Human artificial chromosome carrying 3p21.3-p22.2 region suppresses hTERT transcription in oral cancer cells.

Telomerase is a ribonucleoprotein ribonucleic enzyme that elongates telomere repeat sequences at the ends of chromosomes and contributes to cellular immortalization. The catalytic component of telomerase, human telomerase reverse transcriptase (hTERT), has been observed to be reactivated in immortalized cells. Notably, most cancer cells have been found to have active hTERT mRNA transcription, resulting in continuous cell division, which is crucial for malignant transformation. Therefore, discovering mechanisms underlying the regulation of hTERT transcription is an attractive target for cancer-specific treatments.Loss of heterozygosity (LOH) of chromosome 3p21.3 has been frequently observed in human oral squamous cell carcinoma (OSCC). Moreover, we previously reported that HSC3 OSCC microcell hybrid clones with an introduced human chromosome 3 (HSC3#3) showed inhibition of hTERT transcription compared with the parental HSC3 cells. This study examined whether hTERT transcription regulators are present in the 3p21.3 region. We constructed a human artificial chromosome (HAC) vector (3p21.3-HAC) with only the 3p21.3-p22.2 region and performed functional analysis using the 3p21.3-HAC. HSC3 microcell hybrid clones with an introduced 3p21.3-HAC exhibited significant suppression of hTERT transcription, similar to the microcell hybrid clones with an intact chromosome 3. In contrast, HSC3 clones with truncated chromosome 3 with deletion of the 3p21.3 region (3delp21.3) showed no effect on hTERT expression levels. These results provide direct evidence that hTERT suppressor gene(s) were retained in the 3p21.3 region, suggesting that the presence of regulatory factors that control telomerase enzyme activity may be involved in the development of OSCC.

Obesity-Senescence-Breast Cancer: Clinical Presentation of a Common Unfortunate Cycle.

There are few convincing studies establishing the relationship between endogenous factors that cause obesity, cellular aging, and telomere shortening. Without a functional telomerase, a cell undergoing cell division has progressive telomere shortening. While obesity influences health and longevity as well as telomere dynamics, cellular senescence is one of the major drivers of the aging process and of age-related disorders. Oxidative stress induces telomere shortening, while decreasing telomerase activity. When progressive shortening of telomere length reaches a critical point, it triggers cell cycle arrest leading to senescence or apoptotic cell death. Telomerase activity cannot be detected in normal breast tissue. By contrast, maintenance of telomere length as a function of human telomerase is crucial for the survival of breast cancer cells and invasion. Approximately three-quarters of breast cancers in the general population are hormone-dependent and overexpression of estrogen receptors is crucial for their continued growth. In obesity, increasing leptin levels enhance aromatase messenger ribonucleic acid (mRNA) expression, aromatase content, and its enzymatic activity on breast cancer cells, simultaneously activating telomerase in a dose-dependent manner. Meanwhile, applied anti-estrogen therapy increases serum leptin levels and thus enhances leptin resistance in obese postmenopausal breast cancer patients. Many studies revealed that shorter telomeres of postmenopausal breast cancer have higher local recurrence rates and higher tumor grade. In this review, interlinked molecular mechanisms are looked over between the telomere length, lipotoxicity/glycolipotoxicity, and cellular senescence in the context of estrogen receptor alpha-positive (ERα+) postmenopausal breast cancers in obese women. Furthermore, the effect of the potential drugs, which are used for direct inhibition of telomerase and the inhibition of human telomerase reverse transcriptase (hTERT) or human telomerase RNA promoters as well as approved adjuvant endocrine therapies, the selective estrogen receptor modulator and selective estrogen receptor down-regulators are discussed.

Increased Prolylcarboxypeptidase Expression Can Serve as a Biomarker of Senescence in Culture.

