Mitochondrial mutations in early stage prostate cancer and bodily fluids

Roles of MT-ND1 in Cancer

The energy shift toward glycolysis is one of the hallmarks of cancer. Complex I is a vital enzyme complex necessary for oxidative phosphorylation. The mitochondrially encoded NADH: ubiquinone oxidoreductase core subunit 1 (MT-ND1) is the largest subunit coded by mitochondria of complex I. The present study summarizes the structure and biological function of MT-ND1. From databases and literature, the expressions and mutations of MT-ND1 in a variety of cancers have been reviewed. MT-ND1 may be a biomarker for cancer diagnosis and prognosis. It is also a potential target for cancer therapy.

Mitochondrial DNA Changes in Respiratory Complex I Genes in Brain Gliomas

Mitochondria are organelles necessary for oxidative phosphorylation. The interest in the role of mitochondria in the process of carcinogenesis results from the fact that a respiratory deficit is found in dividing cells, especially in cells with accelerated proliferation. The study included tumor and blood material from 30 patients diagnosed with glioma grade II, III and IV according to WHO (World Health Organization). DNA was isolated from the collected material and next-generation sequencing was performed on the MiSeqFGx apparatus (Illumina). The study searched for a possible relationship between the occurrence of specific mitochondrial DNA polymorphisms in the respiratory complex I genes and brain gliomas of grade II, III and IV. The impact of missense changes on the biochemical properties, structure and functioning of the encoded protein, as well as their potential harmfulness, were assessed in silico along with their belonging to a given mitochondrial subgroup. The A3505G, C3992T, A4024G, T4216C, G5046A, G7444A, T11253C, G12406A and G13604C polymorphisms were assessed as deleterious changes in silico, indicating their association with carcinogenesis.

Mitochondrial Alterations in Prostate Cancer: Roles in Pathobiology and Racial Disparities

Prostate cancer (PCa) affects millions of men worldwide and is a major cause of cancer-related mortality. Race-associated PCa health disparities are also common and are of both social and clinical concern. Most PCa is diagnosed early due to PSA-based screening, but it fails to discern between indolent and aggressive PCa. Androgen or androgen receptor-targeted therapies are standard care of treatment for locally advanced and metastatic disease, but therapy resistance is common. Mitochondria, the powerhouse of cells, are unique subcellular organelles that have their own genome. A large majority of mitochondrial proteins are, however, nuclear-encoded and imported after cytoplasmic translation. Mitochondrial alterations are common in cancer, including PCa, leading to their altered functions. Aberrant mitochondrial function affects nuclear gene expression in retrograde signaling and promotes tumor-supportive stromal remodeling. In this article, we discuss mitochondrial alterations that have been reported in PCa and review the literature related to their roles in PCa pathobiology, therapy resistance, and racial disparities. We also discuss the translational potential of mitochondrial alterations as prognostic biomarkers and as effective targets for PCa therapy.

A hitchhiker's guide to cell-free DNA biology

Liquid biopsy provides a noninvasive window to the cancer genome and physiology. In particular, cell-free DNA (cfDNA) is a versatile analyte for guiding treatment, monitoring treatment response and resistance, tracking minimal residual disease, and detecting cancer earlier. Despite certain successes, brain cancer diagnosis is amongst those applications that has so far resisted clinical implementation. Recent approaches have highlighted the clinical gain achievable by exploiting cfDNA biological signatures to boost liquid biopsy or unlock new applications. However, the biology of cfDNA is complex, still partially understood, and affected by a range of intrinsic and extrinsic factors. This guide will provide the keys to read, decode, and harness cfDNA biology: the diverse sources of cfDNA in the bloodstream, the mechanism of cfDNA release from cells, the cfDNA structure, topology, and why accounting for cfDNA biology matters for clinical applications of liquid biopsy.

Mitochondrial Proteins as Source of Cancer Neoantigens

In the past decade, anti-tumour immune responses have been successfully exploited to improve the outcome of patients with different cancers. Significant progress has been made in taking advantage of different types of T cell functions for therapeutic purposes. Despite these achievements, only a subset of patients respond favorably to immunotherapy. Therefore, there is a need of novel approaches to improve the effector functions of immune cells and to recognize the major targets of anti-tumour immunity. A major hallmark of cancer is metabolic rewiring associated with switch of mitochondrial functions. These changes are a consequence of high energy demand and increased macromolecular synthesis in cancer cells. Such adaptations in tumour cells might generate novel targets of tumour therapy, including the generation of neoantigens. Here, we review the most recent advances in research on the immune response to mitochondrial proteins in different cellular conditions.

Role of Cell-Free DNA and Deoxyribonucleases in Tumor Progression

Many studies have reported an increase in the level of circulating cell-free DNA (cfDNA) in the blood of patients with cancer. cfDNA mainly comes from tumor cells and, therefore, carries features of its genomic profile. Moreover, tumor-derived cfDNA can act like oncoviruses, entering the cells of vulnerable organs, transforming them and forming metastatic nodes. Another source of cfDNA is immune cells, including neutrophils that generate neutrophil extracellular traps (NETs). Despite the potential eliminative effect of NETs on tumors, in some cases, their excessive generation provokes tumor growth as well as invasion. Considering both possible pathological contributions of cfDNA, as an agent of oncotransformation and the main component of NETs, the study of deoxyribonucleases (DNases) as anticancer and antimetastatic agents is important and promising. This review considers the pathological role of cfDNA in cancer development and the role of DNases as agents to prevent and/or prohibit tumor progression and the development of metastases.

Heterologous Inferential Analysis (HIA) and Other Emerging Concepts: In Understanding Mitochondrial Variation In Pathogenesis: There is no More Low-Hanging Fruit

Here we summarize our latest efforts to elucidate the role of mtDNA variants affecting the mitochondrial translation machinery, namely variants mapping to the mt-rRNA and mt-tRNA genes. Evidence is accumulating to suggest that the cellular response to interference with mitochondrial translation is different from that occurring as a result of mutations in genes encoding OXPHOS proteins. As a result, it appears safe to state that a complete view of mitochondrial disease will not be obtained until we understand the effect of mt-rRNA and mt-tRNA variants on mitochondrial protein synthesis. Despite the identification of a large number of potentially pathogenic variants in the mitochondrially encoded rRNA (mt-rRNA) genes, we lack direct methods to firmly establish their pathogenicity. In the absence of such methods, we have devised an indirect approach named heterologous inferential analysis (HIA ) that can be used to make predictions concerning the disruptive potential of a large subset of mt-rRNA variants. We have used HIA to explore the mutational landscape of 12S and 16S mt-rRNA genes. Our HIA studies include a thorough classification of all rare variants reported in the literature as well as others obtained from studies performed in collaboration with physicians. HIA has also been used with non-mammalian mt-rRNA genes to elucidate how mitotypes influence the interaction of the individual and the environment. Regarding mt-tRNA variations, rapidly growing evidence shows that the spectrum of mutations causing mitochondrial disease might differ between the different mitochondrial haplogroups seen in human populations.

