hTERT gene dosage correlates with telomerase activity in human lung cancer cell lines

Exercise training increases telomerase reverse transcriptase gene expression and telomerase activity: A systematic review and meta-analysis

Telomeres protect genomic stability and shortening is one of the hallmarks of ageing. Telomerase reverse transcriptase (TERT) is the major protein component of telomerase, which elongates telomeres. Given that short telomeres are linked to a host of chronic diseases and the therapeutic potential of telomerase-based therapies as treatments and a strategy to extend lifespan, lifestyle factors that increase TERT gene expression and telomerase activity could attenuate telomere attrition and contribute to healthy biological ageing. Physical activity and maximal aerobic fitness are associated with telomere maintenance, yet the molecular mechanisms remain unclear. Therefore, the purpose of this systematic review and meta-analysis was to identify the influence of a single bout of exercise and long-term exercise training on TERT expression and telomerase activity. A search of human and rodent trials using the PubMed, Scopus, Science Direct and Embase databases was performed. Based on findings from the identified and eligible trials, both a single bout of exercise (n; standardised mean difference [95%CI]: 5; SMD: 1.19 [0.41-1.97], p = 0.003) and long-term exercise training (10; 0.31 [0.03-0.60], p = 0.03) up-regulates TERT and telomerase activity in non-cancerous somatic cells. As human and rodent studies were included in the meta-analyses both exhibited heterogeneity (I² = 55-87%, p < 0.05). Endurance athletes also exhibited increased leukocyte TERT and telomerase activity compared to their inactive counterparts. These findings suggest exercise training as an inexpensive lifestyle factor that increases TERT expression and telomerase activity. Regular exercise training could attenuate telomere attrition through a telomerase-dependent mechanism and ultimately extend health-span and longevity.

Telomeres and Telomere Length: A General Overview

Telomeres are highly conserved tandem nucleotide repeats that include proximal double-stranded and distal single-stranded regions that in complex with shelterin proteins afford protection at chromosomal ends to maintain genomic integrity. Due to the inherent limitations of DNA replication and telomerase suppression in most somatic cells, telomeres undergo age-dependent incremental attrition. Short or dysfunctional telomeres are recognized as DNA double-stranded breaks, triggering cells to undergo replicative senescence. Telomere shortening, therefore, acts as a counting mechanism that drives replicative senescence by limiting the mitotic potential of cells. Telomere length, a complex hereditary trait, is associated with aging and age-related diseases. Epidemiological data, in general, support an association with varying magnitudes between constitutive telomere length and several disorders, including cancers. Telomere attrition is also influenced by oxidative damage and replicative stress caused by genetic, epigenetic, and environmental factors. Several single nucleotide polymorphisms at different loci, identified through genome-wide association studies, influence inter-individual variation in telomere length. In addition to genetic factors, environmental factors also influence telomere length during growth and development. Telomeres hold potential as biomarkers that reflect the genetic predisposition together with the impact of environmental conditions and as targets for anti-cancer therapies.

Melatonin and non-small cell lung cancer: new insights into signaling pathways

Non-small-cell lung cancer (NSCLC) is a type of malignancy with progressive metastasis having poor prognosis and lowered survival resulting from late diagnosis. The therapeutic approaches for the treatment of this incurable cancer are chemo- and radiotherapy. Since current treatments are insufficient and because of drug-induced undesirable side effects and toxicities, alternate treatments are necessary and critical. The role of melatonin, produced in and released from the pineal gland, has been documented as a potential therapy for NSCLC. Melatonin prevents tumor metastasis via inducing apoptosis processes and restraining the autonomous cell proliferation. Moreover, melatonin inhibits the progression of tumors due to its oncostatic, pro-oxidant and anti-inflammatory effects. As a result, the combined treatment with melatonin and chemotherapy may have a synergistic effect, as with some other tumors, leading to a prolonged survival and improved quality of life in patients with NSCLC. This review summarizes the available data, based on the molecular mechanisms and related signaling pathways, to show how melatonin and its supplementation function in NSCLC.

Urinary RNA-based biomarkers for prostate cancer detection

Prostate cancer (PCa) is the commonest malignancy in the male population worldwide. Serum prostate specific antigen (PSA) test is the most important biomarker for the detection, follow-up and therapeutic monitoring of PCa. Defects in PSA specificity have elicited research for new biomarkers to improve early diagnosis and avoid false-positive results. This review evaluates urinary RNA-based biomarkers. Urine is a versatile body fluid for non-invasive biomarker detection in case of urological malignancies. The importance of RNA-based biomarkers has been demonstrated by the current use of PCA3, a long non coding RNA biomarker already approved by the Food and Drugs Administration. Through the years, other urinary RNA biomarkers have been evaluated, including the well-known TMPRSS2:ERG transcript, as well as many messenger RNAs, long non coding RNAs and micro-RNA. Validation of a specific urinary RNA-based marker or an algorithm of different biomarkers levels as diagnostic markers for PCa could be useful to avoid unnecessary prostate biopsies.

