OBJECTIVETo observe the expression of ER alpha and SMRT in ER alpha-positive and -negative cell lines before and after treatment with tamoxifen (TAM).

METHODSBreast cancer T47D cells (ER alpha-positive) and MDA-MB-231 cells (ER alpha-negative) were treated with TAM, cell viability was measured by MMT assay before and after TAM treatment. Flow cytometry (FCM) was applied to analyze apoptosis rate and cell cycle. Immunohistochemistry and Western blot were used to test ER alpha and SMRT expression in T-47D and MDA-MB-231 cells with and without TAM treatment.

RESULTProliferation rate of T-47D and MDA-MB-231 decreased after 0.10 mmol/L TAM treatment for 48 h compared with control group (P <0.05), especially that of T47D cells. The result of FCM showed that sub-diploid apoptosis peak was found in both cell lines after TAM treatment. Immunohistochemistry and Western blot indicated that T-47D cells presented ER alpha++ and SMRT++, and ER alpha expression decreased after TAM treatment, meanwhile, that of SMRT increased. MDA-MB-231 cells presented ER alpha-, SMRT-, and both expression levels increased slightly after TAM treatment.

CONCLUSIONTAM can inhibit the proliferation of breast cancer cells by inducing cell apoptosis,which is associated with alteration of ER alpha and SMRT expression.

Antineoplastic Agents, Hormonal ; pharmacology ; Apoptosis ; drug effects ; Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Estrogen Receptor alpha ; metabolism ; Female ; Humans ; Nuclear Receptor Co-Repressor 2 ; metabolism ; Selective Estrogen Receptor Modulators ; pharmacology ; Tamoxifen ; pharmacology

BACKGROUNDEstrogen receptor alpha (ER alpha) is the most important endocrine therapy responsiveness predictor for women with breast cancer. The accuracy of the prediction of the response to endocrine therapy was thought to be affected by involving the estrogen receptor coregulatory proteins and cross-talk between ER and other growth factor-signaling networks. Nuclear corepressor 1 (NCOR1) is one of the ER a transcription repressor. The objective of the study is to investigate the expression of NCOR1 at the protein level and pursue its predictive value for breast cancer endocrine therapy.

METHODSIn the present study, the level of expression of NCOR1 protein has been assessed by immunohistochemistry in 104 cases of invasive carcinoma of the breast. Associations between NCOR1 protein expression and different clinicopathological factors and survival were sought.

RESULTSIt was found that NCOR1 was expressed at significantly higher levels in responsive patients treated with endocrine therapy as first-line treatment on relapse. Responsive patients also had a significantly longer post-relapse survival and overall survival. No NCOR1 expression difference was found between patient by age, tumor size, lymph node status, different histological grade groups and human epidermal growth factor receptor 2 (HER2) status. Multivariate analysis showed that NCOR1 is an independent prognostic factor for over-all survival.

CONCLUSIONSIn breast cancer, NCOR1 protein expression level predicts response to endocrine therapy as first-line treatment for breast cancer patients on relapse and NCOR1 protein level assay may increase the accuracy in the endocrine treatment determination and, therefore, improving the patients survival.

Antineoplastic Agents, Hormonal ; therapeutic use ; Breast Neoplasms ; drug therapy ; metabolism ; Estrogen Receptor alpha ; metabolism ; Female ; Gene Expression Regulation ; Humans ; Immunohistochemistry ; Middle Aged ; Nuclear Receptor Co-Repressor 1 ; metabolism ; Receptor, ErbB-2 ; metabolism ; Receptors, Progesterone ; metabolism ; Tamoxifen ; therapeutic use

BACKGROUNDNF-kappaB p65 was shown to inhibit transcription of phosphoenolpyruvate carboxykinase (PEPCK), a rate-limiting enzyme in gluconeogenesis in the liver. To understand the mechanism of action of NF-kappaB p65, we investigated the nuclear receptor corepressor in the regulation of PEPCK transcription.

METHODSRat H4IIE cells, human hepatoma HepG2 cells and human embryo kidney (HEK) 293 cells were used in this study. The transcriptional activity of a rat PEPCK gene promoter (-490/+100) was analyzed in HepG2 cells, a HepG2 super suppressor IkBalpha (ssIkBalpha) stable cell line, and HEK 293 cells. The effects of p65 and ssIkBalpha on a rat PEPCK gene promoter were observed using the PEPCK luciferase reporter system. The interaction of the cAMP-response- element-binding (CREB) protein, histone deacetylase 3 (HDAC3) and silencing mediator for retinoic and thyroid hormone receptors (SMRT) with the PEPCK gene promoter were investigated using the chromatin immunoprecipitation (ChIP) assay. p65 cotransfection and RNAi-mediated gene knockdown were used to determine the corepressor involved in the inhibition of PEPCK by NF-kappaB p65 and the transcriptional regulation of CREB by NF-kappaB p65.

RESULTSNF-kappaB p65 inhibited PEPCK expression and the inhibition was blocked by ssIkBalpha. The inhibitory effect of p65 was completely blocked in a HepG2 stable cell line in which ssIkBalpha was expressed. HDAC3 or SMRT knockdown led to a significant up-regulation of PEPCK reporter activity in the presence of p65 cotransfection. In the ChIP assay the interaction of HDAC3 and SMRT with the PEPCK gene promoter was induced by p65 activation, but the CREB signal was reduced. Transcriptional activity of CREB was inhibited by NF-kappaB p65 cotransfection. The inhibitory effect of NF-kappaB p65 was blocked by HDAC3 RNAi or SMRT RNAi.

CONCLUSIONSThe study showed that the inhibition of PEPCK by NF-kappaB p65 was dependent on HDAC3 and SMRT, which form a nuclear corepressor complex for transcriptional inhibition. The transcription factors NF-kappaB p65 and CREB share the same corepressor HDAC3-SMRT, and the corepressor exchange leads to inhibition of PEPCK gene transcription by NF-kappaB p65.

Animals ; Blotting, Western ; Cell Line ; Chromatin Immunoprecipitation ; Cyclic AMP Response Element-Binding Protein ; genetics ; metabolism ; Hep G2 Cells ; Histone Deacetylases ; genetics ; metabolism ; Humans ; NF-kappa B ; genetics ; metabolism ; Nuclear Receptor Co-Repressor 2 ; genetics ; metabolism ; Phosphoenolpyruvate Carboxykinase (ATP) ; genetics ; Promoter Regions, Genetic ; genetics ; Protein Binding ; genetics ; physiology ; Rats ; Reverse Transcriptase Polymerase Chain Reaction ; Transcription Factor RelA ; genetics ; metabolism