hTERT mRNA Research Articles

Expression of human telomerase reverse transcriptase mRNA in the peripheral blood of gallbladder carcinoma patients

Objective To study the human telomerase reverse transcriptase (hTERT) mRNA in peripheral blood of patients with gallbladder carcinoma and its clinical significance.Methods Fifty cases of gallbladder cancer (GBC group),50 cases of adenomatous polyps (AMP group) and 50 normal volunteers (control group) were selected.The expression of hTERT mRNA in peripheral blood was detected by using real-time fluorescent quantitative polymerase chain reaction (FQ-PCR).Results The positive rate of hTERT mRNA in GBC group (66％) was significantly higher than in AMP group (14％) (P ＜ 0.05),and that in AMP group was higher than in control group (P ＜ 0.05).There was significant difference in the hTERT mRNA expression between T3 + T4 and T1 + T2 or between negative and positive lymph nodes (P ＜ 0.05).Conclusion The hTERT mRNA expression in peripheral blood of GBC was significantly increased,and associated with depth of invasion and lymph node metastasis. Key words: Gallbladder; Human telomerase reverse transcriptase; Polymerase chain reaction

Prognostic significance of telomere maintenance mechanisms in pediatric high-grade gliomas

Children with high-grade glioma, including diffuse intrinsic pontine glioma (DIPG), have a poor prognosis despite multimodal therapy. Identifying novel therapeutic targets is critical to improve their outcome. We evaluated prognostic roles of telomere maintenance mechanisms in children with HGG, including DIPG. A multi-institutional retrospective study was conducted involving 50 flash-frozen HGG (35 non-brainstem; 15 DIPG) tumors from 45 children (30 non-brainstem; 15 DIPG). Telomerase activity, expression of hTERT mRNA (encoding telomerase catalytic component) and TERC (telomerase RNA template) and alternative lengthening of telomeres (ALT) mechanism were assayed. Cox Proportional Hazard regression analyses assessed association of clinical and pathological variables, TERC and hTERT levels, telomerase activity, and ALT use with progression-free or overall survival (OS). High TERC and hTERT expression was detected in 13/28 non-brainstem HGG samples as compared to non-neoplastic controls. High TERC and hTERT expression was identified in 13/15 and 11/15 DIPG samples, respectively, compared to controls. Evidence of ALT was noted in 3/11 DIPG and 10/19 non-brainstem HGG specimens. ALT and telomerase use were identified in 4/19 non-brainstem HGG and 2/11 DIPG specimens. In multivariable analyses, increased TERC and hTERT levels were associated with worse OS in patients with non-brainstem HGG, after controlling for tumor grade or resection extent. Children with HGG and DIPG, have increased hTERT and TERC expression. In children with non-brainstem HGG, increased TERC and hTERT expression levels are associated with a worse OS, making telomerase a promising potential therapeutic target in pediatric HGG.

Evaluation of MUC1, CK20, and hTERT expression in peripheral blood of gastrointestinal cancer patients in search of diagnostic criteria

The goal of this study was to identify the optimal marker or marker combinations for detection of gastrointestinal malignancies using reverse-transcriptase polymerase chain (RT-PCR) reaction. To detect the presence of tumors, we analyzed mucin 1 (MUC1), cytokeratin 19 (CK19), cytokeratin 20 (CK20), and human telomerase reverse transcriptase (hTERT) mRNA in the peripheral blood of 31 patients with gastrointestinal (esophagus, stomach, and colorectal) cancer and 30 healthy individuals. In RT-PCR analysis of the peripheral blood, 77.4% (24/31), 61.29% (19/31), and 45.16% (14/31) of cancer patients were positive for MUC1, CK20, and hTERT mRNA, respectively. According to our results, any one of these mRNA markers is a predictor of the presence of gastrointestinal tumors (P < 0.001) and colorectal tumors (P < 0.05). However, they did not have predictive potential for presence of metastasis in gastrointestinal tumors. As a result, combination of these 3 tumor-specific mRNA markers would increase the detection rate and may be clinically helpful in predicting tumor presence.

