The tryphostin AG17 induces apoptosis and inhibition of cdk2 activity in a lymphoma cell line that overexpresses bcl-2.
Tyrphostins are low molecular weight compounds that specifically inhibit protein tyrosine kinases. We studied the effects of tyrphostins on OCI-Ly8, a cell line derived from a patient with immunoblastic lymphoma that carries the t(14;18) translocation and overexpresses the B-cell lymphoma/leukemia-2 gene (bcl-2). To test the possibility that tyrphostins induce apoptosis in these cells, overcoming the protection rendered by bcl-2, we screened 16 tyrphostins representing different families at a concentration of 0.5-50 microM. We found that AG17 was the most potent in this regard. Cell cycle analysis demonstrated that AG17 induces arrest at the G1 phase followed by apoptosis with general reduction of the intracellular level of tyrosine-phosphorylated proteins. To further elucidate the mechanism of action of AG17, we investigated its effect on some of the key proteins that regulate the cell cycle. Bcl-2 and cdk2 protein levels were not altered with AG17, whereas cdk2 kinase activity, as well as p21 and p16 protein levels, were reduced markedly. These results suggest that the target of AG17 is inactivation of cdk2. Because lymphoma cells with the t(14;18) translocation and bcl-2 overexpression are resistant to chemotherapy, novel drugs selectively able to induce apoptosis in these cells could offer a new approach to the treatment of lymphoma patients.
Palumbo
G A
GA
Institute of Hematology, University of Catania, Italy.
Yarom
N
N
Gazit
A
A
Sandalon
Z
Z
Baniyash
M
M
Kleinberger-Doron
N
N
Levitzki
A
A
Ben-Yehuda
D
D
D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase; D006801:Humans; D008223:Lymphoma / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors; D010636:Phenols / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020032:Tyrphostins
C493956:CDKN1A protein, human; D002352:Carrier Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D009570:Nitriles; D019384:Nucleic Acid Synthesis Inhibitors; D010636:Phenols; D019253:Proto-Oncogene Proteins c-bcl-2; D020032:Tyrphostins; C001784:SF 6847; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases