Cancer Research and Treatment

Effective Inhibition of Cancer Cell Growth by a Novel Tripartite Transfection Complex Containing Ribbon Antisense Molecules to hTR: Jong-Gu Park; Cancer Res Treat. 2004;36(5):308-314. Published online October 31, 2004; DOI: https://doi.org/10.4143/crt.2004.36.5.308

Abstract PDF PubReader ePub: Purpose
In the present study, ribbon antisense to the hTR RNA, a component of the telomerase complex, was employed to inhibit telomerase activity and cancer cell growth.
Materials and Methods
Ribbon antisense molecules to the human hTR gene (hTR-RiAS) were constructed and complexed with a short modified peptide and cationic liposomes to improve the cellular uptake of the antisense molecules. The DPL complexes containing hTR-RiAS were transfected into target cancer cells. Various assays were performed to confirm the effects of the hTR-RiAS on the gene expression and cell proliferation.
Results
When cancer cells were treated with hTR-RiAS, the cellular level of hTR mRNA was reduced by more than 95%, as shown by RT-PCR. Further, the telomerase acti vity was also affected by the antisense treatment. In contrast, both mismatched and scrambled oligonucleotides failed to reduce the levels of hTR mRNA and telomerase activity. When checked for cancer cell viability, hTR-RiAS inhibited cell growth by more than 70%, in a very rapid manner. The reduced cell viability was found to be due to apoptosis of cancer cells.
Conclusion
These results show that hTR-RiAS is a powerful anticancer reagent, with the potential for broad efficacy to diverse malignant tumors.

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Telomerase Activity in Gastric Adenocarcinomas: Frozen Tissues Versus Methacarn-fixed Paraffin-embedded Tissues: Jinyoung Yoo, Seok Jin Kang, Chang Suk Kang; Cancer Res Treat. 2003;35(6):478-482. Published online December 31, 2003; DOI: https://doi.org/10.4143/crt.2003.35.6.478

Abstract PDF: PURPOSE
Telomerase is an RNA-dependent DNA polymerase that synthesizes TTAGGG telomeric DNA onto chromosome ends to compensate for sequence loss during DNA replication. It has been detected in 85~90% of all primary human cancers, implicating that its apparent reactivation in tumors may play a role in the tumorigenic process. The purpose of this study was to evaluate telomerase activity in stomach cancer, and to determine whether methacarn-fixed paraffin-embedded tissues can replace frozen tissue sections for the telomerase (TRAP) assay. MATERIALS AND METHODS: Frozen and corresponding methacarn-fixed paraffin-embedded tissue samples were obtained from 51 patients with gastric adenocarcinoma and analyzed for telomerase activity by using a TRAPeze ELISA kit. RESULTS: Telomerase activity was detected in 37 (73%) frozen samples, and in 13 (25%) methacarn-fixed paraffin blocks. Telomerase activity was well correlated with depth of invasion (p=.037) and tumor differentiation (p=.022). CONCLUSION: These data suggest that reactivated telomerase may play a significant role in the tumorigenesis of gastric cancer and may reflect the malignant potential of the tumor. It is noteworthy that methacarn- fixed tissue cannot as yet substitute for the frozen tissue in the TRAP assay.

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Changes of Telomerase Activity and Proliferation by Inhibition of Reverse Transcriptase Activity in Human Cancer Cell: Hyun Jung Ji, Kyu Hyun Park, Tae Soo Kim, Sun Young Rha, Nae Choon Yoo, Jun Myung Kim, Jun Suk Kim, Jae Kyoung Roh, Woo Ick Jang, Hyun Cheol Chung; Cancer Res Treat. 2002;34(3):223-233. Published online June 30, 2002; DOI: https://doi.org/10.4143/crt.2002.34.3.223

