A triggered DNA nanomachine with enzyme-free for the rapid detection of telomerase activity in a one-step method

BACKGROUND

Telomerase is considered a biomarker for the early diagnosis and clinical treatment of cancer. The rapid and sensitive detection of telomerase activity is crucial to biological research, clinical diagnosis, and drug development. However, the main obstacles facing the current telomerase activity assay are the cumbersome and time-consuming procedure, the easy degradation of the telomerase RNA template and the need for additional proteases. Therefore, it is necessary to construct a new method for the detection of telomerase activity with easy steps, efficient reaction and strong anti-interference ability.

RESULTS

Herein, an efficient, enzyme-free, economical, sensitive, fluorometric detection method for telomerase activity in one-step, named triggered-DNA (T-DNA) nanomachine, was created based on target-triggered DNAzyme-cleavage activity and catalytic molecular beacon (CMB). Telomerase served as a switch and extended few numbers of (TTAGGG)n repeat sequences to initiate the signal amplification in the T-DNA nanomachine, resulting in a strong fluorescent signal. The reaction was a one-step method with a shortened time of 1 h and a constant temperature of 37 °C, without the addition of any protease. It also sensitively distinguished telomerase activity in various cell lines. The T-DNA nanomachine offered a detection limit of 12 HeLa cells μL-1, 9 SK-Hep-1 cells μL-1 and 3 HuH-7 cells μL-1 with a linear correlation detection range of 0.39 × 102-6.25 × 102 HeLa cells μL-1 for telomerase activity.

SIGNIFICANCE

In conclusion, our study demonstrated that the triggered-DNA nanomachine fulfills the requirements for rapid detection of telomerase activity in one-step under isothermal and enzyme-free conditions with excellent specificity, and its simple and stable structure makes it ideal for complex systems. These findings indicated the application prospect of DNA nanomachines in clinical diagnostics and provided new insights into the field of DNA nanomachine-based bioanalysis.

Recent advances in optical biosensing and imaging of telomerase activity and relevant signal amplification strategies

Telomerase as a new valuable biomarker for early diagnosis and prognosis evaluation of cancer has attracted much interest in the field of biosensors, cell imaging, and drug screening. In this review, we mainly focus on different optical techniques and various signal amplification strategies for telomerase activity determination. Fluorometric, colorimetry, chemiluminescence, surface-enhanced Raman scattering (SERS), and dual-mode techniques for telomerase sensing and imaging are summarized. Signal amplification strategies include two categories: one is nucleic acid-based amplification, such as rolling circle amplification (RCA), the hybridization chain reaction (HCR), and catalytic hairpin assembly (CHA); the other is nanomaterial-assisted amplification, including metal nanoclusters, quantum dots, transition metal compounds, graphene oxide, and DNA nanomaterials. Challenges and prospects are also discussed to provide new insights for future development of multifunctional strategies and techniques for in situ and in vivo analysis of biomarkers for accurate cancer diagnosis.

Assessment of MYC and TERT copy number variations in lung cancer using digital PCR

OBJECTIVE

Lung cancer is the second most frequent cancer type and the most common cause of cancer-related deaths worldwide. Alteration of gene copy numbers are associated with lung cancer and the determination of copy number variations (CNV) is appropriate for the discrimination between tumor and non-tumor tissue in lung cancer. As telomerase reverse transcriptase (TERT) and v-myc avian myelocytomatosis viral oncogene homolog (MYC) play a role in lung cancer the aims of this study were the verification of our recent results analyzing MYC CNV in tumor and non-tumor tissue of lung cancer patients using an independent study group and the assessment of TERT CNV as an additional marker.

RESULTS

TERT and MYC status was analyzed using digital PCR (dPCR) in tumor and adjacent non-tumor tissue samples of 114 lung cancer patients. The difference between tumor and non-tumor samples were statistically significant (p < 0.0001) for TERT and MYC. Using a predefined specificity of 99% a sensitivity of 41% and 51% was observed for TERT and MYC, respectively. For the combination of TERT and MYC the overall sensitivity increased to 60% at 99% specificity. We demonstrated that a combination of markers increases the performance in comparison to individual markers. Additionally, the determination of CNV using dPCR might be an appropriate tool in precision medicine.

Measuring telomerase activity using TRAP assays

Telomerase is a reverse transcriptase that consists of the telomerase reverse transcriptase (TERT) protein and the telomerase RNA component TERC which also harbors the template region for telomere synthesis. In its canonical function the enzyme adds single-stranded telomeric hexanucleotides de novo to the ends of linear chromosomes, telomeres, in telomerase-positive cells such as germline, stem- and cancer cells. This potential biochemical activity of telomerase can be measured with the help of a telomerase repeat amplification protocol (TRAP) which often includes a PCR amplification due to the low abundance of telomerase in most cells and tissues. The current chapter describes various TRAP methods to detect telomerase activity (TA) using gel-based methods, its advantages and deficits, how to perform an ELISA-based TRAP assay and how best to interpret its results. Since development of the TRAP assay in 1994, there have been numerous modifications and adaptations of the method from real-time PCR analysis, isothermal amplification and nanotechnology to CRISPR/Cas-based methods which will be briefly mentioned. However, it is not possible to cover all different TRAP methods and thus there is no comprehensiveness claimed by this chapter. Instead, the author describes various aspects of using TRAP assays including required controls, sample preparation, etc. in order to avoid pitfalls and set-backs in applying this rather complex and demanding technique. The TRAP assay is particularly important to support clinical diagnosis of cancer, analyze tumor therapy as well as to evaluate various approaches to inhibit TA as a form of anti-cancer therapy.

Ultrasensitive Dual-Signal Detection of Telomerase and MiR-21 Based on Boolean Logic Operations

Telomerase and micro-RNAs (miRNAs) are simultaneously upregulated in a variety of tumor cells and have emerged as promising tumor markers. However, sensitive detection of telomerase and miRNAs in situ remains a great challenge due to their low expression levels. Here, we designed a Boolean logic "AND" signal amplification strategy based on functionalized ordered mesoporous nanoparticles (FOMNs) to achieve ultrasensitive detection of telomerase and miR-21 in living tumor cells. Briefly, the strategy uses telomerase as an input to enable the release of DNA3-ROX-BHQ hairpins by making the wrapping DNA1 form a DNA-a hairpin with the joint participation of dNTPs. Subsequently, DNA2-Ag, DNA3-ROX-BHQ, and the second input miR-21 participated in hybridization chain reaction to amplify fluorescence and Raman signals. Experimental results showed the intensity of output dual signals relevant to the expression levels of telomerase and miR-21. The Ag nanoparticles (AgNPs) not only enhanced the fluorescence signals but also allowed to obtain more sensitive Raman signals. Therefore, even if expression of tumor markers is at a low level, the FOMN-based dual-signal logic operation strategy can still achieve sensitive detection of telomerase and miR-21 in situ. Furthermore, FOMNs can detect miR-21 expression levels in a short time. Consequently, this strategy has a potential clinical application value in detection of tumor markers and the assessment of tumor treatment efficacy.

