Overexpression of p21waf1 leads to increased inhibition of E2F-1 phosphorylation and sensitivity to anticancer drugs in retinoblastoma-negative human sarcoma cells.
The effect of overexpression of p21waf1 on drug sensitivity was studied in an osteosarcoma cell line (SaOs-2) lacking both p53 and functional retinoblastoma protein using a tetracycline (TC)-inducible expression system. p21waf1 expression was barely detectable in SaOS-2 cells incubated in the presence of TC. After TC withdrawal, high levels of p21waf1 were induced in these cells. These p21waf1-induced cells showed increased sensitivity to doxorubicin, tomudex, and methotrexate as compared to uninduced cells; this condition is associated with increased apoptosis. Expression of p21waf1 reduced cyclin A-associated kinase activity and, surprisingly, resulted in inhibition of phosphorylation of E2F-1 and increased E2F-1 binding activity. An S-G2 cell cycle arrest/delay and an increase in expression of E2F-responsive genes (dihydrofolate reductase and thymidylate synthase) was correspondingly observed. Overexpression of p21waf1 in cells lacking functional retinoblastoma protein may mediate sensitivity to anticancer drugs by inhibiting E2F-1 phosphorylation, which may contribute to increased S-G2 cell cycle delay and increased cell susceptibility to apoptosis.
Li
W W
WW
Laboratory of Molecular Pharmacology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Fan
J
J
Hochhauser
D
D
Bertino
J R
JR
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D002352:Carrier Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004317:Doxorubicin / Q000494:pharmacology; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology; D012516:Osteosarcoma / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011799:Quinazolines / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D013752:Tetracycline / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D013876:Thiophenes / Q000494:pharmacology; D013940:Thymidylate Synthase / Q000235:genetics; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic; D000964:Antimetabolites, Antineoplastic; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D011799:Quinazolines; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D013876:Thiophenes; D050680:Transcription Factor DP1; D014157:Transcription Factors; D004317:Doxorubicin; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D018844:Cyclin-Dependent Kinases; D013752:Tetracycline; C068874:raltitrexed; D008727:Methotrexate