Prolylcarboxypeptidase (PRCP, PCP, Lysosomal Pro-X-carboxypeptidase, Angiotensinase C) controls angiotensin- and kinin-induced cell signaling. Elevation of PRCP appears to be activated in chronic inflammatory diseases [cardiovascular disease (CVD), diabetes] in proportion to severity. Vascular endothelial cell senescence and mitochondrial dysfunction have consistently been shown in models of CVD in aging. Cellular senescence, a driver of age-related dysfunction, can differentially alter the expression of lysosomal enzymes due to lysosomal membrane permeability. There is a lack of data demonstrating the effect of age-related dysfunction on the expression and function of PRCP. To explore the changes in PRCP, the PRCP-dependent prekallikrein (PK) pathway was characterized in early- and late-passage human pulmonary artery endothelial cells (HPAECs). Detailed kinetic analysis of cells treated with high molecular weight kininogen (HK), a precursor of bradykinin (BK), and PK revealed a mechanism by which senescent HPAECs activate the generation of kallikrein upon the assembly of the HK-PK complex on HPAECs in parallel with an upregulation of PRCP and endothelial nitric oxide (NO) synthase (eNOS) and NO formation. The NO production and expression of both PRCP and eNOS increased in early-passage HPAECs and decreased in late-passage HPAECs. Low activity of PRCP in late-passage HPAECs was associated with rapid decreased telomerase reverse transcriptase mRNA levels. We also found that, with an increase in the passage number of HPAECs, reduced PRCP altered the respiration rate. These results indicated that aging dysregulates PRCP protein expression, and further studies will shed light into the complexity of the PRCP-dependent signaling pathway in aging.

Association of human telomerase reverse transcriptase promoter mutation with unfavorable prognosis in glioma: A systematic review and meta-analysis.

Background: Glioma is one of the most malignant and aggressive tumors, with an extremely poor prognosis. Human telomerase reverse transcriptase (hTERT) promoter mutation is regarded as a risk factor in tumor growth. Although the prevalence of hTERT promoter (pTERT) mutation in gliomas has been investigated, the results are inconsistent. This meta-analysis aims to investigate the prognostic value of hTERT in glioma patients and its interaction with other biomarkers. Materials and Methods: We searched 244 citations from four databases: PubMed (2000-2021), Web of Science (2000-2021), Embase (2010-2021), and Cochrane Library (2000-2021) with 28 articles included. Results: We calculated hazard ratios (HRs) using the random effect model and the pooled result suggested that TERT promoter mutation predicted poorer overall survival (HR: 1.53, 95% confidence interval [CI]: 1.34-1.75, P < 0.001, I2: 49.9%, pheterogeneity:0.002) and progression-free survival (HR: 1.55, 95% CI: 1.27-1.88, P < 0.001, I2: 0.0%, pheterogeneity: 0.473). For subgroup analysis, we analyzed multiple factors including iso-citrate dehydrogenase (IDH) genotype, age, diagnosis, pTERT region, so as to locate the sources of heterogeneity. Interestingly, in IDH mutant subgroup, pTERT mutation became a beneficial prognostic factor (HR: 0.73, 95% CI: 0.57-0.93, I2: 22.3%, pheterogeneity: 0.277), which is contrary to the results in pooled analysis. Conclusion: In general, pTERT mutation may result in shorter survival time in glioma patients, but longer survival time when glioma patients are combined with IDH mutation.

Low-dose telomerase is required for the expansion and migration of placental mesenchymal stem cells.