In situ imaging of intracellular human telomerase RNA with molecular beacon-functionalized gold nanoparticles

Since the expression level of human telomerase RNA (hTR) in tumor cells is much higher than that in normal cells, the determination of hTR is of prime importance in biological research of tumors. In this work, we report molecular beacon-functionalized gold nanoparticles for hTR imaging in live cells. The molecular beacon has a loop-and-stem structure with hTR recognition sequences and a red fluorophore Cy5. In the presence of hTR, the hTR sequence could be hybridized with the loop of molecular beacon to form a duplex DNA chain and thus the fluorescence state switched from "off" to "on". After co-incubation with cells, the probe could readily permeate into cells, leading to the in situ imaging of intracellular hTR. The proposed approach could be used to differentiate tumor cells from normal ones and assess hTR expression levels in different tumor cells. Furthermore, the proposed approach allowed us to dynamically monitor the expression level of hTR in live cells and holds great potential for application in tumor diagnosis and hTR-related drug delivery.

Studies of hTERT DNA methylation assays on the human age prediction

As an important aspect of epigenetics, DNA methylation has been proven to be suitable for forensic DNA analysis. By detecting changes in DNA methylation, it is desirable to construct a model of age patterns associated with it to infer the age of the individual. The hTERT gene methylation is closely related to tumors, but there are few reports on the relationship between hTERT gene promoter methylation and age. In this study, we utilized the methylation-specific polymerase chain reaction and real-time PCR (relative quantification and absolute quantification) approach to explore the connection between hTERT DNA methylation and age prediction. We fit three models for age prediction based on methylation assay for 90 blood samples from donors aged 1-79 years old. Among them, the model of absolute quantification of real-time enabled the age prediction with R² = 0.9634. We verified the linear regression model with a validation set of 30 blood samples where prediction average error was 4.29 years. Generally, this reliable method improves the DNA methylation analysis of forensic samples.

Multivalent Self-Assembled DNA Polymer for Tumor-Targeted Delivery and Live Cell Imaging of Telomerase Activity

The efficient detection and in situ monitoring of telomerase activity is of great importance for cancer diagnosis and biomedical research. Here we report for the first time that the development of a novel multivalent self-assembled DNA polymer, constructed through telomerase primer sequence (ITS) triggered hybridization chain assembly using two functional hairpin probes (tumor-trageting aptamer modified H1 and signal probe modified H2), for sensitive detection and imaging of telomerase activity in living cells. After internalizing into the tumor cells by multivalent aptamer targeting, the ITS on DNA polymers can be elongated by intracellular telomerase to generate telomere repeat sequences that are complementary with the signal probe, which can proceed along the DNA polymers, and gradually light up the whole DNA polymers, leading to an enhanced fluorescence signal directly correlated with the activity of telomerase. Our results demonstrated that the developed DNA polymer show excellent performance for specifically detecting telomerase activity in cancer cells, dynamically monitoring the activity change of telomerase in response to telomerase-based drugs, and efficiently distinguishing cancer cells from normal cells. The proposed strategy may afford a valuable tool for the monitoring of telomerase activity in living cells and have great implications for biological and diagnostic applications.

Quantum dot-based electrochemical biosensor for stripping voltammetric detection of telomerase at the single-cell level

Human telomerase is responsible for the maintenance of chromosome end structures and is a valuable biomarker for malignant growth. However, the accurate measurement of telomerase activity at the single-cell level has remained a great challenge. Here we develop a simple quantum dot (QD)-based electrochemical biosensor for stripping voltammetric detection of telomerase activity at the single-cell level. We designed a thiol-modified capture DNA which may be immobilized on the gold electrode by the gold-sulfur bond. The presence of telomerase enables the addition of the telomere repeats of (TTAGGG)_n to the 3' end of the primer, accompanied by the incorporation of abundant biotins in the extension product with the assistance of the biotin-tagged dATP. The subsequent hybridization of extension product with the capture DNA and the addition of streptavidin-coated QDs induce the assembly of large amounts of QDs onto the electrode via specific biotin-streptavidin binding. After the acidic dissolution of QDs, the released Cd (II) can be simply quantified by anodic stripping voltammetry (ASV). Due to the introduction of large amounts of QDs by telomerase-induced primer extension reaction and the synergistic signal amplification induced by the release of Cd (II) from the QDs, this biosensor can detect telomerase activity at the single-cell level without the involvement of any thermal cycling and extra enzymes for signal amplification. Moreover, this assay exhibits a large dynamic range over four orders of magnitude and it is very simple without the involvement of specific hairpin probe design and complicated labelling, holding great potential in point-of-need testing.

Sticky-flares for in situ monitoring of human telomerase RNA in living cells

Human telomerase RNA (hTR), a template of telomerase for telomeric repeat synthesis, was used to reflect the telomerase activity and act as a potential target of antitumor therapy. Here, we report a novel DNA-conjugated AuNP probe termed sticky-flares for the in situ detection of intracellular human telomerase RNA. The sticky-flares probe is capable of entering living cells directly without any auxiliary and recognizing the binding domain of human telomerase RNA. On recognition, the fluorophore-modified recognition flares can specifically bind to the target, separate from the sticky-flares and act as a fluorescent reporter to quantify and dynamically profile human telomerase RNA in living cells. We envision that the sticky-flares probe would be a valuable platform to investigate the function and regulation of hTR in antitumor therapy and hTR-related drug invention.

Immunohistochemical and Molecular Study of Radiation-Induced Multiple Meningiomas with Pleural and Pulmonary Metastasis

In the present study, the telomerase activity and the putative alterations of genes involved in cell-cycle control (p53, Fas and pRb) were investigated in a radiation-induced meningioma with multiple recurrences and pleural-pulmonary metastases (the patient, a 34-year-old male, had a history of carcinoma of the tongue of testicular lymphocytic lymphoma). Expression of VEGF and vasculature pattern were also studied. Expression of VEGF, pRb and p53 were evaluated by immunohistochemistry on formalin-fixed, paraffin-embedded samples of the tumor. VEGFmRNA was determined by competitive PCR. Fas, FasL and hTERT were evaluated by RT-PCR. Telomerase activity was examined by the TRAP assay. An intense vascularization was observed, supported by high expression of VEGFmRNA (isoforms 121 and 165). pRb and p53 were overexpressed. Fas was undectable with PCR, whereas FasL was positive. Furthermore, the lesion showed an elevated telomerase activity (TPG, 22), according to the high expression of hTERT. These findings emphasized that even among generally benign neoplasms, such as meningiomas, some highly malignant tumors may develop, as in our case, in which several mechanisms were activated in the cancer progression to guarantee the immortalization of cellular clones (angiogenic phenomenon, activation of telomerase and of anti-apoptotic mechanisms) and the blood spread. Thus, the data illustrate the importance of searching for genetic aberrations (which are a hallmark of malignancy) in meningiomas, as predictive and reliable factors of the possibility to recur and to metastasize.

Clinical significance of PSMA, TERT and PDEF in malignant tumors of the prostate

OBJECTIVE

To investigate the clinical significance of the expression of PSMA (prostate specific membrane antigen), TERT (telomerase reverse transcriptase), and PDEF (prostate derived Ets factor) in malignant tumors of the prostate.

PATIENTS AND METHODS

The study was conducted with paraffin slices from 33 specimens of malignant tumors of the prostate and 17 of normal tissue. We found high levels of PSMA, TERT, and PDEF protein by Western blot and immunofluorescence in the malignant tumor of the prostate. We also detected upregulation of PSMA, TERT, and PDEF mRNA in the malignant tumor of the prostate, suggesting complex regulation of these three genes in prostate cancer.

