Telomeric Repeat Amplification Protocol Method Research Articles

Overexpression of Beclin1 gene leads to reduction of telomerase activity in MDCK cells and enhances apoptosis.

Telomeres through maintaining chromosomal integrity have key roles in the cell life span. The autophagy is typically a pro-survival process and important for maintaining cellular homeostasis. Conversely, in some conditions, autophagy acts as caspase-independent cell death program. Beclin1 gene plays a principal role in the initiation of autophagy. The aim of this study was to evaluate the effect of autophagy induction via recombinant Beclin1 on telomerase activity and programmed cell death (apoptosis) in MCDK cells. The recombinant Beclin1-pcDNA3.1(-) was transfected into MDCK cells. Next, the autophagy information was detected by LC3II staining as autophagy marker using flow cytometry. The telomerase activity was measured by telomeric repeat amplification protocol method in MDCK cells. To detection of the cell death in MDCK cells, apoptosis assay was done through Annexin V staining method. The results of flow cytometry analysis indicated that following overexpression of Beclin1 gene, the percentage of the LC3II was 16.08% compared with control group (0.48%). Following induction of autophagy, telomerase activity reduced 10 folds in comparison with the control group. The rate of apoptosis in transfected MDCK cells increased up to 12.74%. Crosstalk between telomerase, autophagy, and apoptosis may determine the fate of the cancer cell aging. Hence, manipulation of autophagy may create a novel area to design new compounds and combination therapy to shorten the cancer cell survival.

Telomerase stability and evaluation of real-time telomeric repeat amplification protocol

Telomerase is RNA directed polymerase which acts as reverse transcriptase based on its own RNA component. It is considered to be involved in the pathology of many diseases and is recognized as a potential biomarker. The aims were to determine the sample storage conditions and the time frame for samples analysis, then to prove reliability of enzyme activity measurement with real-time telomeric repeat amplification protocol (TRAP) and to evaluate the suitable standard samples for telomerase activity measurements. Samples used for stability and freeze-thaw study were peripheral blood leukocytes, obtained from apparently healthy persons, patients with diagnosed cancer and cell lines. Telomerase activity was measured using TRAP method, while standard evaluation was done using nuclear magnetic resonance (NMR) technique. Storage at −20 °C preserved telomerase activity in samples from cancer patients for at least 14 days (21.46 ± 0.135 versus 21.84 ± 0.357, p = .756), while samples obtained from healthy persons should be stored at −80 °C. We observed significant decrease of telomerase activity at freeze thaw cycle 5 in cancer patients’ samples (21.46 ± 0.135 versus 23.09 ± 0.316, p < .05), and in healthy persons’ ones already at cycle 3 (22.74 ± 0.107 versus 24.85 ± 0.151, p < .05). Telomerase activity from cell lines samples showed overall greater stability regarding the storage period and freeze-thaw cycles and it was considered for standard sample, which was confirmed by NMR analysis. Telomerase enzyme had adequate stability while efficacy, linearity, and reproducibility of TRAP method were acceptable for bio-analytical methods. All this indicated that telomerase could be a reliable biomarker.

Abstracts of the 17th International Symposium on Bioluminescence and Chemiluminescence ‐ (ISBC 2012)

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Telomerase activation in a model of lung adenocarcinoma

Ovine pulmonary adenocarcinoma (OPA) is a lung cancer strikingly similar to the pneumonic-type mixed invasive adenocarcinoma with a predominant bronchioloalveolar component in humans. Telomerase activity in OPA and the potential involvement of the kinase Akt in telomerase activation and regulation of cell proliferation were investigated. Lung tissues were collected from sheep with a histopathological diagnosis of OPA or controls. Epithelial cell cultures were derived in vitro from lung tissues. Telomerase activity was evaluated using the telomeric repeat amplification protocol method. Phosphorylation of Akt was detected by Western blotting. Telomerase activity was significantly higher in OPA lung tissues compared to control lung tissues. A high telomerase activity was detected in eight out of 12 (67%) primary cell cultures derived from tumours. A high level of expression of phosphorylated Akt was found in 10 out of 27 (37%) tumours, with abolition of Akt activation in response to epidermal growth factor stimulation demonstrated in primary cell cultures derived from tumours. Telomerase activation takes place in ovine pulmonary adenocarcinoma tumour cells and may be partly attributable to Akt activation. Telomerase may inhibit cellular senescence and contribute to the accumulation of tumour cells in mixed adenocarcinoma with a bronchioloalveolar component. Further work is necessary to identify alternative signalling pathways of telomerase activation in tumours.

