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Results for “Genomic instability”

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PubMed1998

Detection of genomic instability in lung cancer tissues by random amplified polymorphic DNA analysis.

Genomic instability resulting in multiple mutations is believed to be a driving force in the carcinogenic process. In this study, the random amplified polymorphic DNA (RAPD) technique, a simple PCR-based DNA polymorphism assay system, was used for detecting genomic instability in lung cancer tissues. DNAs from 20 lung cancer (18 non-small cell lung cancers and two small cell lung cancers) and their corresponding normal tissues were amplified individually by RAPD with seven different 10-base arbitrary primers. PCR products from RAPD were electrophoretically separated in agarose gels and banding profiles were visualized by ethidium bromide staining. The ability to detect genomic instability in 20 cancer tissues by each single primer ranged from 15 to 75%. DNA changes were detected by at least one primer in 19 (95%) cancer tissues. These results seem to indicate that genomic rearrangement is associated with lung carcinogenesis and that RAPD analysis is useful for the detection of genomic instability in lung cancer tissues.

Biopsy↗
PubMed1997

Ovarian cancer genomic instability correlates with p53 frameshift mutations.

We hypothesize that genomic instability plays an important role in causing specific types of p53 mutations in ovarian cancer. To test this hypothesis, 78 tumors were analyzed for p53 mutations with SSCP analysis of the entire open reading frame. At the same time, alterations in 10 microsatellite loci including di-, tri-, and tetranucleotide repeats were evaluated. Fourteen (26%) of all mutations were insertion/deletion mutations. All insertion/deletion mutations were associated with one of the following features: runs of purines or pyrimidines, repeats of short sequences, or palindromes. There was a strong association of generalized microsatellite instability with p53 in contrast to tumors with other types of mutations or wild-type p53 (P = 0.007). These characteristic p53 mutations appear to be caused by generalized genomic instability rather than to be the direct cause of genomic instability. These findings suggest the existence of additional novel DNA repair genes important to the carcinogenic process.

Carcinoma↗
PubMed2025

Human Placental Genomic Instability Predicts Adverse Pregnancy Outcomes.

Preeclampsia is a leading cause of pregnancy-related death, accounting for over 50,000 maternal and 500,000 fetal deaths worldwide each year1-4. Preeclampsia has been linked to confined placental mosaicism, which underscores a potential role of placental genomic instability in driving adverse pregnancy outcomes. Here, using bulk RNA sequencing from 59 preeclamptic and 53 normotensive pregnancies, we explored somatic genomic instability and hypoxia with respect to clinical maternal-placental-neonatal outcomes. We found that genomic instability increased the probability of delivering at an earlier gestational age with a diagnosis of preeclampsia, maternal vascular malperfusion placental lesions, and small for gestational age neonates. Notably, genomic instability and hypoxia are predictive biomarkers for all three adverse pregnancy outcomes. In an induced pluripotent stem cell-derived trophoblast stem cell model, we observed increased genomic instability in trophoblast stem cells obtained from placentas demonstrating maternal vascular malperfusion with preeclampsia. Additionally, increased genomic instability correlated with reduced extravillous trophoblast invasion, implicating a functional role for genomic instability. These findings provide promising insights into the underlying mechanisms of genomic instability in the placenta which may be useful biomarkers for early clinical diagnosis of placental injury underlying preeclampsia.

Journal Article↗
PubMedDate not supplied

[The redox homeostasis system in radiation-induced genomic instability].

The participation of the redox homeostasis system in the formation of the radiation-induced genome instability and new data of literature, that give a direct evidence the presence of this instability in vivo, is considered. The O2.-, H2O2 and NO. role as signal molecules, that triggered the cascade of active responses to change of redox status of the cells, are discussed. These compounds are mediators, that triggered the expression of specific genes. The reactive oxygen species (ROS) reorganize the membrane physico-chemical system of cell metabolism regulation. The composition, structure and function of cell membranes are changed, the membrane-bound proteins are modified. The data about changes in ROS generation system, including NO, that lead to genome instability after ionizing irradiation even in low doses, are analyzed. It is noted, that the radiation-induced genome instability and ROS production increase may be observed both in direct irradiated cells and their progeny and in the cells, that are not find oneself in ionization tracks, and their progeny. There are evidences that the genome instability of irradiated cell progeny is maintained by the increased ROS production. One of the mechanisms of genome instability transduction is carried out over "bystander effect", triggered by ROS.