PURPOSE
Activation of telomerase is proposed to be an essential step in cancer cell immortalization and cancer progression. 3'-azido-2',3'-dideoxythymidine (AZT), a reverse transcriptase inhibitor, was reported to be incorporated in telomeric sequences of immortalized cells in culture and to suppress the activity of telomerase and the cell proliferation. In this study, after induction of cancer cell senescence with long-term treatment of AZT, we investigated the dynamics of telomerase subunits (hTERT, hTR, TEP), transcription factors (c-Myc, Mad1), telomerase activity, and finally, telomere length in a human breast cancer cell line. MATERIALS AND METGODS: Human breast cancer cell (MDA-MB-231) was treated with AZT. Senescence was measured by senescence-associated beta-gal staining and apoptosis was counted by dTd enzyme assay. Telomerase activity (by TRAP assay), expression of telomerase subunit genes (by RT-PCR and real-time PCR) and telomere length (by Southern blot analysis) were measured after the AZT treatment.
RESULTS
We found evidences of senescence, apoptosis and growth delay after AZT treatment. In addition, AZT- treated cancer cells showed inhibition of telomerase activity and shortening of telomere length in a dose- and duration-dependent way. Among the telomerase subunits, hTERT and c-Myc were the first factors to change after AZT treatment, subsequently, followed by the changes of hTR, Mad1 and TEP.
CONCLUSION
The suppression of hTERT and c-Myc by AZT treatment was the initial genetic phenomenon, subsequently followed by the changes of hTR, Mad1 and TEP.

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Regulation of cellular senescence in tumor progression and therapeutic targeting: mechanisms and pathways
Bowei Liu, Zhigang Peng, Hao Zhang, Nan Zhang, Zaoqu Liu, Zhiwei Xia, Shaorong Huang, Peng Luo, Quan Cheng
Molecular Cancer.2025;[Epub] CrossRef

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Telomerase Activity and Expression of hTR and TERT in Human Soft Tissue Sarcomas: Jinyoung Yoo, Seok Jin Kang, Byung Kee Kim; Cancer Res Treat. 2002;34(1):46-51. Published online February 28, 2002; DOI: https://doi.org/10.4143/crt.2002.34.1.46

Abstract PDF

PURPOSE
Sarcomas have rarely been analyzed for telomerase, which is an RNA-dependent DNA polymerase to maintain telomeres and prevent telomere shortening. This study was undertaken to determine telomerase activity and the expression of the telomerase subunits human telomerase RNA (hTR) and telomerase reverse transcriptase (TERT) in soft tissue sarcomas.
MATERIALS AND METHODS
Twenty three sarcomas were analyzed for the telomerase activity by a radioactive PCR-based TRAP assay. All of the samples were further investigated for the expression of hTR by in situ hybridization and for TERT and p53 by immunohistochemistry.
RESULTS
Telomerase activity was detected in four (17%) samples. Expression of hTR was demonstrated in 11 (48%) cases, whereas TERT was expressed in 20 (87%).Of the four telomerase-positive tumors, three were positive for both hTR and TERT, and one was positive only for TERT. p53 overexpression was observed in nine (39%) tumors. The frequency of p53 expression increased as the tumor grade advanced (p= .064).
CONCLUSION
These data indicate that the reactivation of telomerase is an uncommon event in human soft tissue sarcomas. The high frequency of the expression of hTR and TERT in these tumors suggests that telomerase activity may be regulated at the transcriptional level and an additional event leading to telomerase activation exist.

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Concomitant underexpression of TGFBR2 and overexpression of hTERT are associated with poor prognosis in cervical cancer
Hui Yang, Hongyan Zhang, Yahua Zhong, Qiaoli Wang, Lei Yang, Hong Kang, Xiaojia Gao, Haijun Yu, Conghua Xie, Fuxiang Zhou, Yunfeng Zhou
Scientific Reports.2017;[Epub] CrossRef

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Usefulness of Change of Telomerase Activity as a Predictive Assay for Radiation Response: Hong Gyun Wu, Young Jue Kim, Il Han Kim, Charn Il Park, Sung Whan Ha; J Korean Cancer Assoc. 2000;32(6):1109-1114.

Abstract PDF: PURPOSE
A sensitive predictive assay is necessary to determine the total radiation dose according to sensitivity of individual cancer cell lines. This study is performed to determine whether the radiation sensitivity is correlated with the changes in telomerase activity after irradiation.
MATERIALS AND METHODS
Two colorectal cancer cell lines with different radiation sensitivity were used. In order to confirm the difference in radiation sensitivity, we used a calorimetric assay. Telomerase activities were measured using the PCR-based telomeric repeat amplification protocol (TRAP).
RESULTS
We confirmed the difference in radiation sensitivity between NCI-H630 and NCI-H716. Survival fractions at 2 Gy were 0.836 for NCI-H630 and 0.317 for NCI-H716. Telomerase activity increased after irradiation with NCI-H630, which was more resistant to radiation, whereas telomerase activity decreased with NCI-H730. But dose-dependent change of telomerase activity was not confirmed.
CONCLUSION
Our results suggested that telomerase activity change after irradiation could be used as a predictive assay for radiation response. Further studies with different cell lines and tumor tissues are necessary.