Telomerase activity and cell proliferation index in cholesteatoma

Conclusions. Telomerase activity was expressed in cholesteatomas, and cellular proliferation was significantly higher in cases where the telomerase activity was positive. Telomerase activity was also closely related with cellular proliferation in chronic hyperproliferating tissues such as cholesteatomas. Objective. Telomerase activity is detected in most malignant tumors and is also known to have a close relationship with cell proliferation. Cholesteatoma shows cellular hyperproliferation. We studied telomerase activity in cholesteatoma and its relationship with cellular proliferation and clinical findings. Material and methods. Cholesteatoma tissue was obtained from 40 patients during middle ear surgery. Telomerase activity was measured using a telomeric repeat amplification protocol method. As a cellular proliferation index, expression of Ki-67 was measured by means of immunohistochemical staining. Posterior auricular skin was used as a control. Telomerase activity was compared with Ki-67 expression. Clinical features such as hearing loss, the extension of cholesteatoma, the degree of bone destruction and the cause of cholesteatomas were compared with telomerase activity and the cellular proliferation index. Results. Telomerase activity was positive in 21/40 cholesteatomas (52.5%), but absent in the control group. The average Ki-67 labeling index in the cholesteatoma group was 32.84±10.13, higher than that in the control group (21.83±7.76) (p<0.05). The average Ki-67 labeling indices of the 21 telomerase activity-positive and 19 telomerase activity-negative cholesteatomas were 37.76±8.53 and 27.39±9.06, respectively. The Ki-67 labeling index was significantly higher in telomerase-positive cholesteatomas (p<0.05). The clinical features did not show a relationship with either telomerase activity or the cellular proliferation index.

Telomerase, P53 and PCNA activity in osteosarcoma

Aims: The aim of this study was to investigate telomerase activity and to assess the correlation between telomerase activity, tumor proliferative activity and p53 overexpression in osteosarcoma tumor samples. Methods: Using a telomerase polymerase chain reaction-enzyme-linked immunoassay based on the telomeric repeat amplification protocol method, we examined telomerase activity in 26 primary osteosarcoma specimens. P53 overexpression was identified using immunohistochemical staining, and tumor proliferative activity was assessed by immunohistochemical staining of PCNA. Results: Telomerase activity was detected at a relatively low level in five of 26 osteosarcoma tissue specimens. P53 was detected in eight of 21 cases. There was no significant correlation between telomerase activity and p53 overexpression ( p=0.325). There was a significant correlation between PCNA staining and telomerase activity ( p=0.0075). Conclusion: Difference between the telomerase activity and p53 overexpression in osteosarcoma suggests that p53 and telomerase may not cooperate in tumor proliferation. Correlation of telomerase activity to PCNA expression suggests that telomerase activity may also useful for evaluate proliferative activity in osteosarcoma.

Telomerase activity and hTERT mRNA in development and progression of adenoma to colorectal cancer

Telomerase activity and hTERT mRNA expression are upregulated in colorectal cancer. Whether they are inherent in colorectal adenomas, premalignant lesions to cancer, however, remains to be elucidated. We examined telomerase activity by the fluorescence-based telomeric repeat amplification protocol method and analyzed the level of hTERT mRNA by real-time polymerase chain reaction in 74 surgically obtained neoplasms from 29 patients. The specimens were divided into 6 categories according to the criteria of the Vienna Classification. The control comprising 29 non-pathological mucosa were classified into category 1, 6 adenomas indefinite for neoplasia into category 2, 21 non-invasive low grade adenomas into category 3, 23 high grade adenomas or non-invasive carcinomas into category 4, and 15 intramucosal or submucosal carcinomas into category 5. Carcinoma invading beyond the submucosa (9 samples) was referentially subdivided into category 6. Telomerase activity (mean +/- standard error) in 1 categories to 6 were 5.0+/-1.2, 1.8+/-1.7, 4.3+/-1.6, 20.2+/-2.1, 36.4+/-5.5, and 55.5+/-8.2 units/microg protein, respectively. There were no statistical differences between categories 1 and 2, 1 and 3, and 2 and 3. A significant statistical difference in the other two was observed by the multiple comparison test. The mean levels of hTERT mRNA was 103.1+/-102.4, 103.6+/-103.0, 103.6+/-102.9, 103.7+/-102.9, 104.0+/-103.4, and 104.4+/-104.0 copies/microg total RNA, respectively. There was a significant statistical difference only between category 6 and each of the other categories. These results suggest that telomerase activation occurs during the progression from low-grade to high-grade dysplasia in adenomas and increases steadily with the progression of the degree of dysplasia and invasion during colorectal carcinogenesis, and that hTERT mRNA expression is a feature of the late stage development of colorectal cancer.

