Somatic mitochondrial DNA mutations in cancer escape purifying selection and high pathogenicity mutations lead to the oncocytic phenotype: pathogenicity analysis of reported somatic mtDNA mutations in tumors (original) (raw)
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Human Molecular Genetics, 2007
Mutations in mitochondrial DNA (mtDNA) are frequent in cancers but it is not yet clearly established whether they are modifier events involved in cancer progression or whether they are a consequence of tumorigenesis. Here we show a benign tumor type in which mtDNA mutations that lead to complex I (CI) enzyme deficiency are found in all tumors and are the only genetic alteration detected. Actually renal oncocytomas are homogeneous tumors characterized by dense accumulation of mitochondria and we had found that they are deficient in electron transport chain complex I (CI, NADH-ubiquinone oxidoreductase). In this work total sequencing of mtDNA showed that 9/9 tumors harbored point mutations in mtDNA, seven in CI genes, one in complex III, and one in the control region. 7/8 mutations were somatic. All tumors were somatically deficient for CI. The clonal amplification of mutated mtDNA in 8/9 tumors demonstrates that these alterations are selected and therefore favor or trigger growth. No nuclear DNA rearrangement was detected beside mtDNA defects. We hypothesize that functional deficiency of the oxidative phosphorylation CI could create a loop of amplification of mitochondria during cell division, impair substrates oxidation and increase intermediary metabolites availability.
An inherited mitochondrial DNA disruptive mutation shifts to homoplasmy in oncocytic tumor cells
Human Mutation, 2009
A disruptive frameshift mtDNA mutation affecting the ND5 subunit of complex I is present in homoplasmy in a nasopharyngeal oncocytic tumor and inherited as a heteroplasmic germline mutation recurring in two of the patient's siblings. Homoplasmic ND5 mutation in the tumor correlates with lack of the ND6 subunit, suggesting complex I disassembly. A few oncocytic areas, expressing ND6 and heteroplasmic for the ND5 mutation, harbor a de novo homoplasmic ND1 mutation. Since shift to homoplasmy of ND1 and ND5 mutations occurs exclusively in tumor cells, we conclude that complex I mutations may have a selective advantage and accompany oncocytic transformation. Hum Mutat 0, 1-6, 2008. r r
93 Loss of complex I due to mitochondrial DNA mutations in renal oncocytoma
Mitochondrion, 2007
Many solid tumors exhibit abnormal aerobic metabolism characterized by increased glycolytic capacity and decreased cellular respiration. Recently, mutations in the nuclear encoded mitochondrial enzymes fumarate hydratase and succinate dehydrogenase have been identified in certain tumor types, thus demonstrating a direct link between mitochondrial energy metabolism and tumorigenesis. Although mutations in the mitochondrial genome (mitochondrial DNA, mtDNA) also can affect aerobic metabolism and mtDNA alterations are frequently observed in tumor cells, evidence linking respiratory chain deficiency in a specific tumor type to a specific mtDNA mutation has been lacking. Experimental Design: To identify mitochondrial alterations in oncocytomas, we investigated the activities of respiratory chain enzymes and sequenced mtDNA in 15 renal oncocytoma tissues. Results: Here, we show that loss of respiratory chain complex I (NADH/ubiquinone oxidoreductase) is associated with renal oncocytoma. Enzymatic activity of complex I was undetectable or greatly reduced in the tumor samples (n = 15). Blue Native gel electrophoresis of the multisubunit enzyme complex revealed a lack of assembled complex I. Mutation analysis of the mtDNA showed frame-shift mutations in the genes of either subunit ND1, ND4, or ND5 of complex I in 9 of the 15 tumors. Conclusion: Our data indicate that isolated loss of complex I is a specific feature of renal oncocytoma and that this deficiency is frequently caused by somatic mtDNA mutations.
Mitochondrial DNA mutations in cancer - from bench to bedside
Mitochondria are cell organelles mostly known for their production of ATP through oxidative phosphorylation. As suggested over 70 years ago by O. Warburg and recently confirmed with molecular techniques, alterations in respiratory activity and mitochondrial DNA appear to be a common feature of malignant cells. Somatic mtDNA mutations have been reported in many types of cancer cells. MtDNA mutation pattern may enhance the specificity of cancer diagnostics, detection and prediction of tumor growth rate and patients’ outcome. Therefore it may be used as a molecular cancer bio-marker. Nevertheless recently published papers list a large number of mitochondrial DNA mutations in many different cancer types, but their role in cell patophysiology remains unsummarized. This review covers the consequences of mitochondrial genes mutations for human cell physiology and proliferation. We underline effects of mtDNA mutation-resulting amino acid changes in the respiratory chain proteins’ structure, and propose changes in mitochondrial protein function. Mutations are critically evaluated and interpreted in the functional context and clinical utility of molecular mitochondrial research is summarized and new perspectives for ‘mitochondrial oncology’ suggested. TABLE OF CONTENTS 1. Abstract 2. Introduction 2.1. MtDNA mutation mechanism 2.2. The role of reactive oxygen species in mitochondrial carcinogenesis 3. D-loop mutations in human cancers 3.1. Consequences for cell physiology 3.2. Clinical implications 4. tRNA genes mutations in human cancers 4.1 Consequences for cell physiology 4.2. Clinical implications 5. rRNA genes mutations 6. OXPHOS complex I genes and human cancer 6.1. Consequences for cell physiology 6.2. Clinical implications 7. OXPHOS complex III genes 7.1. Consequences for cell physiology 8. OXPHOS complex IV genes and human cancer 8.1. Consequences for cell physiology 8.2. Clinical implications 9. OXPHOS complex V genes and human cancers 9.1. Consequences for cell physiology 9.2. Clinical implications 10. Large mtDNA deletions and mtDNA depletion in human cancers 11. OXPHOS genes expression in human cancers 12. Summary and perspectives 13. Acknowledgements 14. References
Mitochondrial DNA Variations in Tumors: Drivers or Passengers?
