• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.4
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• pp.289-300
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• 2001

Telomerase is a ribonucleoprotein that synthesizes telomere repeats. It has been reported that activation of telomerase was associtated with immortalization, proliferative activity and carcinogenesis. Recently, telomerase activity has been extensively studied in many kinds of malignant tumors for clinical diagnostic and/or prognostic utilities. In neuroblastoma, breast carcinoma, gastric carcinoma, non-small cell lung carcinoma, close relationship has been reported between high telomerase activity and lymph node metastasis, tumor aggressiveness and poor prognosis. The purpose of this study is to investigate the clinical implication of telomerase activity assay as an adjunctive factor in decision-making on neck node management, speedy pre-operative judging on histologic malignancy grading. Thus we performed semi-quantitative assay of telomerase activity using Telomerase PCR ELISA $kit^{(R)}$(Boeringer Manheim, Germany) and evaluated correlation between telomerase activity and tumor size, neck node metastasis, Anneroth malignancy score and influence of pre-operative chemotherapy on its activity in 27 cases of oral squamous cell carcinomas and 18 cases of normal oral epithelium. Also, correlation between telomerase activities and PCNA indices was evaluated. The results were obtained as follows: 1. The telomerase activities were detected in 24 specimens out of 27 oral squamous cell carcinoma specimens (88.9%) and in 5 specimens out of 18 normal oral epithelium specimens (27.8%). The mean value of telomerase activities was $0.9793{\pm}0.3428$ in 24 oral squamous cell carcinoma specimens and $0.4855{\pm}0.1117$ in 5 normal oral epithelium specimens. The positivity rate and mean value of telomerase activities in oral squamous cell carcinoma specimens were significantly higher than those of normal oral epithelium specimens (p<0.05). 2. There was no significant correlation between total Anneroth malignancy score and telomerase activity (p>0.05), but points of mitosis index and depth of invasion were significantly correlated with telomerase activities (p<0.05). 3. The positive immunohistochemical staining for PCNA(proliferating cell nuclear antigen) was observed in 26 specimens out of 27 oral squamous cell carcinoma specimens and mean value of PCNA indices of 26 specimens was $53.67{\pm}26.46$. PCNA indices were significantly correlated with telomerase activities (p<0.05). 4. The mean value of telomerase activities was significantly higher in pathologic T3/T4 group than in T1/T2 group (p<0.01). There was no significant difference of mean value of telomerase activities between pathologic neck node positive group and negative group (p> 0.05). Pre-operative chemotherapy significantly lowered the telomerase activities (p<0.05). The above results suggested telomerase activity could be used as diagnostic marker and adjunctive parameter for judging on histologic malignancy in oral squamous cell carcinoma.

• Environmental Mutagens and Carcinogens
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• v.25 no.2
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• pp.66-70
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• 2005

Telomerase, a specialized RNA-directed DNA polymerase that extends telomeres of eukaryotic chromosomes, has activity in most malignant tumors and provides a mechanism for the unlimited potential for division of neoplastic cells. Although telomerase is known to be a regulated enzyme, the factors and mechanisms involved in telomerase regulation are not well understood. In the present study, we compared the effect of 12-O­tetradecanoyl-phorbol-13-acetate (TPA) and non-phorbol ester tumor promoters such as okadaic acid, anthralin and benzoyl peroxide on the expression of telomerase in the mouse skin carcinogenesis system, a well characterized model for studying pre-malignant and malignant progression. We found that most early papillomas harvested after 10 weeks of TPA promotion showed telomerase activity. Other papillomas harvested after 10 weeks of okadaic acid, anthralin and benzoyl peroxide promotion and after single treatment of DMBA only also showed telomerase activity, respectively. On the other hand, normal and all skins surrounded by papillomas harvested after 10 weeks of these promoters has no telomerase activity. Taken together these results, there appears to be no clear association between the level of telomerase activity and protein phosphorylation in mouse skin papillomas and telomerase may be useful as bio-markers in early detection of tumors.

• IMMUNE NETWORK
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• v.4 no.3
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• pp.166-175
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• 2004

Background: Telomerase, a ribonucleoprotein enzyme capable of synthesizing telomeric repeats, attracts attention for its possible role in determining the replicative capacity of normal somatic cells, transformed cells, and cells of the germline lineage. Differently from normal somatic cells with no telomerase activity, normal lymphocytes has been reported to have telomerase activity comparable to that found in transformed cells during development and activation, which substantiate a role in supporting the capacity of lymphocytes for extensive clonal expansion. Methods: Here, in order to define the telomerase regulation in murine T lymphocytes, telomerase activity in cloned murine $CD8^+$ T cells and naive $CD8^+$ T cells isolated from C57BL/6 mice was examined. Next, the regulatory mechanism of telomerase activity at transcriptional and post- translational levels was investigated by determining the expression level of the TERT protein, a key component for telomerase activity. Results: It was demonstrated that telomerase activity was expressed in an inactivated state as well as in an activated state in the murine $CD8^+$ T lymphocytes by using TRAP assay. The increase of telomerase activity was partially dependent on the net increase of TERT expression. Also, telomerase activity was decreased after treatment with protein kinase inhibitors, indicating that telomerase activation was prevented by inhibition of phosphorylation. Conclusion: Therefore, these results suggest that telomerase activity is constitutively expressed in the murine resting T lymphocytes and controlled by both transcriptional regulation and post- ranslational modifications.

