A novel telomere elongation in an adriamycin-resistant stomach cancer cell line with decreased telomerase activity

Jun Hyun Kim, Gun Eui Lee, Jin Cheon Kim, Jun Ho Lee, In Kwon Chung

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Actively dividing cells show progressive loss of telomeric DNA during successive rounds of replication due to end-replication problem. Telomere shortening has been proposed as a regulatory mechanism that controls the replicative capacity of primary cells before undergoing cellular senescence. In immortal cells including cancer, cellular senescence can be overcome by reactivation of telomerase or by a telomerase-independent mechanism for lengthening telomeres. In this work, we present a novel example of telomere elongation mechanism in a human stomach adenocarcinoma cell line which was selected for resistance to adriamycin. The resistant cell line (MKN/ADR) had long terminal restriction fragments (TRFs) of up to ∼50 kb, while its parent cell line (MKN-45) had the TRFs, consisting of a smear extending from ∼4 to ∼25 kb. The very large TRFs in MKN/ADR cell line were proven to be telomeric by digestion with the exonuclease Bal31, When telomerase activity was examined using the PCR-based telomeric repeat amplification protocol (TRAP) assay, MKN/ADR cell line showed reduced activity to about 10% of that in MKN-45 cell line. The correlation between reduced telomerase activity and mRNA expression of telomerase subunits in MKN/ADR cell line was assessed by the reverse transcriptase-PCR analysis. The level of human telomerase reverse transcriptase (hTERT) mRNA was lower in MKN/ADR cell line than in MKN-45 cell line. This observation correlates with the finding that telomerase activity is reduced about 10-fold in MKN/ADR cell line. Reverse transcriptase-PCR analysis also revealed a close correlation between telomerase-associated protein (TP1) mRNA expression and telomerase activity in MKN/ADR cell line. In contrast, expression levels of human telomerase RNA (hTR) were identical in both MKN/ADR and MKN-45 cell lines. Taken together, these data suggest that telomeres in MKN/ADR cell line may be regulated through a novel mechanism other than telomerase. Although the basis for telomere elongation mechanism in MKN/ADR cell line is not yet understood, the occurrence of alternative mechanism for telomere elongation in drug-resistant cancer cells may have an important implication for use of telomerase inhibitors in human cancer treatment.

Original languageEnglish
Pages (from-to)228-236
Number of pages9
JournalMolecules and cells
Volume13
Issue number2
Publication statusPublished - 2002 Apr 1

Fingerprint

Telomerase
Telomere
Doxorubicin
Stomach Neoplasms
Cell Line
Cell Aging
Reverse Transcriptase Polymerase Chain Reaction
Messenger RNA
Telomere Homeostasis
Telomere Shortening
Neoplasms
Exonucleases
Digestion
Stomach
Adenocarcinoma

All Science Journal Classification (ASJC) codes

  • Medicine(all)