Telomerase is activated in pluripotent stem cells and the majority of tumors and is postulated to be necessary for the acquisition of self-renewal and long-term proliferation. Placental mesenchymal stem cells (PMSCs) are very promising in regenerative medicine owing to their great capacity for self-renewal and differentiation potential. Although telomerase activity in the placenta is naturally low, it remains unclear whether telomerase activity is required for the properties of PMSCs. We herein isolated and identified a PMSC line carrying compound heterozygote variations in hTERT (DC-PMSCs) that lost telomerase activity, showed a typical surface phenotype of MSCs, and was able to differentiate into multiple cell lineages. DC-PMSCs showed accelerated telomere erosion, advanced senescence, and diminished migratory and invasive capabilities. RNA-seq identified 361 differentially expressed genes between DC-PMSCs and control groups, most of which were enriched in extracellular matrix, ECM, and related pathways. Knockdown of telomerase subunit genes in PMSCs confirmed the phenotype and attenuated the expression of extracellular matrix components and matrix metalloproteases. Our results suggest that low telomerase activity is not essential for the properties of MSCs, but that it is required for community maintenance and for the migration of PMSCs.

[Anti-Tumor Effect of a Novel Oncolytic Virus Based on Chimpanzee Adenovirus Type 6].

OBJECTIVE: To construct, with chimpanzee adenovirus serotype 6 (AdC6) as the vector, a novel oncolytic adenovirus, enabling it to selectively replicate intratumorally, to test its tumor suppressive effect in vitro and in vivo, and to study its oncolytic mechanism. METHODS: Based on the AdC6 vector, the human telomerase reverse transcriptase (hTERT) promoter was used to drive the expression of E1A, the adenovirus replication-related gene, and the recombinant oncolytic virus AdC6-htertΔE1A-ΔE3 was thus obtained. The oncolytic virus AdC6-htertE1A-ΔE3 (CSF 2) expressing granulocyte macrophage colony-stimulating factor (GM-CSF/CSF 2) and replication-deficient adenovirus AdC6-ΔE1-ΔE3 were constructed by homologous recombination, respectively. The recombinant adenovirus was packaged in HEK293 cells, purified and then identified with restriction enzyme digestion. Different types of tumor cells, including RD, SW-620, HeLa, Huh7, RM-1 and MC-38 were infected with the three adenoviruses. Twenty-four hours after infection, Western blot was used to determine the expression of CSF 2 24 hours after infection. CCK8 assay was used to determine the survival rate of tumor cells 72 hours after infection. HeLa cells were infected with the three adenoviruses, and the expression levels of apoptosis signaling pathway proteins were examined with Western blot at 12 h, 24 h, and 48 h. C57BL/6 mice were subcutaneously injected with cell suspension containing 1×10 6 MC38 murine colon cancer cells and RM-1 murine prostate cancer cells to construct two tumor-bearing mice models. The tumor-bearing mice were divided into 4 groups, receiving intratumoral injection of 50 µL of PBS, AdC6-ΔE1-ΔE3 (1×10 8 PFU), AdC6-htertE1A-ΔE3 (1×10 8PFU), and AdC6-htertE1A-ΔE3 (CSF 2) (1×10 8 PFU), respectively. When the tumor size of PBS group reached 2 500 mm 3, all the mice were sacrificed and the tumor tissue was collected for TUNEL staining. Then, apoptosis-positive cells were observed and counted under a microscope. RESULTS: Restriction digestion revealed that the oncolytic viruses AdC6-htertE1A-ΔE3, AdC6-htertE1A-ΔE3 (CSF 2) and AdC6-ΔE1-ΔE3 were successfully constructed. Western blot confirmed that AdC6-htertE1A-ΔE3 (CSF 2) could infect different tumor cells and stably express CSF 2, the exogenous gene. CCK8 results showed that AdC6-htertE1A-ΔE3 and AdC6-htertE1A-ΔE3 (CSF 2) had obvious killing effects on RD, SW-620, HeLa, Huh7, RM-1and MC-38. Compared with the replication-deficient adenovirus AdC6-ΔE1-ΔE3, AdC6-htertE1A-ΔE3 and AdC6-htertE1A-ΔE3 (CSF 2) at a multiplicity of infection of 100 MOI had extremely obvious killing effects on tumor cells ( P<0.05). Western blot showed that AdC6-htertE1A-ΔE3 and AdC6-htertE1A-ΔE3 (CSF 2) induced tumor cell apoptosis by activating the P53-dependent pathway. Injection of oncolytic virus in tumor-bearing mouse models of prostate cancer and colorectal cancer could significantly inhibit the tumor growth and even clear the tumor. CONCLUSION: Oncolytic virus based on AdC6 could eliminate tumor in vivoand in vitro through mechanisms that induced apoptosis, showing great potential for the treatment of tumors.

