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At least 793 records · Page 44Linked to original sources
PubMed2005

AID binds to transcription-induced structures in c-MYC that map to regions associated with translocation and hypermutation.

Translocation and aberrant hypermutation of c-MYC are common in B-cell lymphomas. Activation-induced Cytidine Deaminase (AID) initiates switch recombination and somatic hypermutation in B cells by targeted deamination of transcribed genes. We show that transcription of the immunoglobulin S regions and c-MYC results in formation of similar DNA structures, 'G-loops', which contain a cotranscriptional RNA: DNA hybrid on the C-rich strand and single-stranded regions and G4 DNA on the G-rich strand. AID binds specifically to G-loops within transcribed S regions and c-MYC, and G-loops in c-MYC map to the regions associated with translocation breakpoints and aberrant hypermutation in B-cell lymphomas. Aberrant targeting of AID to DNA structures formed upon c-MYC transcription may therefore contribute to the genetic instability of c-MYC in B-cell malignancies.

Animals↗
PubMed2007

A girl with neurofibromatosis type 1, atypical autism and mosaic ring chromosome 17.

We describe a girl with neurofibromatosis type 1 (NF1), mild dysmorphic features, growth and mental retardation, autism, and mosaicism of ring chromosome 17 and chromosome 17 monosomy. The extent of genetic material deleted from the ring chromosome was determined using a combination of classical cytogenetics, fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) to be 0.6-2.5 Mb on 17p, and up to about 10 Mb on 17q. Based on our observations and on a review of the literature we argue that in addition to a universal "ring syndrome" which is based on ring instability and is less specific for the chromosome involved, various ring chromosomes underlie their own characteristic phenotypes. We propose that the symptoms leading to the diagnosis of NF1 in our patient could be attributed to mosaic hemizygosity for the NF1 gene in some of her somatic cells. A similar mechanism or a direct involvement of respective disease genes in the aberration could possibly influence also the development of autism and other symptoms. We raise a question if the loss of one copy of chromosome 17 from a substantial fraction of somatic cells can have specific consequences also for future risks of the patient, for example, due to the mosaic hemizygosity for the BRCA1 and TP53 genes.

Autistic Disorder↗
PubMed2003

Mutation-selection networks of cancer initiation: tumor suppressor genes and chromosomal instability.

In this paper, we derive analytic solutions of stochastic mutation-selection networks that describe early events of cancer formation. A main assumption is that cancer is initiated in tissue compartments, where only a relatively small number of cells are at risk of mutating into cells that escape from homeostatic regulation. In this case, the evolutionary dynamics can be approximated by a low-dimensional stochastic process with a linear Kolmogorov forward equation that can be solved analytically. Most of the time, the cell population is homogeneous with respect to relevant mutations. Occasionally, such homogeneous states are connected by 'stochastic tunnels'. We give a precise analysis of the existence of tunnels and calculate the rate of tunneling. Finally, we calculate the conditions for chromosomal instability (CIN) to precede inactivation of the first tumor suppressor gene. In this case, CIN is an early event and a driving force of cancer progression. The techniques developed in this paper can be used to study arbitrarily complex mutation-selection networks of the somatic evolution of cancer.

Cell Physiological Phenomena↗
PubMed2001

Telomerase activity modulation in the prevention of prostate cancer.

Telomerase is a ribonucleoprotein that stabilizes chromosomes by maintaining their telomeric ends. Although telomerase is normally expressed in reproductive tissues, it is virtually absent in most normal somatic tissues. During carcinogenesis, cells activate telomerase to protect chromosomal ends from the telomere erosion that occurs with replication. Prevention of telomere loss by activation of telomerase allows for the cellular immortalization that is a characteristic of cancer cells. Recent studies have shown that genetic instability arising from critical telomere shortening is a mechanism through which cancer cells attain multiple genetic aberrations that characterize a malignant clone. Thus, the timing of telomerase activation during carcinogenesis is likely to play an important role in modulating the genetic instability that determines the malignant phenotype. Earlier activation of telomerase should minimize genetic aberrations in neoplastic cells and lead to less aggressive tumors, or may prevent carcinogenesis. In this article, we discuss recent data on telomerase expression in prostate cancer, propose a model that relates the dynamics of telomerase activation to the evolution of different prostatic malignancies, and discuss the potential application of telomerase activation as a strategy for the prevention of prostate cancer.

