An oncogenic KRAS transcription program activates the RHOGEF ARHGEF2 to mediate transformed phenotypes in pancreatic cancer

// Oliver A. Kent 1 , Maria-Jose Sandi 1 , Helen E. Burston 1 , Kevin R. Brown 2 , Robert Rottapel 1, 3, 4, 5, 6 1 Princess Margaret Cancer Centre, University Health Network, Toronto Medical Discovery Tower, University of Toronto, Toronto, Canada 2 Donnelly Centre and Banting and Best Department of Medical Research, University of Toronto, Toronto, Canada 3 Department of Medicine, St. Michael’s Hospital, Toronto, Canada 4 Department of Medical Biophysics, St. Michael’s Hospital, Toronto, Canada 5 Department of Immunology, St. Michael’s Hospital, Toronto, Canada 6 Division of Rheumatology, St. Michael’s Hospital, Toronto, Canada Correspondence to: Oliver A. Kent, email: kent.uhn@gmail.com Robert Rottapel, email: rottapel@gmail.com Keywords: KRAS, ARHGEF2, GEFH1, transcription, pancreatic Received: July 29, 2016     Accepted: October 13, 2016     Published: November 7, 2016 ABSTRACT Activating mutations of KRAS are nearly ubiquitous in pancreatic adenocarcinomas occurring in greater than 90% of cases. Cellular transformation by oncogenic RAS requires the RHO guanine exchange factor ARHGEF2 (also known as GEF-H1) for tumor growth and survival. Here, we find oncogenic KRAS activates ARHGEF2 through a minimal RAS responsive promoter. We have determined the endogenous ARHGEF2 promoter is positively regulated by the transcription factors ELK1, ETS1, SP1 and SP3 and negatively regulated by the RAS responsive element binding protein (RREB1). We find that the panel of ARHGEF2 -regulating transcription factors modulates RAS transformed phenotypes including cellular viability, anchorage-independent growth and invasion-migration of pancreatic cancer cells. RREB1 knockdown activates the amplitude and duration of RHOA via increased ARHGEF2 expression. By relieving the negative regulation of RREB1 on the ARHGEF2 promoter, we determined that ETS1 and SP3 are essential for the normal expression of ARHGEF2 and contribute to the migratory behavior of pancreatic cancer cells. Furthermore, enforced expression of ARHGEF2 rescues loss of SP3 driven invasion-migration and anchorage-independent growth defective phenotypes through restored activation of RHOA. Collectively, our results identify a transcription factor program required for RAS transformation and provide mechanistic insight into the highly metastatic behavior of pancreatic cancer.