Animals↗
PubMed2004

Disruption of beta-catenin pathway or genomic instability define two distinct categories of liver cancer in transgenic mice.

BACKGROUND & AIMS: Human liver cancer can be divided into 2 categories that are characterized by activation of beta-catenin and genomic instability. Here we investigate whether similar categories exist among 5 transgenic models of liver cancer, including c-myc, transforming growth factor-alpha, E2F-1, c-myc/transforming growth factor-alpha, and c-myc/E2F-1 mice. METHODS: The random amplified polymorphic DNA method was used to assess the overall genomic instability, and chromosomal loci affected by genomic alterations were determined by microsatellite analysis. beta-Catenin mutations and deletions were analyzed by polymerase chain reaction and sequencing screening. Cellular localization of beta-catenin and expression of alpha-fetoprotein, a prognostic marker of hepatocellular carcinoma, were investigated by immunohistochemistry. RESULTS: Liver tumors from the transgenic mice could be divided into 2 broad categories characterized by extensive genomic instability (exemplified by the c-myc/transforming growth factor-alpha mouse) and activation of beta-catenin (exemplified by the c-myc/E2F-1 mouse). The c-myc/transforming growth factor-alpha tumors displayed extensive genomic instability with recurrent loss of heterozygosity at chromosomes 1, 2, 4, 6, 7, 9, 12, 14, and X and a low rate of beta-catenin activation. The genomic instability was evident from the early dysplastic stage and occurred concomitantly with increased expression of alpha-fetoprotein. The c-myc/E2F-1 tumors were characterized by a high frequency of beta-catenin activation in the presence of a relatively stable genome and low alpha-fetoprotein levels. CONCLUSIONS: We have identified 2 prototype experimental models, i.e., c-myc/transforming growth factor-alpha and c-myc/E2F-1 mice, for the 2 categories of human hepatocellular carcinoma characterized by genomic instability and beta-catenin activation, respectively. These mouse models will assist in the elucidation of the molecular basis of human hepatocellular carcinoma.

Animals↗
PubMed2006

Indirect mechanisms of genomic instability and the biological significance of mutations at tandem repeat loci.

Radiation induction of genomic instability has two features: induction of untargeted mutation and delayed mutation. These phenomena have been studied mostly in tissue culture cells, but analyses have also been conducted in whole body systems. The study of response in whole body systems frequently applies repeat sequences as markers to detect mutations. These studies have generated conflicting findings. In addition, lack of knowledge of the mechanisms involved in repeat mutation confounds the interpretation of the biological significance of increased rates of repeat mutation. In this review, some of the existing controversies of genomic instability are discussed in relation to the mechanism of repeat mutation. Analyses of published and unpublished studies indicate a mechanistic similarity between radiation-induced genomic instability at repeat loci and dynamic mutations of triplet repeats. Because of their repetitive nature, repeat sequences frequently block progression of replication forks and are consequently resolved by slippage and/or recombination. Irradiation of cells induces S checkpoints and promotes slippage/recombination mediated repeat mutations. Thus, genomic instability at repeat loci might be viewed as a consequence of cellular attempts to restore the stability of replication in the face of the stalled replication fork; this process can occur both spontaneously as well as after exposure to radiation.

Animals↗
PubMed1989

Increased incidence of CAD gene amplification in tumorigenic rat lines as an indicator of genomic instability of neoplastic cells.

