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Cancer Research and Treatment > Volume 34(3); 2002 > Article
Cancer Research and Treatment 2002;34(3): 223-233. doi: https://doi.org/10.4143/crt.2002.34.3.223
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
1Cancer Metastasis Research Center, Korea.
2Department of Internal Medicine, Yonsei University Collegeof Medicine, Seoul, Korea.
3Brain Korea 21 Project for Medicine Science, YonseiUniversity College of Medicine, Seoul, Korea.
4Department of Hemato-oncology, Korea University College ofMedicine, Seoul, Korea.
5Lilly Korea, Ltd., Seoul, Korea.
  Published online: June 30, 2002.
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.
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.
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.
Key words: Telomerase;Senescence;Reverse transcriptase inhibitor;hTERT;c-Myc
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