American Association for Cancer Research
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Figure S2. BET protein specificity and proliferation/survival from BRD4 Regulates Breast Cancer Dissemination through Jagged1/Notch1 Signaling

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posted on 2023-03-31, 00:29 authored by Guillaume Andrieu, Anna H. Tran, Katherine J. Strissel, Gerald V. Denis

(A-C) Relative mRNA expression levels of BRD2 (A), BRD3 (B), and BRD4 (C) in scrambled siRNA control or BRD2-, BRD3-, BRD4-depleted MDA-MB-231 cells. Bars show means (plus minus) SEM of three independent experiments. Statistical analyses were performed by using one-way ANOVA. (D) Dotplot of Annexin V/propidium iodide co-staining of MDA-MB-231 and SUM149PT cells treated with scramble, siBRD2, siBRD3 or BRD4 siRNA for 72h. Quadrant 1 (Q1): necrotic cells, Q2: late apoptotic cells, Q3: early apoptotic cells, Q4: viable cells. At least 20,000 cells were analyzed (n=3). (E) Cell cycle distribution of MDA-MB-231 and SUM149PT treated with scrambled siRNA control, siBRD2, siBRD3 or siBRD4 for 72h. At least 10,000 cells were analyzed (n=3). (F) MTT assay showing proliferation of MDA-MB-231, SUM149PT and MCF-7 treated with scramble, siBRD2, siBRD3 or BRD4 siRNA for 72h for the indicated times. Bars represent means (plus minus) SEM of three independent experiments. Statistical analysis was performed by using two-way ANOVA.

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ARTICLE ABSTRACT

The bromodomain and extraterminal (BET) proteins are epigenetic “readers” of acetylated histones in chromatin and have been identified as promising therapeutic targets in diverse cancers. However, it remains unclear how individual family members participate in cancer progression and small molecule inhibitors such as JQ1 can target functionally independent BET proteins. Here, we report a signaling pathway involving BRD4 and the ligand/receptor pair Jagged1/Notch1 that sustains triple-negative breast cancer migration and invasion. BRD4, but not BRD2 or BRD3, regulated Jagged1 expression and Notch1 signaling. BRD4-selective knockdown suppressed Notch1 activity and impeded breast cancer migration and invasion. BRD4 was required for IL6-stimulated, Notch1-induced migration and invasion, coupling microenvironment inflammation with cancer propagation. Moreover, in patients, BRD4 and Jagged1 expression positively correlated with the presence of distant metastases. These results identify a BRD4/Jagged1/Notch1 signaling pathway that is critical for dissemination of triple-negative breast cancer. Cancer Res; 76(22); 6555–67. ©2016 AACR.

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