DNA damage, mutation and fine structure DNA repair in aging

Pancreatic β-cell mitophagy as an adaptive response to metabolic stress and the underlying mechanism that involves lysosomal Ca2+ release

Mitophagy is an excellent example of selective autophagy that eliminates damaged or dysfunctional mitochondria, and it is crucial for the maintenance of mitochondrial integrity and function. The critical roles of autophagy in pancreatic β-cell structure and function have been clearly shown. Furthermore, morphological abnormalities and decreased function of mitochondria have been observed in autophagy-deficient β-cells, suggesting the importance of β-cell mitophagy. However, the role of authentic mitophagy in β-cell function has not been clearly demonstrated, as mice with pancreatic β-cell-specific disruption of Parkin, one of the most important players in mitophagy, did not exhibit apparent abnormalities in β-cell function or glucose homeostasis. Instead, the role of mitophagy in pancreatic β-cells has been investigated using β-cell-specific Tfeb-knockout mice (TfebΔβ-cell mice); Tfeb is a master regulator of lysosomal biogenesis or autophagy gene expression and participates in mitophagy. TfebΔβ-cell mice were unable to adaptively increase mitophagy or mitochondrial complex activity in response to high-fat diet (HFD)-induced metabolic stress. Consequently, TfebΔβ-cell mice exhibited impaired β-cell responses and further exacerbated metabolic deterioration after HFD feeding. TFEB was activated by mitochondrial or metabolic stress-induced lysosomal Ca2+ release, which led to calcineurin activation and mitophagy. After lysosomal Ca2+ release, depleted lysosomal Ca2+ stores were replenished by ER Ca2+ through ER→lysosomal Ca2+ refilling, which supplemented the low lysosomal Ca2+ capacity. The importance of mitophagy in β-cell function was also demonstrated in mice that developed β-cell dysfunction and glucose intolerance after treatment with a calcineurin inhibitor that hampered TFEB activation and mitophagy.

β Cell and Autophagy: What Do We Know?

Pancreatic β cells are central to glycemic regulation through insulin production. Studies show autophagy as an essential process in β cell function and fate. Autophagy is a catabolic cellular process that regulates cell homeostasis by recycling surplus or damaged cell components. Impaired autophagy results in β cell loss of function and apoptosis and, as a result, diabetes initiation and progress. It has been shown that in response to endoplasmic reticulum stress, inflammation, and high metabolic demands, autophagy affects β cell function, insulin synthesis, and secretion. This review highlights recent evidence regarding how autophagy can affect β cells' fate in the pathogenesis of diabetes. Furthermore, we discuss the role of important intrinsic and extrinsic autophagy modulators, which can lead to β cell failure.

Is Evidence Supporting the Subtelomere-Telomere Theory of Aging?

The telomere theory tries to explain cellular mechanisms of aging as mainly caused by telomere shortening at each duplication. The subtelomere-telomere theory overcomes various shortcomings of telomere theory by highlighting the essential role of subtelomeric DNA in aging mechanisms. The present work illustrates and deepens the correspondence between assumptions and implications of subtelomere-telomere theory and experimental results. In particular, it is investigated the evidence regarding the relationships between aging and (i) epigenetic modifications; (ii) oxidation and inflammation; (iii) telomere protection; (iv) telomeric heterochromatin hood; (v) gradual cell senescence; (vi) cell senescence; and (vii) organism decline with telomere shortening. The evidence appears broadly in accordance or at least compatible with the description and implications of the subtelomere-telomere theory. In short, phenomena of cellular aging, by which the senescence of the whole organism is determined in various ways, appear substantially dependent on epigenetic modifications regulated by the subtelomere-telomere-telomeric hood-telomerase system. These phenomena appear to be not random, inevitable, and irreversible but rather induced and regulated by genetically determined mechanisms, and modifiable and reversible by appropriate methods. All this supports the thesis that aging is a genetically programmed and regulated phenoptotic phenomenon and is against the opposite thesis of aging as caused by random and inevitable degenerative factors.

The emerging role of Cockayne group A and B proteins in ubiquitin/proteasome-directed protein degradation

When mutated, csa and csb genes are responsible of the complex phenotype of the premature aging Cockayne Syndrome (CS). Our working hypothesis is to reconcile the multiple cellular and molecular phenotypes associated to CS within the unifying molecular function of CSA and CSB proteins in the cascade of events leading to ubiquitin/proteasome-directed protein degradation, which occurs in processes as DNA repair, transcription and cell division. This achievement may reasonably explain the plethora of cellular UPS-regulated functions that result impaired when either CSA or CSB are mutated and suggestively explains part of their pleiotropic effect. This review is aimed to solicit the interest of the scientific community in further investigating this aspect, since we believe that the identification of the ubiquitin-proteasome machinery as a new potential therapeutic target, able to comprehensively face the different molecular aspects of CS, whether confirmed and corroborated by in vivo studies, would open a promising avenue to design effective therapeutic intervention.

Astaxanthin protects oxidative stress mediated DNA damage and enhances longevity in Saccharomyces cerevisiae

Reactive oxygen species (ROS) have long been found to play an important role in oxidative mediated DNA damage. Fortunately, cells possess an antioxidant system that can neutralize ROS. However, oxidative stress occurs when antioxidants are overwhelmed by ROS or impaired antioxidant pathways. This study was carried out to find the protective effect of astaxanthin on the yeast DNA repair-deficient mutant cells under hydrogen peroxide stress. The results showed that astaxanthin enhances the percent cell growth of rad1∆, rad51∆, apn1∆, apn2∆ and ogg1∆ cells. Further, the spot test and colony-forming unit count results confirmed that astaxanthin protects DNA repair mutant cells from oxidative stress. The DNA binding property of astaxanthin studied by in silico and in vitro methods indicated that astaxanthin binds to the DNA in the major and minor groove, and that might protect DNA against oxidative stress induced by Fenton's reagent. The intracellular ROS, 8-OHdG level and the DNA fragmentation as measured by comet tail was reduced by astaxanthin under oxidative stress. Similarly, reduced nuclear fragmentation and chromatin condensation results suggest that astaxanthin might reduce apoptosis. Finally, we show that astaxanthin decreases the accumulation of mutation rate and enhances the longevity of DNA repair-deficient mutants' cells during a chronological lifespan.

