Vitamin E succinate inhibits proliferation of BT-20 human breast cancer cells: increased binding of cyclin A negatively regulates E2F transactivation activity.
Vitamin E succinate (VES) inhibited the proliferation of the estrogen receptor-negative human breast cancer cell line, BT-20, in the G1 phase of the cell cycle. The E2F proteins are integral transcriptional components in the regulation of cell growth. Overexpression of E2F-1 blocked the ability of VES to inhibit BT-20 cell growth, suggesting that VES regulation of E2F-1 activity leads to growth arrest of BT-20 cells. VES, although having little effect on E2F-1 steady-state protein levels, decreased E2F-1 phosphorylation and transactivation activity and increased cyclin A binding to E2F-1. GAL4-E2F-1 deletion mutant studies indicated that cyclin A negatively regulates E2F function. In VES-treated BT-20 cells, the cyclin A protein exhibited reduced kinase activity, which correlated with decreased steady-state levels and binding of cyclin-dependent kinase-2 to cyclin A and increased steady-state levels and binding of p21cip1 to cyclin A and cyclin-dependent kinase-2. The functional consequence of the negative regulatory effect of VES on E2F-1 function was shown by the ability of VES to inhibit the transcriptional activation of an E2F-1 responsive gene, c-myc. These studies show that VES induces growth inhibition of BT-20 cells through a mechanism that involves cyclin A-negative regulation of E2F-mediated transcription.
Turley
J M
JM
Division of Basic Sciences, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702, USA.
Ruscetti
F W
FW
Kim
S J
SJ
Fu
T
T
Gou
F V
FV
Birchenall-Roberts
M C
MC
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000473:pathology / Q000517:prevention & control*; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005260:Female; D006801:Humans; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D024505:Tocopherols; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D014810:Vitamin E; D024505:Tocopherols