Melatonin inhibits AP-2β/hTERT, NF-κB/COX-2 and Akt/ERK and activates caspase/Cyto C signaling to enhance the antitumor activity of berberine in lung cancer cells

Melatonin, a molecule produced throughout the animal and plant kingdoms, and berberine, a plant derived agent, both exhibit antitumor and multiple biological and pharmacological effects, but they have never been combined altogether for the inhibition of human lung cancers. In this study, we investigated the role and underlying mechanisms of melatonin in the regulation of antitumor activity of berberine in lung cancer cells. Treatment with melatonin effectively increased the berberine-mediated inhibitions of cell proliferation, colony formation and cell migration, thereby enhancing the sensitivities of lung cancer cells to berberine. Melatonin also markedly increased apoptosis induced by berberine. Further mechanism study showed that melatonin promoted the cleavage of caspse-9 and PARP, enhanced the inhibition of Bcl2, and triggered the releasing of cytochrome C (Cyto C), thereby increasing the berberine-induced apoptosis. Melatonin also enhanced the berberine-mediated inhibition of telomerase reverses transcriptase (hTERT) by down-regulating the expression of AP-2β and its binding on hTERT promoter. Moreover, melatonin enhanced the berberine-mediated inhibition of cyclooxygenase 2 (COX-2) by inhibiting the nuclear translocation of NF-κB and its binding on COX-2 promoter. Melatonin also increased the berberine-mediated inhibition of the phosphorylated Akt and ERK. Collectively, our results demonstrated that melatonin enhanced the antitumor activity of berberine by activating caspase/Cyto C and inhibiting AP-2β/hTERT, NF-κB/COX-2 and Akt/ERK signaling pathways. Our findings provide new insights in exploring the potential therapeutic strategies and novel targets for lung cancer treatment.

Acute exercise leads to regulation of telomere-associated genes and microRNA expression in immune cells

Telomeres are specialized nucleoprotein structures that protect chromosomal ends from degradation. These structures progressively shorten during cellular division and can signal replicative senescence below a critical length. Telomere length is predominantly maintained by the enzyme telomerase. Significant decreases in telomere length and telomerase activity are associated with a host of chronic diseases; conversely their maintenance underpins the optimal function of the adaptive immune system. Habitual physical activity is associated with longer leukocyte telomere length; however, the precise mechanisms are unclear. Potential hypotheses include regulation of telomeric gene transcription and/or microRNAs (miRNAs). We investigated the acute exercise-induced response of telomeric genes and miRNAs in twenty-two healthy males (mean age = 24.1±1.55 years). Participants undertook 30 minutes of treadmill running at 80% of peak oxygen uptake. Blood samples were taken before exercise, immediately post-exercise and 60 minutes post-exercise. Total RNA from white blood cells was submitted to miRNA arrays and telomere extension mRNA array. Results were individually validated in white blood cells and sorted T cell lymphocyte subsets using quantitative real-time PCR (qPCR). Telomerase reverse transcriptase (TERT) mRNA (P = 0.001) and sirtuin-6 (SIRT6) (P<0.05) mRNA expression were upregulated in white blood cells after exercise. Fifty-six miRNAs were also differentially regulated post-exercise (FDR <0.05). In silico analysis identified four miRNAs (miR-186, miR-181, miR-15a and miR-96) that potentially targeted telomeric gene mRNA. The four miRNAs exhibited significant upregulation 60 minutes post-exercise (P<0.001). Telomeric repeat binding factor 2, interacting protein (TERF2IP) was identified as a potential binding target for miR-186 and miR-96 and demonstrated concomitant downregulation (P<0.01) at the corresponding time point. Intense cardiorespiratory exercise was sufficient to differentially regulate key telomeric genes and miRNAs in white blood cells. These results may provide a mechanistic insight into telomere homeostasis and improved immune function and physical health.

hTERT promoter activity identifies osteosarcoma cells with increased EMT characteristics

Epithelial-mesenchymal transition (EMT) is a critical step in order for epithelial-derived malignancies to metastasize, however, its role in mesenchymal-derived tumors, i.e., osteosarcoma, remains unclear. Cancer stem cells (CSCs) are enriched with cells that undergo EMT. The activity of telomerase is maintained in normal stem cells and a number of malignant tumors. The current study observed the heterogeneity of telomerase activity among individual osteosarcoma cells. We hypothesized that telomerase-positive (TELpos) cells are enriched for stem cell-like and EMT properties. A human telomerase reverse transcriptase (hTERT) promoter-reporter was applied to assess the telomerase activity of individual MG63 osteosarcoma cells and sort them into TELpos and telomerase-negative (TELneg) subpopulations. It was found that the TELpos cells exhibited an enhanced ability to form sarcospheres in vitro. In addition, TELpos cells exhibited a higher expression of vimentin, accompanied by an increased long/short axis ratio. A panel of EMT-related genes was evaluated by quantitative PCR and western blot analysis, and were found to be significantly upregulated in TELpos cells. Next, the in vitro migration capacity was examined by Transwell assay, which confirmed that TELpos cells are more prone to migration (2.6 fold). The results of the present study support the concept that EMT also applies to mesenchymal-derived osteosarcoma and draws a connection between telomerase and EMT characteristics.

Allelotypes of lung adenocarcinomas featuring ALK fusion demonstrate fewer onco- and suppressor gene changes

BACKGROUND

A subset of lung adenocarcinomas harboring an EML4-ALK fusion gene resulting in dominant oncogenic activity has emerged as a target for specific therapy. EML4-ALK fusion confers a characteristic histology and is detected more frequently in never or light smokers and younger patients.

METHODS

To gain insights into etiology and carcinogenic mechanisms we conducted analyses to compare allelotypes of 35 ALK fusion-positive and 95 -negative tumours using single nucleotide polymorphism (SNP) arrays and especially designed software which enabled precise global genomic profiling.