Mitochondrial DNA Mutation Analysis in Breast Cancer: Shifting From Germline Heteroplasmy Toward Homoplasmy in Tumors

Studies have suggested a potential role of somatic mitochondrial mutations in cancer development. To analyze the landscape of somatic mitochondrial mutation in breast cancer and to determine whether mitochondrial DNA (mtDNA) mutational burden is correlated with overall survival (OS), we sequenced whole mtDNA from 92 matched-paired primary breast tumors and peripheral blood. A total of 324 germline variants and 173 somatic mutations were found in the tumors. The most common germline allele was 663G (12S), showing lower heteroplasmy levels in peripheral blood lymphocytes than in their matched tumors, even reaching homoplasmic status in several cases. The heteroplasmy load was higher in tumors than in their paired normal tissues. Somatic mtDNA mutations were found in 73.9% of breast tumors; 59% of these mutations were located in the coding region (66.7% non-synonymous and 33.3% synonymous). Although the CO1 gene presented the highest number of mutations, tRNA genes (T,C, and W), rRNA 12S, and CO1 and ATP6 exhibited the highest mutation rates. No specific mtDNA mutational profile was associated with molecular subtypes of breast cancer, and we found no correlation between mtDNA mutational burden and OS. Future investigations will provide insight into the molecular mechanisms through which mtDNA mutations and heteroplasmy shifting contribute to breast cancer development.

The Molecular Landscape of Hürthle Cell Thyroid Cancer Is Associated with Altered Mitochondrial Function-A Comprehensive Review

Hürthle cell thyroid carcinoma (HTC) accounts for 3-5% of all thyroid malignancies. Widely invasive HTC is characterized by poor prognosis and limited responsiveness to standard therapy with radioiodine. The molecular landscape of HTC is significantly different from the genetic signature seen in other forms of thyroid cancer. We performed a comprehensive literature review on the association between the molecular features of HTC and cancer metabolism. We searched the Pubmed, Embase, and Medline databases for clinical and translational studies published between 1980 and 2020 in English, coupling "HTC" with the following keywords: "genomic analysis", "mutations", "exome sequencing", "molecular", "mitochondria", "metabolism", "oxidative phosphorylation", "glycolysis", "oxidative stress", "reactive oxygen species", and "oncogenes". HTC is characterized by frequent complex I mitochondrial DNA mutations as early clonal events. This genetic signature is associated with the abundance of malfunctioning mitochondria in cancer cells. HTC relies predominantly on aerobic glycolysis as a source of energy production, as oxidative phosphorylation-related genes are downregulated. The enhanced glucose utilization by HTC is used for diagnostic purposes in the clinical setting for the detection of metastases by fluorodeoxyglucose positron emission tomography (FGD-PET/CT) imaging. A comprehensive metabolomic profiling of HTC in association with its molecular landscape might be necessary for the implementation of tumor-specific therapeutic approaches.

Mitochondria in cancer

The rediscovery and reinterpretation of the Warburg effect in the year 2000 occulted for almost a decade the key functions exerted by mitochondria in cancer cells. Until recent times, the scientific community indeed focused on constitutive glycolysis as a hallmark of cancer cells, which it is not, largely ignoring the contribution of mitochondria to the malignancy of oxidative and glycolytic cancer cells, being Warburgian or merely adapted to hypoxia. In this review, we highlight that mitochondria are not only powerhouses in some cancer cells, but also dynamic regulators of life, death, proliferation, motion and stemness in other types of cancer cells. Similar to the cells that host them, mitochondria are capable to adapt to tumoral conditions, and probably to evolve to ‘oncogenic mitochondria' capable of transferring malignant capacities to recipient cells. In the wider quest of metabolic modulators of cancer, treatments have already been identified targeting mitochondria in cancer cells, but the field is still in infancy.

Deregulated Mitochondrial DNA in Diseases

Mitochondria play various important roles in energy production, metabolism, and apoptosis. Mitochondrial dysfunction caused by alterations in mitochondrial DNA (mtDNA) can lead to the initiation and progression of cancers and other diseases. These alterations include mutations and copy number variations. Especially, the mutations in D-loop, MT-ND1, and MT-ND5 affect mitochondrial functions and are widely detected in various cancers. Meanwhile, several other mutations have been correlated with muscular and neuronal diseases, especially MT-TL1 is deeply related. These pieces of evidence indicated mtDNA alterations in diseases show potential as a novel therapeutic target. mtDNA repair enzymes are the target for delaying or stalling the mtDNA damage-induced cancer progression and metastasis. Moreover, some mutations reveal a prognosis ability of the drug resistance. Current efforts aim to develop mitochondrial transplantation technique as a direct cure for deregulated mitochondria-associated diseases. This review summarizes the implications of mitochondrial dysfunction in cancers and other pathologies; and discusses the relevance of mitochondria-targeted therapies, along with their contribution as potential biomarkers.

Detection of novel mitochondrial mutations in cytochrome C oxidase subunit 1 (COX1) in patients with familial adenomatous polyposis (FAP)

BACKGROUND

Familial adenomatous polyposis (FAP) is an Autosomal dominant inherited disorder and a rare form‌ of colorectal cancer (CRC) that is characterized by the development of hundreds to thousands of adenomas in the rectum and colon. Mostly, cancers develop after the advent of the polyps. It appears in both sexes evenly, and the occurrence of the disease is in the second decade of life. Mitochondrial genome mutations have been reported with a variety of Tumors, but the precise role of these mutations in the pathogenicity and tumor progression is not exactly clear. Cytochrome c oxidase subunit I (COX1) is the terminal enzyme of the mitochondrial respiratory chain. The present study aims at assessing the occurrence of mtDNA mutations in COX1 gene in FAP patients and attempts to find out the cause and effect relationship between mitochondrial mutations and tumor progression.

METHODS

In this study, 56 FAP patients were investigated for the presence of the mutations in mitochondrial COX1 coding gene by PCR and sequencing analysis. All sequences that differed from the revised Cambridge Reference Sequence (rCRS) were classified as missense/ nonsense or silent mutations. Functional genomic studies using Bio-informatics tools were performed on the founded mutations to understand the downstream alterations in structure and function of protein.