Mitochondrial DNA - New Insights, 2018
Mitochondrial DNA alterations, including point mutations, deletions, inversions and copy number variations, have been widely reported in many age-related degenerative diseases and tumors. However, numerous studies investigating their pathogenic role in cancer have provided inconsistent evidence. Furthermore, biological impacts of mitochondrial DNA variants vary tremendously, depending on the proportion of mutant DNA molecules carried by the neoplastic cells (the so-called heteroplasmy). The recent discovery of inter-genomic crosstalk between nucleus and mitochondria has reinforced the role of mitochondrial DNA variants in perturbing this essential signaling pathway and thus indirectly targeting nuclear genes involved in tumorigenic and invasive phenotype. Therefore, mitochondrial dysfunction is currently considered a crucial hallmark of carcinogenesis as well as a promising target for anticancer therapy. This chapter describes the role of different types of mitochondrial DNA alterations by mainly considering the paradigmatic model of colorectal carcinogenesis and, in particular, it revisits the issue of whether mitochondrial mutations are causative cancer drivers or simply genuine passenger events. The advent of high-throughput next-generation sequencing techniques, as well as the development of genetic and pharmaceutical interventions for the treatment of mitochondrial dysfunction in cancer, are also discussed.
Mitochondrial DNA mutations in human cancer
Oncogene, 2006
Somatic mitochondrial DNA (mtDNA) mutations have been increasingly observed in primary human cancers. As each cell contains many mitochondria with multiple copies of mtDNA, it is possible that wild-type and mutant mtDNA can co-exist in a state called heteroplasmy. During cell division, mitochondria are randomly distributed to daughter cells. Over time, the proportion of the mutant mtDNA within the cell can vary and may drift toward predominantly mutant or wild type to achieve homoplasmy. Thus, the biological impact of a given mutation may vary, depending on the proportion of mutant mtDNAs carried by the cell. This effect contributes to the various phenotypes observed among family members carrying the same pathogenic mtDNA mutation. Most mutations occur in the coding sequences but few result in substantial amino acid changes raising questions as to their biological consequence. Studies reveal that mtDNA play a crucial role in the development of cancer but further work is required to establish the functional significance of specific mitochondrial mutations in cancer and disease progression. The origin of somatic mtDNA mutations in human cancer and their potential diagnostic and therapeutic implications in cancer are discussed. This review article provides a detailed summary of mtDNA mutations that have been reported in various types of cancer. Furthermore, this review offers some perspective as to the origin of these of mutations, their functional consequences in cancer development, and possible therapeutic implications.
Role of Mitochondrial Mutations in Cancer
Endocrine Pathology, 2006
A role for mitochondria in cancer causation has been implicated through identification of mutations in the mitochondrial DNA (mtDNA) and in nuclear-encoded mitochondrial genes. Although many mtDNA mutations were detected in common tumors, an unequivocal causal link between heritable mitochondrial abnormalities and cancer is provided only by the germ line mutations in the nuclear-encoded genes for succinate dehydrogenase (mitochondrial complex II) and fumarate hydratase (fumarase). The absence of evidence for highly penetrant tumors caused by inherited mtDNA mutations contrasts with the frequent occurrence of mtDNA mutations in many different tumor types. Thus, either the majority of diverse mtDNA mutations observed in tumors are not important for the process of carcinogenesis or that they play a common oncogenic role.
Cancer Research, 2006
Oncocytic tumors are characterized by cells with an aberrant accumulation of mitochondria. To assess mitochondrial function in neoplastic oncocytic cells, we studied the thyroid oncocytic cell line XTC.UC1 and compared it with other thyroid non-oncocytic cell lines. Only XTC.UC1 cells were unable to survive in galactose, a condition forcing cells to rely solely on mitochondria for energy production. The rate of respiration and mitochondrial ATP synthesis driven by complex I substrates was severely reduced in XTC.UC1 cells. Furthermore, the enzymatic activity of complexes I and III was dramatically decreased in these cells compared with controls, in conjunction with a strongly enhanced production of reactive oxygen species. Osteosarcoma-derived transmitochondrial cell hybrids (cybrids) carrying XTC.UC1 mitochondrial DNA (mtDNA) were generated to discriminate whether the energetic failure depended on mitochondrial or nuclear DNA mutations. In galactose medium, XTC.UC1 cybrid clones showed reduced viability and ATP content, similarly to the parental XTC.UC1, clearly pointing to the existence of mtDNA alterations. Sequencing of XTC.UC1 mtDNA identified a frameshift mutation in ND1 and a nonconservative substitution in cytochrome b, two mutations with a clear pathogenic potential. In conclusion, this is the first demonstration that mitochondrial dysfunction of XTC.UC1 is due to a combined complex I/III defect associated with mtDNA mutations, as proven by the transfer of the defective energetic phenotype with the mitochondrial genome into the cybrids. (Cancer Res 2006; 66(12): 6087-96)
Mitochondrial defects in cancer
Molecular cancer, 2002
Mitochondria play important roles in cellular energy metabolism, free radical generation, and apoptosis. Defects in mitochondrial function have long been suspected to contribute to the development and progression of cancer. In this review article, we aim to provide a brief summary of our current understanding of mitochondrial genetics and biology, review the mtDNA alterations reported in various types of cancer, and offer some perspective as to the emergence of mtDNA mutations, their functional consequences in cancer development, and therapeutic implications.