RESULTS

Overall aberration numbers (gains + losses) of chromosomal alterations were 8.42 and 9.56 in tumours with and without ALK fusion, respectively, the difference not being statistically significant, although patterns of gain and loss were distinct. Interestingly, among selected genomic regions, oncogene-related examples such as 1p34.3(MYCL1), 7q11.2(EGFR), 7p21.1, 8q24.21(MYC), 16p13.3, 17q12(ERBB2) and 17q25.1 showed significantly less gain. Also, changes in tumour suppressor gene-related regions, such as 9p21.3 (CDKN2A) 9p23-24.1 (PTPRD), 13q14.2 (RB1), were significantly fewer in tumours with ALK fusion.

CONCLUSION

Global genomic comparison with SNP arrays showed tumours with ALK fusion to have fewer alterations in oncogenes and suppressor genes despite a similar overall aberration frequency, suggesting very strong oncogenic potency of ALK activation by gene fusion.

hTERT gene amplification and clinical significance in pleural effusions of patients with lung cancer

PATIENTS AND METHODS

Human telomerase reverse transcriptase (hTERT) gene amplification was detected in pleural effusions of patients with lung cancer (n = 69) and in patients with benign lung disease (n = 46) when using a quantitative polymerase chain reaction (qPCR) technique.

RESULTS

hTERT gene relative copy numbers were significantly higher in effusions from patients with malignant, adenocarcinoma and small-cell lung cancer than in effusions from patients with benign lung disease (P < .01). By using a threshold value of 1.39, hTERT gene amplification was significantly more frequent in malignant effusions compared with benign effusions and more likely to be positive for malignant effusions, compared with cytology (P < .01). The diagnostic performance of qPCR of hTERT gene amplification was significantly higher than that of cytology, in terms of sensitivity (91.3% vs. 56.5%), negative predictive value (87.8% vs. 60.5%), and accuracy (92.2% vs. 73.9%).

CONCLUSIONS

Detecting hTERT gene amplification by qPCR appears suitable for distinguishing carcinoma cells from reactive mesothelial cells in pleural effusions. hTERT gene amplification was more sensitive than cytology and may be useful for diagnosing pleural micrometastases.

Telomerase regulation

The intimate connection between telomerase regulation and human disease is now well established. The molecular basis for telomerase regulation is highly complex and entails multiple layers of control. While the major target of enzyme regulation is the catalytic subunit TERT, the RNA subunit of telomerase is also implicated in telomerase control. In addition, alterations in gene dosage and alternative isoforms of core telomerase components have been described. Finally, telomerase localization, recruitment to the telomere and enzymology at the chromosome terminus are all subject to modulation. In this review we summarize recent advances in understanding fundamental mechanisms of telomerase regulation.

Increased copy number of the TERT and TERC telomerase subunit genes in cancer cells

Telomerase is a ribonucleoprotein enzyme complex that adds telomeric repeats to the ends of chromosomes. The core telomerase components are the telomerase reverse transcriptase (TERT) catalytic subunit, and the telomerase RNA (TR) template subunit. In most cancers, telomerase is expressed at levels that are substantially higher than in normal cells. A known consequence of telomerase up-regulation which is considered to play a critical role in oncogenesis is maintenance of telomere length, and thus evasion by cancer cells of the normal limits on proliferation that are associated with the steady decrease in telomere length that accompanies proliferation of normal cells. It has also been suggested that telomerase up-regulation confers other advantages on cancer cells independent of its enzymatic activity. The mechanisms responsible for up-regulation of telomerase in cancer are incompletely understood. Here we review evidence suggesting that this frequently results from increased copy number of the genes encoding telomerase components. The TERT gene is located at human chromosome band 5p15.33, and the telomerase RNA component (TERC) gene that encodes TR is at 3q26.3. Chromosomal gains and gene amplifications involving chromosome arms 5p and 3q are among the most frequent in human tumors. Increased TERT and TERC gene dosage has been detected frequently in a variety of human cancers, and clonal evolution of cells with increased TERT or TERC copy number has been observed, suggesting a growth advantage in cells with increased TERT or TERC gene dosage.

High telomerase activity and long telomeres in advanced hepatocellular carcinomas with poor prognosis

Telomerase reactivation and telomere maintenance are crucial in carcinogenesis and tumor progression. In this study, the relationships between telomere parameters, chromosomal instability and clinicopathological features were evaluated in hepatocellular carcinomas (HCCs). Telomere length (TL), telomerase activity (TA) and human telomerase reverse transcriptase (hTERT) mRNA levels were measured in 49 hepatitis B virus (HBV)-related HCCs and corresponding non-tumorous tissues. The results were compared with clinicopathological data, including differentiation, multipolar mitosis (MM), anaphase bridge, immunohistochemical stain results for cytokeratin 19 (CK19) and patient outcome. TL of HCCs ranged from 4.7 to 13.1 kb, and 44.4% of HCCs showed telomere lengthening. hTERT mRNA levels and TA were closely related (P=0.008), and were significantly higher in HCCs than non-tumorous tissues. TL was significantly higher in HCCs with strong TA (P=0.048), high hTERT mRNA levels (P=0.001) and poor differentiation (P=0.041). Frequent MM was associated with poor differentiation (P=0.007) and advanced stage (P<0.001). TA was positively correlated with MM, anaphase bridges and advanced stage (P=0.019, P=0.017 and P=0.029). Thirteen (28.3%) HCCs were CK19+ and demonstrated longer telomeres than CK19- HCCs (P=0.046). Overall survival was poor in HCCs with MM >0.4 per field (P=0.016), high TA (P=0.009) and high TL ratio (HCC/non-HCC) >0.8 (P=0.044). Our results show that long telomeres, high TA and high mitotic instability are poor prognostic markers for HBV-related HCCs and their close association suggests that telomere maintenance may be important for the progression of HCCs with high chromosomal instability to more aggressive ones.