Cell Transformation, Neoplastic↗
PubMed1997

Optimal foetal growth in the reduction of learning and behaviour disorder and prevention of sudden infant death (SIDS) after the first month.

A theory is presented that a diet low in polyunsaturated fatty acids (PUFA) in the third trimester of pregnancy may delay myelination and brain maturation. This may underpin learning and behaviour disorders and sudden infant death (SIDS) after the first month, conditions that are associated with lower than average birthweight. Epidemiological evidence is reviewed showing an inverse relation between the proportion of heavy newborns (> 3500 g) and infant mortality rate. Some countries with a lower proportion of heavy newborns despite equally high standards of living and medical care have higher post-neonatal death rates. The higher rates are solely due to SIDS which has a peak mortality within 80-100 days. It is hypothesised that as this is a time when myelination peaks, SIDS may be due to maturational delay. Evidence of subtle CNS changes in brainstem structures and in the neuromuscular system supports an instability in brainstem control systems. Moderate iatrogenic dietary restriction predominates today, but a rising number of women favour a low-caloric low-fat diet especially in the third trimester when the foetus is most susceptible. This may lead to a depressed birthweight, delayed somatic growth and neuronal maturation, such as is observed in SIDS victims. The majority exposed to suboptimal conditions survive, but a few suffer SIDS; confirming post-neonatal susceptibility. Many, especially males, present minor CNS signs and learning/behaviour disorders that could be the sequelae of repeated hypoxic episodes, such as recorded in more than 80% of SIDS victims. To reduce learning/behaviour disorders and prevent death from SIDS after the first month, it is necessary to ensure optimal development by promoting foetal growth. It is advised to avoid unnecessary dieting and to favour a diet high in PUFAs, thus prolonging pregnancy and so increasing birthweight.

Birth Weight↗
PubMed1999

Genomic imprinting and position-effect variegation in Drosophila melanogaster.

Genomic imprinting is a phenomenon in which the expression of a gene or chromosomal region depends on the sex of the individual transmitting it. The term imprinting was first coined to describe parent-specific chromosome behavior in the dipteran insect Sciara and has since been described in many organisms, including other insects, plants, fish, and mammals. In this article we describe a mini-X chromosome in Drosophila melanogaster that shows genomic imprinting of at least three closely linked genes. The imprinting of these genes is observed as mosaic silencing when the genes are transmitted by the male parent, in contrast to essentially wild-type expression when the same genes are maternally transmitted. We show that the imprint is due to the sex of the parent rather than to a conventional maternal effect, differential mitotic instability of the mini-X chromosome, or an allele-specific effect. Finally, we have examined the effects of classical modifiers of position-effect variegation on the maintenance and the establishment of the imprint. Factors that modify position-effect variegation alter the somatic expression but not the establishment of the imprint. This suggests that chromatin structure is important in maintenance of the imprint, but a separate mechanism may be responsible for its initiation.

Alleles↗
PubMed2000

Involvement of PTEN mutations in the genetic pathways of colorectal cancerogenesis.