β-cell autophagy: Mechanism and role in β-cell dysfunction

Background

Elucidation of the basic molecular mechanism of autophagy was a breakthrough in understanding various physiological events and pathogenesis of diverse diseases. In the fields of diabetes and metabolism, many cellular events associated with the development of disease or its treatment cannot be explained well without taking autophagy into account. While a grand picture of autophagy has been established, detailed aspects of autophagy, particularly that of selective autophagy responsible for homeostasis of specific organelles or metabolic intermediates, are still ambiguous and currently under intensive research.

Scope of review

Here, results from previous and current studies on the role of autophagy and its dysregulation in the physiology of metabolism and pathogenesis of diabetes are summarized, with an emphasis on the pancreatic β-cell autophagy. In addition to nonselective (bulk) autophagy, machinery and significance of selective autophagy such as mitophagy of pancreatic β-cells is discussed. Novel findings regarding autophagy types other than macroautophagy are also covered, since several types of autophagy or lysosomal degradation pathways other than macroautophagy coexist in pancreatic β-cells.

Major conclusion

Autophagy plays a critical role in cellular metabolism, homeostasis of the intracellular environment and function of organelles such as mitochondria and endoplasmic reticulum. Impaired autophagic activity due to aging, obesity or genetic predisposition could be a factor in the development of β-cell dysfunction and diabetes associated with lipid overload or human-type diabetes characterized by islet amyloid deposition. Modulation of autophagy of pancreatic β-cells is likely to be possible in the near future, which would be valuable in the treatment of diabetes associated with lipid overload or accumulation of islet amyloid.

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Autophagy is critical for cellular metabolism, homeostasis and organelle function.

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Impaired autophagic activity could predispose to β-cell dysfunction and diabetes.

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Several types of autophagy coexist in pancreatic β-cells.

Mitochondria, spermatogenesis, and male infertility - An update

The incorporation of mitochondria in the eukaryotic cell is one of the most enigmatic events in the course of evolution. This important organelle was thought to be only the powerhouse of the cell, but was later learnt to perform many other indispensable functions in the cell. Two major contributions of mitochondria in spermatogenesis concern energy production and apoptosis. Apart from this, mitochondria also participate in a number of other processes affecting spermatogenesis and fertility. Mitochondria in sperm are arranged in the periphery of the tail microtubules to serve to energy demand for motility. Apart from this, the role of mitochondria in germ cell proliferation, mitotic regulation, and the elimination of germ cells by apoptosis are now well recognized. Eventually, mutations in the mitochondrial genome have been reported in male infertility, particularly in sluggish sperm (asthenozoospermia); however, heteroplasmy in the mtDNA and a complex interplay between the nucleus and mitochondria affect their penetrance. In this article, we have provided an update on the role of mitochondria in various events of spermatogenesis and male fertility and on the correlation of mitochondrial DNA mutations with male infertility.

Enhanced expression of thioredoxin-interacting-protein regulates oxidative DNA damage and aging

The "free radical theory of aging" suggests that reactive oxygen species (ROS) are responsible for age-related loss of cellular functions and, therefore, represent the main cause of aging. Redox regulation by thioredoxin-1 (TRX) plays a crucial role in responses to oxidative stress. We show that thioredoxin-interacting protein (TXNIP), a negative regulator of TRX, plays a major role in maintaining the redox status and, thereby, influences aging processes. This role of TXNIP is conserved from flies to humans. Age-dependent upregulation of TXNIP results in decreased stress resistance to oxidative challenge in primary human cells and in Drosophila. Experimental overexpression of TXNIP in flies shortens lifespan due to elevated oxidative DNA damage, whereas downregulation of TXNIP enhances oxidative stress resistance and extends lifespan.

Epigenetics and Oxidative Stress in Aging

Aging is a multifactorial process characterized by the progressive loss of physiological functions, leading to an increased vulnerability to age-associated diseases and finally to death. Several theories have been proposed to explain the nature of aging. One of the most known identifies the free radicals produced by the mitochondrial metabolism as the cause of cellular and DNA damage. However, there are also several evidences supporting that epigenetic modifications, such as DNA methylation, noncoding RNAs, and histone modifications, play a critical role in the molecular mechanism of aging. In this review, we explore the significance of these findings and argue how the interlinked effects of oxidative stress and epigenetics can explain the cause of age-related declines.

Histopathologic Features Seen with Radiation Recall or Enhancement Eruptions

Background:

Although a radiation recall or enhancement eruption has been associated with a number of chemotherapeutic drugs, the histologic features have rarely been described.

Objective:

Our goal was to define the histologic features of radiation recall and enhancement eruptions in order to better understand their pathogenesis.

Methods:

We present ten patients on chemotherapeutic agents who developed erythematous maculopapular to psoriasiform eruptions often with associated follicular pustules. These eruptions occurred at the sites of prior or concurrent radiation therapy.

Results:

The most common class of drugs inducing these reactions were antibiotic chemotherapeutic agents alone or in combination with other chemotherapeutic drugs. In addition to routine histology, in four patients immunohistochemical staining for p53 was performed at the sites of the eruptions after resolution and at noninvolved sites matched for ultraviolet radiation (UVR) exposure. Histologic features in patients receiving concurrent radiation therapy included epidermal dysplasia, keratinocytes showing features of necrosis, increased mitotic figures, and a mixed inflammatory infiltrate. At sites of prior radiation therapy, the biopsy specimens showed a similar spectrum of epidermal changes and, in some cases, psoriasiform dermatitis with clearing within cells in the upper layers of the epidermis. Additional dermal changes included dermal fibrosis, vasodilatation, and atypical fibroblasts. Moderate to marked solar elastosis was seen in the majority of biopsy specimens. Immunohistochemical studies after resolution showed only a modest increase in p53 staining in epidermal keratinocytes in 3 of 4 sites of recall and enhancement eruptions after resolution of the reactions compared to skin that was matched for similar UVR exposure.

Conclusion:

Cumulative direct DNA damage and oxidative stress are probably important in radiation recall and enhancement eruptions, and these changes may be modulated by underlying nutritional deficits. Cumulative p53 mutations may play some role but are probably not a major factor in these eruptions. Mitochondrial dysfunction, which is known to occur with prior and concurrent radiation and chemotherapy, may be important in these eruptions. In addition to improvements in general nutrition, topical or oral antioxidant therapy may be a potential therapy to avoid radiation enhancement and recall reactions.

