Telomerase- and alternative telomere lengthening-independent telomere stabilization in a metastasis-derived human non-small cell lung cancer cell line: effect of ectopic hTERT.
In the majority of human malignancies, maintenance of telomeres is achieved by reactivation of telomerase, whereas a smaller fraction uses an alternative telomere lengthening (ALT) mechanism. Here, we used 16 non-small cell lung cancer (NSCLC) cell lines to investigate telomere stabilization mechanisms and their effect on tumor aggressiveness. Three of 16 NSCLC cell lines (VL-9, SK-LU-1, and VL-7) lacked telomerase activity, correlating with significantly reduced tumorigenicity in vitro and in vivo. Of the three telomerase-negative cell lines, only SK-LU-1 displayed characteristics of an ALT mechanism (i.e., highly heterogeneous telomeres and ALT-associated promyelocytic leukemia bodies). VL-9 cells gained telomerase during in vitro propagation, indicating incomplete immortalization in vivo. In contrast, NSCLC metastasis-derived VL-7 cells remained telomerase and ALT negative up to high passage numbers and following transplantation in severe combined immunodeficient mice. Telomeres of VL-7 cells were homogeneously short, and chromosomal instability (CIN) was comparable with most telomerase-positive cell lines. This indicates the presence of an efficient telomere stabilization mechanism different from telomerase and ALT in VL-7 cells. To test the effect of ectopic telomerase reverse transcriptase (hTERT) in these unique ALT- and telomerase-negative tumor backgrounds, hTERT was transfected into VL-7 cells. The activation of telomerase led to an excessively rapid gain of telomeric sequences resulting in very long ( approximately 14 kb), uniform telomeres. Additionally, hTERT expression induced a more aggressive growth behavior in vitro and in vivo without altering the level of CIN. These data provide further evidence for a direct oncogenic activity of hTERT not based on the inhibition of CIN.
Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Borschkegasse 8a, A-1090 Vienna, Austria.
Andreas
A
Brachner
Soleman
S
Sasgary
Christine
C
Pirker
Chantal
C
Rodgarkia
Mario
M
Mikula
Wolfgang
W
Mikulits
Helga
H
Bergmeister
Ulrike
U
Setinek
Matthias
M
Wieser
Suet-Feung
SF
Chin
Carlos
C
Caldas
Michael
M
Micksche
Christa
C
Cerni
Walter
W
Berger
D000818:Animals; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016513:Mice, SCID; D019098:Telomerase / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology / Q000502:physiology; D016615:Telomere; D014162:Transfection
D004268:DNA-Binding Proteins; D019098:Telomerase