Regulation of estrogen-mediated cell survival and proliferation by p160 coactivators.
BACKGROUND
Estrogen receptor (ER) activity is dependent on coactivator (CoA) proteins. The role of CoA-ER interactions in breast cancer apoptosis remains unexplored.


METHODS
Expression vectors for the p160 CoA genes NCOA-1, NCOA-2, or NCOA-3 were transiently transfected into MCF-7 cells. Cell survival was determined by viability and clonogenic survival assays. Effects of CoA expression on estrogen (E2) signaling were determined by estrogen response element (ERE)-luciferase reporter-gene assay. Clonogenic and reporter-gene survival assays were used to examine the molecular inhibition of CoA function (dominant inhibitory [DI]-decoy-CoA) on cell survival. Statistical significance was established at the P < .05 level.


RESULTS
Overexpression of NCOA-1, NCOA-2, and NCOA-3 enhanced E2-mediated gene expression by 3.17 +/- 0.51-, 2.33 +/- 0.8-, and 3.65 +/- 0.65-fold, respectively, and enhanced cell survival by suppressing tumor necrosis factor alpha (TNF-alpha)-induced cell death from 80.23% +/- 2.66% viability to 101.5% +/- 8.9%, 86.9% +/- 9.9%, and 95.7% +/- 8.5% viability, respectively. NCOA-1 enhancement of cell survival occurred via suppression of TNF-alpha-induced apoptosis as confirmed by viability and morphologic evaluation. Clonogenic survival and E2-stimulated colony formation in MCF-7 cells were suppressed by expression of DI-decoy-NCOA-1 and DI-decoy-NCOA-3 to 34.4% +/- 7.4% and 54% +/- 5.4% of vector control, but not DI-decoy-NCOA-2.


CONCLUSIONS
Overexpression of NCOA-1 and NCOA-3 exerted potent survival effects in breast carcinoma cells. Use of DI-CoA constructs enhanced TNF-alpha-induced cell death and abrogated E2-induced survival. Inhibition of CoA proteins represents a mechanism for enhancing sensitivity therapies in breast carcinoma.
Department of Surgery, Tulane Cancer Center, New Orleans, LA 70112, USA.
Christopher B
CB
Weldon
Steven
S
Elliott
Yun
Y
Zhu
John L
JL
Clayton
Tyler J
TJ
Curiel
Bernard M
BM
Jaffe
Matthew E
ME
Burow
D000123:Acetyltransferases; D001943:Breast Neoplasms / Q000473:pathology* / Q000628:therapy; D002455:Cell Division; D045744:Cell Line, Tumor; D002470:Cell Survival; D004967:Estrogens / Q000502:physiology*; D005260:Female; D051548:Histone Acetyltransferases; D006801:Humans; D056920:Nuclear Receptor Coactivator 1; D051958:Nuclear Receptor Coactivator 2; D056921:Nuclear Receptor Coactivator 3; D015513:Oncogene Proteins; D011960:Receptors, Estrogen / Q000502:physiology; D020218:Response Elements; D013629:Tamoxifen / Q000494:pharmacology; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004967:Estrogens; C498001:NCOA2 protein, human; D051958:Nuclear Receptor Coactivator 2; D015513:Oncogene Proteins; D011960:Receptors, Estrogen; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D013629:Tamoxifen; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538866:NCOA3 protein, human; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3