Telomerase Reverse Transcriptase Levels Research Articles

Application of machine learning to large in-vitro databases to identify cancer cell characteristics: telomerase reverse transcriptase (TERT) expression.

Advances in biotechnology and machine learning have created an enhanced environment for unearthing and exploiting previously unrecognized relationships between genomic and epigenetic data with potential therapeutic implications. We applied advanced algorithms to data from the Cancer Dependency Map to uncover increasingly complex relationships. Specifically, we investigate characteristics of tumor cell lines with varying levels of telomerase reverse transcriptase (TERT) expression in liver cancer. The findings indicate that the effect of CRISPR knockout of Histone Deacetylase 1 (HDAC1) and numerous individual respiratory complex I genes is strongly related to the level of TERT expression, with knockout being particularly efficacious at killing or inhibiting growth of tumor cells with low levels of TERT expression for HDAC1 and high levels for Complex I genes. These findings suggest key biomarkers for therapeutic efficacy and yield novel potential pathways for drug development and provide further proof of principle for the potential of artificial intelligence in oncology.

Overexpression of BAMBI and SMAD7 impacts prognosis of acute myeloid leukemia patients: A potential TERT non-canonical role.

Bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) and mothers against decapentaplegic homolog 7 (SMAD7) are important transforming growth factor-β (TGF-β) signaling antagonists, however their roles in acute myeloid leukemia (AML) remains unclear. Telomerase reverse transcriptase (TERT) may be involved in regulating BAMBI and SMAD7 expressions; a role beyond telomeres that is not clinically validated yet. In this study, we examined the expression levels and prognostic values of BAMBI, SMAD7 and TERT and their association with AML patients' outcomes. Blood samples were collected from 74 de-novo AML patients and 16 controls. Real-time quantitative PCR (qRT-PCR) was performed to analyze BAMBI, SMAD7 and TERT expressions. BAMBI and SMAD7 expression in AML were significantly upregulated versus controls (p< 0.05). BAMBI, SMAD7 and TERT levels were significantly correlated together (p< 0.001). Kaplan-Meier analysis indicated that patients with high BAMBI, SMAD7 and TERT expression levels had markedly shorter event free survival (EFS) and overall survival (OS) time (p< 0.01). Furthermore, multivariate analysis revealed that only high BAMBI expression was an independent risk factor for OS (p= 0.001). BAMBI is a novel biomarker in predicting prognosis in AML patients. Moreover, a potential interplay is found between BAMBI, SMAD7 and TERT in AML pathogenies.

Significance of TERT Genetic Alterations and Telomere Length in Hepatocellular Carcinoma.

Simple SummaryTelomerase reverse transcriptase (TERT) mutations are the most frequent genetic alterations in hepatocellular carcinoma (HCC). However, integrative analysis studies of TERT-telomere signaling during hepatocarcinogenesis are lacking. In this study, we investigated the clinicopathological association and prognostic value of TERT gene alterations and telomere length in HCC patients undergoing hepatectomy as well as transarterial chemotherapy (TACE). We found that there are eight key TERT-interacting genes and higher TERT expression and longer telomere length in HCC. We also found TERT-telomeric signals related to correlation with tumor differentiation and stage progression. TERT promoter mutations were an independent predictor of worse overall survival after hepatectomy, while TERT expression independently predicted worse time to progression after TACE. Telomere length was also associated with survival in TACE-treated patients. These findings suggest that TERT-telomere signals might be useful biomarkers for HCC, but the prognostic values may differ with tumor characteristics and treatment.Telomerase reverse transcriptase (TERT) mutations are reportedly the most frequent somatic genetic alterations in hepatocellular carcinoma (HCC). An integrative analysis of TERT-telomere signaling during hepatocarcinogenesis is lacking. This study aimed to investigate the clinicopathological association and prognostic value of TERT gene alterations and telomere length in HCC patients undergoing hepatectomy as well as transarterial chemotherapy (TACE). TERT promoter mutation, expression, and telomere length were analyzed by Sanger sequencing and real-time PCR in 305 tissue samples. Protein–protein interaction (PPI) analysis was performed to identify a set of genes that physically interact with TERT. The PPI analysis identified eight key TERT-interacting genes, namely CCT5, TUBA1B, mTOR, RPS6KB1, AKT1, WHAZ, YWHAQ, and TERT. Among these, TERT was the most strongly differentially expressed gene. TERT promoter mutations were more frequent, TERT expression was significantly higher, and telomere length was longer in tumors versus non-tumors. TERT promoter mutations were most frequent in HCV-related HCCs and less frequent in HBV-related HCCs. TERT promoter mutations were associated with higher TERT levels and longer telomere length and were an independent predictor of worse overall survival after hepatectomy. TERT expression was positively correlated with tumor differentiation and stage progression, and independently predicted shorter time to progression after TACE. The TERT-telomere network may have a crucial role in the development and progression of HCC. TERT-telomere abnormalities might serve as useful biomarkers for HCC, but the prognostic values may differ with tumor characteristics and treatment.

