Antisense telomerase treatment: induction of two distinct pathways, apoptosis and differentiation.
Telomerase, the enzyme that elongates telomeric DNA (TTAGGG)n, may be involved in cellular immortality and oncogenesis. To investigate the effect of inhibition of telomerase on tumor cells, we transfected the antisense vector against the human telomerase RNA into human malignant glioma cells exhibiting telomerase activity. After 30 doublings, some subpopulations of transfectants expressed a high level of interleukin-1beta-converting enzyme (ICE) protein and underwent apoptosis. In contrast, other subpopulations also showed enhanced ICE protein but escaped from apoptotic crisis and continued to grow, although their DNA synthesis, invasive ability, and tumorigenicity in nude mice were significantly reduced. Surviving cells demonstrated increased expression of glial fibrillary acidic protein and decreased motility, consistent with a more differentiated state. These cells also contained enhanced expression of the cyclin-dependent kinase inhibitors (CDKIs) p21 and p27. Treatment of surviving nonapoptotic cells with antisense oligonucleotides against p27, but not p21, induced apoptotic cell death, suggesting that p27 may have protected differentiating glioma cells from apoptosis. These data show that treatment with antisense telomerase inhibits telomerase activity and subsequently induces either apoptosis or differentiation. Regulation of these two distinct pathways may be dependent on the expression of ICE or CDKIs.
Kondo
S
S
Department of Neurosurgery, Brain Tumor/Neuro-Oncology Center, The Cleveland Clinic Foundation, Ohio 44195, USA. kondos@cesmtp.ccf.org
Tanaka
Y
Y
Kondo
Y
Y
Hitomi
M
M
Barnett
G H
GH
Ishizaka
Y
Y
Liu
J
J
Haqqi
T
T
Nishiyama
A
A
Villeponteau
B
B
Cowell
J K
JK
Barna
B P
BP
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020170:Caspase 1; D018797:Cell Cycle Proteins; D002454:Cell Differentiation / Q000187:drug effects; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism*; D005910:Glioma / Q000201:enzymology / Q000473:pathology; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D019098:Telomerase / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D016376:Oligonucleotides, Antisense; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D019098:Telomerase; D003546:Cysteine Endopeptidases; D020170:Caspase 1