Abstract 391: Evolutionary trajectories and KRAS gene dosage define pancreatic cancer phenotypes
Authors: Mueller Sebastian , Engleitner Thomas , Maresch Roman , Zukowska Magdalena , Lange Sebastian , Kaltenbacher Thorsten , Konukiewitz Björn , Öllinger Rupert , Zwiebel Maximilian , Strong Alex , Yen Hsi-Yu , Banerjee Ruby , Louzada Sandra , Fu Beiyuan , Seidler Barbara , Götzfried Juliana , Schuck Kathleen , Hassan Zonera , Schönhuber Nina , Klein Sabine , Veltkamp Christian , Friedrich Mathias , Rad Lena , Barenboim Maxim , Ziegenhain Christoph , Hess Julia , Dovey Oliver M. , Eser Stefan , Parekh Swati , Constantino-Casas Fernando , Rosa Jorge de la , Sierra Marta I. , Fraga Mario , Mayerle Julia , Klöppel Günter , Schmid Roland M. , Cadiñanos Juan , Liu Pentao , Vassiliou George , Weichert Wilko , Steiger Katja , Enard Wolfgang , Yang Fengtang , Unger Kristian , Schneider Günter , Varela Ignacio , Bradley Allan , Saur Dieter , Rad Roland 
Published: August 2018

Abstract
Pancreatic ductal adenocarcinoma (PDAC) has frequent alterations in few genes (KRAS, CDKN2A/TP53/SMAD4) and extensive heterogeneity of cancer drivers beyond. The expectation that mutational landscapes of rare drivers could explain phenotypic diversity has -with few exceptions- not come true. Likewise, PDAC metastasis is not understood, and comparisons of primary/metastasis pairs did not find recurrently mutated “metastasis genes”. Here we show that key aspects of PDAC biology are defined by gene-dosage variation of PDAC signature genes, evolving along distinct evolutionary routes. We found increased gene dosage of the initiating KRAS mutation (KRASMUT-iGD) in human PDAC precursors. Mouse models revealed the importance of KrasMUT-iGD for both, early progression and metastasis, rationalizing the high frequency of PDAC dissemination at diagnosis. To overcome limitations posed to gene dosage studies by PDAC´s stroma-richness, we developed murine cell culture resources comprising 135 primaries/metastases. Integrative analyses of their genomes, transcriptomes and tumor phenotypes, combined with human studies and functional analyses revealed a series of additional KrasMUT-dosage effects: different KrasMUT-levels define distinct cellular morphologies, histopathologies and clinical outcomes, with highest KrasMUT-expression underlying the most aggressive undifferentiated phenotypes. We also observed KrasMUT-dosage-associated cellular plasticity, including epithelial-to-mesenchymal transition. Mechanistically, oncogenic dosage-variation is linked to distinct evolutionary routes, characterized by defined types/states of tumor-suppressor alterations: Phylogenetic tracking studies revealed convergent evolution of KrasMUT-iGD-gains, with dependence on prior homozygous Cdkn2a- or Trp53-loss. By contrast, in Cdkn2aHET cancers, amplifications of known and novel oncogenes (Myc, Yap1, Nfkb2) collaborate with KrasMUT-HET to drive progression, yet with lower metastatic potential. These results also reveal oncogene-selective/context-dependent Cdkn2a-haploinsufficiency, for which Tgfβ pathway alterations provide permissiveness. Our study uncovers universal principles underlying PDAC biology and phenotypic diversification. It describes evolutionary trajectories, identifies their genetic hallmarks and shows how oncogenic dosage-variation is differentially licensed along individual routes to control critical disease characteristics, including early progression, histopathology, metastasis, cellular plasticity and clinical aggressiveness.
Citation Format: Sebastian Mueller, Thomas Engleitner, Roman Maresch, Magdalena Zukowska, Sebastian Lange, Thorsten Kaltenbacher, Björn Konukiewitz, Rupert Öllinger, Maximilian Zwiebel, Alex Strong, Hsi-Yu Yen, Ruby Banerjee, Sandra Louzada, Beiyuan Fu, Barbara Seidler, Juliana Götzfried, Kathleen Schuck, Zonera Hassan, Nina Schönhuber, Sabine Klein, Christian Veltkamp, Mathias Friedrich, Lena Rad, Maxim Barenboim, Christoph Ziegenhain, Julia Hess, Oliver M. Dovey, Stefan Eser, Swati Parekh, Fernando Constantino-Casas, Jorge de la Rosa, Marta I. Sierra, Mario Fraga, Julia Mayerle, Günter Klöppel, Roland M. Schmid, Juan Cadiñanos, Pentao Liu, George Vassiliou, Wilko Weichert, Katja Steiger, Wolfgang Enard, Fengtang Yang, Kristian Unger, Günter Schneider, Ignacio Varela, Allan Bradley, Dieter Saur, Roland Rad. Evolutionary trajectories and KRAS gene dosage define pancreatic cancer phenotypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 391.