Telomerase redefined: Integrated regulation of hTR and hTERT for telomere maintenance and telomerase activity

Telomerase activity is dependent on the expression of 2 main core component genes, hTERT, which encodes the catalytic component and hTR (also called TERC), which encodes the RNA component. The correlation between telomerase activity and carcinogenesis has made this molecule of great interest in cancer research, however in order to fully understand the regulation of telomerase the mechanisms controlling both telomerase genes need to be studied. Some of these mechanisms of regulation have begun to emerge, however many more remain to be deciphered. For many years hTERT has been regarded as the limiting component of telomerase and much of the research in this field has focussed on its regulation, however it was clear from an early stage that hTR expression was also tightly regulated in normal cells and disease. More recently evidence from biochemistry, promoter studies and mouse models has been steadily increasing for a role for hTR as a limiting and essential component for telomerase activity and telomere maintenance. Perhaps the time has come to redefine our view of telomerase regulation. Knowledge of the mechanisms controlling both telomerase genes in normal systems and cancer may aid our understanding of the role of telomerase in carcinogenesis or highlight potential areas for therapeutic intervention. Here we review the essential requirement of hTR for telomere maintenance and telomerase activity in normal tissues and disease and focus on recent advances in our understanding of hTR regulation in relation to hTERT.

Free radicals and antioxidants in normal physiological functions and human disease

Reactive oxygen species (ROS) and reactive nitrogen species (RNS, e.g. nitric oxide, NO(*)) are well recognised for playing a dual role as both deleterious and beneficial species. ROS and RNS are normally generated by tightly regulated enzymes, such as NO synthase (NOS) and NAD(P)H oxidase isoforms, respectively. Overproduction of ROS (arising either from mitochondrial electron-transport chain or excessive stimulation of NAD(P)H) results in oxidative stress, a deleterious process that can be an important mediator of damage to cell structures, including lipids and membranes, proteins, and DNA. In contrast, beneficial effects of ROS/RNS (e.g. superoxide radical and nitric oxide) occur at low/moderate concentrations and involve physiological roles in cellular responses to noxia, as for example in defence against infectious agents, in the function of a number of cellular signalling pathways, and the induction of a mitogenic response. Ironically, various ROS-mediated actions in fact protect cells against ROS-induced oxidative stress and re-establish or maintain "redox balance" termed also "redox homeostasis". The "two-faced" character of ROS is clearly substantiated. For example, a growing body of evidence shows that ROS within cells act as secondary messengers in intracellular signalling cascades which induce and maintain the oncogenic phenotype of cancer cells, however, ROS can also induce cellular senescence and apoptosis and can therefore function as anti-tumourigenic species. This review will describe the: (i) chemistry and biochemistry of ROS/RNS and sources of free radical generation; (ii) damage to DNA, to proteins, and to lipids by free radicals; (iii) role of antioxidants (e.g. glutathione) in the maintenance of cellular "redox homeostasis"; (iv) overview of ROS-induced signaling pathways; (v) role of ROS in redox regulation of normal physiological functions, as well as (vi) role of ROS in pathophysiological implications of altered redox regulation (human diseases and ageing). Attention is focussed on the ROS/RNS-linked pathogenesis of cancer, cardiovascular disease, atherosclerosis, hypertension, ischemia/reperfusion injury, diabetes mellitus, neurodegenerative diseases (Alzheimer's disease and Parkinson's disease), rheumatoid arthritis, and ageing. Topics of current debate are also reviewed such as the question whether excessive formation of free radicals is a primary cause or a downstream consequence of tissue injury.

Amplification of telomerase (hTERT) gene is a poor prognostic marker in non-small-cell lung cancer

Telomerase reactivation is a hallmark of human carcinogenesis. Increased telomerase activity may result from gene amplification and/or overexpression. This study evaluates the prognostic value of hTERT gene amplification and mRNA overexpression in 144 resectable non-small-cell lung cancer (NSCLC) specimens. The hTERT gene copy number was assessed by quantitative polymerase chain reaction (qPCR) on laser-capture microdissected tumour cells of 81 tumours, and by fluorescence in situ hybridisation (FISH) on a subset of 59 tumours. hTERT mRNA level was determined by reverse transcription (RT)-qPCR in 130 tumours. In total, 57% of (46 out of 81) primary NSCLC specimens demonstrated hTERT amplification, which was significantly more common (P<0.001) in adenocarcinoma (30 out of 40) than in squamous cell carcinoma (13 out of 37). The hTERT mRNA overexpression was noted in 74% (94 out of 130) of tumours; it was more frequent in squamous cell than in adenocarcinoma (87 vs 68%, P=0.03). Overexpression was significantly associated with amplification (P=0.03), especially in adenocarcinoma. The hTERT gene amplification was prognostic for shorter recurrence-free survival (hazard ratio=2.16, P=0.03). These data indicate that gene amplification is an important mechanism for hTERT overexpression in lung adenocarcinoma and is an independent poor prognostic marker for disease-free survival in NSCLC.

