Basic Research
Copyright ©The Author(s) 2002. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 15, 2002; 8(2): 357-362
Published online Apr 15, 2002. doi: 10.3748/wjg.v8.i2.357
Telomere and telomerase in the initial stage of immortalization of esophageal epithelial cell
Zhong-Ying Shen, Li-Yan Xu, En-Min Li, Wei-Jia Cai, Min-Hua Chen, Jian Shen, Yi Zeng
Zhong-Ying Shen, Li-Yan Xu, Wei-Jia Cai, Min-Hua Chen, Jian Shen, Department of Tumor Pathology, Medical College of Shantou University, Shantou 515031, Guangdong Province, China
En-Min Li, Department of Biochemistry and Molecular Biology, Medical College of Shantou University, Shantou 515031, Guangdong Province, China
Yi Zeng, Institute of Virology, Chinese Academy of Preventive Medicine, Beijing 100052, China
Author contributions: All authors contributed equally to the work.
Supported by the National Natural Science Foundation of Chines, No. 39830380
Correspondence to: Dr. Zhong-Ying Shen, Department of Tumor Pathology, Medical College of Shantou University, 22 Xinling Road, Shantou 515031, Guandong Province, China. zhongyingshen@yahoo.com
Telephone: +86-75-8538621 Fax: +86-754-8537516
Received: September 26, 2001
Revised: October 15, 2001
Accepted: November 1, 2001
Published online: April 15, 2002
Abstract

AIM: To search for the biomarker of cellular immortalization, the telomere length, telomerase activity and its subunits in cultured epithelial cells of human fetal esophagus in the process of immortalization.

METHODS: The transgenic cell line of human fetal esophageal epithelium (SHEE) was established with E6E7 genes of human papillomavirus (HPV) type 18 in our laboratory. Morphological phenotype of cultured SHEE cells from the 6th to 30th passages, was examined by phase contrast microscopy, the telomere length was assayed by Southern blot method, and the activity of telomerase was analyzed by telomeric repeat amplification protocol (TRAP). Expressions of subunits of telomerase, hTR and hTERT, were assessed by RT-PCR. DNA content in cell cycle was detected by flow cytometry. The cell apoptosis was examined by electron microscopy (EM) and TUNEL label.

RESULTS: SHEE cells from the 6th to 10th passages showed cellular proliferation with a good differentiation. From the 12th to the 16th passages, many senescent and apoptotic cells appeared, and the telomere length sharply shortened from 23 kb to 17 kb without expression of hTERT and telomerase activity. At the 20th passage, SHEE cells overcame the senescence and apoptosis and restored their proliferative activity with expression of telomerase and hTERT at low levels, but the telomere length shortened continuously to the lowest of 3 kb. After the 30th passage cells proliferation was restored by increment of cells at S and G2M phase in the cell cycle and telomerase activity expressed at high levels and with maintenance of telomere length.

CONCLUSION: At the early stage of SHEE cells, telomeres are shortened without expression of telomerase and hTERT causing cellular senescence and cell death. From the 20th to the 30th passages, the activation of telomerase and maintenance of telomere length show a progressive process for immortalization of esophageal epithelial cells. The expression of telomerase may constitute a biomarker for detection of immortalization of cells.

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