So far, somatic mutations of the PTEN gene have been found in several different neoplasms but not in colorectal tumours. As exons 7 and 8 of the PTEN coding sequence contain an (A)(6)repeat and mononucleotide repeat sequences are targets for mutations in tumours with microsatellite instability (MI), we screened a panel of sporadic colorectal tumours exhibiting MI to test whether PTEN gene repeats are frequently mutated in MI(+)colorectal cancers. Of 32 cases studied, seven mutations were found in six (18.75%) patients, as a PTEN biallelic frameshift mutation was observed in one case, with consequent loss of function of the gene. Loss of heterozygosity, evaluated in the remaining five cases using the microsatellite marker D10S541, was detected in two of three informative samples. To further address the role of the PTEN gene in MI(+)colorectal cancer, in the six patients with mutated PTEN, we analysed the mononucleotide repeats of six other genes: BAX, hMSH3, hMSH6, TGFbRII, IGFIIR and APC. In two of these six patients, mutations of the TGFbRII gene only were present, indicating that PTEN may have a role in the mutator pathway of colorectal tumorigenesis. Overall, these results indicate that PTEN mutations are selected for during tumorigenesis in MI(+)colorectal tumours. The mutation of both PTEN alleles and evidence that the PTEN protein is expressed in normal colon suggest that loss of function of this gene could play a direct role in tumorigenesis.

Colorectal Neoplasms↗
PubMed1987

Interactions of aging and environmental agents: the gerontological perspective.

This article attempts to briefly review the current status of knowledge of biogerontology as a basis for a beginning set of discussions on the potential roles of environmental agents in the modulation of rates of aging in man. The article has tried to summarize "what the toxicologist should know about gerontology," whereas a companion review, by Dr. Jerry Williams, summarizes "what the gerontologist should know about toxicity." The review begins by defining some basic terminology, including introduction of the term "gerontogens" for those putative environmental agents that may in fact modulate the times of onset and/or rates of development of specific aspects of the senescent phenotype. That phenotype is then briefly described from the level of populations to the level of molecules, including an organ systems approach with emphasis on what is observed in humans. Among the important points that emerge from this description are: the variety of phenotypic alterations; the multiplicity of phenotypic alterations in any one aged individual; the special vulnerability in humans of the arterial system; the loss of proliferative homeostasis; the decline in the efficiency of enzyme adaptation; the decline in protein synthesis; the increasing evidence of post-translational modifications of proteins and DNA; the evidence for chromosomal instability (and, therefore, the potential importance of environmental clastogens). Arguments for a genetic basis for differential rates of aging are then developed, and a number of "genotropic" theories of aging are tabulated (i.e., those theories that invoke crucial roles for alterations of the genomes of somatic cells, whether changes in gene expression, gene structure, or both). It is concluded that no single theory is supported by a preponderance of evidence. Because aging appears to involve numerous processes and is highly polygenic in its determination, it is likely that a number of different mechanisms are responsible for the phenotypic alterations and that different individuals exhibit various patterns of aging based upon their specific inheritance and environmental experiences. At this early stage in the development of experimental approaches to the study of environmental-genetic interactions in the genesis of different aspects of senescence, the most vital issue involves the question of suitable model systems. Clearly, a number of different model systems will be required. A selection of these is tabulated based upon their amenability to a reasonable degree of genetic definition and genetic manipulation. Only by controlling the genotype can the environmental influences be properly assessed.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1995

Failure in expression of structurally altered (CYS164-->TYR) H-2Kb molecules is mitigated with high affinity peptide-ligand.

