scholarly journals PML is required for telomere stability in non-neoplastic human cells

Oncogene ◽  
2015 ◽  
Vol 35 (14) ◽  
pp. 1811-1821 ◽  
Author(s):  
M Marchesini ◽  
R Matocci ◽  
L Tasselli ◽  
V Cambiaghi ◽  
A Orleth ◽  
...  
Keyword(s):  
Chromosomal Abnormalities ◽  
Human Fibroblasts ◽  
Telomerase Activity ◽  
Telomere Shortening ◽  
Normal Cells ◽  
Telomere Attrition ◽  
Shelterin Complex ◽  
Alternative Lengthening ◽  
Physiologic Function ◽  
Normal Human

Abstract Telomeres interact with numerous proteins, including components of the shelterin complex, whose alteration, similarly to proliferation-induced telomere shortening, initiates cellular senescence. In tumors, telomere length is maintained by Telomerase activity or by the Alternative Lengthening of Telomeres mechanism, whose hallmark is the telomeric localization of the promyelocytic leukemia (PML) protein. Whether PML contributes to telomeres maintenance in normal cells is unknown. We show that in normal human fibroblasts the PML protein associates with few telomeres, preferentially when they are damaged. Proliferation-induced telomere attrition or their damage due to alteration of the shelterin complex enhances the telomeric localization of PML, which is increased in human T-lymphocytes derived from patients genetically deficient in telomerase. In normal fibroblasts, PML depletion induces telomere damage, nuclear and chromosomal abnormalities, and senescence. Expression of the leukemia protein PML/RARα in hematopoietic progenitors displaces PML from telomeres and induces telomere shortening in the bone marrow of pre-leukemic mice. Our work provides a novel view of the physiologic function of PML, which participates in telomeres surveillance in normal cells. Our data further imply that a diminished PML function may contribute to cell senescence, genomic instability, and tumorigenesis.

scholarly journals Role of p14ARF in Replicative and Induced Senescence of Human Fibroblasts

2001 ◽  
Vol 21 (20) ◽  
pp. 6748-6757 ◽  
Author(s):  
Wenyi Wei ◽  
Ruth M. Hemmer ◽  
John M. Sedivy
Keyword(s):  
Replicative Senescence ◽  
Human Fibroblasts ◽  
Growth Arrest ◽  
Fibroblast Cell ◽  
Cell Types ◽  
Major Pathway ◽  
Telomere Shortening ◽  
Normal Human ◽  
Cell Strains

ABSTRACT Following a proliferative phase of variable duration, most normal somatic cells enter a growth arrest state known as replicative senescence. In addition to telomere shortening, a variety of environmental insults and signaling imbalances can elicit phenotypes closely resembling senescence. We used p53−/− and p21−/− human fibroblast cell strains constructed by gene targeting to investigate the involvement of the Arf-Mdm2-p53-p21 pathway in natural as well as premature senescence states. We propose that in cell types that upregulate p21 during replicative exhaustion, such as normal human fibroblasts, p53, p21, and Rb act sequentially and constitute the major pathway for establishing growth arrest and that the telomere-initiated signal enters this pathway at the level of p53. Our results also revealed a number of significant differences between human and rodent fibroblasts in the regulation of senescence pathways.

Extensive Chromosome Instability in Acute Myeloid Leukemia Is Associated with Critical Telomere Shortening.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3376-3376
Author(s):  
Susan J.J. Swiggers ◽  
Marianne A. Kuijpers ◽  
Maartje J. de Cort ◽  
Berna Beverloo ◽  
J. Mark J.M. Zijlmans
Keyword(s):  
Telomere Length ◽  
Reciprocal Translocation ◽  
Genetic Instability ◽  
Myeloid Leukemia ◽  
Chromosomal Abnormalities ◽  
Chromosome Instability ◽  
Telomerase Activity ◽  
In Vitro Models ◽  
Telomere Shortening