RESULTS

Variance analysis showed statistically significant differences comparing the expression of PSMA, TERT, and PDEF in the malignant tumor of the prostate and normal tissues. The high expression of PSMA, TERT, and PDEF in the malignant tumor of the prostate suggests the important roles of these three factors in the occurrence and development of the malignant tumors of the prostate.

CONCLUSIONS

PSMA, TERT, and PDEF may serve as a reference for clinical diagnosis and as potential targets for the malignant tumor of the prostate therapeutics.

Evaluation of Telomerase in Canine Mammary Tissues by Immunohistochemical Analysis and a Polymerase Chain Reaction-Based Enzyme-Linked Immunosorbent Assay

The enzyme telomerase is considered a potential marker for neoplastic tissue and is used as a diagnostic and prognostic tool in clinical medicine and therapeutics. For this reason, the possible role of telomerase activation in the process of malignant transformation is currently the subject of intense research efforts. The focus of the study reported here was to detect telomerase in 37 canine mammary samples, by comparing two methods: immunohistochemical (IHC) analysis for detecting the catalytic subunit of the enzyme, telomerase reverse transcriptase (TERT), and the telomeric repeat amplification protocol–enzyme-linked immunosorbent assay (TRAP-ELISA), a polymerase chain reaction (PCR)-based technique that uses a colorimetric detection method. Using the TRAP-ELISA, samples were considered positive when they yielded a difference of at least 0.2 absorbance units between the readings at 450 nm versus 690 nm wavelength. On the basis of this criterion, 18 negative and 19 positive cases were obtained. Specific immunohistochemical staining was observed mainly in the nucleoli, to a lesser extent in the nuclei, and rarely in the cytoplasm of epithelial cells. A sample was considered positive when at least 10% of the epithelial cells had specific staining. The Pearson correlation between the TRAP-ELISA and IHC results was significant only when IHC nucleolar ( r = 0.53, P < 0.01) or nuclear ( r = 0.36, P < 0.05) staining or their combination ( r = 0.58, P < 0.01) was considered. Thus, IHC staining of nucleoli and nuclei can be considered as an alternative method to the TRAP-ELISA. The detection of telomerase in normal mammary gland and fibrocystic mastopathy using both methods does not support the idea that telomerase may be used as a specific marker of mammary neoplasia in dogs.

[Comparison between poly hydroxy acrylic acid and Van-clear replacing the traditional reagents to detect the cervical hTERC genes by adopting FISH technique]

OBJECTIVE

To observe the difference of the human telomeres RNA component (hTERC) genes' amplification in the cervical tissue by applying the environment-friendly fixative poly hydroxy acrylic acid and the transparent dewaxing solution Van-clear separately or jointly to replace the traditional fixative 4% (volume fraction) neutral buffered formalin and the conventional transparent dewaxing solution xylene in the use of fluorescence in situ hybridization (FISH) for detection.

METHODS

In the study, 255 cases of cervical tissue specimens submitted by the Department of Gynecology in Zhongshan Boai Hosipital were collected from Mar. 2013 to Apr. 2015. Four samples were taken from the same lesion site. All the cases were divided into 4 groups and named group A, B, C, and D. Group A used 4% neutral buffered formalin fixed and xylene dewaxing to make slices. Group B used poly hydroxy acrylic fixed and xylene dewaxing to make slices. Group C used 4% neutral buffered formalin fixed and Van-clear transparent to make slices. Group D used poly hydroxy acrylic fixed and Van-clear transparent dewaxing to make slices. The amplification of hTERC genes in the four groups of cervical specimens was also detected by FISH technique.

RESULTS

When the hTERC genes were detected by FISH method under the fluorescence microscope, it was obvious that the tissue profile and the background of group A, B, C and D were all clear. The probe was fixed in the accurate position so that the bright red or green fluorescence signals were easily found in these four groups. Compared with the positive rate of group A, there was no statistical significance in that of group B, C and D (P>0.05). At the same time, the coincidence rate of the FISH results was high, which showed that the new environment-friendly reagent had no significant difference in the detection of cervical hTERC genes by FISH technique.

CONCLUSION

It is possible for the environment-friendly reagent poly hydroxy acrylic acid and Van-clear to replace 4% neutral buffered formalin and xylene separately or jointly to detect the cervical hTERC genes by adopting FISH technique.

Fluorescence detection of telomerase activity in cancer cell extracts based on autonomous exonuclease III-assisted isothermal cycling signal amplification

Based on the extension reaction of a telomerase substrate (TS) primer in the presence of the telomerase, strand-displacement process to perform more stable longer duplex chain, and stepwise hydrolysis of mononucleotides from the blunt or the recessed 3'-hydroxyl termini of duplex DNA in the presence of Exonuclease III (Exo III), an amplified fluorescence detection of telomerase activity in the cancer cells was described in this manuscript. A fluorescence probe DNA, a quencher DNA, and a TS primer were mixed to construct a three-chain DNA structure and a two-chain DNA structure because the amount of the TS primer was less than the other two DNA. In the presence of the telomerase, the quencher DNA was replaced from the probe DNA and the telomerase activity could be determined with the fluorescence enhancement. The telomerase activity in HeLa extracts equivalent to 6-2000 cells was detected by this method. Moreover, the strategy was further proved by using telomerase extracted from Romas cells. With the multiple rounds of isothermal strand displacement and the hydrolysis process, constituted consecutive of signal amplification for the novel detection paradigm that allowed measuring of telomerase activity in crude cancer cell extracts confirmed the reliability and practicality of the protocol, which reveal this platform holds great promise in the biochemical assay for the telomerase activity in early diagnosis for cancers.

Colorimetry and SERS dual-mode detection of telomerase activity: combining rapid screening with high sensitivity

As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and surface enhanced Raman scattering (SERS) dual-mode telomerase activity detection method, which has several distinctive advantages. First, colorimetric functionality allows rapid preliminary discrimination of telomerase activity by the naked eye. Second, the employment of SERS technique results in greatly improved detection sensitivity. Third, the combination of colorimetry and SERS into one detection system can ensure highly efficacious and sensitive screening of numerous samples. Besides, the avoidance of polymerase chain reaction (PCR) procedures further guarantees fine reliability and simplicity. Generally, the presented method is realized by an "elongate and capture" procedure. To be specific, gold nanoparticles modified with Raman molecules and telomeric repeat complementary oligonucleotide are employed as the colorimetric-SERS bifunctional reporting nanotag, while magnetic nanoparticles functionalized with telomerase substrate oligonucleotide are used as the capturing substrate. Telomerase can synthesize and elongate telomeric repeats onto the capturing substrate. The elongated telomeric repeats subsequently facilitate capturing of the reporting nanotag via hybridization between telomeric repeat and its complementary strand. The captured nanotags can cause a significant difference in the color and SERS intensity of the magnetically separated sediments. Thus both the color and SERS can be used as indicators of the telomerase activity. With fast screening ability and outstanding sensitivity, we anticipate that this method would greatly promote practical application of telomerase-based early-stage cancer diagnosis.

Visual detection of telomerase activity with a tunable dynamic range by using a gold nanoparticle probe-based hybridization protection strategy

We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs.

