Differential transcriptional regulation of human telomerase in a cellular model representing important genetic alterations in esophageal squamous carcinogenesis.
Telomerase activity is observed in approximately 90% of human cancer including esophageal squamous cell cancer. Normal somatic cells do not display telomerase activity on a regular basis. The major mechanism to regulate telomerase activity in human cells is the transcriptional control of the catalytic subunit, the human reverse transcriptase gene hTERT. However, the manner in which telomerase activity is regulated during malignant transformation and whether this regulation is influenced by single genetic alterations important in this process are not well understood. In this study we investigated the transcriptional regulation and activity of human telomerase in a cellular model representing important known genetic alterations observed in esophageal cancer. We characterized the respective cells with regard to their telomere biology and telomerase expression, transcriptional regulation using promoter--as well as electrophoretic mobility shift assay--analyses and their promoter methylation status. We could demonstrate that telomerase expression and subsequent activity are differentially regulated in the progression from normal esophageal epithelial cells to genetically defined esophageal cells harboring a specific genetic alteration frequently found in esophageal cancer and compared those changes with esophageal cancer cells. Whereas primary esophageal cells are mainly regulated by Sp1, in cells harboring a genetic alteration as cyclin D1 overexpression other transcription factors like E2F and c-myc as well as promoter methylation influence hTERT transcription. This model demonstrates that the transcriptional regulation of telomerase is influenced by a given genetic alteration important in esophageal cancer, and therefore provides new insight in telomerase regulation during carcinogenesis.
Quante
Michael
M
Department of Medicine and Institute of Molecular Medicine and Cell Research, University of Freiburg, Freiburg, Germany.
Heeg
Steffen
S
von Werder
Alexander
A
Goessel
Gitta
G
Fulda
Christine
C
Doebele
Michaela
M
Nakagawa
Hiroshi
H
Beijersbergen
Roderick
R
Blum
Hubert E
HE
Opitz
Oliver G
OG
D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D050684:E2F Transcription Factors / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000473:pathology; D004947:Esophagus / Q000378:metabolism / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection
D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D016271:Proto-Oncogene Proteins c-myc; D016329:Sp1 Transcription Factor; D019098:Telomerase