A C164Y somatic mutation in the H-2Kb class I molecule causes a disruption of the alpha 2 domain disulfide bond and results in a loss of H-2Kb cell surface expression by the 69.9.15 cell line. In vitro culture of the somatic cell variant at 30 degrees C induced weak, but reproducible, expression of the H-2Kb mutant molecule on the cell surface, which suggests that a temperature-sensitive mutation was contributing to the H-2Kb null phenotype. Based on the inherent structural instability of the mutant H-2Kb molecules synthesized by 69.9.15 cells, we sought to determine the ability of high affinity peptide-ligand to counteract the null expression of H-2Kb. Treatment of 69.9.15 cells was performed with acid-eluted cell-derived peptides, as well as synthetic H-2Kb-restricted peptides, ovalbumin (OVA) p257-264 (YSIINFEKL), and vesicular stomatitis virus-nuclear protein p52-59 (RGYVYQGL). Whereas the endogenous and vesicular stomatitis virus peptides were ineffective at inducing H-2Kb expression at either 37 degrees C or 30 degrees C, treatment with the OVA peptide at 30 degrees C gave rise to dose-dependent enhancement in H-2Kb expression, an effect that was independent of exogenous sources of bovine beta 2-microglobulin at the time of peptide treatment. By comparison, expression of H-2Kb remained unaltered when cells were treated with the OVA peptide at 37 degrees C, consistent with the temperature-sensitive expression of the mutant molecules. Decay of H-2Kb from the cell surface was similar for both 69.9.15 and RMA-S cells, an indication that binding of OVA p257-264 provided the same level of stability for class I molecules with either a cis-(69.9.15) or trans-acting (RMA-S) defect in heavy chain transport. These data provide novel evidence that transport-defective MHC class I molecules, similar in nature to those encoded by class I genes isolated from human genomic libraries, i.e., the 12.4 pseudogene with a polymorphism at amino acid position 164 (C-->F), are subject to high affinity peptide-induced stabilization which reverses the class I null phenotype.

Amino Acid Sequence↗
PubMed2006

Bipolar II and anxious reactive "comorbidity": toward better phenotypic characterization suitable for genotyping.

OBJECTIVE: In DSM-IV, bipolar II (BP-II) disorder is defined by depression and hypomania. There is little appreciation of affective instability, often associated with anxiety-particularly panic disorder and agoraphobia (PDA)-comorbidity. This association has genetic-familial implications, which we believe must be incorporated in refining the BP-II phenotype suitable for genotyping purposes. METHOD: We examined in a semi-structured format 107 consecutive patients who met DSM-IV criteria for major depressive episode with atypical features and separated them into two subgroups according to the co-occurring criteria for PDA. They were further evaluated on the basis of the Atypical Depression Diagnostic Scale (ADDS), the Hopkins Symptoms Check-list (HSCL 90), and the Hamilton Rating Scale for Depression (HRSD), coupled with its modified form for reverse vegetative features, as well as Axis I and II comorbidity and temperamental dispositions, particularly cyclothymic instability. RESULTS: Fifty (46.7%) of our patients met the DSM-IV criteria for PDA. In terms of significant results, PDA+ was more frequently female, had higher number of hypomanic episodes, and stressors; they were also more often BP-II, and cyclothymic. Ratings of reactivity, somatization, OCD and phobic anxiety too were significantly higher among the PDA+. In related analyses, most AD (75.7%) met criteria for BP-II; the BP-II subgroup was characterized by PDA, as well as borderline personality features and cyclothymic and hyperthymic temperaments. LIMITATIONS: Correlational clinical study in which clinicians could not be kept entirely blind to the variables under investigation. CONCLUSIONS: In line with the description by the French psychiatrist Pierre Kahn a century earlier, cyclothymic reactivity and neurotic features (i.e., atypicality and panic attacks) appear relevant to the definition of what today we consider BP-II disorder. These data, which are in line with current familial-genetic models of this disorder, suggest that the DSM-IV characterization of BP-II must be enriched by greater emphasis on temperamentally based mood and anxious reactivity. Such phenotypic characterization is likely to assist in better genotyping. Previous work by us further suggests the relevance of bulimic and addictive tendencies, as well as "borderline personality" diagnosis in the proband and/or the family. We submit that these conditions, rather than being "comorbid," constitute, along with BP-II, a spectrum of overlapping underlying genetic diatheses.

Adolescent↗
PubMed1996

Mutations of the transforming growth factor-beta type II receptor gene are strongly related to sporadic proximal colon carcinomas with microsatellite instability.

