Abstract 1118: FOXQ1 stimulates WNT-signaling through transcriptional activation of WNT5B to promote the epithelial to mesenchymal transition

Abstract

Abstract Aberrant induction of the epithelial to mesenchymal transition (EMT) is an acknowledged mechanism of acquired metastatic competence and drug resistance in many epithelial cancer types. Both physiological and pathological forms of EMT are thought to occur through a network of transcription factors (TFs) that drive cell plasticity and the acquisition of stem-like traits. The forkhead box transcription factor, FOXQ1, is a potent driver of EMT. FOXQ1 has been shown to be specifically upregulated in the triple negative subtype of breast cancer (TNBC) where is it associated with worse clinical prognosis. However, the role of FOXQ1 within the EMT transcriptional network has not been extensively characterized. In this study, we employed chromatin immunoprecipitation and RNA sequencing in a human mammary luminal epithelial cell line with ectopic FOXQ1 (HMLE/FOXQ1), as a model of breast EMT. We identified FOXQ1 localization within the promoter regions of prominent EMT-TFs, including TWIST1, ZEB1, FOXC2 and SIX2. Further, FOXQ1 direct gene targets are enriched in signaling pathways previously associated with EMT, including the WNT-signaling pathway. Within the WNT pathway, the WNT5B signaling ligand was a direct target for transcriptional activation by FOXQ1. Gene expression analysis in a panel of breast cancer cell lines revealed both FOXQ1 and WNT5B are enriched in the basal B subtype of TNBC. FOXQ1 and WNT5B expression were also found to be upregulated and correlated downstream of TGFβ induced EMT. Disruption of WNT5B expression attenuated EMT-associated stem-like traits, including decreases in mammosphere formation and in the CD44+/CD24- population, and significantly reduced cell invasion. Analysis of breast cancer gene expression from the TCGA revealed that FOXQ1 and WNT5B expression are correlated across all breast samples (r=0.46) and differentially upregulated in ER- breast cancer. Additionally, both FOXQ1 and WNT5B expression were associated with worse recurrence-free survival. Our data supports that WNT5B is a critical FOXQ1 target for mediating EMT features and suggests that disrupting the FOXQ1-WNT5B axis could be a potential strategy to target the EMT cell population in TNBC patients. Citation Format: Allison V. Mitchell, Guojun Wu. FOXQ1 stimulates WNT-signaling through transcriptional activation of WNT5B to promote the epithelial to mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1118.