Quantitative assessment of hTERT mRNA expression in dysplastic nodules of HBV-related hepatocarcinogenesis

BACKGROUND

Telomerase reverse transcriptase (hTERT) is the rate-limiting determinant of telomerase, which is critical for carcinogenesis. Dysplastic nodules (DNs) appear to be preneoplastic lesions of hepatocellular carcinomas (HCCs). In this study, in order to characterize DNs, hTERT mRNA, hTERT gene dosage, and mRNA for c-myc, a transcriptional activator of hTERT were studied in human multi-step hepatocarcinogenesis.

METHODS

Fifty four hepatic nodules including 5 large regenerative nodules, 14 low-grade DNs, 7 high-grade DNs, 11 DNs with HCC foci and 17 HCCs, 23 livers with chronic hepatitis/cirrhosis, and 6 normal livers were examined. Transcript levels were measured by real-time quantitative RT-PCR and gene dosages by real-time PCR and Southern blotting.

RESULTS

The hTERT mRNA levels increased with the progression of hepatocarcinogenesis, and a significant induction in the transition between low- and high-grade DNs was seen. Most high-grade DNs strongly expressed hTERT mRNA at levels similar to those of HCCs. Twenty-one percent of low-grade DNs had high levels of hTERT mRNA, up to those of high-grade DNs and there was no difference in the pathological features between low-grade DNs with and without increased hTERT mRNA levels. No correlation was found between hTERT mRNA levels, hTERT gene dosage, and c-myc mRNA levels.

CONCLUSIONS

These results suggest that the induction of hTERT mRNA is an important early event and that its measurement by real-time quantitative RT-PCR is a useful tool to detect premalignant/malignant tendencies in hepatic nodules. However, hTERT gene dosage and c-myc expression are not the main mechanisms regulating hTERT expression in hepatocarcinogenesis.

Molecular diagnostics of non-small cell lung cancer using mediastinal lymph nodes sampled by endoscopic ultrasound-guided needle aspiration

Non-small cell lung cancer is a common cancer with significant mortality. Accurate and early staging of this cancer has a significant impact on outcome. Endoscopic ultrasound-guided fine needle aspiration of involved mediastinal lymph nodes is critical for staging. Several molecular markers have been identified recently in association with non-small cell carcinoma of the lung that are promising to make early detection of metastatic disease more reliable.

Radiotherapy sensitization by tumor-specific TRAIL gene targeting improves survival of mice bearing human non-small cell lung cancer

PURPOSE

To sensitize non-small cell lung cancer (NSCLC) to radiotherapy by tumor-specific delivery of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene.

EXPERIMENTAL DESIGN

The TRAIL was delivered to human NSCLC cell lines and normal human bronchial epithelial cells by the replication-defective adenoviral vector Ad/TRAIL-F/RGD using a tumor-specific human telomerase reverse transcriptase promoter. Cancer growth was studied using 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt and clonogenic assays. Activation of the apoptosis pathway was analyzed in a Western blot and sub-G(1) DNA accumulation. A xenograft mouse lung cancer model was treated by intratumoral injections of Ad/TRAIL-F/RGD and local radiotherapy; the other groups received one of these treatments alone or a control agent. Apoptosis and TRAIL expression in tumors were also analyzed.

RESULTS

Ad/TRAIL-F/RGD specifically targets human NSCLC cells without significant effect in normal human bronchial epithelial cells. The combination of Ad/TRAIL-F/RGD and radiotherapy significantly improved cell-killing effect in all NSCLC cell lines tested (P < 0.05). Expression of TRAIL showed a dose-dependent relationship with Ad/TRAIL-F/RGD, and radiation seemed to increase TRAIL expression. Activation of the apoptosis by TRAIL and radiation was shown by activation of caspase-9, caspase-8, caspase-3, and poly(ADP-ribose) polymerase and increased DNA sub-G(1) accumulation. The combination of TRAIL and radiotherapy significantly increased apoptosis in vivo, inhibited tumor growth, and prolonged mean survival in mice bearing human NSCLC to 43.7 days compared with 23.7 days (TRAIL only) and 16.5 days (radiotherapy only; P < 0.05).

CONCLUSIONS

The combination of Ad/TRAIL-F/RGD and radiotherapy significantly improved therapeutic efficacy in suppressing NSCLC tumor growth and prolonging survival. Ad/TRAIL-F/RGD may improve the therapeutic ratio of radiotherapy in NSCLC.

Endogenous and ectopic expression of telomere regulating genes in chicken embryonic fibroblasts

In this study, we compared the endogenous expression of genes encoding telomere regulating proteins in cultured chicken embryonic fibroblasts (CEFs) and 10-day-old chicken embryos. CEFs maintained in vitro senesced and senescence was accompanied by reduced telomere length, telomerase activity, and expression of the chicken (c) TRF1 gene. There was no change in TRF2 gene expression although the major TRF2 transcript identified in 10-day-old chicken embryos encoded a truncated TRF2 protein (TRF2'), containing an N-terminal dimerisation domain but lacking a myb-related DNA binding domain and nuclear localisation signal. Senescence of the CEFs in vitro was associated with the loss of the TRF2' transcript, indicative of a novel function for the encoded protein. Senescence was also coupled with decreased expression of RAD51, but increased RAD52 expression. These data support that RAD51 independent recombination mechanisms do not function in vitro to maintain chicken telomeres. To attempt to rescue the CEFs from replicative senescence, we stably transfected passage 3 CEFs with the human telomerase reverse transcriptase (hTERT) catalytic subunit. While hTERT expression was detected in the stable transfectants neither telomerase activity nor the stabilisation of telomere length was observed, and the transfectant cells senesced at the same passage number as the untransfected cells. These data indicate that the human TERT is incompatible with the avian telomere maintenance apparatus and suggest the functioning of a species specific telomere system in the avian.

