Abstract 4282: Crenolanib inhibition of PDGFRA+ fibroblast-like cells in visceral smooth muscle.

Abstract

Abstract Platelet derived growth factors (PDGFs) and their receptors (PDGFRs) play important roles in cell proliferation, survival, and migration . The PDGF/PDGFR signaling pathway plays a crucial role in embryonic development and for interstitial and mesenchymal cell proliferation . Primary cancer cells in the GI with abnormal expression of receptor tyrosine kinases like c-Kit and PDGFRs have been implicated in the formation of gastro-intestinal stromal tumors (GIST). Fibroblast-like cells (FLCs) exist in the smooth muscle of all visceral organs yet their functional role throughout the viscera is unclear . It has recently been demonstrated by studies within our group that these FLCs express PDGFRα . These studies demonstrated for the first time that PDGFRα+ cells are a novel class of excitable cells with the molecular and ionic apparatus to mediate enteric inhibitory responses to purines in GI muscles. Using Crenolanib, a novel potent inhibitor of PDGFRα, we have disrupted PDGFRα expression and signaling in normal BALB/c mice. Crenolanib is being developed to treat cancers with populations of primary cells over-expressing PDGFRα including GIST . To track the specific changes in GI visceral smooth muscle cell populations and changes in post-junctional neural responses, we examined changes in protein abundance, gene expression, and used intracellular microelectrodes to examine electrophysiological properties and responses to stimuli. Given the intimate anatomical relationship between Kit+ ICCs and PDGFRα+ FLCs, their structural similarities, and their defining expression of receptor tyrosine kinases, changes in the dynamics of both of these cell populations during Crenolanib inhibition was monitored within this model. Age and species matched pairs of mice injected with either vehicle or Crenolanib were collected from postpartum days 10 through 25 and analyzed for differences in gross anatomy and weight, electrophysiology, PDGFRα protein distribution by western blot and immunofluorescence, and gene expression by both end-point PCR and qPCR. These analyses show a distinct decrease in the protein abundance and gene expression of PDGFRα in Crenolanib injected mice; inhibitory neurological signaling is also affected, with a highly significant decrease in purinergic inhibitory responses to stimulation, which indicates this as one of the functional roles of FLCs in the Tunica muscularis. Monitoring FLCs and ICCs in this inhibition model has provided valuable information on the endogenous cellular dynamics that exist between ICCs and FLCs; it also sheds light on their relationship during pathophysiolgical disorders, including the development of GISTs . Citation Format: Evan Colletti, Abhijit Ramachandran, Monique Carter, Sean Ward. Crenolanib inhibition of PDGFRA+ fibroblast-like cells in visceral smooth muscle. [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 4282. doi:10.1158/1538-7445.AM2013-4282