BACKGROUND: Mutations of the transforming growth factor-beta type II receptor gene (TGF-beta RII) have been found in several replication error-positive sporadic colorectal carcinomas and hereditary nonpolyposis colorectal carcinoma cell lines. The aim of this study was to clarify the role of TGF-beta RII in sporadic colorectal carcinogenesis. METHODS: The authors screened for mutations at simple repeated sequences in the TGF-beta RII gene by polymerase chain reaction-single strand conformation polymorphism. They also examined genomic instability, using five microsatellite DNA markers in 69 sporadic colorectal carcinomas. When the carcinomas exhibited the TGF-beta RII mutations, the authors screened further for mutations in two DNA mismatch repair genes, hMSH2 and hMLH1. RESULTS: Seven of the 69 cancers (10%) showed one or two A deletions in TGF-beta RII and resultant frameshift mutations in nucleotide positions 709-718 containing a (A) 10 repeated sequence; but none of these appeared in the corresponding normal DNA, indicating a somatic mutation. All of the seven cancers were located in the proximal colon; there were none in the distal colon (P < 0.01). On the other hand, 22 of the 69 carcinomas (32%) showed the replication error-positive phenotype. The frequency of replication errors in proximal colon carcinomas was higher than that in distal colon carcinomas (P < 0.05). All 7 cancers with TGF-beta RII mutations showed replication errors. One of them revealed a nonsense mutation at codon 413, and 1 revealed a loss of heterozygosity in hMSH2. CONCLUSIONS: These data indicate that mutations of TGF-beta RII are strongly related to proximal colon carcinomas with microsatellite instability and that the mechanism of carcinogenesis in some proximal colon carcinomas is similar to that in hereditary nonpolyposis colorectal carcinoma.

Aged↗
PubMed2026

Mobile elements in pituitary neuroendocrine tumors: integrative evidence and future directions.

Mobile genetic elements (MGEs), including LINE-1 retrotransposons, Alu and SVA elements, and human endogenous retroviruses (HERVs), constitute nearly half of the human genome and are increasingly understood to influence multiple dimensions of cancer evolution. Yet, pituitary neuroendocrine tumors (PitNETs) remain almost absent from mobilome research, despite exhibiting genomic and epigenetic contexts permissive to retroelement activation. In this review, we synthesize current evidence linking MGEs to PitNET biology and delineate unresolved but testable mechanisms. Structural genomic studies demonstrate that Alu-mediated non-allelic homologous recombination contributes to germline mutagenesis in MEN1 and AIP, reinforcing the notion that repetitive DNA architecture shapes PitNET predisposition. Transcriptomic analyses reveal global derepression of transposable elements and LINE-1 hypomethylation in subsets of tumors, while mechanistic connections to chromatin instability emerge from recurrent ATRX/DAXX deficiency and TP53 inactivation, both established repressors of retroelements. Furthermore, the retrocopy-derived long non-coding RNA RPSAP52 exemplifies how mobilome-origin transcripts can be co-opted as oncogenic regulators in PitNETs, acting through HMGA2-dependent proliferative networks. Preliminary data also suggest endogenous retroviral activation, with consistent upregulation of HERV envelope genes across distinct tumor subtypes. Nevertheless, no study has yet systematically mapped somatic mobile-element insertions (MEIs), quantified LINE-1 protein activity, or profiled HERV expression at locus resolution in PitNETs. Mobilome biology represents a tractable and conceptually rich frontier with diagnostic, prognostic, and therapeutic potential in pituitary tumorigenesis.

Humans↗
PubMed1988

Congenital chromosome breakage clusters within Giemsa-light bands and identifies sites of chromatin instability.

Analysis of the distribution of published chromosome breaks in cells with constitutional chromosome aberrations showed a nonrandom distribution of breaks among chromosomes and chromosome regions. A significant amount of breakage occurred at Giemsa-negative bands. In addition, chromosome sites associated with a number of fragile sites and cellular oncogene sites were affected nonrandomly. The data are consistent with the hypothesis that chromosome breakage occurs in somatic or germ cells as a result of recombinational errors involving actively transcribing chromatin regions or regions of unstable DNA sequence structure placed in proximity during interphase.

Azure Stains↗
PubMed1996

Tumor suppressor activity of the TGF-beta pathway in human cancers.

