Open Access Research article

RhoB modifies estrogen responses in breast cancer cells by influencing expression of the estrogen receptor

Claire Médale-Giamarchi12, Isabelle Lajoie-Mazenc12, Emilie Malissein1, Elise Meunier1, Bettina Couderc23, Yann Bergé4, Thomas Filleron4, Laura Keller1, Claudine Marty4, Magali Lacroix-Triki4, Florence Dalenc1, Sophie F Doisneau-Sixou125* and Gilles Favre12*

Author Affiliations

1 INSERM U563 and UMR1037, Institut Claudius Regaud, 20-24 rue du pont St Pierre, Toulouse cedex 31052, France

2 Faculté des Sciences Pharmaceutiques, Université Paul Sabatier Toulouse III, Toulouse cedex 31062, France

3 EA4553, Institut Claudius Regaud, 20-24 rue du pont St Pierre, Toulouse cedex 31052, France

4 Département de Biologie et de Pathologie, Institut Claudius Regaud, 20-24 rue du pont St Pierre, Toulouse cedex 31052, France

5 Tumorbiologischen Labor, Klinikum der Ludwig-Maximilians-Universität, Maistraße 11, München 80337, Germany

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Breast Cancer Research 2013, 15:R6  doi:10.1186/bcr3377

Published: 22 January 2013

Abstract

Introduction

RhoB has been reported to exert positive and negative effects on cancer pathophysiology but an understanding of its role in breast cancer remains incomplete. Analysis of data from the Oncomine database showed a positive correlation between RhoB expression and positivity for both estrogen receptor alpha (ERα) and progesterone receptor (PR).

Methods

This finding was validated by our analysis of a tissue microarray constructed from a cohort of 113 patients and then investigated in human cell models.

Results

We found that RhoB expression in tissue was strongly correlated with ERα and PR expression and inversely correlated with tumor grade, tumor size and count of mitosis. In human breast cancer cell lines, RhoB attenuation was associated with reduced expression of both ERα and PR, whereas elevation of RhoB was found to be associated with ERα overexpression. Mechanistic investigations suggested that RhoB modulates ERα expression, controlling both its protein and mRNA levels, and that RhoB modulates PR expression by accentuating the recruitment of ERα and other major co-regulators to the promoter of PR gene. A major consequence of RhoB modulation was that RhoB differentially regulated the proliferation of breast cancer cell lines. Interestingly, we documented crosstalk between RhoB and ERα, with estrogen treatment leading to RhoB activation.

Conclusion

Taken together, our findings offer evidence that in human breast cancer RhoB acts as a positive function to promote expression of ERα and PR in a manner correlated with cell proliferation.