Construction and expression of retroviral vector pLEGFP-N1-TERT in preparation of seed cells for skin tissue engineering

OBJECTIVE

To construct the retroviral vector pLEGFP-N1-telomerase reverse transcriptase (TERT) and to investigate the expression of TERT in neonatal mouse hypodermal cells.

METHODS

The polymerase chain reaction (PCR)-amplified TERT gene was inserted into plasmid pLEGFP-N1. The positive clone was identified by restriction enzyme digestion and sequencing, then was transfected into packaging cells to produce retrovirus particles. Neonatal mouse hypodermal cells were infected with the virus to generate a stable cell line. The TERT mRNA expression level, telomerase activity, and enhanced green fluorescent protein (EGFP) expression level were analyzed.

RESULTS

Retroviral vector pLEGFP-N1-TERT was constructed successfully, and a stable cell line of neonatal mouse hypodermal cells expressing EGFP was established. Western blot and immunohistochemical assay showed that the expression level of TERT was significantly elevated in the neonatal mouse hypodermal cells.

CONCLUSIONS

A high titer of retrovirus pLEGFP-N1-TERT mediates high-level expression of the exogenous TERT gene in the neonatal mouse hypodermal cells. This protocol has potential applications for skin tissue engineering and cell transplantation therapy.

Immunohistochemical expression of telomerase in patients with non-small cell lung cancer: prediction of metastasis and prognostic significance

AIM

To detect telomerase reverse transcriptase (TERT) expression in tissue and metastatic and non-metastatic lymph node samples from patients with non-small cell lung cancer; to evaluate whether TERT expression is correlated with pathological and clinical features, and/or patient survival times; to determine differences between TERT expression in metastatic and non-metastatic lymph nodes.

PATIENTS AND METHODS

Tumor tissue samples from 17 patients with squamous cell lung cancer and 11 patients with adenocarcinoma diagnosed between 2003 and 2004 were included in this study. All patients were diagnosed at our hospital and had samples stored in the pathology archive. Additionally, dissected lymph node samples, with and without metastases, were studied. Telomerase Gene Tex, Inc, Irvine, CA USA (TERT (2C4) antibody), Universal Kit (Lab Vision, Newmarket, UK) were used for immunohistochemical staining. Statistical analyses were performed using SPSS 17.0 statistical software.

RESULTS

TERT was positive in 18/28 of the samples, regardless of the histological tumor type. There was no significant correlation between TERT expression in lymph nodes with metastasis and clinical stage, histological type, tumor differentiation, or survival time.

CONCLUSION

TERT expression may be used as a target for therapy. It may also be helpful in predicting metastasis but not in predicting survival time.

The impact of age on the physical and cellular properties of the human limbal stem cell niche

The limbal niche in the corneoscleral junction of the eye, habitat of the limbal epithelial stem cells (LESC), facilitates corneal epithelial regeneration by providing physical support and chemical signalling. Anatomical structures within the limbus, namely, limbal epithelial crypts and focal stromal projections, are believed to function as a putative niche for LESCs. In this study, the impact of age on the topography of this niche was investigated. Also, the relationship between niche topography and limbal epithelial cell phenotype was assessed. Ex vivo imaging of the limbus in cadaveric tissue of donors aged from infancy to 90 years was carried out using electron and confocal microscopy. The data suggested that the area occupied by the crypts was sharply reduced after the age of 60 years. The niche microstructures also became smoother with donor age. The phenotypic assessment of cultured limbal epithelial cells harvested from donors of different ages showed that the levels of putative stem cell markers as well as telomerase activity and telomere length remained unchanged, regardless of niche topography. However, the colony forming efficiency of the cultures was significantly reduced with age (p < 0.05). This is the first comprehensive study of the effect of age on the structural and phenotypic characteristics of the human limbal niche. The results have a significant biological value as they suggest a correlation of limbal architecture with decline of re-epithelialisation rate in older patients. Overall, the data also suggest that LESCs harvested from younger donors may be more suitable for cultured LESC therapy production.

New horizons for diagnostics and therapeutic applications of graphene and graphene oxide

Graphene, a one-atom-thick two-dimensional (2D) layer of sp(2) -bonded carbon, has received worldwide attention owing to its extraordinary physical and chemical properties. Recently, great efforts have been devoted to explore potential applications of graphene and its oxide in life science, especially in disease-related diagnostics, near-Infrared (NIR) phototherapy and imaging. Here we will introduce recent advances and new horizons in this area, and focus on the rising progress on NIR photothermal therapy for cancer and Alzheimer's disease (AD), human telomerase detection, stem cell proliferation and differentiation on graphene substrate, diagnosis of cancer cell and related biomarkers, drug/nucleotide/peptide delivery and cell imaging, which have not been comprehensively reviewed. We hope to provide an outlook to the applications of graphene and its oxide, especially on the new horizons in this field, and inspire broader interests across various disciplines.

c-MYC and h-TERT co-expression in colon adenocarcinoma: a tissue microarray digitized image analysis

PURPOSE

c-MYC oncogene is frequently deregulated by amplification in colon adenocarcinoma. c-MYC also activates telomerase by inducing expression of its catalytic subunit (h-TERT). Furthermore, telomerase activation plays a crucial role in tumorigenesis by sustaining cellular immortality. Our aim was to evaluate the significance of c-MYC and h-TERT co-expression in colon adenocarcinoma.

METHODS

Sixty paraffin embedded primary colon adenocarcinomas were cored at 1.5 mm diameter and transferred to one microarray block. Immunohistochemistry was performed using anti-h-TERT, and c - MYC antibodies. A quantitative digitized macro was performed to evaluate their expression.

RESULTS

c-MYC and h-TERT overexpression was observed in 27 (45%) and 28 (46.6%) cases, respectively. Co-over expression of those genes was observed in 17 (28.3%) cases and found to be statistically significant (p=0.001). The results also showed a strong association between c-MYC and grade of differentiation of the examined neoplasms (p=0.0217rpar;.

CONCLUSION

Simultaneous c-MYC and h-TERT deregulation is a relatively frequent genetic event in colon adenocarcinoma. Because c-MYC overexpression is correlated with progressive disease - due to colon adenocarcinoma dedifferentiation - inhibition of its activity combined with h-TERT regulated expression is a new target for novel therapeutic regimens.

Predictors of outcome in an AIEOP series of childhood ependymomas: a multifactorial analysis

Several molecular biomarkers have been suggested as predictors of outcome for pediatric ependymomas but deserve further validation in independent case series. We analyzed intracranial ependymomas belonging to a series of 60 patients prospectively treated according to the protocol sponsored by the Italian Association of Pediatric Hematology-Oncology. We used a tissue microarray to analyze nucleolin (NCL), cyclin-dependent kinase inhibitor 2A (CDKN2A), tumor protein 53 (TP53), and epidermal growth factor receptor (EGFR) by immunohistochemistry and by 1q gain by fluorescent in situ hybridization. The mRNA expression levels of EGFR, human telomerase reverse-transcriptase (HTERT), and Prominin 1 (PROM 1)/CD133 were evaluated by quantitative real-time PCR from cases with fresh-frozen tumor material available. Univariate and multivariate analyses of updated clinical data confirmed the prognostic significance of surgery (P < .01) and tumor grading (P < .05) for both relapse-free survival (RFS) and overall survival (OS). Among biomolecular markers, HTERT mRNA expression emerged with the strongest association with OS at multivariate analysis (hazard ratio [HR] = 9.9; P = .011); the 5-year OS was 84% versus 48% in the subgroups with HTERT median value <6 versus ≥ 6, respectively (P = .005). Five-year RFS was 46% versus 20% in the subgroups with low versus high NCL protein expression, respectively (P = .004), while multivariate Cox analyses gave suggestively high HRs for high versus low NCL (HR = 1.9; P = .090). The other genes tested were not significant at multivariate analyses, and genetic alterations of CDKN2A, TP53, EGFR, and HTERT loci were rare. The PROM1/CD133 cancer stem cell marker was strongly expressed at both RNA and protein levels in a substantial fraction of cases and was suggestively associated with a more indolent form of the disease. We conclude that NCL and HTERT represent the strongest prognostic biomarkers of RFS and OS, respectively, in our ependymoma case series.