The TGF-betas are a family of cytokines with antiproliferative activity on many cell types. Recent findings demonstrate that the TGF-beta receptor complex functions as a tumor suppressor gene in human malignancy. Somatic mutations of the type II subunit of the TGF-beta receptor (RII) have been demonstrated in several different tumor types. RII frameshift mutations within a short coding region polyadenine repeat are particularly characteristic of colon and gastric cancers that also demonstrate the phenotype of microsatellite instability (RER cancers). These and other mutations as in the type I receptor (RI) are associated with both loss of cell surface TGF beta receptors and with resistance of the cancer cells to TGF-beta-induced growth inhibition. Restoration of receptor expression by gene transfection reverses the transformed phenotype in cancer cells that lacked functional RII or RI. These receptors and, by implication, TGF-beta as well as its complete signalling pathway, are thus new and novel additions to the family of human tumor suppressor genes.

Cell Division↗
PubMed2005

Common fragile sites.

Common fragile sites are regions showing site-specific gaps and breaks on metaphase chromosomes after partial inhibition of DNA synthesis. Common fragile sites are normally stable in somatic cells. However, following treatment of cultured cells with replication inhibitors, fragile sites display gaps, breaks, rearrangements and other features of unstable DNA. Studies showing that fragile sites and associated genes are frequently deleted or rearranged in many cancer cells have clearly demonstrated their importance in genome instability in cancer. Until recently, little was known about the molecular nature and mechanisms involved in fragile site instability. From studies conducted in many laboratories, it is now known that fragile sites extend over large regions, are associated with genes, exhibit delayed replication, and contain regions of high DNA flexibility. Recent findings from our laboratory showing that the key cell cycle checkpoint genes are important for genome stability at fragile sties have shed new light on these mechanisms and on the significance of these sites in cancer and normal chromosome structure. Since their discovery over two decades ago, much has been learned regarding their significance in chromosome structure and instability in cancer, but a number of key questions remain, including why these sites are 'fragile' and the impact of this instability on associated genes in cancer cells. These and other questions have been addressed by participants of this meeting, which highlighted instability at common fragile sites. This brief review is intended to provide background on common fragile sites that has led up to many of the studies presented in the accompanying reports in this volume and not to summarize the findings presented therein. Some aspects of this review were taken from Glover et al. (T.W. Glover, M.F. Arlt, A.M. Casper, S.G. Durkin, Mechanisms of common fragile site instability, Hum. Molec. Genet. 14 (in press). [1]).

Animals↗
PubMed2003

Combined renin-angiotensin system blockade and dietary sodium restriction impairs cardiomyocyte contractility.

INTRODUCTION: Blockade of the renin-angiotensin system (RAS) by combined angiotensin-converting enzyme inhibitor and angiotensin type 1 receptor (AT(1)) antagonist treatment with reduced dietary sodium intake produces suppression of cardiac growth and regression of cardiac hypertrophy. The purpose of this study was to investigate whether cardiac growth suppression by combined RAS blockade under conditions of dietary sodium restriction is associated with cardiomyocyte atrophy and contractile dysfunction and whether this intervention modifies cardiomyocyte inotropic responsiveness to angiotensin II (Ang II). METHODS: Rats were fed a high (4% w/w) or low (0.2% w/w) NaCl diet for six days. Both groups were then given a combined intraperitoneal injection of perindopril (6 mg/kg/day) and losartan (10 mg/kg/day) with maintained dietary treatment for another seven days. At the end of the treatment period, animals were anaesthetised and their hearts were removed and weighed. Left ventricular cardiomyocytes were isolated by enzymatic dissociation and cell dimensions were evaluated. A line scan camera and digital imaging technique were used to assess cardiomyocyte contraction and inotropic responses to exogenous Ang II (10 to 10(-8) M). RESULTS: Dietary treatment alone had no effect on body growth, whereas combined RAS blockade suppressed somatic growth in the low sodium (LS) group, compared with the high sodium (HS) group. This growth suppression in the LS group was also evident in the heart at the organ and cellular level. Studies of cardiomyocyte contraction showed that myocytes from the LS group exhibited contractile instability and depression of contractile performance. Compared with the HS group, myocytes from the LS group showed a significant reduction in maximum cell shortening (6.40+0.17 vs. 7.32+0.16% resting length, p<0.05), and maximum rate of shortening (3.85+0.14 vs. 4.29+0.11 cell length/ms, p<0.05). Myocytes of the HS group exhibited negative inotropic responses to Ang II at all concentrations tested, with a significant reduction in maximum cell shortening by 11 16% after 12 minutes peptide exposure (p<0.05 vs. non-treated control). In comparison, Ang II elicited both positive and negative responses in myocytes from the LS group, with a predominant negative inotropic effect. CONCLUSIONS: This study provides evidence that combined RAS blockade treatment under restricted sodium intake conditions can impair cardiomyocyte contractile function in association with cardiomyocyte growth suppression. Chronic RAS blockade qualitatively alters the intrinsic inotropic status and responsiveness of ventricular cardiomyocytes, and this shift is further modulated by dietary sodium intake conditions.