It has been hypothesized that genomic instability is an important component of tumorigenesis. In an attempt to establish this relationship, we determined the frequencies with which two nontumorigenic and four tumorigenic rat liver epithelial cell lines underwent a particular type of genetic instability, gene amplification. By exposing cells to N-(phosphonoacetyl)-L-aspartate (PALA), a drug which specifically inhibits the aspartate transcarbamylase activity of the multifunctional CAD enzyme and selects for amplification of the CAD gene, we observed a striking parallel between the ability of these cell lines to become resistant to this drug and the ability of these same cells to form tumors after injection into day-old syngeneic rats. Cells of one highly tumorigenic line became resistant to PALA greater than 70 times more often than those of a non-tumorigenic line. Molecular analyses of eight independent PALA-resistant subclones confirmed that, in each case, this resistance was due to amplification of the CAD gene. Thus, our results demonstrate the relationship between tumorigenicity and at least one measure of genomic instability, CAD gene amplification. The method developed in this study provides a quantitative, rapid indicator of tumorigenicity and should prove useful in trying to elucidate the underlying basis of genomic instability in neoplastic cells.

Animals↗
PubMed2005

Oxidative DNA damage causes mitochondrial genomic instability in Saccharomyces cerevisiae.

Mitochondria contain their own genome, the integrity of which is required for normal cellular energy metabolism. Reactive oxygen species (ROS) produced by normal mitochondrial respiration can damage cellular macromolecules, including mitochondrial DNA (mtDNA), and have been implicated in degenerative diseases, cancer, and aging. We developed strategies to elevate mitochondrial oxidative stress by exposure to antimycin and H(2)O(2) or utilizing mutants lacking mitochondrial superoxide dismutase (sod2Delta). Experiments were conducted with strains compromised in mitochondrial base excision repair (ntg1Delta) and oxidative damage resistance (pif1Delta) in order to delineate the relationship between these pathways. We observed enhanced ROS production, resulting in a direct increase in oxidative mtDNA damage and mutagenesis. Repair-deficient mutants exposed to oxidative stress conditions exhibited profound genomic instability. Elimination of Ntg1p and Pif1p resulted in a synergistic corruption of respiratory competency upon exposure to antimycin and H(2)O(2). Mitochondrial genomic integrity was substantially compromised in ntg1Delta pif1Delta sod2Delta strains, since these cells exhibit a total loss of mtDNA. A stable respiration-defective strain, possessing a normal complement of mtDNA damage resistance pathways, exhibited a complete loss of mtDNA upon exposure to antimycin and H(2)O(2). This loss was preventable by Sod2p overexpression. These results provide direct evidence that oxidative mtDNA damage can be a major contributor to mitochondrial genomic instability and demonstrate cooperation of Ntg1p and Pif1p to resist the introduction of lesions into the mitochondrial genome.

Antimycin A↗
PubMed2000

Coming of age: 'dysgenetics'--a theory connecting induction of persistent delayed genomic instability with disturbed cellular ageing.

INTRODUCTION: In recent years a new phenomenon has manifested itself: delayed, persistent genomic instability. When cells are treated with carcinogens not only direct induction of chromosome aberrations and mutations takes place, but there is also an indirect induction: in the distant progeny of treated cells persistently enhanced levels of new chromosome aberrations and enhanced mutation rates are found. This persistent enhanced genomic instability is not due to the presence of lesions in the DNA induced by the treatment because the response can be transmitted to untreated cells. Apparently it is caused by a persistent dysfunctioning of the cell as a whole. Due to these findings a new model for multistep carcinogenesis emerges. According to this model the initiation of carcinogenesis is the induction of a state of persistent genomic instability that not only is responsible for enhanced mutation rates of oncogenes and tumor suppressor genes, but also predisposes to immortalization. This view could lead to a radical change in our views on carcinogenesis. Therefore understanding the mechanism is of utmost importance. PURPOSE: Up to now, the mechanism responsible for this persistent delayed genomic instability remains completely elusive and has only been described as 'unknown'. In this review the phenomenon is connected with a recent theory on cellular ageing and immortalization. CONCLUSION: Although highly speculative this review provides a framework for further experimental approaches that will contribute to our understanding of delayed genomic instability and possibly even to a better understanding of cellular ageing also.