Expression of Telomerase Reverse Transcriptase during the Malignant Transformation of Cadmium-Induced Cells

The objective of the present study was to investigate human telomerase reverse transcriptase (hTERT) mRNA and protein expressions during the cadmium chloride-induced malignant transformation of human bronchial epithelial (16HBE) cells. Fluorescence quantitative PCR (FQ-PCR) and Western blot analyses were performed to detect the hTERT mRNA and protein expressions in normal 16HBE cells, cadmium chloride-transformed 16HBE cells, and tumorigenic cells from nude mice inoculated with cadmium chloride-transformed 16HBE cells. Under the inner standard of GAPDH, the hTERT mRNA expression was significantly higher at different stages of malignant transformation (cadmium chloride-transformed 16HBE cells at passages 15 and 35 and tumorigenic cells from nude mice) than in normal 16HBE cells, and increased with the development of malignancy (P < 0.01). In addition, hTERT protein expression increased with the development of malignancy. These findings demonstrate that hTERT expression is related to cadmium chlorideinduced malignant transformation. Cadmium chloride-induced malignant transformation is involved in changes in the hTERT activity, and might be an early event in cadmium chloride-induced malignant transformation.

Induction of Apoptosis in Pancreatic Cancer Cells by CDDO-Me Involves Repression of Telomerase through Epigenetic Pathways.

Reactivation of telomerase in cancers provides an attractive target for developing novel agents to selectively destroy tumor cells. Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me), a synthetic oleanane triterpenoid, inhibited cell proliferation and induced apoptosis in pancreatic cancer cells at very low concentrations. The antiproliferative and apoptosis-inducing effects of CDDO-Me were associated with the inhibition of human telomerase reverse transcriptase (hTERT) mRNA, hTERT protein and reduction in hTERT telomerase activity. CDDO-Me inhibited multiple transcription factors that regulate hTERT expression positively (Sp1, c-Myc and NF-κB) and negatively (CTCF, E2F-1 and MAD1). CDDO-Me inhibited protein levels of DNA methyl transferases DNMT1 and DNMT3a, which also resulted in hypomethylation of hTERT promoter. In addition, transcriptionally active chromatin markers, such as acetylated histone H3 (Lys 9), acetylated histone H4, di-methyl H3 (Lys 4) and tri-methyl H3 (Lys 9) were all reduced in pancreatic cancer cells treated with CDDO-Me. Chromatin immunoprecipitation analysis showed decreased histone deacetylation and histone demethylation at hTERT promoter. Collectively, these results indicate that down-regulation of telomerase through epigenetic mechanisms plays a critical role in induction of apoptosis in pancreatic cancer cells by CDDO-Me.

Anti-proliferative Effects of Atractylis lancea (Thunb.) DC. via Down-regulation of the c-myc/hTERT/Telomerase Pathway in Hep-G2 Cells

Atractylis lancea (Thunb.) DC. (AL), an important medicinal herb in Asia, has been shown to have anti-tumor effects on cancer cells, but the involved mechanisms are poorly understood. This study focused on potential effects and molecular mechanisms of AL on the proliferation of the Hep-G2 liver cancer cell line in vitro. Cell viability was assessed by MTT test in Hep-G2 cells incubated with an ethanol extract of AL. Then, the effects of AL on apoptosis and cell cycle progression were determined by flow cytometry. Telomeric repeat amplification protocol (TRAP) assays was performed to investigate telomerase activity. The mRNA and protein expression of human telomerase reverse transcriptase (hTERT) and c-myc were determined by real-time RT-PCR and Western blotting. Our results show that AL effectively inhibits proliferation in Hep-G2 cells in a concentration- and time-dependent manner. When Hep-G2 cells were treated with AL after 48h,the IC50 was about 72.1 μg/ mL. Apoptosis was induced by AL via arresting the cells in the G1 phase. Furthermore, AL effectively reduced telomerase activity through inhibition of mRNA and protein expression of hTERT and c-myc. Hence, these data demonstrate that AL exerts anti-proliferative effects in Hep-G2 cells via down-regulation of the c-myc/hTERT/ telomerase pathway.

