Phosphatidylinositol 3-kinase (PI3K) signaling controls survival and proliferation of cancer cells and is activated in around 60% of pancreatic ductal adenocarcinomas (PDACs). Although not entirely clarified, PI3K signaling is linked to cell cycle progression of PDAC cells. In this study we demonstrate that PI3K signaling controls transcription of the E2F1 gene and show that E2F1 is essential for S-phase progression of PDAC cells. On the molecular level, PI3K signaling controls c-myc protein abundance in a glycogen synthase kinase-3 (GSK3)-dependent fashion. c-myc binds to the E-box of the E2F1 gene in PDAC cells and this binding is under control of the PI3K-signaling pathway. Together, we demonstrate that PI3K–GSK3-dependent control of c-myc protein expression is connected to the transcription of the E2F1 gene in PDAC cells, leading to S-phase progression of the cell cycle. © 2009 Wiley-Liss, Inc.