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

Médale-Giamarchi C, Lajoie-Mazenc I, Malissein E, Meunier E, Couderc B, Bergé Y, Filleron T, Keller L, Marty C, Lacroix-Triki M, Dalenc F, Doisneau-Sixou SF, Favre G - Breast Cancer Res. (2013)

Bottom Line: RhoB has been reported to exert positive and negative effects on cancer pathophysiology but an understanding of its role in breast cancer remains incomplete.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.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.

View Article: PubMed Central - HTML - PubMed

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.

Show MeSH

Related in: MedlinePlus

RhoB differentially affects the proliferation of breast cancer cell lines. Forty-eight hours after transfection or transduction, cells were seeded with estradiol (E2) or ethanol and counted daily. Error bars represent the mean values ± standard deviation from three independent experiments that generated triplicate data each. (A) MCF-7 cells were transfected with siControl (siC) or siB1. (B) MCF-7 cells, (C) SK-BR-3 cells and (D) MDA-MB-231 cells were transduced with adenoviral vectors (multiplicity of infection 100:1). Control western blot experiments are shown in the presence of E2. According to the Kruskal-Wallis test, differences were considered statistically significant at *P < 0.01 and **P < 0.001 by comparing siB1 or adenoviral vector expressing RhoB (AdB) conditions with the related control condition (either in the presence or absence of E2). The significance threshold was determined at 0.0125 using Bonferroni correction. AdC, adenoviral control empty vector.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3672819&req=5

Figure 5: RhoB differentially affects the proliferation of breast cancer cell lines. Forty-eight hours after transfection or transduction, cells were seeded with estradiol (E2) or ethanol and counted daily. Error bars represent the mean values ± standard deviation from three independent experiments that generated triplicate data each. (A) MCF-7 cells were transfected with siControl (siC) or siB1. (B) MCF-7 cells, (C) SK-BR-3 cells and (D) MDA-MB-231 cells were transduced with adenoviral vectors (multiplicity of infection 100:1). Control western blot experiments are shown in the presence of E2. According to the Kruskal-Wallis test, differences were considered statistically significant at *P < 0.01 and **P < 0.001 by comparing siB1 or adenoviral vector expressing RhoB (AdB) conditions with the related control condition (either in the presence or absence of E2). The significance threshold was determined at 0.0125 using Bonferroni correction. AdC, adenoviral control empty vector.

Mentions: The effect of RhoB on cell proliferation was evaluated in three cell lines exhibiting variable levels of expression of ERα, including MCF-7 (ERα/PR-positive), SK-BR-3 (ERα/PR-negative and p185erbB2 overexpressed) and MDA-MB-231 (ERα/PR-negative and p185erbB2-negative). As shown in Figure 5A, B, RhoB positively regulated the proliferation of MCF-7 cells both in the absence or presence of E2. siRNA-mediated inhibition of RhoB expression produced a 30 to 35% decrease in MCF-7 cell proliferation as soon as 1 day after transfection, with a 40 to 46% decrease by day 4 (Figure 5A). Conversely, a significant increase in cell proliferation was observed in MCF-7 cells transduced with an adenoviral vector expressing RhoB (Figure 5B), with an increase of 15 to 28% in relative cell proliferation at day 1 that reached 22 to 49% by day 4. In contrast to these observations, under similar conditions for infection of SK-BR-3 or MDA-MB-231 cells, the adenoviral RhoB vector either slightly decreased or had no significant biological effect on cell proliferation (Figure 5C, D). The effect of RhoB downregulation was also analyzed in LCC2 cells, an E2-independent, tamoxifen-resistant subline of the MCF-7 cells. As for the MCF-7 cells, a significant decrease of proliferation was observed at day 4, in parallel to ERα and RhoB downregulation (see Figures S2 and S3 in Additional files 4 and 5).


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

Médale-Giamarchi C, Lajoie-Mazenc I, Malissein E, Meunier E, Couderc B, Bergé Y, Filleron T, Keller L, Marty C, Lacroix-Triki M, Dalenc F, Doisneau-Sixou SF, Favre G - Breast Cancer Res. (2013)

RhoB differentially affects the proliferation of breast cancer cell lines. Forty-eight hours after transfection or transduction, cells were seeded with estradiol (E2) or ethanol and counted daily. Error bars represent the mean values ± standard deviation from three independent experiments that generated triplicate data each. (A) MCF-7 cells were transfected with siControl (siC) or siB1. (B) MCF-7 cells, (C) SK-BR-3 cells and (D) MDA-MB-231 cells were transduced with adenoviral vectors (multiplicity of infection 100:1). Control western blot experiments are shown in the presence of E2. According to the Kruskal-Wallis test, differences were considered statistically significant at *P < 0.01 and **P < 0.001 by comparing siB1 or adenoviral vector expressing RhoB (AdB) conditions with the related control condition (either in the presence or absence of E2). The significance threshold was determined at 0.0125 using Bonferroni correction. AdC, adenoviral control empty vector.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672819&req=5

Figure 5: RhoB differentially affects the proliferation of breast cancer cell lines. Forty-eight hours after transfection or transduction, cells were seeded with estradiol (E2) or ethanol and counted daily. Error bars represent the mean values ± standard deviation from three independent experiments that generated triplicate data each. (A) MCF-7 cells were transfected with siControl (siC) or siB1. (B) MCF-7 cells, (C) SK-BR-3 cells and (D) MDA-MB-231 cells were transduced with adenoviral vectors (multiplicity of infection 100:1). Control western blot experiments are shown in the presence of E2. According to the Kruskal-Wallis test, differences were considered statistically significant at *P < 0.01 and **P < 0.001 by comparing siB1 or adenoviral vector expressing RhoB (AdB) conditions with the related control condition (either in the presence or absence of E2). The significance threshold was determined at 0.0125 using Bonferroni correction. AdC, adenoviral control empty vector.
Mentions: The effect of RhoB on cell proliferation was evaluated in three cell lines exhibiting variable levels of expression of ERα, including MCF-7 (ERα/PR-positive), SK-BR-3 (ERα/PR-negative and p185erbB2 overexpressed) and MDA-MB-231 (ERα/PR-negative and p185erbB2-negative). As shown in Figure 5A, B, RhoB positively regulated the proliferation of MCF-7 cells both in the absence or presence of E2. siRNA-mediated inhibition of RhoB expression produced a 30 to 35% decrease in MCF-7 cell proliferation as soon as 1 day after transfection, with a 40 to 46% decrease by day 4 (Figure 5A). Conversely, a significant increase in cell proliferation was observed in MCF-7 cells transduced with an adenoviral vector expressing RhoB (Figure 5B), with an increase of 15 to 28% in relative cell proliferation at day 1 that reached 22 to 49% by day 4. In contrast to these observations, under similar conditions for infection of SK-BR-3 or MDA-MB-231 cells, the adenoviral RhoB vector either slightly decreased or had no significant biological effect on cell proliferation (Figure 5C, D). The effect of RhoB downregulation was also analyzed in LCC2 cells, an E2-independent, tamoxifen-resistant subline of the MCF-7 cells. As for the MCF-7 cells, a significant decrease of proliferation was observed at day 4, in parallel to ERα and RhoB downregulation (see Figures S2 and S3 in Additional files 4 and 5).

Bottom Line: RhoB has been reported to exert positive and negative effects on cancer pathophysiology but an understanding of its role in breast cancer remains incomplete.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.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.

View Article: PubMed Central - HTML - PubMed

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.

Show MeSH
Related in: MedlinePlus