Chromosome 5p aberrations are early events in lung cancer: implication of glial cell line-derived neurotrophic factor in disease progression

Lung cancer is the most widely diagnosed malignancy in the world. Understanding early-stage disease will give insight into its pathogenesis. Despite the fact that pre-invasive lesions are challenging to isolate, and often yield insufficient DNA for the analysis of multiple loci, genomic profiling of such lesions will lead to the discovery of causal genetic alterations, which may be otherwise masked by the gross instability associated with tumors. In this study, we report the identification of multiple early genetic events on chromosome 5p in lung cancer progression. Using a high-resolution 5p-specific genomic array, which contains a tiling path of DNA segments for comparative genomic hybridization, nine novel minimal regions of loss and gain were discovered in bronchial carcinoma in situ (CIS) specimens. Within these regions we identified two candidate genes novel to lung cancer. The 0.27 Mbp region at 5p15.2 contains a single gene, Triple Functional Domain, which we determined to be differentially expressed in tumors. The 0.34 Mbp region at 5p13.2 contains Glial Cell Line-Derived Neurotrophic Factor (GDNF), which is a ligand for the RET oncogene product and is normally expressed during lung development (but absent in adult lung tissue). Our data showed not only that GDNF is overexpressed at the transcript level in squamous non-small-cell lung carcinoma, but also that the GDNF protein is present in early-stage lesions. Reactivation of the fetal lung expressed GDNF in early lesions and its amplification in CIS suggests an early role in tumorigenesis. These results highlight the value of examining the genomes of pre-invasive stages of cancer at tiling resolution.

Induction of telomerase activity in avian lymphoblastoid cell line transformed by Marek's disease virus, MDCC-MSB1

Telomerase has been studied extensively in human and murine tumors, but little is known about the role of telomerase in the tumor biology of other vertebrate species such as the chicken. We studied the telomerase activity of the lymphoblastoid cell line derived from lymphomas induced by Marek's disease virus (MDCC-MSB1) compared with another avian cell line (PA5) and peripheral blood lymphocytes (PBL) using the telomeric repeat amplification protocol (TRAP) Assay. Telomerase activity in MDCC-MSB1 was 4.5 times greater than in the PA5 cell line and normal avian lymphocytes. These results demonstrate for the first time that telomerase is more intense in one transformed cell line than in normal cells, suggesting a potential role for telomerase in carcinogenesis induced by an avian virus.

Telomerase reverse transcriptase gene amplification in hepatocellular carcinoma

BACKGROUND AND AIM

Telomerase activation is essential for the immortality of cancer cells. The expression of telomerase reverse transcriptase (hTERT), the catalytic component of the telomerase complex, regulates telomerase activity in human cancers. Amplification of the hTERT gene, located at chromosome 5p, is thought to be a potential genetic event contributing to telomerase activation in sporadic tumors.

METHODS

The amplification of the hTERT gene was examined in 46 surgically resected hepatocellular carcinomas (HCC) by real-time polymerase chain reaction and the status was compared with the expression of hTERT mRNA and clinicopathological parameters.

RESULTS

Amplified hTERT genes were found in 21.7% (10/46) of HCC. The incidence of amplified hTERT genes in poorly differentiated HCC (6/12, 50%) was significantly higher than that in highly to moderately differentiated HCC (4/34, 11.8%; P = 0.012). Tumor size in those cases with hTERT gene amplification was larger compared to those cases with no amplification (P = 0.047). Amplification of the hTERT gene was not observed in non-cancerous tissues. The hTERT mRNA level did not correlate with the number of hTERT genes.

CONCLUSIONS

Based on these results, it is thought that hTERT gene amplification is a cancer-specific event, and may furthermore contribute to the dedifferentiation and development of HCC. However, hTERT gene overexpression was rarely due to an increased hTERT gene copy number in HCC.

Prostate cancer molecular markers GSTP1 and hTERT in expressed prostatic secretions as predictors of biopsy results

OBJECTIVES

To develop noninvasive diagnostic tools for the early detection of prostate cancer (PCa). Current screening for PCa lacks sensitivity and specificity. Two molecular markers, telomerase activity and aberrant methylation of the glutathione S-transferase P1 (GSTP1) promoter, are found in more than 90% of PCa specimens. Additionally, these markers can be detected in bodily fluids such as urine and postprostatic massage urethral washes.

METHODS

Expressed prostatic secretions (EPS) from men being evaluated for PCa were analyzed for human telomerase reverse transcriptase (hTERT) expression (the critical factor for telomerase activity) and GSTP1 methylation status. The results were compared with the prostate needle biopsy findings.

RESULTS

EPS could be obtained from 86% of all subjects, and 90% of these samples yielded sufficient RNA and/or DNA for assaying. hTERT expression from EPS (n = 49) had 36% sensitivity and 66% specificity, and GSTP1 methylation from EPS (n = 58) had 46% sensitivity and 56% specificity for the detection of PCa. The combined analysis (n = 32) of hTERT and GSTP1 had 73% sensitivity and 43% specificity, giving a positive predictive value of 40% and a negative predictive value of 75%.

