The adaptor protein Miro1 modulates horizontal transfer of mitochondria in mouse melanoma models.

Recent research has shown that mtDNA-deficient cancer cells (ρ cells) acquire mitochondria from tumor stromal cells to restore respiration, facilitating tumor formation. We investigated the role of Miro1, an adaptor protein involved in movement of mitochondria along microtubules, in this phenomenon. Inducible Miro1 knockout (Miro1) mice markedly delayed tumor formation after grafting ρ cancer cells.

Mitochondrial DNA damage, repair, and replacement in cancer.

Mitochondria are vital organelles with their own DNA (mtDNA). mtDNA is circular and composed of heavy and light chains that are structurally more accessible than nuclear DNA (nDNA). While nDNA is typically diploid, the number of mtDNA copies per cell is higher and varies considerably during development and between tissues.

Mitochondria on the move: Horizontal mitochondrial transfer in disease and health.

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.

Bioenergetic and Metabolic Adaptation in Tumor Progression and Metastasis.

The ability of cancer cells to adjust their metabolism in response to environmental changes is a well-recognized hallmark of cancer. Diverse cancer and non-cancer cells within tumors compete for metabolic resources. Metabolic demands change frequently during tumor initiation, progression and metastasis, challenging our quest to better understand tumor biology and develop novel therapeutics.

SMAD4 loss limits the vulnerability of pancreatic cancer cells to complex I inhibition via promotion of mitophagy.

Pancreatic cancer is one of the deadliest forms of cancer, which is attributed to lack of effective treatment options and drug resistance. Mitochondrial inhibitors have emerged as a promising class of anticancer drugs, and several inhibitors of the electron transport chain (ETC) are being clinically evaluated. We hypothesized that resistance to ETC inhibitors from the biguanide class could be induced by inactivation of SMAD4, an important tumor suppressor involved in transforming growth factor β (TGFβ) signaling, and associated with altered mitochondrial activity.

Mitochondrial DNA Affects the Expression of Nuclear Genes Involved in Immune and Stress Responses in a Breast Cancer Model.

Tumor cells without mitochondrial (mt) DNA (ρ cells) are auxotrophic for uridine, and their growth is supported by pyruvate. While ATP synthesis in ρ cells relies on glycolysis, they fail to form tumors unless they acquire mitochondria from stromal cells. Mitochondrial acquisition restores respiration that is essential for pyrimidine biosynthesis and for mitochondrial ATP production.

A simple indirect colorimetric assay for measuring mitochondrial energy metabolism based on uncoupling sensitivity.

Purpose: Cancer cells rapidly adjust their balance between glycolytic and mitochondrial ATP production in response to changes in their microenvironment and to treatments like radiation and chemotherapy. Reliable, simple, high throughput assays that measure the levels of mitochondrial energy metabolism in cells are useful determinants of treatment effects. Mitochondrial metabolism is routinely determined by measuring the rate of oxygen consumption (OCR).

Vaccines adjuvanted with an NKT cell agonist induce effective T-cell responses in models of CNS lymphoma.

The efficacy of anti-lymphoma vaccines that exploit the cellular adjuvant properties of activated natural killer T (NKT) cells were examined in mouse models of CNS lymphoma. Vaccines were prepared by either loading the NKT cell agonist, α-galactosylceramide onto irradiated and heat-shocked B- and T-lymphoma cells, or chemically conjugating α-galactosylceramide to MHC-binding peptides from a lymphoma-associated antigen. Vaccine efficacy was analyzed in mice bearing intracranial tumors.

High-intensity interval exercise increases humanin, a mitochondrial encoded peptide, in the plasma and muscle of men.

Humanin is a small regulatory peptide encoded within the 16S ribosomal RNA gene () of the mitochondrial genome that has cellular cyto- and metabolo-protective properties similar to that of aerobic exercise training. Here we investigated whether acute high-intensity interval exercise or short-term high-intensity interval training (HIIT) impacted skeletal muscle and plasma humanin levels. Vastus lateralis muscle biopsies and plasma samples were collected from young healthy untrained men ( = 10, 24.

Sodium sulfide selectively induces oxidative stress, DNA damage, and mitochondrial dysfunction and radiosensitizes glioblastoma (GBM) cells.