• Proceedings of the Korea Society of Poultry Science Conference
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• 2004.11a
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• pp.16-18
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• 2004

This study was carried out to analyze the amount of telomeres and telomerase activity of several chicken cells. Telomere quantity and telomerase activity were analyzed during organ development, growth and aging in embryonic and adults chicken. Analyzed cells were whole embryos and the cells from brain, heart, liver, kidney, lymphocytes and germinal tissues in Korean Native Chicken. The amount of telomeric DNA was analyzed by quantitative fluorescence in situ hybridization (Q-FISH) techniques using a chicken telomere repeat probe. Telomerase activity was performed by Telomeric Repeat Amplification Protocol (TRAP) assay. In results, telomerase activity was highly detectable in early embryonic cells, germinal cells and kidney cells. Whereas the cells from brain, heart, and liver had gradually down-regulated pattern of telomerase activity. Analyzing the telomere quantities on chicken cells, the amount of telomeric DNA of most chicken cells gradually decreased as growth. From these results, the amount of telomeric DNA was directly affected by telomerase activity. Consequently the telomere quantity and telomerase activity are closely relate to cell differentiation and tissue specificity during developmental and growing stages.

• Korean Journal of Head & Neck Oncology
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• v.14 no.2
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• pp.199-205
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• 1998

Objective: Telomerase, a specialized ribonucleoprotein polymerase associated with cellular immortality, is expressed by most malignant cells and is inactive in most normal somatic cells. The assays of telomerase activity in various tumors have provided both diagnostic and prognostic information. This study was carried out to determine whether telomerase activity could be useful in distinguishing benign and malignant thyroid diseasees. Materials & Methods: Telomerase activity was determined using Oncor $TRAP_{EZE}^{TM}ELISA$ Telomerase Detection Kit for performing PCR-based telomeric repeat amplification protocol (TRAP) assay followed by ELISA detection in both normal and tumor tissues of 23 adenomatous hyperplasias, 12 follicular adenomas, 4 follicular carcinomas, 16 papillary carcinomas, 4 Hashimoto's thyroiditises and 3 malignant lymphomas. We also examined all cases microscopically to review the status of lymphoid infiltrate. Results: Of the 62 cases, extensive lymphoid infiltrates were contained in 20 tumor tissues(4 Hashimoto's thyroiditises, 3 malignant lymphomas, 6 adenomatous hyperplasias and 7 papillary carcinomas), all of which showed positive telomerase activity. All the normal tissues without lymphoid infiltrates(n=43) did not express telomerase activity. Of 42 tumor tissues without lymphoid infiltrates, 37(88.0%) showed positive telomerase activity: 13 of 17 adenomatous hyperplasias(76.5%), 11 of 12 follicular adenomas(91.7%), 4 of 4 follicular carcinomas(100.0%) and 9 of 9 papillary carcinomas(100.0%). Conclusions: Our methods showed high sensitivity in the detection of telomerase activity and the exclusion of lymphoid infiltrates may be important in telomerase assay. In our work, the measurement of telomerase activity was not useful in distinguishing benign and malignant thyroid diseases.

• Journal of Korean Neurosurgical Society
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• v.30 no.2
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• pp.137-143
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• 2001

Objective : Telomerase, a ribonucleoprotein adds telomere repeats to the ends of telomeres to compensate for the progressive loss. A favorable prognosis associated with low or no telomerase activity in some tumors, and cells transfected with antisense human telomerase lost telomeric repeats and die. We studied about the relationship between telomerase activity and apoptosis in the human brain tumors. Material and Methods : Between July 1998 and December 1999, 62 patients with brain tumors underwent surgery and their surgical specimens were obtained. Telomerase activity was investigated by telomeric repeats amplification protocol(TRAP) assay. Apoptosis was also evaluated by DNA fragmentation analysis. Differences and correlation in data were analyzed using Mann-Whitney test and Wilcoxon-signed rank test. Results : Expression rate of telomerase activity and apoptosis were 80% and 30% in malignant gliomas, 33% and 0% in low grade gliomas, 63% and 38% in meningiomas, 67% and 33% in pituitary adenomas, 33% and 33% in metastatic tumors, 67% and 17% in acoustic neurinomas, 100% and 100% in pineoblastomas, 100% and 0% in the hemangioblastoma, respectively. There was no significant difference of telomerase activity and apoptosis between histological types. But a significant difference was noted in the expression of telomerase activity between malignant gliomas and low grade gliomas(p = 0.022). Brain tumors with telomerase activity expressed the lower rate of apoptosis. A significant correlation was also found between telomerase activity and absence of apoptosis in the human brain tumors(p = 0.005). Conclusions : Our data suggests that telomerase may protect from apoptosis of the human brain tumors and also may play an important role in the biological malignancy of the gliomas.

