Induction of hTERT expression and phosphorylation by estrogen via Akt cascade in human ovarian cancer cell lines.
We examined the mechanism by which estrogen regulates telomerase activity in Caov-3 human ovarian cancer cell lines, which express ER, to determine whether the regulation affects the expression and/or phosphorylation of the telomerase catalytic subunit (hTERT). 17beta-Estradiol (E(2)) induced telomerase activity and hTERT expression. Transient expression assays using luciferase reporter plasmids containing various fragments of hTERT promoter showed that the estrogen-responsive element appeared to be partially responsible for the E(2)-induced activation of the hTERT promoter. Either pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, or transfection with a dominant-negative Akt attenuated the E(2)-induced activation of the hTERT promoter. In addition, estrogen induced the phosphorylation of IkappaB inhibitor protein via the Akt cascade, and cotransfection with a dominant-negative subunit of NFkappaB attenuated the response of the ERE-deleted hTERT promoter to E(2). Moreover, E(2) induced the phosphorylation of hTERT, the association of 14-3-3 protein and NFkappaB with hTERT, and nuclear accumulation of hTERT in an Akt-dependent manner. These results indicate that E(2) induces telomerase activity not only by transcriptional regulation of hTERT via an ERE-dependent mechanism and a PI3K/Akt/NFkappaB cascade, but also by post-transcriptional regulation via Akt-dependent phosphorylation of hTERT. Thus, the phosphorylation of Akt is a key event in the induction of telomerase activity by E(2) in human ovarian cancer cells.
Kimura
Akiko
A
Department of Obstetrics and Gynecology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Ohmichi
Masahide
M
Kawagoe
Jun
J
Kyo
Satoru
S
Mabuchi
Seiji
S
Takahashi
Toshifumi
T
Ohshima
Chika
C
Arimoto-Ishida
Emi
E
Nishio
Yukihiro
Y
Inoue
Masaki
M
Kurachi
Hirohisa
H
Tasaka
Keiichi
K
Murata
Yuji
Y
D048948:14-3-3 Proteins; D002467:Cell Nucleus / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D020672:I-kappa B Proteins / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction; D019098:Telomerase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D048948:14-3-3 Proteins; D002867:Chromones; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D004958:Estradiol; D004967:Estrogens; D020672:I-kappa B Proteins; D009025:Morpholines; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011960:Receptors, Estrogen; D019098:Telomerase; D014446:Tyrosine 3-Monooxygenase; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human