Glioblastoma (GBM) has a poor prognosis despite intensive treatment with surgery and chemoradiotherapy. Previous studies using dose-escalated radiotherapy have demonstrated improved survival; however, increased rates of radionecrosis have limited its use. Development of radiosensitizers could improve patient outcome.

Reactivation of Dihydroorotate Dehydrogenase-Driven Pyrimidine Biosynthesis Restores Tumor Growth of Respiration-Deficient Cancer Cells.

Cancer cells without mitochondrial DNA (mtDNA) do not form tumors unless they reconstitute oxidative phosphorylation (OXPHOS) by mitochondria acquired from host stroma. To understand why functional respiration is crucial for tumorigenesis, we used time-resolved analysis of tumor formation by mtDNA-depleted cells and genetic manipulations of OXPHOS. We show that pyrimidine biosynthesis dependent on respiration-linked dihydroorotate dehydrogenase (DHODH) is required to overcome cell-cycle arrest, while mitochondrial ATP generation is dispensable for tumorigenesis.

Metabolic reprogramming of mitochondrial respiration in metastatic cancer.

Tumor initiation, progression, and metastasis are tissue context-dependent processes. Cellular and non-cellular factors provide the selective microenvironment that determines the fate of the evolving tumor through mechanisms that include metabolic reprogramming. Genetic and epigenetic changes contribute to this reprogramming process, which is orchestrated through ongoing communication between the mitochondrial and nuclear genomes.

Mitochondrial Genome Transfer to Tumor Cells Breaks The Rules and Establishes a New Precedent in Cancer Biology.

Horizontal gene transfer is known to occur in bacteria and archaea whereas higher organisms including mammals undergo vertical transfer. Our recent results demonstrate horizontal transfer of mitochondrial DNA (mtDNA) from normal host cells to tumor cells lacking mitochondrial DNA (mtDNA). This mtDNA migration results in recovery of respiration, restored tumor initiation, and metastasis.

Intercellular Communication in Tumor Biology: A Role for Mitochondrial Transfer.

Intercellular communication between cancer cells and other cells in the tumor microenvironment plays a defining role in tumor development. Tumors contain infiltrates of stromal cells and immune cells that can either promote or inhibit tumor growth, depending on the cytokine/chemokine milieu of the tumor microenvironment and their effect on cell activation status. Recent research has shown that stromal cells can also affect tumor growth through the donation of mitochondria to respiration-deficient tumor cells, restoring normal respiration.

Alternative assembly of respiratory complex II connects energy stress to metabolic checkpoints.

Cell growth and survival depend on a delicate balance between energy production and synthesis of metabolites. Here, we provide evidence that an alternative mitochondrial complex II (CII) assembly, designated as CII, serves as a checkpoint for metabolite biosynthesis under bioenergetic stress, with cells suppressing their energy utilization by modulating DNA synthesis and cell cycle progression. Depletion of CII leads to an imbalance in energy utilization and metabolite synthesis, as evidenced by recovery of the de novo pyrimidine pathway and unlocking cell cycle arrest from the S-phase.

Functional Mitochondria in Health and Disease.

The ability to rapidly adapt cellular bioenergetic capabilities to meet rapidly changing environmental conditions is mandatory for normal cellular function and for cancer progression. Any loss of this adaptive response has the potential to compromise cellular function and render the cell more susceptible to external stressors such as oxidative stress, radiation, chemotherapeutic drugs, and hypoxia. Mitochondria play a vital role in bioenergetic and biosynthetic pathways and can rapidly adjust to meet the metabolic needs of the cell.

The mobility of mitochondria: Intercellular trafficking in health and disease.

The view that genes are constrained within somatic cells is challenged by in vitro evidence, and more recently by in vivo studies which demonstrate that mitochondria with their mitochondrial DNA (mtDNA) payload not only can, but do move between cells in tumour models and in mouse models of tissue damage. Using mouse tumour cell models without mtDNA to reflect mtDNA damage, we have shown that these cells grow tumours only after acquiring mtDNA from cells in the local microenvironment resulting in respiration recovery, tumorigenesis and metastasis. Mitochondrial transfer between cells has also been demonstrated following ischaemia-induced injury in the heart and brain and in lung epithelium, and following lung inflammation.