RESULTS

We identified 38 changes in the COX1 gene in patients with FAP symptoms. Most of them were heteroplasmic changes of missense type (25/38). Tree of the changes (G6145A, C6988A, and T7306G) were nonsense mutations and had not been reported in the literature before. Our results of bioinformatics predictions showed that the identified mutations can affect mitochondrial functions, especially if the conservative domain of the protein is concerned.

CONCLUSION

Our findings indicate a high frequency of mtDNA mutations in all of the FAP cases compared to matched controls. These data significantly enhance our understanding of how such mutations contribute to cancer pathologies and develop the cancer treatment methods by new diagnostic biomarkers, and new drugs for gene therapy.

Heteroplasmic Variants of Mitochondrial DNA in Atherosclerotic Lesions of Human Aortic Intima

Mitochondrial dysfunction and oxidative stress are likely involved in atherogenesis. Since the mitochondrial genome variation can alter functional activity of cells, it is necessary to assess the presence in atherosclerotic lesions of mitochondrial DNA (mtDNA) heteroplasmic mutations known to be associated with different pathological processes and ageing. In this study, mtDNA heteroplasmy and copy number (mtCN) were evaluated in the autopsy-derived samples of aortic intima differing by the type of atherosclerotic lesions. To detect mtDNA heteroplasmic variants, next generation sequencing was used, and mtCN measurement was performed by qPCR. It was shown that mtDNA heteroplasmic mutations are characteristic for particular areas of intimal tissue; in 83 intimal samples 55 heteroplasmic variants were found; mean minor allele frequencies level accounted for 0.09, with 12% mean heteroplasmy level. The mtCN variance measured in adjacent areas of intima was high, but atherosclerotic lesions and unaffected intima did not differ significantly in mtCN values. Basing on the ratio of minor and major nucleotide mtDNA variants, we can conclude that there exists the increase in the number of heteroplasmic mtDNA variants, which corresponds to the extent of atherosclerotic morphologic phenotype.

Mitochondrial oncobioenergetics of prostate tumorigenesis

Mitochondria are emerging as key players in the tumorigenic process of cells by maintaining the biosynthetic and energetic capabilities of cancer cells. It is now evident that mitochondria are involved in the malignant transformation, cell proliferation, aggression and metastatic behavior of prostate cancer (PC). Recent comprehensive analysis of the mitochondrial oncobioenergetic (MOB) profile of PC cells using microplate-based high resolution respirometry has clearly demonstrated that characteristic MOB alterations occur at different stages of PC development. Additionally, studies have reported that modification of the MOB profile significantly inhibits the growth of malignant cells. This observation suggests that dynamic alterations in the MOB function are a critical component in the development of malignant disease of the prostate. Therefore, quantification of MOB function may be a good marker for the prediction of tumor stage. Future studies may develop novel approaches to measure oncobioenergetics of tumors with minimal invasive procedures effectively in men to determine the general prostate health and tumor staging, and to predict whether a tumor will proceed to malignancy in patients. Additionally, since PC is a slow growing tumor, modulating the MOB profile at specific stages of tumor development may be a novel approach to treat or prevent PC.

Mitochondrial biology and prostate cancer ethnic disparity

Prostate cancer remains the second most prevalent cancer in men. Its incidence, progression and mortality profiles vary significantly by race and ethnicity, with African-American men having the highest incidence rate and mortality rate in the world. Although these disparities can be partially explained by socioeconomic factors, the underlying molecular causes are complex and require careful research. A considerable amount of literature exists, supporting the association between mitochondrial health and the incidence, aggression and risk of prostate cancer. Genetic alterations in mitochondrial DNA are frequent in prostate cancer; therefore, the resulting mitochondrial dysfunction and metabolic dysregulation may contribute to or indicate oncogenesis. Many of the prominent features of cancer cells are also closely related to mitochondrial functions, such as resistance to apoptosis, excess reactive oxygen species production and altered oxidative phosphorylation. In addition, prostate cancer ethnic disparity is influenced by environmental and lifestyle factors, which involves differences in mitochondrial metabolism and retrograde signaling events.

Roles of the mitochondrial genetics in cancer metastasis: not to be ignored any longer

Mitochondrial DNA (mtDNA) encodes for only a fraction of the proteins that are encoded within the nucleus, and therefore has typically been regarded as a lesser player in cancer biology and metastasis. Accumulating evidence, however, supports an increased role for mtDNA impacting tumor progression and metastatic susceptibility. Unfortunately, due to this delay, there is a dearth of data defining the relative contributions of specific mtDNA polymorphisms (SNP), which leads to an inability to effectively use these polymorphisms to guide and enhance therapeutic strategies and diagnosis. In addition, evidence also suggests that differences in mtDNA impact not only the cancer cells but also the cells within the surrounding tumor microenvironment, suggesting a broad encompassing role for mtDNA polymorphisms in regulating the disease progression. mtDNA may have profound implications in the regulation of cancer biology and metastasis. However, there are still great lengths to go to understand fully its contributions. Thus, herein, we discuss the recent advances in our understanding of mtDNA in cancer and metastasis, providing a framework for future functional validation and discovery.

Mitochondrial inheritance and cancer

Mitochondria are essential intracellular organelles that are responsible for energy metabolism, cell growth, and differentiation, redox homeostasis, oncogenic signaling, and apoptosis. These multifunctional organelles have been implicated in cancer initiation, progression, and metastasis, relapse, and acquired drug resistance due to metabolic alterations in transformed cells. Maternally inherited mitochondrial DNA (mtDNA) is thought to contribute to cancer development and prognosis and proposed as a therapeutic target for cancer treatment. In this review, we summarize the current knowledge of mtDNA alterations, with a specific focus on somatic changes, germline variants, haplogroups, large deletions, and mtDNA content changes associated with cancer susceptibility and prognosis. We also discuss the potential of mtDNA as biomarkers of cancer detection and targets of cancer treatment. Deeper understanding of the mechanisms underlying these associations requires further investigation.

