Abstract IA29: Identifying epithelial morphogenesis inhibitors in neural crest development and cancer
Authors: Jimenez Laura , Whatcott Clifford , Wang Jindong , Warner Steven , Morrison Monique , Bearss David , Stewart Rodney A. 
Published: May 2016

Abstract
The epithelial to mesenchymal transition (EMT) is a highly conserved morphogenesis program that is essential for re-shaping and mobilizing epithelial cells during gastrulation, neural crest development and tissue regeneration. In cancer cells, EMT induction promotes acquisition of invasive cellular morphologies, stem cell-like properties and pro-survival mechanisms, which contribute to disease progression, therapy resistance and decreased overall survival. The identification of compounds that block or reverse EMT therefore represents an important therapeutic strategy to prevent cancer invasion and eradicate disseminated tumor cells. Unfortunately, current EMT inhibitors have shown limited clinical benefit, in part due to an incomplete understanding of the molecular mechanisms controlling EMT in development and cancer as well as a lack of screening platforms that recapitulate the complex physiological environment of EMT in the living animal. To overcome these obstacles, we have established a zebrafish Snail1-GFP lineage reporter strain to label dorsal neural tube progenitor cells before they undergo EMT to become neural crest, which allows us to visualize epithelial morphogenesis independent of later cell migration events. Thousands of Snail1-GFP embryos can be easily generated to perform whole animal-based screens with small molecule libraries to identify compounds that inhibit EMT in vivo. Our initial screening results using previously characterized EMT inhibitors showed that many compounds inhibited neural crest migration after EMT had occurred, but only one compound, an AXL receptor tyrosine kinase inhibitor called TP-0903, inhibited both epithelial morphogenesis and neural crest migration. TP-0903 significantly decreased twist1a expression, a canonical EMT transcription factor and blocked down-regulation of epithelial Cadherins. RNA-Seq analysis and chemical rescue experiments revealed that TP-0903 acts by inducing retinoic acid (RA) biosynthesis and triggering a RA-mediated transcriptional program. TP-0903 treatment of a number of human cell lines and mouse xenograph tumors showed that TP-0903 also inhibits EMT programs and survival in human cancer cells. These studies demonstrate the value and feasibility of using zebrafish neural crest development to identify effective EMT compounds in vivo. As such, we have identified TP-0903 as a new potential therapeutic for inhibiting EMT in cancer, and our findings support the hypothesis that RA-induced inhibition of EMT contributes to its current success in treating minimal residual disease in humans.
Citation Format: Laura Jimenez, Clifford Whatcott, Jindong Wang, Steven Warner, Monique Morrison, David Bearss, Rodney A. Stewart. Identifying epithelial morphogenesis inhibitors in neural crest development and cancer. [abstract]. In: Proceedings of the AACR Special Conference: Developmental Biology and Cancer; Nov 30-Dec 3, 2015; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(4_Suppl):Abstract nr IA29.