Is telomerase reactivation associated with the down-regulatoin of TGFβ receptor-II expression in human breast cancer?

Background Telomerase is a ribonucleoprotein that synthesizes telomeres and plays an important role in chromosomal stability and cellular immortalisation. Telomerase activity is detectable in most human cancers but not in normal somatic cells. TGF beta (transforming growth factor beta) is a member of a family of cytokines that are essential for cell survival and seems to be down-regulated in human cancer. Recent in vitro work using human breast cancer cell lines has suggested that TGF beta down-regulates the expression of hTERT (human telomerase reverse transcriptase) : the catalytic subunit of telomerase. We have therefore hypothesised that telomerase reactivation is associated with reduced immunohisto-chemical expression of TGF beta type II receptor (RII) in human breast cancer. Methods TGF beta RII immunohistochemical expression was determined in 24 infiltrating breast carcinomas with known telomerase activity (17 telomerase-positive and 7 telomerase-negative). Immunohistochemical expression of TGF beta RII was determined by a breast pathologist who was blinded to telomerase data. Results TGF beta RII was detected in all lesions. The percentage of stained cells ranged from 1–100%. The difference in TGF beta RII expression between telomerase positive and negative tumours was not statistically significant (p = 1.0). Conclusion The results of this pilot study suggest that there is no significant association between telomerase reactivation and TGF-beta RII down-regulation in human breast cancer

The role of telomeres and telomerase in the clinical effect and mechanism of action of psychopharmacological interventions

Originally studied in relation to aging and cancer research, telomeres and telomerase are now also investigated in relation to psychiatric disorders and treatments. Based on findings emerging from clinical and preclinical data, we hypothesize that the telomere–telomerase system represents a novel element mediating the mechanism of action of certain psychopharmacological interventions. In this symposium I’ll present the preliminary evidence on the complex translational relationships between specific psychiatric medications (i.e. antidepressants, lithium and antipsychotics), the telomere–telomerase system and clinical outcomes. The modulation of intracellular Wnt/b-catenin or PI3 K/Akt signaling pathways, the interaction with BDNF and 5-HT, and the antioxidant properties could represent possible mechanisms by which the different types of psychiatric medications could modulate telomere length and telomerase activity. The potential of the telomere–telomerase system in promoting cellular survival and/or function in the brain and in the periphery could, in turn, represent a neurobiological substrate through which these molecules can mediate the therapeutic effect of such interventions. Further, in the present symposium I’ll show data from our research team on telomere length and telomerase activity in leukocytes predicting clinical response to serotonin–specific reuptake inhibitors (SSRIs) in subjects with major depressive disorder

Dynamic telomerase gene suppression via network effects of GSK3 inhibition

<b>Background</b>: Telomerase controls telomere homeostasis and cell immortality and is a promising anti-cancer target, but few small molecule telomerase inhibitors have been developed. Reactivated transcription of the catalytic subunit hTERT in cancer cells controls telomerase expression. Better understanding of upstream pathways is critical for effective anti-telomerase therapeutics and may reveal new targets to inhibit hTERT expression. <b>Methodology/Principal Findings</b>: In a focused promoter screen, several GSK3 inhibitors suppressed hTERT reporter activity. GSK3 inhibition using 6-bromoindirubin-3′-oxime suppressed hTERT expression, telomerase activity and telomere length in several cancer cell lines and growth and hTERT expression in ovarian cancer xenografts. Microarray analysis, network modelling and oligonucleotide binding assays suggested that multiple transcription factors were affected. Extensive remodelling involving Sp1, STAT3, c-Myc, NFκB, and p53 occurred at the endogenous hTERT promoter. RNAi screening of the hTERT promoter revealed multiple kinase genes which affect the hTERT promoter, potentially acting through these factors. Prolonged inhibitor treatments caused dynamic expression both of hTERT and of c-Jun, p53, STAT3, AR and c-Myc. <b>Conclusions/Significance</b>: Our results indicate that GSK3 activates hTERT expression in cancer cells and contributes to telomere length homeostasis. GSK3 inhibition is a clinical strategy for several chronic diseases. These results imply that it may also be useful in cancer therapy. However, the complex network effects we show here have implications for either setting

The telomerase essential N-terminal domain promotes DNA synthesis by stabilizing short RNA-DNA hybrids.

Telomerase is an enzyme that adds repetitive DNA sequences to the ends of chromosomes and consists of two main subunits: the telomerase reverse transcriptase (TERT) protein and an associated telomerase RNA (TER). The telomerase essential N-terminal (TEN) domain is a conserved region of TERT proposed to mediate DNA substrate interactions. Here, we have employed single molecule telomerase binding assays to investigate the function of the TEN domain. Our results reveal telomeric DNA substrates bound to telomerase exhibit a dynamic equilibrium between two states: a docked conformation and an alternative conformation. The relative stabilities of the docked and alternative states correlate with the number of basepairs that can be formed between the DNA substrate and the RNA template, with more basepairing favoring the docked state. The docked state is further buttressed by the TEN domain and mutations within the TEN domain substantially alter the DNA substrate structural equilibrium. We propose a model in which the TEN domain stabilizes short RNA-DNA duplexes in the active site of the enzyme, promoting the docked state to augment telomerase processivity

Cancer-associated TERT promoter mutations abrogate telomerase silencing.