Age-Specific Gene Expression Profiles of Rhesus Monkey Ovaries Detected by Microarray Analysis

The biological function of human ovaries declines with age. To identify the potential molecular changes in ovarian aging, we performed genome-wide gene expression analysis by microarray of ovaries from young, middle-aged, and old rhesus monkeys. Microarray data was validated by quantitative real-time PCR. Results showed that a total of 503 (60 upregulated, 443 downregulated) and 84 (downregulated) genes were differentially expressed in old ovaries compared to young and middle-aged groups, respectively. No difference in gene expression was found between middle-aged and young groups. Differentially expressed genes were mainly enriched in cell and organelle, cellular and physiological process, binding, and catalytic activity. These genes were primarily associated with KEGG pathways of cell cycle, DNA replication and repair, oocyte meiosis and maturation, MAPK, TGF-beta, and p53 signaling pathway. Genes upregulated were involved in aging, defense response, oxidation reduction, and negative regulation of cellular process; genes downregulated have functions in reproduction, cell cycle, DNA and RNA process, macromolecular complex assembly, and positive regulation of macromolecule metabolic process. These findings show that monkey ovary undergoes substantial change in global transcription with age. Gene expression profiles are useful in understanding the mechanisms underlying ovarian aging and age-associated infertility in primates.

The paradoxical role of thioredoxin on oxidative stress and aging

In spite of intensive study, there is still controversy about the free radical or oxidative stress theory of aging, particularly in mammals. Our laboratory has conducted the first detailed studies on the role of thioredoxin (Trx) in the cytosol (Trx1) and in mitochondria (Trx2) on oxidative stress and aging using unique mouse models either overexpressing or down-regulating Trx1 or Trx2. The results generated from our lab and others indicate that: (1) oxidative stress and subsequent changes in signaling pathways could have different pathophysiological impacts at different stages of life; (2) changes in redox-sensitive signaling controlled by levels of oxidative stress and redox state could play more important roles in pathophysiology than accumulation of oxidative damage; (3) changes in oxidative stress and redox state in different cellular compartments (cytosol, mitochondria, or nucleus) could play different roles in pathophysiology during aging, and their combined effects show more impact on aging than changes in either oxidative stress or redox state alone; and (4) the roles of oxidative stress and redox state could have different pathophysiological consequences in different organs/tissues/cells or pathophysiological conditions. To critically test the role of oxidative stress on aging and investigate changes in redox-sensitive signaling pathways, further study is required.

Human longevity and variation in DNA damage response and repair: study of the contribution of sub-processes using competitive gene-set analysis

DNA-damage response and repair are crucial to maintain genetic stability, and are consequently considered central to aging and longevity. Here, we investigate whether this pathway overall associates to longevity, and whether specific sub-processes are more strongly associated with longevity than others. Data were applied on 592 SNPs from 77 genes involved in nine sub-processes: DNA-damage response, base excision repair (BER), nucleotide excision repair, mismatch repair, non-homologous end-joining, homologous recombinational repair (HRR), RecQ helicase activities (RECQ), telomere functioning and mitochondrial DNA processes. The study population was 1089 long-lived and 736 middle-aged Danes. A self-contained set-based test of all SNPs displayed association with longevity (P-value=9.9 × 10(-5)), supporting that the overall pathway could affect longevity. Investigation of the nine sub-processes using the competitive gene-set analysis by Wang et al indicated that BER, HRR and RECQ associated stronger with longevity than the respective remaining genes of the pathway (P-values=0.004-0.048). For HRR and RECQ, only one gene contributed to the significance, whereas for BER several genes contributed. These associations did, however, generally not pass correction for multiple testing. Still, these findings indicate that, of the entire pathway, variation in BER might influence longevity the most. These modest sized P-values were not replicated in a German sample. This might, though, be due to differences in genotyping procedures and investigated SNPs, potentially inducing differences in the coverage of gene regions. Specifically, five genes were not covered at all in the German data. Therefore, investigations in additional study populations are needed before final conclusion can be drawn.

Age-related decrease in the mitochondrial sirtuin deacetylase Sirt3 expression associated with ROS accumulation in the auditory cortex of the mimetic aging rat model

Age-related dysfunction of the central auditory system, also known as central presbycusis, can affect speech perception and sound localization. Understanding the pathogenesis of central presbycusis will help to develop novel approaches to prevent or treat this disease. In this study, the mechanisms of central presbycusis were investigated using a mimetic aging rat model induced by chronic injection of D-galactose (D-Gal). We showed that malondialdehyde (MDA) levels were increased and manganese superoxide dismutase (SOD2) activity was reduced in the auditory cortex in natural aging and D-Gal-induced mimetic aging rats. Furthermore, mitochondrial DNA (mtDNA) 4834 bp deletion, abnormal ultrastructure and cell apoptosis in the auditory cortex were also found in natural aging and D-Gal mimetic aging rats. Sirt3, a mitochondrial NAD+-dependent deacetylase, has been shown to play a crucial role in controlling cellular reactive oxygen species (ROS) homeostasis. However, the role of Sirt3 in the pathogenesis of age-related central auditory cortex deterioration is still unclear. Here, we showed that decreased Sirt3 expression might be associated with increased SOD2 acetylation, which negatively regulates SOD2 activity. Oxidative stress accumulation was likely the result of low SOD2 activity and a decline in ROS clearance. Our findings indicate that Sirt3 might play an essential role, via the mediation of SOD2, in central presbycusis and that manipulation of Sirt3 expression might provide a new approach to combat aging and oxidative stress-related diseases.

Direct synthesis of 4-organylsulfenyl-7-chloro quinolines and their toxicological and pharmacological activities in Caenorhabditis elegans

We describe herein our results on the synthesis and biological properties in Caenorhabditis elegans of a range of 4-organylsulfenyl-7-chloroquinolines. This class of compounds have been easily synthesized in high yields by direct reaction of 4,7-dichloroquinoline with organylthiols using DMSO as solvent at room temperature under air atmosphere and tolerates a range of substituents in the organylsulfenyl moiety. We have performed a toxicological and pharmacological screening of the synthesized 4-organylsulfenyl-7-chloroquinolines in vivo in C. elegans acutely exposed to these compounds, under per se and stress conditions. Hence, we determined the lethal dose 50% (LD50), in order to choose a nonlethal concentration (10 μM) and verified that at that concentration some of the compounds depicted protective action against the induced damage inflicted by paraquat, a superoxide generator. Two compounds (3c and 3h) reduced the toxicity inflicted by paraquat above survival, reproduction and longevity of the worms, at least in part, by reducing the reactive oxygen species (ROS) generated by the toxicant exposure. Besides, these compounds increased the quantities of superoxide dismutase (SOD-3::GFP) and catalase (CTL-1,2,3::GFP), antioxidant enzymes. We concluded that the protective effects of the compounds observed in this study might have been a hormetic response dependent of the transcriptional factor DAF-16/FOXO, causing a non-lethal oxidative stress that protects against the subsequently damage induced by paraquat.

