Mitochondrial neurogastrointestinal encephalomyopathy caused by thymidine phosphorylase enzyme deficiency: From pathogenesis to emerging therapeutic options

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a progressive metabolic disorder caused by thymidine phosphorylase (TP) enzyme deficiency. The lack of TP results in systemic accumulation of deoxyribonucleosides thymidine (dThd) and deoxyuridine (dUrd). In these patients, clinical features include mental regression, ophthalmoplegia, and fatal gastrointestinal complications. The accumulation of nucleosides also causes imbalances in mitochondrial DNA (mtDNA) deoxyribonucleoside triphosphates (dNTPs), which may play a direct or indirect role in the mtDNA depletion/deletion abnormalities, although the exact underlying mechanism remains unknown. The available therapeutic approaches include dialysis and enzyme replacement therapy, both can only transiently reverse the biochemical imbalance. Allogeneic hematopoietic stem cell transplantation is shown to be able to restore normal enzyme activity and improve clinical manifestations in MNGIE patients. However, transplant related complications and disease progression result in a high mortality rate. New therapeutic approaches, such as adeno-associated viral vector and hematopoietic stem cell gene therapy have been tested in Tymp−/− Upp1−/− mice, a murine model for MNGIE. This review provides background information on disease manifestations of MNGIE with a focus on current management and treatment options. It also outlines the pre-clinical approaches toward future treatment of the disease

How do changes in the mtDNA and mitochondrial dysfunction influence cancer and cancer therapy? Challenges, opportunities and models

Several mutations in nuclear genes encoding for mitochondrial components have been associated with an increased cancer risk or are even causative, e.g. succinate dehydrogenase (SDHB, SDHC and SDHD genes) and iso-citrate dehydrogenase (IDH1 and IDH2 genes). Recently, studies have suggested an eminent role for mitochondrial DNA (mtDNA) mutations in the development of a wide variety of cancers. Various studies associated mtDNA abnormalities, including mutations, deletions, inversions and copy number alterations, with mitochondrial dysfunction. This might, explain the hampered cellular bioenergetics in many cancer cell types. Germline (e.g. m.10398A>G; m.6253T>C) and somatic mtDNA mutations as well as differences in mtDNA copy number seem to be associated with cancer risk. It seems that mtDNA can contribute as driver or as complementary gene mutation according to the multiple-hit model. This can enhance the mutagenic/clonogenic potential of the cell as observed for m.8993T>G or influences the metastatic potential in later stages of cancer progression. Alternatively, other mtDNA variations will be innocent passenger mutations in a tumor and therefore do not contribute to the tumorigenic or metastatic potential. In this review, we discuss how reported mtDNA variations interfere with cancer treatment and what implications this has on current successful pharmaceutical interventions. Mutations in MT-ND4 and mtDNA depletion have been reported to be involved in cisplatin resistance. Pharmaceutical impairment of OXPHOS by metformin can increase the efficiency of radiotherapy. To study mitochondrial dysfunction in cancer, different cellular models (like ρ0 cells or cybrids), in vivo murine models (xenografts and specific mtDNA mouse models in combination with a spontaneous cancer mouse model) and small animal models (e.g. Danio rerio) could be potentially interesting to use. For future research, we foresee that unraveling mtDNA variations can contribute to personalized therapy for specific cancer types and improve the outcome of the disease

Healthy, mtDNA-mutation free mesoangioblasts from mtDNA patients qualify for autologous therapy

BACKGROUND: Myopathy and exercise intolerance are prominent clinical features in carriers of a point-mutation or large-scale deletion in the mitochondrial DNA (mtDNA). In the majority of patients, the mtDNA mutation is heteroplasmic with varying mutation loads between tissues of an individual. Exercise-induced muscle regeneration has been shown to be beneficial in some mtDNA mutation carriers, but is often not feasible for this patient group. In this study, we performed in vitro analysis of mesoangioblasts from mtDNA mutation carriers to assess their potential to be used as source for autologous myogenic cell therapy. METHODS: We assessed the heteroplasmy level of patient-derived mesoangioblasts, isolated from skeletal muscle of multiple carriers of different mtDNA point-mutations (n = 25). Mesoangioblast cultures with < 10% mtDNA mutation were further analyzed with respect to immunophenotype, proliferation capacity, in vitro myogenic differentiation potential, mitochondrial function, and mtDNA quantity. RESULTS: This study demonstrated that mesoangioblasts in half of the patients contained no or a very low mutation load (< 10%), despite a much higher mutation load in their skeletal muscle. Moreover, none of the large-scale mtDNA deletion carriers displayed the deletion in mesoangioblasts, despite high percentages in skeletal muscle. The mesoangioblasts with no or a very low mutation load (< 10%) displayed normal mitochondrial function, proliferative capacity, and myogenic differentiation capacity. CONCLUSIONS: Our data demonstrates that in half of the mtDNA mutation carriers, their mesoangioblasts are (nearly) mutation free and can potentially be used as source for autologous cell therapy for generation of new muscle fibers without mtDNA mutation and normal mitochondrial function

Nitroglycerin as a radiosensitizer in non-small cell lung cancer: Results of a prospective imaging-based phase II trial

Background: Nitroglycerin is proposed as an agent to reduce tumour hypoxia by improving tumour perfusion. We investigated the potent

An essential difference in the reactivity of the glutathione adducts of the structurally closely related flavonoids monoher and quercetin

