Abstract LB-306: The Ras exchange factor RasGRP1 opposes proliferative EGFR-SOS1 Ras signals and restricts intestinal epithelial cell growth

Abstract

Abstract The character of EGFR signals can influence cell fate. Anti-EGFR treatment has been successful as cancer therapy but not in colorectal cancer (CRC) where activating somatic KRAS mutations (KRASMUT) are prevalent. While relevant to CRC, intestinal EGFR signaling is poorly understood, particularly in the context of KRASMUT. Here we show that two distinct Ras nucleotide exchange factors, RasGRP1 and SOS1, lie downstream of the EGFR but act in functional opposition to one another in the context of KRASMUT. RasGRP1 creates a negative feedback loop that limits EGFR-SOS1-Ras signals and restricts CRC growth. Genetic Rasgrp1 depletion from KRasMUT mice exacerbates intestinal epithelial cell growth and dysplasia, leading to a highly serrated colonic epithelium. Furthermore, low RasGRP1 expression in CRC patient specimens correlates with poor clinical outcome. The unexpected inhibitory role of EGFR-RasGRP1 signals in KRASMUT gastrointestinal malignancies reveals an intricacy of EGFR signaling that should be considered for future molecular therapeutics. Citation Format: Philippe Depeille, Linda M. Henricks, Robert van de Ven, Ed Lemmens, Mary Matli, Kevin M. Haigis, David Donner, Robert Warren, Jeroen P. Roose. The Ras exchange factor RasGRP1 opposes proliferative EGFR-SOS1 Ras signals and restricts intestinal epithelial cell growth. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-306. doi:10.1158/1538-7445.AM2014-LB-306