HIF-1α-Mediated Telomerase Reverse Transcriptase Activation Inducing Autophagy Through Mammalian Target of Rapamycin Promotes Papillary Thyroid Carcinoma Progression During Hypoxia Stress.

Background: It is important to properly understand the molecular mechanisms of aggressive tumors among papillary thyroid carcinomas (PTCs) that are often the most indolent. Hypoxia inducible factor-1α (HIF-1α), induced by hypoxia, plays pivotal roles in the development and metastasis of the many tumors, including PTCs. Upregulation of telomerase reverse transcriptase (TERT) activity is found in highly invasive PTCs. Further, previous studies have reported that autophagy serves as a protective mechanism to facilitate PTC cell survival. We, therefore, hypothesized that there was a link between HIF-1α, TERT, and autophagy in promoting PTC progression. Methods: Immunohistochemistry staining was conducted to evaluate the expressions of HIF-1α, TERT, and autophagy marker, LC3-II, in matched PTC tumors and corresponding nontumor tissues. Two PTC cell lines (TPC-1 and BCPAP) were used in subsequent cytological function studies. Cell viability, proliferation, apoptosis, migration, and invasion were assessed during hypoxia, genetic enhancement and inhibition of TERT, and chemical and genetic inhibition of autophagy. The protein expression levels of the corresponding biomarkers were determined by Western blotting, and autophagy flow was detected. We characterized the molecular mechanism of PTC cell progression. Results: The protein expression levels of HIF-1α, TERT, and LC3-II were upregulated in PTCs and were significantly correlated with high tumor-node-metastasis stage. Further, an in vitro study indicated that HIF-1α induced by hypoxia functioned as a transcriptional activator by binding with sequences potentially located in the TERT promoter and was positively correlated with the malignant behavior of PTC cell lines. Overexpression of TERT inhibited the kinase activity of mammalian target of rapamycin (mTOR), resulting in the activation of autophagy. Functionally, TERT-induced autophagy provided a survival advantage to PTC cells during hypoxia stress. Conclusions: We identified a novel molecular mechanism involving the HIF-1α/TERT axis, which promoted PTC progression by inducing autophagy through mTOR during hypoxia stress. These findings may provide a basis for the new treatment of aggressive PTCs.

TERT and DNMT1 expression predict sensitivity to decitabine in gliomas.

Decitabine (DAC) is an FDA-approved DNA methyltransferase (DNMT) inhibitor that is used in the treatment of patients with myelodysplastic syndromes. Previously, we showed that DAC marks antitumor activity against gliomas with isocitrate dehydrogenase 1 (IDH1) mutations. Based on promising preclinical results, a clinical trial has been launched to determine the effect of DAC in IDH-mutant gliomas. The next step is to comprehensively assess the efficacy and potential determinants of response to DAC in malignant gliomas. The expression and activity of telomerase reverse transcriptase (TERT) and DNMT1 were manipulated in patient-derived IDH1-mutant and -wildtype glioma lines, followed by assessment of cell proliferation with DAC treatment alone or in combination with telomerase inhibitors. RNA sequencing, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment, and correlation analysis were performed. IDH1-mutant glioma tumorspheres with hemizygous codeletion of chromosome arms 1p/19q were particularly sensitive to DAC and showed significant inhibition of DNA replication genes. Our transcriptome analysis revealed that DAC induced expression of cyclin-dependent kinase inhibitor 1A/p21 (CDKN1A), along with downregulation of TERT. These molecular changes were also observed following doxorubicin treatment, supporting the importance of DAC-induced DNA damage in contributing to this effect. We demonstrated that knockdown of p21 led to TERT upregulation. Strikingly, TERT overexpression increased DNMT1 levels and DAC sensitivity via a telomerase-independent mechanism. Furthermore, RNA inhibition (RNAi) targeting of DNMT1 abrogated DAC response in TERT-proficient glioma cells. DAC downregulates TERT through p21 induction. Our data point to TERT and DNMT1 levels as potential determinants of response to DAC treatment.