Implications of risk conferred by 5p15.33 loci genetic variants; human telomerase reverse transcriptase rs2736098 and rs2736100 in predisposition of bladder cancer.

Background: The polymorphic variations of human telomerase reverse transcriptase (hTERT) gene play an important role in predisposition to carcinogenesis. The current study aimed to elucidate the genetic predisposition to bladder cancer in two important variants, rs2736098 and rs2736100 of hTERT gene. Materials and methods: Confirmed 130 patients of bladder cancer and 200 healthy controls were genotyped by PCR-RFLP to determine different variants of hTERT rs2736098 and rs2736100. Results: hTERT rs2736098 homozygous variant AA genotype frequency was observed to significantly differ 2-fold between cases and controls (26.15% vs. 13.5%) (p = 0.02). In addition, rare 'A' allele significantly differed among two groups (cases: 47% versus controls: 39%: p = 0.03). hTERT rs2736098 was observed to be presented significantly more in high stage tumors (p = 0.02). hTERT rs2736100 genotype AA or variant allele A showed no significant difference between cases and controls. Haplotype CA displayed significantly different pattern of frequency as 0.5 in cases as compared to 0.16 in controls (p < 0.0001). Combination of variant A/G haplotype frequency implicated more in cases than in controls (0.34 vs. 0.14, p = 0.001). Conclusions: It is concluded that hTERT rs2736098 polymorphic variant has a vital role to confer a strong risk to bladder cancer in our population. Further, hTERT haplotypes CA and AG inhTERT could prove to be a promising tool to screen the risk for bladder cancer.

Knockdown of human telomerase reverse transcriptase induces apoptosis in cervical cancer cell line.

Background & objectives: : Human telomerase reverse transcriptase (hTERT) is the catalytic subunit of telomerase enzyme that maintains telomere ends by the addition of telomeric repeats to the ends of chromosomal DNA, and that may generate immortal cancer cells. Hence, the activity of telomerase is raised in cancer cells including cervical cancer. The present study aimed to validate the unique siRNA loaded chitosan coated poly-lactic-co-glycolic acid (PLGA) nanoparticle targeting hTERT mRNA to knock down the expression of hTERT in HeLa cells. Methods: : The siRNA loaded chitosan coated polylactic-co-glycolic acid (PLGA) nanoparticles were synthesized by double emulsion solvent diffusion method. The characterization of nano-formulation was done to determine efficient siRNA delivery. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot were performed to evaluate silencing efficiency of nano-formulation. Results: :Size, zeta potential and encapsulation efficiency of nanoparticles were 249.2 nm, 12.4 mV and 80.5 per cent, respectively. Sustained release of siRNA from prepared nanoparticle was studied for 72 h by ultraviolet method. Staining assays were performed to confirm senescence and apoptosis. Silencing of hTERT mRNA and protein expression were analyzed in HeLa cells by RT-PCR and Western blot. Interpretation & conclusions: : The findings showed that biodegradable chitosan coated PLGA nanoparticles possessed an ability for efficient and successful siRNA delivery. The siRNA-loaded PLGA nanoparticles induced apoptosis in HeLa cells. Further studies need to be done with animal model.

Correlation of human telomerase reverse transcriptase single nucleotide polymorphisms with in vitro fertilisation outcomes.

