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In vitro and in vivo analysis of B-Myb in basal-like breast cancer.

Thorner AR, Hoadley KA, Parker JS, Winkel S, Millikan RC, Perou CM - Oncogene (2008)

Bottom Line: In immortalized, human mammary epithelial cell lines, but not in basal-like tumor lines, cells ectopically expressing wild-type B-Myb or the S427G variant showed increased sensitivity to two DNA topoisomerase IIalpha inhibitors, but not to other chemotherapeutics.In addition, microarray analyses identified many G2/M genes as being induced in B-Myb overexpressing cells.These results confirm that B-Myb is involved in cell cycle control, and that its dysregulation may contribute to increased sensitivity to a specific class of chemotherapeutic agents.

View Article: PubMed Central - PubMed

Affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA.

ABSTRACT
A defining feature of basal-like breast cancer, a breast cancer subtype with poor clinical prognosis, is the high expression of 'proliferation signature' genes. We identified B-Myb, a MYB family transcription factor that is often amplified and overexpressed in many tumor types, as being highly expressed in the proliferation signature. However, the roles of B-Myb in disease progression, and its mammary-specific transcriptional targets, are poorly understood. Here, we showed that B-Myb expression is a significant predictor of survival and pathological complete response to neoadjuvant chemotherapy in breast cancer patients. We also identified a significant association between the G/G genotype of a nonsynonymous B-Myb germline variant (rs2070235, S427G) and an increased risk of basal-like breast cancer [OR 2.0, 95% CI (1.1-3.8)]. In immortalized, human mammary epithelial cell lines, but not in basal-like tumor lines, cells ectopically expressing wild-type B-Myb or the S427G variant showed increased sensitivity to two DNA topoisomerase IIalpha inhibitors, but not to other chemotherapeutics. In addition, microarray analyses identified many G2/M genes as being induced in B-Myb overexpressing cells. These results confirm that B-Myb is involved in cell cycle control, and that its dysregulation may contribute to increased sensitivity to a specific class of chemotherapeutic agents. These data provide insight into the influence of B-Myb in human breast cancer, which is of potential clinical importance for determining disease risk and for guiding treatment.

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Related in: MedlinePlus

Cell cycle profile of HME-CC cells stably expressing B-Myb and treated with doxorubicinCell cultures were treated with a range of doses of doxorubicin for 48 hours followed by propidium iodide DNA content analysis. Percentage of cells in (A) G1 phase and (B) G2/M were calculated by gating based on DNA content. Error bars indicate standard deviations between three independent experiments.
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Figure 5: Cell cycle profile of HME-CC cells stably expressing B-Myb and treated with doxorubicinCell cultures were treated with a range of doses of doxorubicin for 48 hours followed by propidium iodide DNA content analysis. Percentage of cells in (A) G1 phase and (B) G2/M were calculated by gating based on DNA content. Error bars indicate standard deviations between three independent experiments.

Mentions: Since B-Myb expressing, doxorubicin treated cells produced a significant G2/M-enriched gene list, we hypothesized that the cell cycle profiles of these cells may be different than treated controls. B-Myb expressing HME-CC and empty vector controls were both treated with a range of doxorubicin doses for 48 hours and their cell cycle profiles analyzed for DNA content using flow cytometry. At zero dose or high dose of doxorubicin, the cell cycle profiles for both B-Myb overexpressing cells and controls were identical in terms of the percentage of cells in G1 and G2/M phase (Figure 5). However, at low and intermediate concentrations (10-35 nM) of doxorubicin there was a significant difference in the number of cells in G1 or G2/M with a larger percentage of B-Myb overexpressing cells in G1 versus controls, and a lower percentage of B-Myb overexpressing cells in G2/M (Figure 5A and 5B, respectively); very similar results were obtained with etoposide treatment (Supplementary Figure 3). At high doses of doxorubicin or etoposide, regardless of B-Myb expression, the majority of cells arrested in G2/M.