New attempt of preoperative differential diagnosis of thyroid neoplasms by telomerase activity measurement

Telomerase activity (TA) has been shown highly expressed in various solid malignant neoplasms, but only rarely in benign tumor or normal tissues. Most reports examined TA by the qualitative method, telomeric repeat amplification protocol (TRAP) assay. We examined TA in tissues of thyroid neoplasm by quantitative method to establish whether TA was a useful marker for preoperative differential diagnosis of thyroid tumors. TA was measured by the quantitative method, TRAP assay, fluorescence based TRAP method in 32 frozen tissues of thyroid tumors (17 malignant, 15 benign). Cut-off values in TA were 0 unit and 9 units from mean +/- 2SD of TA in benign thyroid tumors. Mean (SD) TA levels in benign thyroid tumors and thyroid carcinomas were 2.06 (3.58) units and 30.5 (38.2), respectively. Mean TA of carcinomas was significantly higher than that of benign disease in thyroid tumors (p=0.0092). The sensitivity of the malignancy was 64.7% (cut-off <0) (p=0.162), 52.9% (cut-off <9) (p=0.0048). TA in thyroid carcinoma was significantly correlated with UICC stage (p=0.029), and slightly correlated with tumor size, pN and M. Positive rate of TA in microfollicular adenoma was slightly higher than that in macrofollicular adenoma. Conclusively, quantitative TA might be a useful marker for differential diagnosis between benign and malignant thyroid tumors.

Real-Time Quantitative Telomeric Repeat Amplification Protocol Assay for the Detection of Telomerase Activity2

Telomerase is a ribonucleoprotein enzyme associated with immortalization and transformation of human cells. The telomeric repeat amplification protocol (TRAP) is widely used for the detection of telomerase activity. The TRAP method, although highly sensitive and specific because it includes PCR amplification, is laborious and does not provide precise quantitative information. We developed a real-time quantitative TRAP (RTQ-TRAP) system by combining a real-time PCR technique with the conventional TRAP method. Telomerase activity in human tumor cell lines and in 13 lymphoma samples was measured using the RTQ-TRAP assay, and the results obtained from the samples using the RTQ-TRAP method were compared with the conventional TRAP method. The RTQ-TRAP method was both accurate and reproducible in measuring telomerase activity in a dilution series of protein extracts from HL60 cells. Telomerase activity in 13 lymphoma samples, as determined by the RTQ-TRAP method, was ninefold lower than that measured by the conventional TRAP method. The half-life of telomerase activity in human tumor cells, as determined using RTQ-TRAP, was much shorter than the half-life reported previously. Our results suggest that the conventional TRAP assay frequently overestimates telomerase activity in tumor samples. The RTQ-TRAP method is thus a useful tool to rapidly and precisely quantify telomerase activity.

Increased telomerase activity and elevated hTERT mRNA expression during multistage carcinogenesis of squamous cell carcinoma of the lung.