Abstract Telomeres, the ends of linear chromosomes, have a critical role in protection against chromosome end-to-end fusion. Telomeres shorten in every cell division due to the end replication problem. Telomerase is a reverse transcriptase that adds telomeric DNA repeats to the ultimate chromosome end. In vitro models of long-term fibroblast cultures have identified two sequential mortality stages, senescence (M1) and crisis (M2). Senescence can be bypassed by loss of p53 or Rb function, whereas escape from crisis can only be achieved by activating a telomere maintenance mechanism, mostly telomerase reactivation. Cells that bypass senescence (M1) did not reactivate telomerase, resulting in further telomere shortening to a critical telomere length upon reaching crisis (M2). In these models, critical telomere shortening induces extensive chromosome instability, most likely via chromosome end-to-end fusions. Dicentric chromosomes lead to anaphase breakage-fusion-bridges resulting in multiple chromosomal aberrations. To investigate whether similar mechanisms may be involved in the development of genetic instability in human cancer, we studied telomere length and expression of critical telomeric proteins (TRF2 and POT1) in acute myeloid leukemia (AML) patients. AML is a good model for these studies since distinct subgroups of AML are characterized by either exchanges along chromosome arms (translocation or inversion), or by a complex karyotype with multiple chromosome aberrations. Groups were age-matched. Telomere length was studied in metaphase arrested leukemic cells using quantitative fluorescence in situ hybridization (Q-FISH) using a telomere-specific probe. Subsequently, metaphase spreads were hybridized with a leukemia-specific probe to confirm leukemic origin of each metaphase. Telomeres were significantly shorter in AML samples with multiple chromosomal abnormalities in comparison to AML samples with a reciprocal translocation/inversion or no abnormalities (mean±SEM=16±1.7 AFU, n=12 versus 29±4.3 AFU, n=18; p=0.015). Interestingly, telomerase activity level is significantly higher in AML samples with multiple chromosomal abnormalities, compared to AML samples with a reciprocal translocation or inversion (mean±SEM=330±95, n=11 versus 70±21, n=13; p=0.02). Expression levels of telomeric proteins TRF2 and POT1 were similar in these AML groups. Our observations suggest that, consistent with previous in vitro models in fibroblasts, critical telomere shortening may have a role in the development of genetic instability in human AML. Critically short telomeres in association with high levels of telomerase activity suggest that AML cells with multiple chromosomal abnormalities have bypassed crisis (M2). The longer telomeres and low levels of telomerase activity in AML cells with a reciprocal translocation or inversion suggest that they originate from an earlier stage, preceding crisis. Consequently, telomere length modulation may have a role in cancer prevention.

Hormone-brain-aging relationships, broadly reactive with imidazole-containing dipeptides: targeting of telomere attrition as an aging biomarker and dynamic telomerase activity flirting

2015 ◽  
Vol 26 (2) ◽  
Author(s):  
Mark A. Babizhayev ◽  
Khava S. Vishnyakova ◽  
Yegor E. Yegorov
Keyword(s):  
Healthy Aging ◽  
Brain Aging ◽  
The United States ◽  
Telomerase Activity ◽  
Therapeutic Drug ◽  
Physiological Control ◽  
Telomere Shortening ◽  
Therapeutic Concept ◽  
Telomere Attrition ◽  
Age Related

AbstractIt has been documented that telomere-associated cellular senescence may contribute to certain age-related disorders, and telomere length (TL) may be an informative biomarker of healthy aging. Hormone-brain-aging behavior-modulated telomere dynamics and changes in telomerase activity are consistent elements of cellular alterations associated with changes in proliferative state, and these processes are consequently considered as the new therapeutic drug targets for physiological control with advanced drug delivery and nutritional formulations. We raise and support a therapeutic concept of using nonhydrolyzed forms of naturally occurring neuron-specific imidazole dipeptide-based compounds carnosine and carcinine, making it clinically possible that slowing down the rate of telomere shortening could slow down the human aging process in specific tissues where proliferative senescence is known to occur, with the demonstrated evidence of telomere shortening that appeared to be a hallmark of oxidative stress and disease. Carnosine released from skeletal muscle during exercise may be transported into the hypothalamic tuberomammillary nucleus (TMN) histamine neurons and hydrolyzed. The resulting L-histidine may subsequently be converted into histamine, which could be responsible for the effects of carnosine on neurotransmission and hormone-like antiaging physiological function. The preliminary longitudinal studies of elderly individuals suggest that longer telomeres are associated with better survival, and an advanced oral nutritional support with nonhydrolyzed carnosine (or carcinine and patented compositions thereof) is a useful therapeutic tool for a critical TL maintenance that may fundamentally be applied in the treatment of age-related sight-threatening eye disorders, prolonged life expectancy, increased survival and chronological age of an organism in health control, smoking behavior, and disease.  “Our pleasures were simple—they included survival.”   —Dwight D. Eisenhower, 34th President of the United States, 1953–1961