Study on the immune responses against pancreatic cancer induced by mucin 4 and human telomerase reverse transcriptase mRNA co-transfected dendritic cells in vitro

Objective To investigate the anti-tumor immune response induced by human pancreatic cancer mucin 4 mRNA and human telomerase reverse transcriptase (hTERT) mRNA cotransfected dendritic cells (DC),and to provide the experimental evidences for the treatment of pancreatic cancer with multi-epitope loaded DC vaccine.Methods DC were isolated from peripheral blood mononuclear cells (PBMC) of six patients with HLA-A2+ pancreatic cancer and cultured.Mucin 4 mRNA and hTERT mRNA were transcripted and amplified in vitro,which were transfected into DC separately or in order by eleetroporation.DC were cultured for 48 hours.The expressions of mucin 4 and hTERT in DC were detected by quantitative real-time polymerase chain reaction (PCR) and Western blot.The survival rates of transfected DC were determined by methylthiazolyl tetrazolium (MTT) method.The cytotoxic T lymphocyte (CTL) activation induced by mucin 4 mRNA and hTERT mRNA transfected DC were evaluated by interferon (IFN)-γ release assays (enzyme linked immunosorbent assay) method.The cytotoxicity of CTL induced by mucin 4 mRNA and hTERT mRNA transfected DC in pancreatic cancer cell lines MiaPaCa-2,Capan-2,AsPC-1 and Pane-1 was measured by 51Cr standard cytotoxicity test.Student t test was performed for statistical analysis.Results After in order transfection of mucin 4 mRNA and hTERT mRNA for 48 h,the relative quantity of the expression of mucin 4 and hTERT in DC were 30.09±5.24 and 12.87±3.36,which were lower than the relative quantity of the expression in DC transfected separately (38.54±6.21 and 36.35±5.03,t=3.469,6.721,both P＜0.05).After transfected in order for 96 hours,the survival rate of DC decreased to 52.17％,which was lower than that of DC transfected separately (around 80％).The quantity of IFN-γ releasing of specific CTL induced by mucin 4 mRNA and hTERT mRNA cotransfected DC was (32.57±2.01) U/mL in 24 hours,which was higher than that of CTL induced by DC transfected with mucin 4 mRNA ((23.06±4.74) U/mL) or hTERT mRNA ((16.82±3.67) U/mL) separately (1=5.092,7.141,both P＜0.05).After co-transfected with mucin4 mRNA and hTERT mRNA,DC could effectivly induce HLA-A2+/mucin 4+/hTERT+ specific CTL immune responses,however there was no significant cytotoxicity in HLA-A2+ pancreatic cancer cells.Conclusion The induction of CTL anti-tumor immune response by DC co-transfected with mucin4 mRNA and hTERT mRNA is more significant compared with that by single antigen loaded DC. Key words: Dendritic cells; Mucins; Telomerase; RNA, messenger; Pancreatic neoplasms; T-lymphocytes, cytotoxic

Clinical and Immunological Response Following hTERT/Survivin mRNA-Loaded Dendritic Cell Vaccination Combined With Ex-Vivo Expanded T Cell Transfer In Melanoma Patients