Animals↗
PubMed2003

Genomic instability--the engine of tumorigenesis?

Human cancers harbour numerous mutations and it has been proposed that these result from some form of inherent genomic instability. Some cancers have proven genomic instability or features that are indicative of this. Inherited cancer syndromes exist that are caused by deficient DNA repair or chromosomal integrity. By contrast, theoretical analysis and experimental data from sporadic colorectal tumours provide little general evidence of genomic instability in early lesions. These apparently conflicting data raise the question of whether or not genomic instability is necessary for driving tumour growth, and whether or not it is the usual initiating event in tumorigenesis.

Cell Transformation, Neoplastic↗
PubMed2003

Characterization of sporadic colon cancer by patterns of genomic instability.

Colorectal cancer (CRC) can progress through two pathways of genomic instability: chromosomal (CIN) and microsatellite instability (MSI). We hypothesized that these two pathways are not always independent and that some tumors therefore show a significant degree of overlap between these two mechanisms. We classified 209 high-risk stage II and stage III sporadic CRCs based on their MSI status, using a National Cancer Institute-recommended panel of microsatellite markers, and also identified MSI-associated mutations of CRC target genes such as TGFbetaRII. Evidence for CIN was gathered by identifying loss of heterozygosity (LOH) events on chromosomal arms 1p, 2p, 3p, 5q, 17p, and 18q, which are regions harboring mismatch-repair and tumor-suppressor genes that are significant in CRC development. Results of all molecular markers tested were correlated with clinicopathological variables of the cohort, including treatment outcome. Of the 209 cases, 65% cancers were microsatellite stable, 21% were MSI-low, and 14% were MSI-high (MSI-H). Overall, 51% of the tumors had at least one LOH event, with most frequent chromosomal losses observed on 18q (72.5%), followed by 5q (22%), 17p (21%), and 3p (14%). Interestingly, we observed a significant degree of overlap between MSI and CIN pathways. Of 107 cancers with LOH events, 7 (6.5%) were also MSI-H, and of 30 cancers that were MSI-H, 7 (23.3%) also had one or more LOH events. We also found that 37.8% of microsatellite-stable cancers had no LOH events identified, thus comprising a subgroup of tumors that were not representative of either of these two pathways of genomic instability. Our data suggest that molecular mechanisms of genomic instability are not necessarily independent and may not be fully defined by either the MSI or CIN pathways.

Aged↗
PubMed2002

Suppression of genome instability by redundant S-phase checkpoint pathways in Saccharomyces cerevisiae.

Cancer cells show increased genome rearrangements, although it is unclear what defects cause these rearrangements. Previous studies have implicated the Saccharomyces cerevisiae replication checkpoint in the suppression of spontaneous genome rearrangements. In the present study, low doses of methyl methane sulfonate that activate the intra-S checkpoint but not the G1 or G2 DNA damage checkpoints were found to cause increased accumulation of genome rearrangements in both wild-type strains and to an even greater extent in strains containing mutations causing defects in the intra-S checkpoint. The rearrangements were primarily translocations or events resulting in deletion of a portion of a chromosome arm along with the addition of a new telomere. Combinations of mutations causing individual defects in the RAD24 or SGS1 branches of the intra-S checkpoint or the replication checkpoint showed synergistic interactions with regard to the spontaneous genome instability rate. PDS1 and the RAD50-MRE11-XRS2 complex were found to be important members of all the S-phase checkpoints in suppressing genome instability, whereas RAD53 only seemed to play a role in the intra-S checkpoints. Combinations of mutations that seem to result in inactivation of the S-phase checkpoints and critical effectors resulted in as much as 12,000-14,000-fold increases in the genome instability rate. These data support the view that spontaneous genome rearrangements result from DNA replication errors and indicate that there is a high degree of redundancy among the checkpoints that act in S phase to suppress such genome instability.

