Role of phosphatidylinositol 3-kinase-Akt pathway in nucleophosmin/anaplastic lymphoma kinase-mediated lymphomagenesis.
The NPM/ALK fusion gene, formed by the t(2;5) translocation in a subset of anaplastic large cell lymphomas, encodes a Mr 75,000 hybrid protein that contains the NH2-terminal portion of the nucleolar phosphoprotein nucleophosmin (NPM) joined to the entire cytoplasmic portion of the receptor tyrosine kinase anaplastic lymphoma kinase (ALK). NPM/ALK encodes a constitutively activated tyrosine kinase that belongs to the family of tyrosine kinases activated by chromosomal translocations. Our studies showed that NPM/ALK, similar to other members of this family, activates phosphatidylinositol 3-kinase (PI3K) and its downstream effector, serine/threonine kinase (Akt). PI3K was found in complex with NPM/ALK. Both PI3K and Akt kinase were permanently activated in NPM/ALK-transfected BaF3 murine hematopoietic cells and in NPM/ALK-positive, but not in NPM/ALK-negative, patient-derived anaplastic large cell lymphoma cell lines. In addition, Akt was phosphorylated/activated in protein samples isolated from four patients diagnosed with ALK-positive T/null-cell lymphomas. The PI3K inhibitors wortmannin and LY294002 induced apoptosis in NPM/ALK+ cells but exerted only minor effects on the control BaF3 parental cells and peripheral blood mononuclear cells stimulated by growth factors. Furthermore, retroviral infection of NPM/ALK+ BaF3 cells with a dominant-negative PI3K mutant (delta p85) or a dominant-negative Akt mutant (K179M) inhibited proliferation and clonogenic properties of the infected cells. Finally, the Akt mutant (K179M) suppressed the tumorigenicity of NPM/ALK-transfected BaF3 cells injected into syngeneic mice. In conclusion, our data indicate that NPM/ALK constitutively activates the PI3K-Akt pathway and that this pathway plays an important role in the NPM/ALK-mediated malignant transformation.
Slupianek
A
A
Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA.
Nieborowska-Skorska
M
M
Hoser
G
G
Morrione
A
A
Majewski
M
M
Xue
L
L
Morris
S W
SW
Wasik
M A
MA
Skorski
T
T
D000818:Animals; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D003470:Culture Media; D004789:Enzyme Activation; D005260:Female; D006133:Growth Substances / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000201:enzymology* / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000502:physiology*
D003470:Culture Media; D006133:Growth Substances; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C107023:p80(NPM-ALK) protein; C494918:AKT1 protein, human