PURPOSE: To explore whether it is possible to predict the number and quality of the embryo using a few particular hTERT SNPs. METHODS: We included 997 Han Chinese women who were genetically unrelated and underwent assisted reproduction using IVF from September 2014 to December 2015. DNA was genotyped by using TaqMan real-time quantitative PCR. RESULTS: Among the 997 patients, individuals with the CC genotype of rs2075786 had a significantly lower number of good-quality embryos than those with the TT+TC genotypes. Compared with the CT+CC genotype carriers, patients carrying the TT genotype of rs2853677 had a significantly lower number of oocytes retrieved, mature oocytes and available embryos. Among the 750 patients aged ≤ 35 years, individuals with the AA+AG genotypes of rs2853691 had a significantly higher number of good-quality embryos than those with the GG genotype. The haplotype analysis showed that the TTTG (rs2853672/rs2853669/rs2735940/rs2736108) haplotype was more likely to lead to more than three good-quality embryos in patients aged ≤ 35 years. CONCLUSIONS: Our study suggests that the hTERT SNP is associated with IVF outcomes.

Higher expression of human telomerase reverse transcriptase in productively-infected CD4 cells possibly indicates a mechanism for persistence of the virus in HIV infection.

Mechanisms involved in survival of productively-infected memory CD4+cells after initial antigenic stimulation and their subsequent reversion to the resting state are critical for the development of a predominant replication-competent HIV reservoir. These mechanisms may also counter their elimination after HIV reactivation through latency-reversing agents (LRA). Thus, their evaluation is critical when using an appropriate HIV latency model that recapitulates the predominant replication-competent HIV reservoir to develop strategies for HIV eradication. The model for evaluating the possible survival mechanisms after T cell receptor (TCR) stimulation was developed by infecting memory CD4+cells with an HIV-1C primary isolate and cytokine secretion and gene expression patterns determined. Infected cells showed compromised functionality as evident from 6.8-fold lower secretion of IL-2 than from uninfected control cells. After TCR stimulation, the infected cells showed significantly higher fold increases in CD27 and CCR5 and smaller increases in CD5 mRNA over baseline values. Because CD27 expression may influence telomerase activity through AKT phosphorylation, CD27, human telomerase reverse transcriptase (hTERT) and pAKT expression in productively-infected cells from HIV-infected patients was evaluated by flow cytometry. HIV harbored in memory CD4+ cells was reactivated by HIV-1 envelope peptides, which have been shown to act as effective LRA. P24+CD4+cell showed significantly higher expression of CD27, hTERT and pAKT than P24-CD4+cells. These findings indicate compromised functionality of HIV-infected cells after TCR stimulation, which may interfere with their elimination by the immune system. They also indicate that pAKT and hTERT induction are possible survival mechanisms of productively-infected CD4+cells.

Immune responses and long-term disease recurrence status after telomerase-based dendritic cell immunotherapy in patients with acute myeloid leukemia.

BACKGROUND: Telomerase activity in leukemic blasts frequently is increased among patients with high-risk acute myeloid leukemia (AML). In the current study, the authors evaluated the feasibility, safety, immunogenicity, and therapeutic potential of human telomerase reverse transcriptase (hTERT)-expressing autologous dendritic cells (hTERT-DCs) in adult patients with AML. METHODS: hTERT-DCs were produced from patient-specific leukapheresis, electroporated with an mRNA-encoding hTERT and a lysosomal-targeting sequence, and cryopreserved. A total of 22 patients with a median age of 58 years (range, 30-75 years) with intermediate-risk or high-risk AML in first or second complete remission (CR) were enrolled. hTERT-DCs were generated for 24 patients (73%). A median of 17 intradermal vaccinations (range, 6-32 intradermal vaccinations) containing 1×107 cells were administered as 6 weekly injections followed by 6 biweekly injections. A total of 21 patients (16 in first CR, 3 in second CR, and 2 with early disease recurrence) received hTERT-DCs. RESULTS: hTERT-DCs were well tolerated with no severe toxicities reported, with the exception of 1 patient who developed idiopathic thrombocytopenic purpura. Of the 19 patients receiving hTERT-DCs in CR, 11 patients (58%) developed hTERT-specific T-cell responses that primarily were targeted toward hTERT peptides with predicted low human leukocyte antigen (HLA)-binding affinities. With a median follow-up of 52 months, 58% of patients in CR (11 of 19 patients) were free of disease recurrence at the time of their last follow-up visit; 57% of the patients who were aged ≥60 years (4 of 7 patients) also were found to be free of disease recurrence at a median follow-up of 54 months. CONCLUSIONS: The generation of hTERT-DCs is feasible and vaccination with hTERT-DCs appears to be safe and may be associated with favorable recurrence-free survival. Cancer 2017;123:3061-72. © 2017 American Cancer Society.