DNA-Binding Proteins↗
PubMed2005

Genomic instability in human lymphocytes irradiated with individual charged particles: involvement of tumor necrosis factor alpha in irradiated cells but not bystander cells.

Exposure to ionizing radiation can increase the risk of cancer, which is often characterized by genomic instability. In environmental exposures to high-LET radiation (e.g. 222Ra), it is unlikely that many cells will be traversed or that any cell will be traversed by more than one alpha particle, resulting in an in vivo bystander situation, potentially involving inflammation. Here primary human lymphocytes were irradiated with precise numbers of 3He2+ ions delivered to defined cell population fractions, to as low as a single cell being traversed, resembling in vivo conditions. Also, we assessed the contribution to genomic instability of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFA). Genomic instability was significantly elevated in irradiated groups (> or = two-fold over controls) and was comparable whether cells were traversed by one or two 3He2+ ions. Interestingly, substantial heterogeneity in genomic instability between experiments was observed when only one cell was traversed. Genomic instability was significantly reduced (60%) in cultures in which all cells were irradiated in the presence of TNFA antibody, but not when fractions were irradiated under the same conditions, suggesting that TNFA may have a role in the initiation of genomic instability in irradiated cells but not bystander cells. These results have implications for low-dose exposure risks and cancer.

Bystander Effect↗
PubMedDate not supplied

Impact of genome instability on transcription regulation of aging and senescence.

Genomic instability has been implicated as a major stochastic mechanism of aging. Using a transgenic mouse model with chromosomally integrated lacZ mutational target genes, mutations were found to accumulate with age at an organ- and tissue-specific rate. Also, the spectrum of age-accumulated mutations was found to differ greatly from organ-to-organ; while initially similar, mutation spectra of different tissues diverged significantly over the lifetime. To explain how genomic instability, which is inherently stochastic, can be a causal factor in aging, it is proposed that randomly induced mutations may adversely affect normal patterns of gene regulation, resulting in a mosaic of cells at various stages on a trajectory of functional decline, eventually resulting in cell death or neoplastic transformation. To directly address this question, we demonstrate that it is now possible to analyze single cells, isolated from old and young tissues, for specific alterations in gene expression.

Aging↗
PubMedDate not supplied

[Radiation-induced genomic instability: phenomenon, molecular mechanisms, pathogenetic significance].

The recent data on the radiation-induced genome instability as a special state of progeny of cells irradiated in vitro as well as after a whole body exposure to ionizing radiation, that make these cells considerably different from normal, unirradiated cells, were considered. This state presents a number of cytogenetical, molecular-biological, cytological and biochemical manifestations untypical for normal cells. The state is controlled by the mechanisms of regulation of checkpoints of cell cycle, and apoptosis, that is under gene p53 control. The proof has been found that this state transfers from irradiated maternal cells to their surviving progeny by the epigenetical mechanisms and would exist until the cells restore the original state of response on the DNA damage. From the point of view of the genome instability conception, that considers the chromatine rearrangement as the adaptive-evolution mechanism of adaptation of the species to changeable environmental conditions, the radiation-induced genome instability may be considered as transition of irradiated progeny to the state of read these to adaptation changes with two alternative pathways. The first leads to adaptation to enviromental conditions and restoring of normal cell functions. The second presents the cell transition into the transformed state with remain genome instability and with increase of tumour growth probability.

Adaptation, Physiological↗
PubMed2003

Induced genomic instability in irradiated germ cells and in the offspring; reconciling discrepancies among the human and animal studies.

