation as a foundation for further development by the community as this dynamic field of research continues to evolve.

• MeSH
• Humans MeSH
• Mitochondria * transplantation   metabolism   physiology   MeSH
• Terminology as Topic * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Consensus Development Conference MeSH
• Review MeSH

Horizontal mitochondrial transfer (HMT) has emerged as a novel phenomenon in cell biology, but it is unclear how this process of intercellular movement of mitochondria is regulated. A new study in PLOS Biology reports that ADP released by stressed cells is a signal that triggers HMT.

• MeSH
• Adenosine Diphosphate * metabolism   MeSH
• Humans MeSH
• Mitochondria * metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Comment MeSH
• Names of Substances
• Adenosine Diphosphate * MeSH

BACKGROUND: Fast adaptation of glycolytic and mitochondrial energy pathways to changes in the tumour microenvironment is a hallmark of cancer. Purely glycolytic ρ0 tumour cells do not form primary tumours unless they acquire healthy mitochondria from their micro-environment. Here we explored the effects of severely compromised respiration on the metastatic capability of 4T1 mouse breast cancer cells. METHODS: 4T1 cell lines with different levels of respiratory capacity were generated; the Seahorse extracellular flux analyser was used to evaluate oxygen consumption rates, fluorescent confocal microscopy to assess the number of SYBR gold-stained mitochondrial DNA nucleoids, and the presence of the ATP5B protein in the cytoplasm and fluorescent in situ nuclear hybridization was used to establish ploidy. MinION nanopore RNA sequence analysis was used to compare mitochondrial DNA transcription between cell lines. Orthotopic injection was used to determine the ability of cells to metastasize to the lungs of female Balb/c mice. RESULTS: OXPHOS-deficient ATP5B-KO3.1 cells did not generate primary tumours. Severely OXPHOS compromised ρ0D5 cells generated both primary tumours and lung metastases. Cells generated from lung metastasis of both OXPHOS-competent and OXPHOS-compromised cells formed primary tumours but no metastases when re-injected into mice. OXPHOS-compromised cells significantly increased their mtDNA content, but this did not result in increased OXPHOS capacity, which was not due to decreased mtDNA transcription. Gene set enrichment analysis suggests that certain cells derived from lung metastases downregulate their epithelial-to-mesenchymal related pathways. CONCLUSION: In summary, OXPHOS is required for tumorigenesis in this orthotopic mouse breast cancer model but even very low levels of OXPHOS are sufficient to generate both primary tumours and lung metastases.

• Keywords
• breast cancer, glycolysis, intercellular mitochondrial transport, metastasis, orthotopic mouse model, oxidative phosphorylation,
• Publication type
• Journal Article MeSH

Mammalian genes were long thought to be constrained within somatic cells in most cell types. This concept was challenged recently when cellular organelles including mitochondria were shown to move between mammalian cells in culture via cytoplasmic bridges. Recent research in animals indicates transfer of mitochondria in cancer and during lung injury in vivo, with considerable functional consequences. Since these pioneering discoveries, many studies have confirmed horizontal mitochondrial transfer (HMT) in vivo, and its functional characteristics and consequences have been described. Additional support for this phenomenon has come from phylogenetic studies. Apparently, mitochondrial trafficking between cells occurs more frequently than previously thought and contributes to diverse processes including bioenergetic crosstalk and homeostasis, disease treatment and recovery, and development of resistance to cancer therapy. Here we highlight current knowledge of HMT between cells, focusing primarily on in vivo systems, and contend that this process is not only (patho)physiologically relevant, but also can be exploited for the design of novel therapeutic approaches.

• MeSH
• Energy Metabolism MeSH
• Phylogeny MeSH
• Mitochondria * metabolism   MeSH
• Neoplasms * genetics   metabolism   MeSH
• Mammals MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Comment MeSH
• Research Support, Non-U.S. Gov't MeSH

Rationale: Despite growing evidence for mitochondria's involvement in cancer, the roles of specific metabolic components outside the respiratory complex have been little explored. We conducted metabolomic studies on mitochondrial DNA (mtDNA)-deficient (ρ0) cancer cells with lower proliferation rates to clarify the undefined roles of mitochondria in cancer growth. Methods and results: Despite extensive metabolic downregulation, ρ0 cells exhibited high glycerol-3-phosphate (G3P) level, due to low activity of mitochondrial glycerol-3-phosphate dehydrogenase (GPD2). Knockout (KO) of GPD2 resulted in cell growth suppression as well as inhibition of tumor progression in vivo. Surprisingly, this was unrelated to the conventional bioenergetic function of GPD2. Instead, multi-omics results suggested major changes in ether lipid metabolism, for which GPD2 provides dihydroxyacetone phosphate (DHAP) in ether lipid biosynthesis. GPD2 KO cells exhibited significantly lower ether lipid level, and their slower growth was rescued by supplementation of a DHAP precursor or ether lipids. Mechanistically, ether lipid metabolism was associated with Akt pathway, and the downregulation of Akt/mTORC1 pathway due to GPD2 KO was rescued by DHAP supplementation. Conclusion: Overall, the GPD2-ether lipid-Akt axis is newly described for the control of cancer growth. DHAP supply, a non-bioenergetic process, may constitute an important role of mitochondria in cancer.

• Keywords
• DHAP, GPD2, cancer, ether lipids, mitochondria,
• MeSH
• Energy Metabolism MeSH
• Ethers metabolism   MeSH
• Glycerolphosphate Dehydrogenase * genetics   metabolism   MeSH
• Humans MeSH
• Mitochondria * enzymology   MeSH
• Mice MeSH
• Neoplasms * enzymology   pathology   MeSH
• Proto-Oncogene Proteins c-akt * metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Ethers MeSH
• Glycerolphosphate Dehydrogenase * MeSH
• Proto-Oncogene Proteins c-akt * MeSH

Targeting tumor metabolism for cancer therapy is an old strategy. In fact, historically the first effective cancer therapeutics were directed at nucleotide metabolism. The spectrum of metabolic drugs considered in cancer increases rapidly - clinical trials are in progress for agents directed at glycolysis, oxidative phosphorylation, glutaminolysis and several others. These pathways are essential for cancer cell proliferation and redox homeostasis, but are also required, to various degrees, in other cell types present in the tumor microenvironment, including immune cells, endothelial cells and fibroblasts. How metabolism-targeted treatments impact these tumor-associated cell types is not fully understood, even though their response may co-determine the overall effectivity of therapy. Indeed, the metabolic dependencies of stromal cells have been overlooked for a long time. Therefore, it is important that metabolic therapy is considered in the context of tumor microenvironment, as understanding the metabolic vulnerabilities of both cancer and stromal cells can guide new treatment concepts and help better understand treatment resistance. In this review we discuss recent findings covering the impact of metabolic interventions on cellular components of the tumor microenvironment and their implications for metabolic cancer therapy.

• Keywords
• cancer, endothelial cells, fatty acid metabolism, glycolysis, metabolism, nucleotide metabolism, oxidative phoshorylation, tumor micro environment (TME),
• Publication type
• Journal Article MeSH
• Review MeSH

Mitochondrial oxidative phosphorylation (OXPHOS) generates ATP, but OXPHOS also supports biosynthesis during proliferation. In contrast, the role of OXPHOS during quiescence, beyond ATP production, is not well understood. Using mouse models of inducible OXPHOS deficiency in all cell types or specifically in the vascular endothelium that negligibly relies on OXPHOS-derived ATP, we show that selectively during quiescence OXPHOS provides oxidative stress resistance by supporting macroautophagy/autophagy. Mechanistically, OXPHOS constitutively generates low levels of endogenous ROS that induce autophagy via attenuation of ATG4B activity, which provides protection from ROS insult. Physiologically, the OXPHOS-autophagy system (i) protects healthy tissue from toxicity of ROS-based anticancer therapy, and (ii) provides ROS resistance in the endothelium, ameliorating systemic LPS-induced inflammation as well as inflammatory bowel disease. Hence, cells acquired mitochondria during evolution to profit from oxidative metabolism, but also built in an autophagy-based ROS-induced protective mechanism to guard against oxidative stress associated with OXPHOS function during quiescence.Abbreviations: AMPK: AMP-activated protein kinase; AOX: alternative oxidase; Baf A: bafilomycin A1; CI, respiratory complexes I; DCF-DA: 2',7'-dichlordihydrofluorescein diacetate; DHE: dihydroethidium; DSS: dextran sodium sulfate; ΔΨmi: mitochondrial inner membrane potential; EdU: 5-ethynyl-2'-deoxyuridine; ETC: electron transport chain; FA: formaldehyde; HUVEC; human umbilical cord endothelial cells; IBD: inflammatory bowel disease; LC3B: microtubule associated protein 1 light chain 3 beta; LPS: lipopolysaccharide; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; mtDNA: mitochondrial DNA; NAC: N-acetyl cysteine; OXPHOS: oxidative phosphorylation; PCs: proliferating cells; PE: phosphatidylethanolamine; PEITC: phenethyl isothiocyanate; QCs: quiescent cells; ROS: reactive oxygen species; PLA2: phospholipase A2, WB: western blot.