Cite this

Kim, Jun Hyun ; Lee, Gun Eui ; Kim, Jin Cheon ; Lee, Jun Ho ; Chung, In Kwon. / A novel telomere elongation in an adriamycin-resistant stomach cancer cell line with decreased telomerase activity. In: Molecules and cells. 2002 ; Vol. 13, No. 2. pp. 228-236.
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abstract = "Actively dividing cells show progressive loss of telomeric DNA during successive rounds of replication due to end-replication problem. Telomere shortening has been proposed as a regulatory mechanism that controls the replicative capacity of primary cells before undergoing cellular senescence. In immortal cells including cancer, cellular senescence can be overcome by reactivation of telomerase or by a telomerase-independent mechanism for lengthening telomeres. In this work, we present a novel example of telomere elongation mechanism in a human stomach adenocarcinoma cell line which was selected for resistance to adriamycin. The resistant cell line (MKN/ADR) had long terminal restriction fragments (TRFs) of up to ∼50 kb, while its parent cell line (MKN-45) had the TRFs, consisting of a smear extending from ∼4 to ∼25 kb. The very large TRFs in MKN/ADR cell line were proven to be telomeric by digestion with the exonuclease Bal31, When telomerase activity was examined using the PCR-based telomeric repeat amplification protocol (TRAP) assay, MKN/ADR cell line showed reduced activity to about 10{\%} of that in MKN-45 cell line. The correlation between reduced telomerase activity and mRNA expression of telomerase subunits in MKN/ADR cell line was assessed by the reverse transcriptase-PCR analysis. The level of human telomerase reverse transcriptase (hTERT) mRNA was lower in MKN/ADR cell line than in MKN-45 cell line. This observation correlates with the finding that telomerase activity is reduced about 10-fold in MKN/ADR cell line. Reverse transcriptase-PCR analysis also revealed a close correlation between telomerase-associated protein (TP1) mRNA expression and telomerase activity in MKN/ADR cell line. In contrast, expression levels of human telomerase RNA (hTR) were identical in both MKN/ADR and MKN-45 cell lines. Taken together, these data suggest that telomeres in MKN/ADR cell line may be regulated through a novel mechanism other than telomerase. Although the basis for telomere elongation mechanism in MKN/ADR cell line is not yet understood, the occurrence of alternative mechanism for telomere elongation in drug-resistant cancer cells may have an important implication for use of telomerase inhibitors in human cancer treatment.",
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A novel telomere elongation in an adriamycin-resistant stomach cancer cell line with decreased telomerase activity. / Kim, Jun Hyun; Lee, Gun Eui; Kim, Jin Cheon; Lee, Jun Ho; Chung, In Kwon.

In: Molecules and cells, Vol. 13, No. 2, 01.04.2002, p. 228-236.

Research output: Contribution to journalArticle

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T1 - A novel telomere elongation in an adriamycin-resistant stomach cancer cell line with decreased telomerase activity

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AU - Lee, Gun Eui

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AU - Chung, In Kwon

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AB - Actively dividing cells show progressive loss of telomeric DNA during successive rounds of replication due to end-replication problem. Telomere shortening has been proposed as a regulatory mechanism that controls the replicative capacity of primary cells before undergoing cellular senescence. In immortal cells including cancer, cellular senescence can be overcome by reactivation of telomerase or by a telomerase-independent mechanism for lengthening telomeres. In this work, we present a novel example of telomere elongation mechanism in a human stomach adenocarcinoma cell line which was selected for resistance to adriamycin. The resistant cell line (MKN/ADR) had long terminal restriction fragments (TRFs) of up to ∼50 kb, while its parent cell line (MKN-45) had the TRFs, consisting of a smear extending from ∼4 to ∼25 kb. The very large TRFs in MKN/ADR cell line were proven to be telomeric by digestion with the exonuclease Bal31, When telomerase activity was examined using the PCR-based telomeric repeat amplification protocol (TRAP) assay, MKN/ADR cell line showed reduced activity to about 10% of that in MKN-45 cell line. The correlation between reduced telomerase activity and mRNA expression of telomerase subunits in MKN/ADR cell line was assessed by the reverse transcriptase-PCR analysis. The level of human telomerase reverse transcriptase (hTERT) mRNA was lower in MKN/ADR cell line than in MKN-45 cell line. This observation correlates with the finding that telomerase activity is reduced about 10-fold in MKN/ADR cell line. Reverse transcriptase-PCR analysis also revealed a close correlation between telomerase-associated protein (TP1) mRNA expression and telomerase activity in MKN/ADR cell line. In contrast, expression levels of human telomerase RNA (hTR) were identical in both MKN/ADR and MKN-45 cell lines. Taken together, these data suggest that telomeres in MKN/ADR cell line may be regulated through a novel mechanism other than telomerase. Although the basis for telomere elongation mechanism in MKN/ADR cell line is not yet understood, the occurrence of alternative mechanism for telomere elongation in drug-resistant cancer cells may have an important implication for use of telomerase inhibitors in human cancer treatment.

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