The value of expression of EGFR, telomerase and topoisomerase IIα in malignant effusion smears before and after chemotherapy

PURPOSE

To evaluate the significance of expression of epidermal growth factor receptor (EGFR), telomerase and topoisomerase IIα (topo IIα) in cells of malignant effusions of patients under chemotherapy.

METHODS

We studied the expression of EGFR, telomerase and topo IIα in malignant effusion smears of 95 cancer patients before and after chemotherapy. Immunocytochemical and in situ hybridization techniques were applied.

RESULTS

Positive expression before chemotherapy of telomerase, topo IIα and EGFR was found in 64.2, 63.2 and 69.5% of the cases, respectively; the expression of these markers following chemotherapy was 43.6, 28.2 and 53.8%, respectively. The stronger prognostic factor affecting survival before chemotherapy was telomerase (p=0.0002), whereas after chemotherapy the strongest factor was EGFR (p<0.0001). A positivity for all three markers following chemotherapy was associated with shorter survival compared with positivity for only 1 or 2 markers (p<0.0001) or with a negative expression.

CONCLUSION

It seems that expression of EGFR, telomerase and topo IIα in malignant effusion smears is adversely affecting prognosis and survival.

An exonuclease III and graphene oxide-aided assay for DNA detection

We have developed a novel DNA assay based on exonuclease III (ExoIII)-induced target recycling and the fluorescence quenching ability of graphene oxide (GO). This assay consists of a linear DNA probe labeled with a fluorophore in the middle. Introduction of target sequence induces the exonuclease III catalyzed probe digestion and generation of single nucleotides. After each cycle of digestion, the target is recycled to realize the amplification. Finally, graphene oxide is added to quench the remaining probes and the signal from the resulting fluorophore labeled single nucleotides is detected. With this approach, a sub-picomolar detection limit can be achieved within 40 min at 37°C. The method was successfully applied to multicolor DNA detection and the analysis of telomerase activity in extracts from cancer cells.

Label-free ultrasensitive detection of human telomerase activity using porphyrin-functionalized graphene and electrochemiluminescence technique

Using porphyrin-functionalized graphene, we construct a PCR-free, low-cost, rapid, and electrochemiluminenscence (ECL) assay for detection of telomerase activity that has been demonstrated in six different cell lines and can be used as initial screening of G-quadruplex DNA binding agents and telomerase inhibitors. This ECL sensor shows highly sensitive for detection of telomerase with the detection limit as low as 10 HeLa cells mL(-1) .

Comparison of clinicopathological features and hRad21 expression between telomerase-dependent and telomerase-independent colorectal cancer

BACKGROUND/AIMS

To investigate the difference of clinicopathological features and expression of hRad21 between telomerase-dependent and telomerase-independent colorectal cancer (CRC).

METHODOLOGY

By detecting telomerase activity of surgical specimens using the TRAP method, 251 cases diagnosed as CRC were allocated to the telomerase-dependent and telomerase-independent groups, as appropriate. Expression difference of hRad21 between the two groups was investigated by immunohistochemistry. All patients were followed-up and clinicopathological features were compared.

RESULTS

There were 38 and 213 cases in the telomerase-independent and telomerase-dependent groups, respectively. Expression of hRad21 in the telomerase-independent group is higher than that in the telomerase-dependent group. Clinicopathological analysis indicated that invasion of the rectal wall (T stage) in the telomerase-independent group was more superficial than that in the telomerase group (p=0.022). Age, gender, location of tumor, serum CEA, CA19-9, lymph node metastasis, distant metastasis, TNM stage and tumor differentiation showed no difference between groups. Follow-up indicated a significantly shortened survival time in the telomerase-dependent group (p=0.006).

CONCLUSIONS

Most CRC (84.9%) maintain their telomeres by telomerase, while a minority (15.1%) do so by telomerase-independent pathway. Depth of invasion in the telomerase-independent group was lower than that the telomerase group. Follow-up indicated that patients of telomerase-independent group had a higher survival rate than that of telomerase-dependent group. Expression of hRad21 in telomerase-independent CRC is higher than that of telomerase-dependent group, which suggested that hRad21 may be an important protein involved in telomerase-independent telomere maintenance mechanisms.

Sirtuin 1 is upregulated in a subset of hepatocellular carcinomas where it is essential for telomere maintenance and tumor cell growth

Hepatocellular carcinoma (HCC) is a highly malignant tumor with a poor prognosis. Treatment of HCC is complicated by the fact that the disease is often diagnosed at an advanced stage when it is no longer amenable to curative surgery, and current systemic chemotherapeutics are mostly inefficacious. Sirtuin 1 (SIRT1) is a class III histone deacetylase that is implicated in gene regulations and stress resistance. In this study, we found that SIRT1 is essential for the tumorigenesis of HCC. We showed that although SIRT1 was expressed at very low levels in normal livers, it was overexpressed in HCC cell lines and in a subset of HCC. Tissue microarray analysis of HCC and adjacent nontumoral liver tissues revealed a positive correlation between the expression levels of SIRT1 and advancement in tumor grades. Downregulation of SIRT1 consistently suppressed the proliferation of HCC cells via the induction of cellular senescence or apoptosis. SIRT1 silencing also caused telomere dysfunction-induced foci and nuclear abnormality that were clearly associated with reduced expressions of telomerase reverse transcriptase (TERT), and PTOP, which is a member of the shelter in complex. Ectopic expression of either TERT or PTOP in SIRT1-depleted cells significantly restored cell proliferation. There was also a positive correlation between the level of induction of SIRT1 and TERT [corrected] in human HCC. Finally, SIRT1-silencing sensitized HCC cells to doxorubicin treatment. Together, our findings reveal a novel function for SIRT1 in telomere maintenance of HCC, and they rationalize the clinical exploration of SIRT1 inhibitors for HCC therapy.

Diffuse malignant peritoneal mesothelioma: systematic review of clinical management and biological research

Diffuse malignant peritoneal mesothelioma (DMPM) is an uncommon and locally aggressive tumor with poor prognosis. Currently, no standard therapy is available. The biology of this disease is still poorly understood. We performed a systematic search of relevant studies on clinical management and biological research of DMPM. Trials were selected using a predetermined protocol. The current evidence suggests that cytoreductive surgery (CRS) and perioperative intraperitoneal chemotherapy (PIC) results in improved survival. Biological understanding of DMPM is currently evolving.

