title: A comprehensive survey of the mutagenic impact of common cancer cytotoxics.
abstract: BACKGROUND
  Genomic mutations caused by cytotoxic agents used in cancer chemotherapy may cause secondary malignancies as well as contribute to the evolution of treatment-resistant tumour cells. The stable diploid genome of the chicken DT40 lymphoblast cell line, an established DNA repair model system, is well suited to accurately assay genomic mutations.
  
  
  RESULTS
  We use whole genome sequencing of multiple DT40 clones to determine the mutagenic effect of eight common cytotoxics used for the treatment of millions of patients worldwide. We determine the spontaneous mutagenesis rate at 2.3 × 10(-10) per base per cell division and find that cisplatin, cyclophosphamide and etoposide induce extra base substitutions with distinct spectra. After four cycles of exposure, cisplatin induces 0.8 mutations per Mb, equivalent to the median mutational burden in common leukaemias. Cisplatin-induced mutations, including short insertions and deletions, are mainly located at sites of putative intrastrand crosslinks. We find two of the newly defined cisplatin-specific mutation types as causes of the reversion of BRCA2 mutations in emerging cisplatin-resistant tumours or cell clones. Gemcitabine, 5-fluorouracil, hydroxyurea, doxorubicin and paclitaxel have no measurable mutagenic effect. The cisplatin-induced mutation spectrum shows good correlation with cancer mutation signatures attributed to smoking and other sources of guanine-directed base damage.
  
  
  CONCLUSIONS
  This study provides support for the use of cell line mutagenesis assays to validate or predict the mutagenic effect of environmental and iatrogenic exposures. Our results suggest genetic reversion due to cisplatin-induced mutations as a distinct mechanism for developing resistance.
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary.
authors.forename: Bernadett
authors.initials: B
authors.lastname: Szikriszt
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary.
authors.forename: Ádám
authors.initials: Á
authors.lastname: Póti
authors.affiliation: Department of Physics of Complex Systems, Eötvös Loránd University, 1117, Budapest, Hungary.
authors.forename: Orsolya
authors.initials: O
authors.lastname: Pipek
authors.affiliation: Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, 2800, Lyngby, Denmark.
authors.forename: Marcin
authors.initials: M
authors.lastname: Krzystanek
authors.affiliation: CRUK Lung Cancer Centre of Excellence, UCL Cancer Institute, London, UK.
authors.forename: Nnennaya
authors.initials: N
authors.lastname: Kanu
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary.
authors.forename: János
authors.initials: J
authors.lastname: Molnár
authors.affiliation: Department of Physics of Complex Systems, Eötvös Loránd University, 1117, Budapest, Hungary.
authors.forename: Dezső
authors.initials: D
authors.lastname: Ribli
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szeltner
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary.
authors.forename: Gábor E
authors.initials: GE
authors.lastname: Tusnády
authors.affiliation: Department of Physics of Complex Systems, Eötvös Loránd University, 1117, Budapest, Hungary.
authors.forename: István
authors.initials: I
authors.lastname: Csabai
authors.affiliation: Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, 2800, Lyngby, Denmark. zoltan.szallasi@childrens.harvard.edu.|Computational Health Informatics Program (CHIP), Boston Children's Hospital, Boston, MA, USA. zoltan.szallasi@childrens.harvard.edu.|Harvard Medical School, Boston, MA, 02215, USA. zoltan.szallasi@childrens.harvard.edu.|MTA-SE-NAP, Brain Metastasis Research Group, 2nd Department of Pathology, Semmelweis University, 1091, Budapest, Hungary. zoltan.szallasi@childrens.harvard.edu.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Szallasi
authors.affiliation: CRUK Lung Cancer Centre of Excellence, UCL Cancer Institute, London, UK. charles.swanton@crick.ac.uk.|Francis Crick Institute, 44 Lincoln's Inn Fields, London, WCA2 3PX, UK. charles.swanton@crick.ac.uk.
authors.forename: Charles
authors.initials: C
authors.lastname: Swanton
authors.affiliation: Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117, Budapest, Hungary. szuts.david@ttk.mta.hu.
authors.forename: Dávid
authors.initials: D
authors.lastname: Szüts
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology / Q000633:toxicity*; D045744:Cell Line, Tumor; D002645:Chickens; D002945:Cisplatin / Q000009:adverse effects / Q000494:pharmacology / Q000633:toxicity*; D003603:Cytotoxins / Q000009:adverse effects / Q000494:pharmacology / Q000633:toxicity*; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D024522:Genes, BRCA2; D016678:Genome; D009153:Mutagens / Q000009:adverse effects / Q000494:pharmacology / Q000633:toxicity*; D059645:Mutation Rate
chemical_list: D000970:Antineoplastic Agents; D003603:Cytotoxins; D009153:Mutagens; D002945:Cisplatin
keywords: BRCA2; Cancer chemotherapy; Chemotherapy resistance; Cisplatin; Cyclophosphamide; Cytotoxics; DT40; Etoposide; Mutagenesis; Spontaneous mutagenesis; Whole genome sequencing