Erratum to: Butyrate-containing structured lipids act on HDAC4, HDAC6, DNA damage and telomerase activity during promotion of experimental hepatocarcinogenesis

In this review, we propose a holistic approach to understanding cancer as a metabolic disease. Our search for relevant studies in medical databases concludes that cancer cells do not evolve directly from normal healthy cells. We hypothesize that aberrant DNA damage accumulates over time—avoiding the natural DNA controls that otherwise repair or replace the rapidly replicating cells. DNA damage starts to accumulate in non-replicating cells, leading to senescence and aging. DNA damage is linked with genetic and epigenetic factors, but the development of cancer is favored by telomerase activity. Evidence indicates that telomere length is affected by chronic inflammations, alterations of mitochondrial DNA, and various environmental factors. Emotional stress also influences telomere length. Chronic inflammation can cause oxidative DNA damage. Oxidative stress, in turn, can trigger mitochondrial changes, which ultimately alter nuclear gene expression. This vicious cycle has led several scientists to view cancer as a metabolic disease. We have proposed complex personalized treatments that seek to correct multiple changes simultaneously using a psychological approach to reduce chronic stress, immune checkpoint therapy with reduced doses of chemo and radiotherapy, minimal surgical intervention, if any, and mitochondrial metabolic reprogramming protocols supplemented by intermittent fasting and personalized dietary plans without interfering with the other therapies.

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Mouse prostate tumor inhibition via disruption of murine telomerase: In vivo and in vitro data for a new preclinical cancer model

Journal of Clinical Oncology ◽

10.1200/jco.2009.27.15_suppl.e14631 ◽

2009 ◽

Vol 27 (15_suppl) ◽

pp. e14631-e14631

Author(s):

T. Xu ◽

Y. Xu ◽

R. Lao ◽

K. He ◽

L. Xue ◽

...

Keyword(s):

Prostate Cancer ◽

Dna Damage ◽

Cancer Cells ◽

Cancer Cell Line ◽

Telomerase Activity ◽

Telomerase Rna ◽

Prostate Cancer Cells ◽

Mouse Prostate

e14631 Background: Telomerase-interference (TI), a novel therapeutic strategy, exploits the high telomerase activity in prostate cancer by introducing a mutated telomerase RNA (MT-Ter) that encodes toxic telomeres. Until now, TI has been tested by targeting human telomerase in tumor cells xenografted into immuno-deficient mice, an inadequate model for predicting efficacy and toxicity. We designed and validated 2 new TI gene constructs that specifically target murine telomerase RNA (mTER), enabling the study of TI in preclinical mouse models that are immuno-competent and that develop endogenous prostate tumors. Methods: We designed 2 constructs and cloned them into a lentiviral delivery system: MT-mTER and siRNA against wild type mTer (α-mTer-siRNA). Using a mouse prostate cancer cell line, E4, we tested the 2 constructs for expression (RT-PCR), telomerase activity (TRAP), and biologic activity (53bp1 DNA damage staining, MTS growth assay, TUNEL and caspase apoptosis assays), as well as in vivo efficacy (NOD-SCID allografts). Results: We confirmed MT-mTER expression (∼50-fold) and showed that α-mTer-siRNA specifically depleted WT-mTER (80% reduction) but not MT-mTER when the 2 constructs are co-expressed; thus, the 2 constructs in combination effectively substituted MT-mTer for WT-mTer in the mouse prostate cancer cells. MT-mTER caused mutant telomeric repeats (TTTGGG instead of TTAGGG) to be added to the ends of telomeres, resulting in rapid telomeric uncapping marked by 53bp1 DNA damage foci (an average 7.5 foci/cell vs. 1.4 foci/cell in vector control). This, in turn, led to rapid and significant apoptosis (>90% TUNEL and caspase +) and growth inhibition in vitro (90% reduction by MTS) and in vivo (75% reduction in tumor allograft size). Conclusions: We successfully designed and validated MT-mTer and α-mTer-siRNA, 2 novel gene constructs that specifically target and co-opt murine telomerase activity within mouse prostate cancer cells. These constructs offer a significant advantage, as they can be used to investigate TI in immuno-competent mice that develop prostate cancer, thereby modeling actual human disease and testing TI-based therapies in a much more informative and authentic manner. No significant financial relationships to disclose.