New immunotherapy strategies have recently been developed combining peptide or dendritic cell (DC) vaccination with infusion of vaccine-primed and ex vivo expanded T cells. The hypothesis is that adoptive transfer of ex vivo expanded tumor specific T cells can improve progression-free and overall survival by restoring anti-tumor immunity. In a phase I/II clinical trial on malignant melanomas stage IV patients received DC vaccination prior to transfer of ex vivo expanded T cells. Our strategy was to target hTERT and survivin since both is highly expressed in most cancers. The vaccine consisted of autologous DCs loaded with hTERT and survivin mRNA. Prior to each DC vaccination the patients received 5 days of Temozolomide treatment to reduce the number of regulatory T cells (Treg). Following 2 monthly DC vaccinations, blood samples were tested for immune response against hTERT and survivin overlapping peptides. Immune responders were offered injection of T cells. The Elutra fraction of T cells was depleted of Treg using Dynabeads CD25 prior to expansion with Dynabeads CD3/CD28 in a WAVE bioreactor. After 10 days the beads were removed and T cells were washed. 3x1010 expanded T cells were injected fresh and DC vaccination was continued. Prior to T cell infusion, the patients received non-myeloablative conditioning with Fludarabine and Cyclophosphamide Here we present the results from three patients receiving expanded T cells. Immune response against hTERT and survivin peptides were detected in blood samples from 7 to 11 weeks of DC vaccination. After 4-7 months of DC vaccination the T cells were expanded for 10 days prior to injection. DC vaccination was continued 1 day after T cell injection. Infused T cells expanded significantly in vivo and in two of the three patients currently tested both patients showed response against hTERT and survivin peptides. Blood samples taken monthly after T cell injection demonstrated immune response against the same peptides. In one of patients the number of Treg was high (&gt; 4%) before and during vaccination and returned to low numbers (&lt;1%) after T cell injection. Since these findings might explain the beneficial effect of the vaccination we are currently investigating if the number of Tregs in blood show the same profile in the two other patients. Progression free survival (PFS) in the three patients was 31,20 and 11 months respectively. Patients with the shortest PFS relapsed very shortly after the T-cell infusion in spite of an objective immunresponse following the last DC vaccine. Metastatic melanoma patients included in this study given DC vaccines without T-cells had a median PFS of 7 months (3-13). We therefore conclude that dendritic cell vaccination combined with ex-vivo expanded T cell transfer can be an efficient immunotherapy strategy in melanoma patients. Disclosures: No relevant conflicts of interest to declare.

NFX1-123 and Human Papillomavirus 16E6 Increase Notch Expression in Keratinocytes

The high-risk human papillomavirus (HR HPV) E6 oncoprotein binds host cell proteins to dysregulate multiple regulatory pathways, including apoptosis and senescence. HR HPV16 E6 (16E6) interacts with the cellular protein NFX1-123, and together they posttranscriptionally increase hTERT expression, the catalytic subunit of telomerase. NFX1-123 interacts with hTERT mRNA and stabilizes it, leading to greater telomerase activity and the avoidance of cellular senescence. Little is known regarding what other transcripts are dependent on or augmented by the association of NFX1-123 with 16E6. Microarray analysis revealed enhanced expression of Notch1 mRNA in 16E6-expressing keratinocytes when NFX1-123 was overexpressed. A moderate increase in Notch1 mRNA was seen with overexpression of NFX1-123 alone, but with 16E6 coexpression the increase in Notch1 was enhanced. The PAM2 motif and R3H protein domains in NFX1-123, which were important for increased hTERT expression, were also important in the augmentation of Notch1 expression by 16E6. These findings identify a second gene coregulated by 16E6 and NFX1-123 and the protein motifs in NFX1-123 that are important for this effect.

Inhibitory effect of small interfering RNA mediated by tumor target cell penetrating peptides on in hepatoma cell line SMMC-7721

Objective To observe the inhibitory effect of small interfering RNA (siRNA) mediated by tumor target cell penetrating peptides (CPPS) targeting metalloproteinase on hepatoma cell line SMMC-7721.Methods SMMC-7721 cells were cultured,and divided into experimental group and control group.In experimental group,siRNA/CCPS complex was added,and in control group,silencer negative control/CCPS was added.The cells were harvested after culture for 48 h.Flow cytometry was use to examine the cell cycle.The human telomerase reverse transcriptase (hTERT) gene expression level was detected by using quantitative polymerase chain reaction (PCR).Methyl thiazol tetrazolium (MTT) assay was used to meassure the inhibitory effect of siRNA/CCPS complex on SMMC-7721 cells.Results As compared with control group,the proportion of cells in G1 phase in experimental group was increased (75.14％ vs.62.55％),while that in G2 phase in experimental group decreased (11.39％ vs.12.14％),and that in the S phase also reduced (13.47％ vs.25.31％).Treatment of CPPS plasmid complexes could arrest the cells in the G1 phase,and the expression quantity of hTERT mRNA in experimental group was 74％ of that in control group.After treatment with CPPS plasmid complexes for 48 h,the proliferation inhibition rate of SMMC-7721 cells was 34.82％.Conclusion The CCPS can be a transmitter to transfect siRNA into hepatoma cells and suppress hepatoma cells to some extent. Key words: Carcinoma, hepatocellular; Cell penetrating peptides; Tumor targeting; Small interfering RNA