Telomerase Reverse Transcriptase (TERT) Expression, Telomerase Activity, and Expression of Matrix Metalloproteinases (MMP)-1/-2/-9 in Feline Oral Squamous Cell Carcinoma Cell Lines Associated With Felis catus Papillomavirus Type-2 Infection.

Telomerase activity contributes to cell immortalization by avoiding telomere shortening at each cell division; indeed, its catalytic subunit telomerase reverse transcriptase (TERT) is overexpressed in many tumors, including human oral squamous cell carcinoma (hOSCC). In these tumors, matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases involved in cell migration, contribute to invasive potential of cancer cells. A proportion of hOSCC is associated with infection by high-risk human papillomavirus (HR-HPVs), whose E6 oncogene enhances TERT and MMPs expression, thus promoting cancer progression. Feline oral squamous cell carcinoma (FOSCC) is a malignant tumor with highly invasive phenotype; however, studies on telomerase activity, TERT, and MMPs expression are scarce. In this study, we demonstrate telomerase activity, expression of TERT, and its transcriptional activator cMyc along with expression of MMP-1, -2, and -9 in FOSCC-derived cell lines SCCF2 and SCCF3, suggesting a contribution by these pathways in cell immortalization and invasion in these tumors. Recent studies suggest that a sub-group of FOSCC as well as SCCF2 and SCCF3 are associated with Felis catus PV type-2 (FcaPV-2) infection. However, in this work, FcaPV-2 E6 gene knock-down caused no shift in either TERT, cMyc, or MMPs levels, suggesting that, unlike its human counterpart, the viral oncogene plays no role in their regulation.

The Solo Play of TERT Promoter Mutations.

The reactivation of telomerase reverse transcriptase (TERT) protein is the principal mechanism of telomere maintenance in cancer cells. Mutations in the TERT promoter (TERTp) are a common mechanism of TERT reactivation in many solid cancers, particularly those originating from slow-replicating tissues. They are associated with increased TERT levels, telomere stabilization, and cell immortalization and proliferation. Much effort has been invested in recent years in characterizing their prevalence in different cancers and their potential as biomarkers for tumor stratification, as well as assessing their molecular mechanism of action, but much remains to be understood. Notably, they appear late in cell transformation and are mutually exclusive with each other as well as with other telomere maintenance mechanisms, indicative of overlapping selective advantages and of a strict regulation of TERT expression levels. In this review, we summarized the latest literature on the role and prevalence of TERTp mutations across different cancer types, highlighting their biased distribution. We then discussed the need to maintain TERT levels at sufficient levels to immortalize cells and promote proliferation while remaining within cell sustainability levels. A better understanding of TERT regulation is crucial when considering its use as a possible target in antitumor strategies.

TERT promoter hotspot mutations and their relationship with TERT levels and telomere erosion in patients with head and neck squamous cell carcinoma.

To evaluate the prevalence of two recurrent somatic mutations(-124 C>T and -146 C>T) within thepromoterof the gene encoding telomerase reverse transcriptase (TERT) as well as their relationship with TERT level, telomeres length, and outcome in patients with head and neck squamous cell carcinomas (HNSCCs). We evaluate the prevalence of TERT promoter mutations, TERT levels, and telomere length in paired cancer tissue and adjacent mucosa (AM) in a series of HNSCCs. Cancer tissue and AM specimens from 105 patients were analyzed. Telomere length and TERT mRNA levels were estimated using real-time polymerase chain reaction. TERT promoter mutations were assessed using Sanger sequencing. Out of 105 cases, 101 were considered suitable for the analysis. TERT promoter harbored mutations in 12 tumors (11.9%), with -124 C>T and -146 C>T accounting for 83.3% and 16.7% of the alterations, respectively. No mutations were detected in AM samples. The prevalence of TERT promoter mutations was significantly higher in oral cavity SCCs (10 out of 27 tumors; 37%), and telomere length in AM was shorter in patients with tumors carrying TERT promoter mutations than in patients with unmutated TERT promoter cancers (p = 0.023). TERT levels in tumor did not significantly differ according to the mutational status of TERT promoter. No significant association was found between TERT promoter status and overall survival. TERT promoter mutations are most likely a late event in tumor development, occurring in a context of critically short telomeres, mostly in patients with oral cavity SCC. TERT levels, but not TERT promoter mutational status impact clinical outcome.

