ERRβ signalling through FST and BCAS2 inhibits cellular proliferation in breast cancer cells

Abstract

Background:The overexpression of oestrogen-related receptor-β (ERRβ) in breast cancer patients is correlated with improved prognosis and longer relapse-free survival, and the level of ERRβ mRNA is inversely correlated with the S-phase fraction of cells from breast cancer patients.Methods:Chromatin immunoprecipitation (ChIP) cloning of ERRβ transcriptional targets and gel supershift assays identified breast cancer amplified sequence 2 (BCAS2) and Follistatin (FST) as two important downstream genes that help to regulate tumourigenesis. Confocal microscopy, co-immunoprecipitation (CoIP), western blotting and quantitative real-time PCR confirmed the involvement of ERRβ in oestrogen signalling.Results:Overexpressed ERRβ induced FST-mediated apoptosis in breast cancer cells, and E-cadherin expression was also enhanced through upregulation of FST. However, this anti-proliferative signalling function was challenged by ERRβ-mediated BCAS2 upregulation, which inhibited FST transcription through the downregulation of β-catenin/TCF4 recruitment to the FST promoter. Interestingly, ERRβ-mediated upregulation of BCAS2 downregulated the major G1-S transition marker cyclin D1, despite the predictable oncogenic properties of BCAS2.Interpretation:Our study provides the first evidence that ERRβ, which is a coregulator of ERα also acts as a potential tumour-suppressor molecule in breast cancer. Our current report also provides novel insights into the entire cascade of ERRβ signalling events, which may lead to BCAS2-mediated blockage of the G1/S transition and inhibition of the epithelial to mesenchymal transition through FST-mediated regulation of E-cadherin. Importantly, matrix metalloprotease 7, which is a classical mediator of metastasis and E-cadherin cleavage, was also restricted as a result of ERRβ-mediated FST overexpression.

Estrogen-related Receptor β Reduces the Subnuclear Mobility of Estrogen Receptor α and Suppresses Estrogen-dependent Cellular Function

“…However, contrary to our expectation, the potential binding site was determined to be within the NTD by live-cell imaging and coIP using deletion mutants of ERR␤. In contrast, the interaction has been predicted to depend on the D-domain and LBD by computer modeling (61). The reason for the different findings may be the contrast between computer-assisted threedimensional modeling and live cell-imaging/coIP using deletion mutants of ERR␤.…”

“…ER␣ and ER␤ have been suggested to bind as a heterodimer in response to estrogen (37,57,66). ERR␤ can also form a heterodimer with ERR␣ that leads to transactivation of ERE and can interact with ER␤, with the resulting modulation of breast cancer-related genes (61,67). Given that the dimer interface of ERR␤ is located within its LBD, while ERR␤ interacts with ER␣ through the NTD, a more complicated complex (trimer or tetramer) of ERs and ERRs centered on ERR␤ may be possible, suggesting multiple signaling pathways of estrogen action.…”

“…Our findings support this idea, but a variety of mechanisms has been proposed in other reports. A recent report suggests that ERR␤ expression results in a better prognosis in breast cancer patients with reduced BCA2 and an increased FST level by controlling these genes (61). In addition, ERR␤ exerts a carcinostatic effect through activation of the p21 tumor suppressor gene and cell cycle regulation, which are not linked to anti-estrogenic action (69,70).…”

Increased Expression of Follistatin in Breast Cancer Reduces Invasiveness and Clinically Correlates with Better Survival

“…Activin has primarily been seen as an inhibitor of cellular proliferation, although certain cell populations seem to be stimulated by activin. Thus, the overall result of activin/FST action in cancer may be both context and cell type specific (3, 6).In the breast, FST is expressed in the normal mammary gland and in different breast proliferative diseases, with additional experimental evidence suggesting that FST can modulate the breast cancer cell cycle (3,(12)(13)(14). However, its role in breast cancer growth and metastasis is far from clear.…”

“…In the breast, FST is expressed in the normal mammary gland and in different breast proliferative diseases, with additional experimental evidence suggesting that FST can modulate the breast cancer cell cycle (3,(12)(13)(14). However, its role in breast cancer growth and metastasis is far from clear.…”