The β-carboline alkaloid harmine inhibits telomerase activity of MCF-7 cells by down-regulating hTERT mRNA expression accompanied by an accelerated senescent phenotype

The end replication problem, which occurs in normal somatic cells inducing replicative senescence, is solved in most cancer cells by activating telomerase. The activity of telomerase is highly associated with carcinogenesis which makes the enzyme an attractive biomarker in cancer diagnosis and treatment. The indole alkaloid harmine has multiple pharmacological properties including DNA intercalation which can lead to frame shift mutations. In this study, harmine was applied to human breast cancer MCF-7 cells. Its activity towards telomerase was analyzed by utilizing the telomeric repeat amplification protocol (TRAP). Our data indicate that harmine exhibits a pronounced cytotoxicity and induces an anti-proliferation state in MCF-7 cells which is accompanied by a significant inhibition of telomerase activity and an induction of an accelerated senescence phenotype by over-expressing elements of the p53/p21 pathway.

Differential telomerase expression in idiopathic pulmonary fibrosis and non-small cell lung cancer

Telomerase is a reverse transcriptase ribonucleo-protein (h-TERT) that synthesizes telomeric repeats using its RNA component (h-TERC) as a template. Telomerase dysfunction has been associated with both fibrogenesis and carcinogenesis. In this study, we aimed to evaluate the telomerase mRNA expression levels of both subunits (h-TERT and h-TERC) in lung tissue and bronchoalveolar lavage fluid (BALF) from patients with idiopathic pulmonary fibrosis (IPF) and non-small cell lung cancer (NSCLC), since there are indications of common pathogenetic pathways in these diseases. We prospectively examined lung tissue samples from 29 patients with IPF, 10 patients with NSCLC and 21 controls. Furthermore, we examined BALF samples from 31 patients with NSCLC, 23 patients with IPF and 12 control subjects. The mRNA expression for both h-TERT and h-TERC was measured by real-time RT-PCR. In the lung tissue samples, both h-TERT and h-TERC mRNA expression levels varied among the 3 groups (p=0.036 and p=0.002, respectively). h-TERT mRNA levels in the patients with IPF were lower compared with those in the controls (p=0.009) and patients with NSCLC (p=0.004). h-TERC mRNA levels in the patients with IPF were lower compared with those in the controls (p=0.0005) and patients with NSCLC (p=0.0004). In the BALF samples, h-TERT mRNA expression levels varied among the groups (p=0.012). More specifically, h-TERT mRNA levels in the patients with IPF were higher compared with those in the controls (p=0.03) and patients with NSCLC (p=0.007). The attenuation of telomerase gene expression in IPF in comparison to lung cancer suggests a differential role of this regulatory gene in fibrogenesis and carcinogenesis. Further functional studies are required in order to further elucidate the role of telomerase in these devastating diseases.

Hedgehog Signaling Regulates Telomerase Reverse Transcriptase in Human Cancer Cells