Do we age because we have mitochondria?

The process of aging remains a great riddle. Production of reactive oxygen species (ROS) by mitochondria is an inevitable by-product of respiration, which has led to a hypothesis proposing the oxidative impairment of mitochondrial components (e.g., mtDNA, proteins, lipids) that initiates a vicious cycle of dysfunctional respiratory complexes producing more ROS, which again impairs function. This does not exclude other processes acting in parallel or targets for ROS action in other organelles than mitochondria. Given that aging is defined as the process leading to death, the role of mitochondria-based impairments in those organ systems responsible for human death (e.g., the cardiovascular system, cerebral dysfunction, and cancer) is described within the context of "garbage" accumulation and increasing insulin resistance, type 2 diabetes, and glycation of proteins. Mitochondrial mass, fusion, and fission are important factors in coping with impaired function. Both biogenesis of mitochondria and their degradation are important regulatory mechanisms stimulated by physical exercise and contribute to healthy aging. The hypothesis of mitochondria-related aging should be revised to account for the limitations of the degradative capacity of the lysosomal system. The processes involved in mitochondria-based impairments are very similar across a large range of organisms. Therefore, studies on model organisms from yeast, fungi, nematodes, flies to vertebrates, and from cells to organisms also add considerably to the understanding of human aging.

Growth hormone alters the glutathione S-transferase and mitochondrial thioredoxin systems in long-living Ames dwarf mice

Ames dwarf mice are deficient in growth hormone (GH), prolactin, and thyroid-stimulating hormone and live significantly longer than their wild-type (WT) siblings. The lack of GH is associated with stress resistance and increased longevity. However, the mechanism underlying GH's actions on cellular stress defense have yet to be elucidated. In this study, WT or Ames dwarf mice were treated with saline or GH (WT saline, Dwarf saline, and Dwarf GH) two times daily for 7 days. The body and liver weights of Ames dwarf mice were significantly increased after 7 days of GH administration. Mitochondrial protein levels of the glutathione S-transferase (GST) isozymes, K1 and M4 (GSTK1 and GSTM4), were significantly higher in dwarf mice (Dwarf saline) when compared with WT mice (WT saline). GH administration downregulated the expression of GSTK1 proteins in dwarf mice. We further investigated GST activity from liver lysates using different substrates. Substrate-specific GST activity (bromosulfophthalein, dichloronitrobenzene, and 4-hydrox-ynonenal) was significantly reduced in GH-treated dwarf mice. In addition, GH treatment attenuated the activity of thioredoxin and glutaredoxin in liver mitochondria of Ames mice. Importantly, GH treatment suppressed Trx2 and TrxR2 mRNA expression. These data indicate that GH has a role in stress resistance by altering the functional capacity of the GST system through the regulation of specific GST family members in long-living Ames dwarf mice. It also affects the regulation of thioredoxin and glutaredoxin, factors that regulate posttranslational modification of proteins and redox balance, thereby further influencing stress resistance.

Aging

Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction.

Mitochondria, oxidative DNA damage, and aging

Protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage is well known to be necessary to longevity. The relevance of mitochondrial DNA (mtDNA) to aging is suggested by the fact that the two most commonly measured forms of mtDNA damage, deletions and the oxidatively induced lesion 8-oxo-dG, increase with age. The rate of increase is species-specific and correlates with maximum lifespan. It is less clear that failure or inadequacies in the protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage are sufficient to explain senescence. DNA containing 8-oxo-dG is repaired by mitochondria, and the high ratio of mitochondrial to nuclear levels of 8-oxo-dG previously reported are now suspected to be due to methodological difficulties. Furthermore, MnSOD -/+ mice incur higher than wild type levels of oxidative damage, but do not display an aging phenotype. Together, these findings suggest that oxidative damage to mitochondria is lower than previously thought, and that higher levels can be tolerated without physiological consequence. A great deal of work remains before it will be known whether mitochondrial oxidative damage is a "clock" which controls the rate of aging. The increased level of 8-oxo-dG seen with age in isolated mitochondria needs explanation. It could be that a subset of cells lose the ability to protect or repair mitochondria, resulting in their incurring disproportionate levels of damage. Such an uneven distribution could exceed the reserve capacity of these cells and have serious physiological consequences. Measurements of damage need to focus more on distribution, both within tissues and within cells. In addition, study must be given to the incidence and repair of other DNA lesions, and to the possibility that repair varies from species to species, tissue to tissue, and young to old.

Thioredoxin, oxidative stress, cancer and aging

The Free Radical or Oxidative Stress Theory of Aging is one of the most popular theories in aging research and has been extensively studied over the past several decades. However, recent evidence using transgenic/knockout mice that overexpress or down-regulate antioxidant enzymes challenge the veracity of this theory since the animals show no increase or decrease in lifespan. These results seriously call into question the role of oxidative damage/stress in the aging process in mammals. Therefore, the theory requires significant modifications if we are to understand the relationship between aging and the regulation of oxidative stress. Our laboratory has been examining the impacts of thioredoxins (Trxs), in the cytosol and mitochondria, on aging and age-related diseases. Our data from mice that are either up-regulating or down-regulating Trx in different cellular compartments, that is, the cytosol or mitochondria, could shed some light on the role of oxidative stress and its pathophysiological effects. The results generated from our lab and others may indicate that: 1) changes in oxidative stress and the redox state in the cytosol, mitochondria or nucleus might play different roles in the aging process; 2) the role of oxidative stress and redox state could have different pathophysiological consequences in different tissues/cells, for example, mitotic vs. post-mitotic; 3) oxidative stress could have different pathophysiological impacts in young and old animals; and 4) the pathophysiological roles of oxidative stress and redox state could be controlled through changes in redox-sensitive signaling, which could have more diverse effects on pathophysiology than the accumulation of oxidative damage to various molecules. To critically test the role of oxidative stress on aging and age-related diseases, further study is required using animal models that regulate oxidative stress levels differently in each cellular compartment, each tissue/organ, and/or at different stages of life (young, middle and old) to change redox sensitive signaling pathways.