DNA Hypermethylation Downregulates Telomerase Reverse Transcriptase (TERT) during H. pylori-Induced Chronic Inflammation.

Helicobacter pylori infection causes chronic gastritis and is the major risk factor of gastric cancer. H. pylori induces a chronic inflammation-producing reactive oxygen species (ROS) which is a source of chromosome instabilities and contributes to the development of malignancy. H. pylori also promotes DNA hypermethylation, known to dysregulate essential genes that maintain genetic stability. The maintenance of telomere length by telomerase is essential for chromosome integrity. Telomerase reverse transcriptase (TERT) is the catalytic component of telomerase activity and an important target during host-pathogen interaction. We aimed to investigate the consequences of H. pylori on the regulation of TERT gene expression and telomerase activity. In vitro, hTERT mRNA levels and telomerase activity were analysed in H. pylori-infected human gastric epithelial cells. In addition, C57BL/6 and INS-GAS mice were used to investigate the influence of H. pylori-induced inflammation on TERT levels. Our data demonstrated that, in vitro, H. pylori inhibits TERT gene expression and decreases the telomerase activity. The exposure of cells to lycopene, an antioxidant compound, restores TERT levels in infected cells, indicating that ROS are implicated in this downregulation. In vivo, fewer TERT-positive cells are observed in gastric tissues of infected mice compared to uninfected, more predominantly in the vicinity of large aggregates of lymphocytes, suggesting an inflammation-mediated regulation. Furthermore, H. pylori appears to downregulate TERT gene expression through DNA hypermethylation as shown by the restoration of TERT transcript levels in cells treated with 5′-azacytidine, an inhibitor of DNA methylation. This was confirmed in infected mice, by PCR-methylation assay of the TERT gene promoter. Our data unraveled a novel way for H. pylori to promote genome instabilities through the inhibition of TERT levels and telomerase activity. This mechanism could play an important role in the early steps of gastric carcinogenesis.

The Potential Role of Cycloastragenol in Promoting Diabetic Wound Repair In Vitro.

Background Refractory wound healing is a severe complication of diabetes with a significant socioeconomic burden. Whereas current therapies are insufficient to accelerate repair, stem cell-based therapy is increasingly recognized as an alternative that improves healing outcomes. The aim of the present study is to explore the role of cycloastragenol (CAG), a naturally occurring compound in Astragali Radix, in ameliorating refractory cutaneous wound healing in vitro, which may provide a new insight into therapeutic strategy for diabetic wounds. Methods Human epidermal stem cells (EpSCs) obtained from nine patients were exposed to CAG, with or without DKK1 (a Wnt signaling inhibitor). A lentiviral short hairpin RNA (shRNA) system was used to establish the telomerase reverse transcriptase (TERT) and β-catenin knockdown cell line. Cell counting kit-8, scratch wound healing, and transwell migration assay were used to determine the effects of CAG in cell growth and migration. The activation of TERT, β-catenin, and c-Myc was determined using real-time qPCR and western blot analysis. Chromatin immunoprecipitation (ChIP) was performed to evaluate the associations among CAG, TERT, and Wnt/β-catenin signals. Results CAG not only promoted the proliferation and migration ability of EpSCs but also increased the expression levels of TERT, β-catenin, c-Myc. These effects of CAG were most pronounced at a dose of 0.3 μM. Notably, the CAG-promoted proliferative and migratory abilities of EpSCs were abrogated in TERT and β-catenin-silenced cells. In addition, the ChIP results strongly suggested that CAG-modulated TERT was closely associated with the activation of Wnt/β-catenin signaling. Conclusion Our data indicate that CAG is a TERT activator of EpSCs and is associated with their proliferation and migration, a role it may play through the activation of Wnt/β-catenin signaling.

Characterization of human telomerase reverse transcriptase promoter methylation and transcription factor binding in differentiated thyroid cancer cell lines.