Emerging evidence for targeting mitochondrial metabolic dysfunction in cancer therapy

Mammalian cells use a complex network of redox-dependent processes necessary to maintain cellular integrity during oxidative metabolism, as well as to protect against and/or adapt to stress. The disruption of these redox-dependent processes, including those in the mitochondria, creates a cellular environment permissive for progression to a malignant phenotype and the development of resistance to commonly used anticancer agents. An extension of this paradigm is that when these mitochondrial functions are altered by the events leading to transformation and ensuing downstream metabolic processes, they can be used as molecular biomarkers or targets in the development of new therapeutic interventions to selectively kill and/or sensitize cancer versus normal cells. In this Review we propose that mitochondrial oxidative metabolism is altered in tumor cells, and the central theme of this dysregulation is electron transport chain activity, folate metabolism, NADH/NADPH metabolism, thiol-mediated detoxification pathways, and redox-active metal ion metabolism. It is proposed that specific subgroups of human malignancies display distinct mitochondrial transformative and/or tumor signatures that may benefit from agents that target these pathways.

Tumor-Specific Mitochondrial DNA Variants Are Rarely Detected in Cell-Free DNA

The use of blood-circulating cell-free DNA (cfDNA) as a “liquid biopsy” in oncology is being explored for its potential as a cancer biomarker. Mitochondria contain their own circular genomic entity (mitochondrial DNA, mtDNA), up to even thousands of copies per cell. The mutation rate of mtDNA is several orders of magnitude higher than that of the nuclear DNA. Tumor-specific variants have been identified in tumors along the entire mtDNA, and their number varies among and within tumors. The high mtDNA copy number per cell and the high mtDNA mutation rate make it worthwhile to explore the potential of tumor-specific cf-mtDNA variants as cancer marker in the blood of cancer patients. We used single-molecule real-time (SMRT) sequencing to profile the entire mtDNA of 19 tissue specimens (primary tumor and/or metastatic sites, and tumor-adjacent normal tissue) and 9 cfDNA samples, originating from 8 cancer patients (5 breast, 3 colon). For each patient, tumor-specific mtDNA variants were detected and traced in cfDNA by SMRT sequencing and/or digital PCR to explore their feasibility as cancer biomarker. As a reference, we measured other blood-circulating biomarkers for these patients, including driver mutations in nuclear-encoded cfDNA and cancer-antigen levels or circulating tumor cells. Four of the 24 (17%) tumor-specific mtDNA variants were detected in cfDNA, however at much lower allele frequencies compared to mutations in nuclear-encoded driver genes in the same samples. Also, extensive heterogeneity was observed among the heteroplasmic mtDNA variants present in an individual. We conclude that there is limited value in tracing tumor-specific mtDNA variants in blood-circulating cfDNA with the current methods available.

Deciphering the Spectrum of Mitochondrial DNA Mutations in Hepatocellular Carcinoma Using High-Throughput Sequencing

Accumulation of mitochondrial DNA (mtDNA) mutations has been proposed to contribute to the initiation and progression of tumors. By using high-throughput sequencing strategies, we measured 33 specimens including 11 hepatocellular carcinoma (HCC) tissues, 11 corresponding adjacent tissues, and 11 normal liver tissues. We identified 194 single nucleotide variants (SNVs; including insert and deletion) in 33 liver tissues, and 13 somatic novel mutations were detected, including 7 mutations in the coding region. One of the seven somatic mutations (T7609C, 91.09%) is synonymous, which does not change amino acid coding; the other four somatic mutations (T6115C, 65.74%; G8387A, 12.23%; G13121A, 93.08%; and T14180C, 28.22%) could result in amino acid substitutions, potentially leading to mitochondrial dysfunction. Furthermore, two mutations in tRNA might influence amino acid transportation. Consistent with a previous study, we also found that mtDNA copy number was significantly reduced in HCC tissues. Therefore, we established a mitochondrial genome depletion cell line ρ0 and revealed that mtDNA loss reduced proliferation and migration in HCC cells but promoted their resistance to 5-fluorouracil. Our results suggested that somatic mtDNA mutations may cause mitochondrial dysfunction and affect chemoresistance of HCC cells. These new identified somatic mutations may serve as a reference for future studies of cancer mitochondrial genomes.

Alterations of Oxidative Phosphorylation Complexes in Papillary Thyroid Carcinoma

The papillary thyroid carcinoma (PTC) is the most common malignant tumor of the thyroid gland, with disruptive mutations in mitochondrial complex I subunits reported at very low frequency. Furthermore, metabolic diversity of PTC has been postulated owing to variable messenger RNA (mRNA) expression of genes encoding subunits of the oxidative phosphorylation (OXHPOS) complexes. The aim of the present study was to evaluate the metabolic diversity of the OXPHOS system at the protein level by using immunohistochemical staining. Analysis of 18 human PTCs revealed elevated mitochondrial biogenesis but significantly lower levels of OXPHOS complex I in the tumor tissue (p < 0.0001) compared to the adjacent normal tissue. In contrast, OXPHOS complexes II–V were increased in the majority of PTCs. In three PTCs, we found pathologic mutations within mitochondrially encoded complex I subunits. Our data indicate that PTCs are characterized by an oncocytic metabolic signature that is in low complex I is combined with elevated mitochondrial mass and high complex II–V levels, which might be an important factor for tumor formation.

Defining the momiome: Promiscuous information transfer by mobile mitochondria and the mitochondrial genome

Mitochondria are complex intracellular organelles that have long been identified as the powerhouses of eukaryotic cells because of the central role they play in oxidative metabolism. A resurgence of interest in the study of mitochondria during the past decade has revealed that mitochondria also play key roles in cell signaling, proliferation, cell metabolism and cell death, and that genetic and/or metabolic alterations in mitochondria contribute to a number of diseases, including cancer. Mitochondria have been identified as signaling organelles, capable of mediating bidirectional intracellular information transfer: anterograde (from nucleus to mitochondria) and retrograde (from mitochondria to nucleus). More recently, evidence is now building that the role of mitochondria extends to intercellular communication as well, and that the mitochondrial genome (mtDNA) and even whole mitochondria are indeed mobile and can mediate information transfer between cells. We define this promiscuous information transfer function of mitochondria and mtDNA as "momiome" to include all mobile functions of mitochondria and the mitochondrial genome. Herein, we review the "momiome" and explore its role in cancer development, progression, and treatment.