ROS in aging Caenorhabditis elegans: damage or signaling?

Many insights into the mechanisms and signaling pathways underlying aging have resulted from research on the nematode Caenorhabditis elegans. In this paper, we discuss the recent findings that emerged using this model organism concerning the role of reactive oxygen species (ROS) in the aging process. The accrual of oxidative stress and damage has been the predominant mechanistic explanation for the process of aging for many years, but reviewing the recent studies in C. elegans calls this theory into question. Thus, it becomes more and more evident that ROS are not merely toxic byproducts of the oxidative metabolism. Rather it seems more likely that tightly controlled concentrations of ROS and fluctuations in redox potential are important mediators of signaling processes. We therefore discuss some theories that explain how redox signaling may be involved in aging and provide some examples of ROS functions and signaling in C. elegans metabolism. To understand the role of ROS and the redox status in physiology, stress response, development, and aging, there is a rising need for accurate and reversible in vivo detection. Therefore, we comment on some methods of ROS and redox detection with emphasis on the implementation of genetically encoded biosensors in C. elegans.

The potential utility of telomere-related markers for cancer diagnosis

The role telomeres and telomerase play in the initiation and progression of human cancers has been extensively evaluated. Telomeres are nucleoprotein complexes comprising the hexanucleotide DNA repeat sequence, TTAGGG and numerous telomere-associated proteins, including the six member Shelterin complex. The main function of the telomere is to stabilize the ends of the chromosomes. However, through multiple mechanisms, telomeres can become dysfunctional, which may drive genomic instability leading to the development of cancer. The majority of human cancers maintain, or actively lengthen, telomeres through up-regulation of the reverse transcriptase telomerase. Because there are significant differences in telomere length and telomerase activity between malignant and non-malignant tissues, many investigations have assessed the potential to utilize these molecular markers for cancer diagnosis. Here, we critically evaluate whether measurements of telomere lengths and telomerase levels may be clinically utilized as diagnostic markers in solid tumours, with emphasis on breast and prostate cancer as representative examples. Future directions focusing on the direct detection of dysfunctional telomeres are explored. New markers for telomere dysfunction may eventually prove clinically useful.

Minimal peroxide exposure of neuronal cells induces multifaceted adaptive responses

Oxidative exposure of cells occurs naturally and may be associated with cellular damage and dysfunction. Protracted low level oxidative exposure can induce accumulated cell disruption, affecting multiple cellular functions. Accumulated oxidative exposure has also been proposed as one of the potential hallmarks of the physiological/pathophysiological aging process. We investigated the multifactorial effects of long-term minimal peroxide exposure upon SH-SY5Y neural cells to understand how they respond to the continued presence of oxidative stressors. We show that minimal protracted oxidative stresses induce complex molecular and physiological alterations in cell functionality. Upon chronic exposure to minimal doses of hydrogen peroxide, SH-SY5Y cells displayed a multifactorial response to the stressor. To fully appreciate the peroxide-mediated cellular effects, we assessed these adaptive effects at the genomic, proteomic and cellular signal processing level. Combined analyses of these multiple levels of investigation revealed a complex cellular adaptive response to the protracted peroxide exposure. This adaptive response involved changes in cytoskeletal structure, energy metabolic shifts towards glycolysis and selective alterations in transmembrane receptor activity. Our analyses of the global responses to chronic stressor exposure, at multiple biological levels, revealed a viable neural phenotype in-part reminiscent of aged or damaged neural tissue. Our paradigm indicates how cellular physiology can subtly change in different contexts and potentially aid the appreciation of stress response adaptations.

Regulation of mRNA translation as a conserved mechanism of longevity control

Appropriate regulation of mRNA translation is essential for growth and survival and the pathways that regulate mRNA translation have been highly conserved throughout eukaryotic evolution. Translation is controlled by a complex set of mechanisms acting at multiple levels, ranging from global protein synthesis to individual mRNAs. Recently, several mutations that perturb regulation of mRNA translation have also been found to increase longevity in three model organisms: the buddingyeast Saccharomyces cerevisiae, the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Many of these translation control factors can be mapped to a single pathway downstream of the nutrient responsive target of rapamycin (TOR) kinase. In this chapter, we will review the data suggesting that mRNA translation is an evolutionarily conserved modifier of longevity and discuss potential mechanisms by which mRNA translation could influence aging and age-associated disease in different species.

Mitochondrial base excision repair assays

The main source of mitochondrial DNA (mtDNA) damage is reactive oxygen species (ROS) generated during normal cellular metabolism. The main mtDNA lesions generated by ROS are base modifications, such as the ubiquitous 8-oxoguanine (8-oxoG) lesion; however, base loss and strand breaks may also occur. Many human diseases are associated with mtDNA mutations and thus maintaining mtDNA integrity is critical. All of these lesions are repaired primarily by the base excision repair (BER) pathway. It is now known that mammalian mitochondria have BER, which, similarly to nuclear BER, is catalyzed by DNA glycosylases, AP endonuclease, DNA polymerase (POLgamma in mitochondria) and DNA ligase. This article outlines procedures for measuring oxidative damage formation and BER in mitochondria, including isolation of mitochondria from tissues and cells, protocols for measuring BER enzyme activities, gene-specific repair assays, chromatographic techniques as well as current optimizations for detecting 8-oxoG lesions in cells by immunofluorescence. Throughout the assay descriptions we will include methodological considerations that may help optimize the assays in terms of resolution and repeatability.

Transcriptional profiling of the age-related response to genotoxic stress points to differential DNA damage response with age

The p53 DNA damage response attenuated with age and we have evaluated downstream factors in the DNA damage response. In old animals p21 protein accumulates in the whole cell fraction but significantly declines in the nucleus, which may alter cell cycle and apoptotic programs in response to DNA damage. We evaluated the transcriptional response to DNA damage in young and old and find 2692 genes are differentially regulated in old compared to young in response to oxidative stress (p<0.005). As anticipated, the transcriptional profile of young mice is consistent with DNA damage induced cell cycle arrest while the profile of old mice is consistent with cell cycle progression in the presence of DNA damage, suggesting the potential for catastrophic accumulation of DNA damage at the replication fork. Unique sets of DNA repair genes are induced in response to damage in old and young, suggesting the types of damage accumulating differs between young and old. The DNA repair genes upregulated in old animals point to accumulation of replication-dependent DNA double strand breaks (DSB). Expression data is consistent with loss of apoptosis following DNA damage in old animals. These data suggest DNA damage responses differ greatly in young and old animals.

