G1-checkpoint function including a cyclin-dependent kinase 2 regulatory pathway as potential determinant of 7-hydroxystaurosporine (UCN-01)-induced apoptosis and G1-phase accumulation.
7-Hydroxystaurosporine (UCN-01), which was originally identified as a protein kinase C selective inhibitor, is currently in clinical trials as an anti-cancer drug. We previously showed that UCN-01 induced preferential G1-phase accumulation in tumor cells and this effect was associated with the retinoblastoma (Rb) protein and its regulatory factors, such as cyclin-dependent kinase 2 (CDK2) and CDK inhibitors p21Cip1/WAF1 and p27Kip1. We demonstrate here that G1-phase accumulation was induced by UCN-01 in Rb-proficient cell lines (WiDr and HCT116 human colon carcinomas and WI-38 human lung fibroblast), and it was accompanied by dephosphorylation of Rb. In addition, UCN-01-induced G1-phase accumulation was also demonstrated in a Rb-defective cell line (Saos-2 human osteosarcoma), but not in a simian virus 40 (SV40)-transformed cell line (WI-38 VA13). Apoptosis was induced by UCN-01 in the two Rb-deficient cell lines, but not in the other Rb-proficient cell lines. These observations suggest that G1-checkpoint function might be important for cell survival during UCN-01 treatment. In addition, there may be a UCN-01-responsive factor in the G1-checkpoint machinery other than Rb which is targeted by SV40. Further studies revealed a correlation between UCN-01-induced G1-phase accumulation and reduction of cellular CDK2 kinase activity. This reduction was strictly dependent on down-regulation of the Thr160-phosphorylated form of CDK2 protein, and coincided in part with up-regulation of p27Kip1, but it was independent of the level of the p21Cip1/WAF1 protein. These results suggest that G1-checkpoint function, including a CDK2-regulatory pathway, may be a significant determinant of the sensitivity of tumor cells to UCN-01.
Akiyama
T
T
Pharmaceutical Research Institute, Kyowa Hakko Kogyo Co., Ltd., Sunto-gun, Shizuoka.
Sugiyama
K
K
Shimizu
M
M
Tamaoki
T
T
Akinaga
S
S
D000470:Alkaloids / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology; D002461:Cell Line, Transformed; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D016213:Cyclins / Q000096:biosynthesis / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects*; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000502:physiology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D019311:Staurosporine / Q000031:analogs & derivatives; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D000470:Alkaloids; D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D008869:Microtubule-Associated Proteins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C054852:7-hydroxystaurosporine; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D019311:Staurosporine