Inducible knock-out of BCL6 in lymphoma cells results in tumor stasis
Stefanie Schlager, Carina Salomon, Sabine Olt, Christoph Albrecht, Anja Ebert, Oliver Bergner, Johannes Wachter, Francesca Trapani, Daniel Gerlach, Tilman Voss, Anna K. Traunbauer, Julian Jude, Matthias Hinterndorfer, Martina Minnich, Norbert Schweifer, Sophia M. Blake, Vittoria Zinzalla, Barbara Drobits, Darryl B. McConnell, Norbert Kraut, Mark Pearson, Johannes Zuber, Manfred Koegl
Abstract
// Stefanie Schlager 1 , Carina Salomon 1 , Sabine Olt 1 , Christoph Albrecht 1 , Anja Ebert 2 , Oliver Bergner 1 , Johannes Wachter 1 , Francesca Trapani 1 , Daniel Gerlach 1 , Tilman Voss 1 , Anna Traunbauer 2 , Julian Jude 2 , Matthias Hinterndorfer 2 , Martina Minnich 2 , Norbert Schweifer 1 , Sophia M. Blake 1 , 3 , Vittoria Zinzalla 1 , Barbara Drobits 1 , Darryl B. McConnell 1 , Norbert Kraut 1 , Mark Pearson 1 , Johannes Zuber 2 , 4 and Manfred Koegl 1 1 Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria 2 Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria 3 Current address: AstraZeneca AB, Gothenburg, Sweden 4 Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria Correspondence to: Manfred Koegl, email: [email protected] Keywords: BCL6; DLBCL; lymphoma; inducible CRISPR/Cas9; in vivo xenograft Received: May 24, 2019     Accepted: February 08, 2020     Published: March 03, 2020 ABSTRACT Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphomas worldwide and is characterized by a high diversity of genetic and molecular alterations. Chromosomal translocations and mutations leading to deregulated expression of the transcriptional repressor BCL6 occur in a significant fraction of DLBCL patients. An oncogenic role of BCL6 in the initiation of DLBCL has been shown as the constitutive expression of BCL6 in mice recapitulates the pathogenesis of human DLBCL. However, the role of BCL6 in tumor maintenance remains poorly investigated due to the absence of suitable genetic models and limitations of pharmacological inhibitors. Here, we have utilized tetracycline-inducible CRISPR/Cas9 mutagenesis to study the consequences of BCL6 deletion in established DLBCL models in culture and in vivo . We show that BCL6 knock-out in SU-DHL-4 cells in vitro results in an anti-proliferative response 4–7 days after Cas9 induction that was characterized by cell cycle (G1) arrest. Conditional BCL6 deletion in established DLBCL tumors in vivo induced a significant tumor growth inhibition with initial tumor stasis followed by slow tumor growth kinetics. Our findings support a role of BCL6 in the maintenance of lymphoma growth and showcase the utility of inducible CRISPR/Cas9 systems for probing oncogene addiction.