Telomerase reverse transcriptase (TERT) activation plays an important role in cancer development by enabling the immortalization of cells. TERT regulation is multifaceted, and its promoter methylation has been implicated in controlling expression through alteration in transcription factor binding. We have characterized TERT promoter methylation, transcription factor binding, and TERT expression levels in five differentiated thyroid cancer (DTC) cell lines and six normal thyroid tissue samples by targeted bisulfite sequencing, ChIP-qPCR, and qRT-PCR. DTC cell lines express varying levels of TERT and exhibit TERT promoter methylation patterns similar to patterns seen in other telomerase positive cancer cell lines. The minimal promoter immediately surrounding the transcription start site is hypomethylated, while further upstream portions show dense methylation. In contrast, the TERT promoter in normal thyroid tissue is largely unmethylated throughout and expresses TERT minimally. Transcription factor binding is also affected by TERT mutation status. The E-twenty-six (ETS) factor GABPA exhibits TERT binding in the TERT mutant DTC cells only, and allele-specific methylation patterns at the minimal promoter were observed as well, which may indicate allele-specific factor recruitment at the minimal promoter. Furthermore, we identified binding sites for activators MYC and GSC in the hypermethylated upstream region, pointing to its possible importance in TERT regulation. Overall, TERT expression and telomerase activity depend on the interplay of multiple regulatory mechanisms including TERT promoter methylation, mutation status, and recruitment of transcription factors. This work explores of the interplay between these regulatory mechanisms and offers insight into cellular control of active telomerase in human cancer.

Polymorphisms in the telomerase complex to predict outcome in patients (pts) with metastatic colorectal cancer (mCRC): Data from TRIBE and FIRE-3 phase III trials.

566 Background: Telomere/telomerase interplay is involved in the regulation of genomic stability and cellular replicative potential. In CRC, shortening of telomeres promotes early steps of carcinogenesis but the prognostic role of telomere length is debated. High circulating levels of telomerase reverse transcriptase (TERT) appear to be a negative prognostic biomarker and polymorphisms in the telomerase RNA component (TERC) are associated with increased cancer risk. We hypothesized that genetic variants in the telomerase/telomere capping complex may predict first-line treatment outcome in mCRC pts. Methods: The impact on outcome of 21 selected SNPs within 13 genes ( TERT, TERC, CLPTM1L, TERF1/2, POT1, ACD, NOP10, NHP2, GAR1, STN1, CTC1) was analyzed through the OncoArray, a custom array manufactured by Illumina, on genomic DNA from blood samples of 451 pts enrolled in two independent randomized trials. TRIBE FOLFIRI/bevacizumab (bev) arm (n=215, mPFS/OS: 9.7/26.2 mo) served as discovery cohort, FIRE-3 FOLFIRI/bev arm (n=107, mPFS/OS: 11.5/31.4 mo) as validation and FOLFIRI/cetuximab (cet) arm (n=129, mPFS/OS: 12.8/49.8 mo) as control. Results: In the discovery cohort, pts carrying any A allele of TERT rs2075786 showed longer mPFS (11.1 vs 9.3 mo, P= .021) and OS (33.5 vs 25 mo, P= .005) compared to the G/G genotype in multivariable analysis. Same results were observed for pts carrying any T allele of CLPTM1L rs401681 compared to the C/C genotype ( P= .022). Any C allele carriers of TERC rs2293607 also showed longer mOS in multivariable analysis ( P= .041) and the A/A genotype of ACD rs6979 was associated with longer mPFS in both uni- and multivariable analysis. Interestingly, the T/T genotype of CLPTM1L rs401681 was associated with shorter mPFS (7.8 vs 13.5 mo) in the cet cohort in uni- ( P= .003) and multivariable analysis ( P= .041). In subgroup analyses based on RAS mutational status several SNPs in additional genes were associated with PFS and/or OS in different cohorts. Conclusions: Our results suggest that SNPs in core telomerase/telomere capping complex genes may have a predictive and prognostic value in mCRC pts receiving targeted first-line treatments.

