Insights into the invasiveness of triple negative breast cancer from genome-wide profiling of transcription factor AP-1 (expression). Homo sapiens

Triple negative breast cancer (TNBC) is an aggressive clinical phenotype, and accounts for 15% to 20% of all breast cancers. The molecular determinants of malignant cell behaviors in TNBC remain largely unknown. We find that the AP-1 transcription factor component, Fra-1, is overexpressed in basal-like breast tumors, and its expression level has high prognostic significance. Depletion of Fra-1 or its heterodimeric partner c-Jun inhibits the proliferative and invasive phenotypes in TNBC cells. To gain insights into the transcriptional regulatory networks of AP-1 in TNBC cells, we combine genome-wide ChIP-seq with loss-of-function transcriptome analyses. We observe dysregulation of direct targets of the Fra-1/c-Jun heterodimer involved in cell proliferation, cell adhesion, and cell-cell contact. Intriguingly, we find that AP-1 mediates downregulation of E-cadherin through direct transcriptional induction of ZEB2. This work sheds light on the mechanisms and pathways by which TNBC acquires invasiveness and proliferative propensity. Overall design: BT549 cells grown in complete medium were transfected with a control siRNA, siRNA targeting Fra-1 or siRNA targeting c-Jun for 72 h, and then global gene expression profiles were assessed. Three or four biological replicates were used for each group.