The Steroid Receptor Coactivator-1 Regulates Twist Expression and Promotes Breast Cancer Metastasis

¹Department of Molecular and Cellular Biology, Baylor College of Medicine; ²Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, Texas; ³UC Davis Cancer Center, University of California at Davis, Sacramento, California; and ⁴Luzhou Medical College, Luzhou, Sichuan, China

^* To whom correspondence should be addressed. E-mail: jxu{at}bcm.tmc.edu.

	Abstract

In breast cancer, steroid receptor coactivator-1 (SRC-1) expression positively correlates with HER2 expression and poor prognosis. In mouse mammary tumor virus–polyoma middle T (PyMT) breast cancer mouse model, SRC-1 strongly promotes mammary tumor metastasis. However, the molecular targets and mechanisms that mediate the role of SRC-1 in metastasis are unknown. In this study, SRC-1 wild-type (WT) and knockout (KO) cell lines were developed from the mammary tumors of WT/PyMT and KO/PyMT mice. WT cells exhibited strong migration and invasion capabilities, reduced E-cadherin and -catenin epithelial markers, gained N-cadherin and vimentin mesenchymal markers, and formed undifferentiated invasive structures in three-dimensional culture. In contrast, KO cells showed slow migration and invasion, retained E-cadherin, had less N-cadherin and vimentin, and developed partially differentiated three-dimensional structures. Importantly, WT cells expressed Twist, a master regulator of metastasis, at significantly higher levels versus KO cells. SRC-1 knockdown in WT cells reduced Twist expression, whereas SRC-1 restoration in KO cells also rescued Twist expression. Furthermore, SRC-1 was found to coactivate Twist transcription through physical interaction with the transcription factor PEA3 at the proximal Twist promoter. Accordingly, Twist knockdown in WT cells increased E-cadherin and reduced cell invasion and metastasis, and Twist expression in KO cells decreased E-cadherin and increased cell invasion. SRC-1 knockdown in human breast cancer cells also decreased Twist, cell migration, and invasion. Therefore, SRC-1 promotes breast cancer invasiveness and metastasis by coactivating PEA3-mediated Twist expression. Intervention of SRC-1 function may provide new strategies to inhibit breast cancer metastasis. [Cancer Res 2009;69(9):3819–27]

Key Words: nuclear receptor, SRC-1, coactivator, Twist, breast cancer