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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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Association of B-cell translocation gene 2 (BTG2) expression and tamoxifen effect in breast cancer cell lines. (a) Quantitative PCR analysis (qPCR) of BTG2 expression in an immortalized mammary epithelial cell line, MCF10A, and breast cancer cell lines MDA-MB231, MDA-MB468, T47D, HCC1500 and MCF7. The fold-change in expression relative to GAPDH is shown. (b) Inhibition curve of MCF7, T47D, HCC1500 and MDA-MB231 (negative control) treated with several different concentrations of tamoxifen. The IC50 value was calculated as the concentration at which a 50% loss of viability occurred relative to the untreated cells. (c–e) A single MCF7 cell was plated onto 96-well plates for limiting dilution and 20 subclones were established. An in vitro cytotoxic assay and assessment of BTG2 expression using quantitative RT-PCR analysis were conducted. Each subclone expressed a different amount of BTG2 mRNA and different IC50 against tamoxifen. Relative expression levels of BTG2 on the x-axis and IC50 values on the y-axis were plotted for each subcloned cell in the correlation diagrams (Spearman correlation coefficient, R = −0.663; P = 0.001). (e) RNA from HCC1500 cells infected with shGFP and shBTG2 was analyzed using qPCR to determine the expression of BTG2. (f) The inhibition curve of HCC1500 infected with either shBTG2 or shGFP and treated with several different concentrations of tamoxifen.
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fig02: Association of B-cell translocation gene 2 (BTG2) expression and tamoxifen effect in breast cancer cell lines. (a) Quantitative PCR analysis (qPCR) of BTG2 expression in an immortalized mammary epithelial cell line, MCF10A, and breast cancer cell lines MDA-MB231, MDA-MB468, T47D, HCC1500 and MCF7. The fold-change in expression relative to GAPDH is shown. (b) Inhibition curve of MCF7, T47D, HCC1500 and MDA-MB231 (negative control) treated with several different concentrations of tamoxifen. The IC50 value was calculated as the concentration at which a 50% loss of viability occurred relative to the untreated cells. (c–e) A single MCF7 cell was plated onto 96-well plates for limiting dilution and 20 subclones were established. An in vitro cytotoxic assay and assessment of BTG2 expression using quantitative RT-PCR analysis were conducted. Each subclone expressed a different amount of BTG2 mRNA and different IC50 against tamoxifen. Relative expression levels of BTG2 on the x-axis and IC50 values on the y-axis were plotted for each subcloned cell in the correlation diagrams (Spearman correlation coefficient, R = −0.663; P = 0.001). (e) RNA from HCC1500 cells infected with shGFP and shBTG2 was analyzed using qPCR to determine the expression of BTG2. (f) The inhibition curve of HCC1500 infected with either shBTG2 or shGFP and treated with several different concentrations of tamoxifen.

Mentions: To determine the functional consequence of BTG2 expression in regulating tamoxifen sensitivity, a panel of human breast cancer cell lines was screened for endogenous BTG2 expression. MCF7, an ER-positive breast cancer cell line, showed decreased expression of BTG2 compared with MCF10A, which is an immortalized human mammary epithelial cell line whereas T47D and HCC1500 cell lines, both ER positive, showed increased expression (Fig.2a). Two ER-negative breast cancer cell lines, MDA-MB231 and MDA-MB468, demonstrated a 10-fold reduction in BTG2 expression compared with MCF10A (Fig.2a). An in vitro cytotoxicity assay showed that T47D and HCC1500 expressing the highest levels of endogenous BTG2 had more drug sensitivity than MCF7 (MCF7: IC50, 4.48 ± 0.21 μM; T47D: IC50, 1.31 ± 0.13 μM; HCC1500: IC50, 0.19 ± 0.15 μM). ER-negative MDA-MB468 was not responsive to tamoxifen (IC50 > 25 μM; Fig.2b).


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)

Association of B-cell translocation gene 2 (BTG2) expression and tamoxifen effect in breast cancer cell lines. (a) Quantitative PCR analysis (qPCR) of BTG2 expression in an immortalized mammary epithelial cell line, MCF10A, and breast cancer cell lines MDA-MB231, MDA-MB468, T47D, HCC1500 and MCF7. The fold-change in expression relative to GAPDH is shown. (b) Inhibition curve of MCF7, T47D, HCC1500 and MDA-MB231 (negative control) treated with several different concentrations of tamoxifen. The IC50 value was calculated as the concentration at which a 50% loss of viability occurred relative to the untreated cells. (c–e) A single MCF7 cell was plated onto 96-well plates for limiting dilution and 20 subclones were established. An in vitro cytotoxic assay and assessment of BTG2 expression using quantitative RT-PCR analysis were conducted. Each subclone expressed a different amount of BTG2 mRNA and different IC50 against tamoxifen. Relative expression levels of BTG2 on the x-axis and IC50 values on the y-axis were plotted for each subcloned cell in the correlation diagrams (Spearman correlation coefficient, R = −0.663; P = 0.001). (e) RNA from HCC1500 cells infected with shGFP and shBTG2 was analyzed using qPCR to determine the expression of BTG2. (f) The inhibition curve of HCC1500 infected with either shBTG2 or shGFP and treated with several different concentrations of tamoxifen.
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fig02: Association of B-cell translocation gene 2 (BTG2) expression and tamoxifen effect in breast cancer cell lines. (a) Quantitative PCR analysis (qPCR) of BTG2 expression in an immortalized mammary epithelial cell line, MCF10A, and breast cancer cell lines MDA-MB231, MDA-MB468, T47D, HCC1500 and MCF7. The fold-change in expression relative to GAPDH is shown. (b) Inhibition curve of MCF7, T47D, HCC1500 and MDA-MB231 (negative control) treated with several different concentrations of tamoxifen. The IC50 value was calculated as the concentration at which a 50% loss of viability occurred relative to the untreated cells. (c–e) A single MCF7 cell was plated onto 96-well plates for limiting dilution and 20 subclones were established. An in vitro cytotoxic assay and assessment of BTG2 expression using quantitative RT-PCR analysis were conducted. Each subclone expressed a different amount of BTG2 mRNA and different IC50 against tamoxifen. Relative expression levels of BTG2 on the x-axis and IC50 values on the y-axis were plotted for each subcloned cell in the correlation diagrams (Spearman correlation coefficient, R = −0.663; P = 0.001). (e) RNA from HCC1500 cells infected with shGFP and shBTG2 was analyzed using qPCR to determine the expression of BTG2. (f) The inhibition curve of HCC1500 infected with either shBTG2 or shGFP and treated with several different concentrations of tamoxifen.
Mentions: To determine the functional consequence of BTG2 expression in regulating tamoxifen sensitivity, a panel of human breast cancer cell lines was screened for endogenous BTG2 expression. MCF7, an ER-positive breast cancer cell line, showed decreased expression of BTG2 compared with MCF10A, which is an immortalized human mammary epithelial cell line whereas T47D and HCC1500 cell lines, both ER positive, showed increased expression (Fig.2a). Two ER-negative breast cancer cell lines, MDA-MB231 and MDA-MB468, demonstrated a 10-fold reduction in BTG2 expression compared with MCF10A (Fig.2a). An in vitro cytotoxicity assay showed that T47D and HCC1500 expressing the highest levels of endogenous BTG2 had more drug sensitivity than MCF7 (MCF7: IC50, 4.48 ± 0.21 μM; T47D: IC50, 1.31 ± 0.13 μM; HCC1500: IC50, 0.19 ± 0.15 μM). ER-negative MDA-MB468 was not responsive to tamoxifen (IC50 > 25 μM; Fig.2b).

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