[Possibility of using the determination of minimal residual disease in pancreatic adenocarcinoma using real-time RT-PCR--a pilot study]

BACKGROUND

Minimal residual disease in patients with pancreatic cancer is defined as the presence of isolated tumor cells in the patient's body, in which the primary tumor was removed and is currently without clinical signs of disease. These isolated tumor cells may be described as precursors of micrometastases. Assessment of MRD in patients with this highly malignant disease could eliminate burdensome implementation of surgery in patients with systematic dissemination of molecular disease and provide a more precise prognosis. METHODS AND RESULTS; The study to date included 70 patients operated on with curative intent for carcinoma of the pancreas. Samples of peripheral and portal blood, bone marrow, peritoneal lavage and of the tumor itself were analyzed by real-time PCR which measured the expression of hTERT (telomerase), EGFR1 (receptor for epidermal growth factor) and CEA (carcinoembryonic antigen). The expression of these markers was correlated with clinicopathological characteristics and survival parameters. We found a statistically significant association between EGFR expression levels in the portal blood and clinical stage--patients with advanced disease have a higher expression of EGFR in the portal stream and peritoneal lavage in contrast to patients without the presence of metastases.

CONCLUSIONS

The results of this pilot study demonstrated a high sensitivity and specificity of the RT-PCR method for detecting circulating tumor cells in patients with pancreatic cancer. By utilizing this methodology, we are able to provide prognostic value of minimal residual disease and its significance for the indication of radical surgery for pancreatic cancer.

[hTERT promoter-based conditionally replicative adenoviruses are useful for lung cancer and other solid cancer treatment]

Treatment of advanced SCLC remains one of the major challenges in current medicine because of the high morbidity and mortality of the disease. Advanced stage lung cancer is refractory to conventional therapies and it also has an extremely poor prognosis. As a result, new therapeutic approaches are needed. Telomere maintenance to the regulation of replicative life span strongly implies that alterations in telomere biology play an important role during malignant transformation. Cancers that exhibit high levels of telomerase activity, such as all of the small-cell lung cancers were examined in a previous study. In this study, we turned the expression of hTERT by tumors to a therapeutic advantage using a conditionally replication-competent adenovirus (CRAd) in which the expression of E1 is controlled by the hTERT promoter. This virus achieved good levels of viral replication in SCLC cells and induced a substantial anti-cancer effect in vitro and in vivo. As a further enhancement the cancer cell killing effect was improved with a tropism modification of the virus to express the knob domain of Ad3, and this improved infectivity for cancer cells. Conversely, the hTERT promoter has low activity in normal tissues, and the CRAd caused no damage to normal lung fibroblast cells. Since the telomerase activity is common in many types of cancers, these CRAds may be applicable to a wide range of tumors. We concluded that the use of hTERT promoter-based CRAds may be a potentially effective strategy for cancer treatment.

Immunohistochemical expression of ubiquitin and telomerase in cervical cancer

Ubiquitin and telomerase immunohistochemical expression patterns in cervical cancer were compared with normal cervical tissue samples. Eighty-one cervical cancer cases and 22 normal exo-endocervical tissue were examined with polyclonal antibody for ubiquitin and 44G12 clone for telomerase using tissue microarrays. The results were interpreted using a semiquantitative scale The average age of patients was 50.67 years. The most frequent histological types were moderately differentiated epidermoid carcinoma (43.5%), according to the degree of differentiation, and endocervical adenocarcinoma (42.1%). Immunohistochemical findings were as follows: 98.7% of cervical cancers showed immunoexpression for ubiquitin and 52.6% for telomerase. Statistically significant differences were found in tumor immunoreactivity when compared with control tissue (p < 0.0007) for both biomarkers. There was no significant difference in biomarker expression at different histological types of tumors, although telomerase was less expressed in endocervical adenocarcinoma. Our findings confirm that abnormal immunoexpression pattern of ubiquitin and telomerase is common in HPV-positive cervical cancer, indicating the existence of an intense degradation of proteins, subsequent cellular immortalization and maintenance of the malignant phenotype.

Immortalization and Characterization of Porcine Ventricular Endocardial Endothelial Cells

Endocardial endothelial cells (EECs), which form the inner lining of the cavities of the heart, are a distinct cell population whose dysfunction can be critical in pathological conditions of heart. Insights into the role and organization of these cells in pathological states of the heart are limited mainly due to a dearth of experimental models. To date no endocardial endothelial cell line is available. The authors attempted to immortalize porcine ventricular EECs by transfecting the cells with human telomerase reverse transcriptase (hTERT). EECs immortalized by ectopic expression of hTERT exhibit phenotypic and functional characteristics similar to primary EECs. The EE cell line could be useful for the study of mechanisms involved in the interaction of EECs with the underlying myocardium and cardiac interstitium and as useful tools in understanding their role in diseased states of heart.

Telomerase activity determined by conventional telomeric repeat amplification protocol and reverse transcriptase‐polymerase chain reaction assay in ovarian lesions: A comparison of assays

OBJECTIVE

Telomerase is capable of restoring telomeric sequence lost during replication. No or low levels of telomerase activity are present in normal somatic cells, whereas up to 85-90% of all cancer cells express telomerase activity, suggesting telomerase as a possible tumor marker. The catalytic subunit, hTERT, correlates with the activity of the enzyme.

MATERIAL AND METHODS

Telomerase activity in ovarian tissue was measured by the functional telomeric repeat amplification protocol (TRAP)eze assay, and a quantitative reverse-transcriptase-polymerase chain reaction (RT-PCR) assay measuring the expression of the telomerase catalytic subunit, hTERT.

RESULTS

A weakly positive correlation was found between telomerase activity and severity of ovarian disease using the results of the TRAP assay, compared to a strongly positive correlation considering the results obtained in the RT-PCR assay. A statistically significant difference between the benign and borderline groups was present using the RT-PCR assay, allowing for screening for both borderline and primary malignant conditions with a specificity of 97% and a sensitivity of 68%. No significant statistical difference was found between telomerase activity in benign and borderline conditions when using the TRAP assay. When screening for primary malignancy, the specificity and sensitivity rates were 94% and 21%, respectively.

CONCLUSIONS

The RT-PCR assay allowed discrimination between benign and borderline and malignant cases, and thereby proved superior to the TRAP assay, which could not discriminate the benign cases from the borderline cases. This suggests that the RT-PCR assay may be useful in screening for both borderline and primary malignancy in ovarian lesions.

Identification and comparative analysis of telomerase RNAs from Candida species reveal conservation of functional elements

The RNA component of telomerase (telomerase RNA; TER) varies substantially both in sequence composition and size (from approximately 150 nucleotides [nt] to >1500 nt) across species. This dramatic divergence has hampered the identification of TER genes and a large-scale comparative analysis of TER sequences and structures among distantly related species. To identify by phylogenetic analysis conserved sequences and structural features of TER that are of general importance, it is essential to obtain TER sequences from evolutionarily distant groups of species, providing enough conservation within each group and enough variation among the groups. To this end, we identified TER genes in several yeast species with relatively large (>20 base pairs) and nonvariant telomeric repeats, mostly from the genus Candida. Interestingly, several of the TERs reported here are longer than all other yeast TERs known to date. Within these TERs, we predicted a pseudoknot containing U-A.U base triples (conserved in vertebrates, budding yeasts, and ciliates) and a three-way junction element (conserved in vertebrates and budding yeasts). In addition, we identified a novel conserved sequence (CS2a) predicted to reside within an internal-loop structure, in all the budding yeast TERs examined. CS2a is located near the Est1p-binding bulge-stem previously identified in Saccharomyces cerevisiae. Mutational analyses in both budding yeasts S. cerevisiae and Kluyveromyces lactis demonstrate that CS2a is essential for in vivo telomerase function. The comparative and mutational analyses of conserved TER elements reported here provide novel insights into the structure and function of the telomerase ribonucleoprotein complex.