Mammary field cancerization: molecular evidence and clinical importance

The term "field cancerization" originally denoted the presence of histologically abnormal tissue/cells surrounding primary tumors of the head and neck. Similar concepts with different and continuously changing definitions have been used for other types of tumors including breast adenocarcinoma, where field cancerization presently denotes the occurrence of molecular alterations in histologically normal tissues surrounding areas of overt cancer. Human mammary tissue morphology lends itself to the proposed concepts of field cancerization, which may include the gradual accumulation of genetic and other aberrations in stationary epithelial cells with intact morphology, or the spread of histologically normal yet genetically aberrant epithelial cells within mammary tissue. In this report, we review published molecular genetic, epigenetic, and gene expressional data in support of field cancerization in human mammary tissues. We then discuss the clinical implications of mammary field cancerization, including its source for potential biomarkers with diagnostic/prognostic potential, and its relationship to surgical margins and disease recurrence. We conclude with a future outlook on further research on mammary field cancerization addressing experimental methods, as well as the development of possible models and integrated approaches to gain a better understanding of the underlying mechanisms with the ultimate goal of developing clinical applications.

Genomic instability demonstrates similarity between DCIS and invasive carcinomas

PURPOSE

To assess telomere DNA content (TC) and the number of sites of allelic imbalance (AI) as a function of breast cancer progression.

EXPERIMENTAL DESIGN

TC and AI were determined in 54 histologically normal tissues, 10 atypical ductal hyperplasias (ADH), 122 in situ ductal carcinomas (DCIS) and 535 invasive carcinomas (Stage I-IIIA).

RESULTS

TC was altered in ADH lesions (20%), DCIS specimens (53%) and invasive carcinomas (51%). The mean number of sites of AI was 0.26 in histologically normal group tissue, increased to 1.00 in ADH, 2.94 in DCIS, and 3.07 in invasive carcinomas. All groups were statistically different from the histologically normal group (P < 0.001 for each); however, there was no difference between DCIS and the invasive groups.

CONCLUSIONS

Genomic instability increases in ADH and plateaus in DCIS without further increase in the invasive carcinomas, supporting the notion that invasive carcinomas evolve from or in parallel with DCIS.

Sun exposure and vitamin D sufficiency

Ultraviolet radiation is a carcinogen that also compromises skin appearance and function. Because the ultraviolet action spectra for DNA damage, skin cancer, and vitamin D(3) photosynthesis are identical and vitamin D is readily available from oral supplements, why has sun protection become controversial? First, the media and, apparently, some researchers are hungry for a new message. Second, the controversy is fueled by a powerful special interest group: the tanning industry. This industry does not target the frail elderly or inner-city ethnic minorities, groups for whom evidence of vitamin D(3) insufficiency is strongest, but rather fair-skinned teenagers and young adults, who are at highest risk of ultraviolet photodamage. Third, evolution does not keep pace with civilization. When nature gave humans the appealing capacity for cutaneous vitamin D(3) photosynthesis, life expectancy was <40 y; long-term photodamage was not a concern; and vitamin D(3) deficiency, with its resulting skeletal abnormalities (rickets), was likely to be fatal in early life. In the 21st century, life expectancy approaches 80 y in developed countries, vitamin D(3) is available at the corner store, and the lifetime risk of skin cancer is 1 in 3 among white Americans. Medical and regulatory groups should avoid poorly reasoned, sensationalistic recommendations regarding unprotected ultraviolet exposure. Instead, they should rigorously explore possible cause-and-effect relations between vitamin D(3) status and specific diseases while advocating the safest possible means of ensuring vitamin D(3) sufficiency.

Cells from long-lived mutant mice exhibit enhanced repair of ultraviolet lesions

Fibroblasts isolated from long-lived hypopituitary dwarf mice are resistant to many cell stresses, including ultraviolet (UV) light and methyl methane sulfonate (MMS), which induce cell death by producing DNA damage. Here we report that cells from Snell dwarf mice recover more rapidly than controls from the inhibition of RNA synthesis induced by UV damage. Recovery of messenger RNA (mRNA) synthesis in particular is more rapid in dwarf cells, suggesting enhanced repair of the actively transcribing genes in dwarf-derived cells. At early time points, there was no difference in the repair of cyclobutane pyrimidine dimers (CPD) or 6-4 photoproducts (6-4PP) in the whole genome, nor was there any significant difference in the repair of UV lesions in specific genes. However, at later time points we found that more lesions had been removed from the genome of dwarf-derived cells. We have also found that cells from dwarf mice express higher levels of the nucleotide excision repair proteins XPC and CSA, suggesting a causal link to enhanced DNA repair. Overall, these data suggest a mechanism for the UV resistance of Snell dwarf-derived fibroblasts that could contribute to the delay of aging and neoplasia in these mice.

Mitochondrial DNA oxidation and manganese superoxide dismutase activity in peripheral blood mononuclear cells from type 2 diabetic patients

AIM

To investigate the balance between parameters of oxidative stress and antioxidant defences in the mitochondria of peripheral blood mononuclear cells (PBMCs) of type 2 diabetic patients with late complications.

METHODS

Ten type 2 diabetic patients with late diabetic complications and 10 age-matched healthy volunteers (controls) were prospectively recruited. Mitochondrial DNA (mtDNA) oxidative damage and mtDNA content were measured as indices of oxidative stress. Manganese superoxide dismutase (MnSOD) activity has been used as an index of mitochondrial antioxidant defence. Mitochondrial respiratory-chain function (cytochrome C oxidase activity) was also assessed.

RESULTS

Mitochondrial DNA (mtDNA) oxidation was significantly higher in the PBMCs of diabetic patients than in control subjects (P<0.0001) and, although mtDNA content was lower in the diabetic group, this was not statistically significant. MnSOD activity was significantly increased in PBMCs of type 2 diabetic patients compared with healthy controls (1366+/-187 versus 686+/-167 U/g of protein; P=0.01), and was related to mtDNA oxidative damage. No differences in mitochondrial respiratory-chain function were found between diabetic patients and controls.