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Derepression of hTERT gene expression promotes escape from oncogene-induced cellular senescence

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1602379113 ◽

2016 ◽

Vol 113 (34) ◽

pp. E5024-E5033 ◽

Cited By ~ 46

Author(s):

Priyanka L. Patel ◽

Anitha Suram ◽

Neena Mirani ◽

Oliver Bischof ◽

Utz Herbig

Keyword(s):

Dna Damage ◽

Cancer Progression ◽

Ectopic Expression ◽

Telomerase Activity ◽

Early Event ◽

Telomere Dysfunction ◽

Telomeric Dna ◽

Human Telomerase Reverse Transcriptase ◽

Htert Gene ◽

In Cells

Oncogene-induced senescence (OIS) is a critical tumor-suppressing mechanism that restrains cancer progression at premalignant stages, in part by causing telomere dysfunction. Currently it is unknown whether this proliferative arrest presents a stable and therefore irreversible barrier to cancer progression. Here we demonstrate that cells frequently escape OIS induced by oncogenic H-Ras and B-Raf, after a prolonged period in the senescence arrested state. Cells that had escaped senescence displayed high oncogene expression levels, retained functional DNA damage responses, and acquired chromatin changes that promoted c-Myc–dependent expression of the human telomerase reverse transcriptase gene (hTERT). Telomerase was able to resolve existing telomeric DNA damage response foci and suppressed formation of new ones that were generated as a consequence of DNA replication stress and oncogenic signals. Inhibition of MAP kinase signaling, suppressing c-Myc expression, or inhibiting telomerase activity, caused telomere dysfunction and proliferative defects in cells that had escaped senescence, whereas ectopic expression of hTERT facilitated OIS escape. In human early neoplastic skin and breast tissue, hTERT expression was detected in cells that displayed features of senescence, suggesting that reactivation of telomerase expression in senescent cells is an early event during cancer progression in humans. Together, our data demonstrate that cells arrested in OIS retain the potential to escape senescence by mechanisms that involve derepression of hTERT expression.

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MEC3, MEC1, and DDC2Are Essential Components of a Telomere Checkpoint Pathway Required for Cell Cycle Arrest during Senescence in Saccharomyces cerevisiae

Molecular Biology of the Cell ◽

10.1091/mbc.02-02-0012 ◽

2002 ◽

Vol 13 (8) ◽

pp. 2626-2638 ◽

Cited By ~ 81

Author(s):

Shinichiro Enomoto ◽

Lynn Glowczewski ◽

Judith Berman

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Cycle ◽

Dna Damage ◽

Telomerase Activity ◽

Cellular Level ◽

Dna Damage Checkpoint ◽

Average Growth ◽

Progressive Decline ◽

Checkpoint Response ◽

Essential Components

When telomerase is absent and/or telomeres become critically short, cells undergo a progressive decline in viability termed senescence. The telomere checkpoint model predicts that cells will respond to a damaged or critically short telomere by transiently arresting and activating repair of the telomere. We examined the senescence of telomerase-deficient Saccharomyces cerevisiae at the cellular level to ask if the loss of telomerase activity triggers a checkpoint response. As telomerase-deficient mutants were serially subcultured, cells exhibited a progressive decline in average growth rate and an increase in the number of cells delayed in the G2/M stage of the cell cycle. MEC3, MEC1, andDDC2, genes important for the DNA damage checkpoint response, were required for the cell cycle delay in telomerase-deficient cells. In contrast, TEL1,RAD9, and RAD53, genes also required for the DNA damage checkpoint response, were not required for the G2/M delay in telomerase-deficient cells. We propose that the telomere checkpoint is distinct from the DNA damage checkpoint and requires a specific set of gene products to delay the cell cycle and presumably to activate telomerase and/or other telomere repair activities.

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One-Two Punch Therapy for the Treatment of T-Cell Malignancies Involving p53-Dependent Cellular Senescence

Oxidative Medicine and Cellular Longevity ◽

10.1155/2021/5529518 ◽

2021 ◽

Vol 2021 ◽

pp. 1-20

Author(s):

Yingjie Qing ◽

Hui Li ◽

Yunzi Zhao ◽

Po Hu ◽

Xiangyuan Wang ◽

...

Keyword(s):

