dUTPase inhibition augments replication defects of 5-Fluorouracil

// Anna Hagenkort 1, * , Cynthia B.J. Paulin 1, * , Matthieu Desroses 1, * , Antonio Sarno 2 , Elisee Wiita 1 , Oliver Mortusewicz 1 , Tobias Koolmeister 1 , Olga Loseva 1 , Ann-Sofie Jemth 1 , Ingrid Almlof 1 , Evert Homan 1 , Thomas Lundback 3 , Anna-Lena Gustavsson 3 , Martin Scobie 1 , Thomas Helleday 1 1 Division of Translational Medicine and Chemical Biology, Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden 2 Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway 3 Chemical Biology Consortium Sweden, Division of Translational Medicine and Chemical Biology, Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden * These authors have contributed equally to this work Correspondence to: Thomas Helleday, email: thomas.helleday@scilifelab.se Keywords: dUTPase, 5-Fluorouracil, DNA replication, combination therapy Received: July 07, 2016      Accepted: February 06, 2017      Published: February 28, 2017 ABSTRACT The antimetabolite 5-Fluorouracil (5-FU) is used in the treatment of various forms of cancer and has a complex mode of action. Despite 6 decades in clinical application the contribution of 5-FdUTP and dUTP [(5-F)dUTP] and 5-FUTP misincorporation into DNA and RNA respectively, for 5-FU-induced toxicity is still under debate. This study investigates DNA replication defects induced by 5-FU treatment and how (5-F)dUTP accumulation contributes to this effect. We reveal that 5-FU treatment leads to extensive problems in DNA replication fork progression, causing accumulation of cells in S-phase, DNA damage and ultimately cell death. Interestingly, these effects can be reinforced by either depletion or inhibition of the deoxyuridine triphosphatase (dUTPase, also known as DUT), highlighting the importance of (5-F)dUTP accumulation for cytotoxicity. With this study, we not only extend the current understanding of the mechanism of action of 5-FU, but also contribute to the characterization of dUTPase inhibitors. We demonstrate that pharmacological inhibition of dUTPase is a promising approach that may improve the efficacy of 5-FU treatment in the clinic.