Angiotensin II↗
PubMedDate not supplied

Telomere stability correlates with longevity of human beings exposed to ionizing radiations.

Normal somatic cells have a finite number of divisions, a limited capacity to proliferate. Human telomeres contain TTAGGG repeats which are considered a molecular clock marker. The gradual and progressive telomere shortening at each replicative cycle is associated, through the activation of pRB and p53 pathways and genomic instability, to the replicative senescence, a non-dividing state and widespread cell death. There is no information available about telomere status in individuals who live long and have been exposed to ionizing radiations (IR). To determine the telomere stability, we examined telomeres at metaphase, G2-type chromosome aberrations after IR treatment and karyotypic analysis of 15 individuals. Three individuals were above the age of 80 years and 1 among the 3 was estimated to have received more than 10 Gy of occupational exposure about 30 years back. The other 12 were cancer patients that had received more than 50 Gy of gamma-radiation for therapeutic purposes. No telomere instability or defective G2 chromosome repair was found in 3 individuals above the age of 80 years. Whereas, 3 out of 7 prostate and 1 out of 5 breast cancer patients showed higher G2-type chromosome damage as well as a high frequency of telomeric association (also known as chromosome end associations) along with frequent loss of telomeres. Present studies demonstrate that telomere stability along with normal G2 chromosome repair correlates with the longevity of human beings, whereas defective G2 chromosome repair and telomere instability correlate with the radiotherapy related late toxicity.

Aged↗
PubMed1996

Changes in telomere lengths in renal cell carcinomas.

Telomeres, the extreme ends of chromosomes, play an important role in chromosome structure and function. The shortening of telomeres is one of the supposed mechanisms of cellular aging and death. Because of end replication problems the length of telomeres decreases with every cell cycle. This may lead to chromosome instability and additional genetic alterations possibly responsible of significant tumor development. In many cancer cells the length of telomeres depends on a balance between the loss of telomeric repeats, at each replication cycle, and the telomere lengthening, by the enzyme telomerase, which is repressed in most normal somatic cells. Many tumor cells demonstrate shortened telomeres in comparison to the corresponding normal tissue. In some types of human cancers the reduction of telomeric repeats was correlated with increasing disease severity. We analyzed Southern blots of HINF1-digested DNA of a large number of renal cell carcinomas (RCC) including different tumor areas, secondary tumors and metastases (76 cases with 142 tumor samples) for changes in the length of telomeric repeats using the oligonucleotide probe (TTAGGG)3 and found telomere shortening in 54%, suggesting that a reduction of the telomeric repeat length is not a general characteristic in RCC. Intratumor heterogeneity was demonstrated in seven cases. But also two RCC, with elongated telomeres in the tumor tissue, were observed. Shortened telomeres do not seem to be associated with advanced stages of tumor development or specific histopathological subtypes of RCC.

Adult↗