In vitro and in vivo analysis of B-Myb in basal-like breast cancer.

Thorner AR, Hoadley KA, Parker JS, Winkel S, Millikan RC, Perou CM - Oncogene (2008)

Cell cycle profile of HME-CC cells stably expressing B-Myb and treated with doxorubicinCell cultures were treated with a range of doses of doxorubicin for 48 hours followed by propidium iodide DNA content analysis. Percentage of cells in (A) G1 phase and (B) G2/M were calculated by gating based on DNA content. Error bars indicate standard deviations between three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2636852&req=5

Figure 5: Cell cycle profile of HME-CC cells stably expressing B-Myb and treated with doxorubicinCell cultures were treated with a range of doses of doxorubicin for 48 hours followed by propidium iodide DNA content analysis. Percentage of cells in (A) G1 phase and (B) G2/M were calculated by gating based on DNA content. Error bars indicate standard deviations between three independent experiments.
Mentions: Since B-Myb expressing, doxorubicin treated cells produced a significant G2/M-enriched gene list, we hypothesized that the cell cycle profiles of these cells may be different than treated controls. B-Myb expressing HME-CC and empty vector controls were both treated with a range of doxorubicin doses for 48 hours and their cell cycle profiles analyzed for DNA content using flow cytometry. At zero dose or high dose of doxorubicin, the cell cycle profiles for both B-Myb overexpressing cells and controls were identical in terms of the percentage of cells in G1 and G2/M phase (Figure 5). However, at low and intermediate concentrations (10-35 nM) of doxorubicin there was a significant difference in the number of cells in G1 or G2/M with a larger percentage of B-Myb overexpressing cells in G1 versus controls, and a lower percentage of B-Myb overexpressing cells in G2/M (Figure 5A and 5B, respectively); very similar results were obtained with etoposide treatment (Supplementary Figure 3). At high doses of doxorubicin or etoposide, regardless of B-Myb expression, the majority of cells arrested in G2/M.

Bottom Line: In immortalized, human mammary epithelial cell lines, but not in basal-like tumor lines, cells ectopically expressing wild-type B-Myb or the S427G variant showed increased sensitivity to two DNA topoisomerase IIalpha inhibitors, but not to other chemotherapeutics.In addition, microarray analyses identified many G2/M genes as being induced in B-Myb overexpressing cells.These results confirm that B-Myb is involved in cell cycle control, and that its dysregulation may contribute to increased sensitivity to a specific class of chemotherapeutic agents.

View Article: PubMed Central - PubMed

Affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA.

ABSTRACT
A defining feature of basal-like breast cancer, a breast cancer subtype with poor clinical prognosis, is the high expression of 'proliferation signature' genes. We identified B-Myb, a MYB family transcription factor that is often amplified and overexpressed in many tumor types, as being highly expressed in the proliferation signature. However, the roles of B-Myb in disease progression, and its mammary-specific transcriptional targets, are poorly understood. Here, we showed that B-Myb expression is a significant predictor of survival and pathological complete response to neoadjuvant chemotherapy in breast cancer patients. We also identified a significant association between the G/G genotype of a nonsynonymous B-Myb germline variant (rs2070235, S427G) and an increased risk of basal-like breast cancer [OR 2.0, 95% CI (1.1-3.8)]. In immortalized, human mammary epithelial cell lines, but not in basal-like tumor lines, cells ectopically expressing wild-type B-Myb or the S427G variant showed increased sensitivity to two DNA topoisomerase IIalpha inhibitors, but not to other chemotherapeutics. In addition, microarray analyses identified many G2/M genes as being induced in B-Myb overexpressing cells. These results confirm that B-Myb is involved in cell cycle control, and that its dysregulation may contribute to increased sensitivity to a specific class of chemotherapeutic agents. These data provide insight into the influence of B-Myb in human breast cancer, which is of potential clinical importance for determining disease risk and for guiding treatment.

Show MeSH
Related in: MedlinePlus