Myc down-regulation induces apoptosis in M14 melanoma cells by increasing p27(kip1) levels.
In recent years, increasing evidence indicated the importance of a deregulated c-myc gene in the melanoma pathogenesis. We have previously demonstrated that treatment of melanoma cells with c-myc antisense oligodeoxynucleotides can inhibit cell proliferation and activate apoptosis. To gain insight into the mechanisms activated by Myc down-regulation, we have now developed an experimental model that allows modulating Myc protein expression in melanoma cells. This was achieved by originating stable melanoma cell clones expressing ecdysone-inducible c-myc antisense RNA. We show that the induction of c-myc antisense RNA in M14 melanoma cells leads to an inhibition of cell proliferation characterized by accumulation of cells in the G(1) phase of the cell cycle (up to 80%) and activation of apoptosis (50%). These data are associated with an increase of p27(kip1) levels and a significant reduction of the cdk2-associated kinase activity. In addition, we show that an ectopic overexpression of p27(kip1) in this experimental model can enhance the apoptotic rate. Our results indicate that down-regulation of Myc protein induces a G(1) arrest and activates apoptosis by increasing p27(kip1) content in melanoma cells, that are known to be defective for the p16-cyclinD/cdk4-pRb G(1) checkpoint. This is particularly relevant for identifying new therapeutic strategies based on the re-establishment of the apoptotic pathways in cancer cells.
D'Agnano
I
I
CNR, Istituto di Tecnologie Biomediche, V.le Marx 43, 00137 Roma, Italy.
Valentini
A
A
Fornari
C
C
Bucci
B
B
Starace
G
G
Felsani
A
A
Citro
G
G
D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism; D015536:Down-Regulation; D016193:G1 Phase / Q000502:physiology; D006801:Humans; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D016372:RNA, Antisense / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016213:Cyclins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D016271:Proto-Oncogene Proteins c-myc; D016372:RNA, Antisense; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27