Horizontal transfer of whole mitochondria restores tumorigenic potential in mitochondrial DNA-deficient cancer cells.

Recently, we showed that generation of tumours in syngeneic mice by cells devoid of mitochondrial (mt) DNA (ρ cells) is linked to the acquisition of the host mtDNA. However, the mechanism of mtDNA movement between cells remains unresolved. To determine whether the transfer of mtDNA involves whole mitochondria, we injected B16ρ mouse melanoma cells into syngeneic C57BL/6N mice that express red fluorescent protein in their mitochondria.

Mitochondrial Transfer from Astrocytes to Neurons following Ischemic Insult: Guilt by Association?

Intercellular mitochondrial transfer has been shown in tumor models, following lung injury and in xenotransplants of leukemic cells, but trafficking between cells in the brain remains unexplored. A suggestion that mitochondria move from astrocytes to neurons in a model of ischemia in a recent article in Nature by Hayakawa et al. (2016) should be interpreted with caution.

Iterative sorting reveals CD133+ and CD133- melanoma cells as phenotypically distinct populations.

Background: The heterogeneity and tumourigenicity of metastatic melanoma is attributed to a cancer stem cell model, with CD133 considered to be a cancer stem cell marker in melanoma as well as other tumours, but its role has remained controversial.

Methods: We iteratively sorted CD133+ and CD133- cells from 3 metastatic melanoma cell lines, and observed tumourigenicity and phenotypic characteristics over 7 generations of serial xeno-transplantation in NOD/SCID mice.

Results: We demonstrate that iterative sorting is required to make highly pure populations of CD133+ and CD133- cells from metastatic melanoma, and that these two populations have distinct characteristics not related to the cancer stem cell phenotype.

Horizontal transfer of mitochondria between mammalian cells: beyond co-culture approaches.

Current dogma holds that genes are the property of individual mammalian cells and partition between daughter cells during cell division. However, and rather unexpectedly, recent research has demonstrated horizontal cell-to-cell transfer of mitochondria and mitochondrial DNA in several mammalian cell culture systems. Furthermore, unequivocal evidence that mitochondrial DNA transfer occurs in vivo has now been published.

N,N-Bis(glycityl)amines as anti-cancer drugs.

A series of N,N-bis(glycityl)amines with promising anti-cancer activity were prepared via the reductive amination of pentoses and hexoses, and subsequently screened for their ability to selectively inhibit the growth of cancerous versus non-cancerous cells. For the first time, we show that this class of compounds possesses anti-proliferative activity, and, while the selective killing of brain cancer (LN18) cells versus matched (SVG-P12) cells was modest, several of the amines, including d-arabinitylamine 1a and d-fucitylamine 1g, exhibited low micromolar IC50 values for HL60 cells. Moreover, these two amines showed good selectivity towards HL60 cells when compared to non-cancerous HEK-293 cells.

Mitochondrial DNA in Tumor Initiation, Progression, and Metastasis: Role of Horizontal mtDNA Transfer.

Mitochondrial DNA (mtDNA), encoding 13 out of more than 1,000 proteins of the mitochondrial proteome, is of paramount importance for the bioenergetic machinery of oxidative phosphorylation that is required for tumor initiation, propagation, and metastasis. In stark contrast to the widely held view that mitochondria and mtDNA are retained and propagated within somatic cells of higher organisms, recent in vitro and in vivo evidence demonstrates that mitochondria move between mammalian cells. This is particularly evident in cancer where defective mitochondrial respiration can be restored and tumor-forming ability regained by mitochondrial acquisition.

Mitochondrial genome acquisition restores respiratory function and tumorigenic potential of cancer cells without mitochondrial DNA.

We report that tumor cells without mitochondrial DNA (mtDNA) show delayed tumor growth, and that tumor formation is associated with acquisition of mtDNA from host cells. This leads to partial recovery of mitochondrial function in cells derived from primary tumors grown from cells without mtDNA and a shorter lag in tumor growth. Cell lines from circulating tumor cells showed further recovery of mitochondrial respiration and an intermediate lag to tumor growth, while cells from lung metastases exhibited full restoration of respiratory function and no lag in tumor growth.