During the scavenging of free radicals flavonoids are oxidized to electrophilic quinones. Glutathione (GSH) can trap these quinones, thereby forming GSH-flavonoid adducts. The aim of this study was to compare the stability of the GSH-flavonoid adduct of 7-mono-O-(beta-hydroxyethyl)rutoside (monoHER) with that of quercetin. It was found that GSH-quercetin reacts with the thiol N-acetyl-l-cysteine (NAC) to form NAC-quercetin, whereas GSH-monoHER does not react with NAC. In addition, the adduct of the monoHER quinone with the dithiol dithiothreitol (DTT) is relatively stable, whereas the DTT-quercetin adduct is readily converted into quercetin and DTT disulfide. These differences in reactivity of the thiol-flavonoid adducts demonstrate that GSH-monoHER is much more stable than GSH-quercetin. This difference in reactivity was corroborated by molecular quantum chemical calculations. Thus, although both flavonoid quinones are rapidly scavenged by GSH, the advantage of monoHER is that it forms a stable conjugate with GSH, thereby preventing a possible spread of toxicity. These findings demonstrate that even structurally comparable flavonoids behave differently, which will be reflected in the biological effects of these flavonoids

Targeting glucose and glutamine metabolism combined with radiation therapy in non-small cell lung cancer

Item does not contain fulltextPURPOSE: Metabolic inhibition might sensitize tumors to irradiation. Here, we examined the effect of lonidamine (several metabolic effects, inhibiting hexokinase amongst others) and/or 968 (glutaminase inhibitor) on tumor cell metabolism, cell growth, cytotoxicity and radiosensitivity in NSCLC cell lines in vitro in relation to histology. MATERIALS AND METHODS: Adeno- (H23, HCC827, H1975) and squamous cell carcinoma (H520, H292, SW900) NSCLC cells were treated with lonidamine and/or 968 for 72 h under physiological levels of glucose (1.5 mM). Cells were irradiated with 0, 4 or 8 Gy. Cell growth of H2B-mCherry transduced cells and cytotoxicity (CellTox Green Cytotoxicity Assay) were measured using live cell imaging (IncuCyte). Inhibitory effects on metabolic profiles was determined using the Seahorse XF96 extracellular Flux analyzer. RESULTS: NSCLC cell lines responded differently to glycolysis (lonidamine) and/or glutaminase (968) inhibition, largely corresponding with changes in glycolytic and mitochondrial metabolism upon treatment. Response patterns were not related to histology. 968 was cytotoxic in cell lines with high glutaminase C expression (H1975 and H520), whereas combination treatment was cytotoxic in KRAS mutated cell lines SW900 and H23. H292 and HCC827 were resistant to combination treatment. Treatment with 968 and especially lonidamine resulted in radiosensitization of H292 and HCC827 in terms of decreased relative cell growth and increased cytotoxicity. CONCLUSION: NSCLC is a heterogeneous disease, which is reflected in the response of different cell lines to the treatment (combinations) reported here. Only a part of NSCLC patients may benefit from the combination of radiation therapy and metabolic inhibition, making stratification necessary

Data from: Nitroglycerin in non-small cell lung cancer: does it impact tumor hypoxia and tumor perfusion? A window-of-opportunity clinical trial.

Despite preclinical evidence that nitric oxide (NO) donors influence both tumor perfusion and hypoxia, in clinical trials nitroglycerin has not been shown to improve the treatment results of all patients with non-small cell lung cancer (NSCLC). Biomarkers are therefore needed to select patients for treatment with NO donors. In this window-of-opportunity study we demonstrate the effect of nitroglycerin on hypoxia in patients using repeated hypoxia PET-imaging: we observed a reduction of hypoxia - quantified by uptake of PET tracer HX4- of varying magnitude upon application of a nitroglycerin..

ATG12 deficiency results in intracellular glutamine depletion, abrogation of tumor hypoxia and a favorable prognosis in cancer

Hypoxia is a common feature of solid tumors and is associated with increased tumor progression, resistance to therapy and increased metastasis. Hence, tumor hypoxia is a prognostic factor independent of treatment modality. To survive hypoxia, cells activate macroautophagy/autophagy. Paradoxically, in several cancer types, mutations or loss of essential autophagy genes have been reported that are associated with earlier onset of tumor growth. However, to our knowledge, the phenotypic and therapeutic consequences of autophagy deficiency have remained unexplored. In this study, we determined autophagy-defects in head and neck squamous cell carcinoma (HNSCC) and observed that expression of ATG12 (autophagy related 12) was lost in 25%-40% of HNSCC. In line, ATG12 loss is associated with absence of hypoxia, as determined by pimonidazole immunohistochemistry. Hence, ATG12 loss is associated with improved prognosis after therapy in two independent HNSCC cohorts and 7 additional cancer types. In vivo, ATG12 targeting resulted in decreased hypoxia tolerance, increased necrosis and sensitivity of the tumor to therapy, but in vitro ATG12-deficient cells displayed enhanced survival in nutrient-rich culture medium. Besides oxygen, delivery of glucose was hampered in hypoxic regions in vivo, which increases the reliance of cells on other carbon sources (e.g., L-glutamine). We observed decreased intracellular L-glutamine levels in ATG12-deficient cells during hypoxia and increased cell killing after L-glutamine depletion, indicating a central role for ATG12 in maintaining L-glutamine homeostasis. Our results demonstrate that ATG12(low) tumors represent a phenotypically different subtype that, due to the lowered hypoxia tolerance, display a favorable outcome after therapy