TNF-α-induced IL-6 and MMP-9 expression in immortalized ameloblastoma cell line established by hTERT.

OBJECTIVE: Ameloblastoma (AM) shows locally invasive behaviour. However, biological investigations regarding regulation of gene expression associated with AM pathological features are difficult to perform, because AM cells can be passaged for a few generations due to senescence. We report a newly established immortalized AM cell line, AMB cells, by transfection with human telomerase reverse transcriptase (hTERT). Furthermore, we examined whether TNF-α modulates bone resorption-related genes, IL-6 and MMP-9 in cooperation with TGF-ß or IFN-γ. MATERIALS AND METHODS: Following transfection of an hTERT expression vector into AM cells using a non-viral method, the effects of cytokines on the expressions of IL-6 and MMP-9 mRNA were examined using real-time PCR. TNF-α-induced NF-κB activity was examined by western blotting and transcription factor assays. RESULTS: AMB cells continued to grow for more than 100 population doublings. Stimulation with TNF-α increased IL-6 and MMP-9 mRNA expressions, as well as NF-κB activation. Furthermore, TGF-ß and IFN-γ dramatically increased TNF-α-mediated expressions of MMP-9 and IL-6 mRNA, respectively, while those responses were suppressed by NF-κB inhibitor. CONCLUSION: We established an immortalized AM cell line by hTERT transfection. TNF-α-mediated regulation of MMP-9 and IL-6 via NF-κB may play an important role in the pathological behaviour of AMs, such as bone resorption.

The correlations between DNA methylation and polymorphisms in the promoter region of the human telomerase reverse transcriptase (hTERT) gene with postoperative recurrence in patients with thyroid carcinoma (TC).

BACKGROUND: This study aims at exploring the correlations between DNA methylation and polymorphisms in the promoter region of the human telomerase reverse transcriptase (hTERT) gene and postoperative recurrence in patients with thyroid carcinoma (TC). METHODS: A total of 312 patients diagnosed with TC were chosen for the study and categorized into recurrence (n = 75) and non-recurrence (n = 237) groups. The hTERT rs2736100 and rs2736098 polymorphisms were detected by performing polymerase chain reaction-restriction fragment length polymorphism. DNA methylation in the promoter region of hTERT gene was evaluated by pyrosequencing. A telephonic and/or outpatient follow-up was conducted for all patients. The correlations of DNA methylation and polymorphisms in the promoter region of hTERT with postoperative recurrence of TC patients underwent analysis. RESULTS: The patient in the recurrence group showed evidently different pathological types and tumor stages in comparison to the non-recurrence group. The GG genotype of hTERT rs2736100 might increase the recurrence risk of TC patients. No correlations between hTERT rs2736098 polymorphisms and recurrence risk were observed. Compared to the TT + TG genotype frequency, the rs2736100 GG genotype frequency increased in patients without multicentricity, patients with extrathyroidal invasion, patients with lymph node metastasis, patients with undifferentiated carcinoma, and patients in the III + IV stage. The recurrence group showed significantly higher DNA methylation level compared to the non-recurrence group. The DNA methylation level was closely associated to tumor stage and lymph node metastasis of TC patients in the recurrence group. CONCLUSIONS: The DNA methylation and rs2736100 polymorphisms in the promoter region of hTERT gene might be in correlation to postoperative recurrence of TC patients.