Mutations in the human telomerase reverse transcriptase (TERT) promoter are the most frequent non-coding mutations in cancer, but their molecular mechanism in tumorigenesis has not been established. We used genome editing of human pluripotent stem cells with physiological telomerase expression to elucidate the mechanism by which these mutations contribute to human disease. Surprisingly, telomerase-expressing embryonic stem cells engineered to carry any of the three most frequent TERT promoter mutations showed only a modest increase in TERT transcription with no impact on telomerase activity. However, upon differentiation into somatic cells, which normally silence telomerase, cells with TERT promoter mutations failed to silence TERT expression, resulting in increased telomerase activity and aberrantly long telomeres. Thus, TERT promoter mutations are sufficient to overcome the proliferative barrier imposed by telomere shortening without additional tumor-selected mutations. These data establish that TERT promoter mutations can promote immortalization and tumorigenesis of incipient cancer cells

Tianshengyuan-1 (TSY-1) regulates cellular Telomerase activity by methylation of TERT promoter.

Telomere and Telomerase have recently been explored as anti-aging and anti-cancer drug targets with only limited success. Previously we showed that the Chinese herbal medicine Tianshengyuan-1 (TSY-1), an agent used to treat bone marrow deficiency, has a profound effect on stimulating Telomerase activity in hematopoietic cells. Here, the mechanism of TSY-1 on cellular Telomerase activity was further investigated using HL60, a promyelocytic leukemia cell line, normal peripheral blood mononuclear cells, and CD34+ hematopoietic stem cells derived from umbilical cord blood. TSY-1 increases Telomerase activity in normal peripheral blood mononuclear cells and CD34+ hematopoietic stem cells with innately low Telomerase activity but decreases Telomerase activity in HL60 cells with high intrinsic Telomerase activity, both in a dose-response manner. Gene profiling analysis identified Telomerase reverse transcriptase (TERT) as the potential target gene associated with the TSY-1 effect, which was verified by both RT-PCR and western blot analysis. The β-galactosidase reporter staining assay showed that the effect of TSY-1 on Telomerase activity correlates with cell senescence. TSY-1 induced hypomethylation within TERT core promoter in HL60 cells but induced hypermethylation within TERT core promoter in normal peripheral blood mononuclear cells and CD34+ hematopoietic stem cells. TSY-1 appears to affect the Telomerase activity in different cell lines differently and the effect is associated with TERT expression, possibly via the methylation of TERT promoter

The simultaneous effect of valproic acid and gamma radiation on telomerase activity and bax and Bcl-2 protein levels in MCF-7 breast cancer cell line

Background: Breast cancer is one of the most prevalent types of cancer. Factors such as ionizing radiation and chemotherapeutic agents can trigger apoptosis and cancer cell death. An anticonvulsant drug named Valproic acid is a histone deacetylase inhibitor that shows promising anti-tumor effects in a variety of cancers. Telomerase is a ribonucleoprotein enzyme that activated in cancer cells and lead to telomeres shortening inhibition and triggering the apoptosis. Objectives: The purpose of this research was to investigate the simultaneously effect of Valproic acid and gamma radiation on telomerase activity and bax and Bcl-2 protein level in MCF-7 breast cancer cell line. Materials and Methods: MCF-7 cells was treated with different dose of Valproic acid (0, 2, 8 and 16 mM/l) and single dose of gamma radiation (4 Gy/min. (cell toxicity was determined using neutral uptake test. Telomerase activity was determined using TRAP assay (PCR-ELISA) method. Bax and Bcl-2 protein level was determined by ELISA method, as well. Results: Combination of Valproic acid and gamma radiation increased significantly cell toxicity in a time and dose dependent manner compared with control (P < 0.0001). The ratio of Bax/Bcl-2 was increased in a dose dependent manner at 48 and 72 hour treatment (P < 0.0001). There was a decrease in Telomerase activity after 24, 48 and 72 hours treatment in a dose dependent manner (P < 0.0001). Conclusions: The increasing cell toxicity, apoptosis-inducing effects and decreasing telomerase activity may play an important role in the Valproic acid and radiation mechanism. The current survey suggested that it is likely beneficial to combine Valproic acid and gamma radiation to treat breast cancer. © 2015, School of Pharmacy, Ahvaz Jundishapur University of Medical Sciences

Investigation on Quantitative Structure-Activity Relationships of 1,3,4 Oxadiazole Derivatives as Potential Telomerase Inhibitors

The published manuscript is available at EurekaSelect via http://www.eurekaselect.com/164022/article, DOI : 10.2174/1570163815666180724113208. © 2018 Bentham ScienceA series of 1,3,4-oxadiazole derivatives with significant broad-spectrum anticancer activity against different cell lines, and demonstrated telomerase inhibition, was subjected to Quantitative Structure-Activity Relationships (QSAR) analysis. Validated models with high correlation coefficients were developed. The Multiple Linear Regression (MLR) models, by Ordinary Least Squares (OLS), showed good robustness and predictive capability, according to the Multi-Criteria Decision Making (MCDM = 0.8352), a technique that simultaneously enhances the performances of a certain number of criteria. The descriptors selected for the models, such as electrotopological state (E-state) descriptors, and extended topochemical atom (ETA) descriptors, showed the relevant chemical information contributing to the activity of these compounds. The results obtained in this study make sure about the identification of potential hits as prospective telomerase inhibitors.Peer reviewedFinal Accepted Versio