Abstract 740: Investigating the role of epigenetic mechanisms upon aberrant signaling network activation.

Abstract Growth factor (GF) stimulation of quiescent cells activates critical receptor tyrosine kinase (RTK) signaling pathways as well as waves of downstream gene expression to drive cell proliferation, survival, and migration. Aberrant activation of RTK signaling networks is a root cause of the uncontrolled cell growth and cell survival seen in cancer. In this study, we aim to uncover the role of epigenetic mechanisms in controlling the dynamic gene expression changes that occur as a cell is activated from a quiescent state, in normal and oncogenic cellular contexts. In order to compare controlled RTK signaling with hyperactive RTK signaling cellular states, we created a cell culture system to modulate the duration and intensity of RTK activation. We genetically deleted the Sprouty (Spry) genes, a family of negative feedback inhibitors of RTK signaling that function as putative tumor suppressors. The Spry deficient cells are hypersensitive to several GFs and show significantly enhanced and prolonged activation of several critical RTK signaling pathways, including the Ras-MAPK pathway. Additionally, the Spry deficient cells possess accelerated cell growth and increased tumorigenic potential compared to their wild-type counterparts. To determine whether this deregulated signaling results in aberrant gene expression, quiescent Spry wild-type and deficient cells were stimulated with GFs, and microarrays were used to profile changes in gene expression over time. Deregulated RTK signaling due to the absence of Spry leads to abnormal expression of a large subset of genes. Specifically, many genes display display not only changes in the level of expression, but aberrant patterns of response to GF stimulation. We determined that genes with deregulated activation in Spry deficient cells display significant differences in histone tail modifications at promoter regions and distal regulatory elements. Interestingly, these changes are evident in the quiescent cellular state as well as upon GF-mediated RTK network activation. Our work suggests that dynamic changes in a cell's epigenetic landscape contribute to the deregulated activation of genes upon hyperactive RTK signaling. Our study will provide a comprehensive view of how epigenetic mechanisms contribute to aberrant gene expression in oncogenic cellular contexts. Citation Format: Behnam Nabet, Rosemary Braun, Relja Popovic, Jonathan D. Licht. Investigating the role of epigenetic mechanisms upon aberrant signaling network activation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 740. doi:10.1158/1538-7445.AM2013-740