CONCLUSIONS

These results demonstrate that EPS can be successfully obtained and easily tested for hTERT expression and GSTP1 methylation. Tests with a high negative predictive value, such as our combination assay results, could be useful in augmenting current PCa diagnostic procedures. For example, the examination of EPS for hTERT and GSTP1 methylation in patients with an elevated prostate-specific antigen level might be used in predicting which patients will have negative biopsies. The use of this assay could potentially eliminate up to 30% of costly and invasive needle biopsies.

Telomerase activity level, but not hTERT mRNA and hTR level, regulates telomere length in telomerase-reconstituted primary fibroblasts

The critical factors in the regulation of telomere length are not yet clearly defined. Telomerase is a key player in telomere elongation, although previous studies have shown that telomeres are differentially elongated after telomerase reconstitution. Moreover, a clear relation between the level of telomerase activity and telomere length was not observed. To investigate which factors are critical in telomere length regulation, we generated 24 telomerase-reconstituted primary human fibroblast clones. In these clones, in vitro telomerase activity level is clearly related to telomere length. High levels of telomerase activity are associated with longer telomeres and better telomere maintenance over time. The correlation coefficient, however, indicates that the level of telomerase activity is not the only factor in the regulation of telomere length. Clearly, factors that are not measured in an in vitro telomerase activity assay are involved in telomere length regulation in vivo. To investigate which telomerase components are critical in regulating telomerase activity levels, we studied expression levels of hTERT mRNA and hTR. Expression is highly variable between individual clones, but not related to the level of telomerase activity or telomere length. Our results indicate that expression levels of hTERT mRNA and hTR do not regulate the activity level of the telomerase complex, suggesting posttranscriptional modification of hTERT or the presence of additional proteins that modulate telomerase enzyme activity.

Potent antitumoral efficacy of a novel replicative adenovirus CNHK300 targeting telomerase-positive cancer cells

PURPOSE

Telomerase reverse transcriptase (hTERT) is the key determinant of telomerase activity and plays a crucial role in cellular immortalization and oncogenesis. It will be a promising target for cancer gene therapy. We constructed a novel replicative adenovirus CNHK300 in which hTERT promoter with three extra E-boxes downstream of the promoter was introduced and used to regulate adenoviral E1a gene, and studied its properties of selective replication in cancer cells and antitumoral activity.

METHODS

Luciferase assay was used to detect hTERT promoter activity. The selective replication of CNHK300 in cancer cells was investigated by E1a Western blot and green fluorescent protein (GFP) reporter gene assay. The antitumoral activity of CNHK300 and its toxicity were measured on animal models.

RESULTS

Luciferase assay showed that introducing extra E-boxes downstream of hTERT promoter is beneficial to decreasing the promoter activity in normal cells without affecting its strong activity in cancer cells. Experiments in vitro and in vivo demonstrated that CNHK300 can selectively target to hTERT-positive cancer cells and replicate in them, resulting in oncolytic or antitumoral effect. CNHK300 is superior to ONYX-015 in terms of selective replication and oncolytic or antitumoral effect. The toxicity assay showed no signs of toxicity to liver cells even at the higher dosage of CNHK300 in vivo.

CONCLUSION

The hTERT promoter-controlled, replication-competent adenovirus CNHK300 is a promising system for targeted cancer gene therapy.

Chromosomal imbalances in primary and metastatic melanomas: over-representation of essential telomerase genes

Comparative genomic hybridization was used to map copy number abnormalities in 48 short-term cell cultures established from different stages and types of human melanoma. A variety of random and non-random chromosomal alterations were detected, with gains within chromosomes 20q, 7q, 7p, 20p, 6p and 17q and losses in 9p, 10q, 6q, 10p, 4q, and 11q being the most common observations. In addition, several other chromosomal loci were over- or under-represented in subgroups of melanomas. For example, sequences on 3q26 were over-represented in 33% and on 5p15.33 in 27% of cell cultures, reaching the level of amplification in 12% and 22%, respectively. These regions harbour the two essential genes for the enzyme telomerase: the telomerase reverse transcriptase gene (hTERT) on 5p15.33 and the telomerase RNA component gene (hTERC) on 3q26. Using fluorescence in situ hybridization and Southern blot analysis, both genes were shown to be over-represented or amplified in several melanomas. Interestingly, hTERT amplification was abundant in superficial spreading primary melanomas, subcutaneous metastases and malignant effusion-derived cells, but completely absent or very rare in primary nodular melanomas as well as brain, bone and lymph node metastases. Several chromosomes or chromosomal regions harbouring telomerase-suppressing activities (3p, 4, 6 and 10p) were frequently under-represented in melanomas. Our data suggest that genetic alterations at several chromosomal loci might facilitate activation of telomerase during the development of cutaneous malignant melanoma.

Stochastic Variation in Telomere Shortening Rate Causes Heterogeneity of Human Fibroblast Replicative Life Span

The replicative life span of human fibroblasts is heterogeneous, with a fraction of cells senescing at every population doubling. To find out whether this heterogeneity is due to premature senescence, i.e. driven by a nontelomeric mechanism, fibroblasts with a senescent phenotype were isolated from growing cultures and clones by flow cytometry. These senescent cells had shorter telomeres than their cycling counterparts at all population doubling levels and both in mass cultures and in individual subclones, indicating heterogeneity in the rate of telomere shortening. Ectopic expression of telomerase stabilized telomere length in the majority of cells and rescued them from early senescence, suggesting a causal role of telomere shortening. Under standard cell culture conditions, there was a minor fraction of cells that showed a senescent phenotype and short telomeres despite active telomerase. This fraction increased under chronic mild oxidative stress, which is known to accelerate telomere shortening. It is possible that even high telomerase activity cannot fully compensate for telomere shortening in all cells. The data show that heterogeneity of the human fibroblast replicative life span can be caused by significant stochastic cell-to-cell variation in telomere shortening.