The role of telomerase activity in predicting early recurrence of epithelial ovarian cancer after first-line chemotherapy: a prospective clinical study

PURPOSE OF INVESTIGATION

To investigate the value of telomerase activity (TA) in the detection of early recurrence in primary epithelial ovarian cancer (EOC).

METHOD(S)

In this study, TA was studied in 30 patients with Stage III EOC and 50 control patients with benign gynecological disease. All enrolled EOC patients had had primary cytoreductive surgery and six cycles of platinum-based first-line chemotherapy previously. Semi-quantative TA measurements were done by TRAP assay in ascites, taken at second-look surgery, of cancer patients and in peritoneal washings, taken during planned surgery, of the control group.

RESULT(S)

Early recurrence was diagnosed in ten EOC patients (33.3%). Mean TA was statistically higher in EOC patients than in patients with benign disease. However, the mean TA was insignificantly lower in early recurrent EOC patients than in disease-free EOC patients.

CONCLUSION(S)

The value of TA is limited in the detection of early recurrence in primary EOC.

Development of a marine fish model for studying in vivo molecular responses in ecotoxicology

A protocol for fixation and processing of whole adult marine medaka (Oryzias melastigma) was developed in parallel with in situ hybridization (ISH) and immunohistochemistry (IHC) for molecular analysis of in vivo gene and protein responses in fish. Over 200 serial sagittal sections (5microm) can be produced from a single adult medaka to facilitate simultaneous localization and quantification of gene-specific mRNAs and proteins in different tissues and subcellular compartments of a single fish. Stereological analysis (as measured by volume density, V(v)) was used to quantify ISH and IHC signals on tissue sections. Using the telomerase reverse transcriptase (omTERT) gene, omTERT and proliferating cell nuclear antigen (PCNA) proteins as examples, we demonstrated that it is possible to localize, quantify and correlate their tissue expression profiles in a whole fish system. Using chronic hypoxia (1.8+/-0.2 mgO(2)L(-1) for 3 months) as an environmental stressor, we were able to identify significant alterations in levels of omTERT mRNA, omTERT protein, PCNA (cell proliferation marker) and TUNEL (apoptosis) in livers of hypoxic O. melastigma (p<0.05). Overall, the results suggest that O. melastigma can serve as a model marine fish for assessing multiple in vivo molecular responses to stresses in the marine environment.

Bladder cancer biomarkers: current developments and future implementation

PURPOSE OF REVIEW

Bladder cancer biomarker development has advanced significantly over the last decade, but has not yet been able to make a significant impact in the diagnosis and management of the disease. Many available markers are suitable, but do not meet the expectations of physicians and patients. Patients do not want to compromise accuracy in diagnosing bladder cancer for less-invasive tests. The review highlights the latest developments in bladder cancer biomarkers, including markers developed over the last year, and comments on the high standards placed on these markers which have delayed their widespread implementation into the urologic field.

RECENT FINDINGS

New markers described in the last year include soluble Fas, urothelial carcinoma-associated 1 and human chorionic gonadotropin beta type II genes. The latter two markers represent the contribution of genomic technology to this field. Also described are updates to known markers, including long-term follow-up of hematuria screening, recent studies in DNA methylation for bladder cancer diagnosis and patient perspectives on bladder tumor markers.

SUMMARY

Biomarkers for bladder cancer have been intensively scrutinized over the last decade, but despite new findings and good performance characteristics, they are currently not accepted in clinical practice.

Real-time detection and quantification of telomerase activity utilizing energy transfer primers

A novel closed-tube format telomeric repeat amplification protocol specifically adapted to real-time detection and quantification of telomerase activity was developed. The assay utilizes energy transfer primers, which emit fluorescence only upon incorporation into polymerase chain reaction (PCR) amplification products. The assay, performed on a real-time detection instrument, is highly reproducible, sensitive, and specific. Telomerase activity in as few as 10 cultured cells can be quantified with a linear dynamic range more than 2.5 logs. In addition, the presence of potential PCR inhibitor(s) is readily detectable by inclusion of an internal PCR control labeled with a second color fluorescence.

Evaluation of combined h-TERT, bcl-2, and caspases 3 and 8 expression in cutaneous malignant melanoma based on tissue microarrays and computerized image analysis

PURPOSE

Deregulation of apoptotic pathways in cutaneous malignant melanoma appears to be correlated with chemoresistance and poor prognosis. Furthermore, telomerase (especially h-TERT) expression induces proliferation and also represents a potential target for vaccination regarding some types of malignancies.

MATERIALS AND METHODS

Using tissue microarrays (TMA) technology, 25 paraffin-embedded tissue samples of histologically confirmed malignant melanomas were cored at a diameter of 2 mm and re-embedded into one recipient block (final TMA density 24/25-96%). Immunohistochemistry (IHC) was performed by the use of anti-bcl-2, anti-caspase 3, anti-caspase 8 and anti- h-TERT antibodies. Protein expression levels were evaluated using a computerized image analysis system (CIA). SPSS (chi square test and inter-rater kappa) was used for statistical analysis.

RESULTS

Strong protein expression was observed in 1/24 (4.1%), 1/24 (4.1%), 2/24 (8.2%), and 4/24 (16.4%) cases regarding h-TERT, caspase 3, caspase 8 and bcl-2, respectively. Moderate was observed in 7/24 (29.1%), 8/24 (32.2%), 5/24 (20.2%), and 8/24(32.2%) cases, whereas reduced or absent expression demonstrated 16/24 (65%), 15/24 (60.2%), 17/24 (68.5%), and 12/24 (50 %) cases. Statistical significance was assessed correlating age to caspase 3 (p=0.05), Breslow's thickness to telomerase (p=0.013) and to bcl-2 (p=0.053), Clark's level to telomerase (p=0.008) and to bcl-2 (p=0.022), and finally ulceration to telomerase expression (p=0.007).

CONCLUSION

bcl-2 and telomerase expression are correlated to critical parameters of malignant melanoma, affecting its biological behavior. Furthermore, downregulation of proteins such as caspases 3/8, which normally induce apoptosis, is perhaps associated with resistance of the applied chemotherapeutic strategies in this type of malignancy.

[Theranostic application of telomerase-specific oncolytic adenovirus for human cancer]

Replication-selective tumor-specific viruses present a novel approach for treatment of neoplastic disease. Telomerase activation is considered to be a critical step in carcinogenesis and its activity correlates closely with human telomerase reverse transcriptase (hTERT) expression. We constructed an attenuated adenovirus 5 vector (Telomelysin, OBP-301), in which the hTERT promoter element drives expression of E1 genes. We further modified the E3 region of OBP-301 to contain green fluorescent protein (GFP) gene for monitoring viral replication (TelomeScan, OBP-401). When TelomeScan was intratumorally injected into human tumors orthotopically implanted into the rectum in mice, para-aortic lymph node metastasis could be visualized at laparotomy under a three-chip color cooled charged-coupled device camera. This article reviews recent highlights in this rapidly evolving field: cancer therapeutic and cancer diagnostic approaches using the telomerase-specific oncolytic adenoviruses.

