Abstract
The mechanisms of cell transformation mediated by the nucleophosmin (NPM)/anaplastic lymphoma kinase (ALK) tyrosine kinase are only partially understood. Here, we report that cell lines and native tissues derived from the NPM/ALK-expressing T-cell lymphoma display persistent activation of mammalian target of rapamycin (mTOR) as determined by phosphorylation of mTOR targets S6rp and 4E-binding protein 1 (4E-BP1). The mTOR activation is serum growth factor-independent but nutrient-dependent. It is also dependent on the expression and enzymatic activity of NPM/ALK as demonstrated by cell transfection with wild-type and functionally deficient NPM/ALK, small interfering RNA (siRNA)-mediated NPM/ALK depletion and kinase activity suppression using the inhibitor WHI-P154. The NPM/ALK-induced mTOR activation is transduced through the mitogen-induced extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway and, to a much lesser degree, through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway. Accordingly, whereas the low-dose PI3K inhibitor wortmannin and Akt inhibitor III profoundly inhibited Akt phosphorylation, they had a very modest effect on S6rp and 4E-BP1 phosphorylation. In turn, MEK inhibitors U0126 and PD98059 and siRNA-mediated depletion of either ERK1 or ERK2 inhibited S6rp phosphorylation much more effectively. Finally, the mTOR inhibitor rapamycin markedly decreased proliferation and increased the apoptotic rate of ALK+TCL cells. These findings identify mTOR as a novel key target of NPM/ALK and suggest that mTOR inhibitors may prove effective in therapy of ALK-induced malignancies.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Anaplastic Lymphoma Kinase
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Animals
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Blotting, Western
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Cell Line
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Cell Line, Tumor
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Cell Proliferation / drug effects
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Cell Survival / drug effects
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Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
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Extracellular Signal-Regulated MAP Kinases / genetics
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Extracellular Signal-Regulated MAP Kinases / metabolism
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Humans
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Immunohistochemistry
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Lymphoma, T-Cell / genetics
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Lymphoma, T-Cell / metabolism
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Lymphoma, T-Cell / pathology
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / genetics
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Mitogen-Activated Protein Kinases / metabolism
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Models, Biological
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Nucleophosmin
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphatidylinositol 3-Kinases / pharmacology
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Phosphoinositide-3 Kinase Inhibitors
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Protein Kinase Inhibitors
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Protein Kinases / genetics
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Protein Kinases / metabolism*
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Proto-Oncogene Proteins c-akt / antagonists & inhibitors
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism
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Quinazolines / pharmacology
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RNA, Small Interfering / genetics
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Receptor Protein-Tyrosine Kinases
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Signal Transduction / drug effects*
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Sirolimus / pharmacology*
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TOR Serine-Threonine Kinases
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Transfection
Substances
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NPM1 protein, human
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Nuclear Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Protein Kinase Inhibitors
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Quinazolines
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RNA, Small Interfering
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WHI P154
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Nucleophosmin
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Protein Kinases
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MTOR protein, human
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ALK protein, human
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Anaplastic Lymphoma Kinase
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Protein-Tyrosine Kinases
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Receptor Protein-Tyrosine Kinases
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Proto-Oncogene Proteins c-akt
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TOR Serine-Threonine Kinases
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Extracellular Signal-Regulated MAP Kinases
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Mitogen-Activated Protein Kinases
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Sirolimus