CONCLUSION

PMBCs from type 2 diabetic patients with late diabetic complications exhibit high mtDNA oxidative damage. The degree of mtDNA oxidation was associated with an increase in MnSOD as an adaptive response to oxidative stress. The consequences of mtDNA oxidative damage on PBMC function and the progression of diabetic complications remain to be elucidated.

Genetic susceptibility in pancreatic ductal adenocarcinoma

BACKGROUND

The strongest risk factors for pancreatic adenocarcinoma are tobacco smoking and increasing age. However, only a few smokers or elderly individuals develop the disease and genetic factors are also likely to be important.

METHODS

The literature on genetic factors modifying susceptibility to cancer was reviewed, with particular regard to the interindividual variation that exists in the development of pancreatic adenocarcinoma.

RESULTS

Tobacco-derived carcinogen-metabolizing enzyme gene variants have been the main area of study in stratifying the risk of sporadic pancreatic cancer. Inconsistent results have emerged from the few molecular epidemiological studies performed.

CONCLUSION

There is great scope for further investigation of critical pathways and unidentified genetic influences may be revealed. This may eventually allow the identification of individuals at high risk who might be targeted for screening.

The use of comet assay in measuring DNA damage and repair efficiency in child, adult, and old age populations

In the present study, we used the Comet assay to estimate basal DNA damage in three distinct populations aged 5-10, 40-50, and 60-70 years old. The DNA damage induced by hydrogen peroxide and gamma-irradiation in the lymphocytes of these populations, as well as their repair activity, was also studied. Finally, we measured apoptosis and necrosis after the effect of these agents. Our results indicate that the older population (60-70 years old) showed higher basal levels of DNA damage and was more sensitive to the effects of the DNA-damaging agents than the adult one (40-50 years old), who, in turn, was more sensitive than the younger population (5-10 years old). A decline of the repair efficiency with age to the DNA damage induced by the two agents was also observed. Apoptosis and necrosis were also affected by age.

Reduction in glutathione peroxidase 4 increases life span through increased sensitivity to apoptosis

Glutathione peroxidase 4 (Gpx4) is an antioxidant defense enzyme that plays an important role in detoxification of oxidative damage to membrane lipids. Because oxidative stress is proposed to play a causal role in aging, we compared the life spans of Gpx4 heterozygous knockout mice (Gpx4(+/-) mice) and wild-type mice (WT mice). To our surprise, the median life span of Gpx4(+/-) mice (1029 days) was significantly longer than that of WT mice (963 days) even though the expression of Gpx4 was reduced approximately 50% in all tissues of Gpx4(+/-) mice. Pathological analysis revealed that Gpx4(+/-) mice showed a delayed occurrence of fatal tumor lymphoma and a reduced severity of glomerulonephritis. Compared to WT mice, Gpx4(+/-) mice showed significantly increased sensitivity to oxidative stress-induced apoptosis. Our data indicate that lifelong reduction in Gpx4 increased life span and reduced/retarded age-related pathology most likely through alterations in sensitivity of tissues to apoptosis.

Caloric restriction and genomic stability

Caloric restriction (CR) reduces the incidence and progression of spontaneous and induced tumors in laboratory rodents while increasing mean and maximum life spans. It has been suggested that CR extends longevity and reduces age-related pathologies by reducing the levels of DNA damage and mutations that accumulate with age. This hypothesis is attractive because the integrity of the genome is essential to a cell/organism and because it is supported by observations that both cancer and immunological defects, which increase significantly with age and are delayed by CR, are associated with changes in DNA damage and/or DNA repair. Over the last three decades, numerous laboratories have examined the effects of CR on the integrity of the genome and the ability of cells to repair DNA. The majority of studies performed indicate that the age-related increase in oxidative damage to DNA is significantly reduced by CR. Early studies suggest that CR reduces DNA damage by enhancing DNA repair. With the advent of genomic technology and our increased understanding of specific repair pathways, CR has been shown to have a significant effect on major DNA repair pathways, such as NER, BER and double-strand break repair.

Autophagy, organelles and ageing

As a result of insufficient digestion of oxidatively damaged macromolecules and organelles by autophagy and other degradative systems, long-lived postmitotic cells, such as cardiac myocytes, neurons and retinal pigment epithelial cells, progressively accumulate biological 'garbage' ('waste' materials). The latter include lipofuscin (a non-degradable intralysosomal polymeric substance), defective mitochondria and other organelles, and aberrant proteins, often forming aggregates (aggresomes). An interaction between senescent lipofuscin-loaded lysosomes and mitochondria seems to play a pivotal role in the progress of cellular ageing. Lipofuscin deposition hampers autophagic mitochondrial turnover, promoting the accumulation of senescent mitochondria, which are deficient in ATP production but produce increased amounts of reactive oxygen species. Increased oxidative stress, in turn, further enhances damage to both mitochondria and lysosomes, thus diminishing adaptability, triggering mitochondrial and lysosomal pro-apoptotic pathways, and culminating in cell death.

Oxidative stress, chronic disease, and muscle wasting

Underlying the pathogenesis of chronic disease is the state of oxidative stress. Oxidative stress is an imbalance in oxidant and antioxidant levels. If an overproduction of oxidants overwhelms the antioxidant defenses, oxidative damage of cells, tissues, and organs ensues. In some cases, oxidative stress is assigned a causal role in disease pathogenesis, whereas in others the link is less certain. Along with underlying oxidative stress, chronic disease is often accompanied by muscle wasting. It has been hypothesized that catabolic programs leading to muscle wasting are mediated by oxidative stress. In cases where disease is localized to the muscle, this concept is easy to appreciate. Transmission of oxidative stress from diseased remote organs to skeletal muscle is thought to be mediated by humoral factors such as inflammatory cytokines. This review examines the relationship between oxidative stress, chronic disease, and muscle wasting, and the mechanisms by which oxidative stress acts as a catabolic signal.