The Hedgehog (HH) signaling pathway is critical for normal embryonic development, tissue patterning and cell differentiation. Aberrant HH signaling is involved in multiple human cancers. HH signaling involves a multi-protein cascade activating the GLI proteins that transcriptionally regulate HH target genes. We have previously reported that HH signaling is essential for human colon cancer cell survival and inhibition of this signal induces DNA damage and extensive cell death. Here we report that the HH/GLI axis regulates human telomerase reverse transcriptase (hTERT), which determines the replication potential of cancer cells. Suppression of GLI1/GLI2 functions by a C-terminus truncated GLI3 repressor mutant (GLI3R), or by GANT61, a pharmacological inhibitor of GLI1/GLI2, reduced hTERT protein expression in human colon cancer, prostate cancer and Glioblastoma multiforme (GBM) cell lines. Expression of an N-terminus deleted constitutively active mutant of GLI2 (GLI2ΔN) increased hTERT mRNA and protein expression and hTERT promoter driven luciferase activity in human colon cancer cells while GANT61 inhibited hTERT mRNA expression and hTERT promoter driven luciferase activity. Chromatin immunoprecipitation with GLI1 or GLI2 antibodies precipitated fragments of the hTERT promoter in human colon cancer cells, which was reduced upon exposure to GANT61. In contrast, expression of GLI1 or GLI2ΔN in non-malignant 293T cells failed to alter the levels of hTERT mRNA and protein, or hTERT promoter driven luciferase activity. Further, expression of GLI2ΔN increased the telomerase enzyme activity, which was reduced by GANT61 administration in human colon cancer, prostate cancer, and GBM cells. These results identify hTERT as a direct target of the HH signaling pathway, and reveal a previously unknown role of the HH/GLI axis in regulating the replication potential of cancer cells. These findings are of significance in understanding the important regulatory mechanisms that determine the functions of HH/GLI signaling in cancer cells.

The status of telomerase enzyme activity in benign and malignant gynaecologic pathologies.

Telomeres are essential for the function and stability of eukaryotic chromosomes. Telomerase consists of three subunits: human telomerase reverse transcriptase (hTERT), human telomerase RNA (hTR), and telomerase protein 1 (TP1). The hTERT subunit determines the activity of telomerase as an enzyme and is detected in most human tumors and regenerative cells. Telomerase activity is a useful cancer-cell detecting marker in some types of cancers. The aim of this study was to assess of telomerase hTERT mRNA in gynaecological tumors for diagnosis of malignancy. Cross-sectional study. A total of 55 gynaecologic tumor samples (35 ovarian, 13 endometrial, 6 cervical and 1 placental site trophoblastic tumor tissue) were obtained at the time of surgery. Quantification of hTERT mRNA was performed in a real-time reverse transcriptase polymerase chain reaction (RT-PCR) using the LightCycler TeloTAGGG hTERT Quantification Kit. It was histopathologically detected that 18 of the tissue samples were malignant and 37 of the samples were benign. 16 of the malignant tissue samples (88.9%) and 3 (8.1%) (endometrial tissue in proliferative phase, mucinous cyst adenoma and endometriosis) of the benign tissue samples were found to be hTERT positive. With the presence of these data, sensitivity and specificity of hTERT for the diagnosis of malignancy were calculated to be 88.9% and 91.9%, respectively. It was suggested that the measurement of telomerase activity in gynaecologic tumors, except for endometrial tissue in the reproductive phase, is a valuable method for pathological investigation.

Homocysteine-related hTERT DNA demethylation contributes to shortened leukocyte telomere length in atherosclerosis

AimsLeukocyte telomere length (LTL) is shortened in patients with clinical atherosclerosis (AS). Here we aimed to explore the contribution of elevated homocysteine (Hcy) level to LTL shortening in AS patients and the underlying mechanism. MethodsCirculating leukocytes were collected from 197 patients with AS and 165 sex- and age-matched healthy subjects for LTL determination. mRNA expression or DNA methylation of human telomerase reverse transcriptase (hTERT) was determined by real-time PCR and methylation-specific PCR assay, respectively. We established a hyperhomocysteinemia (HHcy) mice model to confirm human results. ResultsHcy was negatively correlated with LTL shortening in AS patients (r = −0.179, p = 0.015) and controls (r = −0.146, p = 0.031). Serum folate and high-sensitivity C-reactive protein levels significantly interacted with Hcy in LTL shortening. Hcy was related to hTERT mRNA downregulation and promoter demethylation, which combined was associated with LTL shortening in AS patients. Hcy-induced LTL shortening did not differ by sites of AS lesions or infarction. Similar to clinical observations, our HHcy mice model suggested that Hcy induced DNA demethylation and downregulation of mouse TERT and further contributed to LTL shortening. ConclusionsElevated Hcy level induced DNA demethylation of hTERT and was closely related with hTERT downregulation, which led to LTL shortening in AS. These findings provide novel insights into an epigenetic mechanism for Hcy-related AS.