Telomerase activation is believed to play a critical role in the immortalization of cells and carcinogenesis. Telomerase activity is undetectable in normal somatic cells (except for those cells undergoing proliferation) but is expressed in the majority of human tumors including lung carcinoma. The expression of hTERT mRNA has been found to be correlated with telomerase activity. In the current study, the authors analyzed telomerase activity and hTERT mRNA expression in preinvasive bronchial lesions using biopsy specimens obtained by fluorescence bronchoscopy. The authors studied 150 bronchial biopsy specimens obtained by fluorescence bronchoscopy. The intensity of telomerase activity was determined by the fluorescence-based telomeric repeat amplification protocol method in 74 bronchial biopsy specimens (22 normal bronchial epithelium or bronchitis cases, 15 squamous metaplasia cases, 23 dysplasia cases, and 14 squamous cell carcinoma cases), and the level of hTERT mRNA was analyzed in another 76 specimens (24 normal bronchial epithelium or bronchitis cases, 15 squamous metaplasia cases, 20 dysplasia cases, and 17 squamous cell carcinoma cases) by real-time polymerase chain reaction. The mean values (+/- the standard deviation [SD]) of telomerase activity in normal bronchial epithelium or bronchitis, squamous metaplasia, dysplasia, and squamous cell carcinoma cases were 6.2 +/- 7.5, 13.9 +/- 14.8, 18.5 +/- 20.8, and 54.5 +/- 22.3 U/microg protein, respectively. The upper limit of telomerase activity in normal bronchial epithelium or bronchitis was 21 U/microg protein (mean + 2SD). It is interesting to note that, 5 of 15 squamous metaplasia biopsies (33%), 8 of 23 dysplasia biopsies (35%), and all squamous cell carcinoma biopsies (100%) exhibited levels of telomerase activity that were > 21 U/microg protein. The mean levels of hTERT mRNA in normal bronchial epithelium or bronchitis, squamous metaplasia, dysplasia, and squamous cell carcinoma cases were 891 +/- 840, 1936 +/- 1704, 3019 +/- 2607, and 12965 +/- 18008 copies/microg total RNA, respectively. Telomerase activity and hTERT mRNA expression were found to increase in proportion to the severity of histologic change from normal bronchial epithelium or bronchitis to squamous cell carcinoma. These results suggest that an increase in telomerase activity and hTERT mRNA expression are features of the early stages of the development of squamous cell carcinoma of the lung, with strong telomerase activity and hTERT mRNA expression being prominent during the latter stages.

Evaluation of telomerase activity in cutaneous melanocytic proliferations

Telomerase is an enzyme which synthesizes the telomeres, TTAGGG repeats at the end of vertebrate chromosomes. Its activity is suppressed in the majority of somatic cells, whereas it is detectable in most tumor cell lines and human cancers. Telomerase activity has been evaluated in many tumors for diagnostic purposes, and an increase thereof has been found with tumor progression. In our study we used a nonisotopic polymerase chain reaction (PCR)-based TRAP (telomeric repeat amplification protocol) method to quantify the level of telomerase activity in a series of cutaneous melanocytic lesions. Thirty-three benign nevi, 8 dysplastic nevi, 38 malignant melanomas, and 4 melanoma metastases were analyzed. Mean relative telomerase activity was low in benign nevi (3.5 ± 2.9), and significantly increased in dysplastic nevi (13.1 ± 6.8), malignant melanomas (49.8 ± 29.6), and metastases (121.2 ± 11.2). In addition to the evaluation of telomerase activity as a possible diagnostic tool, its increase with tumor progression also suggest a prognostic role in cutaneous melanoma. H UM P ATHOL 31:1018-1021.

Limitations on the quantitative determination of telomerase activity by the electrophoretic and ELISA based TRAP assays

Telomerase is a promising new tumor marker and can be detected using the TRAP (Telomeric Repeat Amplification Protocol) method. To address factors affecting its quantitative determination, we evaluated two commercial TRAP assays, an electrophoretic and an ELISA assay formats, using cultured cells and human tumor samples. We found that both TRAP assays had a limited linearity from 250 to 5000 tumor cells, with a similar intra-assay variation. The quantification of TRAP products was affected by high cell number in sample, the presence of non-tumor cells, and interfering substances in patient specimens. Because both assays have different limitations, determination of telomerase by a combined use of the two may provide more accurate information on the telomerase activity in a specimen. Extracts of specimens should also be tested at several concentrations to insure that the result is not being falsely decreased by an inhibitor. The quantitative results for telomerase activity by the TRAP assays, however, should be interpreted cautiously.