Dexmedetomidine Rescues Enteric Glial Cells from Oxidative Stress-Induced Intestinal Ischemia-Reperfusion Injury Through Promoting Mitochondrial Translocation of Telomerase Reverse Transcriptase

Background: Intestinal ischemia-reperfusion injury (IRI) is a devastating complication in the perioperative period leading to systemic inflammation and multiple organ dysfunction. We aimed to determine whether dexmedetomidine protects against oxidative stress injury induced by mitochondrial translocation of telomerase reverse transcriptase (TERT) in enteric glial cells (EGCs) of a rat model after intestinal IRI and the mechanisms involved in this protection. Methods: After the rat model with intestinal IRI was established, the rats were treated with high/low dose of dexmedetomidine. The positive rate of TERT protein was detected by immunohistochemistry. The distribution and levels of TERT were measured by immunofluorescence. The levels of apoptosis-related proteins and oxidative stress injury-related factors (ROS, MDA, and GSH) were also measured. Mitochondrial membrane permeability and potential were detected using Calcein cobalt and Rhodamine 123 staining respectively. The oxidative injury of mtDNA was detected by real-time fluorescence quantitative PCR. Cell Counting Kit-8 (CCK-8) assay and flow cytometry were applied to detection of EGC viability and apoptosis. Results: Relative to normal rats, rats with intestinal IRI displayed with reduced TERT mitochondrial translocation and EGC viability, as well as elevated mitochondrial damage, oxidative stress, and EGC apoptosis. Dexmedetomidine treatment could alleviate intestinal IRI by promoting mitochondrial translocation of TERT, reducing mitochondrial damage and oxidative stress. The regulatory mechanism functioned in a dose-dependent manner. Conclusion: Dexmedetomidine restores mitochondrial translocation of TERT, thus reducing oxidative stress and mitochondrial damage in EGCs after intestinal IRI. Funding: The study was supported by a grant from the National Natural Science Foundation of China (No. 81660096). Declaration of Interest: The authors have no competing interests to declare. Ethical Approval: Our study was approved by the Institutional Review Board of the First Affiliated Hospital of Nanchang University. All animal experiments and procedures were performed in accordance with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health.

Protective effects ROS up-regulation on premature ovarian failure by suppressing ROS-TERT signal pathway.

Premature ovarian failure (POF) refers to the condition of pre-onset ovarian function failure, and is one commonly occurred disease in gynecology. Its pathogenic mechanism, however, is still unclear. Early study found decreased activity of telomerase reverse transcriptase (TERT). As an important factor to suppress TERT, oxidative stress has not been studied in POF. We, thus, investigated the role of reactive oxygen species (ROS)-TERT in POF. Rat POF model was induced by a single intraperitoneal injection of cyclophosphamide plus 12 mg/kg busulfan. Level of follicle stimulating hormone (FSH) and inhibin B was measured by enzyme-linked immunosorbent assay (ELISA), along with hematoxylin and eosin (HE) staining to confirm successful generation of models. Western blot was applied to measure TERT expression, and N-acetyl-cysteine (NAC) or TERT small interfere RNA (siRNA) was injected to suppress ROS or TERT level, followed by HE staining to observe POF condition. In POF model, ovary tissues showed atrophy, less follicles, and more follicular atresia, plus mesenchymal hyperplasia. FSH and inhibin B level were significantly up-regulated and down-regulated, respectively (p<0.05). In POF rat, ROS level was elevated (p<0.05) whilst TERT level was decreased. NAC inhibited ROS level and enhanced TERT expression. In contrast, TERT siRNA further aggravated POF condition. ROS up-regulation inhibits TERT expression, suppresses TERT activity and facilitates POF. The ROS-TERT pathway may work as the target for treating POF.

Telomerase reverse transcriptase regulates DNMT3B expression/aberrant DNA methylation phenotype and AKT activation in hepatocellular carcinoma