Multianalyte Tests for the Early Detection of Cancer: Speedbumps and Barriers

It has become very clear that a single molecular event is inadequate to accurately predict the biology (or pathophysiology) of cancer. Furthermore, using any single molecular event as a biomarker for the early detection of malignancy may not comprehensively identify the majority of individuals with that disease. Therefore, the fact that technologies have arisen that can simultaneously detect several, possibly hundreds, of biomarkers has propelled the field towards the development of multianalyte-based in vitro diagnostic early detection tests for cancer using body fluids such as serum, plasma, sputum, saliva, or urine. These multianalyte tests may be based on the detection of serum autoantibodies to tumor antigens, the presence of cancer-related proteins in serum, or the presence of tumor-specific genomic changes that appear in plasma as free DNA. The implementation of non-invasive diagnostic approaches to detect early stage cancer may provide the physician with evidence of cancer, but the question arises as to how the information will affect the pathway of clinical intervention. The confirmation of a positive result from an in vitro diagnostic cancer test may involve relatively invasive procedures to establish a true cancer diagnosis. If in vitro diagnostic tests are proven to be both specific, i.e. rarely produce false positive results due to unrelated conditions, and sufficiently sensitive, i.e. rarely produce false negative results, then such screening tests offer the potential for early detection and personalized therapeutics using multiple disease-related targets with convenient and non-invasive means. Here we discuss the technical and regulatory barriers inherent in development of clinical multianalyte biomarker assays.

Low circulating levels of the mitochondrial-peptide hormone SHLP2: novel biomarker for prostate cancer risk

CONTEXT

Mitochondrial DNA mutations and dysfunction are associated with prostate cancer (PCa). Small humanin-like peptide-2 (SHLP2) is a novel mitochondrial-encoded peptide and an important mitochondrial retrograde signaling molecule.

OBJECTIVE

To determine whether serum SHLP2 concentration is associated with PCa risk and whether associations are race-specific.Design, Setting and Participants: Patients undergoing prostate biopsy were recruited from the Durham Veterans Affairs hospital. Serum was collected prior to biopsy and SHLP2 measured by ELISA. We selected 200 men for analysis (100 negative biopsies and 100 PCa cases; 100 black and 100 white).

RESULTS

Mean SHLP2 levels were significantly higher in white controls versus black controls and SHLP2 was significantly higher in white controls versus white PCa cases. In contrast, there was no significant difference in SHLP2 levels between black controls and black cases. SHLP2 levels > 350-pg/ml ruled out PCa with ≥ 95% accuracy in both races.

CONCLUSIONS

Lower SHLP2 was linked with increased PCa risk in white men, but no significant association was observed in black men. While SHLP2 > 350-pg/ml ruled out PCa in both races with high accuracy, SHLP2 was unrelated to PCa grade. These data suggest the circulating mitochondrial-derived peptide hormone, SHLP2 plays a key role in the development and racial disparity of prostate cancer.

Mitochondrial genome variation and prostate cancer: a review of the mutational landscape and application to clinical management

Prostate cancer is a genetic disease. While next generation sequencing has allowed for the emergence of molecular taxonomy, classification is restricted to the nuclear genome. Mutations within the maternally inherited mitochondrial genome are known to impact cancer pathogenesis, as a result of disturbances in energy metabolism and apoptosis. With a higher mutation rate, limited repair and increased copy number compared to the nuclear genome, the clinical relevance of mitochondrial DNA (mtDNA) variation requires deeper exploration. Here we provide a systematic review of the landscape of prostate cancer associated mtDNA variation. While the jury is still out on the association between inherited mtDNA variation and prostate cancer risk, we collate a total of 749 uniquely reported prostate cancer associated somatic mutations. Support exists for number of somatic events, extent of heteroplasmy, and rate of recurrence of mtDNA mutations, increasing with disease aggression. While, the predicted pathogenic impact for recurrent prostate cancer associated mutations appears negligible, evidence exists for carcinogenic mutations impacting the cytochrome c oxidase complex and regulating metastasis through elevated reactive oxygen species production. Due to a lack of lethal cohort analyses, we provide additional unpublished data for metastatic disease. Discussing the advantages of mtDNA as a prostate cancer biomarker, we provide a review of current progress of including elevated mtDNA levels, of a large somatic deletion, acquired tRNAs mutations, heteroplasmy and total number of somatic events (mutational load). We confirm via meta-analysis a significant association between mtDNA mutational load and pathological staging at diagnosis or surgery (p < 0.0001).

Identification of sequence polymorphisms in the mitochondrial cytochrome c oxidase genes as risk factors for hepatocellular carcinoma

BACKGROUND

Single nucleotide polymorphisms (SNPs) accumulated in the mitochondrial DNA (mtDNA) is susceptible to the tumor formation. We discovered previously that SNPs in the mitochondrial displacement loop (D-loop) was associated with the risk of hepatocellular carcinoma (HCC).

METHODS

The cytochrome c oxidase (COX) genes of mtDNA were sequenced between 107 HCC patients and 100 matched healthy controls. The χ² test was used to analyze single SNPs' statistical difference between HCC patients and healthy controls.

RESULTS

In this study, cancer risk-associated SNPs in the COX genes of mtDNA coding region were assessed in HCC patients and health controls. The nucleotide position at site 9545A/G (P=.036) was identified its association for HCC with the 9545G allele susceptible to cancer risk.

CONCLUSIONS

The SNPs in the COX genes may help us to evaluate the cancer risk of HCC.

Folate deficiency as predisposing factor for childhood leukaemia: a review of the literature

BACKGROUND

Folic acid and its derivates, known as folates, are chemoprotective micronutrients of great interest because of their essential role in the maintenance of health and genomic integrity. The supplementation of folic acid during pregnancy has long been known to reduce the risk of neural tube defects (NTDs) in the foetus. Folate metabolism can be altered by many factors, including adequate intake through diet. Folate deficiency can compromise the synthesis, repair and methylation of DNA, with deleterious consequences on genomic stability and gene expression. These processes are known to be altered in chronic diseases, including cancer and cardiovascular diseases.

MAIN BODY

This review focuses on the association between folate intake and the risk of childhood leukaemia. Having compiled and analysed studies from the literature, we show the documented effects of folates on the genome and their role in cancer prevention and progression with particular emphasis on DNA methylation modifications. These changes are of crucial importance during pregnancy, as maternal diet has a profound impact on the metabolic and physiological functions of the foetus and the susceptibility to disease in later life. Folate deficiency is capable of modifying the methylation status of certain genes at birth in both animals and humans, with potential pathogenic and tumorigenic effects on the progeny. Pre-existing genetic polymorphisms can modify the metabolic network of folates and influence the risk of cancer, including childhood leukaemias. The protective effects of folic acid might be dose dependent, as excessive folic acid could have the adverse effect of nourishing certain types of tumours.