Short telomeres and high telomerase activity in T-cell prolymphocytic leukemia

To test the role of telomere biology in T-cell prolymphocytic leukemia (T-PLL), a rare aggressive disease characterized by the expansion of a T-cell clone derived from immuno-competent post-thymic T-lymphocytes, we analyzed telomere length and telomerase activity in subsets of peripheral blood leukocytes from 11 newly diagnosed or relapsed patients with sporadic T-PLL. Telomere length values of the leukemic T cells (mean+/-s.d.: 1.53+/-0.65 kb) were all below the 1st percentile of telomere length values observed in T cells from healthy age-matched controls whereas telomere length of normal T- and B cells fell between the 1st and 99th percentile of the normal distribution. Leukemic T cells exhibited high levels of telomerase and were sensitive to the telomerase inhibitor BIBR1532 at doses that showed no effect on normal, unstimulated T cells. Targeting the short telomeres and telomerase activity in T-PLL seems an attractive strategy for the future treatment of this devastating disease.

Low- to high-throughput analysis of telomerase modulators with Telospot

We designed a method termed Telospot to discover and characterize telomerase modulators as anticancer drugs or chemical biology tools. Telospot is based on a highly efficient human telomerase expression system and the detection of telomerase DNA reaction products in macroarray format. Telospot offers a highly scalable, cost- and time-effective alternative to presently available telomerase assays, which are limited by the requirement for PCR, telomerase purification or technologies not amenable to high throughput.

Premature telomere shortening in polymorphonuclear neutrophils from patients with systemic lupus erythematosus is related to the lupus disease activity

We investigated whether premature telomeric loss occurred in peripheral polymorphonuclear neutrophils (PMN) as well as mononuclear cells (MNC) from patients with systemic lupus erythematosus (SLE). We measured the telomere length of MNC and PMN in 60 SLE patients and 26 sex-, race- and age-matched healthy volunteers by Southern blotting with chemiluminescence method. The possible predisposing factors associated with telomere change were also analysed. We found the telomere length of MNC and PMN shortened with age in different degrees in both SLE and control groups. Compared to the control group, the telomere length was shortened in both SLE-MNC (6.08 kb in SLE versus 6.71 kb in control, P = 0.0008) and PMN (6.24 kb in SLE versus 6.75 kb in control, P = 0.0025). The average reduction in telomere length in SLE patients was equivalent to a premature senescence of 16.5 years in MNC and 13.4 years in PMN. In addition, the accelerated telomere shortening was more prominent in SLE patients younger than 45 years old. SLE disease activity (SLEDAI) contributed remarkably to the accelerated telomere erosion, at least in PMN. Moreover, the telomere length of MNC was significantly shorter than PMN in the same SLE patients with leukopenia and lymphopenia. These data suggested that MNC and PMN from patients with SLE displayed premature and accelerated telomere shortening that SLE is an independent factor for it.

Differences in telomerase expression by the CD1a+ cells in Langerhans cell histiocytosis reflect the diverse clinical presentation of the disease

Langerhans cell histiocytosis (LCH) is a disease characterized by an uncontrolled clonal proliferation of Langerhans cells, whose aetiology is still unclear. The clonal nature of LCH could support the hypothesis that it is a neoplastic disease with unlimited growth potential. One requirement for unlimited proliferation is the maintenance of telomere length. In a group of 70 patients, we set out to investigate whether a telomere maintenance mechanism is indeed active in LCH cells. This work showed that LCH cells from all restricted skin LCH lesions (6/6) expressed telomerase as assessed by human telomere reverse transcriptase (hTERT) immunohistochemistry, whereas LCH cells from the majority of the bone lesions analysed did not express hTERT (26/34). Interestingly, in contrast to the solitary bone lesions, LCH cells from lesions of multi-system patients always expressed telomerase (11/11), regardless of the lesional site. In situ telomeric repeat amplification protocol (TRAP) assays performed on different lesional sites showed that this telomerase was active. In addition, the telomere length of LCH cells from a hTERT-positive skin multi-system lesion was long and homogeneous when compared to that in the LCH cells from hTERT-negative bone single-system LCH lesions, which was heterogeneous in length. No evidence for an alternative lengthening of telomeres mechanism was found in hTERT-negative lesions. The difference in telomerase expression and telomere length at the different lesional sites and in biopsies from patients with solitary versus multi-system disease appears to reflect the diverse clinical presentation and course of this disease. The results from this study have important implications for understanding the nature of this disease.

Nonradioactive detection of telomerase activity using the telomeric repeat amplification protocol

The telomeric repeat amplification protocol (TRAP) is a two-step process for analyzing telomerase activity in cell or tissue extracts. Recent modifications of this sensitive assay include elimination of radioactivity by using a fluorescently labeled primer instead of a radiolabeled primer. In addition, the TRAP assay has been modified for real-time, quantitative PCR analysis. Here, we describe cost-effective procedures for detection of telomerase activity using a fluorescent-based assay as well as by using real-time PCR. These modified TRAP assays can be accomplished within 4 h (from lysis of samples to analysis of telomerase products).

Clinical significance of telomerase activity in peritoneal lavage fluid from patients with gastric cancer and its relationship with cellular proliferation

AIM: To evaluate the efficacy of telomerase activity assay and peritoneal lavage cytology (PLC) examination in peritoneal lavage fluid for the prediction of peritoneal metastasis in gastric cancer patients, and to explore the relationship between telomerase activity and proliferating cell nuclear antigen expression.

METHODS: Telomeric repeated amplification protocol (TRAP)-enzyme-linked immunosorbent assay (ELISA) was performed to measure the telomerase activity in 60 patients with gastric cancer and 50 with peptic ulcer. PLC analysis of the 60 patients with gastric cancer was used for comparison. The proliferating cell nuclear antigen (PCNA) in gastric carcinoma was immunohistochemically examined.

RESULTS: The telomerase activity and PLC positive rate in peritoneal lavage fluid from patients with gastric cancer was 41.7% (25/60), and 25.0% (15/60), respectively. The positive rate of telomerase activity was significantly higher than that of PLC in the group of pT₄ (15/16 vs 9/16, P < 0.05), P_1-3 (13/13 vs 9/13, P < 0.05) and diffuse type (22/42 vs 13/42, P < 0.05). The patients with positive telomerase activity, peritoneal metastasis, and serosal invasion had significantly higher levels of average PCNA proliferation index (PI), (55.00 ± 6.59 vs 27.43 ± 7.72, 57.26 ± 10.18 vs 29.15 ± 8.31, and 49.82 ± 6.74 vs 24.65 ± 7.33, respectively, P < 0.05).

CONCLUSION: The TRAP assay for telomerase activity is a useful adjunct for cytologic method in the diagnosis of peritoneal micrometastasis and well related to higher proliferating activity of gastric cancer. The results of this study also suggest a promising future therapeutic strategy for treating peritoneal dissemination based on telomerase inhibition.