Abrupt telomere shortening in normal human fibroblasts

2010 ◽  
Vol 45 (3) ◽  
pp. 235-242 ◽  
Author(s):  
Nikolina Škrobot Vidaček ◽  
Andrea Ćukušić ◽  
Milena Ivanković ◽  
Hrvoje Fulgosi ◽  
Miljenko Huzak ◽  
...  
Keyword(s):  
Human Fibroblasts ◽  
Telomere Shortening ◽  
Normal Human

Inhibition of Homologous Recombination Pathway Promotes Telomere Shortening and Cell Survival without Affecting Telomerase Activity In Myeloma

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 786-786
Author(s):  
Jagannath Pal ◽  
Jason Wong ◽  
Puru Nanjappa ◽  
Saem Lee ◽  
Masood Shammas ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Telomere Length ◽  
Board Of Directors ◽  
Telomerase Activity ◽  
Human Cells ◽  
Telomere Maintenance ◽  
Advisory Committees ◽  
Telomere Shortening ◽  
Telomerase Inhibitor ◽  
Normal Human

Abstract Abstract 786 Recombinase (RAD51) expression and homologous recombination (HR) activity are low in normal human cells including plasma cells. It is significantly induced following exposure of normal human cells to carcinogen, and is constitutively elevated in cancer cells including multiple myeloma (MM) cells. Besides its effect on genomic stability, elevated or dysregulated HR has also been implicated in telomere maintenance in tumor and immortalized cells. These cells usually lack telomerase activity and maintain telomere length by ALT mechanism (alternate lengthening of telomeres). Inhibitors of homologous recombination, therefore, have potential not only to prevent/reduce genomic instability, but also inhibit telomere maintenance, and cancer survival. We have here investigated the effect of inhibitor of HR on telomere maintenance mechanism in MM. We have evaluated effect of Nilotinib, a tyrosine kinase inhibitor and RAD51 shRNA on HR in MM. First we observed that nilotinib inhibits and RAD51 phosphorylation in MM. Nilotinib at both 5 and 10 mM concentration also led to dose-dependent inhibition of recombinase expression in MM cells. Importantly, Nilotinib also inhibited HR activity in MM cells as well as other cancer cell lines, as measured by a plasmid based assay in which leuciferase activity is generated following homologous recombination. We next evaluated effect of nilotinib on telomere maintenance alone as well as in combination with agents inhibiting telomere maintenance. The MM cells were treated for 48 hrs, either with nilotinib, telomerase inhibitor, or both nilotinib and telomerase inhibitor and evaluated for telomerase activity as well as effect on telomere length. As expected, the treatment of myeloma cells with telomerase inhibitor at 1 mM led to 88% inhibition of telomerase activity relative to control cells. Nilotinib, either alone or in the presence of telomerase inhibitor, did not have any major effect on telomerase activity in these cells. The cells were cultured in the presence of these agents for 2 weeks and evaluated for telomere length, using telomere specific real time PCR. Cells in presence of Telomerase inhibitor at 1 mM in fact had slightly increased telomere length (9%), probably due to presence or activation of ALT mechanism, following loss of telomerase activity. Importantly, nilotinib alone at 10 mM led to 20% reduction in telomere length and when combined with telomerease inhibitor at 1 mM concentrations led to reduction in the telomere length in MM cells by 52%. Moreover we have observed that transduction of MM cells with shRNA targeting RAD51 combined with telomerase inhibitor induced greater and quicker MM cell kill compared to either of these treatments alone. These data indicate that elevated HR pathway contributes to telomere maintenance in MM and combining inhibitors of HR with telomerase would expedite telomere shortening and cell death providing more effective therapeutic strategy. Disclosures: Munshi: Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees.