CONCLUSION

Overall, maternal folic acid supplementation before and during pregnancy seems to confer protection against the risk of childhood leukaemia in the offspring. The optimal folic acid requirements and supplementation doses need to be established, especially in conjunction with other vitamins in order to determine the most successful combinations of nutrients to maintain genomic health and wellbeing. Further research is therefore needed to uncover the role of maternal diet as a whole, as it represents a main factor capable of inducing permanent changes in the foetus.

Energy metabolism in skin cancers: A therapeutic perspective

Skin cancers are the most common cancers worldwide. The incidence of common skin cancers, including basal cell carcinomas (BCCs), squamous cell carcinomas (SCCs) and melanomas, continues to rise by 5 to 7% per year, mainly due to ultraviolet (UV) exposure and partly because of aging. This suggests an urgent necessity to improve the level of prevention and protection for skin cancers as well as developing new prognostic and diagnostic markers of skin cancers. Moreover, despite innovative therapies especially in the fields of melanoma and carcinomas, new therapeutic options are needed to bypass resistance to targeted therapies or treatment's side effects. Since reprogramming of cellular metabolism is now considered as a hallmark of cancer, some of the recent findings on the role of energy metabolism in skin cancer initiation and progression as well as its effect on the response to targeted therapies are discussed in this review. This article is part of a Special Issue entitled Mitochondria in cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.

Mitochondrial Changes in Cancer

Mitochondrial structural and functional integrity defines the health of a cell by regulating cellular metabolism. Thus, mitochondria play an important role in both cell proliferation and cell death. Cancer cells are metabolically altered compared to normal cells for their ability to survive better and proliferate faster. Resistance to apoptosis is an important characteristic of cancer cells and given the contribution of mitochondria to apoptosis, it is imperative that mitochondria could behave differently in a tumor situation. The other feature associated with cancer cells is the Warburg effect, which engages a shift in metabolism. Although the Warburg effect often occurs in conjunction with dysfunctional mitochondria, the relationship between mitochondria, the Warburg effect, and cancer cell metabolism is not clearly decoded. Other than these changes, several mitochondrial gene mutations occur in cancer cells, mitochondrial biogenesis is affected and mitochondria see structural and functional variations. In cancer pharmacology, targeting mitochondria and mitochondria associated signaling pathways to reduce tumor proliferation is a growing field of interest. This chapter summarizes various changes in mitochondria in relevance to cancer, behavior of mitochondria during tumorigenesis, and the progress on using mitochondria as a therapeutic target for cancer.

Spotlight on the relevance of mtDNA in cancer

The potential role of the mitochondrial genome has recently attracted interest because of its high mutation frequency in tumors. Different aspects of mtDNA make it relevant for cancer's biology, such as it encodes a limited but essential number of genes for OXPHOS biogenesis, it is particularly susceptible to mutations, and its copy number can vary. Moreover, most ROS in mitochondria are produced by the electron transport chain. These characteristics place the mtDNA in the center of multiple signaling pathways, known as mitochondrial retrograde signaling, which modifies numerous key processes in cancer. Cybrid studies support that mtDNA mutations are relevant and exert their effect through a modification of OXPHOS function and ROS production. However, there is still much controversy regarding the clinical relevance of mtDNA mutations. New studies should focus more on OXPHOS dysfunction associated with a specific mutational signature rather than the presence of mutations in the mtDNA.

A Comprehensive Characterization of Mitochondrial Genome in Papillary Thyroid Cancer

Nuclear genetic alterations have been widely investigated in papillary thyroid cancer (PTC), however, the characteristics of the mitochondrial genome remain uncertain. We sequenced the entire mitochondrial genome of 66 PTCs, 16 normal thyroid tissues and 376 blood samples of healthy individuals. There were 2508 variations (543 sites) detected in PTCs, among which 33 variations were novel. Nearly half of the PTCs (31/66) had heteroplasmic variations. Among the 31 PTCs, 28 specimens harbored a total of 52 somatic mutations distributed in 44 sites. Thirty-three variations including seven nonsense, 11 frameshift and 15 non-synonymous variations selected by bioinformatic software were regarded as pathogenic. These 33 pathogenic mutations were associated with older age (p = 0.0176) and advanced tumor stage (p = 0.0218). In addition, they tended to be novel (p = 0.0003), heteroplasmic (p = 0.0343) and somatic (p = 0.0018). The mtDNA copy number increased in more than two-third (46/66) of PTCs, and the average content in tumors was nearly four times higher than that in adjacent normal tissues (p < 0.0001). Three sub-haplogroups of N (A4, B4a and B4g) and eight single-nucleotide polymorphisms (mtSNPs) (A16164G, C16266T, G5460A, T6680C, G9123A, A14587G, T16362C, and G709A) were associated with the occurrence of PTC. Here we report a comprehensive characterization of the mitochondrial genome and demonstrate its significance in pathogenesis and progression of PTC. This can help to clarify the molecular mechanisms underlying PTC and offer potential biomarkers or therapeutic targets for future clinical practice.

Mitochondrial DNA copy number in peripheral blood leukocytes and the aggressiveness of localized prostate cancer

We investigated whether low mitochondrial DNA copy number (mtDNAcn) in peripheral blood leukocytes at diagnosis was associated with an increased risk of the aggressive form of the tumor and disease progression among localized prostate cancer (PCa) patients. We recruited 1,751 non-Hispanic white men with previously untreated PCa from The University of Texas MD Anderson Cancer Center. mtDNAcn was categorized into three groups according to tertiles. We used multivariate logistic regression to estimate the odds ratios (ORs) and 95 percent confidence intervals (95% CIs) for the association of mtDNAcn with the risk of having aggressive PCa at diagnosis. We used Cox proportional hazards model to estimate hazard ratios (HRs) and 95% CIs for disease progression. We observed an inverse association between aggressiveness of PCa and mtDNAcn (P < 0.001). In multivariate analysis, compared to patients in the highest tertile of mtDNAcn, those in the second and lowest tertiles had significantly increased risks of presenting with the high-risk form of PCa, as defined by the D'Amico criteria, with ORs of 1.33 (95% CI, 0.89–1.98; P = 0.17) and 1.53 (95% CI, 1.02–2.30; P = 0.04), respectively. Furthermore, PCa patients in the lowest and second tertiles combined relative to those in the highest tertile had a 56% increased risk of disease progression (HR, 1.56; 95% CI, 0.96–2.54; P = 0.07). In summary, our results suggested that low mtDNAcn in peripheral blood leukocytes was associated with aggressive PCa at diagnosis and might further predict poor progression-free survival among localized PCa patients.