• Keywords
• ATG4B, biosynthesis, cell death, electron transport chain, endothelial cells, mitochondria, oxidative phosphorylation, oxidative stress, reactive oxygen species,
• MeSH
• Adenosine Triphosphate metabolism   MeSH
• Autophagy * MeSH
• Cysteine metabolism   MeSH
• Dextrans metabolism   MeSH
• Respiration MeSH
• Endothelial Cells metabolism   MeSH
• Fibroblasts metabolism   MeSH
• Formaldehyde metabolism   MeSH
• Phosphatidylethanolamines metabolism   MeSH
• Inflammatory Bowel Diseases * metabolism   MeSH
• Isothiocyanates MeSH
• Humans MeSH
• Lipopolysaccharides metabolism   MeSH
• DNA, Mitochondrial metabolism   MeSH
• Mitochondria metabolism   MeSH
• Mechanistic Target of Rapamycin Complex 1 metabolism   MeSH
• Mice MeSH
• AMP-Activated Protein Kinases metabolism   MeSH
• Microtubule-Associated Proteins metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Sirolimus MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adenosine Triphosphate MeSH
• Cysteine MeSH
• Dextrans MeSH
• Formaldehyde MeSH
• Phosphatidylethanolamines MeSH
• Isothiocyanates MeSH
• Lipopolysaccharides MeSH
• DNA, Mitochondrial MeSH
• Mechanistic Target of Rapamycin Complex 1 MeSH
• phenethyl isothiocyanate MeSH Browser
• AMP-Activated Protein Kinases MeSH
• Microtubule-Associated Proteins MeSH
• Reactive Oxygen Species MeSH
• Sirolimus MeSH

Mitochondria are organelles essential for tumor cell proliferation and metastasis. Although their main cellular function, generation of energy in the form of ATP is dispensable for cancer cells, their capability to drive their adaptation to stress originating from tumor microenvironment makes them a plausible therapeutic target. Recent research has revealed that cancer cells with damaged oxidative phosphorylation import healthy (functional) mitochondria from surrounding stromal cells to drive pyrimidine synthesis and cell proliferation. Furthermore, it has been shown that energetically competent mitochondria are fundamental for tumor cell migration, invasion and metastasis. The spatial positioning and transport of mitochondria involves Miro proteins from a subfamily of small GTPases, localized in outer mitochondrial membrane. Miro proteins are involved in the structure of the MICOS complex, connecting outer and inner-mitochondrial membrane; in mitochondria-ER communication; Ca2+ metabolism; and in the recycling of damaged organelles via mitophagy. The most important role of Miro is regulation of mitochondrial movement and distribution within (and between) cells, acting as an adaptor linking organelles to cytoskeleton-associated motor proteins. In this review, we discuss the function of Miro proteins in various modes of intercellular mitochondrial transfer, emphasizing the structure and dynamics of tunneling nanotubes, the most common transfer modality. We summarize the evidence for and propose possible roles of Miro proteins in nanotube-mediated transfer as well as in cancer cell migration and metastasis, both processes being tightly connected to cytoskeleton-driven mitochondrial movement and positioning.

• Keywords
• Miro, cancer, intercellular transfer, metastasis, migration, mitochondria, respiration,
• Publication type
• Journal Article MeSH
• Review MeSH