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A feedback loop between androgen receptor and ERK signaling in estrogen receptor-negative breast cancer.

ABSTRACT: Estrogen receptor (ER)-negative breast cancer is heterogeneous, and the biology of this disease has remained poorly understood. Molecular apocrine is a subtype of ER-negative breast cancer that is characterized by the overexpression of steroid-response genes such as AR and a high rate of ErbB2 amplification. In this study, we have identified a positive feedback loop between the AR and extracellular signal-regulated kinase (ERK) signaling pathways in molecular apocrine breast cancer. In this process, AR regulates ERK phosphorylation and kinase activity. In addition, AR inhibition results in the down-regulation of ERK target proteins phospho-RSK1, phospho-Elk-1, and c-Fos using an in vivo molecular apocrine model. Furthermore, we show that AR-mediated induction of ERK requires ErbB2, and AR activity, in turn, regulates ErbB2 expression as an AR target gene. These findings suggest that ErbB2 is an upstream connector between the AR and ERK signaling pathways. Another feature of this feedback loop is an ERK-mediated regulation of AR. In this respect, the inhibition of ERK phosphorylation reduces AR expression and CREB1-mediated transcriptional regulation of AR acts as a downstream connector between the AR and ERK signaling pathways in molecular apocrine cells. Finally, we demonstrate that AR-positive staining is associated with the overexpression of ERK signaling targets phospho-Elk-1 and c-Fos in ER-negative breast tumors, which further supports a cross-regulation between the AR and ERK signaling pathways in molecular apocrine subtype. This study demonstrates an AR-ERK feedback loop in ER-negative breast cancer with significant biologic and therapeutic implications in this disease.

SUBMITTER: Chia KM

PROVIDER: S-EPMC3033594 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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A feedback loop between androgen receptor and ERK signaling in estrogen receptor-negative breast cancer.

Chia Kee Ming KM Liu Ji J Francis Glenn D GD Naderi Ali A

Neoplasia (New York, N.Y.) 20110201 2

Estrogen receptor (ER)-negative breast cancer is heterogeneous, and the biology of this disease has remained poorly understood. Molecular apocrine is a subtype of ER-negative breast cancer that is characterized by the overexpression of steroid-response genes such as AR and a high rate of ErbB2 amplification. In this study, we have identified a positive feedback loop between the AR and extracellular signal-regulated kinase (ERK) signaling pathways in molecular apocrine breast cancer. In this proc ...[more]

PMID: 21403841

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Project description:Triple-negative breast cancer (TNBC) is an aggressive subtype with few treatment options for chemo-resistant disease. In both preclinical models and patient circulating tumor cells, androgen receptor (AR) expression is increased in anchorage independent TNBC. The AR inhibitor enzalutamide (Enza) leads to reduced TNBC growth in soft agar, invasion, mammosphere formation in vitro, and reduced tumorigenicity and recurrence when combined with chemotherapy in vivo pre-clinical models. Transforming growth factor β (TGFβ) pathway gene signatures are also increased during TNBC anchorage independent survival both in vitro and in vivo in pre-clinical models and CTC from patients during relapse while on chemotherapy. We hypothesized that a positive loop between AR and TGFβ signaling facilitates TNBC anchorage independent survival (anoikis resistance). We previously published that AR protein levels and transcriptional activity increased during anchorage independent conditions and we now find that that multiple components of the TGFβ pathway, including TGFβ1 and 3, as well as pathway activity, as measured by nuclear localization and transcriptional activity of pSmad3, are enhanced in anchorage independent conditions. Indeed, exogenous TGFβ increased AR protein and TGFβ inhibition decreased AR and TNBC viability, particularly under anchorage independent culture conditions. ChIP-Seq experiments revealed AR binding to genomic regions near the TGFB1 and SMAD3. TGFB3 and AR expression were positively correlated in clinical datasets and high levels of co-expression correspond to significantly worse recurrence-free and overall survival in both ER- and basal-like breast cancer. Finally, combining Enza with a TGFβ inhibitor decreased cell survival more than either drug alone, particularly under anchorage independent conditions, where the effect was more than additive. These findings warrant further investigations into whether combined inhibition of AR and TGFβ pathways might decrease metastatic recurrence rates and mortality from TNBC.

Dataset Information

A feedback loop between androgen receptor and ERK signaling in estrogen receptor-negative breast cancer.

Publications

A feedback loop between androgen receptor and ERK signaling in estrogen receptor-negative breast cancer.

Similar Datasets

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