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Loss of B-cell translocation gene 2 expression in estrogen receptor-positive breast cancer predicts tamoxifen resistance.

Takahashi M, Hayashida T, Okazaki H, Miyao K, Jinno H, Kitagawa Y - Cancer Sci. (2014)

Bottom Line: To determine if BTG2 expression modifies tamoxifen efficacy, a cohort of 60 patients treated with adjuvant tamoxifen monotherapy was analyzed.We found that increased BTG2 expression showed better clinical survival and was the only independent prognostic factor for disease-free survival (hazard ratio, 0.691; 95% confidence interval, 0.495-0.963; P = 0.029).These studies demonstrate that BTG2 is a significant factor in tamoxifen response, acting through modification of AKT activation in ER-positive/HER2-negative breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Keio University School of Medicine, Tokyo, Japan.

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In vitro and in vivo conditional expression model of B-cell translocation gene 2 (BTG2) using the tetracycline inducible system. (a) BTG2 was induced by treating MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells with tetracycline for 48 h and BTG2 mRNA expression was assessed using qPCR. Additionally, MCF7/tet-LacZ and MCF7-RASV12/tet-LacZ cells were analyzed as controls. (b) Several different concentrations of tamoxifen were added to MCF7-RASV12/tet-BTG2 cells to draw inhibition curves for cells with or without tetracycline treatment. (c) MCF7-RASV12/tet-BTG2 cells were injected into the mammary fat pad of immunodeficient mice to form tumors. These tumor-bearing mice were administered water containing tetracycline. To confirm the BTG2 expression, mRNA was extracted from the harvested tumors and the expression was analyzed using semi-quantitative RT-PCR. (d) The resected tumors were also immunostained with anti-V5 antibody to confirm the nuclear expression of BTG2 in the tumor cells. MCF7-RASV12/tet-LacZ cells were also injected to create tumors as negative controls.
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fig03: In vitro and in vivo conditional expression model of B-cell translocation gene 2 (BTG2) using the tetracycline inducible system. (a) BTG2 was induced by treating MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells with tetracycline for 48 h and BTG2 mRNA expression was assessed using qPCR. Additionally, MCF7/tet-LacZ and MCF7-RASV12/tet-LacZ cells were analyzed as controls. (b) Several different concentrations of tamoxifen were added to MCF7-RASV12/tet-BTG2 cells to draw inhibition curves for cells with or without tetracycline treatment. (c) MCF7-RASV12/tet-BTG2 cells were injected into the mammary fat pad of immunodeficient mice to form tumors. These tumor-bearing mice were administered water containing tetracycline. To confirm the BTG2 expression, mRNA was extracted from the harvested tumors and the expression was analyzed using semi-quantitative RT-PCR. (d) The resected tumors were also immunostained with anti-V5 antibody to confirm the nuclear expression of BTG2 in the tumor cells. MCF7-RASV12/tet-LacZ cells were also injected to create tumors as negative controls.

Mentions: To evaluate the relationship between BTG2 expression and tamoxifen efficacy in vivo, oncogenic H-RASV12 was introduced into the MCF7 cells. This was done because wild-type MCF7 could not constitute a xenograft tumor without additional estrogen management in an immunodeficient mouse; however, estrogen treatment during the experiment would strongly influence tamoxifen efficacy. MCF7-RASV12 maintains characteristics of hormone-sensitive breast cancer and forms tumors in immunodeficient mice without estrogen treatment.20,21 Oncogenic H-RASV12 transformation of MCF7 had no effect on the endogenous level of BTG2 expression (Fig.3a). To assess the cytotoxicity of tamoxifen treatment on BTG2 overexpression, a tetracycline-inducible BTG2 expression model was developed in the MCF7-RASV12 cells. The addition of low concentrations of tetracycline sharply induced BTG2 mRNA expression in both MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells (Fig.3a). As expected, MCF7-RASV12/tet-BTG2 tumors without BTG2 expression showed less sensitivity to tamoxifen treatment (IC50, 3.0 ± 0.24 μM) than tumors with induced BTG2 expression with statistical significance (IC50, 1.70 ± 0.16 μM; P = 0.043; Fig3b) .


Loss of B-cell translocation gene 2 expression in estrogen receptor-positive breast cancer predicts tamoxifen resistance.