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Changes of Telomerase Activity by Protein Kinase C Modulators in Human Ovarian Cancer Cell Lines: Soo Young Hur, Joon Mo Lee, Sung Eun Namkoong, Jin Woo Kim; J Korean Cancer Assoc. 2000;32(4):724-733.

Abstract PDF: PURPOSE
This study was designed to find out whether protein kinase C (PKC) may affect telomerase activity in human ovarian cancers.
MATERIALS AND METHODS
To determine whether PKC modulators influence PKC activities, NIH: OVCAR-3 and CUMO-2, cells were treated with PKC inhibitors, G 6976 and bisindolyl maleimide I, and PKC activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA). Telomerase acti vity was determined by telomeric repeat amplification protocol (TRAP). Analysis of the expres sion of each telomerase subunits, human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT), was performed by RT-PCR. We also examined the alternative splicing of hTERT.
RESULTS
G 6976 and bisindolylmaleimide I inhibited PKC activity. Telomerase activities appeared to be affected in a time-dependent manner by these two PKC inhibitors. PKC activities were increased in parallel with telomerase activity by TPA at the low dose (10 nM), but their activities were down-regulated at the high dose (1 micrometer). RT-PCR demonstrated the presence of hTR and hTERT mRNA before and after the treatment of PKC modulators, respectively, and showed the presence of one alternatively spliced transcript and full-length hTERT transcripts.
CONCLUSION
These results showed that telomerase activity was affected by PKC and suggested PKC modulation may serve as an useful tool in the regulation of telomerase activity.

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Modulation of Telomerase Activity by p53 Gene in KATO - III Gastric Carcinoma Cell Line: Si Young Kim, Kyung Sam Cho, Jae Kyung Park, Young II Kim, Hwi Joong Yoon; J Korean Cancer Assoc. 1999;31(6):1112-1119.

Abstract PDF: PURPOSE
Alteration of p53 and telomerase activity may be responsible for gastric carcino- genesis. In this study, we tried to observe modulation of telomerase activity by wild type p53 in gastric cancer cell lines.
MATERIALS AND METHODS
We used five gastric cancer cell lines (KATO-III, AGS, SNU-1, SNU-5, SNU-16). In order to find p53 mutation, we used western blot and PCR-SSCP. The TRAP-eze kit which supplied by Oncor (Gaithersburg, MD) was used to detect telomerase activity of the five gastric carcinoma cell lines. The wild type p53 gene was transfected by electroporation method.
RESULTS
The expression of p53 protein was increased in four gastric carcinoma cell lines and one cell line (KATO-III) did not express. We found p53 point mutation in exon 5 and 8, and the p53 gene was deleted in KATO-III. The telomerase activity were observed in all five gastric carcinoma cell lines and there were no difference in telomere repeat length among five cell lines. After transfection with wild type p53, we could not find the change of telomerase activity in KATO-III.
CONCLUSION
Although activation of telomerase activity and mutation of p53 gene may be needed in gastric carcinogenesis, the telomerase activity was not affected by restoration of p53 function in gastric carcinoma cell lines.

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Semi - quantitative Comparison of Terminal Restriction Fragment Length and Telomerase in Breast Cancer for Biotherapy: Sun Young Rha, Kyu Hyun Park, Tae Soo Kim, Joo Hang Kim, Jae Kyung Roh, Jin Sik Min, Kyung Shik Lee, Byung Soo Kim, Hyun Cheol Chung; J Korean Cancer Assoc. 1998;30(2):231-241.

