Adenovirus-mediated overexpression of p15INK4B inhibits human glioma cell growth, induces replicative senescence, and inhibits telomerase activity similarly to p16INK4A.
The genes encoding the cyclin-dependent kinase inhibitors p16INK4A (CDKN2A) and p15INK4B (CDKN2B) are frequently homozygously deleted in a variety of tumor cell lines and primary tumors, including glioblastomas in which 40-50% of primary tumors display homozygous deletions of these two loci. Although the role of p16 as a tumor suppressor has been well documented, it has remained less well studied whether p15 plays a similar growth-suppressing role. Here, we have used replication-defective recombinant adenoviruses to compare the effects of expressing wild-type p16 and p15 in glioma cell lines. After infection, high levels of p16 and p15 were observed in two human glioma cell lines (U251 MG and U373 MG). Both inhibitors were found in complex with CDK4 and CDK6. Expression of p16 and p15 had indistinguishable effects on U251 MG, which has homozygous deletion of CDKN2A and CDKN2B, but a wild-type retinoblastoma (RB) gene. Cells were growth-arrested, showed no increased apoptosis, and displayed a markedly altered cellular morphology and repression of telomerase activity. Transduced cells became enlarged and flattened and expressed senescence-associated beta-galactosidase, thus fulfilling criteria for replicative senescence. In contrast, the growth and morphology of U373 MG, which expresses p16 and p15 endogenously, but undetectable levels of RB protein, were not affected by exogenous overexpression of either inhibitor. Thus, we conclude that overexpression of p15 has a similar ability to inhibit cell proliferation, to cause replicative senescence, and to inhibit telomerase activity as p16 in glioma cells with an intact RB protein pathway.
Ludwig Institute for Cancer Research, Stockholm Branch, Sweden.
J
J
Fuxe
G
G
Akusjärvi
H M
HM
Goike
G
G
Roos
V P
VP
Collins
R F
RF
Pettersson
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D048429:Cell Size; D016922:Cellular Senescence; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004790:Enzyme Induction; D005910:Glioma; D006801:Humans; D015151:Immunoblotting; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins
C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D017346:Protein Serine-Threonine Kinases; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D019098:Telomerase