Alternative Splicing of hTERT Pre-mRNA: A Potential Strategy for the Regulation of Telomerase Activity.

The activation of telomerase is one of the key events in the malignant transition of cells, and the expression of human telomerase reverse transcriptase (hTERT) is indispensable in the process of activating telomerase. The pre-mRNA alternative splicing of hTERT at the post-transcriptional level is one of the mechanisms for the regulation of telomerase activity. Shifts in splicing patterns occur in the development, tumorigenesis, and response to diverse stimuli in a tissue-specific and cell type-specific manner. Despite the regulation of telomerase activity, the alternative splicing of hTERT pre-mRNA may play a role in other cellular functions. Modulating the mode of hTERT pre-mRNA splicing is providing a new precept of therapy for cancer and aging-related diseases. This review focuses on the patterns of hTERT pre-mRNA alternative splicing and their biological functions, describes the potential association between the alternative splicing of hTERT pre-mRNA and telomerase activity, and discusses the possible significance of the alternative splicing of the hTERT pre-mRNA in the diagnosis, therapy, and prognosis of cancer and aging-related diseases.

Telomerase reverse transcriptase induces basal and amino acid starvation-induced autophagy through mTORC1.

Telomerase is a reverse transcriptase that consists of the telomerase RNA component (TERC) and the reverse transcriptase catalytic subunit (TERT) and specializes in the elongation of telomere ends. New evidence suggests that beyond classical telomere maintenance, TERT also possesses telomere length-independent functions that are executed via interaction with other binding proteins. One such reported TERT-interacting proteins is mTOR, a master nutrient sensor that is upregulated in several cancers; however, the physiological implications of the TERT-mTOR interaction in normal cellular processes as well as in tumorigenesis are poorly understood. Here, we report that TERT inhibits the kinase activity of mTOR complex 1 (mTORC1) in multiple cell lines, resulting in the activation of autophagy under both basal and amino acid-deprived conditions. Furthermore, TERT-deficient cells display the inability to properly execute the autophagy flux. Functionally, TERT-induced autophagy provides a survival advantage to cells in nutrient-deprived conditions. Collectively, these findings support a model in which gain of TERT function modulates mTORC1 activity and induces autophagy, which is required for metabolic rewiring to scavenge the nutrients necessary for fueling cancer cell growth in challenging tumor microenvironments.

Generation and characterization of bovine bone marrow-derived macrophage cell line.

Macrophages, as the forefront of innate immune defense, have an important role in the host responses to mycobacterial infection. Therefore, a stable macrophage cell line is needed for future bovine immune system research on the bacterial infection. In this study, we established a bovine macrophage cell line by introducing the human telomerase reverse transcriptase (hTERT) gene into bovine bone marrow-derived macrophages (bBMMs). The TERT-bBMMs cells expressed macrophage surface antigen (CD11b, CD282) and upregulated expression of the cytokines IL-1ß, IL-6, IL-10, IL-12, TNF-α in response to bacterial invasion. These results demonstrate that this cell line provide reliable cell model system for future studies on interactions between the bovine macrophages and Mycobacterium tuberculosis.

Declined hTERT expression of peripheral blood CD4(+) T cells in oral lichen planus correlated with clinical parameter.