scholarly journals ATR cooperates with CTC1 and STN1 to maintain telomeres and genome integrity in Arabidopsis

2012 ◽  
Vol 23 (8) ◽  
pp. 1558-1568 ◽  
Author(s):  
Kara A. Boltz ◽  
Katherine Leehy ◽  
Xiangyu Song ◽  
Andrew D. Nelson ◽  
Dorothy E. Shippen
Keyword(s):  
Genome Stability ◽  
First Generation ◽  
Telomerase Activity ◽  
Ataxia Telangiectasia Mutated ◽  
Telomere Shortening ◽  
Telomere Attrition ◽  
Damage Response ◽  
Chromosome Fusions ◽  
Repair Genes ◽  
Prolonged Absence

The CTC1/STN1/TEN1 (CST) complex is an essential constituent of plant and vertebrate telomeres. Here we show that CST and ATR (ataxia telangiectasia mutated [ATM] and Rad3-related) act synergistically to maintain telomere length and genome stability in Arabidopsis. Inactivation of ATR, but not ATM, temporarily rescued severe morphological phenotypes associated with ctc1 or stn1. Unexpectedly, telomere shortening accelerated in plants lacking CST and ATR. In first-generation (G1) ctc1 atr mutants, enhanced telomere attrition was modest, but in G2 ctc1 atr, telomeres shortened precipitously, and this loss coincided with a dramatic decrease in telomerase activity in G2 atr mutants. Zeocin treatment also triggered a reduction in telomerase activity, suggesting that the prolonged absence of ATR leads to a hitherto-unrecognized DNA damage response (DDR). Finally, our data indicate that ATR modulates DDR in CST mutants by limiting chromosome fusions and transcription of DNA repair genes and also by promoting programmed cell death in stem cells. We conclude that the absence of CST in Arabidopsis triggers a multifaceted ATR-dependent response to facilitate maintenance of critically shortened telomeres and eliminate cells with severe telomere dysfunction.

scholarly journals Accelerated telomere attrition in children and teenagers with α1-antitrypsin deficiency

2016 ◽  
Vol 48 (2) ◽  
pp. 350-358 ◽  
Author(s):  
Amparo Escribano ◽  
Sara Pastor ◽  
Ana Reula ◽  
Silvia Castillo ◽  
Silvia Vicente ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
High Risk ◽  
Telomere Length ◽  
Telomerase Activity ◽  
Multiple Hypothesis Testing ◽  
Intermediate Risk ◽  
Telomere Shortening ◽  
Telomere Attrition ◽  
Antitrypsin Deficiency ◽  
Risk Patients

Numerous studies have shown that oxidative stress accelerates telomere shortening in several lung pathologies. Since oxidative stress is involved in the pathophysiology of α1-antitrypsin deficiency (AATD), we hypothesised that telomere shortening would be accelerated in AATD patients. This study aimed to assess telomere length in AATD patients and to study its association with α1-antitrypsin phenotypes.Telomere length, telomerase activity, telomerase reverse transcriptase (hTERT) expression and biomarkers of oxidative stress were measured in 62 children and teenagers (aged 2–18 years) diagnosed with AATD and 18 controls (aged 3–16 years).Our results show that intermediate-risk (MZ; SZ) and high-risk (ZZ) AATD patients have significantly shorter telomeres and increased oxidative stress than controls. Correlation studies indicate that telomere length was related to oxidative stress markers in AATD patients. Multiple hypothesis testing revealed an association between telomere length, telomerase activity, hTERT expression and AATD phenotypes; high-risk patients showed shorter telomeres, lower hTERT expression and decreased telomerase activity than intermediate-risk and low-risk patients.AATD patients show evidence of increased oxidative stress leading to telomere attrition. An association between telomere and α1-antitrypsin phenotypes is observed suggesting that telomere length could be a promising biomarker for AATD disease progression.