• Molecules and Cells
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• v.19 no.3
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• pp.303-309
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• 2005

The end of eukaryotic genomic DNA is capped by a specialized structure called as "telomere" which consists of the repetitive array of nucleotide sequence, TTAGGG, in humans and mice, and a variety of binding proteins. Telomerase is a ribonucleoprotein (RNP) complex responsible for the elongation of telomeres to maintain the genomic integrity, and is composed of telomerase reverse transcriptase (TERT), telomerase RNA component (TERC), and their associated factors regulating the catalytic activity of telomerase. Although it is now apparent that telomerase protects cells from apoptosis via the maintenance of genomic integrity by stabilizing telomeres, our understanding for the physiological role of telomerase is yet far from completion, and emerging evidence suggests that telomerase has additional extratelomeric roles in mediating cell survival and anti-apoptotic functions against various cytotoxic stresses. Here we summarize and discuss how telomerase and telomeres are involved in mediating cellular protection against apoptosis.

• Tuberculosis and Respiratory Diseases
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• v.46 no.2
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• pp.195-203
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• 1999

Background: Telomerase enzyme activity is not detected in most normal cells, a phonomenon believed to be associated with limitations on cellular proliferation. Since this activity is detected in nearly all human tumor, including lung cancers, it has been suggested that telomerase activation may be coupled to acquisition of malignant phenotype. In this study, we determined whether telomerase activity was associated with tumor pathologic stage. Methods: Primary tumor specimens obtained by bronchoscopic biopsies from 33 patients were analyzed. Telomerase activity was measured by means of a modified Telomeric Repeat Amplication Protocol(TRAP) assay. Results: Telomerase activity was detected in 23 of the 27 non-small-cell lung cancer and 5 of 6 small-cell lung cancer. A few primary tumors did not appear to have detectable telomerase activity. Positive associations were found between the telomerase-positive rate and tumor stage(p<0.05). Conclusion: High telomerase activity is detected frequently in primary lung cancers that exhibit high tumor cell proliferation rates and advanced pathologic stage.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.89-95
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• 2002

Telomerase is a ribonucleoprotein complex, whose function is to add telomeric repeats $(TTAGGG)_n$ to chromosomal ends and is also known to play an important role in cellular immortalization. Telomerase is highly active in most tumor cells, yet not in normal cells. Therefore, it may have possible applications in cancer gene therapy. Telomerase consists of two essential components; a telomerase RNA template (hTR) and a catalytic subunit (hTERT). The current study attempted to inhibit the "open" part of the human telomerase RNA (hTR) with an antisense sequence-expressing adenovirus. It was found that the antisense telomerase adenovirus suppressed the telomerase activity, tumor cell growth, and survival in vitro. Furthermore, FACS analysis and TUNEL assay suggested that the reduce viability was mediated through the induction of apoptosis, indicating that this approach might be a useful method for suppressing cancer growth in targeted cancer gene therapy.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.12
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• pp.4919-4923
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• 2014

Background: To investigate the effect of celecoxib on telomerase activity and apoptosis in a human laryngeal squamous carcinoma cell line (Hep-2 cells). Materials and Methods: The growth inhibition rate of Hep-2 cells in vitro was measured by MTT assay, and apoptosis by TUNEL assay and flow cytometry (FCM). The TRAP-ELISA method was used to determine telomerase activity in Hep-2 cells. The mRNA expression of human telomerase RNA component(hTR), human telomerase reverse transcriptase (hTERT) and human telomerase-associated protein(hTEP1) was determined by RT-PCR assay. Expression of Bax and Bcl-2 proteins was assessed by Western blotting. Results: Celecoxib can inhibit proliferation and induce apoptosis in a dose- and time-dependent manner, repress telomerase activity, decrease hTERT mRNA and Bcl-2 protein expression and increase Bax protein expression, PGE2 had no effect on telomerase. Conclusions: Celecoxib had the antiproliferative and pro-apoptotic effect in Hep-2 cells. Apoptosis was accompanied by a decrease in telomerase activity which was directly correlated with hTERT mRNA and up-regulation of Bax/Bcl-2. Bcl-2 may thus play an important role in telomerase activity as well as apoptosis.