Loss of 13q14-q21 and gain of 5p14-pter in the progression of leiomyosarcoma

Leiomyosarcomas of soft tissues are an aggressive group of tumors with a high incidence of recurrence. Little is known about the molecular genetic changes associated with clinical outcome. Therefore, we studied 28 leiomyosarcoma samples of similar grade using comparative genomic hybridization and DNA flow cytometry and identified a difference in survival time associated with ploidy status and the number of chromosomal aberrations. The average survival time was shown to decrease with increase in chromosomal aberrations identified using comparative genomic hybridization. The average survival time was shorter in the near-tetraploid group than in the diploid and triploid group. Gain of 5p14-pter was significantly more common in near-tetraploid tumors. The survival time of patients with near-tetraploidy together with gain of 5p14-pter was reduced, and 50% died within the 1st year. Furthermore, loss of 13q14-q21 was significantly more frequent in the <5-year than in the >5-year survival group (P =.01). These results suggest that 13q14-q21 loss and 5p14-pter gain at diagnosis could be used to identify patients with leiomyosarcoma who are likely to have a shorter survival time and who might benefit from early treatment intensification.

Detection of telomerase expression in mediastinal lymph nodes of patients with lung cancer

Mediastinal lymph nodes are the most common site of tumor spread in non-small cell lung cancer (NSCLC). We hypothesized that micrometastatic disease could be detected by reverse transcription-polymerase chain reaction (RT-PCR) for expression of human telomerase reverse transcriptase (hTERT) in mediastinal lymph nodes and that a minimally invasive technique (endoscopic ultrasound-guided fine-needle aspiration [EUS-FNA]) is capable of sampling lymph nodes for PCR analysis without surgery. Mediastinal lymph nodes were sampled with EUS-FNA in patients with NSCLC and negative control subjects undergoing EUS for benign disease. Total RNA was harvested from samples, and RT-PCR was performed to detect telomerase gene expression. RNA was available from 87 of 100 lymph node aspirates from 39 patients with NSCLC and from 12 negative control patients. hTERT was expressed in 0 of 14 negative control lymph nodes in 18 of 57 pathologically negative lymph nodes from cancer patients and in 10 of 16 pathologically positive lymph nodes (p < 0.05). Five of 18 (28%) patients with no pathologically evident mediastinal disease expressed telomerase in at least one lymph node. Minimally invasive EUS-FNA with RT-PCR is capable of detecting expression of cancer specific mRNA in lymph nodes. Approximately one-third of pathologically negative mediastinal lymph nodes in NSCLC patients express hTERT mRNA. The clinical significance of this observation is yet to be determined.

hTERT gene amplification and increased mRNA expression in central nervous system embryonal tumors

High-level gains at 5p15, a chromosomal region including the human telomerase catalytic protein subunit (hTERT) gene, have been documented in several medulloblastomas. We therefore analyzed hTERT gene dosage in a group of medulloblastomas and other embryonal brain tumors using differential PCR. Amplification of the hTERT locus was detected in 15 of 36 (42%) tumors examined. To correlate gene amplification with message level, we used real-time quantitative PCR to measure hTERT mRNA in 50 embryonal brain tumors. hTERT mRNA was detected in all but one of these cases, and mRNA level correlated significantly with gene dosage (r = 0.82). Log-rank analysis of survival data revealed a trend toward poor clinical outcomes in patients with medulloblastomas containing high hTERT mRNA levels, but clinical follow-up was relatively short and the association was not statistically significant (P = 0.078). Comparative genomic hybridization was used to further analyze the tumor with the greatest hTERT gene dosage and mRNA level, a recurrent medulloepithelioma. hTERT was amplified in the recurrent tumor but not in the primary lesion, suggesting this locus can be involved in tumor progression. Our data indicate that hTERT gene amplification is relatively common in embryonal brain tumors, and that increased expression of hTERT mRNA may be associated with biologically aggressive tumor behavior.

Deletion of the telomerase reverse transcriptase gene and haploinsufficiency of telomere maintenance in Cri du chat syndrome

Cri du chat syndrome (CdCS) results from loss of the distal portion of chromosome 5p, where the telomerase reverse transcriptase (hTERT) gene is localized (5p15.33). hTERT is the rate-limiting component for telomerase activity that is essential for telomere-length maintenance and sustained cell proliferation. Here, we show that a concomitant deletion of the hTERT allele occurs in all 10 patients with CdCS whom we examined. Induction of hTERT mRNA in proliferating lymphocytes derived from five of seven patients was lower than that in unaffected control individuals (P<.05). The patient lymphocytes exhibited shorter telomeres than age-matched unaffected individuals (P<.0001). A reduction in replicative life span and a high rate of chromosome fusions were observed in cultured patient fibroblasts. Reconstitution of telomerase activity by ectopic expression of hTERT extended the telomere length, increased the population doublings, and prevented the end-to-end fusion of chromosomes. We conclude that hTERT is limiting and haploinsufficient for telomere maintenance in humans in vivo. Accordingly, the hTERT deletion may be one genetic element contributing to the phenotypic changes in CdCS.