scholarly journals Study of Synergistic and Protective Effects of Three Different Polar Saffron Extracts and Photon Radiation on Human Colorectal Cancer Cells (HT-29) and Normal Human Fibroblasts

2020 ◽  
Vol 13 (12) ◽  
Author(s):  
Mahnaz Nourbakhsh ◽  
Amin Hosseinzade ◽  
Jamshidkhan Chamani ◽  
Ameneh Sazgarnia ◽  
Roham Salek
Keyword(s):  
Colorectal Cancer ◽  
Cancer Cells ◽  
Synergistic Effects ◽  
Human Fibroblasts ◽  
Protective Effects ◽  
Normal Cells ◽  
Colorectal Cancer Cells ◽  
Normal Human ◽  
Saffron Extract ◽  
Ht 29

Background: There are some hypotheses about radiation-sensitizing and radiation-protective effects of antioxidants. Saffron, dried stigmas of Crocus sativus L., is a precious medicinal plant that contains an impressive variety of plant compounds such as crocin, crocetin, and safranal that act as antioxidants. The present study examined the cytotoxic effects of saffron extracts with different polarity and their synergism or protective effects with radiation on a colorectal cancer cell line (HT-29) and normal human fibroblasts. Objectives: The aim was to find a natural agent to improve radiotherapy efficacy. Methods: HT-29 colorectal cancer cells and normal human fibroblasts were cultured in RPMI1640 medium, incubated with different concentrations of different saffron extracts (50-250 µg/ml), and then were exposed to a dose of 8 Gy of X-rays. The cytotoxicity effect was determined by the MTT assay. Results: Saffron extracts decreased cell viability in HT-29 colorectal cancer cells and normal human fibroblasts as a concentration-dependent manner. Combination radiotherapy with polar saffron extract in most doses showed synergistic effects on HT-29 cell death while it did not show any distinctive synergistic effect in normal cells. Semi-polar and non-Polar extracts just in low doses had synergistic effects on tumor cells. These two extracts did not show any protective effects on normal cells. Conclusions: Among the various saffron extracts, polar saffron extract and low doses of non-polar saffron extract in combination with radiation increase radiation sensitivity and cell death in tumor cells, while they do not increase radiation sensitivity in normal cells and even protect normal cells to some extent.

scholarly journals The effect of chloroquine on the metabolism of [35S]cystine in normal and cystinotic human skin fibroblasts

1981 ◽  
Vol 200 (3) ◽  
pp. 555-563 ◽  
Author(s):  
C J Danpure
Keyword(s):  
Storage Disease ◽  
Human Fibroblasts ◽  
Total Cell ◽  
Optimum Concentration ◽  
Cell Uptake ◽  
Lysosomal Storage ◽  
Normal Cells ◽  
Normal Human ◽  
Uptake And Metabolism

The present study concerns the effect of the lysosomotropic drug chloroquine on the uptake and metabolism of [35S]cystine in vitro by normal human fibroblasts and those from patients suffering from the lysosomal storage disease cystinosis. When the cells were cultured with [35S]cystine for periods in excess of 4 h, it was found that chloroquine considerably increased (up to 30-fold) the labelling of the intracellular cystine pool in cystinotic cells, with no increase or a much smaller increase in normal cells. For this effect chloroquine had an optimum concentration of 20 microM, with a small effect still being noticeable at 1 microM. A quinoline analogue, 4-(dimethylaminoethylamino)-7-iodoquinoline, had a similar effect to chloroquine. However, NH4Cl at concentrations of between 100 microM and 50 mM showed either no effect (at the lower concentrations) or a depression of intracellular cystine labelling (at the higher concentrations). The differences between the effects of the quinolines on cystinotic acid normal cells were not due to differences in total cell uptake of drug.

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