Genetic variants in ATP6 and ND3 mitochondrial genes are not associated with aggressive prostate cancer in Mexican-Mestizo men with overweight or obesity

Mitochondrial defects have been related to obesity and prostate cancer. We investigated if Mexican-Mestizo men presenting this type of cancer, exhibited somatic mutations of ATP6 and/or ND3.Body mass index (BMI) was determined; the degree of prostate cancer aggressiveness was demarcated by the Gleason score. DNA from tumor tissue and from blood leukocytes was amplified by the polymerase chain reaction and ATP6 and ND3 were sequenced. We included 77 men: 20 had normal BMI, 38 were overweight and 19 had obesity; ages ranged from 52 to 83. After sequencing ATP6 and ND3, from DNA obtained from leukocytes and tumor tissue, we did not find any somatic mutations. All changes observed, in both genes, were polymorphisms. In ATP6 we identified, in six patients, two non-synonymous nucleotide changes and in ND3 we observed that twelve patients presented non-synonymous polymorphisms. To our knowledge, this constitutes the first report where the complete sequences of the ATP6 and ND3 have been analyzed in Mexican-Mestizo men with prostate cancer and diverse BMI. Our results differ with those reported in Caucasian populations, possibly due to ethnic differences.

Role of mitochondrial dysfunction in cancer progression

Deregulated cellular energetics was one of the cancer hallmarks. Several underlying mechanisms of deregulated cellular energetics are associated with mitochondrial dysfunction caused by mitochondrial DNA mutations, mitochondrial enzyme defects, or altered oncogenes/tumor suppressors. In this review, we summarize the current understanding about the role of mitochondrial dysfunction in cancer progression. Point mutations and copy number changes are the two most common mitochondrial DNA alterations in cancers, and mitochondrial dysfunction induced by chemical depletion of mitochondrial DNA or impairment of mitochondrial respiratory chain in cancer cells promotes cancer progression to a chemoresistance or invasive phenotype. Moreover, defects in mitochondrial enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, are associated with both familial and sporadic forms of cancer. Deregulated mitochondrial deacetylase sirtuin 3 might modulate cancer progression by regulating cellular metabolism and oxidative stress. These mitochondrial defects during oncogenesis and tumor progression activate cytosolic signaling pathways that ultimately alter nuclear gene expression, a process called retrograde signaling. Changes in the intracellular level of reactive oxygen species, Ca(2+), or oncometabolites are important in the mitochondrial retrograde signaling for neoplastic transformation and cancer progression. In addition, altered oncogenes/tumor suppressors including hypoxia-inducible factor 1 and tumor suppressor p53 regulate mitochondrial respiration and cellular metabolism by modulating the expression of their target genes. We thus suggest that mitochondrial dysfunction plays a critical role in cancer progression and that targeting mitochondrial alterations and mitochondrial retrograde signaling might be a promising strategy for the development of selective anticancer therapy.

Spectrum of mitochondrial genomic variation and associated clinical presentation of prostate cancer in South African men

BACKGROUND

Prostate cancer incidence and mortality rates are significantly increased in African-American men, but limited studies have been performed within Sub-Saharan African populations. As mitochondria control energy metabolism and apoptosis we speculate that somatic mutations within mitochondrial genomes are candidate drivers of aggressive prostate carcinogenesis.

METHODS

We used matched blood and prostate tissue samples from 87 South African men (77 with African ancestry) to perform deep sequencing of complete mitochondrial genomes. Clinical presentation was biased toward aggressive disease (Gleason score >7, 64%), and compared with men without prostate cancer either with or without benign prostatic hyperplasia.

RESULTS

We identified 144 somatic mtDNA single nucleotide variants (SNVs), of which 80 were observed in 39 men presenting with aggressive disease. Both the number and frequency of somatic mtDNA SNVs were associated with higher pathological stage.

CONCLUSIONS

Besides doubling the total number of somatic PCa-associated mitochondrial genome mutations identified to date, we associate mutational load with aggressive prostate cancer status in men of African ancestry.

Complex-I Alteration and Enhanced Mitochondrial Fusion Are Associated With Prostate Cancer Progression

Mitochondria (mt) encoded respiratory complex-I (RCI) mutations and their pathogenicity remain largely unknown in prostate cancer (PCa). Little is known about the role of mtDNA loss on mt integrity in PCa. We determined mtDNA mutation in human and mice PCa and assessed the impact of mtDNA depletion on mt integrity. We also examined whether the circulating exosomes from PCa patients are transported to mt and carry mtDNA or mt proteins. We have employed next generation sequencing of the whole mt genome in human and Hi-myc PCa. The impact of mtDNA depletion on mt integrity, presence of mtDNA, and protein in sera exosomes was determined. A co-culture of human PCa cells and the circulating exosomes followed by confocal imaging determined co-localization of exosomes and mt. We observed frequent RCI mutations in human and Hi-myc PCa which disrupted corresponding complex protein expression. Depletion of mtDNA in PCa cells influenced mt integrity, increased expression of MFN1, MFN2, PINK1, and decreased expression of MT-TFA. Increased mt fusion and expression of PINK1 and DNM1L were also evident in the Hi-myc tumors. RCI-mtDNA, MFN2, and IMMT proteins were detected in the circulating exosomes of men with benign prostate hyperplasia (BPH) and progressive PCa. Circulating exosomes and mt co-localized in PCa cells. Our study identified new pathogenic RCI mutations in PCa and defined the impact of mtDNA loss on mt integrity. Presence of mtDNA and mt proteins in the circulating exosomes implicated their usefulness for biomarker development.

The presence of highly disruptive 16S rRNA mutations in clinical samples indicates a wider role for mutations of the mitochondrial ribosome in human disease

Mitochondrial DNA mutations are well recognized as an important cause of disease, with over two hundred variants in the protein encoding and mt-tRNA genes associated with human disorders. In contrast, the two genes encoding the mitochondrial rRNAs (mt-rRNAs) have been studied in far less detail. This is because establishing the pathogenicity of mt-rRNA mutations is a major diagnostic challenge. Only two disease causing mutations have been identified at these loci, both mapping to the small subunit (SSU). On the large subunit (LSU), however, the evidence for the presence of pathogenic LSU mt-rRNA changes is particularly sparse. We have previously expanded the list of deleterious SSU mt-rRNA mutations by identifying highly disruptive base changes capable of blocking the activity of the mitoribosomal SSU. To do this, we used a new methodology named heterologous inferential analysis (HIA). The recent arrival of near-atomic-resolution structures of the human mitoribosomal LSU, has enhanced the power of our approach by permitting the analysis of the corresponding sites of mutation within their natural structural context. Here, we have used these tools to determine whether LSU mt-rRNA mutations found in the context of human disease and/or ageing could disrupt the function of the mitoribosomal LSU. Our results clearly show that, much like the for SSU mt-rRNA, LSU mt-rRNAs mutations capable of compromising the function of the mitoribosomal LSU are indeed present in clinical samples. Thus, our work constitutes an important contribution to an emerging view of the mitoribosome as an important element in human health.

