Anti-estrogenic actions of histone deacetylase inhibitors in MCF-7 breast cancer cells

Abstract

Anti-estrogens are the current endocrine therapy of choice in the treatment of estrogen receptor (ER)-positive breast cancers. Histone deacetylase inhibitors (HDACi) also constitute a promising treatment for therapy, and combination of anti-estrogens with HDACi may improve efficacy while reducing side effects. We have examined the effect of the HDACi sodium butyrate and suberoylanilide hydroxamic acid (SAHA), alone and in combination with 17b-estradiol (E 2 ) and the pure anti-estrogen ICI 182.780 (ICI) in human MCF-7 breast cancer cells. HDACi caused a sustained increase of histone H3 acetylation and caused cell death as shown by flow cytometry analysis. In surviving cells, both inhibitors were even stronger than ICI in depleting cyclin D1 levels, inducing expression of the cyclin kinase inhibitor p21 Waf1/Cip1 , blocking phosphorylation of the retinoblastoma protein, or inhibiting cell growth. No additive effects of ICI with either butyrate or SAHA were found. In addition, these drugs were able to antagonize the effects of E 2 on expression of cell cycle proteins, cell growth, and transcription of ER-dependent genes. The anti-estrogenic effects of HDACi appear to be related to a strong downregulation of the expression of ERa that appears to be secondary to both transcriptional and post-transcriptional regulation. ERa phosphorylation is involved in estrogen signaling, and HDACi also prevented receptor phosphorylation in Ser-118 both in the absence and presence of ER ligands. These results provide further support for the use of deacetylase inhibitors as chemotherapeutic agents in the treatment of breast cancer tumors.

Dietary sources of lignans and isoflavones modulate responses to estradiol in estrogen reporter mice

“…An interesting feature of rye bran is the production of SCFAs, especially butyrate, in the gut [39,57]. Butyrate is a histone deacetylase inhibitor that inhibits E 2 -induced expression of estrogen target genes and proliferation of MCF-7 cells [58,59]. Perhaps butyrate production explains some of the estrogen antagonism in the rye-fed mice in our study.…”

Activation of the unliganded estrogen receptor by prolactin in breast cancer cells

“…However, it should be noted that this modification cannot be univocally linked to transcriptional activation, because ER antagonists also cause Ser-118-ERa phosphorylation (Lipfert et al, 2006). In fact, we have previously shown that ICI is at least as strong as E2 to induce a sustained increase of Ser-118-ERa phosphorylation in MCF-7 cells (De los Santos et al, 2007), and in this work we observe that ER antagonists cooperate with PRL to increase P-Ser-118-ERa levels. In addition to ERa phosphorylation, the activation of ERK1/2 and AKT by PRL may also lead to phosphorylation of receptor co-regulators (co-activators and co-repressors).…”

“…Cell culture and transfection T47D and MCF-7 cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% fetal calf serum, 2 mM glutamine, 100 IU/ml penicillin and 100 mg/ml streptomycin, and 72 h before transfection were shifted to serum-free medium lacking phenol red. Cells were transiently transfected with 5 mg of a luciferase reporter plasmid that contains three copies of a consensus ERE by incubation with a mixture of cationic liposomes (1.5 ml/mg DNA) for 6 h (De los Santos et al, 2007). Cells were then treated with 100 nM PRL, ICI or E2 for the indicated times, and luciferase activity was determined.…”

“…Cells were collected and stained with propidium iodide for sorting as previously described (De los Santos et al, 2007).…”

“…Interestingly, it has been proposed that phosphorylation in Ser-118 may be associated with an increase in estrogen agonism, progression of breast cancer, resistance to tamoxifen therapy and estrogen-independent growth of MCF-7 cells (Likhite et al, 2006;Murphy et al, 2006). Recently, it has been shown that the pure ER antagonist ICI 182,780 (ICI) can also induce ER phosphorylation in Ser-118 (Lipfert et al, 2006;De los Santos et al, 2007).…”