Many studies confirmed that radiation induces genomic instability in whole-body systems. However, the results of the studies are not always consistent with each other. Attempts are made in the present review to resolve the discrepancies. Many of the studies in human and experimental animals utilize the length change mutation of minisatellite sequences as a marker of genomic instability. Minisatellite sequences frequently change their length, and the data obtained by conventional Southern blotting give rather qualitative information, which is sometimes difficult to scrutinize quantitatively. This is the problem inevitably associated with the study of minisatellite mutations and the source of some conflicts among studies in humans and mice. Radiation induction of genomic instability has also been assessed in whole-body experimental systems, using other markers such as the mouse pink-eyed unstable allele and the specific pigmentation loci of medaka fish (Oryzias latipes). Even though there are some contradictions, all these studies have demonstrated that genomic instability is induced in the germ cells of irradiated parents, especially of males, and in offspring born to them. Among these, transmission of genomic instability to the second generation of irradiated parents is limited to the mouse minisatellite system, and awaits further clarification in other experimental systems.

Animals↗
PubMed2005

Emerging roles of centrosomal amplification and genomic instability in cancer.

The carcinogenic process is multistep in terms of its etiology and multifactor in terms of its evolution. In this context, the temporal accumulation of multiple genetic changes during multistage carcinogenesis that can be mediated at least in part by genomic instability may represent crucial components of tumor cell evolution. Evidence is accumulating indicating a close link between genomic instability and cancer initiation and progression. Neoplastic cells typically possess numerous genomic lesions, which may include sequence alterations (point mutations, small deletions, and insertions) and/or gross structural abnormalities in one or more chromosomes (large-scale deletions, rearrangements, gene amplifications). Furthermore karyotypic alterations, including whole chromosome loss or gain, ploidy changes (aneuploidy and polyploidy) and a variety of chromosome aberrations are common in tumor cells. Genomic instability also involves mitotic defects associated with centrosome abnormalities. However, the question of whether abnormal centrosomes cause genomic instability or develop secondary to other changes has not been conclusively resolved. In this review, the recent studies investigating genomic instability and aneuploidy in human cancer, centrosome amplification and the role of centrosomal duplication in chromosomal mis-segregetion, and genes implicated in regulating chromosome segregation, centrosomal amplification and progression in cancer cells are discussed.

Aneuploidy↗
PubMed1998

Is exposure to environmental or industrial endocrine disrupting estrogen-like chemicals able to cause genomic instability?

Human and wild life populations are continually exposed to a wide variety of environmental estrogen-like chemicals. Most research to date on environmental endocrine disrupting estrogen-like chemicals has focussed on screening of estrogenic activity of environmental or industrial chemicals, their bioaccumulative properties and toxicokinetics, and developing the structure-activity relationship between environmental or industrial chemicals and estrogen-receptor. Whether estrogen-like chemicals also possess the ability to alter the stability of the genome is not clear. It is very important to understand the effects of estrogen-like chemicals at the genome level. This article evaluates the current status of knowledge of the potential of producing genomic instability in response to the exposure of estrogen-like chemicals, which might help in understanding the mechanisms of some of the adverse effects. We and others have shown several structural, numerical, and functional changes at the cellular levels in response to DES exposure. Some other phenolic estrogen-like chemicals, such as, bisphenol A, phenylphenol and nonylphenol, also follow some of the pattern of effects similar to DES. These compounds also alter cell cycle kinetics, induce DNA damages, and produce telomeric associations and chromosomal aberrations. Whether weak or strong, the estrogenic response of a chemical, if not overcome, will add extra estrogenic burden to the system, and particularly those endocrine disrupting environmental and industrial estrogen-like chemicals capable of producing genomic instability will induce additional burden of genomic instability. Though, estrogenically some of these compounds may be weak, however, they may have different activities in generation of genomic instability. For example, nonylphenol is weak in estrogen-like action compared to DES, however, it is equal or more potent in producing telomeric associations in MCF-7 cells compared to DES. Additive or synergistic extra-burden of estrogenicity and genomic instability could produce detrimental effects compare to estrogenic action alone. Screening of endocrine disrupting environmental estrogen-like chemicals for their ability to produce genomic instability and analysis of molecular basis of some of the adverse human health outcomes as a result of exposure of these types of chemicals should lead to a better understanding of how these environmental estrogen-like chemicals may influence the development of some adverse effects in humans and wildlife.

Animals↗