Telomerase reverse transcriptase (TERT)1 acts as a master regulator of cancer hallmarks, but underlying mechanisms remain incompletely understood. We show that TERT is required for the aberrant DNA methyltransferase 3 B (DNMT3B)2 expression and cancer-specific methylation in hepatocellular carcinoma (HCC)3, through which AKT is activated. TERT depletion inhibited, while its over-expression promoted DNMT3B expression in HCC cells, respectively. Mechanistically, TERT cooperates with the transcription factor Sp1 to stimulate DNMT3B transcription. The tumor suppressors PTEN and RASSF1A were de-repressed following DNMT3B inhibition in TERT-depleted HCC cells. The PTEN promoter analysis demonstrated significantly reduced methylation in these cells. TERT silencing also led to diminished global DNA methylation. The analysis of the Cancer Genome Atlas (TCGA)4 dataset showed that higher levels of TERT and DNMT3B expression predicted significantly shorter survival in HCC patients. Collectively, our findings establish TERT as an important contributor to cancer-specific DNA methylation and AKT hyperactivation in HCC cells. Given critical roles of both the aberrant DNA methylation and AKT activation in carcinogenesis, this TERT-regulated network or the TERT-DNMT3B-PTEN-AKT axis provides a biological explanation for multi-oncogenic activities of TERT and may be exploited in HCC treatment.

Telomerase reverse transcriptase induced thyroid carcinoma cell proliferation through PTEN/AKT signaling pathway

Thyroid carcinoma is the most common endocrine malignant tumor in the world, and so, there is a requirement to develop novel molecular targets for thyroid cancer diagnosis and treatment. Telomerase reverse transcriptase (TERT) was revealed to promote cell proliferation in a number of types of cell. To evaluate whether and how TERT functioned on papillary thyroid cancer (PTC) cell proliferation, the present study constructed TERT over-expression [recombined (r)TERT plasmid group] and interference [small interfering RNA (si)-TERT group] models by liposome transfection respectively to study the molecular mechanisms. The transfection efficiency was first detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting to analyze TERT levels compared with the negative control (NC) and control groups. Then MTT and carboxyfluorescein diacetate succinimidyl ester assays were performed to determine living cell proliferation and total cell proliferation respectively. Propidium iodide assay was used to detect alterations in cell cycle progression. RT-qPCR and western blotting were performed to detect associated factor variation. The results demonstrated that, following the generation of TERT overexpression or silencing PTC cells, the living cells and also total cell proliferation increased significantly in the rTERT group, and decreased significantly in siTERT group, when compared with the NC and control groups. The cell cycle was accelerated in the rTERT group, and blocked in the G1/S transition in the siTERT group. The mRNA and protein levels of P27, P53 and phosphatase and tensin homolog (PTEN) decreased significantly in the rTERP group and increased in the siTERP group, while cyclin dependent kinase 2 and Cyclin D1 increased significantly in the rTERP group and decreased in the siTERP group. The expression of cell division cycle 25A did not alter significantly. The protein levels of β-catenin and retinoblastoma were also unaltered. Protein kinase B (AKT) was detected once activated by TERT, and there were increased phosphorylated (p)-AKT protein levels in the rTERT group, and decreased p-AKT protein levels in the siTERT group. In conclusion, TERT could induce thyroid carcinoma cell proliferation mainly through the PTEN/AKT signaling pathway.

Telomere elongation protects heart and lung tissue cells from fatal damage in rats exposed to severe hypoxia

BackgroundThe effects of acute hypoxia at high altitude on the telomere length of the cells in the heart and lung tissues remain unclear. This study aimed to investigate the change in telomere length of rat heart and lung tissue cells in response to acute exposure to severe hypoxia and its role in hypoxia-induced damage to heart and lung tissues.MethodsForty male Wistar rats (6-week old) were randomized into control group (n = 10) and hypoxia group (n = 30). Rats in control group were kept at an altitude of 1500 m, while rats in hypoxia group were exposed to simulated hypoxia with an altitude of 5000 m in a low-pressure oxygen chamber for 1, 3, and 7 days (n = 10). The left ventricular and right middle lobe tissues of each rat were collected for measurement of telomere length and reactive oxygen species (ROS) content, and the mRNA and protein levels of telomerase reverse transcriptase (TERT), hypoxia-inducible factor1α (HIF-1α), and hypoxia-inducible factor1α (HIF-2α).ResultsIncreased exposure to hypoxia damaged rat heart and lung tissue cells and increased ROS production and telomere length. The mRNA and protein levels of TERT and HIF-1α were significantly higher in rats exposed to hypoxia and increased with prolonged exposure; mRNA and protein levels of HIF-2α increased only in rats exposed to hypoxia for 7 days. TERT was positively correlated with telomere length and the levels of HIF-1α but not HIF-2α.ConclusionsAcute exposure to severe hypoxia causes damage to heart and lung tissues due to the production of ROS but promotes telomere length and adaptive response by upregulating TERT and HIF-1α, which protect heart and lung tissue cells from fatal damage.