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Identification of pathogenic mutations of mitochondrial rRNAs is problematic.

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We analysed 64 rare 16S rRNA mutations obtained from clinical samples.

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The mutations underwent heterologous inferential analysis (HIA).

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We show that highly disruptive 16S rRNA mutations are present in clinical samples.

Molecular markers in bladder cancer: Novel research frontiers

Bladder cancer (BC) is a heterogeneous disease encompassing distinct biologic features that lead to extremely different clinical behaviors. In the last 20 years, great efforts have been made to predict disease outcome and response to treatment by developing risk assessment calculators based on multiple standard clinical-pathological factors, as well as by testing several molecular markers. Unfortunately, risk assessment calculators alone fail to accurately assess a single patient's prognosis and response to different treatment options. Several molecular markers easily assessable by routine immunohistochemical techniques hold promise for becoming widely available and cost-effective tools for a more reliable risk assessment, but none have yet entered routine clinical practice. Current research is therefore moving towards (i) identifying novel molecular markers; (ii) testing old and new markers in homogeneous patients' populations receiving homogeneous treatments; (iii) generating a multimarker panel that could be easily, and thus routinely, used in clinical practice; (iv) developing novel risk assessment tools, possibly combining standard clinical-pathological factors with molecular markers. This review analyses the emerging body of literature concerning novel biomarkers, ranging from genetic changes to altered expression of a huge variety of molecules, potentially involved in BC outcome and response to treatment. Findings suggest that some of these indicators, such as serum circulating tumor cells and tissue mitochondrial DNA, seem to be easily assessable and provide reliable information. Other markers, such as the phosphoinositide-3-kinase (PI3K)/AKT (serine-threonine kinase)/mTOR (mammalian target of rapamycin) pathway and epigenetic changes in DNA methylation seem to not only have prognostic/predictive value but also, most importantly, represent valuable therapeutic targets. Finally, there is increasing evidence that the development of novel risk assessment tools combining standard clinical-pathological factors with molecular markers represents a major quest in managing this poorly predictable disease.

Mitochondrial DNA somatic mutation in cancer

Cancer cells are known to drastically alter cellular energy metabolism. The Warburg effect has been known for over 80 years as pertaining cancer-specific aerobic glycolysis. As underlying molecular mechanisms are elucidated so that cancer cells alter the cellular energy metabolism for their advantage, the significance of the modulation of metabolic profiles is gaining attention. Now, metabolic reprogramming is becoming an emerging hallmark of cancer. Therapeutic agents that target cancer energy metabolism are under intensive investigation, but these investigations are mostly focused on the cytosolic glycolytic processes. Although mitochondrial oxidative phosphorylation is an integral part of cellular energy metabolism, until recently, it has been regarded as an auxiliary to cytosolic glycolytic processes in cancer energy metabolism. In this review, we will discuss the importance of mitochondrial respiration in the metabolic reprogramming of cancer, in addition to discussing the justification for using mitochondrial DNA somatic mutation as metabolic determinants for cancer sensitivity in glucose limitation.

Generation of blood circulating DNA: the sources, peculiarities of circulation and structure

Extracellular nucleic acids (exNA) were described in blood of both healthy and illness people as early as in 1948, but staied overlooked until middle 60-th. Starting from the beginning of new millennium and mainly in the last 5 years exNA are intensively studied. Main attention is directed to investigation of exNA as the source of diagnostic material whereas the mechanisms of their generation, as well as mechanisms to providing long-term circulation of exNA in the bloodstream are not established unambiguously. According to some authors, the main source of circulating nucleic acids in blood are the processes of apoptosis and necrosis, while others refer to the possible nucleic acid secretion by healthy and tumor cells. Circulating DNA were found to be stable in the blood for a long time, escaping from the action of DNA hydrolyzing enzymes and are apparently packed in different supramolecular complexes. This review presents the opinions of various authors and evidence in favor of all the theories describingappearance of extracellular DNA, the features of the circulation and structure of the extracellular DNA and factors affecting the time of DNA circulation in blood

Mitochondrial DNA levels in blood and tissue samples from breast cancer patients of different stages

AIMS

Alterations in mitochondrial DNA (mtDNA) have been implicated in carcinogenesis and tumor progression. We here evaluated the diagnostic and prognostic potential of mtDNA as a biomarker for breast cancer.

METHODS

Using multiplex real-time polymerase chain reaction, nuclear DNA (nDNA) and mtDNA levels in serum, buffy coat, tumor, and tumor-adjacent tissue samples from 50 breast cancer patients were determined and assessed for associations with clinicopathological features. To evaluate mtDNA as a biomarker for distinguishing between the four sample types, we created receiver operating characteristic (ROC) curves.

RESULTS

The mtDNA levels in buffy coat were significantly lower than in other sample types. Relative to tumor-adjacent tissue, reduced levels of mtDNA were identified in buffy coat and tumor tissue but not in serum. According to ROC curve analysis, mtDNA levels could be used to distinguish between buffy coat and tumor-adjacent tissue samples with good sensitivity (77%) and specificity (83%). Moreover, mtDNA levels in serum and tumor tissue were positively associated with cancer TMN stage.

CONCLUSIONS

The mtDNA levels in blood samples may represent a promising, non-invasive biomarker in breast cancer patients. Additional, large-scale validation studies are required to establish the potential use of mtDNA levels in the early diagnosis and monitoring of breast cancer.

Structure of the large ribosomal subunit from human mitochondria

Human mitochondrial ribosomes are highly divergent from all other known ribosomes and are specialized to exclusively translate membrane proteins. They are linked with hereditary mitochondrial diseases and are often the unintended targets of various clinically useful antibiotics. Using single-particle cryogenic electron microscopy, we have determined the structure of its large subunit to 3.4 angstrom resolution, revealing 48 proteins, 21 of which are specific to mitochondria. The structure unveils an adaptation of the exit tunnel for hydrophobic nascent peptides, extensive remodeling of the central protuberance, including recruitment of mitochondrial valine transfer RNA (tRNA(Val)) to play an integral structural role, and changes in the tRNA binding sites related to the unusual characteristics of mitochondrial tRNAs.