BACKGROUND: BRCA1-mutant breast tumors are typically estrogen receptor alpha (ER alpha) negative, whereas most sporadic tumors express wild-type BRCA1 and are ER alpha positive. We examined a possible mechanism for the observed ER alpha-negative phenotype of BRCA1-mutant tumors. METHODS: We used a breast cancer disease-specific microarray to identify transcripts that were differentially expressed between paraffin-embedded samples of 17 BRCA1-mutant and 14 sporadic breast tumors. We measured the mRNA levels of estrogen receptor 1 (ESR1) (the gene encoding ER alpha), which was differentially expressed in the tumor samples, by quantitative polymerase chain reaction. Regulation of ESR1 mRNA and ER alpha protein expression was assessed in human breast cancer HCC1937 cells that were stably reconstituted with wild-type BRCA1 expression construct and in human breast cancer T47D and MCF-7 cells transiently transfected with BRCA1-specific short-interfering RNA (siRNA). Chromatin immunoprecipitation assays were performed to determine if BRCA1 binds the ESR1 promoter and to identify other interacting proteins. Sensitivity to the antiestrogen drug fulvestrant was examined in T47D and MCF-7 cells transfected with BRCA1-specific siRNA. All statistical tests were two-sided. RESULTS: Mean ESR1 gene expression was 5.4-fold lower in BRCA1-mutant tumors than in sporadic tumors (95% confidence interval [CI] = 2.6-fold to 40.1-fold, P = .0019). The transcription factor Oct-1 recruited BRCA1 to the ESR1 promoter, and both BRCA1 and Oct-1 were required for ER alpha expression. BRCA1-depleted breast cancer cells expressing exogenous ER alpha were more sensitive to fulvestrant than BRCA1-depleted cells transfected with empty vector (T47D cells, the mean concentration of fulvestrant that inhibited the growth of 40% of the cells [IC40] for empty vector versus ER alpha: >10(-5) versus 8.0 x 10(-9) M [95% CI = 3.1 x 10(-10) to 3.2 x 10(-6) M]; MCF-7 cells, mean IC40 for empty vector versus ER alpha: >10(-5) versus 4.9 x 10(-8) M [95% CI = 2.0 x 10(-9) to 3.9 x 10(-6) M]). CONCLUSIONS: BRCA1 alters the response of breast cancer cells to antiestrogen therapy by directly modulating ER alpha expression.
BACKGROUND: BRCA1-mutant breast tumors are typically estrogen receptor alpha (ER alpha) negative, whereas most sporadic tumors express wild-type BRCA1 and are ER alpha positive. We examined a possible mechanism for the observed ER alpha-negative phenotype of BRCA1-mutant tumors. METHODS: We used a breast cancer disease-specific microarray to identify transcripts that were differentially expressed between paraffin-embedded samples of 17 BRCA1-mutant and 14 sporadic breast tumors. We measured the mRNA levels of estrogen receptor 1 (ESR1) (the gene encoding ER alpha), which was differentially expressed in the tumor samples, by quantitative polymerase chain reaction. Regulation of ESR1 mRNA and ER alpha protein expression was assessed in human breast cancer HCC1937 cells that were stably reconstituted with wild-type BRCA1 expression construct and in human breast cancer T47D and MCF-7 cells transiently transfected with BRCA1-specific short-interfering RNA (siRNA). Chromatin immunoprecipitation assays were performed to determine if BRCA1 binds the ESR1 promoter and to identify other interacting proteins. Sensitivity to the antiestrogen drug fulvestrant was examined in T47D and MCF-7 cells transfected with BRCA1-specific siRNA. All statistical tests were two-sided. RESULTS: Mean ESR1 gene expression was 5.4-fold lower in BRCA1-mutant tumors than in sporadic tumors (95% confidence interval [CI] = 2.6-fold to 40.1-fold, P = .0019). The transcription factor Oct-1 recruited BRCA1 to the ESR1 promoter, and both BRCA1 and Oct-1 were required for ER alpha expression. BRCA1-depleted breast cancer cells expressing exogenous ER alpha were more sensitive to fulvestrant than BRCA1-depleted cells transfected with empty vector (T47D cells, the mean concentration of fulvestrant that inhibited the growth of 40% of the cells [IC40] for empty vector versus ER alpha: >10(-5) versus 8.0 x 10(-9) M [95% CI = 3.1 x 10(-10) to 3.2 x 10(-6) M]; MCF-7 cells, mean IC40 for empty vector versus ER alpha: >10(-5) versus 4.9 x 10(-8) M [95% CI = 2.0 x 10(-9) to 3.9 x 10(-6) M]). CONCLUSIONS: BRCA1 alters the response of breast cancer cells to antiestrogen therapy by directly modulating ER alpha expression.
Authors: C M Perou; T Sørlie; M B Eisen; M van de Rijn; S S Jeffrey; C A Rees; J R Pollack; D T Ross; H Johnsen; L A Akslen; O Fluge; A Pergamenschikov; C Williams; S X Zhu; P E Lønning; A L Børresen-Dale; P O Brown; D Botstein Journal: Nature Date: 2000-08-17 Impact factor: 49.962
Authors: D A Bochar; L Wang; H Beniya; A Kinev; Y Xue; W S Lane; W Wang; F Kashanchi; R Shiekhattar Journal: Cell Date: 2000-07-21 Impact factor: 41.582
Authors: Sunil R Lakhani; Jorge S Reis-Filho; Laura Fulford; Frederique Penault-Llorca; Marc van der Vijver; Suzanne Parry; Timothy Bishop; Javier Benitez; Carmen Rivas; Yves-Jean Bignon; Jenny Chang-Claude; Ute Hamann; Cees J Cornelisse; Peter Devilee; Matthias W Beckmann; Carolin Nestle-Krämling; Peter A Daly; Neva Haites; Jenny Varley; Fiona Lalloo; Gareth Evans; Christine Maugard; Hanne Meijers-Heijboer; Jan G M Klijn; Edith Olah; Barry A Gusterson; Silvana Pilotti; Paolo Radice; Siegfried Scherneck; Hagay Sobol; Jocelyne Jacquemier; Teresa Wagner; Julian Peto; Michael R Stratton; Lesley McGuffog; Douglas F Easton Journal: Clin Cancer Res Date: 2005-07-15 Impact factor: 12.531
Authors: Richard D Kennedy; Julia J Gorski; Jennifer E Quinn; Gail E Stewart; Colin R James; Stephen Moore; Karl Mulligan; Ethan D Emberley; Tong F Lioe; Patrick J Morrison; Paul B Mullan; George Reid; Patrick G Johnston; Peter H Watson; D Paul Harkin Journal: Cancer Res Date: 2005-11-15 Impact factor: 12.701