Abstract PDF: PURPOSE
We determined the clinical significance of telomerase activity and telomere length in breast cancer patients and also developed the measuring system of telomerase activity change with RNAse A pre-treatment.
MATERIALS AND METHODS
We measured the telomerase activity in 71 breast cancer tissues and paired normal tissues with TRAP (Telomeric Repeat Amplification Protocol) assay. Telomerase activity was calculated by computer-assisted densitometry compared to telomerase activity of the 293 control cell line. To develop the measuring system of telomerase activity modulation, we measured the telomerase activity after the treatment with RNAse A, 150microgram/ml, which inhibited 70% of telomerase activity compared to control in the 293 control cell line. In 59 paired tissues with telomerase activity, terminal restriction fragment (TRFs) length were measured using Southern blotting.
RESULTS
Sixty-three out of 71 cancer tissues showed telomerase activity (88.7%), while no telomerase activity was detected in their paired normal tissues. Telomerase activity was correlated to the node metastasis (p=0.02) and stage (p=0.005), but not to the tumor size or the hormonal receptor status. TRFs were neither specific to tumor tissues nor related to any of the clinical parameters. However, changes of TRFs of the tumor tissues from their paired normal tissues were correlated to the telomerase activities. Also the patients with different TRFs between cancer and normal tissues were in more advanced stage. After pre-treatment with the 150microgram/ml of RNAse A, telomerase activity in the tumor tissues showed variable inhibition. Relative inhibition, the ratio of inhibited telomerase activity in each tumor tissue compared to the inhibition of 293 control cell line, was proportional to the telomerase activity.
CONCLUSION
In breast cancer, telomerase activity was specific to the tumor tissues and correlated to tumor progression. A combination of telomerase activity and TRFs changes can be used as a guidline in detecting a better candidate for telomerase inhibition. Semi-quantitative assay with RI system can be used in evaluating the changes of telomerase activity after treatment with a new telomerase inhibitor with TRAP assay.

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Increment of Telomerase Activity with Breast Cancer Progression: Kyu Hyun Park, Sun Young Rha, Tae Soo Kim, Byung Chan Lee, Sei Ho Park, Hyun Cheol Chung, Won Young Lee, Joo Hang Kim, Jae Kyung Roh, Kyong Sik Lee, Jin Sik Min, Byung Soo Kim; J Korean Cancer Assoc. 1997;29(6):1032-1040.

Abstract PDF: PURPOSE
We studied the telomerase activity in normal and cancer tissues of the breast and then compared it to the clinical parameters.
MATERIALS AND METHODS
36 paired normal and cancerous breast tissues were assayed for telomerase activity by PCR-based TRAP assay (telomeric repeat amplification protocol). In 17 cancer tissues, flow cytometric analysis for S-phase fraction was done.
RESULTS
None of the normal breast tissue expressed telomerase activity while 23 out of 26 breast cancer tissue expressed telomerase activity (92%). Clinical parameters such as T-factor, tumor grade, hormone receptor expression, mitosis, S-phase fraction did not correlate with telomerase expression. However, telomerase acitvity increased with cancer progression such as; in a state of lymph node metastasis and in an advanced pathological stage.
CONCLUSION
Telomerase activity was expressed only from cancer tissues. And this expression increased with cancer progression suggesting a possible therapeutic target in breast cancer.

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Telomerase Activity in Human Cervical Carcinoma: Tae Sung Lee, Seong Il Suh, Won Ki Baek, Jong Wook Park, Soon Do Cha, Byung Kil Choe, Min Ho Suh; J Korean Cancer Assoc. 1996;28(4):733-739.

Abstract PDF: The Immortalization of normal eukaryotic cells is often associated with the reactivation of the ribonucleoprotein enzyme telomerase, which adds TTAGGG repeats on to the telomeres of chromosomes and is thought to be present in germ cells but not in normal somatic cells. Recently telomerase activity has been found in most immortalized human cell lines and various cancer tissues, but has not been found in most of normal somatic tissues. In present study, we show that telomerase activation can also occur in human cervical carcinomas. Extracts from 25 human cervical carcinomas and 10 normal cervical tissues were tested for telomerase activity using a recently developed polymerase chain reaction-based telomeric repeat amplification assay. Twenty(80%) of cervical carcinoma tissues were positive for telomerase acivity and 3(30%) of normal cervical tissues were also positive. There were no correlation between the level of telomerase activitty and degree of malignancy.This result suggest that telomerase activity seems to be uniquely relate to cervical carcinomas and telomerase appears to be repressed in normal tissues but may be reactivated in cervical carcinoms. Thus telomerase activity will be a useful marker for the cervical carcinomas.

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