Guanidinylated 3-gluconamidopropyl methacrylamide-s-3-aminopropyl methacrylamide copolymer as siRNA carriers for inhibiting human telomerase reverse transcriptase expression

In this report, a series of well-defined glucose- and guanidine-based cationic copolymers as gene carriers were developed to inhibit human telomerase reverse transcriptase (hTERT) gene expression. First of all, guandinylated 3-gluconamidopropyl methacrylamide-s-3-aminopropyl methacrylamide copolymers (guanidinylated GAPMA-s-APMA, abbreviated as GGA) were prepared via aqueous reversible addition – fragmentation chain transfer polymerization (RAFT). Then, three target hTERT siRNA TERT-1, TERT-2 and TERT-3 were designed and combined with GGA copolymers to form siRNA/GGA polyplexes. The polyplexes were examined by dynamic light scattering and agarose gel electrophoresis. The results indicated that GGA copolymers can condense siRNA effectively to form particles with the diameter from 157 nm to 411 nm and zeta potential values in the range from +3.7 to +15.8 mV at various charge ratios (N/P). The MTT assay data of siRNA/GGA polyplexes on human hepatocellular liver carcinoma cells (HepG2) indicated that GGA copolymer had better cell viabilities than polyethylenimine (PEI). Furthermore, the transfection of siRNA/GGA polyplexes was detected by real-time quantitative PCR (RT-qPCR) in HepG2. It was found that siRNA/GGA polyplexes could effectively silence hTERT mRNA expression in serum-free media (p < 0.01). In the presence of serum, the hTERT mRNA expression in HepG2 cells have significant difference (p < 0.01) between siRNA/GGA3 polyplexes and blank. The results showed that the GAPMA component can reduce the aggregation of protein in serum media. Therefore, the enhancement of transfection may be attributed to the combination of guadino groups and glucose component. And, the guandinylated 3-gluconamidopropyl methacrylamide-s-3-aminopropyl methacrylamide copolymers might be promise in gene delivery.

Physiological and pathological significance of human telomerase reverse transcriptase splice variants

Human telomerase reverse transcriptase (hTERT) is tightly regulated at various transcriptional and post-transcriptional levels. Alternative splicing of hTERT has been shown in many human tissues and cell lines regardless of telomerase status and may play a role in regulation of telomerase activity and other cellular functions. Catalytically inactive splice variants make up a substantial proportion of total hTERT mRNA and are at least partly translated into protein. Shifts in splicing patterns occur in development, tumorigenesis and in response to exogenous stimuli in a tissue- and cell type-specific manner. This review focuses on prevalence, patterns and regulation of hTERT alternative splicing, describes associations with telomerase activity and telomere length, and discusses the potential significance of hTERT alternative splice variants in cancer as well as possible telomere-independent functions.

Chlamydia trachomatis inhibits telomeric DNA damage signaling via transient hTERT upregulation

Epidemiological data exist to support a positive association between Chlamydia trachomatis (Ctr) infection and gynecological cancers; however, putative cellular mechanisms for this association are lacking. Here, we identified Ctr-induced perturbations to host cell phenotypes in vitro that persisted after clearance of infection and could directly contribute to host cell transformation. In particular, human telomerase catalytic subunit (hTERT) mRNA expression and catalytic subunit activity were increased in acute infected late passage IMR90E1A cells. hTERT upregulation was accompanied by recruitment of ceramide, a known regulator of hTERT, to the chlamydial inclusion and was abrogated following doxycycline-mediated infection clearance. In cells cleared of Ctr infection, average telomere length was slightly increased and immunofluorescence staining of the DNA damage marker γH2A.X was reduced after clearance of infection compared with cells that had not been infected. Reduced p53 binding to the promoter of the cell cycle checkpoint regulator p21 was also detected in cells cleared of infection and p21 levels were reduced; moreover, this cell population exhibited increased resistance to etoposide-induced DNA damage. Thus, Ctr infection altered cell aging and survival pathways, which persisted after infection clearance. Cells that survive infection are likely to exhibit altered physiology, as evidenced by an increased resistance to DNA damage-induced apoptosis, which may support cellular transformation.