Sun protection and Vitamin D: three dimensions of obfuscation

Ultraviolet (UV) radiation is a proven carcinogen, responsible for more than half of all human malignancies. It also compromises skin appearance and function. Since the UV action spectra for DNA damage, skin cancer and Vitamin D(3) (vit D) photosynthesis are identical and vit D is readily available from oral supplements, why has sun protection become controversial, now that some data suggest conventionally "sufficient" levels of vit D may be less than optimal for at least some population groups? First, the media and apparently some researchers are hungry for a new message. Nevertheless, after 50 years, UV exposure is still a major avoidable health hazard. Second, the controversy is fueled by a powerful special interest group: the indoor tanning industry. They target not the frail elderly or inner-city ethnic minorities, groups for whom evidence of vit D insufficiency is strongest, but rather fair-skinned teenagers and young adults, those at highest risk of UV photodamage. Third, evolution does not keep pace with civilization. When nature gave man the appealing capacity for vit D photosynthesis, the expected lifespan was far less than 40 years. Long-term photodamage was not a concern, and vit D was not available at the corner store. The medical community should avoid sensationalism and instead rigorously explore possible cause-and-effect relationships between vit D status and specific diseases while advocating the safest possible means of assuring vit D sufficiency.

Telomeres: prognostic markers for solid tumors

Solid tumors continue to affect millions of people worldwide. Increasingly sophisticated diagnostic tools contribute to the high incidence rates for some tumor types, and treatment options continue to expand. However, the progression of solid tumors represents a challenge for the appropriate treatment of individual patients because of the relative inaccuracy of current prognostic markers, including the widely used Tumor-Nodes-Metastasis (TNM) staging system, to predict the course of disease. As a result, both over- and undertreatment are clinical realities in the management of patients diagnosed with solid tumors. Therefore, population-based screening programs that increase the overall cancer incidence rates are controversial, as they may do little to improve the patient's quality of life. Consequently, there is a strong need to develop novel and independent markers of prognosis. In this context, we review the use of telomeres as prognostic markers for solid tumors, including cancers from lung, breast, prostate, colon, brain and head and neck. Telomeric sequences, the repetitive DNA at the end of human chromosomes, are mediators of genomic stability and can undergo length alterations during tumor initiation and progression. In a number of studies reviewed here, these alterations, measured as telomere attrition and elongation, have been shown either to be associated with clinical markers of disease progression or to be independent markers of cancer prognosis. We conclude from these studies that careful assessment of telomere length or its proxies, such as telomere DNA content, will be part of novel risk assessment and prognostic modalities for patients with solid tumors.

T-oligos augment UV-induced protective responses in human skin

We have shown that DNA oligonucleotides substantially homologous to the telomere 3-prime overhang sequence (T-oligos) increase DNA repair capacity (DRC) in cultured human cells and decrease UV-induced mutation rate and photocarcinogenesis in mouse skin. To investigate the protective effects of T-oligos in intact human skin, paired skin explants obtained from adult donors were treated with T-oligos or diluent alone for 24 h, then UVB- or sham-irradiated, and processed after 6, 24, 48, 72, and 96 h for histological analysis. After UV irradiation apoptotic epidermal cells were comparable in diluent- and T-oligo-treated skin. Proliferating (Ki67+) cells were sparse in sham-irradiated skin and for 24 h after UV in both diluent- and T-oligo-treated specimens. However, compared to diluent controls, at 48 and 72 h T-oligos significantly inhibited UV-induced rebound hyperproliferation. Maximum and comparable cyclobutane pyrimidine dimers (CPDs) were detected immediately after UV irradiation in diluent- and T-oligo-treated skin, but CPDs were strikingly reduced in T-oligo- vs. diluent-treated skin at 24, 48, and 72 h. Total and activated p53 protein was increased in T-oligo- vs. diluent-pretreated skin at the time of irradiation, and up to 3-fold increases persisted for 24 h post-UV. Over 5 days, UV irradiation and T-oligo comparably increased expression of melanogenic proteins and each increased epidermal melanin content 3- to 5-fold, with distinct nuclear capping in many keratinocytes. In combination, these findings predict that T-oligo treatment will increase melanogenesis, prolong epidermal arrest, and increase DNA repair rate after UV irradiation, thus decreasing the severity of acute and chronic photodamage in human skin. Moreover, the data document an inducible SOS-like response consisting of increased melanogenesis and increased DNA repair capacity in human skin following UV-induced damage that is also produced by T-oligos in the absence of initial damage.

Age-related loss of the DNA repair response following exposure to oxidative stress

Young (4- to 6-month-old) and aged (24- to 28-month-old) mice were exposed to 2-nitropropane (2-NP), a DNA oxidizing agent, and the ability to induce DNA polymerase beta (beta-pol) and AP endonuclease (APE) was determined. In contrast to the inducibility of these gene products in response to oxidative damage in young mice, aged mice showed a lack of inducibility of beta-pol and APE. APE protein level and endonuclease activity were both reduced 40% (p<.01) in response to 2-NP. Accordingly, the accumulation of DNA repair intermediates in response to 2-NP differed with age. Young animals accumulated 3'OH-containing DNA strand breaks, whereas the aged animals did not. A role for p53 in the difference in DNA damage response with age is suggested by the observation that the accumulation of p53 protein in response to DNA damage in young animals was absent in the aged animals. Our results are consistent with a reduced ability to process DNA damage with age.

Telomere DNA content and allelic imbalance demonstrate field cancerization in histologically normal tissue adjacent to breast tumors

Cancer arises from an accumulation of mutations that promote the selection of cells with progressively malignant phenotypes. Previous studies have shown that genomic instability, a hallmark of cancer cells, is a driving force in this process. In the present study, two markers of genomic instability, telomere DNA content and allelic imbalance, were examined in two independent cohorts of mammary carcinomas. Altered telomeres and unbalanced allelic loci were present in both tumors and surrounding histologically normal tissues at distances at least 1 cm from the visible tumor margins. Although the extent of these genetic changes decreases as a function of the distance from the visible tumor margin, unbalanced loci are conserved between the surrounding tissues and the tumors, implying cellular clonal evolution. Our results are in agreement with the concepts of "field cancerization" and "cancer field effect," concepts that were previously introduced to describe areas within tissues consisting of histologically normal, yet genetically aberrant, cells that represent fertile grounds for tumorigenesis. The finding that genomic instability occurs in fields of histologically normal tissues surrounding the tumor is of clinical importance, as it has implications for the definition of appropriate tumor margins and the assessment of recurrence risk factors in the context of breast-sparing surgery.