Dna Damage ◽

T Cell ◽

Cellular Senescence ◽

Apoptotic Cell ◽

Telomerase Activity ◽

Flavonoid Compound ◽

Antitumor Effects ◽

Drug Induced ◽

Human Telomerase Reverse Transcriptase ◽

T Cell Malignancies

T-cell malignancies are still difficult to treat due to a paucity of plans that target critical dependencies. Drug-induced cellular senescence provides a permanent cell cycle arrest during tumorigenesis and cancer development, particularly when combined with senolytics to promote apoptosis of senescent cells, which is an innovation for cancer therapy. Here, our research found that wogonin, a well-known natural flavonoid compound, not only had a potential to inhibit cell growth and proliferation but also induced cellular senescence in T-cell malignancies with nonlethal concentration. Transcription activity of senescence-suppression human telomerase reverse transcriptase (hTERT) and oncogenic C-MYC was suppressed in wogonin-induced senescent cells, resulting in the inhibition of telomerase activity. We also substantiated the occurrence of DNA damage during the wogonin-induced aging process. Results showed that wogonin increased the activity of senescence-associated β-galactosidase (SA-β-Gal) and activated the DNA damage response pathway mediated by p53. In addition, we found the upregulated expression of BCL-2 in senescent T-cell malignancies because of the antiapoptotic properties of senescent cells. Following up this result, we identified a BCL-2 inhibitor Navitoclax (ABT-263), which was highly effective in decreasing cell viability and inducing apoptotic cell death in wogonin-induced senescent cells. Thus, the “one-two punch” approach increased the sensibility of T-cell malignancies with low expression of BCL-2 to Navitoclax. In conclusion, our research revealed that wogonin possesses potential antitumor effects based on senescence induction, offering a better insight into the development of novel therapeutic methods for T-cell malignancies.

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MicroRNA regulation of the MRN complex impacts DNA damage, cellular senescence and angiogenic signaling

10.1101/132258 ◽

2017 ◽

Author(s):

Cristina Espinosa-Diez ◽

RaeAnna Wilson ◽

Namita Chatterjee ◽

Clayton Hudson ◽

Rebecca Ruhl ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Targeted Delivery ◽

Genotoxic Stress ◽

Telomerase Activity ◽

Loss Of Function ◽

Mrn Complex ◽

Vegf Signaling

AbstractMicroRNAs contribute to biological robustness by buffering cellular processes from external perturbations. Here we report an unexpected link between DNA damage response and angiogenic signaling that is buffered by two distinct microRNAs. We demonstrate that genotoxic stress-induced miR-494 and miR-99b inhibit the DNA repair machinery by targeting the MRE11a-RAD50-NBN (MRN) complex. Functionally, gain and loss of function experiments show that miR-494 and miR-99b affect telomerase activity, activate p21 and Rb pathways and diminish angiogenic sproutingin vitroandin vivo. Genetic and pharmacological disruption of VEGFR-2 signaling and the MRN complex reveal a surprising co-dependency of these pathways in regulating endothelial senescence and proliferation. Vascular-targeted delivery of miR-494 decreases both growth factor-induced and tumor angiogenesis in mouse models. Mechanistically, disruption of the MRN complex induced CD44, a known driver of senescence and regulator of VEGF signaling in addition to suppressing IL-13 a stimulator of VEGF signaling. Our work identifies a putative miR-facilitated mechanism by which endothelial cells can be insulated against VEGF signaling to facilitate the onset of senescence and highlight the potential of targeting DNA repair to disrupt pathological angiogenesis.

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Telomerase interference in combination with docetaxel therapy for maximal prostate cancer inhibition: In vitro data for a novel therapeutic approach

Journal of Clinical Oncology ◽

10.1200/jco.2009.27.15_suppl.e14596 ◽

2009 ◽

Vol 27 (15_suppl) ◽

pp. e14596-e14596

Author(s):

D. Sahu ◽

T. Xu ◽

R. Lau ◽

L. Xue ◽

A. Goldkorn

Keyword(s):

Prostate Cancer ◽

Dna Damage ◽

Vector Control ◽

Telomere Length ◽

Statistical Significance ◽

Telomerase Activity ◽

Telomerase Rna ◽

Castration Resistant Prostate Cancer ◽

Novel Therapeutic

e14596 Background: Metastatic castration-resistant prostate cancer (mCRPC) carries a median survival of 18 months with standard docetaxel based therapies. Telomerase interference (TI) is a promising novel therapeutic strategy that exploits the high telomerase activity in cancer cells by introducing a mutated telomerase RNA (MT-Ter) that encodes toxic telomeres and rapidly induces apoptosis. We investigated whether TI can be combined with docetaxel therapy to achieve greater growth inhibition in mCRPC. Methods: PC3 and DU145 mCRPC cell lines were treated with docetaxel in the presence of TI or vector control. TI was accomplished by concurrent lentiviral expression of 2 constructs: telomerase RNA with an altered template region (MT-Ter) and siRNA targeting wild-type telomerase RNA (anti-Ter siRNA). Telomere length and telomerase activity were assessed using RT-PCR and TRAP, respectively. Proliferation, apoptosis, and DNA damage were quantified using MTS, TUNEL, and 53bp1 staining, respectively. Statistical significance was calculated using a 2-sided t-test. Results: Docetaxel (10nM) induced 22% inhibition (p=0.01) of PC3 proliferation in the presence of vector control and 41% inhibition (p=0.001) in the presence of TI (results were similar in DU145 cells). This near-doubling of efficacy was attributable to an independent inhibitory effect (17% inhibition, p=0.04) from TI treatment alone, which occurred without change in bulk telomere length or telomerase activity. TI alone generated increased numbers of DNA damage foci (7/cell vs. 2/cell with vector control) while docetaxel alone did not generate significant increases in DNA damage. Both TI and docetaxel induced a marked increase in the rate of apoptosis. Conclusions: Docetaxel and TI each exerted a pro-apoptotic effect which, when combined, produced an additive inhibition of mCRPC proliferation. TI-mediated apoptosis ensued from DNA damage, consistent with its known telomeric-uncapping effect, while docetaxel-induced apoptosis was not associated with direct DNA damage, also consistent with known docetaxel mechanisms of action. These findings underscore the therapeutic promise of combining standard agents with TI to improve efficacy and reduce toxicity. No significant financial relationships to disclose.