Telomerase Activity and Prognosis in Primary Breast Cancers

Recent studies associate telomerase activity with prognostic factors and survival. We compared quantitative telomerase activity in primary tumors with traditional prognostic factors and outcome in a group of invasive but nonmetastatic breast cancers. Telomerase activity was measured in 203 invasive breast cancers by the quantitative telomeric repeat amplification protocol method. Telomerase expression was compared with 28S rRNA level, tumor content, and clinical variables, including outcome. For clinical correlations, telomerase activity was standardized by two methods: (1) a correction for cellularity using 28S rRNA levels, and (2) a correction for the histologically determined invasive proportion of the specimen. Telomerase activity was found in 82% of breast cancers with measurable 28S rRNA levels. Telomerase activity was associated with the proliferative index (P <.01) of the tumor but not with any other prognostic variable. Neither uncorrected nor corrected telomerase activity was associated with relapse-free or overall survival in this study. Telomerase activity level was associated with the proliferative index of invasive breast cancers, but its measurement in samples from this group of nonmetastatic breast cancer patients did not predict survival.

Telomerase activity and telomere length in lymphocytes from patients with cutaneous T‐cell lymphoma

Telomeres shorten with successive cell divisions in normal somatic cells. Telomerase is a ribonucleoprotein enzyme associated with cellular proliferation and plays an important role in maintaining the stability of chromosomes and the length of DNA telomeres. Telomerase activity has been detected in tissues from many human tumors, but is not present in the majority of normal tissues. Thus, measurement of telomerase activity and telomere length may contribute to understanding the mechanism of tumorigenesis and provide useful diagnostic or prognostic information. The aim of this study was to investigate the telomerase activity and telomere length from patients with cutaneous T-cell lymphoma (CTCL). Eighteen skin-homing T-cell lines were established from skin biopsies and 10 peripheral blood mononuclear cells (PBMC) were isolated from patients with various stages of CTCL together with 22 PBMC from healthy donors. For each sample an identical amount of cellular protein was measured quantitatively for telomerase activity using the telomerase polymerase chain reaction-enzyme-linked immunosorbent assay based on the telomeric repeat amplification protocol method. Telomere length was assayed using a commercial kit. Eight of ten PBMC and 16 of 18 skin-homing T-cell lines from patients with CTCL showed moderate to strong telomerase activity. Freshly obtained PBMC from healthy donors showed weak levels of telomerase activity. A shorter telomere length was found in cell lines and PBMC from patients with CTCL compared with healthy controls. Four skin-homing T-cell lines going into growth crisis showed sharply reduced telomerase activity. The results of the current study indicate that both skin-homing T-cells and PBMC from CTCL have high telomerase activity and short telomere length. These changes are similar to the changes observed in the majority of malignant cells including other types of T-cell lymphoma. It is interesting to note that even in the very early stages of CTCL such as parapsoriasis (which is a clinically benign disease) the changes already are present, indicating that a significantly high level of telomerase activity frequently occurs in CTCL and may be an important event in tumorigenesis. Telomerase activity and telomere length are useful markers for CTCL risk assessment.

TELOMERASE ACTIVITY AND TELOMERES IN PERIPHERAL BLOOD MONONUCLEAR CELLS FROM PATIENTS WITH ATL AND HAM/TSP

P134 Telomeres and telomerase are known to be important in chromosome function and cell proliferation. We investigated the effect of infection of HTLV-I on telomerase activity, telomere length and human telomerase RNA (hTR) of the peripheral blood mononuclear cells from donors infected with HTLV-I. Ten patients with ATL and 10 patients with HAM/TSP were examined. As controls, 11 asymptomatic controls were examined; 6 of these were infected with HTLV-I and the other 5 were not. The telomerase activity was assayed by a non-radioisotope quantitative system from a telomeric repeat amplification protocol (TRAP), and it was detected using a fluorescence-based TRAP method. We measured the telomere length as the terminal restriction fragment length. The amount of hTR was measured using the real-time PCR system. The telomerase activity was significantly increased in the samples from patients with acute type of ATL (n=4, mean ± SEM 206.24 ± 22.44 units/μg) compared with asymptomatic controls (11.29 ± 2.60) (p<0.01). It was also slightly increased in the other types of ATL (n=6, 29.06 ± 9.09) (p<0.05), but not in HAM/TSP (13.32 ± 3.49). Both telomere length and the amount of hTR showed no specific association with the type of diseases, although the decrease of telomere length was observed with aging (p<0.05). Infections with HTLV-I themselves cause no significant effect on the telomerase activity and telomere length, although telomerase may play an important role in the process of tumorigenesis of some types of ATL.