The predictive and prognostic potential of plasma telomerase reverse transcriptase (TERT) RNA in rectal cancer patients

Background:Preoperative chemoradiotherapy (CRT) followed by surgery is the standard care for locally advanced rectal cancer, but tumour response to CRT and disease outcome are variable. The current study aimed to investigate the effectiveness of plasma telomerase reverse transcriptase (TERT) levels in predicting tumour response and clinical outcome.Methods:176 rectal cancer patients were included. Plasma samples were collected at baseline (before CRT=T0), 2 weeks after CRT was initiated (T1), post-CRT and before surgery (T2), and 4–8 months after surgery (T3) time points. Plasma TERT mRNA levels and total cell-free RNA were determined using real-time PCR.Results:Plasma levels of TERT were significantly lower at T2 (P<0.0001) in responders than in non-responders. Post-CRT TERT levels and the differences between pre- and post-CRT TERT levels independently predicted tumour response, and the prediction model had an area under curve of 0.80 (95% confidence interval (CI) 0.73–0.87). Multiple analysis demonstrated that patients with detectable TERT levels at T2 and T3 time points had a risk of disease progression 2.13 (95% CI 1.10–4.11)-fold and 4.55 (95% CI 1.48–13.95)-fold higher, respectively, than those with undetectable plasma TERT levels.Conclusions:Plasma TERT levels are independent markers of tumour response and are prognostic of disease progression in rectal cancer patients who undergo neoadjuvant therapy.

Curcumin Affects Adipose Tissue-Derived Mesenchymal Stem Cell Aging Through TERT Gene Expression

Aging and losing cell survival is one of the main problems in cell therapy. Aging of Mesenchymal Stem Cells (MSCs) is associated with a rise in intracellular reactive oxygen species, decrease in telomerase reverse transcriptase (TERT) expression and finally eroded telomere ends. Given that the production of free radicals in the aging process is effective, the use of antioxidants can help in scavenging free radicals and prevent the aging of cells. The aim of this study is to evaluate the effects of curcumin on proliferation, aging and TERT expression of rat adipose tissue-derived stem cells (rADSC). rADSCs were isolated from inguinal rat adipose tissue and their viabilities were assessed by MTT after exposure to different concentrations of curcumin. Flow-cytometry was performed for investigating the cell surface markers. Adipogenic and osteogenic differentiation were carried out to evaluate the pluripotency of rADSCs. Telomerase expression and percentage of senescent cells were evaluated using real-time PCR and senescence-associated β-galactosidase activity, respectively. The results demonstrated significant proliferation of rADSCs after 48 h treatment with 1 and 5 µM curcumin. Additionally, these concentrations could significantly reduce the population doubling time and aging of rADSCs at different passages. The findings of SA-ß-gal staining showed that curcumin significantly decreased the number of senescent cells in the 5 and 7 cell passages. Moreover, expression levels of TERT increased in the presence of 1 and 5 µM curcumin than control group (P<0.001). As a conclusion, curcumin may be a good candidate to improve lifespan of rADSCs through promoting TERT gene expression.

Differential decrease in soluble and DNA-bound telomerase in senescent human fibroblasts.

The role of telomere shortening in the induction of replicative cellular senescence (CS) is well known and as a result, the involvement of telomerase and in particular its catalytic subunit, the telomerase reverse transcriptase (TERT) in CS has also been investigated. However, the majority of studies were conducted on cells that generally express high levels of TERT (cancer and immortalized cells) while the role of telomerase in CS in normal cells has been investigated to a much lesser extent. In particular, it was reported that active TERT is expressed in early passages of cultured human keratinocytes but rapidly diminished towards entry to CS, without telomere shortening. With the putative importance of TERT/telomerase in CS and the aging process in mind, we investigated the expression of TERT and telomerase activity in primary cultures of adult human dermal fibroblasts (HDFs) in the in vitro model of replicative CS. We found that (i) HDFs expressed active TERT; (ii) TERT protein levels and telomerase activity were markedly decreased in senescent HDFs; and (iii) the reduction of TERT in the soluble fraction was more pronounced than in the DNA-bound one. The results suggest the importance of the non-canonical (telomere-unrelated) functions of TERT in cellular senescence.