Abstract 2676: Epithelial-mesenchymal transition does not require transcriptional repression of the epithelial program in vivo

Abstract

Abstract Epithelial-mesenchymal transition (EMT), the process by which an epithelial cell loses its adhesion to neighboring cells and acquires a motile, fibroblast-like phenotype, is critical for many aspects of embryogenesis and has been strongly implicated in tumor cell invasion and metastasis. EMT is thought to be primarily regulated at the transcriptional level through repression of epithelial genes by transcription factors such as Snail, Zeb and Twist. To date, the mechanisms driving EMT have been parsed out almost exclusively in vitro under pre-defined conditions (ie, using TGFβ as an EMT inducer), but it remains to be seen whether the machinery that regulates in vitro EMT is physiologically relevant. Using a lineage labeled mouse model of pancreatic ductal adenocarcinoma (PDAC), we isolated tumor cells that have spontaneously undergone EMT to interrogate the molecular mechanisms driving this process in vivo. By comparing the transcriptomes of epithelial (E-cadherin+) and mesenchymal (E-cadherin-) tumor cells, we found that for a majority of PDAC tumors, EMT does not require transcriptional repression of the epithelial program. These cells were fully capable of upregulating a mesenchymal program, as evidenced by the increased expression of collagens, SPARC, MMP2, PDPN, and PRRX1; however, despite the loss of E-cadherin protein, we detected no change in transcript levels of E-cadherin or other epithelial genes after EMT. Our results suggest that in vivo, cells that undergo EMT retain epithelial gene transcription, which may confer the ability to rapidly oscillate between epithelial and mesenchymal states. Citation Format: Nicole M. Aiello, David Balli, Robert Norgard, Jinyang Li, Amine Sahmoud, Ben Z. Stanger. Epithelial-mesenchymal transition does not require transcriptional repression of the epithelial program in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2676.