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The Impact of Telomere Shortening in Dyskeratosis Congenita Cells on DNA Damage Response Pathways.

Blood ◽

10.1182/blood.v110.11.4052.4052 ◽

2007 ◽

Vol 110 (11) ◽

pp. 4052-4052

Author(s):

Travis Witt ◽

Aloysius Klingelhutz ◽

Erik Westin ◽

Preeti Satyanarayana ◽

Peter M. Lansdorp ◽

...

Keyword(s):

Bone Marrow ◽

Dna Damage ◽

Dna Damage Response ◽

Cellular Proliferation ◽

Bone Marrow Failure ◽

Telomerase Activity ◽

Dyskeratosis Congenita ◽

Cytotoxic Agents ◽

Damage Response ◽

And Control

Abstract Dyskeratosis congenita (DC) is an inherited multisystem disorder of premature aging, typically characterized by bone marrow failure, mucosal leukoplakia, abnormal skin pigmentation, and nail dystrophy. The X-linked and autosomal dominant forms of DC are associated with mutations in genes that affect telomerase activity resulting in a decrease in telomere length. DC, like other bone marrow failure disorders, is associated with ineffective hematopoiesis and a cancer predisposition. Standard treatment of bone marrow failure or cancer requires cytotoxic therapy, and clinical observations suggest DC patients have an increased sensitivity to cytotoxic therapy. To explain this, we hypothesized that the short telomeres in somatic cells from DC patients could alter the activity and/or expression of several proteins involved in DNA repair or the response to cellular stress including p16, p53 and p21. Lymphocytes from five DC subjects and age-matched controls were stimulated to grow in vitro in the presence of various cytotoxic agents with different modes of action, including Taxol (antimitotic agent and microtubule inhibitor) and Etoposide (topoisomerase inhibitor and DNA damaging agent). In addition, we tested fibroblasts and keratinocyte extracted from skin biopsies from DC and control subjects that were serially passaged. Cellular proliferation and cell death were monitored by cell counts and flow cytometry. Western blotting was used to measure steady state and DNA damage- induced expression of tumor suppressor protein p53 and other proteins involved in DNA damage response signaling pathway, including p16 and p21 in relation to telomere length. Results of flow cytometry accompanied by direct visualization showed a decreased proliferation of DC lymphocytes compared to normal cells, and this growth disadvantage was further accentuated following cell exposure to cytotoxic agents. DC lymphocytes exposed to 10−6 M Taxol showed a decrease in cellular proliferation between 3 and 8 fold while normal control cells exposed to the same agents exhibited only a 3 to 4 fold decrease in cell growth. Similarly DC lymphocytes exposed to Etoposide were inhibited to a greater extent than control cells. Western blot analysis of whole cell lysates indicated a difference in DNA damage response proteins. Of note, lymphocytes from several DC subjects exposed to Taxol did not upregulate p53 expression, while inducible levels were noted in Taxol-treated control cells. In contrast, DC and control lymphocytes exposed to Etoposide upregulated p53 in a similar dose dependent manner. No differences were noted in DC versus control lymphocytes with regards to basal or chemotherapy induced p16 expression. Interestingly, late passage DC fibroblasts displayed enhanced basal expression of p16. These results support the clinical observation of increased “chemosensitivity” in DC subjects and suggest that diminished telomerase activity and premature telomere shortening may interfere with normal DNA damage and stress response pathways. These data are also consistent with our finding that DC fibroblasts, keratinocytes, and lymphocytes have a reduced cell proliferative lifespan. Further studies are needed to dissect the role of telomeres in the cellular response to various types of DNA damage.

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