Takahashi M, Hayashida T, Okazaki H, Miyao K, Jinno H, Kitagawa Y - Cancer Sci. (2014)

In vitro and in vivo conditional expression model of B-cell translocation gene 2 (BTG2) using the tetracycline inducible system. (a) BTG2 was induced by treating MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells with tetracycline for 48 h and BTG2 mRNA expression was assessed using qPCR. Additionally, MCF7/tet-LacZ and MCF7-RASV12/tet-LacZ cells were analyzed as controls. (b) Several different concentrations of tamoxifen were added to MCF7-RASV12/tet-BTG2 cells to draw inhibition curves for cells with or without tetracycline treatment. (c) MCF7-RASV12/tet-BTG2 cells were injected into the mammary fat pad of immunodeficient mice to form tumors. These tumor-bearing mice were administered water containing tetracycline. To confirm the BTG2 expression, mRNA was extracted from the harvested tumors and the expression was analyzed using semi-quantitative RT-PCR. (d) The resected tumors were also immunostained with anti-V5 antibody to confirm the nuclear expression of BTG2 in the tumor cells. MCF7-RASV12/tet-LacZ cells were also injected to create tumors as negative controls.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4317889&req=5

fig03: In vitro and in vivo conditional expression model of B-cell translocation gene 2 (BTG2) using the tetracycline inducible system. (a) BTG2 was induced by treating MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells with tetracycline for 48 h and BTG2 mRNA expression was assessed using qPCR. Additionally, MCF7/tet-LacZ and MCF7-RASV12/tet-LacZ cells were analyzed as controls. (b) Several different concentrations of tamoxifen were added to MCF7-RASV12/tet-BTG2 cells to draw inhibition curves for cells with or without tetracycline treatment. (c) MCF7-RASV12/tet-BTG2 cells were injected into the mammary fat pad of immunodeficient mice to form tumors. These tumor-bearing mice were administered water containing tetracycline. To confirm the BTG2 expression, mRNA was extracted from the harvested tumors and the expression was analyzed using semi-quantitative RT-PCR. (d) The resected tumors were also immunostained with anti-V5 antibody to confirm the nuclear expression of BTG2 in the tumor cells. MCF7-RASV12/tet-LacZ cells were also injected to create tumors as negative controls.
Mentions: To evaluate the relationship between BTG2 expression and tamoxifen efficacy in vivo, oncogenic H-RASV12 was introduced into the MCF7 cells. This was done because wild-type MCF7 could not constitute a xenograft tumor without additional estrogen management in an immunodeficient mouse; however, estrogen treatment during the experiment would strongly influence tamoxifen efficacy. MCF7-RASV12 maintains characteristics of hormone-sensitive breast cancer and forms tumors in immunodeficient mice without estrogen treatment.20,21 Oncogenic H-RASV12 transformation of MCF7 had no effect on the endogenous level of BTG2 expression (Fig.3a). To assess the cytotoxicity of tamoxifen treatment on BTG2 overexpression, a tetracycline-inducible BTG2 expression model was developed in the MCF7-RASV12 cells. The addition of low concentrations of tetracycline sharply induced BTG2 mRNA expression in both MCF7/tet-BTG2 and MCF7-RASV12/tet-BTG2 cells (Fig.3a). As expected, MCF7-RASV12/tet-BTG2 tumors without BTG2 expression showed less sensitivity to tamoxifen treatment (IC50, 3.0 ± 0.24 μM) than tumors with induced BTG2 expression with statistical significance (IC50, 1.70 ± 0.16 μM; P = 0.043; Fig3b) .

Bottom Line: To determine if BTG2 expression modifies tamoxifen efficacy, a cohort of 60 patients treated with adjuvant tamoxifen monotherapy was analyzed.We found that increased BTG2 expression showed better clinical survival and was the only independent prognostic factor for disease-free survival (hazard ratio, 0.691; 95% confidence interval, 0.495-0.963; P = 0.029).These studies demonstrate that BTG2 is a significant factor in tamoxifen response, acting through modification of AKT activation in ER-positive/HER2-negative breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Keio University School of Medicine, Tokyo, Japan.

Show MeSH
Related in: MedlinePlus