Estrogen-Related Receptor α1 Transcriptional Activities Are Regulated in Part via the ErbB2/HER2 Signaling Pathway

Abstract

We previously showed that (a) estrogen-related receptor A1 (ERRA1) down-modulates estrogen receptor (ER) -stimulated transcription in low ErbB2 -expressing MCF-7 mammary carcinoma cells, and (b) ERRA and ErbB2 mRNA levels positively correlate in clinical breast tumors. We show here that ERRA1 represses ERA-mediated activation in MCF-7 cells because it failed to recruit the coactivator glucocorticoid receptor interacting protein 1 (GRIP1) when bound to an estrogen response element. In contrast, ERRA1 activated estrogen response element -and ERR response element -mediated transcription in ERA-positive, high ErbB2 -expressing BT-474 mammary carcinoma cells, activation that was enhanced by overexpression of GRIP1. Likewise, regulation of the endogenous genes pS2, progesterone receptor, and ErbB2 by ERRA1 reflected the cell type -specific differences observed with our reporter plasmids. Importantly, overexpression of activated ErbB2 in MCF-7 cells led to transcriptional activation, rather than repression, by ERRA1. Two-dimensional PAGE of radiophosphate-labeled ERRA1 indicated that it was hyperphosphorylated in BT-474 relative to MCF-7 cells; incubation of these cells with anti-ErbB2 antibody led to reduction in the extent of ERRA1 phosphorylation. Additionally, mitogen-activated protein kinases (MAPK) and Akts, components of the ErbB2 pathway, phosphorylated ERRA1 in vitro. ERRA1-activated transcription in BT-474 cells was inhibited by disruption of ErbB2/epidermal growth factor receptor signaling with trastuzumab or gefitinib or inactivation of downstream components of this signaling, MAPK kinase/MAPK, and phosphatidylinositol-3-OH kinase/ Akt, with U0126 or LY294002, respectively. Thus, ERRA1 activities are regulated, in part, via ErbB2 signaling, with ERRA1 likely positively feedback-regulating ErbB2 expression. Taken together, we conclude that ERRA1 phosphorylation status shows potential as a biomarker of clinical course and antihormonal-and ErbB2-based treatment options, with ERRA1 serving as a novel target for drug development. (Mol Cancer Res 2007;5(1):71 -85)

Estrogen Induces Estrogen-related Receptor α Gene Expression and Chromatin Structural Changes in Estrogen Receptor (ER)-positive and ER-negative Breast Cancer Cells

“…We have demonstrated that E 2 induction of ERR␣ relies on the MAPK signaling pathway as it is susceptible to a MAPK inhibitor. Stimulation of the MAPK pathway by estrogen can lead to the activation of ERR␣ via phosphorylation (22,78). Phosphorylated ERR␣ binds DNA and interacts with co-activators more efficiently.…”

Exemestane's 17-hydroxylated metabolite exerts biological effects as an androgen

“…MCF-7/WS8 and T47D:A18 human mammary carcinoma cells, clonally selected from their parental counterparts for sensitivity to growth stimulation by E 2 (32), were used in all experiments indicating MCF-7 and T47D cells. Cells were maintained in steroid-replete RPMI 1640, but 3 days before all experiments, were cultured in steroid-free media as previously described (32,33).…”

“…33) or ARE(5x)-regulated (pAR-Luc; Panomics) firefly luciferase expression plasmid and co-transfected with a basal TATA promoter-regulated (pTA-srLuc) Renilla luciferase expression plasmid as previously described (33).…”

Raloxifene-stimulated experimental breast cancer with the paradoxical actions of estrogen to promote or prevent tumor growth: A unifying concept in anti-hormone resistance

“…Total RNA (1 μg) was reversely transcribed with the High Capacity cDNA reverse transcriptase kit (Applied Biosystems) following manufacturer's instructions. The sequences of the primers utilized for real-time qPCR are as follows: tff1 forward primer, 5'-CATC GACGTCCCTCCAGAAGAG-3'; tff1 reverse primer, 5'-CTC TGGGACTAATCACCGTGCTG-3'; 36B4 forward primer, 5'-GTGTTCGACAATGGCAGGCAT-3'; 36B4 reverse primer, 5'-GACACCCTCCAGGAAGCGA-3'; c-myc forward primer, 5'-GCCACGTCTCCACACATCAG-3'; c-myc reverse primer, 5'-TCTTGGCAGCAGGAATAGTCCTT-3'; ebag9 forward primer, 5'-CTGGCAGAGGACGGAAATTA-3'; ebag9 reverse primer, 5'-TCATCCCAGGAAGTCCACTC-3'; the primer sets for egfr and her2 were previously described (36,37). Real-time qPCR was performed using the 7900HT real-time PCR system (Applied Biosystems), the amplicons were detected with SYBR-Green and analysis was performed utilizing the 2 -ΔΔt method (38).…”