The antiretroviral agent saquinavir enhances hTERT expression and telomerase activity in human T leukaemia cells in vitro

BackgroundSaquinavir, a protease inhibitor utilized in HIV infection, shows antitumor activity in various experimental models. In previous studies performed in our laboratory the drug was found to induce a substantial increase of telomerase activity in normal peripheral blood mononuclear cells. Aim of the present investigation was to test whether saquinavir was able to increase telomerase activity and the expression of the catalytic subunit of telomerase, hTERT, in human malignant hematopoietic cells.MethodsHuman Jurkat CD4+ T cell leukaemia cell line was used throughout the present study. The antiproliferative effect of saquinavir was tested by the MTT assay. Telomerase activity was determined according to the telomeric repeat amplification protocol. The expression of hTERT mRNA was semi-quantitative evaluated by RT-PCR amplification and quantitative Real Time PCR. The binding of the transcription factor c-Myc to its specific E-Box DNA binding-site of hTERT promoter was analyzed by Electophoretic Mobility Shift Assay (EMSA). The amount of c-Myc in cytoplasm and nucleus of leukemia cells was determined by Western Blot analysis, and c-Myc down-regulation was obtained by siRNA transfection.ResultsSaquinavir produced a substantial increase of telomerase activity in Jurkat cells in vitro without increasing but rather reducing target cell proliferation rate. Telomerase up-regulation appeared to be the result of enhanced expression of hTERT. Saquinavir-mediated up-regulation of hTERT gene was the result of the increased binding of proteins to the E-Box sequence of the promoter. Moreover, saquinavir amplified the expression of c-Myc especially in the nuclear cell fraction. The direct influence of saquinavir on this transcription factor was also demonstrated by the antagonistic effect of the drug on siRNA induced c-Myc suppression. Since c-Myc is the main responsible for hTERT transcription, these findings suggest that the main mechanism underlying saquinavir-induced telomerase activation is mediated by c-Myc up-regulation.ConclusionsSaquinavir augments hTERT expression while inhibiting leukemic cell growth. Experimental evidences show that this effect is mediated by saquinavir-influenced increase of c-Myc levels. This could have relevance in terms of enhanced hTERT-dependent tumor cell immunogenicity and suggests new paharmacological approaches interfering with c-Myc dependent pathways.

Aspirin inhibits human telomerase activation in unstable carotid plaques

The activation of telomerase in unstable plaques is an important factor in atherosclerosis, and may be predictive of the risk of cerebrovascular diseases. Human telomerase reverse transcriptase (hTERT) is a subunit of telomerase that is essential for telomerase activation. The aim of the present study was to investigate whether aspirin inhibits the activation of telomerase and hTERT in unstable carotid plaques. Polymorphonuclear neutrophils (PMNs) derived from carotid plaques were isolated from the washing medium of angioplasty balloons, while circulating PMNs, isolated from arterial blood, served as the controls. A polymerase chain reaction-based telomeric repeat amplification protocol (TRAP) enzyme-linked immunosorbent assay (ELISA) was used to measure the telomerase activity in the cells following treatment with aspirin. The mRNA and protein expression of hTERT were detected by a reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis, respectively. The results revealed that the atherosclerotic plaques were positive for telomerase activity, and that aspirin inhibited the telomerase activity of the PMNs derived from the plaques. In addition, aspirin was demonstrated to inhibit the mRNA and protein expression of hTERT through the suppression of hTERT transcriptional activity; however, it had no inhibitory effect on the telomerase activity of the circulating PMNs. Thus, the activation of telomerase in resident PMNs is critical in the instability of carotid plaques. The upregulation of telomerase and hTERT during the progression of atherosclerosis may indicate a role for telomerase in the vascular remodeling that occurs during atherogenesis. Aspirin was demonstrated to inhibit the activation of telomerase via an hTERT-dependent manner in the PMN cells of unstable carotid plaques, and thus hTERT may be considered as a target in the treatment of cerebrovascular diseases.