BACKGROUND: Oral lichen planus (OLP) is a chronic, T-cell-mediated inflammatory autoimmune disease. Human telomerase reverse transcriptase (hTERT), a catalytic subunit bearing the enzymatic activity of telomerase, may have a unique function in regulating the activation, proliferation, and function of T lymphocytes. The goal of this study was to investigate the expression of hTERT in CD4(+) and CD8(+) T cells from patients with OLP and its correlation with clinical parameter. METHODS: The disease severity of OLP was assessed by RAE (reticular, atrophic, erosive) scoring system. Expressions of hTERT in CD4(+) T cells and CD8(+) T cells isolated from peripheral blood of patients with OLP were detected by real-time PCR, and their correlations with clinical features were analyzed. RESULTS: hTERT mRNA levels in CD4(+) T cells of OLP were significantly lower than that of controls, while the levels in CD8(+) T cells showed no statistical difference. The expression of hTERT in CD4(+) T cells and CD8(+) T cells was neither associated with disease severity nor gender. CD4(+) T cells of OLP patients with the age ≤50 had markedly decreased hTERT levels compared with controls, but CD8(+) T cells did not. CONCLUSIONS: A divergent hTERT pattern between CD4(+) and CD8(+) T cells was implicated in OLP. Decreased hTERT in CD4(+) T cells might be responsible for the immune dysfunction in OLP.

Reversible immortalization of sheep fetal fibroblast cells by tetracycline-inducible expression of human telomerase reverse transcriptase.

OBJECTIVES: To achieve reversible immortalization of cells, we design a modified tetracycline-inducible expression (Tet-on) system to conditionally regulate the ectopic expression of human telomerase reverse transcriptase (hTERT) in primary cells. RESULTS: The hTERT gene, hygromycin-resistant gene and all essential elements for achieving tetracycline induction were combined into a single plasmid vector. Sheep fetal fibroblast cells were transfected with the vector and four putative immortalized cell clones were obtained via induction of hTERT expression by doxycycline. These immortalized cells maintained a normal karyotype and showed no transformed phenotype after 250 days continuous culture. When hTERT expression was switched off by withdrawal of doxycycline, the immortalized cells reverted to a normal proliferative state and eventually senesced after limited divisions. CONCLUSIONS: This single-plasmid based Tet-on inducible hTERT expression system can be applied for reversible immortalization of animal cells.

Involvement of transcription repressor Snail in the regulation of human telomerase reverse transcriptase (hTERT) by transforming growth factor-ß.

Human telomerase reverse transcriptase (hTERT), a catalytic subunit of telomerase, is the primary determinant for telomerase enzyme activity, which has been associated with cellular immortality. Expression of the hTERT gene is regulated by various extracellular (external) stimuli and is aberrantly up-regulated in more than 90% of cancers. Here we show that hTERT gene expression was repressed in response to transforming growth factor-ß (TGF-ß) by a mechanism dependent on transcription factors Snail and c-Myc. TGF-ß activated Snail and down-regulated c-Myc gene expression. In addition, ectopic expression of Snail strongly inhibited hTERT promoter activity, although co-expression of c-Myc abrogated this effect. Chromatin immunoprecipitation (ChIP) analysis revealed that TGF-ß decreased c-Myc occupancy and dramatically increased recruitment of Snail to the E-box motifs of the hTERT promoter, thereby repressing hTERT expression. Our findings suggest a dynamic alteration in hTERT promoter occupancy by Snail and c-Myc is the mechanistic basis for TGF-ß-mediated regulation of hTERT.

Stromal cell-derived factor-1α prevents endothelial progenitor cells senescence and enhances re-endothelialization of injured arteries via human telomerase reverse transcriptase.

Recent studies have suggested that endothelial progenitor subpopulation (EPCs) number and activity were associated with EPCs senescence. Our previous study had shown that stromal cell-derived factor-1alpha (SDF-1α) could prevent EPCs senescence, which may be via telomerase. In this study, we further investigated the role of human telomerase reverse transcriptase (h-TERT) on the protective effect of SDF-1α against senescence. Knockdown h-TERT abrogated the protective effect of SDF-1α and abolished the effects of SDF-1α on migration and proliferation. Moreover, it inhibited EPCs recruitment. In conclusion, h-TERT served a critical role in the progress that SDF-1α prevented EPCs senescence and enhanced re-endothelialization of the injured arteries.